Resorbable and biocompatible scaffolds made of a bacterial biopolymer

NYGAARD, D.; BERTUOLA M.; YASHCHUK, O.; HERMIDA É.B.

Dresden

Congreso; 7th International Conference on Cellular Materials - Cellmat 2022; 2022

German Materials Society (DGM)

3D printing allows to build scaffolds for tissue regeneration with controlled porosity. By adjusting thepercentage and pattern of infill, and the printing velocity, scaffolds can be manufactured with the porositythat mimics the extracellular matrix (ECM) of each type of tissue (bone, cartilage, skin, etc.). The elasticmodulus of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a biodegradable polymer produced bymicroorganisms, make it suitable to resemble the ECM of cartilage and bone. In fact, the excellent combinationof its attributes: thermoplastic, resorbable and biocompatible, encourages 3D printing of PHBV-products forbiomedical applications. Fused deposition modeling with PHBV filaments has the drawback of the narrowworking window between the melting point (160°C) and the thermal decomposition temperature ( 220°C).Thus, the aim of this work is to formulate a viscous ink made of PHBV that allows to build scaffolds using abioprinter.The PHBV-ink was obtained by dissolving PHBV in chloroform(12.7% m/v) at 70°C and slowly cooled to room temperature; theink was poured into one of the two cartridges of the bioprinter LifeSi3D Res (Argentina) (Fig 1A). Printing was performed at roomtemperature using a 514um blunt-tipped 21G needle. A single layermodel with square pores was generated with 10% of infill (.gcode)generating porous scaffold (porous dimension of 2mm x 2mm).The printed layer, shown in Fig. 1B, has filaments of 648±7umthickness and 22±5um height. The printing fidelity (Pr) of the inkwas calculated as Pr=L2 /(16*A), where L = 2mm and A are the lengthand area of the pores, respectively. Fig 1C remarks the well-definedsquare shape of the pores, with Pr= (0.9845±0.0025). Regarding the PHBV production, it was performed by Cupriavidus necator in culture medium with residualglycerol (35g/l) and propionic acid (1g/l) as carbon sources. Bacterial cells were observed at 72h by optical,scanning electron and transmission microscopies (Fig. 1). The production of bacterial cells and biopolymerswas quantified by gravimetry and UV spectrophotometry. Then, the produced polymer was extracted fromthe lyophilized bacterial cells with hot chloroform, purified in two steps with methanol and hexane at 4°C, andcharacterized by H1 and C13 NMR. Kinetic measurement of the production process established the maximumvalue of 3.4g/l PHBV copolymer at 72 h, corresponding to 63% of the cell dry weight, with a hydroxyvaleratemonomer molar fraction of 7.6%.