Interpenetrating Alginate-Collagen Polymer Network Microspheres for Modular Tissue Engineering

Abstract

The lack of vascularization limits the creation of engineered tissue constructs with clinically relevant sizes. We pioneered a bottom-up process (modular tissue engineering) in which constructs with intrinsic vasculature were assembled from endothelialized building blocks. In this study, we prepared an interpenetrating polymer network (IPN) hydrogel from a collagenalginate blend and evaluated its use as microspheres in modular tissue engineering. Ionotropic gelation of alginate was combined with collagen fibrillogenesis, and the resulting hydrogel was stiffer and had greater resistance to enzymatic degradation relative to that of collagen alone; the viability of embedded mesenchymal stromal cells (adMSC) was unaltered. IPN microspheres were fabricated by a coaxial air-flow technique, and an additional step of collagen coating was required to have human umbilical vein endothelial cells (HUVEC) attach and proliferate. When implanted subcutaneously in SCID/bg mice, adMSC-HUVEC microspheres promoted more blood vessels at day 7 relative to microspheres without adMSC but coated with HUVEC. Perfusion studies confirmed that these vessels were connected to the host vasculature. Fewer vessels were detected in both groups at day 21, but in adMSC-HUVEC explants, more smooth muscle cells had wrapped around vessels, and CLARITY processing of whole explants revealed a restricted leakage of blood. The capacity for rapid gelation and high throughput production are promising features for the use of these microspheres in modular tissue engineering.

Tunable Fibrin-Alginate Interpenetrating Network Hydrogels to Guide Cell Behavior

“…IPN hydrogels offer a strategy to achieve a preferred embodiment of biomaterial by decoupling function from composition [21]. Thus, IPNs have been formed from a number of materials including collagen-alginate [10], fibrin-alginate [12], and fibrin-hyaluronic acid [22]. However, formulations utilizing matricellular proteins such as collagen rely on the concentration of the polymer to drive mechanical and structural properties, while formulations using fibrin require one-step protocols for rapid crosslinking and gelation.…”

“…Among polymers used in IPNs, alginate is commonly studied due to its tunable, robust mechanical properties. IPNs have been formed by combining collagen-alginate [9,10], basement membrane-alginate [11], fibrin-alginate [12], and others. Previous studies have confirmed the potential to combine two polymers and modulate both adhesion and mechanical characteristics in hydrogel constructs.…”

Hipster microcarriers: exploring geometrical and topographical cues of non-spherical microcarriers in biomedical applications

“…This strategy aimed to produce a pre-vascularised network that could anastomose upon implantation. 218 Ultimately, bottom-up strategies can be used to interweave a pre-vascularised network between cellseeded micrometric structures in a precise manner, something which would not be possible with top-down strategies. 219 Due to the micrometric nature of units applied for bottomup strategies and their proximity in size to cell dimensions, this unlocks several opportunities to tailor and guide cell response via biophysical signals such as geometrical, mechanical, and topographical cues.…”

Solvent-free preparation of uniform styrene/maleimide copolymer microspheres from solid poly(styrene-alt-maleic anhydride) microspheres

“…Polymer microspheres are a class of micro or nano scale materials which have been widely used in various fields such as enzyme/drug/catalystsupports, [1][2][3][4] water treatment, 5 chromatography, 6 tissue engineering 7 and composite materials. 8 Among these polymer microspheres, the poly(styrene-altmaleic anhydride) (SMA) microsphere has attracted intensive attention due to its excellent heat resistance as well as the high reactivity of its maleic anhydride group, 9,10 which provides the possibility for further modification including esterification, 11 hydrolysis, 12 amination, 13 imidization, 14 etc.…”