Dexamethasone-poly(dimethylamino)ethyl methacrylate (pDMAEMA) conjugates reduce inflammatory biomarkers in human intestinal epithelial monolayers

摘要

The mucoadhesive polymer, poly(dimethylamino)ethyl methacrylate (pDMAEMA) was synthesised by living radical polymerisation and subsequently conjugated by esterification to the anti-inflammatory corticosteroid, dexamethasone, to separately yield two concentrations of conjugates with ratios of 10:1 and 20:1 active:polymer. The hypothesis was to test whether the active agent maintained in vitro bioactivity when exposed to the apical side of human intestinal epithelial monolayers, Caco-2 and mucous-covered HT29-MTX-E12 (E12). HPLC analysis showed that 80% of the dexamethasone in both conjugates was attached to pDMAEMA. Similar to pDMAEMA, fluorescently-labelled dexamethasone-pDMAEMA conjugates were bioadhesive to Caco-2 and mucoadhesive to E12. Apical addition of conjugates suppressed mRNA expression of the inflammatory markers, NURR1 and ICAM-1 in E12 following stimulation by PGE2 and TNF-α, respectively. Conjugates also suppressed TNF-α stimulated cytokine secretion to the basolateral side of Caco-2 monolayers. pDMAEMA was inactive in these assays. Measurement of dexamethasone permeability from conjugates across monolayers suggested that conjugation reduced permeability compared to free dexamethasone. LDH assay indicated that conjugates were not cytotoxic to monolayers at high concentrations. Anti-inflammatory agents can therefore be successfully conjugated to polymers and they retain adhesion and bioactivity to enable formulation for topical administration.