Detection of protein deposition on contact lens type polymeric hydrogels by Coomassie blue R staining

A novel gellan gel-based microcarrier for anchorage-dependent cell delivery

Competent vehicles are highly sought after as a means to transplant cells for tissue regeneration. In this study, novel hydrogel-based microspherical cell carriers are designed and developed with an FDA-approved natural polysaccharide, gellan gum. The bulk fabrication of these microspheres is performed via a water-in-oil (W/O) emulsion process followed by a series of redox (oxidation-reduction) crosslinking treatments; this enables the microspherical dimensions to be precisely manipulated in terms of injectability, and simultaneously ensures the structural stability. To acquire adhesion affinity with anchorage-dependent cells (ADCs), a covalent coating of gelatin is further applied on the microspherical surfaces. The final product is constructed as a variety of gelatin-grafted-gellan microspherical cell carriers, abbreviated as "TriG" microcarriers. The cell-loading tests are conducted, respectively, with human dermal fibroblasts (HDFs) and human fetal osteoblasts (hFOBs). Morphological observation from optical microscopy and field emission scanning electron microscopy indicates that the HDFs spread well and populate rapidly on surfaces of TriG microcarriers. Immunofluorescent staining reveals the activation of focal adhesion and subsequent organization of F-actin from the attached cell surfaces, which suggests the TriG microspherical substrate is favorable to ADC adhesion and therefore capable of promoting HDF proliferation to achieve confluence by turning over three times within 10 days. The hFOBs are also cultivated on the TriG carriers, where ideal viability and clear potentials for osteogenesis are demonstrated by fluorescent "Live/Dead" screening and specific histobiochemical indications. All these findings suggest that the TriG microcarriers are suitable to provide open platforms for therapeutic ADC proliferation and differentiation.

Matrix-assisted laser desorption ionization mass spectrometry detection of proteins adsorbed in vivo onto contact lenses

Identification of the biomolecules that form the first adsorbed monolayer, which thus effect "interface conversion", in competitive adsorption from multicomponent biological solutions can be challenging because of limitations in mass resolution and sensitivity of established techniques. In this study matrix-assisted laser desorption ionization (MALDI) time of flight mass spectrometry is developed and applied as a novel surface analytical method to enable analysis of adsorbed multicomponent biomolecule layers directly on the biomaterial surfaces. We show that proteins adsorbed in vivo (on human eyes) on contact lenses can be detected rapidly and conveniently by the diagnostic highly resolved mass signals recorded by MALDI mass spectrometry. This new approach allows detection of minor (and major) proteinaceous constituents of biofouled layers at levels substantially below monolayer coverage. Identification is done by comparison with molecular masses of known proteins. Specifically, it is shown that in addition to lysozyme, other low molecular weight proteins adsorb from human tear fluid onto contact lenses; these proteins had not been detected in earlier studies using other techniques.

The effect of eye closure on protein and complement deposition on Group IV hydrogel contact lenses: relationship to tear flow dynamics

PURPOSE

This study was designed to determine the effect of overnight eye closure on the rate and composition of protein deposition on high water content ionic matrix soft contact lenses (Group IV SCLs) and to extrapolate from this data information on the probable change in the rate of reflex-type tear secretion associated with eye closure.

METHODS

Group IV SCLs were temporally sampled after equivalent periods of wear under closed eye (C) or open eye (O) conditions. Lenses were rinsed in saline and the majority of the tightly bound protein extracted at 90 degrees C in 40% urea, containing 1% SDS, 1 mM DTT, 100 mM Tris-HCl (pH 8.00). Residual protein was determined by Coomassie staining of the extracted lenses and densitometric analysis. Extracted protein was quantitated and separated by SDS-PAGE. Gels were either stained with Coomassie blue or reversibly stained with imidazole-zinc and blotted. Blots were PAS stained, or lectin and antibody probed for glycoproteins, secretory IgA (sIgA), IgG, lysozyme and complement C3. Laboratory simulated deposition studies were carried out on unworn lenses exposed to HPLC purified lysozyme.

RESULTS

The protein in the saline rinse, to a large degree mirrored the composition of tear fluid in which the lens had been residing (O or C). This would suggest that the saline wash consists of residual tear fluid and loosely adherent protein. In contrast, the urea extracts were highly homogeneous consisting primarily of lysozyme and to lesser extent lysozyme dimer. This supports the contention that the Group IV SCL functions in the eye much as cationic exchange resin selectively absorbing lysozyme. C extracts also proved relatively enriched in trace amounts of sIgA, IgG and complement C3 and its breakdown products. High levels of C3 and C3 breakdown products were specifically recovered only in the C worn lens extracts from a subject experiencing unilateral contact lens associated corneal infiltrates from the affected eye. In all subjects, markedly less protein (lysozyme) was recovered in urea extracts of lenses exposed to 7-8 h of closed eye as compared to open eye wear (0.20 +/- .08 versus 0.79 +/- .15 mg/lens (n = 6)). Temporal studies further revealed that deposition was linearly related to duration of wear during the initial phase of conditioning film formation giving rise to rate constants for lysozyme deposition of 2.2 +/- 0.29 (n = 5) and 0.20 +/- 0.06 microgram/min (n = 4) under open and closed eye conditions respectively. With further wear, deposition eventually reached a steady state. Under laboratory conditions, lysozyme was much rapidly and quantitatively removed from solution in a manner following a hyperbolic plot. This suggests that during the initial phase of deposition the rate of deposition is limited by the capacity of the tear fluid to deliver lysozyme to the lens surface under these two extremes of conditions.

CONCLUSIONS

Eye closure profoundly affects the rate of lysozyme deposition on Group IV hydrogels and the composition of minor biofilm constituents in a manner that could affect biocompatibility. Findings support the contention that eye closure results in a > 90% reduction in the rate of reflex-type tear secretion.

Silicone derivatives for contact lenses: functionalization, chemical characterization, and cell compatibility assessment

Epoxy ring-opening functionalization of polymers at random sites along chains with various chemical groups has been demonstrated. The reaction is performed in an aqueous solution under mild conditions in order to minimize degradation of the macromolecular chains. Silicone lenses made of copolymers with epoxy side chains were functionalized with 4-hydroxybutyric acid, sodium salt. The carboxylated silicone derivatives were characterized by ESCA and radiotracers. A mean value of 30% reaction yield was concluded, based upon data from both methods; nevertheless, the latter can be improved up to 50% or more if the conditions of preparation of the epoxydized silicone lenses are optimized. Derivatized silicones were coated in the wells of culture plates to evaluate the cell compatibility of these new polymers with a fibroblast cell line (McCoy's). No cellular toxicity was observed.

Effect of antidenaturant drugs on lysozyme deposit formation on soft contact lenses by liquid chromatography--electrochemical detection

The effect of some antidenaturant drugs on the formation of lysozyme deposits on soft contact lenses was investigated by in vitro experiments. Results were obtained which encourage the use of this strategy to reduce lens spoilage. At the same time emphasis is given to the possibility that some functionalities (i.e. lysine groups) present in drug molecules could promote protein adsorption. In order to evaluate at a quantitative level the effectiveness of the drugs used to minimize the formation of deposits on soft contact lenses, a selective method for the determination of adsorbed lysozyme was developed. It is based on the hydrolysis of the 'lens/adsorbed lysozyme' system, followed by high performance liquid chromatography coupled to electrochemical detection of the released tryptophan residues. The lysozyme calibration curve was linear up to 5 mg ml-1 and the detection limit was 5 ng injected.