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

The influence of some hydrophilic polymers on the clearance of particles across the ciliated epithelium of the bullfrog palate has been examined. The polymers studied were Carbopol 907 cross-linked with maltose to provide microspheres of varying cross-link density, Carbopol 934P, hydroxypropylmethylcellulose, chitosan and poly(vinyl alcohol). Transport rates were determined 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. For 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 cross-link density. Incorporation of some preservatives (EDTA, methylhydroxybenzoate, chlorbutol and chlorocresol), known to reversibly retard clearance, into the cross-linked poly(acrylic acid) microspheres produced effects dependent on cross-link density: lightly cross-linked microspheres were cleared more slowly than the preservative-free microspheres whilst for more heavily cross-linked particles the converse was observed.