Surface modifications of alginate/ poly(L-lysine) microcapsular membranes with poly(ethylene glycol) and poly(vinyl alcohol)

Three different surface modifications were conducted on the membranes of double-layer alginate/ poly(image-lysine) microcapsules with tosyl chloride-activated poly(ethylene glycol), cyanuric chlorideactivated poly(ethylene glycol) and tosyl chloride-activated poly(vinyl alcohol), separately. All these surface modifications strengthen the microcapsular membranes. Of the three surfacemodified microcapsules, those treated with cyanuric poly(ethylene glycol) and tosylated poly(vinyl alcohol) have mechanical strength higher than that treated with tosylated poly(ethylene glycol). The permeabilities of the proteins were only slightly affected by the surface modifications. When IW32 erythroleukaemia cells were entrapped inside these microcapsules, cells proliferated to a density of (1.0–1.5) × 107 cells cm−3 after 7 d culturing compared with 2 × 106 cells cm−3 attained by free cell culturing. The intracapsular concentration of erythropoietin which was secreted by the IW32 cells accumulated to concentrations of 5–7 U cm−3. In addition, 3T3 cells were found to have a very low tendency to attach to the microcapsular membranes of all three surface-modified preparations.