In-vitro Affinity for Nicotine of Contact Lenses of Different Materials

Nicotine is a toxic compound belonging to the alkaloid familyand it is present in high concentrations in the leaves of tobaccoplants (Nicotiana tabacum). Both smokers and non-smokers areexposed to this chemical because of direct fruition of tobaccoderivatives and its presence in the environment as a pollutant(Liu et al., 2018). In clinical contact lens practice, this molecule can be dangerous because it can adhere to the surface of con-tact lenses (CLs) (Broich et al., 1980). As for other contaminants,nicotine can have a negative impact on CL properties and ocularhealth causing infection and inflammation (Panthi & Nichols,2018;Rabiah et al., 2019). The purpose of this study was todetermine thein-vitroaffinity of CLs to nicotine using UV-VISspectrophotometry.Thirteen different materials belonging to 4 out of 5 FDAgroups were chosen according to the availability on the market:1 group I hydrogel CL (Polymacon), 3 group II hydrogel CLs(Nelfilcon A, Omafilcon A, Nesofilcon A), 4 group IV hydrogelCLs (Etafilcon A, Methafilcon A, Filcon IV, Ocufilcon D), and 5group V silicone hydrogel CLs (Comfilcon A, Delefilcon A, Lo-trafilconA,LotrafilconB,SomofilconA).UVabsorbancespectraof each of these CL materials were acquired with a Jasco V-650spectrophotometer, prior to and after a 10-minute exposure to a2 mM nicotine solution, followed by a brief rinse in saline solu-tion in order to remove the superficial nicotine. The spectrumof the clean CL was numerically subtracted from the spectra ofeach CL after the exposure to the nicotine solution. The result-ing spectra show a peak centred at about 260 nm, due to thepresence of nicotine. The intensity of this peak was then com-pared to the expected absorbance at the equilibrium (assuminga CL hydration with 0.5 mM nicotine solution), calculated ac-cording to the central thickness and percentage of hydrationof each CL. The measured/expected ratio provided a relativevalue which allowed a comparison of nicotine incorporation inthe investigated materials.For each CL, a different measured/expected ratio was found.Group II hydrogel materials showed an absorbance in goodagreement with the calculated equilibrium value (range: 0.8-1.0), except for Nesofilcon A, which displayed a ratio of 0.3. Onthe other hand, Group IV hydrogel materials showed an inten-sity of the nicotine peak between two and three times higherthan the expected equilibrium level (range: 2.1-2.4) and GroupV silicone hydrogels showed an opposite result, with a muchlower absorbance than expected (0.2-0.4). As far as Group I isconcerned, only Polymacon wasmeasured and itshowed aratioof 0.6. In conclusion, despite small differences, similar valueswere displayed by CLs belonging to the same FDA group: inparticular, ionic high-water-content materials (Group IV) pre-sented the highest affinity to nicotine, whereas silicone hydro-gels (Group V) showed the lowest. These results suggest thatin-vitroaffinity of CL materials for nicotine depends on their chem-ical and physical properties.ReferencesBroich, J. R., Weiss, L., & Rapp, J. (1980). Isolation and identification of biolog-ically active contaminants from soft contact lenses. I. Nicotine deposits on wornlenses.Investigative Ophthalmology & Visual Science,19(11), 1328–1335.Liu, S.-H., Tang, W.-T., & Yang, Y.-H. (2018). Adsorption of nicotine in aqueoussolution by a defective graphene oxide.Science of the Total Environment,643,507–515.Panthi, S., & Nichols, J. J. (2018). An imaging-based analysis of lipid deposits oncontact lens surfaces.Contact Lens and Anterior Eye,41(4), 342–350.Rabiah, N. I., Scales, C. W., & Fuller, G. G. (2019). The influence of protein de-position on contact lens tear film stability.Colloids and Surfaces B: Biointerfaces,180, 229–236.