Novel Approaches for Retinal Drug and Gene Delivery

Advancements in Nanogels for Enhanced Ocular Drug Delivery: Cutting-Edge Strategies to Overcome Eye Barriers

Nanomedicine in gel or particle formation holds considerable potential for enhancing passive and active targeting within ocular drug delivery systems. The complex barriers of the eye, exemplified by the intricate network of closely connected tissue structures, pose significant challenges for drug administration. Leveraging the capability of engineered nanomedicine offers a promising approach to enhance drug penetration, particularly through active targeting agents such as protein peptides and aptamers, which facilitate targeted release and heightened bioavailability. Simultaneously, DNA carriers have emerged as a cutting-edge class of active-targeting structures, connecting active targeting agents and illustrating their potential in ocular drug delivery applications. This review aims to consolidate recent findings regarding the optimization of various nanoparticles, i.e., hydrogel-based systems, incorporating both passive and active targeting agents for ocular drug delivery, thereby identifying novel mechanisms and strategies. Furthermore, the review delves into the potential application of DNA nanostructures, exploring their role in the development of targeted drug delivery approaches within the field of ocular therapy.

Potential therapeutic strategies for photoreceptor degeneration: the path to restore vision

Photoreceptors (PRs), as the most abundant and light-sensing cells of the neuroretina, are responsible for converting light into electrical signals that can be interpreted by the brain. PR degeneration, including morphological and functional impairment of these cells, causes significant diminution of the retina's ability to detect light, with consequent loss of vision. Recent findings in ocular regenerative medicine have opened promising avenues to apply neuroprotective therapy, gene therapy, cell replacement therapy, and visual prostheses to the challenge of restoring vision. However, successful visual restoration in the clinical setting requires application of these therapeutic approaches at the appropriate stage of the retinal degeneration. In this review, firstly, we discuss the mechanisms of PR degeneration by focusing on the molecular mechanisms underlying cell death. Subsequently, innovations, recent developments, and promising treatments based on the stage of disorder progression are further explored. Then, the challenges to be addressed before implementation of these therapies in clinical practice are considered. Finally, potential solutions to overcome the current limitations of this growing research area are suggested. Overall, the majority of current treatment modalities are still at an early stage of development and require extensive additional studies, both pre-clinical and clinical, before full restoration of visual function in PR degeneration diseases can be realized.

Application of Nanomaterials in the Treatment and Diagnosis of Ophthalmology Diseases

Eye diseases often lead to impaired vision and seriously affect the daily life of patients. Local administration of ophthalmic drugs is one of the most important approaches for the treatment of ophthalmic diseases. However, due to the special biochemical environment of the ocular tissue and the existence of many barriers, the bioavailability of conventional ophthalmic preparations in the eye is very low. Nanomaterials can be utilized as carriers of drugs, which can improve the absorption, distribution, metabolism and bioavailability of drugs in eyes. Nanomaterials have also the advantages of small size, simple preparation, good degradability, strong targeting, and little stimulation to biological tissues, providing an innovative and practical method for the drug delivery of ophthalmic diseases. In addition, nanomaterials can be used as an auxiliary means for early diagnosis of ophthalmic diseases by improving the specificity and accuracy of detection methods. Nanomaterials help clinicians and researchers delve deeper into the physiology and pathology of the eye at the nanoscale. We summarize the application of nanomaterials in the diagnosis and treatment of ophthalmic diseases in this review.

Nano-Biomaterials for Retinal Regeneration

Nanoscience and nanotechnology have revolutionized key areas of environmental sciences, including biological and physical sciences. Nanoscience is useful in interconnecting these sciences to find new hybrid avenues targeted at improving daily life. Pharmaceuticals, regenerative medicine, and stem cell research are among the prominent segments of biological sciences that will be improved by nanostructure innovations. The present review was written to present a comprehensive insight into various emerging nanomaterials, such as nanoparticles, nanowires, hybrid nanostructures, and nanoscaffolds, that have been useful in mice for ocular tissue engineering and regeneration. Furthermore, the current status, future perspectives, and challenges of nanotechnology in tracking cells or nanostructures in the eye and their use in modified regenerative ophthalmology mechanisms have also been proposed and discussed in detail. In the present review, various research findings on the use of nano-biomaterials in retinal regeneration and retinal remediation are presented, and these findings might be useful for future clinical applications.

Design, characterisation and drug release study of polymeric, drug-eluting single layer thin films on the surface of intraocular lenses

To design, develop and study a novel drug delivery system for intraocular applications. The spin coating technique was applied to develop a polymeric, drug-eluting thin film consisting of a blend of organic polymers [poly (D, L lactide coglycolide) lactide: glycolide 75: 25, PLGA and polycaprolactone, PCL] and dexamethasone on the surface of intraocular lenses (IOLs). The initial durability of the IOLs during spinning was assessed. Information about the structural and optical properties of the modified IOLs was extracted using atomic force microscopy, scanning electron microscopy and spectroscopic ellipsometry. A drug release study was conducted for 8 weeks. The IOLs were durable in spinning speeds higher than the ones used to develop thin films. Single-layer thin films were successfully developed on the optics and the haptics of the lenses. The films formed nanopores with encapsulated aggregates of dexamethasone. The spectroscopic ellipsometry showed an acceptable optical transparency of the lenses regardless of the deposition of the drug-eluting films on their surface. The drug release study demonstrated gradual dexamethasone release over the selected period. In conclusion, the novel drug-eluting IOL system exhibited desired properties regarding its transparency and drug release rate. Further research is necessary to assess their suitability as an intraocular drug delivery system.

In Vitro and Ex Vivo Evaluation of Nepafenac-Based Cyclodextrin Microparticles for Treatment of Eye Inflammation

The aim of this study was to design and evaluate novel cyclodextrin (CD)-based aggregate formulations to efficiently deliver nepafenac topically to the eye structure, to treat inflammation and increase nepafenac levels in the posterior segment, thus attenuating the response of inflammatory mediators. The physicochemical properties of nine aggregate formulations containing nepafenac/γ-CD/hydroxypropyl-β (HPβ)-CD complexes as well as their rheological properties, mucoadhesion, ocular irritancy, corneal and scleral permeability, and anti-inflammatory activity were investigated in detail. The results were compared with a commercially available nepafenac suspension, Nevanac^® 3 mg/mL. All formulations showed microparticles, neutral pH, and negative zeta potential (–6 to –27 mV). They were non-irritating and nontoxic and showed high permeation through bovine sclera. Formulations containing carboxymethyl cellulose (CMC) showed greater anti-inflammatory activity, even higher than the commercial formulation, Nevanac^® 0.3%. The optimized formulations represent an opportunity for topical instillation of drugs to the posterior segment of the eye.

Noble Metals and Soft Bio-Inspired Nanoparticles in Retinal Diseases Treatment: A Perspective

We are witnessing an exponential increase in the use of different nanomaterials in a plethora of biomedical fields. We are all aware of how nanoparticles (NPs) have influenced and revolutionized the way we supply drugs or how to use them as therapeutic agents thanks to their tunable physico-chemical properties. However, there is still a niche of applications where NP have not yet been widely explored. This is the field of ocular delivery and NP-based therapy, which characterizes the topic of the current review. In particular, many efforts are being made to develop nanosystems capable of reaching deeper sections of the eye such as the retina. Particular attention will be given here to noble metal (gold and silver), and to polymeric nanoparticles, systems consisting of lipid bilayers such as liposomes or vesicles based on nonionic surfactant. We will report here the most relevant literature on the use of different types of NPs for an efficient delivery of drugs and bio-macromolecules to the eyes or as active therapeutic tools.

Topical Nonsteroidal Anti-inflammatory Drugs for Pain Resulting from Intravitreal Injections: A Meta-Analysis

TOPIC

The role of topical nonsteroidal anti-inflammatory drugs (NSAIDs) for the reduction of ocular pain after intravitreal injections (IVIs) has been explored. To provide clarity on the evidence for these agents, the present meta-analysis of randomized controlled trials (RCTs) was undertaken.

CLINICAL RELEVANCE

No standard of care regimen exists for the management of pain resulting from IVIs.

METHODS

A systematic literature search was conducted on Ovid MEDLINE, EMBASE, and Cochrane Central from inception through July 2019. The RCTs that treated patients with a topical NSAID and assessed postprocedural pain were included. Risk of bias was assessed using the Cochrane guidelines. For all analyses, weighted mean differences (WMDs) with 95% confidence intervals (CIs) were reported. Random effects models were used for all analyses. The primary analysis analyzed pain on a 0- to 10-point visual analog scale. Literature estimates were categorized into the following postprocedure time point groups: 1 hour or less, 1 to 24 hours (although data were available only at 6 hours), and 24 hours or more. A subgroup analysis stratified studies based on agent and preprocedure versus postprocedure administration.

RESULTS

From 241 results, 9 RCTs and 598 eyes were included. A low to medium risk of bias was found across the included studies. The mean pain score on a 0-to-10 visual analog scale was significantly lower after topical NSAID administration relative to control at 1 hour or less after IVI (WMD, -1.01 units; 95% CI, -1.38 to -0.65; P < 0.001), 6 hours after IVI (WMD, -2.17 units; 95% CI, -2.67 to -1.68; P < 0.001; threshold met for clinical significance, defined as WMD >1.2 units), and more than 24 hours after IVI (WMD, -0.75 units; 95% CI, -1.11 to -0.38; P < 0.001). A greater effect size was seen with administration of NSAIDs before versus after IVI, as well as topical nepafenac relative to ketorolac or diclofenac.

DISCUSSION

At 6 hours after the procedure, NSAIDs provide a clinically meaningful reduction in pain relative to a control group. The administration of NSAIDs before the procedure, specifically topical nepafenac, was associated with the greatest improvement in pain relative to the control group.

EFFECT OF BROMFENAC ON PAIN RELATED TO INTRAVITREAL INJECTIONS: A Randomized Crossover Study

PURPOSE

To evaluate the analgesic effect of bromfenac, a topically administered nonsteroidal antiinflammatory agent, in patients undergoing intravitreal injections (IVIs) of anti-vascular endothelial growth factor agents.

METHODS

A single center, prospective, randomized, double-blind, placebo-controlled, cross over interventional study. Patients scheduled to undergo IVI of anti-vascular endothelial growth factor were randomized to receive topical bromfenac or placebo before IVI. Pain perception was assessed using the short form of the McGill Pain Questionnaire. Pain intensity was evaluated with the visual analog scale, the main component of the short form of the McGill Pain Questionnaire, and the Present Pain Intensity scores immediately and 6 hours postinjection.

RESULTS

Sixty-five patients (65 eyes) were enrolled in the study. Immediately after IVI, pain perception was statistically significant lower in patients treated with bromfenac compared with placebo as assessed by the visual analog scale pain score and the main component of the short form of the McGill Pain Questionnaire (P = 0.002 and 0.001, respectively). At 6 hours postIVI, pain was statistically significant lower in patients treated with bromfenac, according to the visual analog scale pain score, the main component of the short form of the McGill Pain Questionnaire, and the Present Pain Intensity score (P < 0.001, <0.001, and P = 0.001, respectively). Multivariable regression analysis revealed that pain perception, as evaluated with the visual analog scale pain score immediately after IVI, was significantly lower in patients of older age, female patients and those with higher number of previous injections. Immediately after IVI, bromfenac seemed to be more effective in younger patients and in those who had already undergone an amount of injections.

CONCLUSION

Topical instillation of bromfenac significantly reduced the IVI-related pain immediately after and 6 hours postinjection.