Fabrication of gelatin methacryloyl/graphene oxide conductive hydrogel for bone repair.

The ideal bone repair materials possess a series of properties, such as injectability, good mechanical properties and bone inducibility. In the present study, gelatin methacryloyl (GelMA) and graphene oxide (GO) were selected to prepare conductive hydrogel by changing the concentration of GelMA and GO during the cross-link process. The effects of different contents of GelMA and GO to the hydrogel performance were investigated. The results showed that the mechanical properties of the hydrogel kept 16.37 ± 1.89 KPa after adding 0.1% GO, while the conductivity was improved to 1.36 ± 0.09 µS/cm. The porosity of hydrogel before and after mineralization could reach more than 90%. The mechanical properties of mineralized hydrogel was improved significantly, could reach 26.38 ± 2.29 KPa. Cell experiments indicated that the mineralized hydrogel with electrical stimulation obviously improve the alkaline phosphatase activity of the cells. GelMA/GO conductive hydrogel could be a promising candidate for bone repair and bone tissue engineering.

Electrospun nanofibers with antibacterial properties for wound dressings.

The antibacterial nanofibers have been proposed as an interesting material for wound healing management, since the majority of traditional wound dressings exhibit issues and complications such as infection, pain, discomfort, and poor adhesive proprieties. It allows the organism's passage through the dressing and delay the wound healing progression. Electrospun nanofibers have been intensively investigated for wound dressings in tissue engineering applications due to their distinctive features and structural similarities to the extracellular matrix including the various available methods to load the antibacterial compounds onto the nanofiber webs. To construct an effective electrospun wound dressing, various efforts have been made to design different strategies to develop advanced polymers, such as employing synthetic and/or natural materials, modifying fiber orientation, and incorporating chemicals and metallic nanoparticles (NPs) as intriguing materials for antibacterial bandages. Thus, this review summarizes the relevant recent studies on the production of electrospun antibacterial nanofibers from a wide variety of polymers used in biomedical applications for wound dressings.

Engineered bone tissues using biomineralized gelatin methacryloyl/sodium alginate hydrogels.

At present, the treatment of bone defect is one of the most concerned problems in biomedical fields. Despite the wide variety of scaffolds, there is a challenge to select materials that can mimic the structural integrity and biocompatibility of natural bone. In our study, gelatin methacryloyl (GelMA) and sodium alginate (Alg) were used to prepare three-dimensional (3D) GelMA/Alg hybrid hydrogel, which can simulate the structure and biological function of natural extracellular matrix due to their high water content and porous structure. The interconnected and homogeneous pores of the scaffold facilitate the transport of nutrients during the bone regeneration. Then hydroxyapatite (HA) coated GelMA/Alg (GelMA/Alg-HA) hydrogel was obtained by sequential mineralization. The mineralized hydrogel was obtained by immersing hydrogel alternately in a solution of calcium and phosphorus at 37 °C. The hydrogel was modified with a coating of HA under a mild condition. The calcium crosslinked Alg could provide nucleation sites for HA crystals. And the sequential mineralization will improve the physical properties and osteoinductivity of the hydrogels by introducing HA, which is similar to the mineral component of natural bone. Analytical results confirmed that the HA particles were uniformly distributed in the surface of the hydrogels and the mineral contents were about 40% after three cycles. The compressive strength was improved from 22.43 ± 6.39 to 131.03 ± 9.26 kPa. In addition, MC3T3-E1 cell co-culture experiments shown that the mineralized GelMA/Alg-HA hybrid hydrogel possess good biocompatibility, which is conducive to the growth of new bone tissue and bone repair.

Fabrication of adhesive hydrogels based on poly (acrylic acid) and modified hyaluronic acid.

Hydrogel wound dressings with good flexibility and adhesiveness to resist deformation during wound movement are urgently needed in clinical application. In this work, the hydrogels based on poly (acrylic acid) and N-hydroxysuccinimide grafted hyaluronic acid (PAA/HA-NHS) with good elasticity and adhesiveness were prepared by chemical cross-linking and hydrogen bonding. The elastic and adhesive properties within the PAA hydrogels could reach a balance by adjusting the concentration of potassium persulfate (KPS) and N, N'-methylenebisacrylamide (MBA). Subsequently, HA-NHS was incorporated into the PAA hydrogel system. The mechanical test revealed that the elongation at break and interfacial toughness of the PAA/HA-NHS hydrogels could reach 265.79 ± 21.93% and 52.88 ± 3.51 J/m2, respectively. In addition, the hydrogels possess a connected porous network and well water absorption ability (with porosity of 51.90 ± 0.11% and swelling ratio in wet state of 122.17 ± 2.78%). In vitro experiment demonstrates that the PAA/HA-NHS hydrogels exhibit nontoxic and cell in-adhesive properties. The PAA/HA-NHS hydrogels could cover the wound spots directly, stretch with the skin movement and gently remove from the wound tissue due to the suitable adhesiveness and poor cell adhesion. In conclusion, the PAA/HA-NHS hydrogels show great application value in the field of wound dressing.

Berberine carried gelatin/sodium alginate hydrogels with antibacterial and EDTA-induced detachment performances.

Most existing hydrogel wound dressings lack gentle detachment property. In this work, novel hydrogels with anti-bacterial and induced detachment properties were prepared. Both gelatin (G) and sodium alginate (SA) are natural polymer materials. The G/SA hydrogels were prepared by dual cross-linking. The addition of SA significantly improves the mechanical properties of composite hydrogels. The tensile modulus and elongation at break of the G/SA hydrogels with 2.0% SA could reach 99.23 ± 2.18 kPa and 85.47 ± 5.01%, respectively. In addition, the interconnected porous network and high swelling ratio (over 9.99 ± 0.33) are beneficial to the transmission of oxygen and absorption of exudates to accelerate the healing of wound. Subsequently, berberine (BBR) was loaded into the G/SA hydrogels. The BBR/G/SA hydrogels show sustained drug release for 168 h and exhibit anti-bacterial effect against Staphylococcus aureus. The results of L929 cells cultured with the hydrogel extracts indicate good biocompatibility. Finally, results of EDTA-induced detachment performances demonstrate that the hydrogels could be removed from the wound as the internal structure destroyed. All illustrated results above demonstrated the BBR carried G/SA hydrogels have potential used as wound dressing materials in future.