Polymeric gene transfection on insulin-secreting cells: Sulfonylurea receptor-mediation and transfection medium effect

Purpose. In vitro transfection of secreting cells is regarded as one strategy for improved cell engineering/transplantation. Insulin-secreting insulinoma cell lines or pancreatic β-cells could be genetically engineered using designed polymeric vectors which are safer than viral vectors. This study investigates the effects of the constituents in transfection media on polymeric transfection. Methods. Polyplexes conjugated with sulfonylurea (SU) were evaluated under different transfection conditions for gene transfection and their effects on cytotoxicity and insulin secretion. Several components in transfection media specifically associated with the insulin secretion pathway were amino acids, vitamins, Ca²⁺ and K⁺. The interactions of the polyplexes with insulin were monitored by surface charge and particle size to monitor how insulin as a protein influences transfection. Results. For an insulin-secreting cell line (RINm5F), polyplexes in Ca²⁺- containing KRH medium (Ca²⁺(+)KRH) enhanced transfection and did not cause damage to biological functions. When adding amino acids, vitamins, or K⁺ or depleting Ca²⁺ from Ca²⁺(+)KRH, poly(l-lysine)/DNA complexes showed a greater reduction in transfection than SU receptor (SUR)-targeting polyplexes (SU-polyplex). Positively charged polyplexes interacted with insulin, developing a negative surface charge, and these interactions may cause a decrease in transfection. Conclusion. The findings suggest that in vitro and ex vivo polymeric transfection of insulin-secreting cells can be modulated and enhanced by adjusting the transfection conditions.