Lyophilized Polyvinyl Alcohol and Chitosan Scaffolds Pre-Loaded with Silicon Dioxide Nanoparticles for Tissue Regeneration

Materials with a soft tissue regenerative capacity can be produced using biopolymer scaffolds and nanomaterials, which allow injured tissue to recover without any side effects or limitations. Four formulations were prepared using polyvinyl alcohol (PVA) and chitosan (CS), with silicon dioxide nanoparticles (NPs-SiO2) incorporated using the freeze-drying method at a temperature of -50 °C. TGA and DSC showed no change in thermal degradation, with glass transition temperatures around 74 °C and 77 °C. The interactions between the hydroxyl groups of PVA and CS remained stable. Scanning electron microscopy (SEM) indicated that the incorporation of NPs-SiO2 complemented the freeze-drying process, enabling the dispersion of the components on the polymeric matrix and obtaining structures with a small pore size (between 30 and 60 μm) and large pores (between 100 and 160 μm). The antimicrobial capacity analysis of Gram-positive and Gram-negative bacteria revealed that the scaffolds inhibited around 99% of K. pneumoniae, E. cloacae, and S. aureus ATCC 55804. The subdermal implantation analysis demonstrated tissue growth and proliferation, with good biocompatibility, promoting the healing process for tissue restoration through the simultaneous degradation and formation of type I collagen fibers. All the results presented expand the boundaries in tissue engineering and regenerative medicine by highlighting the crucial role of nanoparticles in optimizing scaffold properties.

Novel Chitosan-Silica Hybrid Hydrogels for Cell Encapsulation and Drug Delivery

Hydrogels constructed from naturally derived polymers provide an aqueous environment that encourages cell growth, however, mechanical properties are poor and degradation can be difficult to predict. Whilst, synthetic hydrogels exhibit some improved mechanical properties, these materials lack biochemical cues for cells growing and have limited biodegradation. To produce hydrogels that support 3D cell cultures to form tissue mimics, materials must exhibit appropriate biological and mechanical properties. In this study, novel organic-inorganic hybrid hydrogels based on chitosan and silica were prepared using the sol-gel technique. The chemical, physical and biological properties of the hydrogels were assessed. Statistical analysis was performed using One-Way ANOVAs and independent-sample t-tests. Fourier transform infrared spectroscopy showed characteristic absorption bands including amide II, Si-O and Si-O-Si confirming formation of hybrid networks. Oscillatory rheometry was used to characterise the sol to gel transition and viscoelastic behaviour of hydrogels. Furthermore, in vitro degradation revealed both chitosan and silica were released over 21 days. The hydrogels exhibited high loading efficiency as total protein loading was released in a week. There were significant differences between TC2G and C2G at all-time points (p < 0.05). The viability of osteoblasts seeded on, and encapsulated within, the hydrogels was >70% over 168 h culture and antimicrobial activity was demonstrated against Pseudomonas aeruginosa and Enterococcus faecalis. The hydrogels developed here offer alternatives for biopolymer hydrogels for biomedical use, including for application in drug/cell delivery and for bone tissue engineering.

Injectable chitosan/gelatin/bioactive glass nanocomposite hydrogels for potential bone regeneration: In vitro and in vivo analyses

The present work describes in vitro and in vivo behaviors of thermosensitive composite hydrogels based on polymers/bioactive glass nanoparticles. Assays in SBF (simulated body fluid) solution showed that loss of hydrogel mass in vitro was decreased by 4.3% when bioactive glass nanoparticles (nBG) were incorporated, and confirmed the bioactivity of nBG containing hydrogels. In vitro assays demonstrated the cytocompatibility of the hydrogels with encapsulated rat bone marrow mesenchymal stem cells (BMSC). Crystal violet assays showed a 27% increase in cell viability when these cells were seeded in hydrogels containing nBG. In vivo biocompatibility was examined by injecting hydrogels into the dorsum of Swiss rats. The results indicated that the prepared hydrogels were nontoxic upon subcutaneous injection, and could be candidates for a safe in situ gel-forming system. Injection of the hydrogels into a rat tibial defect allowed preliminary evaluation of the hydrogels' regenerative potential. Micro Computed Tomography analysis suggested that more new tissue was formed in the defects treated with the hydrogels. Taken together, our data suggest that the developed injectable composite hydrogels possess properties which make them suitable candidates for use as temporary injectable matrices for bone regeneration.