Exploring molecular dynamics simulation to predict binding with ocular mucin: An in silico approach for screening mucoadhesive materials for ocular retentive delivery systems

In recent times, molecular dynamic (MD) simulations have been applied in the area of drug delivery, as an in silico tool to predict the behaviour of nanoparticles with respect to their interaction with larger biological entities like bilayer membranes, DNA and dermal surface. However, the predictions must be systematically evaluated by extensive studies with actual biological entities in order to deem the in silico models accurate. Thus, in the present study, MD simulation was used to screen ligands with respect to ocular mucoadhesion. Mucin-4, a cell surface-associated mucin was selected as the substrate for the in silico study due to its abundance across the ocular surface. The ligands were then incorporated into a delivery system like nanostructured lipid carriers (NLC) and assessed for mucoadhesion by relevant in vitro and in vivo techniques. The in silico study suggested chitosan oligosaccharide (COS) to have an extensive mucoadhesive potential towards ocular mucin followed by stearylamine (STA) and cetrimonium bromide (CTAB) which showed intermediate and low mucoadhesion respectively. The corresponding in vitro assessment by spectrophotometry and nanoparticle tracking analysis showed a similar outcome wherein COS was found to be extensively mucoadhesive, followed by both STA and CTAB, which showed mucoadhesion to a nearly equal extent. The findings of in vivo confocal imaging following topical administration to rats showed that while COS and STA adhered extensively to the ocular surface, CTAB showed negligible adhesion. MD simulation was thus found to accurately predict interactions critical to mucoadhesion and the same could be fairly correlated well by relevant mucoadhesion studies both in vitro and in vivo.