3D printing of hydrogel inks containing PHBV microparticles

EVELINA PACHECO; MERCEDES PERÉZ-RECALDE; BEATRIZ ARAOZ; ÉLIDA B. HERMIDA

Congreso; Cellmat 2022; 2022

3D printing has widely increased the development of cellular materials that emulate the extracellular matrix of different tissues [1]. Inks for 3D printing must fulfill certain biological and mechanical requirements: to be biocompatible and biodegradable, to have a shear-thinning behavior, to show at least 0,90 of printability, and to give scaffolds with similar mechanical properties to the tissue to be replaced. Furthermore, the addition of a drug delivery systems (DDS) to a scaffold is under development, seeking potential applications in pharmacology [2]. In this work, a sodium alginate-gelatin hydrogel with poly (hydroxybutyrate-co-hydroxyvalerate) (PHBV) microparticles was employed to produce 3D printed scaffolds. The hydrogel was a blend made of 9% sodium alginate and 4.5% gelatin; its liquid-like behavior led to a poor printability (Pr=0.81). This value could be improved to 0,94 by the addition 15 mM of CaCl2. This ink, called Ink-Ca, was filled with PHBV spherical microparticles (MP) from 5 mg to 100 mg every 10 ml of ink. The MP were prepared by an emulsification/solvent technique [3]; their mean size, determined by microscopy, was 14+6 µm. Interestingly, the viscosity of the ink filled with MP decreased as the concentration increases: 1498, 1178 and 840 Pa.s for 0, 30 and 100 mg of MP/10 mL of ink. Samples made of the Ink-Ca loaded with MP (5 mg, 15 mg, 30 mg, 50 mg and 100 mg) and crosslinked with CaCl2 0,5 M for 3 h at 25°C and overnight at 4°C showed an increase in the compression modulus from 400 kPa (without MP) to 550 kPa with 30 mg of MP. Higher concentrations of MP particles did not increase the compression modulus. Thus, 30 mg MP/10 mL enhances the compression modulus and higher concentrations could be suitable for drug delivery without loss in the mechanical behavior. When evaluated for 3D-printing, Ink-Ca/30 mg MP presented the same (Pr=0,94) that the Ink-Ca. We manufactured scaffolds with infill 30% and 8 layers, by 3D printing, with the Ink-Ca and Ink-Ca/30 mg MP, to compare mechanical properties. These scaffolds were also crosslinked overnight with CaCl2 0,5M. In this case, again, the sample with MP increased the compression modulus (Ink-Ca 172±30 kPa, Ink-Ca/30 mg MP 270±30 kPa). The results suggest that microparticles with alginate-gelatin hydrogel can be combined giving inks accurate for the application in 3D printing, and the microparticles produce changes in the microstructure both in ink form and in the scaffold form. 30 mg MP in this system is highlighted for DDS application for soft tissues.