Alginate-chitosan core-shell microcapsule cultures of hepatic cells in a small scale stirred bioreactor: impact of shear forces and microcapsule core composition

Abstract

A small scale stirred bioreactor was designed and the effect of different agitation rates (30, 60 and 100 rpm) was investigated on HepG2 cells cultured in alginate-chitosan (AC) core-shell microcapsule in terms of the cell proliferation and liver-specific function. The microencapsulated hepatic cells could proliferate well when they were cultured for 10 days at 30 rpm while the cell-laden microcapsules showed no cell proliferation at 100 rpm in the bioreactor system. Albumin production rate, as an important liver function, increased also 1.8- and 1.5- fold under stirring rate of 30 rpm compared to the static culture and 60 rpm of agitation, respectively. Moreover, In comparison with the static culture, about 1.5-fold increment in urea production was observed at 30 rpm. Similarly, the highest expressions of albumin and P450 genes were found at 30 rpm stirring rate, which were 4.9- and 19.2-fold of the static culture. Addition of collagen to the microcapsule core composition (ACol/C) could improve the cell proliferation and functionality at 60 rpm in comparison with the cell-laden microcapsules without collagen. The study demonstrated the hepatic cell-laden ACol/C microcapsule hydrogel cultured in the small scale stirred bioreactor at low mixing rate has a great potential for mass production of the hepatic cells while maintaining liver-specific functions.

Keywords: Hepatocytes; Mass production; Microencapsulation; Shear rate; Small scale stirred bioreactor.

Fig. 1

Schematic of bioreactor system

Fig. 2

Phase-contrast microscopy images of microencapsulated HepG2 cells at initial cell density of 2 × 10⁶ cells/ml for microcapsules during 10 days culture period in the stirred bioreactor, (Scale bar: 100 μm)

Fig. 3

Proliferation of HepG2 cells in the microcapsules during 10 day culture in the stirred bioreactor (a), mechanical property of AC and ACol/C microcapsules (b), glucose consumption at the determined days before 50% exchanging of culture medium (c) and the ratio of lactate production to glucose consumption at determined days (d)

Fig. 4

Liver-specific secretions of albumin (a) and urea (b) for microencapsulated HepG2 cell line after 10 days in the stirred bioreactor

Fig. 5

Real time PCR analysis of albumin and P450 expression in microencapsulated HepG2 cells inside AC and ACol/C microcapsules after 10 days dynamic culture