The effects of
alginate composition on the growth of murine
insulinoma betaTC3 cells encapsulated in
alginate/poly-L-lysine/
alginate (APA) beads, and on the overall metabolic and secretory characteristics of the encapsulated cell system, were investigated for four different types of
alginate. Two of the
alginates used had a high
guluronic acid content (73% in
guluronic acid residues) with varying molecular weight, while the other two had a high
mannuronic acid content (68% in
mannuronic acid residues) with varying molecular weight. Each composition was tested using two different
polymer concentrations. Our data show that betaTC3 cells encapsulated in
alginates with a high
guluronic acid content experienced a transient hindrance in their metabolic and secretory activity because of growth inhibition. Conversely, betaTC3 cells encapsulated in
alginates with a high
mannuronic acid content experienced a rapid increase in metabolic and secretory activity as a result of rapid cell growth. Our data also demonstrate that an increase in either molecular weight or concentration of high
mannuronic acid alginates did not alter the behavior of the encapsulated betaTC3 cells. Conversely, an increase in molecular weight and concentration of high
guluronic acid alginates prolonged the hindrance of
glucose metabolism, insulin secretion and cell growth. These observations can be best interpreted by changes in the microstructure of the
alginate matrix, i.e., interaction between the contiguous
guluronic acid residues and the Ca2+
ions, as a result of the different compositions.