Fabricating customized hydrogel contact lens

Quantifying the Dynamics of Bacterial Biofilm Formation on the Surface of Soft Contact Lens Materials Using Digital Holographic Tomography to Advance Biofilm Research

The increase in bacterial resistance to antibiotics in recent years demands innovative strategies for the detection and combating of biofilms, which are notoriously resilient. Biofilms, particularly those on contact lenses, can lead to biofilm-related infections (e.g., conjunctivitis and keratitis), posing a significant risk to patients. Non-destructive and non-contact sensing techniques are essential in addressing this threat. Digital holographic tomography emerges as a promising solution. This allows for the 3D reconstruction of the refractive index distribution in biological samples, enabling label-free visualization and the quantitative analysis of biofilms. This tool provides insight into the dynamics of biofilm formation and maturation on the surface of transparent materials. Applying digital holographic tomography for biofilm examination has the potential to advance our ability to combat the antibiotic bacterial resistance crisis. A recent study focused on characterizing biofilm formation and maturation on six soft contact lens materials (three silicone hydrogels, three hydrogels), with a particular emphasis on Staphylococcus epidermis and Pseudomonas aeruginosa, both common culprits in ocular infections. The results revealed species- and time-dependent variations in the refractive indexes and volumes of biofilms, shedding light on cell dynamics, cell death, and contact lens material-related factors. The use of digital holographic tomography enables the quantitative analysis of biofilm dynamics, providing us with a better understanding and characterization of bacterial biofilms.

Correlation between corneal and contact lens deformation with changes in intraocular pressure for wearable monitoring systems

OBJECTIVE

The aim of this work is to evaluate the extent to which the eye's curvature deformation, due to changes in the intraocular pressure (IOP), can be directly tracked by an overlying contact lens.

METHOD

In this experimental study, using 12 cadaveric eyes, the IOP was increased from 10 to 36 mmHg, while video imaging was used to capture the three experimental variations. The deformation of the bare eye was used as a control, while the deformation of an overlying silicone grided contact lens and an overlying microfluidic IOP-sensing contact lens were examined and compared.

RESULTS

The relation between the slope of the radius of corneal curvature versus the IOP for both the bare eye and the marker contact lens yielded a linear relationship with a R2 value of 0.83. The microfluidic contact lens resulted in an average performance of 0.40 mm indicator movement/mmHg (SD 0.006). Comparing the slope of the marker contact lens deformation, to the performance of the microfluidic contact lens resulted in a R2 value of 0.78. The strain map of the overlaying grided contact lens showed most deformation occurring along the outer edge of the lens with increased deformation as increase IOP occurs; as well as with some negative, compressive movement near the central points.

CONCLUSION

The deformation from the curvature of the eye is significant enough from 10 to 36 mmHg that a silicone contact lens can capture and mimic those changes. The results show promise for optimization in contact lens-based IOP monitoring.

Transparent tissue in solid state for solvent-free and antifade 3D imaging

Optical clearing with high-refractive-index (high-n) reagents is essential for 3D tissue imaging. However, the current liquid-based clearing condition and dye environment suffer from solvent evaporation and photobleaching, causing difficulties in maintaining the tissue optical and fluorescent features. Here, using the Gladstone-Dale equation [(n-1)/density=constant] as a design concept, we develop a solid (solvent-free) high-n acrylamide-based copolymer to embed mouse and human tissues for clearing and imaging. In the solid state, the fluorescent dye-labeled tissue matrices are filled and packed with the high-n copolymer, minimizing scattering in in-depth imaging and dye fading. This transparent, liquid-free condition provides a friendly tissue and cellular environment to facilitate high/super-resolution 3D imaging, preservation, transfer, and sharing among laboratories to investigate the morphologies of interest in experimental and clinical conditions.

Synthesis of NVCL-NIPAM Hydrogels Using PEGDMA as a Chemical Crosslinker for Controlled Swelling Behaviours in Potential Shapeshifting Applications

Stimuli-responsive hydrogels have recently gained interest within shapeshifting applications due to their capabilities to expand in water and their altering swelling properties when triggered by stimuli, such as pH and heat. While conventional hydrogels lose their mechanical strength during swelling, most shapeshifting applications require materials to have mechanical strength within a satisfactory range to perform specified tasks. Thus, stronger hydrogels are needed for shapeshifting applications. Poly (N-isopropylacrylamide) (PNIPAm) and poly (N-vinyl caprolactam) (PNVCL) are the most popular thermosensitive hydrogels studied. Their close-to-physiological lower critical solution temperature (LCST) makes them superior candidates in biomedicine. In this study, copolymers made of NVCL and NIPAm and chemically crosslinked using poly (ethylene glycol) dimethacrylate (PEGDMA) were fabricated. Successful polymerisation was proven via Fourier transform infrared spectroscopy (FTIR). The effects of incorporating comonomer and crosslinker on the LCST were found minimal using cloud-point measurements, ultraviolet (UV) spectroscopy, and differential scanning calorimetry (DSC). Formulations that completed three cycles of thermo-reversing pulsatile swelling are demonstrated. Lastly, rheological analysis validated the mechanical strength of PNVCL, which was improved due to the incorporation of NIPAm and PEGDMA. This study showcases potential smart thermosensitive NVCL-based copolymers that can be applied in the biomedical shapeshifting area.

A hydrogel-based mechanical metamaterial for the interferometric profiling of extracellular vesicles in patient samples

The utility of mechanical metamaterials for biomedical applications has seldom been explored. Here we show that a metamaterial that is mechanically responsive to antibody-mediated biorecognition can serve as an optical interferometric mask to molecularly profile extracellular vesicles in ascites fluid from patients with cancer. The metamaterial consists of a hydrogel responsive to temperature and redox activity functionalized with antibodies to surface biomarkers on extracellular vesicles, and is patterned into micrometric squares on a gold-coated glass substrate. Through plasmonic heating, the metamaterial is maintained in a transition state between a relaxed form and a buckled state. Binding of extracellular vesicles from the patient samples to the antibodies on the hydrogel causes it to undergo crosslinking, induced by free radicals generated via the activity of horseradish peroxidase conjugated to the antibodies. Hydrogel crosslinking causes the metamaterial to undergo fast chiral re-organization, inducing amplified changes in its mechanical deformation and diffraction patterns, which are detectable by a smartphone camera. The mechanical metamaterial may find broad utility in the sensitive optical immunodetection of biomolecules.

Formulation development and evaluation of therapeutic contact lens loaded with ganciclovir

PURPOSE

In the present investigation ganciclovir (GAN) loaded microparticles dispersed in hydrogel-based contact lenses were fabricated, characterized and evaluated for eye irritation.

METHODS

GAN-Hydroxy Propyl Methyl Cellulose (HPMC) microparticles were prepared by solvent evaporation method and evaluated for entrapment efficiency, drug content and drug release. The Polyhydroxyethylmethacrylate (pHEMA) contact lenses were synthesized by free radical polymerization reaction using crosslinkers like ethylene glycoldimethacrylate and photoinitiator such as IRGACURE 1173^®, in UVB light, λ 365 nm. The GAN-HPMC microparticles when incorporated into the premonomer mixture and polymerized together give rise to a particle dispersion system in the hydrogel contact lenses. The contact lenses were studied for surface morphology, transmittance, swelling, drug release, Na⁺ion permeability and hens egg test chorioallantoic membrane assay (HETCAM).

RESULTS

Hydrogel contact lens exhibited satisfactory surface morphology, transmittance, swelling, Na⁺ion permeability (3.72 × 106 mm²/min) and a release of 48 h suggesting a potential for prolonged ocular drug delivery. Furthermore, HETCAM exhibited no signs of ocular irritation.

CONCLUSION

The developed delivery platform is a promising alternative to conventional dosage forms like eye drops, suspensions and ointments due to its increase in the residence time attributed to its prolonged release profile.

Stretchable and transparent ionogel-based heaters

Transparent heaters (THs) are widely used for various applications, such as in smart windows, deicers, defoggers, displays, and thermotherapy pads. The rapid development of flexible electronics has led to a demand for flexible and even stretchable THs. At present, most stretchable THs are designed using a combination of electronically conductive networks and flexible polymer materials. Electronic THs still face common challenges, such as a transparency-conductance trade-off, non-uniform heating, and poor interfacial adhesion. In this work, an ionic TH is reported based on a stretchable and transparent ionogel. Joule heating from an ionic current induced by alternating voltage functions as the heating source. This ionogel-based TH exhibits excellent and steady mechanical, optical, electrical, and thermal properties, simultaneously solving the abovementioned three problems relating to electronic THs. Two simple applications of this ionogel-based TH are demonstrated: deicing and boiling water. This reported ionogel-based TH provides a new material choice and heating principle to compete with conventional electronic TH technology.

Lab-on-a-Contact Lens: Recent Advances and Future Opportunities in Diagnostics and Therapeutics

The eye is one of the most complex organs in the human body, containing rich and critical physiological information (e.g., intraocular pressure, corneal temperature, and pH) as well as a library of metabolite biomarkers (e.g., glucose, proteins, and specific ions). Smart contact lenses (SCLs) can serve as a wearable intelligent ocular prosthetic device capable of noninvasive and continuous monitoring of various essential physical/biochemical parameters and drug loading/delivery for the treatment of ocular diseases. Advances in SCL technologies and the growing public interest in personalized health are accelerating SCL research more than ever before. Here, the current status and potential of SCL development through a comprehensive review from fabrication to applications to commercialization are discussed. First, the material, fabrication, and platform designs of the SCLs for the diagnostic and therapeutic applications are discussed. Then, the latest advances in diagnostic and therapeutic SCLs for clinical translation are reviewed. Later, the established techniques for wearable power transfer and wireless data transmission applied to current SCL devices are summarized. An outlook, future opportunities, and challenges for developing next-generation SCL devices are also provided. With the rise in interest of SCL development, this comprehensive and essential review can serve as a new paradigm for the SCL devices.

Numerical Study of Customized Artificial Cornea Shape by Hydrogel Biomaterials on Imaging and Wavefront Aberration

The blindness caused by cornea diseases has exacerbated many patients all over the world. The disadvantages of using donor corneas may cause challenges to recovering eye sight. Developing artificial corneas with biocompatibility may provide another option to recover blindness. The techniques of making individual artificial corneas that fit the biometric parameters for each person can be used to help these patients effectively. In this study, artificial corneas with different shapes (spherical, aspherical, and biconic shapes) are designed and they could be made by two different hydrogel polymers that form an interpenetrating polymer network for their excellent mechanical strength. Two designed cases for the artificial corneas are considered in the simulations: to optimize the artificial cornea for patients who still wear glasses and to assume that the patient does not wear glasses after transplanting with the optimized artificial cornea. The results show that the artificial corneas can efficiently decrease the imaging blur. Increasing asphericity of the current designed artificial corneas can be helpful for the imaging corrections. The differences in the optical performance of the optimized artificial corneas by using different materials are small. It is found that the optimized artificial cornea can reduce the high order aberrations for the second case.

Three-dimensional printed personalized drug devices with anatomical fit: a review

OBJECTIVES

Three-dimensional printing (3DP) has opened the era of drug personalization, promising to revolutionize the pharmaceutical field with improvements in efficacy, safety and compliance of the treatments. As a result of these investigations, a vast therapeutic field has opened for 3DP-loaded drug devices with an anatomical fit. Along these lines, innovative dosage forms, unimaginable until recently, can be obtained. This review explores 3DP-engineered drug devices described in recent research articles, as well as in patented inventions, and even devices already produced by 3DP with drug-loading potential.

KEY FINDINGS

3D drug-loaded stents, implants and prostheses are reviewed, along with devices produced to fit hard-to-attach body parts such as nasal masks, vaginal rings or mouthguards. The most promising 3DP techniques for such devices and the complementary technologies surrounding these inventions are also discussed, particularly the scanners useful for mapping body parts. Health regulatory concerns regarding the new use of such technology are also analysed.

SUMMARY

The scenario discussed in this review shows that for wearable 3DP drug devices to become a tangible reality to users, it will be necessary to overcome the existing regulatory barriers, create new interfaces with electronic systems and improve the mapping mechanisms of body surfaces.

Post-Operative Monitoring of Intestinal Tissue Oxygenation Using an Implantable Microfabricated Oxygen Sensor

Anastomotic leakage (AL) is a common and dangerous post-operative complication following intestinal resection, causing substantial morbidity and mortality. Ischaemia in the tissue surrounding the anastomosis is a major risk-factor for AL development. Continuous tissue oxygenation monitoring during the post-operative recovery period would provide early and accurate early identification of AL risk. We describe the construction and testing of a miniature implantable electrochemical oxygen sensor that addresses this need. It consisted of an array of platinum microelectrodes, microfabricated on a silicon substrate, with a poly(2-hydroxyethyl methacrylate) hydrogel membrane to protect the sensor surface. The sensor was encapsulated in a biocompatible package with a wired connection to external instrumentation. It gave a sensitive and highly linear response to variations in oxygen partial pressure in vitro, although over time its sensitivity was partially decreased by protein biofouling. Using a pre-clinical in vivo pig model, acute intestinal ischaemia was robustly and accurately detected by the sensor. Graded changes in tissue oxygenation were also measurable, with relative differences detected more accurately than absolute differences. Finally, we demonstrated its suitability for continuous monitoring of tissue oxygenation at a colorectal anastomosis over a period of at least 45 h. This study provides evidence to support the development and use of implantable electrochemical oxygen sensors for post-operative monitoring of anastomosis oxygenation.

Silver Nanoparticles from Oregano Leaves' Extracts as Antimicrobial Components for Non-Infected Hydrogel Contact Lenses

The oregano leaves' extract (ORLE) was used for the formation of silver nanoparticles (AgNPs(ORLE)). ORLE and AgNPs(ORLE) (2 mg/mL) were dispersed in polymer hydrogels to give the pHEMA@ORLE_2 and pHEMA@AgNPs(ORLE)_2 using hydroxyethyl-methacrylate (HEMA). The materials were characterized by X-ray fluorescence (XRF) spectroscopy, X-ray powder diffraction analysis (XRPD), thermogravimetric differential thermal analysis (TG-DTA), derivative thermogravimetry/differential scanning calorimetry (DTG/DSC), ultraviolet (UV-Vis), and attenuated total reflection mode (ATR-FTIR) spectroscopies in solid state and UV-Vis in solution. The crystallite size value, analyzed with XRPD, was determined at 20 nm. The antimicrobial activity of the materials was investigated against Gram-negative bacterial strains Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli). The Gram-positive ones of the genus of Staphylococcus epidermidis (S. epidermidis) and Staphylococcus aureus (S. aureus) are known to be involved in microbial keratitis by the means of inhibitory zone (IZ), minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). The IZs, which developed upon incubation of P. aeruginosa, E. coli, S. epidermidis, and S. aureus with paper discs soaked in 2 mg/mL of AgNPs(ORLE), were 11.7 ± 0.7, 13.5 ± 1.9, 12.7 ± 1.7, and 14.3 ± 1.7 mm. When the same dose of ORLE was administrated, the IZs were 10.2 ± 0.7, 9.2 ± 0.5, 9.0 ± 0.0, and 9.0 ± 0.0 mm. The percent of bacterial viability when they were incubated over the polymeric hydrogel discs of pHEMA@AgNPs(ORLE)_2 was interestingly low (66.5, 88.3, 77.7, and 59.6%, respectively, against of P. aeruginosa, E. coli, S. epidermidis, and S. aureus) and those of pHEMA@ORLE_2 were 89.3, 88.1, 92.8, and 84.6%, respectively. Consequently, pHEMA@AgNPs(ORLE)_2 could be an efficient candidate toward the development of non-infectious contact lenses.

Review on the advancements of magnetic gels: towards multifunctional magnetic liposome-hydrogel composites for biomedical applications

Magnetic gels have been gaining great attention in nanomedicine, as they combine features of hydrogels and magnetic nanoparticles into a single system. The incorporation of liposomes in magnetic gels further leads to a more robust multifunctional system enabling more functions and spatiotemporal control required for biomedical applications, which includes on-demand drug release. In this review, magnetic gels components are initially introduced, as well as an overview of advancements on the development, tuneability, manipulation and application of these materials. After a discussion of the advantages of combining hydrogels with liposomes, the properties, fabrication strategies and applications of magnetic liposome-hydrogel composites (magnetic lipogels or magnetolipogels) are reviewed. Overall, the progress of magnetic gels towards smart multifunctional materials are emphasized, considering the contributions for future developments.

Photoinduced Polymerization of Eugenol-Derived Methacrylates

Biobased monomers have been used to replace their petroleum counterparts in the synthesis of polymers that are aimed at different applications. However, environmentally friendly polymerization processes are also essential to guarantee greener materials. Thus, photoinduced polymerization, which is low-energy consuming and solvent-free, rises as a suitable option. In this work, eugenol-, isoeugenol-, and dihydroeugenol-derived methacrylates are employed in radical photopolymerization to produce biobased polymers. The polymerization is monitored in the absence and presence of a photoinitiator and under air or protected from air, using Real-Time Fourier Transform Infrared Spectroscopy. The polymerization rate of the methacrylate double bonds was affected by the presence and reactivity of the allyl and propenyl groups in the eugenol- and isoeugenol-derived methacrylates, respectively. These groups are involved in radical addition, degradative chain transfer, and termination reactions, yielding crosslinked polymers. The materials, in the form of films, are characterized by differential scanning calorimetry, thermogravimetric, and contact angle analyses.

Sagittal height differences of disposable soft contact lenses

PURPOSE

We aim to improve contact lens fitting by using an innovative and simple photogrammetry imaging system to find the sagittal height (SAG) of soft contact lenses.

METHODS

Eleven different types of commercially available soft contact lenses were measured, and five different lenses per package of each lens type were evaluated. The lenses were inserted in a polymethyl methacrylate cell with parallel faces containing a solution of saline and fluorescein to improve the contrast against the background. For every lens, two photographs from the top view and five photographs from the side view were taken. Using homothetic transformations, we calculated the sagittal height.

RESULTS

The SAG of all lenses ranged from 3450 to 3907 μm. Differences can be appreciated between SAG of different materials. Performing an ANOVA test, we confirm that the intra-packaging sagitta is reliable for every lens. Comparing the measured SAG with the calculated spherical one, we confirm that the majority of lenses, eight out of eleven, have a spherical geometry for the internal side. Finally, we are able to group the type of lenses that present similar SAG apart from the data reported on the blister.

CONCLUSION

Optical coherence tomography measurement of the eye sagitta over a given chord helped finding the first lens to fit, because matching contact lens sagitta and ocular sagitta is the key for a good fitting. In our work, we found that the majority of brands use single sphere geometry for internal surface of disposable soft contact lenses.

Advances in bioinks and in vivo imaging of biomaterials for CNS applications

Due to increasing life expectancy incidence of neurological disorders is rapidly rising, thus adding urgency to develop effective strategies for treatment. Stem cell-based therapies were considered highly promising and while progress in this field is evident, outcomes of clinical trials are rather disappointing. Suboptimal engraftment, poor cell survival and uncontrolled differentiation may be the reasons behind dismal results. Clearly, new direction is needed and we postulate that with recent progress in biomaterials and bioprinting, regenerative approaches for neurological applications may be finally successful. The use of biomaterials aids engraftment of stem cells, protects them from harmful microenvironment and importantly, it facilitates the incorporation of cell-supporting molecules. The biomaterials used in bioprinting (the bioinks) form a scaffold for embedding the cells/biomolecules of interest, but also could be exploited as a source of endogenous contrast or supplemented with contrast agents for imaging. Additionally, bioprinting enables patient-specific customization with shape/size tailored for actual needs. In stroke or traumatic brain injury for example lesions are localized and focal, and usually progress with significant loss of tissue volume creating space that could be filled with artificial tissue using bioprinting modalities. The value of imaging for bioprinting technology is advantageous on many levels including design of custom shapes scaffolds based on anatomical 3D scans, assessment of performance and integration after scaffold implantation, or to learn about the degradation over time. In this review, we focus on bioprinting technology describing different printing techniques and properties of biomaterials in the context of requirements for neurological applications. We also discuss the need for in vivo imaging of implanted materials and tissue constructs reviewing applicable imaging modalities and type of information they can provide. STATEMENT OF SIGNIFICANCE: Current stem cell-based regenerative strategies for neurological diseases are ineffective due to inaccurate engraftment, low cell viability and suboptimal differentiation. Bioprinting and embedding stem cells within biomaterials at high precision, including building complex multi-material and multi-cell type composites may bring a breakthrough in this field. We provide here comprehensive review of bioinks, bioprinting techniques applicable to application for neurological disorders. Appreciating importance of longitudinal monitoring of implanted scaffolds, we discuss advantages of various imaging modalities available and suitable for imaging biomaterials in the central nervous system. Our goal is to inspire new experimental approaches combining imaging, biomaterials/bioinks, advanced manufacturing and tissue engineering approaches, and stimulate interest in image-guided therapies based on bioprinting.

Contact Lens Technology: From Fundamentals to Applications

Contact lenses are ocular prosthetic devices used by over 150 million people worldwide. Primary applications of contact lenses include vision correction, therapeutics, and cosmetics. Contact lens materials have significantly evolved over time to minimize adverse effects associated with contact lens wearing, to maintain a regular corneal metabolism, and to preserve tear film stability. This article encompasses contact lens technology, including materials, chemical and physical properties, manufacturing processes, microbial contamination, and ocular complications. The function and the composition of the tear fluid are discussed to assess its potential as a diagnostic media. The regulatory standards of contact lens devices with regard to biocompatibility and contact lens market are presented. Future prospects in contact lens technology are evaluated, with particular interest given to theranostic applications for in situ continuous monitoring the ocular physiology.

Cataract-preventing contact lens for in vivo imaging of mouse retina

In vivo imaging of mouse retinas using two-photon or confocal laser scanning fluorescence microscopy is a powerful tool for time-lapse analyses of the dynamic movements of cell populations. However, acute and reversible opacification of the crystalline lenses of mouse eyes under anesthesia decreases the visibility of the ocular fundus. Therefore, we developed a customized contact lens for preventing cataract during continuous retinal imaging in anesthetized mice. This experimental approach will aid in the elucidation of cellular and molecular dynamics in the CNS under physiological and pathological conditions.

Evaluation of Polyvinyl Alcohol/Pectin-Based Hydrogel Disks as Extraction Phase for Determination of Steroidal Hormones in Aqueous Samples by GC-MS/MS

A new extraction phase based on hydrogel disks of polyvinyl alcohol (PVOH) and pectin was proposed, characterized and evaluated for the extraction of six steroidal hormones (estriol, estrone, 17β-estradiol, 17α-ethinylestradiol, progesterone, and testosterone) in aqueous samples with subsequent determination by gas chromatography-tandem mass spectrometry (GC-MS/MS) after the derivatization procedure. The developed extraction procedure was based on the solid phase extraction (SPE) technique, but employed hydrogel as the sorbent phase. The effects of several parameters, including the amount and composition of the sorbent phase, pH, sample volume, flow rate, and gel swelling over the extraction efficiency, were evaluated. Gels with lower swelling indexes and larger amounts of sorbent ensured higher extraction yields of analytes. The main benefits of using the PVOH/pectin-based hydrogel as the extraction phase are the ease of synthesis, low-cost preparation, and the possibility of reusing the extraction disks. Limits of quantification of 0.5 μg L-1 for estrone and 17β-estradiol, and 1 μg L-1 for testosterone, 17α-ethinylestradiol, progesterone, and estriol were obtained. Accuracy values ranged from 80% to 110%, while the inter-assay precision ranged from 0.23% to 22.2% and the intra-assay from 0.55% to 12.3%. Since the sorbent phase has an amphiphilic character, the use of hydrogels is promising for the extraction of medium-to-high polarity compounds.

Tunable antibiotic delivery from gellan hydrogels

Hydrogels are used extensively in wound management. Many wounds are highly susceptible to infection and hydrogels can provide localized antibacterial delivery to treat and prevent this infection. There are several key considerations in designing antibacterial hydrogels for wound therapy, including preserving activity of encapsulated antibacterial agents, controlling drug release timescales and concentrations, and having the ability to conform to various wound configurations. In this work, we have used gellan, a U.S. Food and Drug Administration approved food additive, to develop antibiotic loaded hydrogels focusing on these criteria. These hydrogels were formed to exhibit a range of mechanical properties, which were investigated using oscillatory rheology. We denoted hydrogels formed using 1% w/v gellan and 1 mM CaCl₂"ointment" hydrogels and those formed using 4% w/v gellan and 7 mM CaCl₂"sheet" hydrogels. Vancomycin, a broad-spectrum antibiotic against Gram-positive bacteria, was encapsulated in these hydrogels both directly and/or in graphitized carbon black nanoparticles (CNPs). We found that vancomycin released from both sheet and ointment hydrogels at therapeutically effective concentrations over 9 days with CNPs and 6 days without CNPs. Applying the Ritger-Peppas and Peppas-Sahlin semi-empirical drug release models to sheet hydrogels, we determined that Fickian diffusion dominates release while case II relaxation also has a small contribution. The sheet hydrogels exhibited a larger overall release of the drug (83.6 ± 1.6% compared to 67.0 ± 2.6% for ointments), which was attributed to the larger swelling resulting from osmotic pressure differences between the hydrogel formulations and the release buffer. We also suggest that final drug release amounts are influenced by intermolecular interactions between vancomycin and gellan, which were observed via quartz crystal microbalance with dissipation monitoring. Lastly, we examined the potential for future in vivo translation. We demonstrated in vitro growth inhibition of Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus in the presence of these hydrogels, demonstrating that vancomycin activity is preserved upon encapsulation. We also showed that these hydrogels are non-toxic to important wound healing cells including fibroblasts and mesenchymal stem cells.

Nonpupil adaptive optics for visual simulation of a customized contact lens

We present a method for determining the deformable mirror profile to simulate the optical effect of a customized contact lens in the central visual field. Using nonpupil-conjugated adaptive optics allows a wider field simulation compared to traditional pupil-conjugated adaptive optics. For a given contact lens, the mirror shape can be derived analytically using Fermat's principle of the stationary optical path or numerically using optimization in ray-tracing programs. An example of an aspheric contact lens simulation is given to illustrate the method, and the effect of eye misalignment with respect to the deformable mirror position is investigated. The optimal deformable mirror conjugation position is found to be near the posterior corneal surface. Chromatic aberration analysis is also presented, and our findings indicate that the polychromatic simulation quality is similar to that of the monochromatic case, even though the mirror is a reflective component. The limitations of a single continuous surface deformable mirror to mimic a contact lens are outlined, with some recommendations for improving the quality of simulation.

Microfluidic Contact Lenses

Contact lens is a ubiquitous technology used for vision correction and cosmetics. Sensing in contact lenses has emerged as a potential platform for minimally invasive point-of-care diagnostics. Here, a microlithography method is developed to fabricate microconcavities and microchannels in a hydrogel-based contact lens via a combination of laser patterning and embedded templating. Optical microlithography parameters influencing the formation of microconcavities including ablation power (4.3 W) and beam speed (50 mm s^-1 ) are optimized to control the microconcavity depth (100 µm) and diameter (1.5 mm). The fiber templating method allows the production of microchannels having a diameter range of 100-150 µm. Leak-proof microchannel and microconcavity connections in contact lenses are validated through flow testing of artificial tear containing fluorescent microbeads (Ø = 1-2 µm). The microconcavities of contact lenses are functionalized with multiplexed fluorophores (2 µL) to demonstrate optical excitation and emission capability within the visible spectrum. The fabricated microfluidic contact lenses may have applications in ophthalmic monitoring of metabolic disorders at point-of-care settings and controlled drug release for therapeutics.

Effect of a contact lens on mouse retinal in vivo imaging: Effective focal length changes and monochromatic aberrations

For in vivo mouse retinal imaging, especially with Adaptive Optics instruments, application of a contact lens is desirable, as it allows maintenance of cornea hydration and helps to prevent cataract formation during lengthy imaging sessions. However, since the refractive elements of the eye (cornea and lens) serve as the objective for most in vivo retinal imaging systems, the use of a contact lens, even with 0 Dpt. refractive power, can alter the system’s optical properties. In this investigation we examined the effective focal length change and the aberrations that arise from use of a contact lens. First, focal length changes were simulated with a Zemax mouse eye model. Then ocular aberrations with and without a 0 Dpt. contact lens were measured with a Shack-Hartmann wavefront sensor (SHWS) in a customized AO-SLO system. Total RMS wavefront errors were measured for two groups of mice (14-month, and 2.5-month-old), decomposed into 66 Zernike aberration terms, and compared. These data revealed that vertical coma and spherical aberrations were increased with use of a contact lens in our system. Based on the ocular wavefront data we evaluated the effect of the contact lens on the imaging system performance as a function of the pupil size. Both RMS error and Strehl ratios were quantified for the two groups of mice, with and without contact lenses, and for different input beam sizes. These results provide information for determining optimum pupil size for retinal imaging without adaptive optics, and raise critical issues for design of mouse optical imaging systems that incorporate contact lenses.