A simple ocular mucoadhesion assay

Purpose. Multiparticulate systems provide unparalleled opportunities for improved drug targeting al epithelial surfaces. The nature of interactions between these potential drug carriers and the ocular surface is poorly understood, and is difficult to study in vivo. The purpose of this investigation was to develop a simple assal for microparticle binding to ocular mucins which would allow sueh interactions to he dissected in detail. Methods. Ocular mueus was collected by suction from the ocular surface of 12 normal dogs; dispersed in a eocktail of proteinase inhibitors: and secreted mucins fractionated and purified by CsCl density gradient centrifugal ion. and gel filtration. Ocular mucins in the densitv range 1,36-1.47g/rnl, representing n major ocular mucin fraction, were used to develop A) an adhesion assay, based on mucin coated microtitre plates: followed by spectrophotometric quantification and B) a precipitation assay, based on the removal of mucin/microparticle aggregates from a standard mucin solution by ccntrifugalion: followed by quant ill cation of residual mucin on slot blots. The following micro particles were examined: plain latex (0.3f.im); carboxylale (l-m); carboxyl (l(.im): sulphate (1pm): amidine (0.5nm). Results The precipitation assay was reproducible, whereas the adhesion of microparticles to microtitre plates was uneven, and showed variability between equivalent samples. Avidity of mucoadhesion was shown in the order: plain latex amidinc>sulphate-(;arboxylate=carboxyl. Conclusions. Solid phase methodolog) may be unsuitable for in vitro assays of ocular mucoadhesion: liquid phase assays being preferable. The polymer support of latex microspheres is a significant factor in determining mucoadhesion. Supported by Pfizer Pharmaceutical s. C5.