Albumin adsorption to contact lens materials: A review

POSS and PEG Contained Copolymer for Antibioadhesive Rigid Contact Lenses Materials Application

Myopia is a global public health issue. Rigid contact lenses (RCLs) are an effective way to correct or control myopia. However, bioadhesion issues remain one of the significant obstacles limiting its clinical application. Although enhancing hydrophilicity through various surface treatments can mitigate this problem, the duration of effectiveness is short-lived and the processing involved is complex and costly. Herein, an antiadhesive RCLs material was designed via 8-armed methacrylate-POSS (8MA-POSS), and poly(ethylene glycol) methacrylate (PEGMA) copolymerization with 3-[tris(trimethylsiloxy)silyl] propyl methacrylate (TRIS). The POSS and PEG segments incorporated P(TRIS-co-PEGMA-co-8MA-POSS) (PTPM) material was obtained and their optical transparency, refractive index, resolution, hardness, surface charge, thermal features, and wettability were tested and optimized. The antibioadhesion activities, including protein, lipid, and bacteria, were evaluated as well. In vitro and in vivo results indicated that the optimized antibioadhesive PTPM materials present good biocompatibility and biosafety. Thus, such POSS and PEG segments containing material were a potential antibioadhesive RCL material option.

Improved triamcinolone acetonide-eluting contact lenses based on cyclodextrins and high hydrostatic pressure assisted complexation

Contact lenses (CLs) constitute an advantageous platform for the topical release of corticosteroids due to their prolonged contact with the eye. However, the lipophilic nature of corticosteroids hampers CLs' ability to release therapeutic amounts. Two approaches to improve loading and release of triamcinolone acetonide (TA) from poly(2-hydroxyethyl methacrylate)-based hydrogels were investigated: adding 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) to the monomers solution before polymerization (HEMA/i-CD) and an hydrogels' post-treatment with HP-β-CD (HEMA/p-CD). The effect of HP-β-CD and sterilization by high hydrostatic pressure (HHP) on the hydrogel properties (water content, oxygen and ion permeability, roughness, transmittance, and stiffness) was evaluated. The HEMA/i-CD hydrogels had stronger affinity for TA, sustaining its release for one day. HHP sterilization promoted the formation of cyclodextrin-TA complexes within the hydrogels, improving their drug-loading capacity »60 %. Cytotoxicity and irritability tests confirmed the safety of the therapeutic CLs. TA released from the hydrogels permeated through ocular tissues ex vivo and showed anti-inflammatory activity. Finally, a previously validated mathematical model was used to estimate the ability of the TA-loaded CLs to deliver therapeutic drug concentrations to the posterior part of the eye. Overall, HP-β-CD-containing CLs are promising candidates for the topical ocular application of TA as an alternative delivery system to intraocular injections.

Polysaccharide-based hydrogels for medical devices, implants and tissue engineering: A review

Hydrogels are highly biocompatible biomaterials composed of crosslinked three-dimensional networks of hydrophilic polymers. Owing to their natural origin, polysaccharide-based hydrogels (PBHs) possess low toxicity, high biocompatibility and demonstrate in vivo biodegradability, making them great candidates for use in various biomedical devices, implants, and tissue engineering. In addition, many polysaccharides also show additional biological activities such as antimicrobial, anticoagulant, antioxidant, immunomodulatory, hemostatic, and anti-inflammatory, which can provide additional therapeutic benefits. The porous nature of PBHs allows for the immobilization of antibodies, aptamers, enzymes and other molecules on their surface, or within their matrix, potentiating their use in biosensor devices. Specific polysaccharides can be used to produce transparent hydrogels, which have been used widely to fabricate ocular implants. The ability of PBHs to encapsulate drugs and other actives has been utilized for making neural implants and coatings for cardiovascular devices (stents, pacemakers and venous catheters) and urinary catheters. Their high water-absorption capacity has been exploited to make superabsorbent diapers and sanitary napkins. The barrier property and mechanical strength of PBHs has been used to develop gels and films as anti-adhesive formulations for the prevention of post-operative adhesion. Finally, by virtue of their ability to mimic various body tissues, they have been explored as scaffolds and bio-inks for tissue engineering of a wide variety of organs. These applications have been described in detail, in this review.

Polysaccharides in contact lenses: From additives to bulk materials

As the number of applications has increased, so has the demand for contact lenses comfort. Adding polysaccharides to lenses is a popular way to enhance comfort for wearers. However, this may also compromise some lens properties. It is still unclear how to balance the variation of individual lens parameters in the design of contact lenses containing polysaccharides. This review provides a comprehensive overview of how polysaccharide addition impacts lens wear parameters, such as water content, oxygen permeability, surface wettability, protein deposition, and light transmittance. It also examines how various factors, such as polysaccharide type, molecular weight, amount, and mode of incorporation into lenses modulate these effects. Polysaccharide addition can improve some wear parameters while reducing others depending on the specific conditions. The optimal method, type, and amount of added polysaccharides depend on the trade-off between various lens parameters and wear requirements. Simultaneously, polysaccharide-based contact lenses may be a promising option for biodegradable contact lenses as concerns regarding environmental risks associated with contact lens degradation continue to increase. It is hoped that this review will shed light on the rational use of polysaccharides in contact lenses to make personalized lenses more accessible.

Long-term effects of tear film component deposition on the surface and optical properties of two different orthokeratology lenses

PURPOSE

To understand the effects of long-term deposition of tear film components on the surface and optical properties of orthokeratology (ortho-k) lenses, two different lenses, Brighten 22 and Optimum Extra, were tested here.

METHODS

Ortho-k lenses were immersed in artificial tears and cleaned with a commercial care solution repeatedly for up to 90 days. Both the daily and accumulated lysozyme deposition amounts using an Enzyme-Linked ImmunoSorbent Assay were then analyzed. The base curve, central thickness, power, and transmission of visible light, ultraviolet A, and ultraviolet B were analyzed before and after repeated tear film component deposition procedures. The surface roughness using atomic force microscopy was observed and an energy dispersive spectrometer was used to analyze the composition of the deposits.

RESULTS

The highest levels of lysozyme were adsorbed on both lens materials during the first four days of the procedure and became saturated by day 6. For both lens materials, contamination on the lenses was easily observed by day 30, and the degree of surface roughness was higher. The transmission levels of different light spectrums were reduced showing that the optical characteristics of both lenses were also affected.

CONCLUSIONS

The results provide in vitro evidence that lysozyme could not be completely removed from orthokeratology lenses. Both surface and optical properties were affected by the deposition of tear film components. However, only one commercial multipurpose care solution was used to clean the lens in this study when the main ingredient was a surfactant, and the results might be different when other care regimens with other key ingredients are used. In addition, whether tear film component deposition might result in increased risks of infection or corneal abrasion will require further investigation.

Nutrient Supplementation Improves Contact Lens-Induced Corneal Cell Damage Based on a SIRC Cellular Model

OBJECTIVES

The long-term use of contact lenses may damage the structure of the ocular surface and cause metabolic disorders in corneal cells. Vitamins and amino acids help maintain the physiological function of the eye. In the present study, the effects of nutrient (vitamin and amino acid) supplementation on corneal cell repair after contact lens-induced damage was investigated.

METHODS

High-performance liquid chromatography was used to quantify the nutrient contents of minimum essential medium, and the MTT assay was used to measure the viability of corneal cells. A Statens Seruminstitut rabbit cornea cellular model was established to simulate contact lens-induced keratopathy and investigate the effects of vitamin and amino acid supplementations on corneal cell repair.

RESULTS

The high water content lens group (78%) has a cell viability as high as 83.3%, whereas the cell viability of the low water content lens group (38%) is only 51.6%. The 32.0% difference between the two groups confirms the correlation between water content of lens and corneal viability.

CONCLUSIONS

Vitamin B2, vitamin B12, asparagine, and taurine supplementation may help improve contact lens-induced damage.

Nonfouling and Antibacterial Zwitterionic Contact Lenses Loaded with Heme-Mimetic Gallium Porphyrin for Treating Keratitis

Antifouling and antibacterial are two critical challenges in the development of contact lenses (CLs). Herein, we presented nonfouling and antibacterial bifunctionalized CLs by encapsulating cationic heme-mimetic gallium porphyrin (Ga-CHP) into zwitterionic-elastomeric-networked (ZEN) hydrogel. Results proved that the ZEN hydrogel showed excellent abilities to resist non-specific protein adsorption, bacterial adhesion, and biofilm formation. Moreover, Ga-CHP could be sustainably released and kill >99.9% planktonic bacteria and >99.9% mature biofilms. In vivo, the symptoms of bacterial keratitis in mice were significantly alleviated after wearing the CLs for 7 days via iron-blocking and photodynamic synergistic antibacterial therapy with the help of natural sunlight. This study highlights the nonfouling and antibacterial superiority of the Ga-CHP-functional zwitterionic CLs and proposes a portable yet efficient non-antibiotic keratitis treatment strategy.

In vitro and in vivo evaluation of brimonidine loaded silica nanoparticles-laden silicone contact lenses to manage glaucoma

Glaucoma is treated by frequent instillation of 0.2% w/v brimonidine tartrate eye drop solution, which showed poor ocular bioavailability of 1-3%. Medicated contact lenses can be used to improve the ocular drug bioavailability. However, drug loading in the contact lens matrix showed high burst release and changes the optophysical properties of the contact lens material. In this paper, a novel brimonidine loaded silica nanoparticles-laden silicone contact lenses (Bri-Si) were designed to achieve controlled drug delivery without altering the optophysical properties of the contact lens. Silica nanoparticles were prepared by polymerizing octadecyltrimethoxysilane (OTMS) molecules at the oil/water interface of microemulsion. Traditional soaking method (Bri-SM), direct brimonidine-loading method (Bri-DL) and microemulsion-laden contact lens (Bri-ME) were developed for comparison. The Bri-Si lens showed improved swelling, transmittance, oxygen permeability and lysozyme adherence compared to Bri-SM, Bri-DL and Bri-ME lenses. The Bri-DL lens showed high brimonidine leaching during extraction and sterilization steps, with low cumulative drug release. While, Bri-Si lens show controlled brimonidine release for 144 h. In a rabbit tear fluid model, the Bri-Si lens showed high brimonidine concentration for 96 h compared to Bri-ME lens and eye drop therapy. Based on histopathological studies of cornea, the Bri-Si lens was found to be safe for human applications. The data demonstrated the novel application of silica nanoparticles to control brimonidine release from the contact lens without altering the optophysical properties of the contact lens.

A SiO2/pHEMA-Based Polymer-Infiltrated Ceramic Network Composite for Dental Restorative Materials

SiO2-poly(2-hydroxyethyl methacrylate) (pHEMA)-based composites have been widely used as biomaterials owing to their biocompatibility. However, they have not yet been applied as tooth restorative materials because of their poor mechanical properties. In the present paper, we develop a novel SiO2/pHEMA-based composite with a polymer-infiltrated network (PICN) structure for use in dental restorative materials. A mixture of SiO2 nanoparticles and a poly(vinyl alcohol) binder was sintered at 950 °C to fabricate a porous SiO2 block. A monomer mixture containing 70 wt%-HEMA/30 wt%-ethylene glycol dimethacrylate and a benzoyl peroxide initiator was infiltrated into the porous SiO2 block and heat-polymerized to fabricate the SiO2/pHEMA-based composite with a PICN structure. The composite was characterized according to its mechanical properties, surface free energy, and bonding properties with a dental adhesive. The flexural strength was 112.5 ± 18.7 MPa, the flexural modulus was 13.6 ± 3.4 GPa, and the Vickers hardness was 168.2 ± 16.1, which are similar values to human teeth. The surface free energy of the polar component of the composite was 19.6 ± 2.5 mN/m, suggesting that this composite has an active surface for bonding with the adhesive. The composite bonded well to the adhesive, in the presence of a silane coupling agent. The SiO2/pHEMA-based composite was demonstrated to be a potential candidate for dental restorative materials.

Development of an enzymatic method for the evaluation of protein deposition on contact lenses

The aim of this study was to evaluate a new digestion method to quantify protein deposition on contact lenses. Four silicone hydrogel and one hydrogel contact lens material were incubated in lactoferrin, lysozyme, immunoglobulin A, and bovine serum albumin solutions at approximate physiological concentrations and temperature. Immobilized trypsin was used to digest the protein deposits from the contact lens surfaces. The total protein absorbed to lenses was extracted and digested using sequencing grade trypsin. The tryptic peptides were quantified using selected reaction monitoring mass spectrometry. The concentration of surface protein deposits was either lower than or the same as the total protein for all lens types and proteins. Immobilised trypsin can digest protein deposits from the surface of contact lenses. This ability to analyse the amount of protein at a contact lens surface may help in elucidating the effect of surface deposition on clinical outcomes during lens wear.

Evaluation of Pollen Adhesion to Verofilcon-A Soft Contact Lenses

Purpose:

A new 1-day disposable soft contact lens (SCL), verofilcon-A, constructed of silicone hydrogel material, has recently become available in Japan. This SCL has a very smooth surface produced by using the SMARTSURFACE ® Technology, and it was expected that pollen particles and protein components would not adhere easily to its surface. We examined the degree of pollen adhesion to the surface of the verofilcon-A material SCL and compared the results with those of other 1-day disposable SCLs (1DSCL).

Methods:

To determine the number of pollen grains attached to the surface of different types of SCLs, 0.01 mg/ml of cedar pollen solution was dropped onto the surface of 13 types of 1DSCL. After 24 h, each 1DSCL was rinsed in a shaker and washed five times with saline (n = 10 for each 1DSCL type). The number of pollen particles adhered to the 1DSCL and the percentage of surface area occupied by pollen was determined.

Results:

The number of pollen particles on the 1DSCLs ranged from 0 to 185 in the 200 × 200 µm area. The number of particles was lowest in the delefilcon-A and verofilcon-A SCLs with 0 particles, and the number was higher in the other 11 1DSCLs. The number of pollen particles was negatively correlated with the water content (r = −0.48), oxygen permeability (Dk; r = −0.43), oxygen transmissibility (r = −0.42), and center thickness (r = −0.33) of the 1DSCLs. The pollen adhesion area ranged from 0.0% to 3.1% and was lowest in the delefilcon-A and verofilcon-A 1DSCLs. There were significant differences in the pollen adhesion area between colored 1DSCLs (2.73 ± 1.97%) and clear 1DSCLs (1.03 ± 1.01%, P<0.001) and between hydroxyethyl methacrylate-based 1DSCLs (1.84 ± 1.45%) and silicone hydrogel-based 1DSCLs (0.05 ± 0.16%, P<0.001).

Conclusion:

These findings indicate that the verofilcon-A 1DSCL processed with SMARTSURFACE™ Technology is an excellent option for SCL users with allergic conjunctivitis during the high pollen season.

Bimatoprost-Loaded Silica Shell-Coated Nanoparticles-Laden Soft Contact Lenses to Manage Glaucoma: In Vitro and In Vivo Studies

Currently, glaucoma is managed by frequent instillation of bimatoprost eye drop therapy, which showed very poor ocular bioavailability. Contact lens is widely used as medical device to improve the drug retention on the ocular tissues. However, the traditional methods of drug loading in the contact lens matrix showed high burst release and changes the optophysical properties of the contact lens material. In this paper, a novel bimatoprost-loaded silica shell nanoparticles-laden soft contact lenses were developed to achieve sustain drug delivery without altering the optophysical properties of the contact lens. Silica-shell nanoparticles were prepared using octyltrimethoxysilane (OTMS) and microemulsion. Traditional soaking method (SM-BT), direct bimatoprost loading method (DL-BT), and microemulsion-laden contact lens (ME-BT) were developed for comparison. The silica shell-coated nanoparticles-laden soft contact lenses (SiS-BT) showed improved swelling, transmittance, oxygen permeability, and lysozyme adherence compared to SM-BT, DL-BT, and ME-BT lenses. The DL-BT and ME-BT batch showed high bimatoprost lost/leaching during extraction and sterilization steps, with low cumulative drug release. Also, SiS-BT lens showed sustain bimatoprost release for 96 h. In a rabbit tear fluid model, the SiS-BT lens showed high bimatoprost concentration for 72 h compared to ME-BT lens and eye drop therapy. Based on histopathological studies of cornea, the SiS-BT lens was found to be safe for human applications. The data demonstrated the novel application of silica shell nanoparticles to deliver bimatoprost from the contact lens for extended period of time without altering the optophysical properties of the contact lens.

The Effect of Different Cleaning Methods on Protein Deposition and Optical Characteristics of Orthokeratology Lenses

Orthokeratology lenses are commonly used for myopia control, especially in children. Tear lipids and proteins are immediately adsorbed when the lens is put on the cornea, and protein deposition may cause discomfort or infection. Therefore, we established an in vitro protein deposition analysis by mimicking the current cleaning methods for orthokeratology lens wearers for both short-term and long-term period. The results showed that the amounts of tear proteins accumulated daily and achieved a balance after 14 days when the lens was rubbed to clean or not. Protein deposition also affected the optical characteristics of the lens regardless of cleaning methods. Our results provided an in vitro analysis for protein deposition on the lens, and they may provide a potential effective method for developing care solutions or methods that can more effectively remove tear components from orthokeratology lenses.

Correlation between surface friction and the hydrophobicity of structure-related side-chain exposure of albumin on contact lens

The management of contact lens discomfort remains a challenge leading to the increased contact lens dropout rates. Tear protein accumulates on the lens surfaces with different configurations observed are correlated to the lens friction, with the improved comfort experienced by reduced surface friction in the eye. However, protein adsorption is a complex process with the combined protein-protein interactions (PPI) and protein-surface interactions (PSI) involved, which is difficult to explain the complicated tribological behavior in terms of protein structural shifts alone on lens surfaces. On the other hand, the type of solvent-exposed side chains from specific protein conformations on lens surfaces should be more important to the lens friction involved. We aim to investigate the correlation between the structure-related side-chain exposure and corresponding lens friction of adsorbed tear proteins on lens surfaces under varied PPI and PSI. Albumin was the model protein adsorbed onto the conventional lens material. Such as polymethylmethacrylate (PMMA) or the poly-2-hydroxyethyl methacrylate (PHEMA) surfaces applied here. Adsorption was conducted under varying protein solution concentrations to saturate the model surface to change the PPI effects over a wide range. Our results indicate that PPI effects help stabilize protein structures on both surfaces. When PPI is minimized, a distinct correlation was observed between the surface friction and the hydrophobicity of structure-related side-chain exposure of albumin on lens surfaces depending on the different PSI involved. At a fundamental understanding, our results would provide insights for developing new lens materials or the lens care solution designs to reduce the lens discomfort.

Evaluation of silicone hydrogel contact lenses based on poly(dimethylsiloxane) dialkanol and hydrophilic polymers

Silicone hydrogel lenses were prepared by copolymerizing PDMS-PEGMA macromer (PGP) with various combinations of DMA, NVP, and PEGMA through UV initiated polymerization process. The resultant PGP macromer were characterized by gel permeation chromatography (GPC), and scanning electron microscope (SEM-EDS). Characterization of all the resultant co-polymers included Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), equilibrium water content (EWC), oxygen permeability (Dk), optical transparency, contact angle, mechanical properties, zeta potential, protein deposition, and cytotoxicity. The results show that higher content of hydrophilic polymers increased water uptake ability as well as improved hydrophilicity and modulus of silicone hydrogel lenses; however, oxygen permeability decreased with the decrease of PDMS content (145 barrers of PGP to 37 barrers of DP0). In addition, these silicone hydrogel lenses exhibited relatively optical transparency, anti-protein deposition, and non-cytotoxic according to an in vitro L929 fibroblast assay. Therefore, these silicone hydrogel polymers would be applicable for making contact lens.

Albumin Acts as a Lubricant on the Surface of Hydrogel and Silicone Hydrogel Contact Lenses

Feeling comfortable is the greatest concern for contact lens wearers, and it has been suggested that in vivo comfort could be corresponded to the in vitro friction coefficient of contact lenses. How tear albumin could affect the friction coefficient of silicone hydrogel and hydrogel contact lenses was analyzed by sliding a lens against a quartz glass in normal and extremely high concentration of albumin solution. Albumin deposition testing and surface roughness analysis were also conducted. The results showed that the friction coefficient of tested contact lenses did not correspond to both the albumin deposition amount and surface roughness, but we proposed a model of how albumin might act as a lubricant on the surface of some hydrogel and silicone hydrogel contact lenses. In conclusion, albumin provided lubrication for silicone hydrogel contact lenses regardless of albumin concentrations, while albumin only acted as a lubricant for hydrogel contact under normal concentration.

Adhesion of Pollen Particles to Daily Disposable Soft Contact Lenses

PURPOSE

Pollen and proteins attached to soft contact lenses (SCLs) exacerbate allergic conjunctivitis. The material of SCLs may affect the pollen adhesion to the SCLs. The factors associated with the number of pollen particles that are adherent to daily disposable SCL were investigated.

METHODS

Pollen particles were experimentally exposed to the contact lens surface of 12 types of SCLs for 1 hour, and the SCLs were washed and rinsed with a physiological saline (n=10 for each SCL type). A total of 120 contact lenses were used in this study. The pollen particles attached to the SCL were observed and photographed under a microscope. The influence of the materials of the SCLs on the degree of pollen adhesion were investigated.

RESULTS

The number of residual pollen particles attached to SCLs was in the range from 0-293/area of 200×200 µm. Percentage of pollen adhesion area of the surface of the SCL was in the range from 0.01% to 3.25%. There were significant differences in both the number and adhesion area of pollen particles among the 12 types of SCLs tested (P<0.0001 and P<0.0001, respectively). The number of pollen particles adhered to SCLs was significantly higher in colored SCLs than clear SCLs (unpaired t-test, p<0.001). The portion of pollen adhesion area was the lowest in the silicone hydrogel SCLs made with delefilcon-A (0.01 ± 0.02%).

CONCLUSION

Pollen adhesion in daily disposable SCLs depends on the characteristics and materials of the SCLs and was high in colored SCLs and lowest in delefilcon-A silicone hydrogel SCL. These results suggest that colored SCLs are not preferred during pollen season.

Thirty years of 'quiet eye' with etafilcon A contact lenses

Frequent replacement contact lenses made from the etafilcon A hydrogel lens material were introduced onto the market over 30 years ago, and etafilcon A remains the most widely used hydrogel lens material today. Although the prescribing of silicone hydrogel lenses is increasing, millions of lens wearers globally have been wearing hydrogel lenses for many years and exhibit a physiologically-stable 'quiet eye', with a low profile of adverse events. Hydrogel lenses are demonstrated to maintain a low inflammatory response and infection risk profile during daily wear, which in the case of etafilcon A, may be related to its low modulus, and the naturally-protective, anti-microbial, non-denatured lysozyme absorbed into the lens from the tear fluid. Although improved corneal physiology from decreased hypoxia with silicone hydrogel lenses is well accepted, equivalent levels of corneal oxygenation are maintained during daily wear of low to medium powered hydrogel lenses, which do not impede the daily corneal de-swelling process, and do not induce clinically significant changes in ocular health. Therefore, hydrogel lenses remain an important alternative for daily wear in modern contact lens practice.

Stable Fabrication of Zwitterionic Coating Based on Copper-Phenolic Networks on Contact Lens with Improved Surface Wettability and Broad-Spectrum Antimicrobial Activity

Ocular dryness and contact lens(CL)-related microbial keratitis (MK) are two major risks of wearing CLs. The development of multifunctional surface coating for CLs with excellent hydrating and antimicrobial properties is a practical strategy to improve the comfort of CL wearers and to prevent corneal infection. Here, we develop zwitterionic and antimicrobial metal-phenolic networks (MPNs) based on the coordination of copper ions (Cu^II) and the poly(carboxylbetaine-co-dopamine methacrylamide) copolymer (PCBDA), which can be easily one-step prepared onto CLs due to the near-universal adherent properties of catechol groups. The zwitterionic and antifouling carboxybetaine (CB) groups of the Cu^II-PCBDA coating can significantly increase the wettability of CLs and reduce their protein adsorptions, resulting in a lens surface that is more water retentive and with lower protein binding to prevent tear film evaporation and eye dryness. In addition, since the immobilized copper ions in the MPNs impart them with ion-mediated antimicrobial activity, the Cu^II-PCBDA coating exhibits a strong and broad-spectrum antimicrobial activity against MK related pathogenic microbes, including bacteria, such as Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, and fungi, such as Candida albicans. Compared with a pristine CL, the Cu^II-PCBDA-coated CL effectively inhibited biofilm formation even after daily exposure to the above microbial environment for 14 days. Notably, the Cu^II-PCBDA coating developed in this study is not only biocompatible with 100% cell viability following direct contact with human corneal epithelial cells (HCECs) for 48 h but also maintains the optical clarity of the native CLs. Thus, the Cu^II-PCBDA coating has a great application potential for the development of a multifunctional surface coating for CLs for increased CL comfort and prevention of MK.

Synthesis and Characterization of Silicone Contact Lenses Based on TRIS-DMA-NVP-HEMA Hydrogels

In this study, silicone-based hydrogel contact lenses were prepared by the polymerization of 3-(methacryloyloxy)propyltris(trimethylsiloxy)silane (TRIS), N,N-dimethylacrylamide (DMA), 1-vinyl-2-pyrrolidinone (NVP), and 2-hydroxyethylmethacrylate (HEMA). The properties of silicone hydrogel lenses were analyzed based on the methods such as equilibrium water content, oxygen permeability, optical transparency, contact angle, mechanical test, protein adsorption, and cell toxicity. The results showed that the TRIS content in all formulations increased the oxygen permeability and decreased the equilibrium water content, while both DMA and NVP contributed the hydrophilicity of the hydrogels. The maximum value of oxygen permeability was 74.9 barrers, corresponding to an equilibrium water content of 44.5% as well as a contact angle of 82°. Moreover, L929 fibroblasts grew on all these hydrogels, suggesting non-cytotoxicity. In general, the silicone hydrogels in this work exhibited good oxygen permeability, stiffness, and optical transparency as well as anti-protein adsorption. Hence, these silicone hydrogel polymers would be feasible for making contact lens.

Transport-Limited Adsorption of Plasma Proteins on Bimodal Amphiphilic Polymer Co-Networks: Real-Time Studies by Spectroscopic Ellipsometry

Traditional hydrogels are commonly limited by poor mechanical properties and low oxygen permeability. Bimodal amphiphilic co-networks (β-APCNs) are a new class of materials that can overcome these limitations by combining hydrophilic and hydrophobic polymer chains within a network of co-continuous morphology. Applications that can benefit from these improved properties include therapeutic contact lenses, enzymatic catalysis supports, and immunoisolation membranes. The continuous hydrophobic phase could potentially increase the adsorption of plasma proteins in blood-contacting medical applications and compromise in vivo material performance, so it is critical to understand the surface characteristics of β-APCNs and adsorption of plasma proteins on β-APCNs. From real-time spectroscopic visible (Vis) ellipsometry measurements, plasma protein adsorption on β-APCNs is shown to be transport-limited. The adsorption of proteins on the β-APCNs is a multistep process with adsorption to the hydrophilic surface initially, followed by diffusion into the material to the internal hydrophilic/hydrophobic interfaces. Increasing the cross-linking of the PDMS phase reduced the protein intake by limiting the transport of large proteins. Moreover, the internalization of the proteins is confirmed by the difference between the surface-adsorbed protein layer determined from XPS and bulk thickness change from Vis ellipsometry, which can differ up to 20-fold. Desorption kinetics depend on the adsorption history with rapid desorption for slow adsorption rates (i.e., slow-diffusing proteins within the network), whereas proteins with fast adsorption kinetics do not readily desorb. This behavior can be directly related to the ability of the protein to spread or reorient, which affects the binding energy required to bind to the internal hydrophobic interfaces.

"Click" Chemistry-Tethered Hyaluronic Acid-Based Contact Lens Coatings Improve Lens Wettability and Lower Protein Adsorption

Improving the wettability of and reducing the protein adsorption to contact lenses may be beneficial for improving wearer comfort. Herein, we describe a simple "click" chemistry approach to surface functionalize poly(2-hydroxyethyl methacrylate) (pHEMA)-based contact lenses with hyaluronic acid (HA), a carbohydrate naturally contributing to the wettability of the native tear film. A two-step preparation technique consisting of laccase/TEMPO-mediated oxidation followed by covalent grafting of hydrazide-functionalized HA via simple immersion resulted in a model lens surface that is significantly more wettable, more water retentive, and less protein binding than unmodified pHEMA while maintaining the favorable transparency, refractive, and mechanical properties of a native lens. The dipping/coating method we developed to covalently tether the HA wetting agent is simple, readily scalable, and a highly efficient route for contact lens modification.

Incorporation of ultraviolet (UV) absorbing nanoparticles in contact lenses for Class 1 UV blocking

UV blocking nanoparticles 10 to 1000 nm in diameter have been created by polymerization of emulsions and loaded into contact lens materials.

The effect of albumin and cholesterol on the biotribological behavior of hydrogels for contact lenses

The irritation/discomfort associated with the use of contact lenses (CLs) is often related to the eyelid-lens friction. Although the use of such devices is widespread, the information about the influence of the lacrimal fluid biomolecules on the tribological behavior of the CLs hydrogels is scarce. In this work, we investigated the effect of the presence of albumin and cholesterol in the lubricant medium, on the frictional response of two model hydrogels for CLs: a hydroxyethylmethacrylate based hydrogel, HEMA/PVP, and a silicone based one, TRIS/NVP/HEMA. Tribological experiments were done in a nanotribometer, in water and in the presence of solutions of those biomolecules. It was observed a significant increase of the friction coefficient (μ) for HEMA/PVP when the lubricant contains cholesterol, and for TRIS/NVP/HEMA when it contains albumin. Solid-state NMR and DSC analysis revealed that HEMA/PVP hydrated in cholesterol solution has a lower amount of free and loosely bound water than the hydrogel hydrated in water. Therefore, a smaller amount of water shall be released into the contact region during the friction tests with cholesterol solution, leading to a thinner film in the contact zone, and consequently to a higher μ. Concerning TRIS/NVP/HEMA, QCM-D studies showed that this hydrogel adsorbs less albumin than HEMA/PVP and that the formed film is more rigid, which can explain the increase of μ. The obtained results contribute to understand the influence of lacrimal fluid composition on the tribological behavior of CLs materials, being relevant for the selection and optimization of these devices.

STATEMENT OF SIGNIFICANCE

Understanding the tribological behavior of contact lenses (CLs) materials in contact with the lacrimal fluid and the role of its components is of major importance to optimize the comfort and overall success of these devices. Nevertheless, the available information on this subject in the literature is scarce. In this work, the effect of albumin and cholesterol (two of the main components of the lacrimal fluid) on the frictional response of distinct types of hydrogels suitable for CLs, is compared, for the first time. Significant differences were observed with the two molecules, depending on the material, stressing the need to further study this issue to understand, predict and optimize the in vivo performance of CLs.

Self-assembling peptide-enriched electrospun polycaprolactone scaffolds promote the h-osteoblast adhesion and modulate differentiation-associated gene expression

Electrospun polycaprolactone (PCL) is able to support the adhesion and growth of h-osteoblasts and to delay their degradation rate to a greater extent with respect to other polyesters. The drawbacks linked to its employment in regenerative medicine arise from its hydrophobic nature and the lack of biochemical signals linked to it. This work reports on the attempt to add five different self-assembling (SA) peptides to PCL solutions before electrospinning. The hybrid scaffolds obtained had regular fibers (SEM analysis) whose diameters were similar to those of the extracellular matrix, more stable hydrophilic (contact angle measurement) surfaces, and an amorphous phase constrained by peptides (DSC analysis). They appeared to have a notable capacity to promote the h-osteoblast adhesion and differentiation process by increasing the gene expression of alkaline phosphatase, bone sialoprotein, and osteopontin. Adding an Arg-Gly-Asp (RGD) motif to a self-assembling sequence was found to enhance cell adhesion, while the same motif condensed with a scrambled sequence did not, indicating that there is a cooperative effect between RGD and 3D architecture created by the self-assembling peptides. The study demonstrates that self-assembling peptide scaffolds are still able to promote beneficial effects on h-osteoblasts even after they have been included in electrospun polycaprolactone. The possibility of linking biochemical messages to self-assembling peptides could lead the way to a 3D decoration of fibrous scaffolds.

Infection of orthopedic implants with emphasis on bacterial adhesion process and techniques used in studying bacterial-material interactions

Staphylococcus comprises up to two-thirds of all pathogens in orthopedic implant infections and they are the principal causative agents of two major types of infection affecting bone: septic arthritis and osteomyelitis, which involve the inflammatory destruction of joint and bone. Bacterial adhesion is the first and most important step in implant infection. It is a complex process influenced by environmental factors, bacterial properties, material surface properties and by the presence of serum or tissue proteins. Properties of the substrate, such as chemical composition of the material, surface charge, hydrophobicity, surface roughness and the presence of specific proteins at the surface, are all thought to be important in the initial cell attachment process. The biofilm mode of growth of infecting bacteria on an implant surface protects the organisms from the host immune system and antibiotic therapy. The research for novel therapeutic strategies is incited by the emergence of antibiotic-resistant bacteria. This work will provide an overview of the mechanisms and factors involved in bacterial adhesion, the techniques that are currently being used studying bacterial-material interactions as well as provide insight into future directions in the field.

Adsorptive properties of albumin, fibrinogen, and gamma-globulin on fluorinated diamond-like carbon films coated on PTFE

Fluorinated diamond-like carbon (F-DLC) films were deposited on polytetrafluoroethylene (PTFE) using radio frequency (RF) plasma-enhanced chemical vapor deposition (CVD) by changing the ratio of tetrafluoromethane (CF(4)) and methane (CH(4)). To enhance the adhesion strength of the F-DLC film to the PTFE substrate, the PTFE surface was modified with a N(2) plasma pre-treatment. XPS analysis of the films showed that the C-C bond decreased with increases in the CF(4) ratio, whereas the C-F bond increased with the CF(4) ratio. The F/C ratio of the film also increased with the CF(4) ratio. The pull-out test showed that the adhesion strengths of the films (CF(4)-0-60%) were improved with the plasma pre-treatment. In the film without the plasma pre-treatment, adhesion strength increased with the CF(4) ratio. In contrast, in the case with the plasma pre-treatment, the adhesion strength of the F-DLC film decreased with the increased CF(4) ratio. Regarding the adsorption of albumin, fibrinogen, and gamma-globulin, the amount of adsorbed albumin on the film decreased with an increasing CF(4) ratio, and the amount of adsorbed fibrinogen and gamma-globulin increased with the CF(4) ratio. The CF(4)-0% DLC film showed the most adsorbed albumin and the least adsorbed fibrinogen and gamma-globulin. This indicates that the CF(4)-0% DLC film has higher anti-thrombogenicity than the F-DLC film.