Development of new polycations for cell encapsulation with alginate

Microencapsulation is one of the most important techniques used in immobilizing cells for biomedical applications. Of the many microcapsules derived from various materials, the one formed by alginate and poly(l-lysine) is probably the most common. These microcapsules, prepared under mild conditions, provide an adequate environment for cell growth. Unfortunately, they usually lack mechanical strength due to the ionic interaction, instead of covalent bonding, between alginate and polycations. er to improve the mechanical strength, we have investigated the feasibility of using poly(vinylamine) and poly(allylamine) to replace the conventional poly(l-lysine). Of these two polycations, poly(allylamine) formed microcapsules of about the same strength as that prepared from poly(l-lysine). On the other hand, microcapsules prepared from alginate and poly(vinylamine) have about 40% of capsules weaker than that prepared from poly(l-lysine). However, the remaining 60% of its population remained intact even after 48 h of mechanical vibration test. ernative strengthening method is to cross-link poly(l-lysine) by chemical or photochemical process. The chemical method was conducted by treating microcapsules with tosylated poly(vinylalcohol). This treatment resulted in the cross-linking of poly(l-lysine) in the capsular membrane and therefore, a significant improvement of capsular strength. For the photochemical method, a photosensitive polycation was prepared by partially modifying the amino groups of the poly(l-lysine) with α-phenylcinnamyldieneacetyl chloride. The capsules formed from alginate and this photosensitive polymer yield the highest mechanical strength after irradiation of light at ∼320 nm. All microcapsules investigated were permeable to the proteins of mid-size molecular weight such as myoglobin. Cells can be entrapped and cultured by using this encapsulation technology.