Study On TiN Film Modification For IOLs

Titanium nitride (TiN) as a kind of biomaterial with excellent mechanical properties and biocompatibility is widely used. TiN thin film has a good optical performance and selective projection spectrum. In this paper, we used the method of ion beam sputtering deposition to deposit TiN thin film on the PMMA intraocular lens surface. We obtained different titanium nitride thin films in different energy parameters. When the sputtering energy was low, we cannot obtain the ideal thin film. But large energy would have created the destruction to the PMMA material; therefore the appropriate energy would be very important to the thin film formation. We detected the physical chemical properties, optical properties and biological performance of golden titanium nitride thin films. The samples were characterized by contact angle measuring instrument , Atomic Force Microscope.(AFM), X-ray Photoelectron Spectrum (XPS) and Scanning Electronic Microscope (SEM) respectively;contact angle, resolution, diopter and transmission spectra of modified (IOLs) were measured; and tested on biocompatibility including cytotoxicity and hemolysis.The results showed that modification does not reduce the resolution of IOLs, whereas enlarged diopter slightly within the proper extent. Spectral transmittance of golden yellow IOLs is 0, less than 30%, 55% or more than 80% when wavelength of light is from 200nm to 400nm, from 400 to 430nm, from 430-480nm or from 480-800nm, respectively, indicating that golden yellow crystals have best blue-ray blocking effect. The basic optical properties of modified IOLs remain unchanged, except for the increasing of absorption on blue-ray and ultraviolet.SEM showed that the surface of modified IOLs is integrity and smooth, illustrating that modification does not affect the surface morphology of IOLs. AFM showed that the thin film has smooth surface. The result of XPS showed that the major content of the surface of IOLs contains C, N, Ti, O, and the proportion of C atoms is 50%, which is relatively high. The proportion of N atoms accounted for about 25%, Ti about 21%, whereas the ratio of N to Ti was a little higher than 1. Test of contact angle showed that the modified IOLs had smaller contact angle, which illustrated better hydrophilicity.The results showed that Unmodified and modified cytotoxicity were 0.6 and 1 grade respectively; hemolytic rate of modified and unmodified were less than 5%, in line with national standards.Above all, the modified IOLs, which protected its previous surface morphology and optical charicteristics, not only can absorb blue light but also had better biocompatibility. This study provides fundamental experimental data of modified IOL for further clinical application.