Correction: Flexible, micro-porous chitosan-gelatin hydrogel/nanofibrin composite bandages for treating burn wounds.

[This corrects the article DOI: 10.1039/C4RA11969J.].

Additively manufactured biphasic construct loaded with BMP-2 for vertical bone regeneration: A pilot study in rabbit.

Vertical bone augmentation of the jaws is required when the height of bone is insufficient at the site of dental implant placement. In this proof of concept study, we investigated the potential of a biphasic polycaprolactone construct combined with a hyaluronic acid based hydrogel loaded with recombinant human bone morphogenetic growth factor-2 (BMP-2) for vertical bone regeneration. The biphasic scaffold consisted of an outer shell manufactured by fused deposition modelling, mimicking native cortical bone and providing mechanical and space maintenance properties essential for bone formation. Within this shell, a 90% porous melt electrospun microfibrous mesh mimicking the architecture of cancellous bone was incorporated in order to facilitate hydrogel loading and subsequent osteogenesis and angiogenesis. The in vitro performances of the biphasic construct demonstrated that BMP-2 was released in a sustained manner over several weeks and that cell viability was maintained in the hydrogel over 21 days. qRT-PCR demonstrated the upregulation of bone markers such as osteopontin, osteocalcin and collagen 1A1 at day 3 and 14 in the constructs loaded with BMP2. In vivo assessment of the biphasic scaffold was performed using a dose of 30 µg of BMP-2 in a rabbit calvarial vertical bone augmentation model. The histology and micro-CT analysis of the elevated space demonstrated that the hydrogel and the presence of BMP-2 enabled bone formation. However, this was limited to the immediate vicinity of the calvarial bone. The amount of newly formed bone was relatively small which was likely due to poor vascularisation of the extraskeletal space. The utilisation of this biomimetic biphasic construct with excellent space maintenance properties can be of interest in dentistry although the in vivo model requires refinement to demonstrated appropriate efficacy.

Titania nanopores with dual micro-/nano-topography for selective cellular bioactivity.

This letter describes a simple surface modification strategy based on a single-step electrochemical anodization towards generating dual micro- and nano-rough horizontally-aligned TiO2 nanopores on the surface of clinically utilized micro-grooved titanium implants. Primary macrophages, osteoblasts and fibroblasts were cultured on the nano-engineered implants, and it was demonstrated that the modified surfaces selectively reduced the proliferation of macrophages (immunomodulation), while augmenting the activity of osteoblasts (osseo-integration) and fibroblasts (soft-tissue integration). Additionally, the mechanically robust nanopores also stimulated osteoblast and fibroblast adhesion, attachment and alignment along the direction of the pores/grooves, while macrophages remained oval-shaped and sparsely distributed. This study for the first time reports the use of cost-effectively prepared nano-engineered titanium surface via anodization, with aligned multi-scale micro/nano features for selective cellular bioactivity, without the use of any therapeutics.

Combining electrospinning and cell sheet technology for the development of a multiscale tissue engineered ligament construct (TELC).

Ligament tissue rupture is a common sport injury. Although current treatment modalities can achieve appropriate reconstruction of the damaged ligament, they present significant drawbacks, mostly related to reduced tissue availability and pain associated with tissue harvesting. Stem cell based tissue regeneration combined with electrospun scaffolds represents a novel treatment method for torn ligaments. In this study, a low fiber density polycaprolactone (PCL) electrospun mesh and sheep mesenchymal stem cells (sMSCs) were used to develop tissue engineered ligament construct (TELC) in vitro. The assembly of the TELC was based on the spontaneous capacity of the cells to organize themselves into a cell sheet once seeded onto the electrospun mesh. The cell sheet matured over 4 weeks and strongly integrated with the low fiber density electrospun mesh which was subsequently processed into a ligament-like bundle and braided with two other bundles to develop the final construct. Live/dead assay revealed that the handling of the construct through the various phases of assembly did not cause significant difference in viability compared to the control. Mechanical evaluation demonstrated that the incorporation of the cell sheet into the braided construct resulted in significantly modifying the mechanical behavior. A stress/displacement J-curve was observed for the TELC that was similar to native ligament, whereas this particular feature was not observed in the non-cellularized specimens. The regenerative potential of the TELC was evaluated ectopically in immunocompromized rats, compared to non cellularized electrospun fiber mesh and this demonstrated that the TELC was well colonized by host cells and that a significant remodelling of the implanted construct was observed. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 399-409, 2018.

Antimicrobial drugs encapsulated in fibrin nanoparticles for treating microbial infested wounds.

PURPOSE: In vitro evaluation of antibacterial and antifungal drugs encapsulated fibrin nanoparticles to prove their potential prospect of using these nanocomponent for effective treatment of microbial infested wounds. METHODS: Surfactant-free oil-in-water emulsification-diffusion method was adopted to encapsulate 1 mg/ml each of antimicrobial drugs (Ciprofloxacin and Fluconazole) in 4 ml of aqueous fibrinogen suspension and subsequent thrombin mediated cross linking to synthesize drug loaded fibrin nanoparticles. RESULTS: Ciprofloxacin loaded fibrin nanoparticles (CFNPs) showed size range of 253 ± 6 nm whereas that of Fluconazole loaded fibrin nanoparticles (FFNPs) was 260 ± 10 nm. Physico chemical characterizations revealed the firm integration of antimicrobial drugs within fibrin nanoparticles. Drug release studies performed at physiological pH 7.4 showed a release of 16% ciprofloxacin and 8% of fluconazole while as the release of ciprofloxacin at alkaline pH 8.5, was 48% and that of fluconazole was 37%. The antimicrobial activity evaluations of both drug loaded systems independently showed good antibacterial activity against Escherichia coli (E.coli), Staphylococcus aureus (S. aureus) and antifungal activity against Candida albicans (C. albicans). The in vitro toxicity of the prepared drug loaded nanoparticles were further analyzed using Human dermal fibroblast cells (HDF) and showed adequate cell viability. CONCLUSION: The efficacies of both CFNPs and FFNPs for sustained delivery of encapsulated anti microbial drugs were evaluated in vitro suggesting its potential use for treating microbial infested wounds (diabetic foot ulcer).

Biochemical properties of Hemigraphis alternata incorporated chitosan hydrogel scaffold.

In this work, Hemigraphis alternata extract incorporated chitosan scaffold was synthesized and characterized for wound healing. The antibacterial activity of Hemigraphis incorporated chitosan scaffold (HIC) against Escherichia coli and Staphylococcus aureus was evaluated which showed a reduction in total colony forming units by 45-folds toward E. coli and 25-fold against S. aureus respectively. Cell viability studies using Human Dermal Fibroblast cells (HDF) showed 90% viability even at 48 h when compared to the chitosan control. The herbal scaffold made from chitosan was highly haemostatic and antibacterial. The obtained results were in support that the herbal scaffold can be effectively applied for infectious wounds.

In vitro and in vivo evaluation of microporous chitosan hydrogel/nanofibrin composite bandage for skin tissue regeneration.

In this work, we have developed chitosan hydrogel/nanofibrin composite bandages (CFBs) and characterized using Fourier transform-infrared spectroscopy and scanning electron microscopy. The homogeneous distribution of nanofibrin in the prepared chitosan hydrogel matrix was confirmed by phosphotungstic acid-hematoxylin staining. The mechanical strength, swelling, biodegradation, porosity, whole-blood clotting, and platelet activation studies were carried out. In addition, the cell viability, cell attachment, and infiltration of the prepared CFBs were evaluated using human umbilical vein endothelial cells (HUVECs) and human dermal fibroblast (HDF) cells. It was found that the CFBs were microporous, flexible, biodegradable, and showed enhanced blood clotting and platelet activity compared to the one without nanofibrin. The prepared CFBs were capable of absorbing fluid and this was confirmed when immersed in phosphate buffered saline. Cell viability studies on HUVECs and HDF cells proved the nontoxic nature of the CFBs. Cell attachment and infiltration studies showed that the cells were found attached and proliferated on the CFBs. In vivo experiments were carried out in Sprague-Dawley rats and found that the wound healing occurred within 2 weeks when treated with CFBs than compared to the bare wound and wound treated with Kaltostat. The deposition of collagen was found to be more on CFB-treated wounds compared to the control. The above results proved the use of these CFBs as an ideal candidate for skin tissue regeneration and wound healing.

Fabrication of chitin-chitosan/nano ZrO(2) composite scaffolds for tissue engineering applications.

The urge to repair and regenerate natural tissues can now be satisfactorily fulfilled by various tissue engineering approaches. Chitin and chitosan are the most widely accepted biodegradable and biocompatible materials subsequent to cellulose. The incorporation of nano ZrO(2) onto the chitin-chitosan scaffold is thought to enhance osteogenesis. Hence a nanocomposite scaffold was fabricated by lyophilization technique using chitin-chitosan with nano ZrO(2). The prepared nanocomposite scaffolds were characterized using SEM, FTIR, XRD and TGA. In addition, the swelling, degradation, biomineralization, cell viability and cell attachment of the composite scaffolds were also evaluated. The results demonstrated better swelling and controlled degradation in comparison to the control scaffold. Cell viability studies proved the non toxic nature of the nanocomposite scaffolds. Cells were found to be attached to the pore walls and spread uniformly throughout the scaffolds. All these results suggested that the developed nanocomposite scaffolds possess the prerequisites for tissue engineering scaffolds and could be used for various tissue engineering applications.

Biomaterials based on chitin and chitosan in wound dressing applications.

Wound dressing is one of the most promising medical applications for chitin and chitosan. The adhesive nature of chitin and chitosan, together with their antifungal and bactericidal character, and their permeability to oxygen, is a very important property associated with the treatment of wounds and burns. Different derivatives of chitin and chitosan have been prepared for this purpose in the form of hydrogels, fibers, membranes, scaffolds and sponges. The purpose of this review is to take a closer look on the wound dressing applications of biomaterials based on chitin, chitosan and their derivatives in various forms in detail.

Development of novel chitin/nanosilver composite scaffolds for wound dressing applications.

Antibiotic resistance of microorganisms is one of the major problems faced in the field of wound care and management resulting in complications like infection and delayed wound healing. Currently a lot of research is focused on developing newer antimicrobials to treat wounds infected with antibiotic resistant microorganisms. Silver has been used as an antimicrobial agent for a long time in the form of metallic silver and silver sulfadiazine ointments. Recently silver nanoparticles have come up as a potent antimicrobial agent and are finding diverse medical applications ranging from silver based dressings to silver coated medical devices. Chitin is a natural biopolymer with properties like biocompatibility and biodegradability. It is widely used as a scaffold for tissue engineering applications. In this work, we developed and characterized novel chitin/nanosilver composite scaffolds for wound healing applications. The antibacterial, blood clotting and cytotoxicity of the prepared composite scaffolds were also studied. These chitin/nanosilver composite scaffolds were found to be bactericidal against S. aureus and E. coli and good blood clotting ability. These results suggested that these chitin/nanosilver composite scaffolds could be used for wound healing applications.

Novel chitin/nanosilica composite scaffolds for bone tissue engineering applications.

Biopolymers like chitin are widely investigated as scaffolds in bone tissue engineering. Its properties like biocompatibility, biodegradability, non-toxicity, wound healing ability, antibacterial activity, hemostatic property, etc., are widely known. However, these materials are not much bioactive. Addition of material like silica can improve the bioactivity and biocompatibility of chitin. In this work, chitin composite scaffolds containing nanosilica were prepared using chitin hydrogel and their bioactivity, swelling ability and cytotoxicity was analyzed in vitro. These scaffolds were found to be bioactive in simulated body fluid (SBF) and biocompatible when tested with MG 63 cell line. These results suggest that chitin/nanosilica composite scaffolds can be useful for bone tissue engineering applications.

Bioactive and metal uptake studies of carboxymethyl chitosan-graft-D-glucuronic acid membranes for tissue engineering and environmental applications.

Carboxymethyl chitosan-graft-D-glucuronic acid (CMCS-g-D-GA) was prepared by grafting D-GA onto CMCS in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and then the membranes were made from it. In this work, the bioactivity studies of CMCS-g-D-GA membranes were carried out and then characterized by SEM, CLSM, XRD and FT-IR. The CMCS-g-D-GA membranes were found to be bioactive. The adsorption of Ni2+, Zn2+ and Cu2+ ions onto CMCS-g-D-GA membranes has also been investigated. The maximum adsorption capacity of CMCS-g-D-GA for Ni2+, Zn2+ and Cu2+ was found to be 57, 56.4 and 70.2 mg/g, respectively. Hence, these membranes were useful for tissue engineering, environmental and water purification applications.