Safety Evaluation of Intracameral and Subconjunctival Injection of a Novel Mucoadhesive Polysaccharide Isolated from Bletilla striata in Rabbit Eye

Purpose: To evaluate the safety of intracameral and subconjunctival injection of a novel mucoadhesive polysaccharide isolated from Bletilla striata in rabbit eye. Methods: One hundred microliters (100 mu L) of Bletilla striata polysaccharide (BsP) at concentrations of 10, 40, and 80mg/mL was intracamerally or subconjunctivally injected into rabbit eyes. Phosphate-buffered saline and 10mg/mL hyaluronic acid solution were also injected as controls. BsP safety was evaluated via clinical followup and histological analysis. The dead corneal endothelial cells were observed by vital staining with alizarin red and trypan blue at 14 days after intracameral injection. Finally, in the intracameral injection study, scanning electron microscopy was performed for evaluation of the structure of the corneal endothelium and anterior lens capsules. Results: Subconjunctival injection of 10mg/mL BsP does not cause pathological changes or an inflammatory response. Concentration greater than 10mg/mL of BsP (40 or 80mg/mL) leaded to a slight inflammatory response, but the rabbits recovered well in 3 days. The pathological observation further confirmed the safety of subconjunctival injection of BsP, and subconjunctival injection of 80mg/mL BsP caused no lesion of the ocular tissues. Intracameral injection of 80mg/mL of BsP did not cause a significant inflammatory reaction, and an even lower inflammatory response was observed in rabbits intracamerally injected with 40 or 10mg/mL BsP. All rabbits intracamerally injected with BsP recovered within 7-14 days. BsP had little effect on the bloodaqueous barrier's integrity when the concentration was 10mg/mL; at 40 or 80mg/mL, a mild effect was observed, and the rabbits recovered in 1-3 days. Intracameral BsP injected at a concentration of 80mg/mL had a negative impact on the corneal endothelium and lens, but concentrations of 40 or 10mg/mL could be injected safely. Conclusions: BsP injection into the subconjunctival space and anterior chamber in rabbits at low concentrations (such as 10mg/mL) did not have adverse effects.