Electrospun cotton\u2013wool-like silica/gelatin hybrids with covalent coupling

Maria Nelson,Akiko Obata,Toshihiro Kasuga,Julian R Jones,Francesca Tallia,Samuel J Page,Yuki Fujita,John V Hanna

doi:10.1007/s10971-020-05420-x

Abstract

Inorganic/organic sol–gel hybrids consist of co-networks of inorganic and organic components that can lead to unique properties, compared to conventional composites, especially when there is covalent bonding between the networks. The aim here was to develop new electrospun silica/gelatin sol–gel hybrids, with covalent coupling and unique 3D cotton–wool-like morphology for application as regenerative medicine scaffolds. Covalent coupling is critical for obtaining sustained dissolution of the fibres and we identified the sol–gel synthesis conditions needed for coupling within the electrospun fibres. Under carefully controlled conditions, such as constant humidity, we investigated the effect of the electrospinning process variables of sol viscosity (and aging time) and amount of coupling agent on the 3D morphology of the fibres, their structure (bonding) and dissolution, identifying a detailed optimised protocol for fibre scaffold production.

Highlights

Inorganic/organic sol–gel hybrids are being applied to regenerative medicine strategies as traditional materials have not been able to fulfil all the design requirements of scaffolds [1]
The criteria are that the scaffold should: be biocompatible; provide a temporary 3D template for cell migration and production of new tissue, without the formation of fibrous encapsulation; match the mechanical properties and mimic the environment of the host tissue; biodegrade at a controlled rate as the tissue regrows; be sterilisable and be able to be manufactured to Good Manufacturing Practice (GMP) [1]
The organic polymer is usually functionalised with the coupling agent before it is introduced to the sol, e.g., a polymer containing nucleophilic groups, such as carboxylic acid groups, can be functionalised with glycidoxypropyl trimethoxysilane (GPTMS) as the nucleophilic groups open the epoxy ring [14]

Summary

Introduction

Inorganic/organic sol–gel hybrids are being applied to regenerative medicine strategies as traditional materials have not been able to fulfil all the design requirements of scaffolds [1]. Conventional composites can have controlled stiffness and elastomeric properties [8], but when glass or ceramic particles are dispersed within a polymer matrix, they can be masked by the polymer. Sol–gel hybrids, made by adding an organic polymer into the sol before it gels, have the potential to overcome these problems due to the molecular scale interactions between the inorganic and organic components, which translate to controlled degradation rate. The functionalised polymer has side chains with alkoysilane groups and it is added to the sol–gel process, forming covalent bonds between Si-OH bonds from the hydrolysed coupling agent and the silica network in the sol, forming a class-II hybrid [15]. Gelatin has high potential in silica/gelatin hybrid materials [16,17,18], as it is an analogue of collagen, making it a mimic of the composition of natural extracellular matrix. Other crosslinking agents for gelatin include genipin [19] and gluteraldahyde [20] but they do not bond to the silica network

Methods

Results

Conclusion