An atomic force microscopy investigation of bioadhesive polymer adsorptiononto human buccal cells

Atomic force microscopy (AFM) was used to examine the buccal cell surface i n order to image the presence of adsorbed bioadhesive polymers identified f rom previous work. Isotonic saline solution (5 ml) containing either polyca rbophil (pH 7.6), chitosan (pH 4.5) or hydroxypropyl methylcellulose (pH 7. 6) (0.5% w/v) was exposed to freshly collected buccal cells (ca. 48 x 10(4) cells/test) for 15 min at 30 degrees C. The cells were then rinsed with a small volume of double distilled water, allowed to air-dry on a freshy clea ved mica surface and imaged using contact mode AFM. Untreated cells showed relatively smooth surface characteristics, with many small 'crater-like' pi ts and indentations spread over cell surfaces. Cells that had been treated with all the investigated polymers appeared to have lost the crater and ind entation characteristic and gained a higher surface roughness. These result s suggest that polymer chains had adsorbed onto the cell surfaces. Quantita tive image analysis of cell topography showed significant increases (P < 0. 05) in arithmetic roughness average (R-a) for all the investigated polymer treated cells surfaces with respect to untreated control specimens. The cha nges in surface topography indicate the presence of adsorbed polymer, confi rming previous work. This study demonstrates the suitability of AFM as a po werful and sensitive technique for detecting and imaging bioadhesive polyme rs present on mucosal cell surfaces. (C) 2000 Elsevier Science B.V. All rig hts reserved.