The transport of polymeric microspheres across the ciliated epithelia of the bullfrog

The influence of some hydrophilic polymers on the clearance of particles ac ross the ciliated epithelium of the bullfrog palate has been examined. The polymers studied were Carbopol 907 cross-linked with maltose to provide mic rospheres of varying cross-link density, Carbopol 934P, hydroxypropylmethyl cellulose, chitosan and poly(vinyl alcohol). Transport rates were determine d relative to glass spheres. The polymers in dilute solution (0.1 and 0.5% w/v) resulted in a reduction in the transport rate of the glass spheres. Fo r non-cross-linked microspheres, Carbopol 934P exhibited a lower transport rate than the more slowly hydrating chitosan. The cross-linked poly(acrylic acid) microspheres showed clearance rates which were dependent on the cros s-link density. Incorporation of some preservatives (EDTA, methylhydroxyben zoate, chlorbutol and chlorocresol), known to reversibly retard clearance, into the cross-linked poly(acrylic acid) microspheres produced effects depe ndent on cross-link density: lightly cross-linked microspheres were cleared more slowly than the preservative-free microspheres whilst for more heavil y cross-linked particles the converse was observed. (C) 1999 Elsevier Scien ce B.V. All rights reserved.