Study on injectable chitosan hydrogel with tendon-derived stem cells for enhancing rotator cuff tendon-to-bone healing / 中国修复重建外科杂志

OBJECTIVE@#To explore the effect of chitosan (CS) hydrogel loaded with tendon-derived stem cells (TDSCs; hereinafter referred to as TDSCs/CS hydrogel) on tendon-to-bone healing after rotator cuff repair in rabbits.@*METHODS@#TDSCs were isolated from the rotator cuff tissue of 3 adult New Zealand white rabbits by Henderson step-by-step enzymatic digestion method and identified by multidirectional differentiation and flow cytometry. The 3rd generation TDSCs were encapsulated in CS to construct TDSCs/CS hydrogel. The cell counting kit 8 (CCK-8) assay was used to detect the proliferation of TDSCs in the hydrogel after 1-5 days of culture in vitro, and cell compatibility of TDSCs/CS hydrogel was evaluated by using TDSCs alone as control. Another 36 adult New Zealand white rabbits were randomly divided into 3 groups ( n=12): rotator cuff repair group (control group), rotator cuff repair+CS hydrogel injection group (CS group), and rotator cuff repair+TDSCs/CS hydrogel injection group (TDSCs/CS group). After establishing the rotator cuff repair models, the corresponding hydrogel was injected into the tendon-to-bone interface in the CS group and TDSCs/CS group, and no other treatment was performed in the control group. The general condition of the animals was observed after operation. At 4 and 8 weeks, real-time quantitative PCR (qPCR) was used to detect the relative expressions of tendon forming related genes (tenomodulin, scleraxis), chondrogenesis related genes (aggrecan, sex determining region Y-related high mobility group-box gene 9), and osteogenesis related genes (alkaline phosphatase, Runt-related transcription factor 2) at the tendon-to-bone interface. At 8 weeks, HE and Masson staining were used to observe the histological changes, and the biomechanical test was used to evaluate the ultimate load and the failure site of the repaired rotator cuff to evaluate the tendon-to-bone healing and biomechanical properties.@*RESULTS@#CCK-8 assay showed that the CS hydrogel could promote the proliferation of TDSCs ( P<0.05). qPCR results showed that the expressions of tendon-to-bone interface related genes were significantly higher in the TDSCs/CS group than in the CS group and control group at 4 and 8 weeks after operation ( P<0.05). Moreover, the expressions of tendon-to-bone interface related genes at 8 weeks after operation were significantly higher than those at 4 weeks after operation in the TDSCs/CS group ( P<0.05). Histological staining showed the clear cartilage tissue and dense and orderly collagen formation at the tendon-to-bone interface in the TDSCs/CS group. The results of semi-quantitative analysis showed that compared with the control group, the number of cells, the proportion of collagen fiber orientation, and the histological score in the TDSCs/CS group increased, the vascularity decreased, showing significant differences ( P<0.05); compared with the CS group, the proportion of collagen fiber orientation and the histological score in the TDSCs/CS group significantly increased ( P<0.05), while there was no significant difference in the number of cells and vascularity ( P>0.05). All samples in biomechanical testing failed at the repair site during the testing process. The ultimate load of the TDSCs/CS group was significantly higher than that of the control group ( P<0.05), but there was no significant difference compared to the CS group ( P>0.05).@*CONCLUSION@#TDSCs/CS hydrogel can induce cartilage regeneration to promote rotator cuff tendon-to-bone healing.

Preparation and properties of hydrogels loaded with phage endolysin Lys84 / 生物工程学报

This study investigated the application of poly(N-isopropylacrylamide)-based interpenetrating network temperature-sensitive hydrogels (notation: IPNT) as the delivery vehicle for phage endolysin Lys84 and the potential of drug-loaded hydrogels as antimicrobial materials. Interpenetrating network temperature-sensitive hydrogels were prepared by free radical polymerization of sodium alginate and N-isopropylacrylamide. Drug-loaded hydrogels (IPNT-Lys84) were obtained by dry soaking method with the endolysin Lys84 of Staphylococcus aureus phage. The physical properties of the hydrogels with and without drug loading were characterized by infrared spectroscopy, scanning electron microscopy, and differential scanning calorimetry. The swelling and deswelling of the hydrogels as well as the release of endolysin Lys84 were investigated. Moreover, the antibacterial properties of IPNT-Lys84 hydrogels at different temperatures and concentrations of the drug solution were studied. The results showed that IPNT-Lys84 hydrogel had uniform pores and a low critical solubility temperature (LCST) of 32 ℃. The equilibrium swelling of the hydrogel was 30 g/g, and the water loss rate was 88% upon deswelling. The release rate of endolysin reached more than 70% within 6 h at 37 ℃. The bactericidal rate of IPNT-Lys84 hydrogel was over 99.9%. The research results showed the feasibility of using IPNT to deliver the endolysin Lys84, and IPNT-Lys84 hydrogel might be an effective antimicrobial material against multi-drug resistant Staphylococcus aureus.

Application of hydrogel-loaded stem cell exosomes in the field of tissue regeneration / 生物工程学报

In recent years, mesenchymal stem cell (MSCs)-derived exosomes have attracted much attention in the field of tissue regeneration. Mesenchymal stem cell-derived exosomes are signaling molecules for communication among cells. They are characterized by natural targeting and low immunogenicity, and are mostly absorbed by cells through the paracrine pathway of mesenchymal stem cells. Moreover, they participate in the regulation and promotion of cell or tissue regeneration. As a scaffold material in regenerative medicine, hydrogel has good biocompatibility and degradability. Combining the two compounds can not only improve the retention time of exosomes at the lesion site, but also improve the dose of exosomes reaching the lesion site by in situ injection, and the therapeutic effect in the lesion area is significant and continuous. This paper summarizes the research results of the interaction of exocrine and hydrogel composite materials to promote tissue repair and regeneration, in order to facilitate research in the field of tissue regeneration in the future.

Applicatoin of chitosan-based hydrogel in oral tissue engineering / 中南大学学报(医学版)

Pulpitis, periodontitis, jaw bone defect, and temporomandibular joint damage are common oral and maxillofacial diseases in clinic, but traditional treatments are unable to restore the structure and function of the injured tissues. Due to their good biocompatibility, biodegradability, antioxidant effect, anti-inflammatory activity, and broad-spectrum antimicrobial property, chitosan-based hydrogels have shown broad applicable prospects in the field of oral tissue engineering. Quaternization, carboxymethylation, and sulfonation are common chemical modification strategies to improve the physicochemical properties and biological functions of chitosan-based hydrogels, while the construction of hydrogel composite systems via carrying porous microspheres or nanoparticles can achieve local sequential delivery of diverse drugs or bioactive factors, laying a solid foundation for the well-organized regeneration of defective tissues. Chemical cross-linking is commonly employed to fabricate irreversible permanent chitosan gels, and physical cross-linking enables the formation of reversible gel networks. Representing suitable scaffold biomaterials, several chitosan-based hydrogels transplanted with stem cells, growth factors or exosomes have been used in an attempt to regenerate oral soft and hard tissues. Currently, remarkable advances have been made in promoting the regeneration of pulp-dentin complex, cementum-periodontium-alveolar bone complex, jaw bone, and cartilage. However, the clinical translation of chitosan-based hydrogels still encounters multiple challenges. In future, more in vivo clinical exploration under the conditions of oral complex microenvironments should be performed, and the combined application of chitosan-based hydrogels and a variety of bioactive factors, biomaterials, and state-of-the-art biotechnologies can be pursued in order to realize multifaceted complete regeneration of oral tissue.

Effects of three-dimensional bioprinting antibacterial hydrogel on full-thickness skin defect wounds in rats / 中华烧伤杂志

Objective: To explore the effects of three-dimensional (3D) bioprinting gelatin methacrylamide (GelMA) hydrogel loaded with nano silver on full-thickness skin defect wounds in rats. Methods: The experimental research method was adopted. The morphology, particle diameter, and distribution of silver nanoparticles in nano silver solution with different mass concentrations and the pore structure of silver-containing GelMA hydrogel with different final mass fractions of GelMA were observed by scanning electron microscope and the pore size was calculated. On treatment day 1, 3, 7, and 14, the concentration of nano silver released from the hydrogel containing GelMA with final mass fraction of 15% and nano silver with final mass concentration of 10 mg/L was detected by mass spectrometer. At 24 h of culture, the diameters of inhibition zone of GelMA hydrogel containing final mass concentration of 0 (no nano silver), 25, 50, and 100 mg/L nano silver against Staphylococcus aureus and Escherichia coli were detected. Fibroblasts (Fbs) and adipose stem cells (ASCs) were isolated respectively by enzymatic digestion using the discarded prepuce after circumcision from a 5-year-old healthy boy who was treated in the Department of Urology of the Second Affiliated Hospital of Zhejiang University School of Medicine in July 2020, and the discarded fat tissue after liposuction from a 23-year-old healthy woman who was treated in the Department of Plastic Surgery of the Hospital in July 2020. The Fbs were divided into blank control group (culture medium only), 2 mg/L nano sliver group, 5 mg/L nano sliver group, 10 mg/L nano sliver group, 25 mg/L nano sliver group, and 50 mg/L nano sliver group, which were added with the corresponding final mass concentrations of nano sliver solution, respectively. At 48 h of culture, the Fb proliferation viability was detected by cell counting kit 8 method. The Fbs were divided into 0 mg/L silver-containing GelMA hydrogel group, 10 mg/L silver-containing GelMA hydrogel group, 50 mg/L silver-containing GelMA hydrogel group, and 100 mg/L silver-containing GelMA hydrogel group and then were correspondingly treated. On culture day 1, 3, and 7, the Fb proliferation viability was detected as before. The ASCs were mixed into GelMA hydrogel and divided into 3D bioprinting group and non-printing group. On culture day 1, 3, and 7, the ASC proliferation viability was detected as before and cell growth was observed by live/dead cell fluorescence staining. The sample numbers in the above experiments were all 3. Four full-thickness skin defect wounds were produced on the back of 18 male Sprague-Dawley rats aged 4 to 6 weeks. The wounds were divided into hydrogel alone group, hydrogel/nano sliver group, hydrogel scaffold/nano sliver group, and hydrogel scaffold/nano sliver/ASC group, and transplanted with the corresponding scaffolds, respectively. On post injury day (PID) 4, 7, 14, and 21, the wound healing was observed and the wound healing rate was calculated (n=6). On PID 7 and 14, histopathological changes of wounds were observed by hematoxylin eosin staining (n=6). On PID 21, collagen deposition of wounds was observed by Masson staining (n=3). Data were statistically analyzed with one-way analysis of variance, analysis of variance for repeated measurement, Bonferroni correction, and independent sample t test. Results: The sliver nano particles in nano silver solution with different mass concentrations were all round, in scattered distribution and uniform in size. The silver-containing GelMA hydrogels with different final mass fractions of GelMA all showed pore structures of different sizes and interconnections. The pore size of silver-containing GelMA hydrogel with 10% final mass fraction was significantly larger than that of silver-containing GelMA hydrogels with 15% and 20% final mass fractions (with P values both below 0.05). On treatment day 1, 3, and 7, the concentration of nano silver released from silver-containing GelMA hydrogel in vitro showed a relatively flat trend. On treatment day 14, the concentration of released nano silver in vitro increased rapidly. At 24 h of culture, the diameters of inhibition zone of GelMA hydrogel containing 0, 25, 50, and 100 mg/L nano silver against Staphylococcus aureus and Escherichia coli were 0, 0, 0.7, and 2.1 mm and 0, 1.4, 3.2, and 3.3 mm, respectively. At 48 h of culture, the proliferation activity of Fbs in 2 mg/L nano silver group and 5 mg/L nano silver group was both significantly higher than that in blank control group (P<0.05), and the proliferation activity of Fbs in 10 mg/L nano silver group, 25 mg/L nano silver group, and 50 mg/L nano silver group was all significantly lower than that in blank control group (P<0.05). Compared with the that of Fbs in 0 mg/L silver-containing GelMA hydrogel group, the proliferation activity of Fbs in 50 mg/L silver-containing GelMA hydrogel group and 100 mg/L silver-containing GelMA hydrogel group was all significantly decreased on culture day 1 (P<0.05); the proliferation activity of Fbs in 50 mg/L silver-containing GelMA hydrogel group was significantly increased (P<0.05), while the proliferation activity of Fbs in 100 mg/L silver-containing GelMA hydrogel group was significantly decreased on culture day 3 (P<0.05); the proliferation activity of Fbs in 100 mg/L silver-containing GelMA hydrogel group was significantly decreased on culture day 7 (P<0.05). The proliferation activity of ASCs in 3D bioprinting group show no statistically significant differences to that in non-printing group on culture day 1 (P>0.05). The proliferation activity of ASCs in 3D bioprinting group was significantly higher than that in non-printing group on culture day 3 and 7 (with t values of 21.50 and 12.95, respectively, P<0.05). On culture day 1, the number of dead ASCs in 3D bioprinting group was slightly more than that in non-printing group. On culture day 3 and 5, the majority of ASCs in 3D bioprinting group and non-printing group were living cells. On PID 4, the wounds of rats in hydrogel alone group and hydrogel/nano sliver group had more exudation, and the wounds of rats in hydrogel scaffold/nano sliver group and hydrogel scaffold/nano sliver/ASC group were dry without obvious signs of infection. On PID 7, there was still a small amount of exudation on the wounds of rats in hydrogel alone group and hydrogel/nano sliver group, while the wounds of rats in hydrogel scaffold/nano sliver group and hydrogel scaffold/nano sliver/ASC group were dry and scabbed. On PID 14, the hydrogels on the wound surface of rats in the four groups all fell off. On PID 21, a small area of wounds remained unhealed in hydrogel alone group. On PID 4 and 7, the wound healing rates of rats in hydrogel scaffold/nano sliver/ASC group were significantly higher than those of the other three groups (P<0.05). On PID 14, the wound healing rate of rats in hydrogel scaffold/nano sliver/ASC group was significantly higher than the wound healing rates in hydrogel alone group and hydrogel/nano sliver group (all P<0.05). On PID 21, the wound healing rate of rats in hydrogel alone group was significantly lower than that in hydrogel scaffold/nano sliver/ASC group (P<0.05). On PID 7, the hydrogels on the wound surface of rats in the four groups remained in place; on PID 14, the hydrogel in hydrogel alone group was separated from the wounds of rats, while some hydrogels still existed in the new tissue of the wounds of rats in the other three groups. On PID 21, the collagen arrangement in the wounds of rats in hydrogel alone group was out of order, while the collagen arrangement in the wounds of rats in hydrogel/nano sliver group, and hydrogel scaffold/nano sliver/ASC group was relatively orderly. Conclusions: Silver-containing GelMA hydrogel has good biocompatibility and antibacterial properties. Its three-dimensional bioprinted double-layer structure can better integrate with new formed tissue in the full-thickness skin defect wounds in rats and promote wound healing.

Role of functional hydrogel in promoting wound healing / 中华烧伤杂志

Cutaneous wounds are one of the commonest clinical diseases. At present, there are still many challenges in how to repair wounds quickly with high quality. With the rapid development and cross-integration of materials science and biomedicine, hydrogels that can integrate various excellent properties through flexible structural modification and combination of different functional components are widely applied in wound management and research. This paper attempted to summarize the role of hydrogel in promoting wound repair from the respects of matrix materials, special structures, and diverse functions of hydrogel.

Cell-loaded hydrogel microspheres based on droplet microfluidics: a review / 生物工程学报

Droplet microfluidics technology offers refined control over the flows of multiple fluids in micro/nano-scale, enabling fabrication of micro/nano-droplets with precisely adjustable structures and compositions in a high-throughput manner. With the combination of proper hydrogel materials and preparation methods, single or multiple cells can be efficiently encapsulated into hydrogels to produce cell-loaded hydrogel microspheres. The cell-loaded hydrogel microspheres can provide a three-dimensional, relatively independent and controllable microenvironment for cell proliferation and differentiation, which is of great value for three-dimensional cell culture, tissue engineering and regenerative medicine, stem cell research, single cell study and many other biological science fields. In this review, the preparation methods of cell-loaded hydrogel microspheres based on droplet microfluidics and its applications in biomedical field are summarized and future prospects are proposed.

Preparation of silk fibroin/hyaluronic acid composite hydrogel based on thiol-ene click chemistry / 浙江大学学报·医学版

OBJECTIVES@#To design and prepare silk fibroin/hyaluronic acid composite hydrogel.@*METHODS@#The thiol modified silk fibroin and the double-bond modified hyaluronic acid were rapidly cured into gels through thiol-ene click polymerization under ultraviolet light condition. The grafting rate of modified silk fibroin and hyaluronic acid was characterized by 1H NMR spectroscopy; the gel point and the internal microstructure of hydrogels were characterized by rheological test and scanning electron microscopy; the mechanical properties were characterized by compression test; the swelling rate and degradation rate were determined by mass method. The hydrogel was co-cultured with the cells, the cytotoxicity was measured by the lactate dehydrogenase method, the cell adhesion was measured by the float count method, and the cell growth and differentiation on the surface of the gel were observed by scanning electron microscope and fluorescence microscope.@*RESULTS@#The functional group substitution degrees of modified silk fibroin and hyaluronic acid were 17.99% and 48.03%, respectively. The prepared silk fibroin/hyaluronic acid composite hydrogel had a gel point of 40-60 s and had a porous structure inside the gel. The compressive strength was as high as 450 kPa and it would not break after ten cycles. The water absorption capacity of the composite hydrogel was 4-10 times of its own weight. Degradation experiments showed that the hydrogel was biodegradable, and the degradation rate reached 28%-42% after 35 d. The cell biology experiments showed that the cytotoxicity of the composite gel was low, the cell adhesion was good, and the growth and differentiation of the cells on the surface of the gel were good.@*CONCLUSIONS@#The photocurable silk fibroin/hyaluronic acid composite hydrogel can form a gel quickly, and has excellent mechanical properties, adjustable swelling rate and degradation degree, good biocompatibility, so it has promising application prospects in biomedicine.

Resiliência: avaliação de pacientes queimados em um hospital de urgência e emergência / Resilience: evaluation of burned patients in an urgency and emergency hospital / Resiliencia: evaluación de pacientes quemados en un hospital de urgencias y emergencias

A recuperação de vítimas de queimaduras é longa e dolorosa e afeta diversas esferas da vida do paciente. A resiliência, que se refere à capacidade humana de enfrentar e se adaptar a eventos adversos, exerce grande importância no processo de recuperação da queimadura. Logo, este trabalho objetiva avaliar a capacidade de resiliência de pacientes queimados, no momento da admissão e da alta hospitalar, em um hospital de emergência e urgência de Goiânia. Trata-se de um estudo descritivo, quantitativo e transversal que utiliza a Escala de Resiliência de Connor-Davidson (CD-RISC) como instrumento de mensuração. Na admissão hospitalar, a média da resiliência foi de 71,35, tendo sido observada uma relação significativa entre o fator Amparo da escala CD-RISC e a presença do(a) companheiro(a). O escore de resiliência encontrado nesta pesquisa é consistente com outros achados da literatura científica internacional e nacional referente à expressão da resiliência em vítimas de queimaduras e outros adoecimentos. A relação entre o fator Amparo e a presença de um(a) companheiro(a) enfatiza a importância da rede de apoio familiar na reabilitação do paciente queimado.(AU)

The recovery of burned patients is long and painful and impacts on different areas of people's lives. Resilience, which refers to the human capacity to face and adapt to adverse events, plays a major role in the process of recovery from burns. Therefore, the present study aims to assess the resilience of burned patients, on admission and hospital discharge, in an emergency and urgency hospital in Goiânia. This is a descriptive, quantitative and cross-sectional study that uses the Connor-Davidson Resilience Scale (CD RISC) as a measuring instrument. At hospital admission, the mean resilience was 71.35, with a significant association between the Support factor on the CD RISC scale and the presence of a partner. The resilience score found in the present study is consistent with other findings in the international and national scientific literature regarding the expression of resilience in victims of burns and other illnesses. The relationship between the Support factor and the presence of a partner emphasizes the importance of the family support network in the rehabilitation of the burned patient.(AU)

La recuperación de los pacientes quemados es larga y dolorosa e impacta en diferentes esferas de la vida de las personas. La resiliencia, que se refiere a la capacidad humana para enfrentar y adaptarse a eventos adversos, juega un papel importante en el proceso de recuperación de las quemaduras. Por tanto, el presente estudio tiene como objetivo evaluar la resiliencia de los pacientes quemados, en el momento del ingreso y el alta, en un hospital de emergencia y urgencia en Goiânia. Se trata de un estudio descriptivo, cuantitativo y transversal que utiliza la Escala de Resiliencia Connor-Davidson (CD RISC) como instrumento de medida. Al ingreso hospitalario, la resiliencia media fue de 71,35, con associación significativa entre el factor Amparo de la escala CD RISC y la presencia de pareja. El puntaje de resiliencia encontrado en el presente estudio es consistente con otros hallazgos en la literatura científica nacional e internacional sobre la expresión de resiliencia en víctimas de quemaduras y otras enfermedades. La relación entre el factor Amparo y la presencia de pareja enfatiza la importancia de la red de apoyo familiar en la rehabilitación del paciente quemado.(AU)

Locust bean gum hydrogels are bioadhesive and improve indole-3-carbinol cutaneous permeation: influence of the polysaccharide concentration

Abstract The locust bean gum (LBG) is a polysaccharide with thickening, stabilizing and gelling properties and it has been used in the preparation of pharmaceutical formulations. Hydrogels (HGs) are obtained from natural or synthetic materials that present interesting properties for skin application. This study aimed to develop HGs from LBG using indole-3-carbinol (I3C) as an asset model for cutaneous application. HGs were prepared by dispersing LBG (2%, 3% and 4% w/v) directly in cold water. The formulations showed content close to 0.5 mg/g (HPLC) and pH ranging from 7.25 to 7.41 (potentiometry). The spreadability factor (parallel plate method) was inversely proportional to LBG concentration. The rheological evaluation (rotational viscometer) demonstrated a non-Newtonian pseudoplastic flow behavior (Ostwald De Weale model), which is interesting for cutaneous application. The HET-CAM evaluation showed the non-irritating characteristic of the formulations. The bioadhesive potential demonstrated bioadhesion in a concentration-dependent manner. Permeation in human skin using Franz cells showed that the highest LBG concentration improved the skin distribution profile with greater I3C amounts in the viable skin layers. The present study demonstrated the feasibility of preparing HGs with LBG and the formulation with the highest polymer concentration was the most promising to transport active ingredients through the skin.

Development and clinical application of hydrogel formulations containing papain and urea for wound healing

Abstract Hydrogels are used for wound treatment, as they may contain one or more active components and protect the wound bed. Papain is one of the active substances that have been used with this purpose, alongside urea. In this paper, carboxypolymethylene hydrogels containing papain (2% and 10% concentrations) and urea (5% concentration) were produced. Physical-chemical stability was performed at 0, 7, 15 and 30 days at 2-8ºC, 25ºC and 40ºC, as well as the rheological aspects and proteolytic activity of papain by gel electrophoresis. Clinical efficacy of the formulations in patients with lower limb ulcers was also evaluated in a prospective, single-center, randomized, double-blind and comparative clinical trial. The results showed 7-day stability for the formulations under 25ºC, in addition to approximately 100% and 15% of protein activity for 10% and 2% papain hydrogel, respectively. The rheological profile was non-Newtonian for the 10% papain hydrogel tested. There were no significant differences regarding the mean time for healing of the lesions, although 10% papain presented a better approach to be used in all types of tissue present in the wound bed.

Hydrogel loaded with exosomes from Wharton 's Jelly-derived mesenchymal stem cells enhances wound healing in mice / 浙江大学学报·医学版

OBJECTIVES@#To explore the effect of hydrogel loaded with exosomes from Wharton's Jelly-derived mesenchymal stem cell (WJMSC) on wound healing.@*METHODS@#Exosomes were extracted from WJMSC, and the morphology and size of WJMSC-derived exosomes (WEX) were analyzed by transmission electron microscopy and nanoparticle size analyzer, respectively. The surface markers CD9, CD81, and Calnexin of WEX were detected by Western blotting. Exosome-loaded alginate hydrogel (WEX-gel) was prepared; its morphology was studied by scanning electron microscope, and its rheological behavior was examined by a rheometer. The in vitro drug release performance of WEX-gel was investigated by BCA method. RAW264.7 cells were treated with alginate hydrogel, WEX and WEX-gel, respectively; and the expression of CD86 and CD206 in macrophages was detected by flow cytometry. A full-thickness skin wound model was established in mice; the model mice were randomly divided into blank control group, WEX control group and WEX-gel group, and PBS, WEX and WEX-gel were applied to the wound area of mice, respectively. On day 3, the skin tissue of mice was excised, and the antibacterial effect of WEX hydrogel was evaluated by plate counting. On day 15, the mice were euthanized and the percentage of residual wounds was calculated. The histological changes of the skin wound were observed after hematoxylin and eosin (HE) and Masson stainings. The expression of CD86, CD206, CD31 and vascular endothelial growth factor (VEGF) in the skin wound tissue was detected by immunohistochemistry.@*RESULTS@#Exosomes were successfully extracted from WJMSC. WEX-gel presented a regular three-dimensional network structure, good rheology and controlled drug release performance. WEX-gel promoted the polarization of RAW264.7 cells from the M1 phenotype to M2 phenotype in vitro. The residual wound percentage in blank control group, WEX control group and WEX-gel group were (27.5±3.4)%, (15.3±1.2)% and (7.6±1.1)%, respectively (P<0.05). The antibacterial property of WEX-gel is better than that of WEX (P<0.05). The dermis thickness, the number of new hair follicles, and the rate of collagen deposition in the WEX-gel group were significantly higher than those in the other two groups (all P<0.05). The expression of CD206, CD31 and VEGF in skin wound tissue was higher and the expression of CD86 was lower in WEX-gel group than those in other two groups (all P<0.05).@*CONCLUSIONS@#WEX-gel can significantly promote wound healing in mice by regulating the polarization of macrophages.

A dual-crosslinked injectable hydrogel derived from muscular decellularized matrix promoting myoblasts proliferation and myogenic differentiation / 中国修复重建外科杂志

OBJECTIVE@#To investigate the feasibility of a dual-crosslinked injectable hydrogel derived from acellular musclar matrix (AMM) for promoting myoblasts proliferation and myogenic differentiation.@*METHODS@#Firstly, hyaluronic acid was oxidized with NaIO 4 and methylated to prepare methacrylamidated oxidized hyaluronic acid (MOHA). Then, AMM obtained by washing enzymatically treated muscle tissue was aminolyzed to prepare aminated AMM (AAMM). MOHA hydrogel and AAMM were crosslinked using Schiff based reaction and UV radiation to prepare a dual-crosslinked MOHA/AAMM injectable hydrogel. Fourier transform infrared spectroscopy (FTIR) was used to characterize MOHA, AAMM, and MOHA/AAMM hydrogels. The injectability of MOHA/AAMM hydrogel were evaluated by manual injection, and the gelation performance was assessed by UV crosslinking. The rheological properties and Young's modulus of the hydrogel were examined through mechanical tests. The degradation rate of the hydrogel was assessed by immersing it in PBS. The active components of the hydrogel were verified using immunofluorescence staining and ELISA assay kits. The promotion of cell proliferation by the hydrogel was tested using live/dead staining and cell counting kit 8 (CCK-8) assays after co-culturing with C2C12 myoblasts for 9 days. The effect of the hydrogel on myogenic differentiation was evaluated by immunofluorescence staining and real time quantitative polymerase chain reaction (RT-qPCR).@*RESULTS@#FTIR spectra confirmed the successful preparation of MOHA/AAMM hydrogel. The hydrogel exhibited good injectability and gelation ability. Compared to MOHA hydrogel, MOHA/AAMM hydrogel exhibited higher viscosity and Young's modulus, a reduced degradation rate, and contained a higher amount of collagen (including collagen type Ⅰ and collagen type Ⅲ) as well as bioactive factors (including epidermal growth factor, fibroblast growth factor 2, vascular endothelial growth factor, and insulin-like growth factor 1). The live/dead cell staining and CCK-8 assay indicated that with prolonged incubation time, there was a significant increase in viable cells and a decrease in dead cells in the C2C12 myoblasts within the MOHA/AAMM hydrogel. Compared with MOHA hydrogel, the difference was significant at each time point ( P<0.05). Immunofluorescence staining and RT-qPCR analysis demonstrated that the deposition of IGF-1 and expression levels of myogenic-related genes (including Myogenin, Troponin T, and myosin heavy chain) in the MOHA/AAMM group were significantly higher than those in the MOHA group ( P<0.05).@*CONCLUSION@#The MOHA/AAMM hydrogel prepared based on AMM can promote myoblasts proliferation and myogenic differentiation, providing a novel dual-crosslinked injectable hydrogel for muscle tissue engineering.

Bone/cartilage immunomodulating hydrogels: construction strategies and applications / 中国修复重建外科杂志

OBJECTIVE@#To review the research progress in the construction strategy and application of bone/cartilage immunomodulating hydrogels.@*METHODS@#The literature related to bone/cartilage immunomodulating hydrogels at home and abroad in recent years was reviewed and summarized from the immune response mechanism of different immune cells, the construction strategy of immunomodulating hydrogels, and their practical applications.@*RESULTS@#According to the immune response mechanism of different immune cells, the biological materials with immunoregulatory effect is designed, which can regulate the immune response of the body and thus promote the regeneration of bone/cartilage tissue. Immunomodulating hydrogels have good biocompatibility, adjustability, and multifunctionality. By regulating the physical and chemical properties of hydrogel and loading factors or cells, the immune system of the body can be purposively regulated, thus forming an immune microenvironment conducive to osteochondral regeneration.@*CONCLUSION@#Immunomodulating hydrogels can promote osteochondral repair by affecting the immunomodulation process of host organs or cells. It has shown a wide application prospect in the repair of osteochondral defects. However, more data support from basic and clinical experiments is needed for this material to further advance its clinical translation process.

Injectable hydrogel microspheres experimental research for the treatment of osteoarthritis / 中国修复重建外科杂志

OBJECTIVE@#To prepare a novel hyaluronic acid methacrylate (HAMA) hydrogel microspheres loaded polyhedral oligomeric silsesquioxane-diclofenac sodium (POSS-DS) patricles, then investigate its physicochemical characteristics and in vitro and in vivo biological properties.@*METHODS@#Using sulfhydryl POSS (POSS-SH) as a nano-construction platform, polyethylene glycol and DS were chemically linked through the "click chemistry" method to construct functional nanoparticle POSS-DS. The composition was analyzed by nuclear magnetic resonance spectroscopy and the morphology was characterized by transmission electron microscopy. In order to achieve drug sustained release, POSS-DS was encapsulated in HAMA, and hybrid hydrogel microspheres were prepared by microfluidic technology, namely HAMA@POSS-DS. The morphology of the hybrid hydrogel microspheres was characterized by optical microscope and scanning electron microscope. The in vitro degradation and drug release efficiency were observed. Cell counting kit 8 (CCK-8) and live/dead staining were used to detect the effect on chondrocyte proliferation. Moreover, a chondrocyte inflammation model was constructed and cultured with HAMA@POSS-DS. The relevant inflammatory indicators, including collagen type Ⅱ, aggrecan (AGG), matrix metalloproteinase 13 (MMP-13), recombinant A disintegrin and metalloproteinase with thrombospondin 5 (Adamts5), and recombinant tachykinin precursor 1 (TAC1) were detected by immunofluorescence staining and real-time fluorescence quantitative PCR, with normal cultured chondrocytes and the chondrocyte inflammation model without treatment as control group and blank group respectively to further evaluate their anti-inflammatory activity. Finally, by constructing a rat model of knee osteoarthritis, the effectiveness of HAMA@POSS-DS on osteoarthritis was evaluated by X-ray film and Micro-CT examination.@*RESULTS@#The overall particle size of POSS-DS nanoparticles was uniform with a diameter of about 100 nm. HAMA@POSS-DS hydrogel microspheres were opaque spheres with a diameter of about 100 μm and a spherical porous structure. The degradation period was 9 weeks, during which the loaded POSS-DS nanoparticles were slowly released. CCK-8 and live/dead staining showed no obvious cytotoxicity at HAMA@POSS-DS, and POSS-DS released by HAMA@POSS-DS significantly promoted cell proliferation (P<0.05). In the chondrocyte anti-inflammatory experiment, the relative expression of collagen type Ⅱ mRNA in HAMA@POSS-DS group was significantly higher than that in control group and blank group (P<0.05). The relative expression level of AGG mRNA was significantly higher than that of blank group (P<0.05). The relative expressions of MMP-13, Adamts5, and TAC1 mRNA in HAMA@POSS-DS group were significantly lower than those in blank group (P<0.05). In vivo experiments showed that the joint space width decreased after operation in rats with osteoarthritis, but HAMA@POSS-DS delayed the process of joint space narrowing and significantly improved the periarticular osteophytosis (P<0.05).@*CONCLUSION@#HAMA@POSS-DS can effectively regulate the local inflammatory microenvironment and significantly promote chondrocyte proliferation, which is conducive to promoting cartilage regeneration and repair in osteoarthritis.

Research progress on biocomposites based on bioactive glass / 生物医学工程学杂志

Bioactive glass (BG) has been widely used in the preparation of artificial bone scaffolds due to its excellent biological properties and non-cytotoxicity, which can promote bone and soft tissue regeneration. However, due to the brittleness, poor mechanical strength, easy agglomeration and uncontrollable structure of glass material, its application in various fields is limited. In this regard, most current researches mainly focus on mixing BG with organic or inorganic materials by freeze-drying method, sol-gel method, etc., to improve its mechanical properties and brittleness, so as to increase its clinical application and expand its application field. This review introduces the combination of BG with natural organic materials, metallic materials and non-metallic materials, and demonstrates the latest technology and future prospects of BG composite materials through the development of scaffolds, injectable fillers, membranes, hydrogels and coatings. The previous studies show that the addition of BG improves the mechanical properties, biological activity and regeneration potential of the composites, and broadens the application of BG in the field of bone tissue engineering. By reviewing the recent BG researches on bone regeneration, the research potential of new materials is demonstrated, in order to provide a reference for future related research.

Physicochemical properties of a novel chiral self-assembling peptide R-LIFE-1 and its controlled release to exosomes / 生物医学工程学杂志

This research aims to investigate the encapsulation and controlled release effect of the newly developed self-assembling peptide R-LIFE-1 on exosomes. The gelling ability and morphological structure of the chiral self-assembling peptide (CSAP) hydrogel were examined using advanced imaging techniques, including atomic force microscopy, transmission electron microscopy, and cryo-scanning electron microscopy. The biocompatibility of the CSAP hydrogel was assessed through optical microscopy and fluorescent staining. Exosomes were isolated via ultrafiltration, and their quality was evaluated using Western blot analysis, nanoparticle tracking analysis, and transmission electron microscopy. The controlled release effect of the CSAP hydrogel on exosomes was quantitatively analyzed using laser confocal microscopy and a BCA assay kit. The results revealed that the self-assembling peptide R-LIFE-1 exhibited spontaneous assembly in the presence of various ions, leading to the formation of nanofibers. These nanofibers were cross-linked, giving rise to a robust nanofiber network structure, which further underwent cross-linking to generate a laminated membrane structure. The nanofibers possessed a large surface area, allowing them to encapsulate a substantial number of water molecules, thereby forming a hydrogel material with high water content. This hydrogel served as a stable spatial scaffold and loading matrix for the three-dimensional culture of cells, as well as the encapsulation and controlled release of exosomes. Importantly, R-LIFE-1 demonstrated excellent biocompatibility, preserving the growth of cells and the biological activity of exosomes. It rapidly formed a three-dimensional network scaffold, enabling the stable loading of cells and exosomes, while exhibiting favorable biocompatibility and reduced cytotoxicity. In conclusion, the findings of this study support the notion that R-LIFE-1 holds significant promise as an ideal tissue engineering material for tissue repair applications.

Research advances on the promotive healing effect of hydrogel dressing for diabetic foot wound / 中华烧伤杂志

In recent years, the number of diabetic patients has gradually increased, and the number of patients with diabetic foot has also increased. Diabetic foot has a high rate of disability and death, seriously affects the patients' quality of life, shortens life expectancy, and brings heavy social burden. The current treatment methods for diabetic foot are insufficient. The concepts and methods of tissue engineering provide new thoughts and means for the treatment of diabetic foot. This article introduces the pathogenesis of diabetic foot wounds, the factors leading to non-healing of diabetic foot, the applications of functional hydrogel dressings in the treatment of diabetic foot and their technical methods of functional hydrogel dressings for treating skin wounds in diabetic animals, and the future development direction of functional hydrogel dressing for treating diabetic foot wounds is prospected.

Effects of in situ cross-linked graphene oxide-containing gelatin methacrylate anhydride hydrogel on wound vascularization of full-thickness skin defect in mice / 中华烧伤杂志

Objective: To prepare graphene oxide (GO)-containing gelatin methacrylate anhydride (GelMA) hydrogel and to investigate the effects of in situ photopolymerized GO-GelMA composite hydrogel in wound vascularization of full-thickness skin defect in mice. Methods: The experimental study method was used. The 50 μL of 0.2 mg/mL GO solution was evenly applied onto the conductive gel, and the structure and size of GO were observed under field emission scanning electron microscope after drying. Human skin fibroblasts (HSFs) were divided into 0 μg/mL GO (without GO solution, the same as below) group, 0.1 μg/mL GO group, 1.0 μg/mL GO group, 5.0 μg/mL GO group, and 10.0 μg/mL GO group treated with GO of the corresponding final mass concentration, and the absorbance value was detected using a microplate analyzer after 48 h of culture to reflect the proliferation activity of cells (n=6). HSFs and human umbilical vein vascular endothelial cells (HUVECs) were divided into 0 μg/mL GO group, 0.1 μg/mL GO group, 1.0 μg/mL GO group, and 5.0 μg/mL GO group treated with GO of the corresponding final mass concentration, and the migration rates of HSFs at 24 and 36 h after scratching (n=5) and HUVECs at 12 h after scratching (n=3) were detected by scratch test, and the level of vascular endothelial growth factor (VEGF) secreted by HSFs after 4, 6, and 8 h of culture was detected by enzyme-linked immunosorbent assay method (n=3). The prepared GO-GelMA composite hydrogels containing GO of the corresponding final mass concentration were set as 0 μg/mL GO composite hydrogel group, 0.1 μg/mL GO composite hydrogel group, 1.0 μg/mL GO composite hydrogel group, and 5.0 μg/mL GO composite hydrogel group to observe their properties before and after cross-linking, and to detect the release of GO after soaking with phosphate buffer solution for 3 and 7 d (n=3). The full-thickness skin defect wounds were made on the back of 16 6-week-old female C57BL/6 mice. The mice treated with in situ cross-linked GO-GelMA composite hydrogel containing GO of the corresponding final mass concentration were divided into 0 μg/mL GO composite hydrogel group, 0.1 μg/mL GO composite hydrogel group, 1.0 μg/mL GO composite hydrogel group, and 5.0 μg/mL GO composite hydrogel group according to the random number table, with 4 mice in each group. The general condition of wound was observed and the wound healing rate was calculated on 3, 7, and 14 d of treatment, the wound blood perfusion was detected by laser Doppler flowmetry on 3, 7, and 14 d of treatment and the mean perfusion unit (MPU) ratio was calculated, and the wound vascularization on 7 d of treatment was observed after hematoxylin-eosin staining and the vascular density was calculated (n=3). The wound tissue of mice in 0 μg/mL GO composite hydrogel group and 0.1 μg/mL GO composite hydrogel group on 7 d of treatment was collected to observe the relationship between the distribution of GO and neovascularization by hematoxylin-eosin staining (n=3) and the expression of VEGF by immunohistochemical staining. Data were statistically analyzed with analysis of variance for repeated measurement, one-way analysis of variance, and Tukey's method. Results: GO had a multilayered lamellar structure with the width of about 20 μm and the length of about 50 μm. The absorbance value of HSFs in 10.0 μg/mL GO group was significantly lower than that in 0 μg/mL GO group after 48 h of culture (q=7.64, P<0.01). At 24 h after scratching, the migration rates of HSFs were similar in the four groups (P>0.05); at 36 h after scratching, the migration rate of HSFs in 0.1 μg/mL GO group was significantly higher than that in 0 μg/mL GO group, 1.0 μg/mL GO group, and 5.0 μg/mL GO group (with q values of 7.48, 10.81, and 10.20, respectively, P<0.01). At 12 h after scratching, the migration rate of HUVECs in 0.1 μg/mL GO group was significantly higher than that in 0 μg/mL GO group, 1.0 μg/mL GO group, and 5.0 μg/mL GO group (with q values of 7.11, 8.99, and 14.92, respectively, P<0.01), and the migration rate of HUVECs in 5.0 μg/mL GO group was significantly lower than that in 0 μg/mL GO group and 1.0 μg/mL GO group (with q values of 7.81 and 5.33, respectively, P<0.05 or P<0.01 ). At 4 and 6 h of culture, the VEGF expressions of HSFs in the four groups were similar (P>0.05); at 8 h of culture, the VEGF expression of HSFs in 0.1 μg/mL GO group was significantly higher than that in 0 μg/mL GO group and 5.0 μg/mL GO group (with q values of 4.75 and 4.48, respectively, P<0.05). The GO-GelMA composite hydrogels in the four groups were all red liquid before cross-linking, which turned to light yellow gel after cross-linking, with no significant difference in fluidity. The GO in the GO-GelMA composite hydrogel of 0 μg/mL GO composite hydrogel group had no release of GO at all time points; the GO in the GO-GelMA composite hydrogels of the other 3 groups was partially released on 3 d of soaking, and all the GO was released on 7 d of soaking. From 3 to 14 d of treatment, the wounds of mice in the 4 groups were covered with hydrogel dressings, kept moist, and gradually healed. On 3, 7, and 14 d of treatment, the wound healing rates of mice in the four groups were similar (P>0.05). On 3 d of treatment, the MPU ratio of wound of mice in 0.1 μg/mL GO composite hydrogel group was significantly higher than that in 0 μg/mL GO composite hydrogel group, 1.0 μg/mL GO composite hydrogel group, and 5.0 μg/mL GO composite hydrogel group (with q values of 10.70, 11.83, and 10.65, respectively, P<0.05 or P<0.01). On 7 and 14 d of treatment, the MPU ratios of wound of mice in the four groups were similar (P>0.05). The MPU ratio of wound of mice in 0.1 μg/mL GO composite hydrogel group on 7 d of treatment was significantly lower than that on 3 d of treatment (q=14.38, P<0.05), and that on 14 d of treatment was significantly lower than that on 7 d of treatment (q=27.78, P<0.01). On 7 d of treatment, the neovascular density of wound of mice on 7 d of treatment was 120.7±4.1 per 200 times of visual field, which was significantly higher than 61.7±1.3, 77.7±10.2, and 99.0±7.9 per 200 times of visual field in 0 μg/mL GO composite hydrogel group, 1.0 μg/mL GO composite hydrogel group, and 5.0 μg/mL GO composite hydrogel group (with q values of 12.88, 7.79, and 6.70, respectively, P<0.01), and the neovascular density of wound of mice in 1.0 μg/mL GO composite hydrogel group and 5.0 μg/mL GO composite hydrogel group was significantly higher than that in 0 μg/mL GO composite hydrogel group (with q values of 5.10 and 6.19, respectively, P<0.05). On 7 d of treatment, cluster of new blood vessels in wound of mice in 0.1 μg/mL GO composite hydrogel group was significantly more than that in 0 μg/mL GO composite hydrogel group, and the new blood vessels were clustered near the GO; a large amount of VEGF was expressed in wound of mice in 0.1 μg/mL GO composite hydrogel group in the distribution area of GO and new blood vessels. Conclusions: GO with mass concentration lower than 10.0 μg/mL had no adverse effect on proliferation activity of HSFs, and GO of 0.1 μg/mL can promote the migration of HSFs and HUVECs, and can promote the secretion of VEGF in HSFs. In situ photopolymerized of GO-GelMA composite hydrogel dressing can promote the wound neovascularization of full-thickness skin defect in mice and increase wound blood perfusion in the early stage, with GO showing an enrichment effect on angiogenesis, and the mechanism may be related to the role of GO in promoting the secretion of VEGF by wound cells.

Effects of methacrylic anhydride gelatin hydrogel loaded with silver and recombinant human basic fibroblast growth factor on deep partial-thickness burn wounds in rabbits / 中华烧伤杂志

Objective: To investigate the effects of methacrylic anhydride gelatin (GelMA) hydrogel loaded with silver and recombinant human basic fibroblast growth factor (rh-bFGF) on deep partial-thickness burn wounds in rabbits. Methods: The experimental research method was adopted. Low-concentration GelMA materials, medium-concentration GelMA materials and high-concentration GelMA materials containing different concentrations of methacrylic anhydride (MA) were prepared, after adding photoinitiator, low-concentration GelMA hydrogels, medium-concentration GelMA hydrogels, and high-concentration GelMA hydrogels were obtained, respectively. The nuclear magnetic resonance spectroscopy was performed to detect the hydrogen nuclear magnetic resonance spectra of the above-mentioned three concentrations of GelMA materials, and to calculate the degree of substitution according to the spectrum diagram. The three-dimensional microstructure and pore size of 3 types of above-mentioned GelMA hydrogels were detected by field emission scanning electron microscopy (FESEM), with 9 samples measured. According to the selected concentration of MA, ten kinds of solutions of GelMA with different concentration of silver (silver-containing GelMA) were synthesized, and the silver-containing GelMA solution of each concentration was divided into three parts, and then exposed to ultraviolet light lasting for 20, 25, and 35 s, respectively. After adding photoinitiator,the corresponding silver-containing GelMA hydrogels were obtained. The residual degradation rate of silver-containing GelMA hydrogel with different photocrosslinking times was detected by collagenase degradation method at degradation of 12, 24, 36, and 48 h; and the time required for complete degradation was detected, and the sample number was 5. The inhibition zone diameter of GelMA hydrogel under above screened photocrosslinking times containing 10 concentrations of silver against Staphylococcus aureus was measured to reflect its antibacterial ability, and the sample numbers were all 5. The silver-containing GelMA hydrogel with statistical significance compared with the antibacterial circle diameter of the silver-containing GelMA hydrogel containing the lowest concentration (no silver) was considered as having antibacterial activity. The three-dimensional microstructure and pore size of the silver-containing GelMA hydrogels with antibacterial activity and the lowest drug concentration selected were detected by FESEM, and the sample numbers were all 9. The freeze-dried alone GelMA hydrogel and the freeze-dried silver-containing GelMA hydrogel were soaked in phosphate buffer solution for 24 h, respectively, then the swelling rate of the two GelMA hydrogel were calculated and compared by weighing method, and the sample number was 5. GelMA hydrogel containing silver and rh-bFGF, namely compound hydrogel for short, was prepared according to the preliminary experiment and the above experimental results. The appearance of the composite hydrogel was observed in general, and its three-dimensional microstructure and pore size were detected by FESEM. The deep partial-thickness burn wound was made on the back of 30 rabbits (aged 4-6 months, female half and half). Meanwhile, with the rabbit head as the benchmark, the wounds on the left side of the spine were treated as composite hydrogel treatment group, and the wounds on the right side were treated as gauze control group, and which were treated accordingly. On post injury day (PID) 3, 7, 14, 21, and 28, the healing of wounds in the two groups was observed. On PID 7, 14, 21, and 28, the wound healing area was recorded and the healing rate was calculated, with a sample number of 30. Data were statistically analyzed with analysis of variance for repeated measurement, one-way analysis of variance, and independent sample t test. Results: The substitution degree among low-concentration GelMA materials, medium-concentration GelMA materials, and high-concentration GelMA materials was significantly different (F=1 628.00, P<0.01). The low-concentration GelMA hydrogel had a loose and irregular three-dimensional spatial network structure with a pore size of (60±17) μm; the medium-concentration GelMA hydrogel had a relatively uniform three-dimensional spatial network and pore size with a pore size of (45±13) μm; the high-concentration GelMA hydrogel had the dense and disordered three-dimensional spatial network with a pore size of (25±15) μm, the pore sizes of 3 types of GelMA hydrogels were significantly differences (F=12.20, P<0.01), and medium concentration of MA was selected for the concentration of subsequent materials. The degradability of silver-containing GelMA hydrogels with different concentrations of the same photocrosslinking time was basically same. The degradation residual rates of silver-containing GelMA hydrogels with 20, 25, and 35 s crosslinking time at 12 h were (74.2±1.7)%, (85.3±0.9)%, and (93.2±1.2)%, respectively; the residual rates of degradation at 24 h were (58.3±2.1)%, (65.2±1.8)%, and (81.4±2.6)%, respectively; the residual rates of degradation at 36 h were (22.4±1.9)%, (45.2±1.7)%, and (68.1±1.4)%, respectively; the residual rates of degradation at 48 h were (8.2±1.7)%, (32.4±1.3)%, and (54.3±2.2)%, respectively, and 20, 25, and 30 s photocrosslinking time required for complete degradation of silver-containing GelMA hydrogels were (50.2±2.4), (62.4±1.4), and (72.2±3.2) h, and the difference was statistically significant (F=182.40, P<0.01), 25 s were selected as the subsequent photocrosslinking time. The antibacterial diameters of 10 types of silver-containing GelMA hydrogels against Staphylococcus aureus from low to high concentrations were (2.6±0.4), (2.5±0.4), (3.2±0.4), (12.1±0.7), (14.8±0.7), (15.1±0.5), (16.2±0.6), (16.7±0.5), (16.7±0.4), and (16.7±0.6) mm, respectively, and which basically showed a concentration-dependent increasing trend, and the overall difference was statistically significant (F=428.70, P<0.01). Compared with the silver-containing GelMA hydrogel with the lowest concentration, the antibacterial circle diameters of other silver-containing GelMA hydrogels with antibacterial ability from low to high concentration were significantly increased (with t values of 26.35, 33.84, 43.65, 42.17, 49.24, 55.74, and 43.72, respectively, P<0.01). The silver-containing GelMA hydrogel with the antibacterial diameter of (12.1±0.7) mm had the lowest antibacterial activity against Staphylococcus aureus and the lowest drug loading concentration, and the concentration of silver was selected for the concentration of subsequent materials. The microscopic morphology of the silver-containing GelMA hydrogel containing silver element with a pore size of (45±13) μm had a regular and linear strip-like structure. After soaking for 24 h, the swelling ratio of silver-containing GelMA hydrogel was similar to that of alone GelMA hydrogel. The composite hydrogel was colorless, clear and transparent, and its three-dimensional microstructure was a regular and uniform grid, with a filament network structure inside, and the pore size of (40±21) μm. On PID 3, a large amount of necrotic tissue and exudate of rabbit wound in composite hydrogel group were observed, and scattered scabs, a small amount of necrotic tissue and exudate of rabbit wound in gauze control group were observed. On PID 7, the area of rabbit wound in composite hydrogel group was significantly reduced, and adhesion of rabbit wound and gauze in gauze control group was observed. On PID 14, In composite hydrogel group, the rabbit wound surface was ruddy, and the growth of granulation tissue was observed, and in gauze control group, the rabbit wound base was pale, and the blood supply was poor. On PID 21, the rabbit wounds in composite hydrogel group healed completely, and rabbit wound in gauze control group had healing trend. On PID 28, new hair could be seen on rabbit wound surface in composite hydrogel group; oval wound of rabbit in gauze control group still remained. On PID 7, 14, 21, and 28, the wound healing areas of rabbit in composite hydrogel group were significantly larger than those in gauze control group (with t values of 2.24, 4.43, 7.67, and 7.69, respectively, P<0.05 or P<0.01). Conclusions: The medium-concentration GelMA hydrogel has good physical and chemical properties in terms of swelling and degradability. The screened silver-containing GelMA hydrogels had the lowest antibacterial activity and the lowest drug loading concentration. Composite hydrogel can significantly shorten the healing time of deep partial-thickness burn wounds in rabbits.