Facile synthesis of nano-composite double network hybrid hydrogels via UV polymerisation for cartilage tissue engineering applications, with functionalised silica nanoparticles as macro-crosslinkers

摘要

Introduction: Hydrogels are a highly versatile material for tissue engineering applications, but are limited in their use due to the inherently weak mechanical properties they exhibit. Control over their swelling and mechanical strengths, as well as then drugloading ability can bring about many uses in regenerative medicine. Here, a simple and fast method to prepare two different hybrid hydrogels with nanocomposite structures has been developed, using UV polymerisation, silica nanoparticles and glucose oxidase (GOx). These gels are made using a 2 step sequential technique, where the first network consisting of a polyelectrolyte polymer is prepared followed by a second network neutral polymer. This creates a synergetic effect of both polymers ranther than a linear effect to their mechanical properties. SNP functionality in these gels are important as macro-crosslinkers and also for potential ion or drug loading to assist in combating diseases when placed in vivo, such as osteoarthritis. The assessment of SNP size and concentration will conclude if smaller or larger particles are more efficient at providing mechanical stability and strength. Materials and Methods: SNPs are synthesised to 50,100,150 nm then functionalised using APTES and VTEOS to get vinyl-SNPs and amine-SNPs. The first hydrogel is synthesised by preparing a monomer solution of 2-acrylamido-2-methylpropane sulfonic acid (PAMPS) with GOx to prevent oxygen inhibition and v-SNP for macro-crosslinking, and exposed to UV (365nm) for photo polymerization, once gelled it is then swollen in a monomer solution of acrylamide monomers and GOx before being UV polymerised. Finally, a gel is formed, labelled DNHG1. DNHG2 follows a similar synthesis route but in the first step EDC chemistry is applied to crosslink the a-SNPS (in MES buffer) to the poly acrylic acid. Results and Discussion: Successful synthesis of both gels using the described method have been repeated to get indicative results. Two controls per gel were made; control without SNPs, and control without SNPs and GOx. Mechanical strengths and swelling abilities change drastically in the presence SNP and GOx for these gels. Characterisation techniques such as TGA, mercury porosimetry, SEM, UV-VIS show that particle retention is high in the gels (above 66% after purification in water for 3 weeks) and pore interconnect sizes range from 5-100 micrometers. Mechanical strengths reach up to 2 MPa compared to controls 0.05MPa. Smaller nanoparticles prove to give the best results and best retention meaning their higher surface area is favoured for crosslinking. Images provided show the PAMPS/PAAm hydrogel exhibiting 75% strain with 40wt% V-SNP. Figure attached shows PAAc/PAAm mechanical strengths at different A-SNP concentrations. Conclusion: A tailorable material has been developed using silica nanoparticles as macro-crosslinkers. The benefit of this material is it ability to control the mechanical strength and swelling ability. GOx is a key component, preventing oxygen inhibition in the polymerisation step for higher conversion of monomers leading to stronger mechanical properties matching articular cartilage. This opens up the door to open vessel photo polymerisation and the facile preparation of synthetic hydrogels for tissue engineering.