Silica–gelatin hybrids for tissue regeneration: inter-relationships between the process variables

Abstract

Owing to their diverse range of highly tailorable material properties, inorganic/organic hybrids have the potential to meet the needs of biodegradable porous scaffolds across a range of tissue engineering applications. One such hybrid platform, the silica-gelatin sol-gel system, was examined and developed in this study. These hybrid scaffolds exhibit covalently linked interpenetrating networks of organic and inorganic components, which allows for independent control over their mechanical and degradation properties. A combination of the sol-gel foaming process and freeze drying was used to create an interconnected pore network. The synthesis and processing of the scaffolds has many variables that affect their structure and properties. The focus of this study was to develop a matrix tool that shows the inter-relationship between process variables by correlating the key hybrid material properties with the synthesis parameters that govern them. This was achieved by investigating the effect of the organic (gelatin) molecular weight and collating previously reported data.Control of molecular weight of the polymer is as an avenue that allows the modification of hybrid material properties without changing the surface chemistry of the material, which is a factor that governs the cell and tissue interaction with the scaffold. This presents a significant step forward in understanding the complete potential of the silica-gelatin hybrid system as a medical device.

Functionalizing natural polymers with alkoxysilane coupling agents: reacting 3-glycidoxypropyl trimethoxysilane with poly(γ-glutamic acid) and gelatin

“…They have been applied to a wide range of applications including protective surfaces 1, 2 , optical coatings 1, 2 , separation membranes 3,4 , drug delivery 5 , wound healing 6 and degradable tissue engineering scaffolds [7][8][9][10][11][12] .…”

“…Introducing covalent bonding between the components and adjusting the degree of bonding enables the tailorability of properties such as degradation rate, stiffness, hardness and mechanical strength 10,11 , widening the potential applications of hybrids. However, characterization of the bonding reaction is difficult, preventing fine control and design of hybrid synthesis 16 .…”

“…The silanol groups may originate exclusively from the functional alkoxysilane itself or an additional silica precursor may be introduced, such as hydrolysed tetraethyl orthosilicate (TEOS) 10,11,17,18 .…”

“…a sol of hydrolysed TEOS, and fabricated into three dimensional (3-D) porous scaffolds using techniques such as electrospinning 34 , foaming or freeze-drying 9,11,12,[35][36][37][38] . Hybrid scaffolds can be tailored to exhibit mechanical and degradation properties suitable for their applications 10,11 and they have shown promising results in vitro with regards to attachment and proliferation of mesenchymal stem cells 10 , osteoblast-like 39 and osteosarcoma cells 18,19 . In vivo, chitosan-silica hybrid scaffolds showed good cytocompatibility when implanted subcutaneously and improved tissue regeneration of crushed spinal nerve in a rat model 7 .…”

Hybrid sol–gel inorganic/gelatin porous fibres via solution blow spinning

“…Sol-gel derived bioactive glasses can be produced at low temperatures and formed into monolithic scaffolds in situ by direct foaming [24][25][26][27], freeze-casting [28][29][30], and even fibrous structures via electrospinning and air-spraying (a process analogous to SBS) [31,32]. Notably, bioactive glasses with compositions that contain calcium and phosphate exhibit more bioactivity than pure silica based glasses [33,34].…”