Hydroxyl Radical Scavenging Activity of a New Ophthalmic Viscosurgical Device

Abstract

Purpose: To quantify the hydroxyl radical scavenging activity of a new ophthalmic viscosurgical device (OVD) based on sodium hyaluronate and hydroxypropylmethylcellulose (named VISC28) in comparison with Viscoat, Healon, and Amvisc Plus. Methods: The hydroxyl radicals that represent the principal free-radical species generated during phacoemulsification were produced by the Fenton reaction, and the scavenging activity of the tested viscoelastic substances was evaluated in vitro by the 2-deoxy-D-ribose (2-DR) oxidation method that produces the thiobarbituric acid–malondialdehyde (TBA-MDA), complex. An aliquot of viscosurgical formulation was added to phosphate buffer and mixed with 2-DR, Fe^{2 +}/ethylenediaminetetraacetic acid (EDTA), and H₂O₂. The sample mix was incubated and thiobarbituric acid–trichloroacetic acid solution was added. The sample was then incubated for 30 min, and a chromatographic analysis was performed to quantify the TBA-MDA complex. The data were expressed as micromoles of MDA per milliliter of sample. Results: All tested OVDs showed a marked hydroxyl radical scavenging activity. The MDA level was significantly lower in VISC28 (0.045 ± 0.007 μ mol/ml) compared with Viscoat (0.070 ± 0.012 μ mol/ ml, p < 0.05), Amvisc Plus (0.111 ± 0.008 μ mol/ml, p < 0.001), and Healon (0.175 ± 0.016 μ mol/ml, p < 0.001). A reduced scavenging activity was shown by VISC28 phosphate-buffered solution (PBS) (no TRIS and no sorbitol) compared with VISC28 (p < 0.001). Conclusions: The new OVD, VISC28, showed significantly higher hydroxyl radical inhibition compared with the other viscosurgical formulations. The following rank order for the scavenging activity was established: VISC28 > Viscoat > Amvisc Plus > Healon.

KEYWORDS:

• cataract
• free radicals
• hyaluronic acid
• hydroxypropylmethylcellulose