Fabrication And Studies Of Chitosan-Based Contact Lens

Study of chitosan is highlighted recent years with respect to its natural bio-macromolecular properties. Currently, chitosan has been broadly applied in a lot of fields, e.g. medicine, environment, chemical industry and so on. Observe the utilization of chitosan for fabrication of contact lens seems to be less reported. In this thesis, we reported chitosan-based contact lens and its structure and properties. Initially, two series chitosans were prepared one with confirmed degree of deacetylation, DD, and varied degree of polymerization, DP, and another on the contrary, characterized by FTIR spectroscopy and viscosimetry respectively. Then, utilizing the excellent biological and self-antibacterial possibility, chitosan-based contact lens were further prepared. After that, we studied to load drug in fabricated contact lens and its drug release behavior. Following, tes polyphenols are employed in the presence of chitosan-based contact lens and related UV ability was measured.Experimentally, a set of orthogonal test was designed for fabrication of contact lens in optimally. Results show that a best condition in this case might be as to evaporate about 48 h with a temperature of about 35℃. The concentration of crosslink agent used to be of about 8% for reaction time of about 4h. Observe, these condition could be resulting in contact lens with visible smooth surface and optically.According to this case fabricated chitosan contact lens, the average transmission light is of 93.2%, with a refraction rate of 1.377, both fit the Chinese standard related for contact lens. The water content of chitosan contact lens was determined to be of 54% which is higher then a typical HEMA contact lens, e.g. about 38%. The tensile strength for this case prepared contact lens was found to be in the range of 10-23 MPa which is expected to high than the related Chinese standard, e.g. 4.5 MPa. To check the stability for we made chitosan contact lens, the influence of from special liquid, e.g. the OPTI-FREE contact lens liquid, which was usually employed for protect contact lens, and normal water is usually required and therefore be studied. As expected, result indicated that the average transmission is similarly for using both the deionized water and OPTI-FREE contact lens liquid for we prepared contact lens. Of this measurement, the equilibrium water content for fabricated chiitosan-based contact lens has been further found to be higher in deionized water and lower in OPTI-FREE liquid, while the lower value is acceptable dur to which over 38%.The relationship between the hydrogels oxygen permeability and water content is studied and this leads to provide the possibility for estimation of one unknown from another known previously or being determined. According to measured water content remained in contact lens, the oxygen permeability described as Dk was evaluated. In this case, the Dk was about 20.08×10^-11 （cm²/s）[mlO₂/（ml mmHg）].The dehydrate behavior of chitosan-based contact lens is studied and the average dehydrate ratio was obtained. A model deduced from recorded data showed that the dehydrate behavior for chitosan-based contact lens may follow a first order model. Of this case, the influence of seasons, concentration of crosslink agent, thickness of lens, OPTI-FREE contact lens liquid on the dehydrate ratio is also examined, and we found that the dehydrate ratio is higher in winter and autumn, but lower in summer and spring. The dehydrate ratio was decreased with the increase of lens thickness. The OPTI-FREE contact lens liquid also cause the dehydrate ratio in low. With the increase of crosslink agent concentration, the dehydrate ratio has been found to be increased in the first stage and then decreased.Drug release from the chitosan-based contact lens was studied dynamically by conductivity measurement. The recorded curve has been found with two stages: the first stage follows a second order kinetics model, and the second stage follows a first order kinetics models. A comparison of the FTIR spectra for drug-loaded and drug-non-loaded contact lens suggested that the drug was only combined with the chitosan hydrogel frame due to the H-bond and this is greatly than the covalent bond. This means that the drug loaded in len can be released into tear when this len was used.A study of the UV-len show that the UV properties of len could be enhanced with the inducing of tea polyphenols, and the detailed to be as the adding of tea polyphenols above 2%, the transmission of UVA can be about 3.71% which was less the 9.48%（suggested standard value）, and the UVB to be of 0.146% which also small than suggested value, e.g. 0.948% （American Optometric Association standard about ultraviolet absorbing contact lens）. Recorded DSC curve further indicated that the water content for UV lens seems to be the increase the increased of the tea polyphenols percent.Finally, SEM photographs indicated that the chitosan-based contact lens has a smooth surface which is capable to guarantee lens with splendid wear comfortable performance.