Ocular drug delivery

Hyaluronan-Cholesterol Nanogels for the Enhancement of the Ocular Delivery of Therapeutics

The anatomy and physiology of the eye strongly limit the bioavailability of locally administered drugs. The entrapment of therapeutics into nanocarriers represents an effective strategy for the topical treatment of several ocular disorders, as they may protect the embedded molecules, enabling drug residence on the ocular surface and/or its penetration into different ocular compartments. The present work shows the activity of hyaluronan-cholesterol nanogels (NHs) as ocular permeation enhancers. Thanks to their bioadhesive properties, NHs firmly interact with the superficial corneal epithelium, without penetrating the stroma, thus modifying the transcorneal penetration of loaded therapeutics. Ex vivo transcorneal permeation experiments show that the permeation of hydrophilic drugs (i.e., tobramycin and diclofenac sodium salt), loaded in NHs, is significantly enhanced when compared to the free drug solutions. On the other side, the permeation of hydrophobic drugs (i.e., dexamethasone and piroxicam) is strongly dependent on the water solubility of the entrapped molecules. The obtained results suggest that NHs formulations can improve the ocular bioavailability of the instilled drugs by increasing their preocular retention time (hydrophobic drugs) or facilitating their permeation (hydrophilic drugs), thus opening the route for the application of HA-based NHs in the treatment of both anterior and posterior eye segment diseases.

Advances and challenges in the nanoparticles-laden contact lenses for ocular drug delivery

The delivery of drugs that target ocular tissues is challenging due to the physiological barriers of the eye like tear dilution, nasolacrimal drainage, blinking, tear turnover rate and low residence time Drug-laden contact lenses can be a possible solution to overcome some of these challenges. Nanoparticles are being extensively studied as novel systems for loading drugs into therapeutic contact lenses. The versatile features of the organic and inorganic nanoparticles and their diverse physicochemical properties make it possible to load and sustain drug release from the contact lenses. Nevertheless, several issues remains to be solved before its clinical application and commercialization such as changes in contact lens swelling (water content), transmittance, protein adherence, surface roughness, tensile strength, ion and oxygen permeability and drug leaching during contact lens manufacture. However, clinical studies demonstrated the potential of therapeutic contact lenses to manage the scientific, commercial and regulatory challenges to make its place in the market. This review highlights the different methodologies used to fabricate nanoparticle-laden contact lenses and highlights the major advances and challenges to commercialization.

Recent advances in ophthalmic preparations: Ocular barriers, dosage forms and routes of administration

The human eye is a complex organ with unique anatomy and physiology that restricts the delivery of drugs to target ocular tissues/sites. Recent advances in the field of pharmacy, biotechnology and material science have led to development of novel ophthalmic dosage forms which can provide sustained drug delivery, reduce dosing frequency and improve the ocular bioavailability of drugs. This review highlights the different anatomical and physiological factors which affect ocular bioavailability of drugs and explores advancements from 2016 to 2020 in various ophthalmic preparations. Different routes of drug administration such as topical, intravitreal, intraocular, juxtascleral, subconjunctival, intracameral and retrobulbar are discussed with their advances and limitations.

Difluprednate-Hydroxypropyl-β-Cyclodextrin-Based Ophthalmic Solution for Improved Delivery in a Porcine Eye Model

Purpose: Difluprednate (DFP) is an approved corticosteroid, available as an ophthalmic emulsion (Durezol^®), used to treat pain and inflammation of the eye following ocular surgeries. This study utilized hydroxypropyl-β-cyclodextrin (HPBCD)-based DFP ophthalmic solution for improved ocular delivery. Methods: The DFP-HPBCD complex formation was studied in the liquid and solid states. Phase solubility, molecular docking studies, differential scanning calorimetry, and Fourier transform infrared spectroscopy suggested inclusion complexation of DFP and HPBCD. Results: DFP-HPBCD-based eye drops (solution) provided 16 and 26 times higher transcorneal permeation when compared to the suspension (no HPBCD, control) and Durezol, respectively (P < 0.001). In addition, ocular drug distribution studies conducted in continuously perfused whole porcine eyes showed DFP permeated into all of the ocular tissues in significantly higher amounts than Durezol. Conclusions: The solution-based eye drops in this study is iso-osmotic, safe, and more permeable in porcine eyes compared to Durezol.

Posterior Segment Ophthalmic Drug Delivery: Role of Muco-Adhesion with a Special Focus on Chitosan

Posterior segment eye diseases (PSEDs) including age macular degeneration (AMD) and diabetic retinopathy (DR) are amongst the major causes of irreversible blindness worldwide. Due to the numerous barriers encountered, highly invasive intravitreal (IVT) injections represent the primary route to deliver drugs to the posterior eye tissues. Thus, the potential of a more patient friendly topical route has been widely investigated. Mucoadhesive formulations can decrease precorneal clearance while prolonging precorneal residence. Thus, they are expected to enhance the chances of adherence to corneal and conjunctival surfaces and as such, enable increased delivery to the posterior eye segment. Among the mucoadhesive polymers available, chitosan is the most widely explored due to its outstanding mucoadhesive characteristics. In this review, the major PSEDs, their treatments, barriers to topical delivery, and routes of topical drug absorption to the posterior eye are presented. To enable the successful design of mucoadhesive ophthalmic drug delivery systems (DDSs), an overview of mucoadhesion, its theory, characterization, and considerations for ocular mucoadhesion is given. Furthermore, chitosan-based DDs that have been explored to promote topical drug delivery to the posterior eye segment are reviewed. Finally, challenges of successful preclinical to clinical translation of these DDSs for posterior eye drug delivery are discussed.

Wettability and contact angle affect precorneal retention and pharmacodynamic behavior of microspheres

In the present study, we describe the development of betaxolol hydrochloride and montmorillonite with ion exchange in a single formulation to create a novel micro-interactive dual-functioning sustained-release delivery system (MIDFDS) for the treatment of glaucoma. Betaxolol hydrochloride molecule was loaded onto the montmorillonite by ion exchange and MIDFDS formation was confirmed by XPS data. MIDFDS showed similar physicochemical properties to those of Betoptic, such as particle size, pH, osmotic pressure, and rheological properties. Nevertheless, the microdialysis and intraocular pressure test revealed better in vivo performance of MIDFDS, such as pharmacokinetics and pharmacodynamics. With regards to wettability, MIDFDS had a larger contact angle (54.66 ± 5.35°) than Betoptic (36.68 ± 1.77°), enabling the MIDFDS (2.93 s) to spread slower on the cornea than Betoptic (2.50 s). Moderate spreading behavior and oppositely charged electrostatic micro-interactions had a comprehensive influence on micro-interactions with the tear film residue, resulting in a longer precorneal retention time. Furthermore, MIDFDS had a significant sustained-release effect, with complete release near the cornea. The dual-functioning sustained-release carrier together with prolonged pre-corneal retention time (80 min) provided sufficiently high drug concentrations in the aqueous humor to achieve a more stable and long-term IOP reduction for 10 h. In addition, cytotoxicity and hemolysis tests showed that MIDFDS had better biocompatibility than Betoptic. The dual-functioning microspheres presented in this study provide the possibility for improved compliance due to low cytotoxicity and hemolysis, which suggests promising clinical implications.

Drug delivery to the anterior segment of the eye: A review of current and future treatment strategies

Research in the development of ophthalmic drug formulations and innovative technologies over the past few decades has been directed at improving the penetration of medications delivered to the eye. Currently, approximately 90% of all ophthalmic drug formulations (e.g. liposomes, micelles) are applied as eye drops. The major challenge of topical eye drops is low bioavailability, need for frequent instillation due to the short half-life, poor drug solubility, and potential side effects. Recent research has been focused on improving topical drug delivery devices by increasing ocular residence time, overcoming physiological and anatomical barriers, and developing medical devices and drug formulations to increase the duration of action of the active drugs. Researchers have developed innovative technologies and formulations ranging from sub-micron to macroscopic size such as prodrugs, enhancers, mucus-penetrating particles (MPPs), therapeutic contact lenses, and collagen corneal shields. Another approach towards the development of effective topical drug delivery is embedding therapeutic formulations in microdevices designed for sustained release of the active drugs. The goal is to optimize the delivery of ophthalmic medications by achieving high drug concentration with prolonged duration of action that is convenient for patients to administer.

Statistical optimization of hyaluronic acid enriched ultradeformable elastosomes for ocular delivery of voriconazole via Box-Behnken design: in vitro characterization and in vivo evaluation

Voriconazole (VCZ) is a well-known broad spectrum triazole antifungal, mainly used orally and intravenously. The study aimed to formulate VCZ into ultradeformable elastosomes for the topical treatment of ocular fungal keratitis. Different formulae were prepared using a modified ethanol injection method, employing a 3³ Box-Behnken design. They were characterized by measuring their entrapment efficiency (EE%), particle size (PS), polydispersity index (PDI) and zeta potential (ZP). The optimized formula was subjected to further in vitro investigations and in vivo evaluation studies. The prepared vesicles had satisfactory EE%, PS, PDI and ZP values. The numerical optimization process suggested an optimal elastosomal formula (OE) composed of phosphatidyl choline and brij S100 at the weight ratio of 3.62: 1, 0.25%w/v hyaluronic acid and 5% (percentage from phosphatidyl choline/brij mixture) polyvinyl alcohol. It had high EE (72.6%), acceptable PS and PDI (362.4 nm and 0.25, respectively) and highly negative ZP of −41.7 mV. OE exhibited higher elasticity than conventional liposomes, with acceptable stability for three months. Transmission electron microscopy demonstrated the spherical morphology of vesicles with an external transparent coat of Hyaluronic acid. OE was expected to cause no ocular irritation or blurring in vision as reflected by pH and refractive index measurements. The histopathological study revealed the safety of OE for ocular use. The fungal susceptibility testing using Candida albicans demonstrated the superiority of OE to VCZ suspension, with greater and more durable growth inhibition. Therefore, OE can be regarded as a promising formula, achieving both safety and efficacy.

Recent Advances in Hydrogels: Ophthalmic Applications in Cell Delivery, Vitreous Substitutes, and Ocular Adhesives

With the prevalence of eye diseases, such as cataracts, retinal degenerative diseases, and glaucoma, different treatments including lens replacement, vitrectomy, and stem cell transplantation have been developed; however, they are not without their respective shortcomings. For example, current methods to seal corneal incisions induced by cataract surgery, such as suturing and stromal hydration, are less than ideal due to the potential for surgically induced astigmatism or wound leakage. Vitrectomy performed on patients with diabetic retinopathy requires an artificial vitreous substitute, with current offerings having many shortcomings such as retinal toxicity. The use of stem cells has also been investigated in retinal degenerative diseases; however, an optimal delivery system is required for successful transplantation. The incorporation of hydrogels into ocular therapy has been a critical focus in overcoming the limitations of current treatments. Previous reviews have extensively documented the use of hydrogels in drug delivery; thus, the goal of this review is to discuss recent advances in hydrogel technology in surgical applications, including dendrimer and gelatin-based hydrogels for ocular adhesives and a variety of different polymers for vitreous substitutes, as well as recent advances in hydrogel-based retinal pigment epithelium (RPE) and retinal progenitor cell (RPC) delivery to the retina.

Topical ocular delivery of vancomycin loaded cationic lipid nanocarriers as a promising and non-invasive alternative approach to intravitreal injection for enhanced bacterial endophthalmitis management

Vancomycin (VCM) is a drug of choice for treating infections caused by Staphylococcus species, reported being the most causative agent of bacterial endophthalmitis. However, the ocular bioavailability of topically applied VCM is low due to its high molecular weight and hydrophilicity. The current study sought to explore whether the nanostructured lipid carriers (NLCs) fabricated via cold homogenization technique could improve ocular penetration and prolong the ophthalmic residence of VCM. A 2³ full factorial design was adopted to evaluate the influence of different process and formulation variables on VCM-loaded NLC formulae. The optimized formula with the particle size of 96.4 ± 0.71 nm and narrow size distribution showed spherical morphology obtained by AFM and represented sustained drug release up to 67% in 48 h fitted to the Korsmeyer-Peppas model with probably non-Fickian diffusion kinetic. FTIR studies visualized the drug-carrier interactions in great detail. High encapsulation of VCM (74.8 ± 4.3% w/w) in NLC has been established in DSC and PXRD analysis. The optimal positively charged (+ 29.7 ± 0.47 mV) colloidal dispersion was also stable for 12 weeks at both 4 °C and 25 °C. According to in vivo studies, incorporation of VCM in NLC resulted in a nearly 3-fold increase in the intravitreal concentration of VCM after eye-drop instillation over control groups. Besides, microbiological evaluation admitted its therapeutic effect within five days is comparable to intravitreal injection of VCM. Further, the optimized formula was found to be nonirritant and safe for ophthalmic administration in RBC hemolytic assay. Also, fluorescent tracking of NLCs on rabbit's cornea showed an increase in corneal penetration of nanoparticles. Thus, it is possible to infer that the evolved NLCs are promising drug delivery systems with superior attainments for enhanced Vancomycin ophthalmic delivery to the eye's posterior segment and improved bacterial endophthalmitis management.

Endogenous dual stimuli-activated NO generation in the conventional outflow pathway for precision glaucoma therapy

High intraocular pressure (IOP) has been regarded as a predominant risk factor for glaucoma. Nitric oxide (NO) is shown to lower IOP, but the magnitude and duration of IOP reduction are not satisfying due to the poor cornea penetration of NO drugs and limited NO generation in the trabecular meshwork (TM)/Schlemm's canal (SC) area. Herein, we introduce deep cornea penetrating biodegradable hollow mesoporous organosilica (HOS) nanocapsules for the efficient co-delivery of hydrophobic JS-K (J_R) and hydrophilic l-Arginine (L_O). The resulting HOS-J_RL_O can be reduced and oxidized by the ascorbic acid (AA) and catalysis of endothelial nitric oxide synthase (eNOS) in the TM/SC microenvironment to release NO for inducing appreciable IOP reduction in various glaucoma mouse models. In addition to developing an endogenous stimuli-responsive NO nanotherapeutic, this study is also expected to establish a versatile, non-invasive, and efficacious treatment paradigm for precision glaucoma therapy.

An ion-paired moxifloxacin nanosuspension eye drop provides improved prevention and treatment of ocular infection

There are numerous barriers to achieving effective intraocular drug administration, including the mucus layer protecting the ocular surface. For this reason, antibiotic eye drops must be used multiple times per day to prevent and treat ocular infections. Frequent eye drop use is inconvenient for patients, and lack of adherence to prescribed dosing regimens limits treatment efficacy and contributes to antibiotic resistance. Here, we describe an ion-pairing approach used to create an insoluble moxifloxacin-pamoate (MOX-PAM) complex for formulation into mucus-penetrating nanosuspension eye drops (MOX-PAM NS). The MOX-PAM NS provided a significant increase in ocular drug absorption, as measured by the area under the curve in cornea tissue and aqueous humor, compared to Vigamox in healthy rats. Prophylactic and treatment efficacy were evaluated in a rat model of ocular Staphylococcus aureus infection. A single drop of MOX-PAM NS was more effective than Vigamox, and completely prevented infection. Once a day dosing with MOX-PAM NS was similar, if not more effective, than three times a day dosing with Vigamox for treating S. aureus infection. The MOX-PAM NS provided increased intraocular antibiotic absorption and improved prevention and treatment of ocular keratitis, and the formulation approach is highly translational and clinically relevant.

Diabetic eye: associated diseases, drugs in clinic, and role of self-assembled carriers in topical treatment

Introduction: Diabetes is a pandemic disease that causes relevant ocular pathologies. Diabetic retinopathy, macular edema, cataracts, glaucoma, or keratopathy strongly impact the quality of life of the patients. In addition to glycemic control, intense research is devoted to finding more efficient ocular drugs and improved delivery systems that can overcome eye barriers. Areas covered: The aim of this review is to revisit first the role of diabetes in the development of chronic eye diseases. Then, commercially available drugs and new candidates in clinical trials are tackled together with the pros and cons of their administration routes. Subsequent sections deal with self-assembled drug carriers suitable for eye instillation combining patient-friendly administration with high ocular bioavailability. Performance of topically administered polymeric micelles, liposomes, and niosomes for the management of diabetic eye diseases is analyzed in the light of ex vivo and in vivo results and outcomes of clinical trials. Expert opinion: Self-assembled carriers are being shown useful for efficient delivery of not only a variety of small drugs but also macromolecules (e.g. antibodies) and genes. Successful design of drug carriers may offer alternatives to intraocular injections and improve the treatment of both anterior and posterior segments diabetic eye diseases.

Pharmaceutical-loaded contact lenses as an ocular drug delivery system: A review of critical lens characterization methodologies with reference to ISO standards

Therapeutic contact lenses for ocular drug delivery have received considerable interest as they can potentially enhance ocular bioavailability, increase patient compliance, and reduce side effects. Along with the successful in vitro and in vivo studies on sustained drug delivery through contact lenses, lens critical properties such as water content, optical transparency and modulus have also been investigated. Aside from issues such as drug stability or burst release, the potential for the commercialization of pharmaceutical-loaded lenses can be limited by the alteration of lens physical and chemical properties upon the incorporation of therapeutic or non-therapeutic components. This review outlines advances in the use of pharmaceutical-loaded contact lenses and their relevant characterization methodologies as a potential ocular drug delivery system from 2010 to 2020, while summarizing current gaps and challenges in this field. A key reference point for this review is the relevant ISO standards on contact lenses, relating to the associated characterization methodologies. The content of this review is categorized based on the chemical, physical and mechanical properties of the loaded lens with the shortcomings of such analytical technologies examined.

Recent Advances in the Excipients Used for Modified Ocular Drug Delivery

In ocular drug delivery, maintaining an efficient concentration of the drug in the target area for a sufficient period of time is a challenging task. There is a pressing need for the development of effective strategies for drug delivery to the eye using recent advances in material sciences and novel approaches to drug delivery. This review summarizes the important aspects of ocular drug delivery and the factors affecting drug absorption in the eye including encapsulating excipients (chitosan, hyaluronic acid, poloxamer, PLGA, PVCL-PVA-PEG, cetalkonium chloride, and gelatin) for modified drug delivery.

Studying the ophthalmic toxicity potential of developed ketoconazole loaded nanoemulsion in situ gel formulation for ophthalmic administration

Ocular fungal infections are one of the essential reasons for vision loss, especially in developing countries for tropical regions. Ketoconazole (KZ), a broad-spectrum antifungal drug, is a lipophilic compound and practically insoluble in water. Since topical ophthalmic drug delivery confronts low bioavailability, an in situ gel formulation is designed to improve the residence time and consequently the bioavailability. Safety of the developed formulation as a carrier for ophthalmic drug delivery was measured using three different methods: MTT assay for measuring cell viability in which the human retinal pigmentation epithelial cells (RPE) were used, HET-CAM as a borderline method between in vivo and in vitro techniques for investigating the irritation potential of the chosen formulation which was done by adding formulation directly on the CAM surface and visually monitoring the vessels in terms of irritation reactions, and finally the modified Draize test for evaluating tolerability of the selected formulation on eyes. According to our results from the MTT test, cell viability for KZ-NE in situ gel formulation at 0.1% concentration was acceptable. The results obtained from the HET-CAM investigation didn't show any sign of vessel injury on the CAM surface for prepared formulation. Additionally, during 24 hours, the developed formulation was tolerable by rabbit eyes. Regarding our results, KZ-NE in situ gel formulation was non-irritant and non-toxic and can be well-tolerated and presented as an applicable vehicle for ophthalmic delivery of the anti-fungal drug.

The Emerging Role of Topical Ocular Drugs to Target the Posterior Eye

The prevalence of chronic fundus diseases is increasing with the aging of the general population. The treatment of these intraocular diseases relies on invasive drug delivery because of the globular structure and multiple barriers of the eye. Frequent intraocular injections bring heavy burdens to the medical care system and patients. The use of topical drugs to treat retinal diseases has always been an attractive solution. The fast development of new materials and technologies brings the possibility to develop innovative topical formulations. This article reviews anatomical and physiological barriers of the eye which affect the bioavailability of topical drugs. In addition, we summarize innovative topical formulations which enhance the permeability of drugs through the ocular surface and/or extend the drug retention time in the eye. This article also reviews the differences of eyes between different laboratory animals to address the translational challenges of preclinical models. The fast development of in vitro eye models may provide more tools to increase the clinical translationality of topical formulations for intraocular diseases. Clinical successes of topical formulations rely on continuous and collaborative efforts between different disciplines.

Design and Development of Antibacterial/Anti-inflammatory Dual Drug-Loaded Nanofibrous Inserts for Ophthalmic Sustained Delivery of Gentamicin and Methylprednisolone: In Vitro Bioassay, Solvent, and Method Effects’ Evaluation

Purpose: To overcome the challenges caused by the use of conventional ophthalmic dosage forms such as the fast elimination of the drug from the surface of the eye, in this study, dual drug-loaded nanofibers were developed for sustained ophthalmic delivery of gentamicin (GNT) and methylprednisolone (MP). Moreover, the solvent effects, polymer mixtures, and method of preparation on the release profile of the prepared nanofibers, were evaluated.

Methods: The nanofibers were prepared using polycaprolactone (PCL), poly (lactic-co-glycolic acid) (PLGA), and polyvinyl alcohol (PVA) using electrospinning technique. Thereafter, seven optimized formulations were developed with different solvent mixtures and polymer concentrations using various electrospinning methods. The physicochemical and mechanical properties of nanofibers were also evaluated, and the morphology of formulations was observed. The antibacterial efficacy was investigated and the in vitro release amounts of GNT and MP from nanofibers were estimated using the bioassay and ultraviolet-visible (UV-Vis) spectroscopy.

Results: The developed G1, G4, G5, G6, and G7 had suitable mechanical properties and morphologies with diameter ranging between 70-350 nm. The 1:1 v/v ratio of DMF/DCM in the solvent mixture and using core-shell technique for the preparation, formed nanofibers with more favorable release profiles. The optimized formulations indicated sustained-release manner for both drugs during 3-9 days and the antibacterial efficacy against Staphylococcus aureus.

Conclusion: Among all the prepared formulations, the nanofiber with core-shell structure possessed the best sustained-release profiles of GNT and MP. The obtained results suggest that these nanofibers have a potential to be used as an insert in the eye for long-term release of the drug.

Ocular microemulsion of brinzolamide: Formulation, physicochemical characterization, and in vitro irritation studies based on EpiOcular™ eye irritation assay

In recent years, the hydrophobic active substances have led researchers to develop new formulations to enhance bioavailability and dissolution rate; brinzolamide, a lipophilic drug belongs to carbonic anhydrase inhibitors, which cause reduction of intraocular pressure in patients suffering from glaucoma. Currently, the marketed product of brinzolamide is in the form of ocular drops; nonetheless, the conventional drops provide decreased therapeutic efficacy owing to their low bioavailability and pulsed drug release. Thus, the development of novel ocular formulations such as topical microemulsions is of high importance. In this work, the preparation of new microemulsions containing brinzolamide (0.2, 0.5 and 1% w/w) and comprised from isopropyl myristate, tween 80 and span 20 and Cremophor EL was performed. The obtained microemulsions were further characterized for their physicochemical properties. In addition, Fourier Transformed-Infrared spectroscopy was used touate the compatibility of active ingredients and components. In vitro release studies along with kinetic modeling were performed using the dialysis membrane method in simulated tear fluid. Bioadhesion studies were performed using Texture analysis. Finally, in vitro ocular irritation based on EpiOcular™ Eye Irritation Test and cytocompatibility studies was performed to examine any possible harm on ocular cells and predict in vivo safety profile.

Ophthalmic Sensors and Drug Delivery

Advances in multifunctional materials and technologies have allowed contact lenses to serve as wearable devices for continuous monitoring of physiological parameters and delivering drugs for ocular diseases. Since the tear fluids comprise a library of biomarkers, direct measurement of different parameters such as concentration of glucose, urea, proteins, nitrite, and chloride ions, intraocular pressure (IOP), corneal temperature, and pH can be carried out non-invasively using contact lens sensors. Microfluidic contact lens sensor based colorimetric sensing and liquid control mechanisms enable the wearers to perform self-examinations at home using smartphones. Furthermore, drug-laden contact lenses have emerged as delivery platforms using a low dosage of drugs with extended residence time and increased ocular bioavailability. This review provides an overview of contact lenses for ocular diagnostics and drug delivery applications. The designs, working principles, and sensing mechanisms of sensors and drug delivery systems are reviewed. The potential applications of contact lenses in point-of-care diagnostics and personalized medicine, along with the significance of integrating multiplexed sensing units together with drug delivery systems, have also been discussed.

Preclinical Evaluations of Modified Rice Hydrogel for Topical Ophthalmic Drug Delivery of Praziquantel on Avian Philophalmiasis

The present study aims to evaluate the efficacy of a novel drug delivery system of the modified rice hydrogel containing praziquantel (PZQ) against Philophthalmus gralli isolated from ostrich eyes and determine the toxicity of the preparation on chicken eye model. The parasiticidal activity of PZQ (0, 1, 10, and 100 µg/mL) was tested on P. gralli. The ophthalmic antiparasitic hydrogel was formulated with appropriate amount of PZQ and chemically modified rice gel. The parasitic morphology after exposure with the preparation was examined under scanning electron microscope (SEM). The anthelminthic efficacy of the preparation on motility and mortality of parasites was performed by visual inspection and vital dye staining. The ocular irritation of the preparation was evaluated for 21 days using standard avian model followed by OECD 405. The results demonstrated that the parasiticidal activity of PZQ against P. gralli appears to be in a concentration- and time-dependent manner. In addition, the concentration of PZQ 10 µg/mL (Chi squared test, p = 0.003) and exposure time for 24 h (log-rank test, p = 0.0004) is sufficient to kill parasites, when statistically compared to negative control group. Rice hydrogel containing a lethal concentration of 10 µg/mL PZQ was successfully prepared. The preparation illustrated good parasitic killing and motile inhibiting effect on P. gralli compared with PZQ 10 µg/mL and its control (p < 0.05). An appearance under SEM of non-viable parasite after being incubated with the preparation, showing parasitic deformity, was observed comparing with the viable parasite in 0.9% normal saline solution (NSS). Moreover, no irritation of chicken eyes was also observed. Our results contribute to understanding the efficacy and the safety of the rice hydrogel of PZQ which have a predictive value for controlling P. gralli on the animal eyes. However, the pharmacological application needs to be further investigated for the best possible therapeutic approach.

Delivery of siRNA to the Eye: Protocol for a Feasibility Study to Assess Novel Delivery System for Topical Delivery of siRNA Therapeutics to the Ocular Surface

Drug delivery to the eye remains a real challenge due to the presence of ocular anatomical barriers and physiological protective mechanisms. The lack of effective siRNA delivery mechanism has hampered the real potential of RNAi therapy, but recent literature suggests that nanocarrier systems show great promise in enhancing siRNA bioavailability and reducing the need for repeated intraocular injections. A diverse range of materials are under exploration worldwide, including natural and synthetic polymers, liposomes, peptides, and dendrimeric nanomaterials. This chapter describes a simple workflow for feasibility assessment of a proposed ocular surface siRNA delivery system. Gel retardation assay is used for investigation of optimal siRNA to carrier loading ratio. Fluorescent siRNA allows for initial in vitro testing of cellular uptake to corneal epithelial cells and investigation of in vivo siRNA delivery into mouse cornea by live animal imaging and fluorescence microscopy.

Ocular drug delivery to the anterior segment using nanocarriers: A mucoadhesive/mucopenetrative perspective

There is a growing demand for effective treatments for ocular conditions that improve patient compliance and reduce side-effects. While methods such as implants and injections have proven effective, topical administration remains the method of choice for the delivery of therapeutics to the anterior segment of the eye. However, topical administration suffers from multiple drawbacks including low bioavailability of the target therapeutic, systemic toxicity, and the requirement for high therapeutic doses due to the effective clearance mechanisms that exist in the eye. Nanoparticles that have tunable mucoadhesion and/or mucopenetration offer outstanding potential to overcome the anatomical and physiological barriers present to improve ocular bioavailability, reduce toxicity, and increase ocular retention, among other benefits. The current review highlights recent advances in the field of developing nanocarriers with tunable mucoadhesion and mucopenetration for drug delivery to the eye.

Design and In Vitro Evaluation of a Slow-Release Intraocular Implant of Betamethasone

Posterior eye diseases are a common cause of vision problems in developing countries, which have encouraged the development of new treatment models for these degenerative diseases. Intraocular implants are one of the drug delivery systems to the posterior region of the eye. Using these implants, the blood-eye barrier can be bypassed; the complications caused by repeated in vitro administrations can be eliminated, and smaller amounts of the drug would be used during the treatment process. Meanwhile, biodegradable implants have received more attention due to their biodegradable structure and the lack of need for re-surgery to remove the rest of the system from the eye. The aim of this study is to employ biodegradable implants composed of polyethylene glycol (PEG) and 3-hydroxybutyrate-co-3-hydroxyvalerat (PHBV) to deliver betamethasone to the back of the eye in the treatment of retinopathy. PHBV polymer has been selected as the main polymer with a certain ratio of drug to polymer for fabrication of enamel and different amounts of PEG with three molecular weights used as pore generators to control drug release over a period of time. Based on the analysis of the results of differential scanning calorimetry (DSC) and FTIR spectroscopy, none of the polymers were degraded in the temperature range of the manufacturing process, and among betamethasone derivatives, the best option for implant preparation is the use of its basic form. Drug release studies over a period of three months showed that implants containing PHBV HV2% and PEG 6000 had a more appropriate release profile.

NO, CO and H2S based pharmaceuticals in the mission of vision (eye health): a comprehensive review

A set of well defined signaling molecules responsible for normal functioning of human physiology including nitric oxide along with carbon monoxide and hydrogen sulphide are referred as “gasotransmitters”. Due to their involvement in almost every system of a human body, the care of highly sensitive organs using these molecules as drugs represents highly fascinating area of research. In connection with these interesting aspects, the applied aspects of these gaseous molecules in maintaining healthy eye and vision have been targeted in this review. Several examples of eye-droppers including NORMs like latanoprost and nipradiol, CORMs like CORM-3 and CORM-A1, and Hydrogen sulfide releasing system like GYY4137 have been discussed in this context. Therefore the relation of these trio-gasotransmitters with the ophthalmic homeostasis on one hand, and de-infecting role on the other hand has been mainly highlighted. Some molecular systems capable of mimicking gasotransmitter action have also been introduced in connection with the titled theme.

Predictive Platforms of Bond Cleavage and Drug Release Kinetics for Macromolecule–Drug Conjugates

Macromolecule–drug conjugates (MDCs) occupy a critical niche in modern pharmaceuticals that deals with the assembly and combination of a macromolecular carrier, a drug cargo, and a linker toward the creation of effective therapeutics. Macromolecular carriers such as synthetic biocompatible polymers and proteins are often exploited for their inherent ability to improve drug circulation, prevent off-target drug cytotoxicity, and widen the therapeutic index of drugs. One of the most significant challenges in MDC design involves tuning their drug release kinetics to achieve high spatiotemporal precision. This level of control requires a thorough qualitative and quantitative understanding of the bond cleavage event. In this review, we highlight specific research findings that emphasize the importance of establishing a precise structure–function relationship for MDCs that can be used to predict their bond cleavage and drug release kinetic parameters.

Intellective and stimuli-responsive drug delivery systems in eyes

Stimuli-responsive drug delivery systems have attracted widespread attention in recent years since they can control drug release in a spatiotemporal manner and can achieve tunable drug release according to patient's physiological or pathological condition. In this review, we briefly introduce the drug delivery barriers and drug delivery systems in the anterior and posterior segment of eyes, and collect the recent advances in stimuli-responsive drug delivery systems in eyes for controlled drug release in response to exogenous stimuli (ultrasound, magnetic stimulus, electrical stimulus, and light) or endogenous stimuli (enzyme, active oxygen species, temperature, ions, and pH). In addition, the design and mechanisms of the stimuli-responsive drug delivery systems have been summarized in this review, and the advantages and limitations are also briefly discussed.

In vivo photoacoustic imaging for monitoring treatment outcome of corneal neovascularization with metformin eye drops

Corneal neovascularization (CNV) compromises corneal avascularity and visual acuity. Current clinical visualization approaches are subjective and unable to provide molecular information. Photoacoustic (PA) imaging offers an objective and non-invasive way for angiogenesis investigation through hemodynamic and oxygen saturation level (sO₂) quantification. Here, we demonstrate the utility of PA and slit lamp microscope for in vivo rat CNV model. PA images revealed untreated corneas exhibited higher sO₂ level than treatment groups. The PA results complement with the color image obtained with slit lamp. These data suggest PA could offer an objective and non-invasive method for monitoring CNV progression and treatment outcome through the sO₂ quantification.

In vivo drug delivery via contact lenses: The current state of the field from origins to present

Over the past half century, contact lenses have been investigated for their potential as drug delivery devices for ocular therapeutics. Hundreds of studies have been published in the pursuit of the most effective and efficient release strategies and methods for contact lens drug delivery. This paper provides a thorough overview of the various contact lens drug delivery strategies, with a specific, comprehensive focus on in vivo studies that have been published since the field began in 1965. Significant accomplishments, current trends, as well as future strategies and directions are highlighted. In vivo study analysis provides a straightforward perspective and assessment of method success and commercialization potential in comparison to benchtop, in vitro studies. Analysis of the majority of published work indicates in vitro and in vivo studies do not correlate with a correlation coefficient of 0.25, with many in vitro studies grossly overestimating drug release duration and not showing appreciable drug release control. However, there has been an increase in activity in the last decade, and some methods have generated promising results exhibiting controlled release with commercialization potential. Clinical translation of drug releasing lenses is on the horizon and has high potential to impact a large number of patients providing efficacious treatment compared to current topical treatments.

Evaluation of the Presence and Functional Importance of Nucleoside Transporters in Lacrimal Gland for Tear Disposition of Intravenously Injected Substrate in Rabbits

Purpose: Purpose of the current study was to assess the presence and functionality of the nucleoside transporters in the lacrimal gland for the tear disposition of its substrate given intravenously in rabbits.Materials and Methods: Rabbits were divided into two groups - control and blocker pretreated. The blocker pretreated group received 5 mg/kg of dipyridamole 30 min before ribavirin (substrate), which was given at a dose of 2.5 mg/kg. All the treatments were given intravenously. Blood and tear samples were collected at 5, 15, 30, 60, 90, 120, 180, 240, 300 and 360 min (n = 4; each time point) after substrate administration. Tear samples were collected on Schirmer's strips, and plasma was separated immediately after blood collection. All the samples were stored at -80°C until analysis by LC-MS/MS.Results: Plasma ribavirin concentration for blocker pretreated group showed significantly (p < .05) higher levels at 5, 15, 30, 60, 120, 180 and 300 min as compared to the control group. Similarly, tear ribavirin concentration for blocker pretreated group also showed a significant (p < .05) increase at 5, 15, 60, 90, 180, 240 and 300 min compared to the control group. Plasma and tear AUC_(0-6) for blocker pretreated group was 1.7 (p < .001) and 2.42 (p < .001) folds higher in a significant manner as compared to the control group, respectively. Percentage penetration of ribavirin from plasma to tears was also different between control and blocker pretreated group. Permeation ratio of ribavirin from plasma to tear for blocker pretreated group was found to be 1.4-folds higher in a significant (p < .05) manner.Conclusion: It is evident from the results that nucleoside transporters are present in lacrimal gland. The blocker treatment induced increase in tear transport of ribavirin indicates the possibility of the presence of nucleoside transporters on the apical side of lacrimal acinar cells in the uptake position.

Effect of Poly(L-lysine) and Heparin Coatings on the Surface of Polyester-Based Particles on Prednisolone Release and Biocompatibility

A plethora of micro- and nanoparticle types are currently investigated for advanced ocular treatment due to improved drug retention times, higher bioavailability and better biocompatibility. Yet, comparative studies of both physicochemical and toxicological performance of these novel drug delivery systems are still rare. Herein, poly(L-lactic acid)- and poly(ε-caprolactone)-based micro- and nanoparticles were loaded with prednisolone as a model drug. The physicochemical properties of the particles were varied with respect to their hydrophilicity and size as well as their charge and the effect on prednisolone release was evaluated. The particle biocompatibility was assessed by a two-tier testing strategy, combining the EpiOcular^TM eye irritation test and bovine corneal opacity and permeability assay. The biodegradable polyelectrolyte corona on the particles’ surface determined the surface charge and the release rate, enabling prednisolone release for at least 30 days. Thereby, the prednisolone release process was mainly governed by molecular diffusion. Finally, the developed particle formulations were found to be nontoxic in the tested range of concentrations.

Acyclovir-Loaded Nanoemulsions: Preparation, Characterization and Irritancy Studies for Ophthalmic Delivery

Objective: The main goal of the present work was to develop and evaluate nanoemulsions (NEs) containing acyclovir (ACV) for ophthalmic drug delivery.Method: Firstly, component screening was performed by determining ACV solubility in various oils, surfactants, and co-surfactants. Different NE formulations were developed based on pseudo-ternary phase diagrams, and physicochemical assets were evaluated. Selected formulations were subjected to the drug release efficacy, stability studies, and ex-vivo trans-corneal permeation test. The safety of NEs was investigated by the modified Draize test and hen's egg test-chorioallantoic membrane (HET-CAM).Results: Based on the solubility studies, Tween 20, Triacetin, and Tramsectol^®P were chosen to prepare NE formulations. Developed NEs showed desirable physiochemical properties, including a droplet size of less than 15 nm. Selected formulations (F1 and F2) exhibited a sustained drug release pattern compared to the control group (P < .001). ACV penetration from F1 and F2 to the excised bovine cornea was 2.85 and 2.9-fold more than the control, respectively. Furthermore, HET-CAM and modified Draize test confirmed that F1 and F2 were safe for ocular administration.Conclusion: Present investigation revealed that ACV-loaded NEs could be effective, and safe platform for ophthalmic delivery of ACV.

Age-related ocular conditions: Current treatments and role of cyclodextrin-based nanotherapies

Age-related eye disorders are chronic diseases that affect millions of people worldwide. They cause visual impairment and, in some cases, irreversible blindness. Drug targeting to the retina is still a challenge due to the difficulties with drug distribution, crossing eye barriers, and reaching intraocular tissues in an effective therapeutic concentration. Although intravitreal injections can directly deliver drugs to the posterior segment of the eye, it remains an invasive technique and leads to several side effects. Conventional formulations such as emulsions, suspensions, or ointments have been related to frequent instillation and inability to reach intraocular tissues. New drug delivery systems and medical devices have also been designed. Nevertheless, these treatments are not always effective and sometimes require the presence of a specialist for the administration of the dose. Therefore, treatments for age-related ocular diseases remain as one of the major unmet clinical needs to manage these widespread eye conditions. Nanotechnology may become the adequate tool for developing effective and non-invasive therapies suitable for self-administration. In this review, we discuss emerging therapeutic options based on nanoengineering of cyclodextrin nanocarriers for the treatment of age-related eye disorders, including their pathophysiology, pharmacological options, and feasibility of clinical translation.

Lipid-Based Nanocarriers as Topical Drug Delivery Systems for Intraocular Diseases

Effective drug delivery to intraocular tissues remains a great challenge due to complex anatomical and physiological barriers that selectively limit the entry of drugs into the eye. To overcome these challenges, frequent topical application and regular intravitreal injections are currently used to achieve the desired drug concentrations into the eye. However, the repetitive installation or recurrent injections may result in several side effects. Recent advancements in the field of nanoparticle-based drug delivery have demonstrated promising results for topical ophthalmic nanotherapies in the treatment of intraocular diseases. Studies have revealed that nanocarriers enhance the intraocular half-life and bioavailability of several therapies including proteins, peptides and genetic material. Amongst the array of nanoparticles available nowadays, lipid-based nanosystems have shown an increased efficiency and feasibility in topical formulations, making them an important target for constant and thorough research in both preclinical and clinical practice. In this review, we will cover the promising lipid-based nanocarriers used in topical ophthalmic formulations for intraocular drug delivery.

A Review on Newer Ocular Drug Delivery Systems with an Emphasis on Glaucoma

Glaucoma is an irreversible condition resulting from the increase in intraocular pressure (IOP); which leads to permanent loss of vision with the destruction of retinal ganglion cells (RGCs). The IOP elevations are controlled in normal by the physiological flow of aqueous humour. A population with age above 40 is more susceptible to glaucoma. Other factors like gender, genetics, race etc. plays major roles in the development of the disease. Current treatment methods available for the disease includes drugs come under the classes of beta receptor blockers, carbonic anhydrase inhibitors, cholinergic agonists, prostaglandins etc. N-methyl-D-aspartate (NMDA) antagonists, inducible nitric oxide synthase (iNOS) inhibition, cytoskeletal agents, Rho-kinase inhibitors etc are few novel targets sites which are in research focus for the treatment of the disease. Developments in nanomedicine are also being evaluated for their potential in treating the growing glaucomatous population. Nanosystems are suggested to avoid the difficulties in tackling the various ocular barriers to a limit, help to decrease the instillation frequency of topical medication and can provide drug delivery in a sustained or controlled manner. This review focuses on the current and emerging treatment methods for glaucoma along with some of the nanoformulations for ocular drug delivery.

Borneol: a Promising Monoterpenoid in Enhancing Drug Delivery Across Various Physiological Barriers

Incorporation of permeation enhancers is one of the most widely employed approaches for delivering drugs across biological membranes. Permeation enhancers aid in delivering drugs across various physiological barriers such as brain capillary endothelium, stratum corneum, corneal epithelium, and mucosal membranes that pose resistance to the entry of a majority of drugs. Borneol is a natural, plant-derived, lipophilic, volatile, bicyclic monoterpenoid belonging to the class of camphene. It has been used under the names "Bing Pian" or "Long Nao" in Traditional Chinese Medicine for more than 1000 years. Borneol has been incorporated predominantly as an adjuvant in the traditional Chinese formulations of centrally acting drugs to improve drug delivery to the brain. This background knowledge and anecdotal evidence have led to extensive research in establishing borneol as a permeation enhancer across the blood-brain barrier. Alteration in cell membrane lipid structures and modulation of multiple ATP binding cassette transporters as well as tight junction proteins are the major contributing factors to blood-brain barrier opening functions of borneol. Owing to these mechanisms of altering membrane properties, borneol has also shown promising potential to improve drug delivery across other physiological barriers as well. The current review focuses on the role of borneol as a permeation enhancer across the blood-brain barrier, mucosal barriers including nasal and gastrointestinal linings, transdermal, transcorneal, and blood optic nerve barrier.

Lipid Nanoparticles as Carriers for Bioactive Delivery

Nanotechnology has made a great impact on the pharmaceutical, biotechnology, food, and cosmetics industries. More than 40% of the approved drugs are lipophilic and have poor solubility. This is the major rate-limiting step that influences the release profile and bioavailability of drugs. Several approaches have been reported to administer lipophilic drugs with improved solubility and bioavailability. Nanotechnology plays a crucial role in the targeted delivery of poorly soluble drugs. Nanotechnology-based drug delivery systems can be classified as solid lipid nanoparticulate drug delivery systems, emulsion-based nanodrug delivery systems, vesicular drug delivery systems, etc. Nanotechnology presents a new frontier in research and development to conquer the limitations coupled with the conventional drug delivery systems through the formation of specific functionalized particles. This review presents a bird's eye view on various aspects of lipid nanoparticles as carriers of bioactive molecules that is, synthesis, characterization, advantage, disadvantage, toxicity, and application in the medical field. Update on recent development in terms of patents and clinical trials of solid lipid nanoparticles (SLNs) and nanostructure lipid carriers (NLCs) have also been discussed in this article.

Gene therapy in the anterior eye segment

This review provides comprehensive information about the advances in gene therapy in the anterior segment of the eye including cornea, conjunctiva, lacrimal gland, and trabecular meshwork. We discuss gene delivery systems including viral and non-viral vectors as well as gene editing techniques, mainly CRISPR-Cas9, and epigenetic treatments including antisense and siRNA therapeutics. We also provide a detailed analysis of various anterior segment diseases where gene therapy has been tested with corresponding outcomes. Disease conditions include corneal and conjunctival fibrosis and scarring, corneal epithelial wound healing, corneal graft survival, corneal neovascularization, genetic corneal dystrophies, herpetic keratitis, glaucoma, dry eye disease, and other ocular surface diseases. Although most of the analyzed results on the use and validity of gene therapy at the ocular surface have been obtained in vitro or using animal models, we also discuss the available human studies. Gene therapy approaches are currently considered very promising as emerging future treatments of various diseases, and this field is rapidly expanding.

Nanotechnology: revolutionizing the delivery of drugs to treat age-related macular degeneration

Introduction: Age-related macular degeneration (AMD) is a progressive retinal disease that degrades the eye's ability to grasp visual acuity. The antivascular endothelial growth factor (VEGF) therapies have made significant strides in improving the quality of life, and there is a continued opportunity to improve delivery, outcomes, and patient convenience and compliance. The treatments available could gain better clinical outcome from novel therapeutics through nanotechnology application.Areas covered: This review summarizes AMD biology and the pathophysiology of the disease along with the successes and limitations of available therapies. It further discusses the promising nanotechnology modalities that could become the cornerstone of future AMD research for improving delivery and reducing frequency of administration thus, enabling development of novel therapeutics.Expert opinion: The robust translation from preclinical work to clinical outcome for AMD remains an unmet need. Continuing to investigate in deeper understanding of biology and advancing high-quality targets into the clinic in combination with the application of advanced nanotechnology to design patient-centric offerings for both dry and wet AMD is needed. Because of the lack of regulatory precedence, and challenging manufacturing and supply chain need, the future of nano-enabled technologies is challenging but presents exciting treatment options for AMD.

Advancing the treatment of juvenile idiopathic arthritis

Treatment for juvenile idiopathic arthritis has undergone substantial changes in recent decades. These changes are partly due to the availability of new treatments, mainly biological agents, as well as developments in treatment strategies, including a focus on concepts such as treat-to-target. In addition, the creation of large paediatric research networks has improved patient access to, and design of, clinical trials for rare paediatric diseases. Although these advances have resulted in improvements in care for most patients with juvenile idiopathic arthritis, certain subgroups of patients continue to have a poor prognosis. Further research aims to identify patients in these subgroups early, to personalise their care, improve functional outcomes, and minimise long-term damage and harm. Optimising the duration of therapy for those individuals who require systemic immunosuppression is also of importance. Incorporation of novel biomarkers in combination with validated clinical measures in an effort to predict outcomes and target therapy accordingly is an exciting development.

Lipid-Based Nanocarriers for Ophthalmic Administration: Towards Experimental Design Implementation

Nanotherapeutics based on biocompatible lipid matrices allow for enhanced solubility of poorly soluble compounds in the treatment of ophthalmic diseases, overcoming the anatomical and physiological barriers present in the eye, which, despite the ease of access, remains strongly protected. Micro-/nanoemulsions, solid lipid nanoparticles (SLN) or nanostructured lipid carriers (NLC) combine liquid and/or solid lipids with surfactants, improving drug stability and ocular bioavailability. Current research and development approaches based on try-and-error methodologies are unable to easily fine-tune nanoparticle populations in order to overcome the numerous constraints of ocular administration routes, which is believed to hamper easy approval from regulatory agencies for these systems. The predictable quality and specifications of the product can be achieved through quality-by-design (QbD) implementation in both research and industrial environments, in contrast to the current quality-by-testing (QbT) framework. Mathematical modelling of the expected final nanoparticle characteristics by variation of operator-controllable variables of the process can be achieved through adequate statistical design-of-experiments (DoE) application. This multivariate approach allows for optimisation of drug delivery platforms, reducing research costs and time, while maximising the understanding of the production process. This review aims to highlight the latest efforts in implementing the design of experiments to produce optimised lipid-based nanocarriers intended for ophthalmic administration. A useful background and an overview of the different possible approaches are presented, serving as a starting point to introduce the design of experiments in current nanoparticle research.

The effects of addition of functional monomers and molecular imprinting on dual drug release from intraocular lens material

Although cataract surgery is considered a safe procedure, post-surgery complications such as endophthalmitis and ocular inflammation, may occur. To prevent this, antibiotics and anti-inflammatories are prescribed in the form of eye drops during the post-operatory period, but they lead to a low drug bioavailability in target tissues. The objective of this work is to develop an intraocular lens (IOL) material to deliver simultaneously one antibiotic, moxifloxacin (MXF), and one anti-inflammatory, diclofenac (DFN), in therapeutic concentrations to prevent both complications. The IOL material was modified through the incorporation of functional monomers, as well as molecular imprinting with both drugs using the same functional monomers, namely acrylic acid (AA), methacrylic acid (MAA), 4-vinylpiridine (4-VP) and a combination of MAA + 4-VP. The best results were obtained with MAA. Molecular imprinting did not influence the drug release, except with AA. Application of a mathematical model predicted that the released MXF and DFN concentrations would stay above the pre-determined MIC of S. aureus and S. epidermidis and the minimum values of IC50 of COX-1 and COX-2, for 9 and 14 days, respectively. Antibacterial tests showed that the released antibiotic remained active. The physical properties of the drug-loaded MAA-hydrogel remained adequate. The developed system proved to be non-irritant and non-cytotoxic.

Emerging innovations in nano-enabled therapy against age-related macular degeneration: A paradigm shift

Age-related macular degeneration (AMD), a degenerative eye disease, is the major cause of irreversible loss of vision among individuals aged 50 and older. Both genetic and environmental factors are responsible for the progressive damage to central vision. It is a multifactorial retinal disease with features such as drusen, hypopigmentation and/or hyperpigmentation of the retinal pigment epithelium, and even choroidal neovascularization in certain patients. AMD is of two major forms: exudative (wet) and atrophic (dry) with changes affecting the macula leading to impaired vision. Although the retina remains an accessible portion for delivering drugs, there are no current options to cure or treat AMD. The existing expensive therapeutics are unable to treat the underlying pathology but display several side effects. However, recent innovations in nanotherapeutics provide an optimal alternative of drug delivery to treat the neovascular condition. These new-age technologies in the nanometer scale would enhance bioactivity and improve the bioavailability of drugs at the site of action to treat AMD. The nanomedicine also provides sustained release of the drug with prolonged retention after penetrating across the ocular tissues. In this review, the insights into the cellular and molecular mechanisms associated with the pathophysiology of AMD are provided. It also serves to review the current progress in nanoparticle-based drug delivery systems that offer feasible treatments in AMD.

Key advances of carboxymethyl cellulose in tissue engineering & 3D bioprinting applications

Carboxymethyl cellulose (CMC) is a water-soluble derivative of cellulose and a major type of cellulose ether prepared by the chemical attack of alkylating reagents on the activated non-crystalline regions of cellulose. It is the first FDA approved cellulose derivative which can be targeted for desired chemical modifications. In this review, the properties along with current advances in the physical and chemical modifications of CMC are discussed. Further, CMC and modified CMC could be engineered to fabricate scaffolds for tissue engineering applications. In recent times, CMC and its derivatives have been developed as smart bioinks for 3D bioprinting applications. From these perspectives, the applications of CMC in tissue engineering and current knowledge on peculiar features of CMC in 3D and 4D bioprinting applications are elaborated in detail. Lastly, future perspectives of CMC for wider applications in tissue engineering and 3D/4D bioprinting are highlighted.

Enhanced in vivo antifungal activity of novel cell penetrating peptide natamycin conjugate for efficient fungal keratitis management

Natamycin is the only FDA approved drug that is used as a first line of treatment for fungal keratitis caused by filamentous fungi, however natamycin is known for poor corneal penetration. Cell penetrating peptides (CPPs) are emerging nanocarriers for the enhanced delivery of various macromolecules owing to their distinct cellular translocation ability. In the present study, tissue penetration ability and antifungal efficacy of CPP (Tat₂) conjugated natamycin has been investigated and compared with natamycin alone in vivo. Results show that Tat₂natamycin exhibits five- fold higher ocular penetration than natamycin alone when given topically. Complete resolution of fungal keratitis in 44% of the animals in Tat₂natamycin treated group as compared to only 13% of the animals in natamycin treated group further highlights its increased antifungal efficacy. Hence, this conjugate is a promising antifungal molecule with enhanced ocular penetration as well as antifungal efficacy against selected fungal species.