MICROENCAPSULATED HUMAN HEPATOMA (HEPG2) CELLS - CAPSULE-TO-CAPSULE VARIATIONS IN PROTEIN SECRETION AND PERMEABILITY

Human hepatoma (HepG2) cells were microencapsulated in hydroxyethyl me thacrylate-methyl methacrylate by an interfacial precipitation process . The secretion of cr,-antitrypsin (AT: 52 kDa) and fibrinogen (Fbg: 3 40 kDa) from individual capsules was determined using sensitive enzyme -linked immunosorbent assays. A significant capsule-to-capsule variati on in the secretion rates of both AT and Fbg was found. After 2 weeks of in vitro culture, similar to 20 and 70% of the capsules did not sec rete any detectable AT and Fbg, respectively. The relative secretion o f Fbg with respect to AT (Fbg/AT) for those capsules which secreted AT also varied among the individual capsules: similar to 50% of capsules had zero Fbg/AT, presumably indicating the fraction of the capsules e xhibiting the expected sieving effect to the larger protein Fbg but no t to the smaller protein AT. Using a new procedure for the permeabilit y of individual capsules (horseradish peroxidase, 40 kDa, as the model protein), a significant capsule-to-capsule variation in protein perme ability was found consistent with the observed variation in Fbg and AT release.