Contact Lenses For Drug Delivery Research Articles

Current Advances in Regenerative Strategies for Dry Eye Diseases: A Comprehensive Review.

Dry eye disease (DED) is an emerging health issue affecting millions of individuals annually. Ocular surface disorders, such as DED, are characterized by inflammation triggered by various factors. This condition can lead to tear deficiencies, resulting in the desiccation of the ocular surface, corneal ulceration/perforation, increased susceptibility to infections, and a higher risk of severe visual impairment and blindness. Currently, the clinical management of DED primarily relies on supportive and palliative measures, including the frequent and lifelong use of different lubricating agents. While some advancements like punctal plugs, non-steroidal anti-inflammatory drugs, and salivary gland autografts have been attempted, they have shown limited effectiveness. Recently, there have been promising developments in the treatment of DED, including biomaterials such as nano-systems, hydrogels, and contact lenses for drug delivery, cell-based therapies, biological approaches, and tissue-based regenerative therapy. This article specifically explores the different strategies reported so far for treating DED. The aim is to discuss their potential as long-term cures for DED while also considering the factors that limit their feasibility and effectiveness. These advancements offer hope for more effective and sustainable treatment options in the future.

Newer approaches to dry eye therapy: Nanotechnology, regenerative medicine, and tissue engineering.

Definitive treatment of dry eye disease (DED), one of the commonest ocular surface disorders, has remained elusive despite several recent advances in better diagnostics and the introduction of newer therapeutic molecules. The current treatment paradigms rely heavily on lubricating eye drops and anti-inflammatory agents that may need to be used long-term and are mainly palliative. Research is ongoing not only for a curative treatment option but also to improve the potency and efficacy of existing drug molecules through better formulations and delivery platforms. In the past two decades, significant advancement has been made in terms of preservative-free formulations, biomaterials such as nanosystems and hydrogels, stem cell therapy, and creation of a bioengineered lacrimal gland. This review comprehensively summarizes the newer approaches to DED treatment, which are biomaterials such as nanosystems, hydrogels, and contact lenses for drug delivery, cell and tissue-based regenerative therapy for damaged lacrimal gland and ocular surface, and tissue engineering for developing artificial lacrimal gland. Also, their potential efficacies in animal models or in vitro studies and possible limitations are discussed. The ongoing research looks promising and needs to be supported with clinical efficacy and safety studies for human use.

Contact Lenses: A Promising Drug Delivery System

Presently, around 100 million people are estimated to be wearing contact lenses, and the number is growing exponentially. Though the main use of contact lenses is for improving ametropia problems, they also hold attention as therapeutic devices for the treatment of ocular pain, promotion of corneal healing, maintenance of corneal epithelial hydration, and drug delivery. Contact lenses are developing as an substitute ophthalmic drug delivery system to resolve the problems of the conventional topical application methods [1,2]. The interest in evolving contact lenses for drug delivery has expressively increased in the last decade as several new techniques have been developed for designing contact lenses for extended drug delivery. The newest studies show that contact lenses are able to achieve prolonged release of a few weeks without any significant effect on critical lens properties. The future appears promising for drug eluting contact lenses but several challenges remain to be overcome regarding processing and storage issues, lack of use in the elderly population, regulatory issues, high costs of clinical studies and cost-benefit analysis[3]. Contact lenses are attractive for ocular drug delivery systems as significantly prolong the residence time of the drug in the eye, high degree of comfort which improve patient compliance, higher efficiency and low side effects and, hence increase the ocular drug bioavailability[16]. Keywords: Lenses, polymer, methods, therapeutic, eye

Recent Trends in Advanced Contact Lenses.

Exploiting contact lenses for ocular drug delivery is an emerging field in the area of biomedical engineering and advanced healthcare materials. Despite all the research conducted in this area, still, new technologies are in their early stages of the development, and more work must be done in terms of clinical trials to commercialize these technologies. A great challenge in using contact lenses for drug delivery is to achieve a prolonged drug release profile within the therapeutic range for various eye-related problems and diseases. In general, desired release kinetics to avoid the initial burst release is the zero-order kinetics within the therapeutic range. This review highlights the new technologies developed to achieve efficient and extended drug delivery. It also provides an overview of the materials and methods for fabrication of contact lenses and their mechanical and optical properties.

Carbon Black Tinted Contact Lenses for Reduction of Photophobia in Cystinosis Patients

ABSTRACTPurpose: To examine if current development on using contact lenses for drug delivery of cysteamine to treat ocular symptoms of cystinosis can be tinted to mitigate photophobia common in patients by reducing transmittanceMethods: Commercial contact lenses were placed in a carbon black solution to examine loading after lens synthesis. Silicone hydrogel contact lenses were also synthesized with carbon black added prior to UV curing. Transmittance was measured using UV–vis spectrophotometry over the range of 190–1190 nm and compared to unmodified contact lenses. Lens parameters of refractive index, ion permeability, and Young’s modulus were measured using a refractometer, release of sodium chloride, and the cantilever method. Cysteamine release was measured by loading lenses into 5% cysteamine solution and then monitoring the release of the drug using UV–vis spectrophotometry. Vitamin E diffusion barriers were also added to lenses via ethanol solution, and the release of cysteamine from these modified lenses was also examined.Results: No leeching of carbon black was detected during experiments. Loading of pre-made contact lenses led to uneven distribution of carbon black throughout lens. Adding 0.3% carbon black to lens monomer solution prior to UV-curing led to even distribution and a transmittance reduction of approximately 50%. Ion permeability was reduced from 6.19 ± 0.90 x 10−3 to 1.28 ± 0.06 x 10−3 mm2 min−1, and Young’s modulus was decreased from 1.58 ± 0.08 to 1.29 ± 0.06 MPa. Cysteamine releases from carbon black lenses with and without vitamin E were comparable to controls, although the loading solution of vitamin E/ethanol had to be tripled to achieve a similar mass loading to control.Conclusions: Carbon black increases the softness of contact lenses, but a loading of 0.3% maintains lens parameters required for wear. The release of cysteamine is also possible with carbon black lenses, albeit requiring a higher loading concentration of vitamin E to achieve similar release times.

A validated stability-indicating HPLC method for determination of brimonidine tartrate in BRI/PHEMA drug delivery systems

BackgroundA simple, rapid and accurate stability-indicating reverse phase high performance liquid chromatography (RP-HPLC) was developed and validated for the determination of brimonidine tartrate in brimonidine tartrate/poly(2-hydroxyethyl methacrylate) (BRI/PHEMA) drug delivery contact lenses and pharmaceutical formulations.ResultsOptimum chromatographic conditions for separating brimonidine tartrate from other impurities in the leaching liquor of BRI/PHEMA drug delivery contact lenses or pharmaceutical formulations have been achieved by using a Diamonsil C18 column (150 mm × 4.6 mm, 5 μm) as a stationary phase and a mixture solution of phosphate buffer (10 mM, pH3.5) containing 0.5% triethlamine and methanol (85:15, v/v) as a mobile phase at a flow rate of 1 mL/min. The theoretical plates for the brimonidine tartrate measurement were calculated to be 8360 when detection was performed at 246 nm using a diode array detector. The proposed method was validated in accordance with ICH guidelines with respect to linearity, accuracy, precision, robustness, specificity, limit of detection and quantitation. Regression analysis showed a good correlation (R2 > 0.999) for brimonidine tartrate in the concentration range of 0.01–50 μg/mL. The peak purity factor is ≥980 for the analyte after all types of stress tests, indicating an excellent separation of brimonidine tartrate peak from other impurities. The measurement course could be completed within 10 min, which was very quick, effective and convenient.ConclusionsOverall, the proposed stability-indicating method was suitable for routine quality control and drug analysis of brimonidine tartrate in BRI/PHEMA drug delivery contact lenses and other pharmaceutical formulations.

In Vivo Studies Evaluating the Use of Contact Lenses for Drug Delivery.

This review highlights the current state of knowledge of in vivo testing of drug-delivering contact lenses. There has been a significant increase in interest in alternative means to deliver ocular pharmaceuticals, and within the past few decades, contact lenses have emerged as a vehicle of interest because of their biocompatibility and acceptance by both eye care professionals and the public. Using techniques such as molecular imprinting, vitamin E diffusion barriers, ionic reservoirs, and drug-impregnated films, significantly improved drug release kinetics have been observed in vitro. Extension of these results into in vivo studies has thus far been limited but has led to evidence of the viability of this drug delivery platform by demonstrating improved drug residence time, drug penetration, and clinical outcomes when compared with conventional therapy such as eye drops. The evidence supporting these improvements has occurred in both animal models and small human trials and is presented within this review.

Review of ophthalmic drug delivery by contact lenses

Ophthalmic drugs are almost exclusively delivered through eye drops in spite of several deficiencies including low bioavailability and poor compliance. Contact lenses are ideally suited for delivery of drugs to the anterior chamber because of the placement directly on the cornea which results in a high bioavailability of at least 50 % compared to about 1–5 % for eye drops. The ten-fold increase in bioavailability reduces the amount of drug delivered, which in turn reduces the systemic loss of the drug, thereby reducing the potential for side effects. Additionally contact lenses can provide a most uniform release profile compared to the pulsatile delivery with eye drops, which can potentially result in improved therapeutic outcomes. Finally drug delivery via extended wear contact lenses can significantly improve the compliance. In spite of all these benefits, contact lenses are not yet available as drug delivery vehicles mainly because the earlier lens designs were not optimized for drug delivery. The interest in developing contact lenses for drug delivery has significantly increased in the last decade as several new techniques have been developed for designing contact lenses for extended drug delivery. The latest studies show that contact lenses can achieve extended release of a few weeks without any significant impact on critical lens properties. Also in vivo animal studies have proven safety, efficacy and increased bioavailability compared to eye drops. The future appears promising for drug eluting contact lenses but several challenges remain to be overcome regarding processing and storage issues, lack of use in the elderly population, regulatory issues, high costs of clinical studies and cost-benefit analysis.

Insights to Using Contact Lenses for Drug Delivery

There has been considerable interest in the potential application of contact lenses for ocular drug delivery. This short communication provides an overview of the challenges faced by delivering drugs using contact lenses, highlights the solutions to limitations that have already been achieved, and describes the barriers that remain before commercial application can be realized.

Effect of anionic/siloxy groups on the release of ofloxacin from soft contact lenses

AbstractFor the treatment of ocular diseases, chemotherapeutic antibiotics, for example, Ofloxacin, are usually administrated through the application of eye drops during ophthalmic perioperative sterilization. However, this approach has several drawbacks, such as the need for frequent application caused by tears draining the drugs out of the eyes or the presence of a possible contraindication of eye drops when contact lenses are worn. To overcome these problems, we have studied contact lenses composed of hydrogels, which function as a type of drug delivery system technology. We synthesized hydrogels to be used as contact lenses with sufficient amounts of drug uptake and release profiles for sterilization treatment during the perioperative period in ophthalmic areas. This study showed that the hydrogels that included side‐chain ionic groups and silyl groups were useful materials to prepare drug delivery contact lenses. The ionic groups in the hydrogels could functionally retain a drug if an ionic substituent was present. It is noteworthy that the drug content in the contact lenses could readily be controlled by changing the ratio of ionic monomer contents during polymerization. Furthermore, the controlled drug release of silyl‐group‐containing hydrogels showed sustained release over 72 h, which indicated that the hydrogels could be used as contact lenses for sustained drug release. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013

Supercritical fluid-assisted preparation of imprinted contact lenses for drug delivery

The aim of this work was to develop an innovative supercritical fluid (SCF)-assisted molecular imprinting method to endow commercial soft contact lenses (SCLs) with the ability to load specific drugs and to control their release. This approach seeks to overcome the limitation of the common loading of preformed SCLs by immersion in concentrated drug solutions (only valid for highly water soluble drugs) and of the molecular imprinting methods that require choice of the drug before polymerization and thus to create drug-tailored networks. In particular, we focused on improving the flurbiprofen load/release capacity of daily wear Hilafilcon B commercial SCLs by the use of sequential SCF flurbiprofen impregnation and extraction steps. Supercritical carbon dioxide (scCO2) impregnation assays were performed at 12.0MPa and 40°C, while scCO2 extractions were performed at 20.0MPa and 40°C. Conventional flurbiprofen sorption and drug removal experiments in aqueous solutions were carried out for comparison purposes. SCF-processed SCLs showed a recognition ability and a higher affinity for flurbiprofen in aqueous solution than for the structurally related ibuprofen and dexamethasone, which suggests the creation of molecularly imprinted cavities driven by both physical (swelling/plasticization) and chemical (carbonyl groups in the network with the C–F group in the drug) interactions. Processing with scCO2 did not alter some of the critical functional properties of SCLs (glass transition temperature, transmittance, oxygen permeability, contact angle), enabled the control of drug loaded/released amounts (by the application of several consecutive processing cycles) and permitted the preparation of hydrophobic drug-based therapeutic SCLs in much shorter process times than those using conventional aqueous-based molecular imprinting methods.

Contact Lenses for Drug Delivery

The majority of ocular medications are delivered to the eye topically, often in the form of a solution, or eye drop. Contact lenses could potentially also be used to deliver medications to the eye. Recently, progress has been made in developing a drug-eluting contact lens. Different designs have been proposed and several offer the hope of expanding the therapeutic armamentarium for eye care providers.

Contact Lenses for Drug Delivery

Currently, approximately 100 million people are estimated to be wearing contact lenses, and the number is increasing exponentially. Although the main use of contact lenses is for correcting ametropia problems, they also hold interest as therapeutic devices for the relief of ocular pain, promotion of corneal healing, mechanical protection and support, maintenance of corneal epithelial hydration, and drug delivery. Ocular drug administration is particularly challenging and recent research has been directed towards the design of novel drug delivery systems capable of prolonging the permanence of the drug in the precorneal area and, thus, potentially increasing bioavailability and minimizing adverse effects. Conventional hydrogel soft contact lenses have the ability to absorb some drugs and release them into the post-lens lacrimal fluid, minimizing clearance and sorption through the conjunctiva. Their ability to be a drug reservoir strongly depends on the water content and thickness of the lens, the molecular weight of the drug, the concentration of the drug loading solution and the time the lens remains in it. However, the ability of contact lenses to load drugs and to control their release is in general inadequate and the following approaches, based on modifications of the polymer network, are currently under evaluation: (i) covalent binding of the drug to the lens network via labile bonds; (ii) inclusion of the drug in colloidal structures that are dispersed in the lens and are responsible for controlling drug release; (iii) functionalization of the network with chemical groups that work as ion-exchange resins; and (iv) creation in the lens structure of imprinted pockets that memorize the spatial features and bonding preferences of the drug and provide the lens with a high affinity and selectivity for a given drug. In this review, the possibilities and the advantages/drawbacks of these new types of contact lenses as drug delivery systems are critically analyzed.