title: Fluorescent solute-partitioning characterization of layered soft contact lenses.
abstract: Partitioning of aqueous packaging, wetting, and care-solution agents into and out of soft contact lenses (SCLs) is important for improving wear comfort and also for characterizing lens physico-chemical properties. We illustrate both features of partitioning by application of fluorescent-solute partitioning into DAILIES TOTAL1® (delefilcon A) water-gradient SCLs, which exhibit a layered structure of a silicone-hydrogel (SiHy) core sandwiched between thin surface-gel layers. Two-photon fluorescence confocal laser-scanning microscopy and attenuated total-reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) characterize the lens and assess uptake profiles of six prototypical fluorescent solutes. Comparison of solute uptake in a SiHy-core prototype lens (i.e., O2OPTIX(TM)) validates the core SiHy structure of DAILIESTOTAL1®. To establish surface-layer charge, partition coefficients and water contents are obtained for aqueous pH values of 4 and 7.4. Solute fluorescence-intensity profiles clearly confirm a layered structure for the DAILIES TOTAL1® lenses. In all cases, aqueous solute partition coefficients are greater in the surface layers than in the SiHy core, signifying higher water in the surface gels. ATR-FTIR confirms surface-layer mass water contents of 82±3%. Water uptake and hydrophilic-solute uptake at pH 4 compared with that at pH 7.4 reveal that the surface-gel layers are anionic at physiologic pH 7.4, whereas both the SiHy core and O2OPTIX™ (lotrafilcon B) are nonionic. We successfully confirm the layered structure of DAILIES TOTAL1®, consisting of an 80-μm-thick SiHy core surrounded by 10-μm-thick polyelectrolyte surface-gel layers of significantly greater water content and aqueous solute uptake compared with the core. Accordingly, fluorescent-solute partitioning in SCLs provides information on gel structure and composition, in addition to quantifying uptake and release amounts and rates.
authors.affiliation: Chemical and Biomolecular Engineering Department, University of California, 101E Gilman, Berkeley, CA 94720-1462, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Dursch
authors.affiliation: Chemical and Biomolecular Engineering Department, University of California, 101E Gilman, Berkeley, CA 94720-1462, USA.
authors.forename: D E
authors.initials: DE
authors.lastname: Liu
authors.affiliation: Chemical and Biomolecular Engineering Department, University of California, 101E Gilman, Berkeley, CA 94720-1462, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Oh
authors.affiliation: Chemical and Biomolecular Engineering Department, University of California, 101E Gilman, Berkeley, CA 94720-1462, USA; Vision Science Group, University of California, Berkeley, CA 94720, USA. Electronic address: radke@berkeley.edu.
authors.forename: C J
authors.initials: CJ
authors.lastname: Radke
mesh_terms: D001360:Avidin / Q000737:chemistry; D003263:Contact Lenses, Hydrophilic; D003911:Dextrans / Q000737:chemistry; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives / Q000737:chemistry; D005453:Fluorescence; D057446:Hydrodynamics; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D008856:Microscopy, Fluorescence; D017550:Spectroscopy, Fourier Transform Infrared; D014867:Water / Q000737:chemistry
chemical_list: D003911:Dextrans; C015219:fluorescein isothiocyanate dextran; C036963:fluorescein isothiocyante avidin; D014867:Water; D001360:Avidin; D016650:Fluorescein-5-isothiocyanate
keywords: Attenuated total-reflectance Fourier-transform infrared spectroscopy; Contact lens; DAILIES TOTAL1® (delefilcon A); Fluorescence confocal microscopy; Partition coefficient