Characterization of Polyethersulfone Membranes for Tear Fluid Collection

The sampling of tear fluids is essential for the reproducibility of tear assays. But, an operable, efficient and stable method for tear collection has not been widely established. This study evaluated the utility of polyethersulfone membranes (PESms) for tear collection and compared it with two frequently employed approaches: the use of Schirmer test paper (STP) and capillary tube (CaT).

STP and PESms (0.45 and 0.65 µm) were examined using scanning electron microscopy(SEM), applied to soak up water, bovine albumin and cellular lysates, and employed to collect tear fluids from rabbits. The proteins in the cellular lysates and tear fluid were characterized through band profiling of SDS-polyacrylamide electrophoresis (PAGE) gels. Western blot analyses with antibodies against vinculin and lysozyme C were used to compare rabbit tear fluids sampling with CaT, STP and PESm. Rabbit ocular surfaces and eye blinking were evaluated under different conditions.

The SEM examination showed that PESms exhibited much smoother surfaces and smaller pores than STP. PESm65 exhibited the highest water absorption and water recovery in vitro. Although SDS-PAGE revealed no obvious differences in the cellular or tear protein band patterns, the highest Dice's similarity coefficient and lowest variance in the differences in peak heights(i.e. band intensities) were observed in the PESm65 samples. The Western blot showed that the band intensities of vinculin protein in tear fluids obtained using CaT, STP and PESm65 are in order of CaTPESm65>STP. PESm65 exhibited less blinks and conjunctival injuries than STP during sampling-rabbit tears.

Tear collection using PESm has less variance in protein components and is easily operable than traditional STP. PESm possesses the potential for clinical utilization in diagnostic tear assays.