Hydrophilic polymers: interactions with lipid layers and ferning patterns

Abstract

AbstractPurposeTo evaluate (i) the mucomimeticity of pharmaceutically applicable hydrophilic polymers (HP) as well as (ii) their interactions with human meibum films.MethodsFour HP were used‐hyaluronic acid (HA), cross‐linked hyaluronic acid (CHA), carboxymethyl cellulose (CMC) and gellan gum (GG)‐ at the concentrations of 0.0001, 0.001,0.01,0.05, 0.1%. HP mucomimeticity was probed by the formation of tear‐like ferning patterns (TFP) after HP solution drop evaporation. The interactions between HP and meibum at the air/water interface were examined in vitro at blink‐like compression/expansion of the film area by Langmuir surface balance. Surface pressure (π)‐area (A) isocycles and stress relaxations were used to assess the sample’s lateral elasticity and reorganization during area cycling. Films morphology was monitored by Brewster Angle Microscopy (BAM).ResultsSignificant differences were observed in the capability of HP to form ferning patterns: CHA (≥0.001%) > HA (≥0.01%) = CMC (≥0.01%) > GG (≥0.05%). CHA, HA, CMC and GG enhanced the uniform spreading of meibomian layers as well as their elasticity and rapid reorganization at blink like area cycling in concentration dependent manner. BAM micrographs revealed considerable thickening of the meibomian films in the presence of HP.ConclusionsThe combination of tear ferning and Langmuir surface balance studies allows to simultaneously evaluate the mucomimetic and the lipid interaction properties of HP. TFP forming polymers enhanced both (i) the uniform spreading and structure of meibomian layers and (ii) their dynamic surface properties. Cross‐linking HA was particularly efficient both in ferning pattern and meibomian film systems.