3D Scaffolds Fabrication via Bicomponent Microgels Assembly: Process Optimization and In Vitro Characterization

Abstract

In the last decade, different technological approaches have been proposed for the fabrication of 3D models suitable to evaluate in vitro cell response. Among them, electro fluid dynamic atomization (EFDA) belonging to the family of electro-assisted technologies allows for the dropping of polysaccharides and/or proteins solutions to produce micro-scaled hydrogels or microgels with the peculiar features of hydrogel-like materials (i.e., biocompatibility, wettability, swelling). In this work, a method to fabricate 3D scaffolds by the assembly of bicomponent microgels made of sodium alginate and gelatin was proposed. As first step, optical and scanning electron microscopy with the support of image analysis enabled to explore the basic properties of single blocks in terms of correlation between particle morphology and process parameters (i.e., voltage, flow rate, electrode gap, and needle diameter). Chemical analysis via ninhydrin essays and FTIR analysis confirmed the presence of gelatin, mostly retained by physical interactions into the alginate network mediated by electrostatic forces. In vitro tests confirmed the effect of biochemical signals exerted by the protein on the biological response of hMSCs cultured onto the microgels surface. Hence, it is concluded that alginate/gelatin microgels assemblies can efficiently work as 3D scaffolds able to support in vitro cells functions, thus providing a friendly microenvironment to investigate in vitro cell interactions.

Keywords: alginate; biocompatibility; gelatin; hMSC; scaffolds.

Figure 1

Schematic representation of the preparation 3D scaffolds via EFDA/freeze drying.

Figure 2

Optical images of (a) Alg and (b) Alg/Gel microgels (Scale bar: 500 µm) and relative diameter distribution (c,d).

Figure 3

SEM images of (a) Alg and (b) Alg/Gel microgels (scale bar: 300 µm). (c) Ninhydrin staining test to detect the presence of gelatin into the bicomponent microgels.

Figure 4

ATR-FTIR spectrum of (a) Alg and (b) Alg/Gel microgels.

Figure 5

In vitro tests on Alg and Alg/Gel assembled scaffolds: (a) Adhesion and (b) proliferation (statistical difference * p < 0.05, ** p < 0.01, *** p < 0.001 respect to the control (TCP); ^## p < 0.01 statistical difference between Alg and Alg/Gel); (c) cell viability fold increase in time.