Emulsion Templated Scaffolds that Include Gelatin and Glycosaminoglycans

Abstract

Gelatin is one of the most commonly used biopolymer for creating cellular scaffolds due to its innocuous nature. To create stable gelatin scaffolds at physiological temperature (37 degrees C), chemical cross-linking is a necessary step. In a previous paper (Biomacromolecules 2006, 7, 3059-3068), cross-linking was carried out by either radical polymerization of the methacrylated derivative of gelatin (GMA) or through the formation of isopeptide bonds catalyzed by transglutaminase. The method of scaffold production was based on emulsion templating in which an organic phase is dispersed in the form of discrete droplets into a continuous aqueous solution of the biopolymer. Both kinds of scaffolds were tested as culture medium for hepatocytes. It turned out that the enzymatic cross-linked scaffold performed superiorily in this respect, even though it was mechanically less stable than the GMA scaffold. In the present paper, in an attempt to improve the biocompatibility of the GMA-based scaffold, biopolymers present in the extracellular matrix (ECM) were included in scaffold formulation, namely, chondroitin sulfate and hyaluronic acid. These biopolymers were derivatized with methacrylic moieties to undergo radical polymerization together with GMA. The morphology of the scaffolds was tuned to some extent by varying the volume fraction of the internal phase and to a larger extent by inducing a controlled destabilization of the precursor emulsion through the use of additives. In this way, scaffolds with 44% of the void volume attributable to voids with a diameter exceeding 60 microm and with 79% of the interconnect area attributable to interconnects with a diameter exceeding 20 microm in diameter could be successfully synthesized. To test whether the inclusion of ECM components into scaffold formulation resolves in an improvement of their biocompatibility with respect to GMA scaffolds, hepatocytes were seeded on both kinds of scaffolds and cell viability and function assays were carried out and compared.

Degradable emulsion-templated scaffolds for tissue engineering from thiol–ene photopolymerisation

“…This imparts (bio)degradability to these materials and opens up the prospect of their use as scaffolds for tissue engineering. Emulsion-templated scaffolds have previously been explored as scaffolds for tissue engineering [26][27][28][33][34][35][36][37][38][39][40][41] , however in almost all cases the materials used contain significant amounts of non-degradable carbon backbone polymer chains, potentially limiting their clinical applicability (the exception are enzymatically crosslinked gelatin scaffolds developed by Barbetta et al 28 ). In addition, non-degradable styrene-based polyHIPEs have been used extensively for in vitro 3D cell culture [42][43][44][45] …”

Enzymatic Polymer Modification

“…Besides crosslinking, transglutaminases have been employed for grafting/coating of wool fabrics with silk sericin or keratin leading to increased bursting strength and softness and reduced felting shrinkage [17,18] . In biomedical applications, transglutaminases have been used for tissue engineering [19,20] or for the production of melt -extruded guides for peripheral nerve repair [21] .…”

Mimicking the quasi-random assembly of protein fibers in the dermis by freeze-drying method

“…Commonly used techniques are: particulate leaching [8], emulsion templating [9,10], electro spinning [11], rapid prototyping [12], phase separation [13][14][15], and mostly freeze-drying [1,[16][17][18][19][20].…”

“…In this method, aqueous solutions are often used to fabricate scaffolds. When compared to the other methods [8][9][10][13][14][15], the freeze-drying process does not bring any impurities into the samples and a further purifying process is therefore not necessary. The low temperature of the freeze-drying process helps maintain the activity of biomacromolecules and pharmaceuticals [21].…”