Exact determination of phagocytic activity of alveolar macrophages toward polymer microspheres by elimination of those attached to the macrophage membrane

A method for exact determination of phagocytic activity of alveolar macrophage (M phi) cells toward synthetic microspheres (MS) by optical microscopy was developed. We examined the effectiveness of the treatment of M phi samples with trypsin, acid or xylene to remove the polystyrene latex microspheres (PSL MS) attached to M phi cell membranes during their phagocytosis by M phi cells. We found that centrifugation, which was employed to collect M phi samples after incubation with MS, affected significantly the efficiency of the various treatments. Of the three treatments, xylene treatment without centrifugation was the most effective to determine the phagocytic activity of M phi cells, as xylene dissolved the PSL MS on the cell surface almost completely. This treatment was also effective in the case of poly(lactic-co-glycolic acid) MS (PLGA MS), which have been commonly used as an efficient vehicle for drug delivery system. (C) 2007 Elsevier B.V. All rights reserved.