Zero-Order Antibiotic Release from Multilayer Contact Lenses: Nonuniform Drug and Diffusivity Distributions Produce Constant-Rate Drug Delivery

Drug-eluting contact lenses: Progress, challenges, and prospects

Topical ophthalmic solutions (eye drops) are becoming increasingly popular in treating and preventing ocular diseases for their safety, noninvasiveness, and ease of handling. However, the static and dynamic barriers of eyes cause the extremely low bioavailability (<5%) of eye drops, making ocular therapy challenging. Thus, drug-eluting corneal contact lenses (DECLs) have been intensively investigated as a drug delivery device for their attractive properties, such as sustained drug release and improved bioavailability. In order to promote the clinical application of DECLs, multiple aspects, i.e., drug release and penetration, safety, and biocompatibility, of these drug delivery systems were thoroughly examined. In this review, we systematically discussed advances in DECLs, including types of preparation materials, drug-loading strategies, drug release mechanisms, strategies for penetrating ocular barriers, in vitro and in vivo drug delivery and penetration detection, safety, and biocompatibility validation methods, as well as challenges and future perspectives.

Dynamic Covalent Amphiphilic Polymer Conetworks Based on End-Linked Pluronic F108: Preparation, Characterization, and Evaluation as Matrices for Gel Polymer Electrolytes

We present the development of a platform of well-defined, dynamic covalent amphiphilic polymer conetworks (APCN) based on an α,ω-dibenzaldehyde end-functionalized linear amphiphilic poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) (PEG-b-PPG-b-PEG, Pluronic) copolymer end-linked with a triacylhydrazide oligo(ethylene glycol) triarmed star cross-linker. The developed APCNs were characterized in terms of their rheological (increase in the storage modulus by a factor of 2 with increase in temperature from 10 to 50 °C), self-healing, self-assembling, and mechanical properties and evaluated as a matrix for gel polymer electrolytes (GPEs) in both the stretched and unstretched states. Our results show that water-loaded APCNs almost completely self-mend, self-organize at room temperature into a body-centered cubic structure with long-range order exhibiting an aggregation number of around 80, and display an exceptional room temperature stretchability of ∼2400%. Furthermore, ionic liquid-loaded APCNs could serve as gel polymer electrolytes (GPEs), displaying a substantial ion conductivity in the unstretched state, which was gradually reduced upon elongation up to a strain of 4, above which it gradually increased. Finally, it was found that recycled (dissolved and re-formed) ionic liquid-loaded APCNs could be reused as GPEs preserving 50-70% of their original ion conductivity.

Constructing an Ultra-Rapid Nanoconfinement-Enhanced Fluorescence Clinical Detection Platform by Using Machine Learning and Tunable DNA Xerogel "Probe"

Low mass transfer efficiency and unavoidable matrix effects seriously limit the development of rapid and accurate determination of biosensing systems. Herein, we have successfully constructed an ultra-rapid nanoconfinement-enhanced fluorescence clinical detection platform based on machine learning (ML) and DNA xerogel "probe", which was performed by detecting neutrophil gelatinase-associated lipocalin (NGAL, protein biomarker of acute kidney injury). By regulating pore sizes of the xerogels, the transfer of NGAL in xerogels can approximate that in homogeneous solution. Due to electrostatic attraction of the pore entrances, NGAL rapidly enriches on the surface and inside the xerogels. The reaction rate of NGAL and aptamer cross-linked in xerogels is also accelerated because of the nanoconfinement effect-induced increasing reactant concentration and the enhanced affinity constant KD between reactants, which can be promoted by ∼667-fold than that in bulk solution, thus achieving ultra-rapid detection (ca. 5 min) of human urine. The platform could realize one-step detection without sample pretreatments due to the antiligand exchange effect on the surface of N-doped carbon quantum dots (N-CQDs) in xerogels, in which ligand exchange between -COOH and underlying interfering ions in urine will be inhibited due to higher adsorption energy of -COOH on the N-CQD surface relative to the interfering ions. Based on the ML-extended program, the real-time analysis of the urine fluorescence spectra can be completed within 2 s. Interestingly, by changing DNA, aptamer sequences, or xerogel fluorescence intensities, the detection platform can be customized for targeted diseases.

Contact lens as an emerging platform for ophthalmic drug delivery: A systematic review

The number of people with eye diseases has increased with the use of electronics. However, the bioavailability of eye drops remains low owing to the presence of the ocular barrier and other reasons. Although many drug delivery systems have been developed to overcome these problems, they have certain limitations. In recent years, the development of contact lenses that can deliver drugs for long periods with high bioavailability and without affecting vision has increased the interest in using contact lenses for drug delivery. Hence, a review of the current state of research on drug delivery contact lenses has become crucial. This article reviews the key physical and chemical properties of drug-laden contact lenses, development and classification of contact lenses, and features of the commonly used materials. A review of the methods commonly used in current research to create contact lenses has also been presented. An overview on how drug-laden contact lenses can overcome the problems of high burst and short release duration has been discussed. Overall, the review focuses on drug delivery methods using smart contact lenses, and predicts the future direction of research on contact lenses.

Intelligent wireless theranostic contact lens for electrical sensing and regulation of intraocular pressure

Engineering wearable devices that can wirelessly track intraocular pressure and offer feedback-medicine administrations are highly desirable for glaucoma treatments, yet remain challenging due to issues of limited sizes, wireless operations, and wireless cross-coupling. Here, we present an integrated wireless theranostic contact lens for in situ electrical sensing of intraocular pressure and on-demand anti-glaucoma drug delivery. The wireless theranostic contact lens utilizes a highly compact structural design, which enables high-degreed integration and frequency separation on the curved and limited surface of contact lens. The wireless intraocular pressure sensing modulus could ultra-sensitively detect intraocular pressure fluctuations, due to the unique cantilever configuration design of capacitive sensing circuit. The drug delivery modulus employs an efficient wireless power transfer circuit, to trigger delivery of anti-glaucoma drug into aqueous chamber via iontophoresis. The minimally invasive, smart, wireless and theranostic features endow the wireless theranostic contact lens as a highly promising system for glaucoma treatments.

Does skin permeation kinetics influence efficacy of topical dermal drug delivery system?: Assessment, prediction, utilization, and integration of chitosan biomacromolecule for augmenting topical dermal drug delivery in skin

Skin permeation is an integral part of penetration of topical therapeutics. Zero order in addition to Higuchi permeation kinetic is usually preferred in topical drug delivery cargo. Penetration of therapeutic entities through epidermal barrier is a major challenge for scientific fraternity. Furthermore, penetration of therapeutic entities determines the transportation and ultimately therapeutic efficacy of topical dermal dosage forms. Apart from experimentation models, mathematical equations, in silico docking, molecular dynamics (MDs), and artificial neural network (Neural) techniques are being used to assess free energies and prediction of electrostatic attractions in order to predict the permeation phenomena of therapeutic entities. Therefore, in the present review, we have summarized the significance of kinetic equations, in silico docking, MDs, and ANN in assessing and predicting the penetration behavior of topical therapeutics through dermal dosage form. In addition, the role of chitosan biomacromolecule in modulating permeation of topical therapeutics in skin has also been illustrated using computational techniques.

Model Amphiphilic Polymer Conetworks in Water: Prediction of Their Ability for Oil Solubilization

In this work, we computationally explored the ability of water-swollen, model ionizable ABA triblock copolymer-based amphiphilic polymer conetworks (APCNs) to solubilize a water-immiscible organic solvent (oil), via Gibbs free energy minimization. This was done as a function of the conetwork hydrophobe (A-blocks) mol fraction and the degree of ionization of the hydrophilic B-blocks. Expectedly, highest oil solubilization capacities were calculated for the most hydrophobic and least ionized APCNs, which could absorb up to 6.4 times more oil than water and exhibited a lamellar morphology. Our results also included a phase diagram, which indicated transitions from spheres to cylinders, lamellae, and unimers in oil, as the hydrophobe content increased and the degree of ionization decreased. All of these transitions were accompanied by discontinuous changes in the degrees of swelling in the aqueous and oil nanophases, discontinuous changes in the asymmetry ratios (for the anisotropic morphologies), and discontinuous changes in the oil solubilization capacities. This is the first time that a dual discontinuous volume phase transition is reported within a polymer gel.

Bioinspired hydrogels for drug-eluting contact lenses

Efficient ocular drug delivery that can overcome the challenges of topical application has been largely pursued. Contact lenses (CLs) may act as light-transparent cornea/sclera bandages for prolonged drug release towards the post-lens tear fluid, if their composition and inner architecture are fitted to the features of the drug molecules. In this review, first the foundations and advantages of using CLs as ocular drug depots are revisited. Then, pros and cons of common strategies to prepare drug-loaded CLs are analyzed on the basis of recent examples, and finally the main section focuses on bioinspired strategies that can overcome some limitations of current designs. Most bioinspired strategies resemble a reverse engineering process to create artificial receptors for the drug inside the CL network by mimicking the human natural binding site of the drug. Related bioinspired strategies are being also tested for designing CLs that elute comfort ingredients mimicking the blinking-associated renewal of eye mucins. Other bioinspired approaches exploit the natural eye variables as stimuli to trigger drug release or take benefit of bio-glues to specifically bind active components to the CL surface. Overall, biomimicking approaches are being revealed as valuable tools to fit the amounts loaded and the release profiles to the therapeutic demands of each pathology. STATEMENT OF SIGNIFICANCE: Biomimetic and bioinspired strategies are remarkable tools for the optimization of drug delivery systems. Translation of the knowledge about how drugs interact with the natural pharmacological receptor and about components and dynamics of anterior eye segment may shed light on the design criteria for obtaining efficient drug-eluting CLs. Current strategies for endowing CLs with controlled drug release performance still require optimization regarding amount loaded, drug retained in the CL structure during storage, regulation of drug release once applied onto the eye, and maintenance of CL physical properties. All these limitations may be addressed through a variety of recently growing bioinspired approaches, which are expected to pave the way of medicated CLs towards the clinics.

pH-Triggered Release from Polyamide Microcapsules Prepared by Interfacial Polymerization of a Simple Diester Monomer

The majority of current pH-triggered release systems is designed to respond to either low or high pH. Encapsulants based on polyampholytes are an example of materials that can respond to both acidic and basic pH. However, polyampholyte-based encapsulants generally possess a low loading capacity and have difficulty retaining their small-molecule cargo. The current work utilizes interfacial polymerization between polyamines and a pyromellitic diester diacid chloride to form high capacity "liquid core-shell" polyamide microcapsules that are stable in a dry or nonpolar environment but undergo steady, controlled release at pH 7.4 and accelerated release at pH 5 and pH 10. The rate of release can be tuned by adjusting the amine cross-linker feed ratio, which varies the degree of cross-linking in the polymer shell. The thin-shell microcapsule exhibited suitable barrier properties and tunable dual acid/base-triggered release, with applications in a wide range of pH environments.

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.