Structural Heteropolysaccharide Adhesion to the Corneal Glycocalyx

Abstract

The cornea presents unique challenges to wound care. The cornea is constantly exposed to bacterial colonization, has ongoing risk of wound‐related astigmatism, and is cumbersome for traditional wound dressings. A potential solution to these challenges is provided by the corneal glycocalyx.Recent high pressure rapid freezing fixation techniques suggest that the glycocalyx is much thicker than previously believed. In the case of the cornea, the glycocalyx may provide an opportunity for wound care anchored to the transmembrane carbohydrate surface layer.To probe the surface glycocalyx we used a plant‐derived structural heteropolysaccharide called pectin. Pectin has been shown to mirror the structure of the glycocalyceal surface layer of visceral organs. To test the adhesivity of pectin to the corneal glycocalyx, high methoxyl citrus pectin was molded into tape form. Bovine globes were obtained from a local abattoir and used same day. Experiments were performed with custom fixtures using a materials analyzer (TA‐XT plus, Stable Micro Systems). To assess pectin adhesion to cornea, pectin was compressed onto the corneal surface then withdrawn, recording force and distance. A corneal incision was sealed with pectin and subject to increased pressure, until leak. At least three biologic replicates were analyzed, expressed as mean ± one standard deviation. Significance was assessed by Student’s T‐test. Pectin films on cornea were also fixed with formalin and imaged using a scanning electron microscope (Philips XL30 ESEM).Pectin films were flexible, translucent, thin (80um), and did not distort an Amsler grid. Pectin was significantly more adherent (3.2±0.54 N) to the bovine cornea than control polymers nanocellulose fibers (1.2±0.4 N), sodium hyaluronate (1.7±0.7 N), and carboxymethyl cellulose (1.3±0.1)(p<0.05). The work of adhesion, reflecting the area under the adhesion curve, was also significantly greater (p<0.05, asterisk, Figure 1). The cornea incisions sealed with pectin were resistant to pressure fluctuations ranging from ‐51.3±8.9 mmHg to +214.4±68.0 mmHg, both extremes beyond physiologic human intraocular pressures. Sudden or complete sealant failure was not observed. Consistent with these findings, scanning electron microscopy demonstrated a low‐profile tape densely adherent to the bovine cornea (Figure 2).The tensile and peel adhesive strength of the pectin biopolymer suggests a mechanism of polymer‐polymer entanglement with the corneal glycocalyx. As a therapeutic option for corneal wounds, the entangled pectin provides not only a protective barrier, but also an opportunity for pectin‐embedded drug delivery.