Recent advances of smart materials for ocular drug delivery

External stimuli-responsive drug delivery to the posterior segment of the eye

Posterior segment eye diseases represent the leading causes of vision impairment and blindness globally. Current therapies still have notable drawbacks, including the need for frequent invasive injections and the associated risks of severe ocular complications. Recently, the utility of external stimuli, such as light, ultrasound, magnetic field, and electric field, has been noted as a promising strategy to enhance drug delivery to the posterior segment of the eye. In this review, we briefly summarize the main physiological barriers against ocular drug delivery, focusing primarily on the recent advancements that utilize external stimuli to improve treatment outcomes for posterior segment eye diseases. The advantages of these external stimuli-responsive drug delivery strategies are discussed, with illustrative examples highlighting improved tissue penetration, enhanced control over drug release, and targeted drug delivery to ocular lesions through minimally invasive routes. Finally, we discuss the challenges and future perspectives in the translational research of external stimuli-responsive drug delivery platforms, aiming to bridge existing gaps toward clinical use.

Ophthalmic formulation of methotrexate: a strategy of using the self-assembled LacAC4A nanoparticles for non-invasive drug delivery to the ocular posterior segment

Drug delivery to ocular posterior segment remains difficult due to the challenges imposed by dynamic and static ocular barriers, lesion point targeting, and off-target effect. In this study, a novel approach is demonstrated for non-invasive drug delivery to the ocular posterior segments using lactose-modified azocalix[4] arene (LacAC4A) as a supramolecular ocular drug delivery platform. LacAC4A contains azo groups and is covalently modified by lactose groups, which confers active targeting to the retina, and induces a hypoxic response. The immunomodulator methotrexate (MTX), which is commonly used in ophthalmology to treat immune system diseases such as uveitis, was also selected as a guest to prepare MTX@LacAC4A. The prepared LacAC4A and MTX@LacAC4A systems were characterized, then the internalization mechanisms and hypoxia response abilities were determined through flow cytometry and fluorescence imaging, respectively. Besides, the delivery route and efficiency were verified, and the safety profile of MTX@LacAC4A was evaluated in multiple dimensions. Importantly, it was found that the prepared MTX@LacAC4A exhibits good biocompatibility, can effectively reach the posterior segment, and demonstrates potential ophthalmic applications. These findings lay the grounds for the future development of non-invasive ocular posterior segment disease treatments based on the advanced use of LacAC4A as a drug delivery platform.

An overview of novel formulations for ocular viral infections: focused on nanomedicines

Ocular viral infections are a common cause of blindness globally. Many ocular viral infections are mistakenly identified as bacterial infections. In these situations, treatment is initiated belatedly and fails to address the root cause of the infection, which frequently results in serious ocular complications like corneal infiltrates, conjunctival scarring, and decreased visual acuity. The efficacy of conventional treatments for viral infections suffers from poor bioavailability, which requires the development of novel methods of drug delivery, accurate diagnosis, and efficient treatment choices. As nanotechnology in medicine advances at a rapid pace, multifunctional nanosystems are being prioritized more and more to address the problems brought on by viral infections of the eyes offering targeted delivery, increased bioavailability and decreased systemic toxicity. This study delivers a thorough overview of the use of nanomedicines in the treatment of ocular viral infections, with a particular emphasis on how they may enhance the safety and efficacy of antiviral drugs. We address a range of nanocarrier systems, such as liposomes, nanoparticles, nanosuspension, proniosomes, in-situ gels, dendrimers, and nanogels, emphasizing their distinct characteristics that facilitate the effective transportation of antiviral drugs to ocular tissues. This article also highlighted the regulatory barriers of ocular nanoformulation. The transition of in-vitro studies to in-vivo and clinical models has been discussed. This review also highlights the Preclinical studies of ocular viral treatment, ocular nanotoxicology and advancement of ocular antiviral treatments in the form of patents, ongoing clinical trials and marketed formulations.

Recent progress in ZIF-polymer composites for advanced drug delivery applications

This review article provides an in-depth study of recent advancements in ZIF-polymer composites, focusing on their transformative potential in drug delivery systems. It also reveals their multiple advantages, including increased drug loading efficiency, controlled and sustained release, and targeted delivery capabilities. In addition, this article explores various applications of ZIFs in diverse therapeutic areas such as orthopedic, ocular, transdermal, gastrointestinal, and pulmonary drug delivery. This review also offers key insights into the synthesis approaches, current scenario, and future directions of ZIF-polymer composites, along with some aspects of critical factors such as stimuli-responsiveness, stability, and toxicity. Zeolitic imidazolate frameworks (ZIFs), a new subclass of MOFs, are synthesized from tetrahedral metal ions and imidazolate linkers. ZIFs are valued for their exceptional porosity, robust chemical stability, and thermal characteristics. They show excellent compatibility with polymers and fabrication of ZIF-polymer hybrids with high loading efficiency is achieved using methods such as in situ synthesis, self-assembly, grafting, electrospinning, and microfluidic synthesis techniques. By consolidating knowledge of the role of ZIF-polymer hybrids in drug delivery, this article provides a valued resource for researchers and scientists seeking to revolutionize patient care through cutting-edge materials. It also emphasizes the potential of ZIF-polymer composites to redefine drug delivery systems and improve clinical outcomes, marking a significant milestone in the quest for ideal drug delivery platforms. In summary, this review emphasizes the importance of innovative ZIF-polymer materials as promising alternatives to conventional therapeutic systems, contributing to the development of advanced healthcare solutions.

Application of Nanomaterials in the Diagnosis and Treatment of Retinal Diseases

In recent years, nanomaterials have demonstrated broad prospects in the diagnosis and treatment of retinal diseases due to their unique physicochemical properties, such as small-size effects, high biocompatibility, and functional surfaces. Retinal diseases are often accompanied by complex pathological microenvironments, where conventional diagnostic and therapeutic approaches face challenges such as low drug delivery efficiency, risks associated with invasive procedures, and difficulties in real-time monitoring. Nanomaterials hold promise in addressing these limitations of traditional therapies, thereby improving treatment precision and efficacy. The applications of nanomaterials in diagnostics are summarized, where they enable high-resolution retinal imaging by carrying fluorescent probes or contrast agents or act as biosensors to sensitively detect disease-related biomarkers, facilitating early diagnosis and dynamic monitoring. In therapeutics, functionalized nanocarriers can precisely deliver drugs, genes, or antioxidant molecules to retinal target cells, significantly enhancing therapeutic outcomes while reducing systemic toxicity. Additionally, nanofiber materials possess unique properties that make them particularly suitable for retinal regeneration in tissue engineering. By loading neurotrophic factors into nanofiber scaffolds, their regenerative effects can be amplified, promoting the repair of retinal neurons. Despite their immense potential, clinical translation of nanomaterials still requires addressing challenges such as long-term biosafety, scalable manufacturing processes, and optimization of targeting efficiency.

Functionalized amino acid-based injectable hydrogels for sustained drug delivery

Drug delivery vehicles optimize therapeutic outcomes by enhancing drug efficacy, minimizing side effects, and providing controlled release. Injectable hydrogels supersede conventional ones in the field of drug delivery owing to their less invasive administration and improved targeting. However, they face challenges such as low biodegradability and biocompatibility, potentially compromising their effectiveness. To address these limitations, a modified amino acid-based pH-responsive injectable shear-thinning hydrogel cl-β-CD-g-p(Gly-MA) has been developed as an efficient drug carrier. In the two-step synthetic approaches, first, the well-known amino acid glycine (Gly) is modified to form glycine methacrylate (Gly-MA). Afterward, Gly-MA is chemically crosslinked with β-cyclodextrin (β-CD), an oligosaccharide, using an ethylene glycol dimethacrylate (EGDMA) crosslinker. The presence of these biomaterials as building blocks enhances the biocompatibility, hemocompatibility, and biodegradability of the hydrogel. They also reduce the risk of immunogenicity. The unique property of easy injectability enables minimally invasive administration. This feature also helps prolong drug retention at the target site, further optimizing drug delivery efficiency. Moreover, the pH-responsive feature of the developed cl-β-CD-g-p(Gly-MA) hydrogel ensures controlled drug release in response to the physiological conditions of the target site, enhancing therapeutic efficacy. The study focuses on investigating the in vitro loading and release of diclofenac sodium (DS), a non-steroidal anti-inflammatory drug (NSAID) commonly used to treat arthritic pain and inflammation.

Nanotechnology-based non-invasive strategies in ocular therapeutics: Approaches, limitations to clinical translation, and safety concerns

The eye is a highly sensitive and vital component that significantly affects human quality of life. Diseases that affect the eye are major contributors to visual impairment and blindness and can have a profound effect on an individual's well-being. Ocular drug delivery is challenging because of physiological and anatomical barriers. Invasive Intravitreal administration is primarily used for the treatment and management of posterior segmental disease. However, frequent intravitreal administration is associated with adverse effects. Furthermore, topical administration results in less than 5% ocular bioavailability, leading to a void in the safe and efficacious management of posterior segment diseases. Nanocarrier-based systems have been well explored as ocular therapeutics to overcome the sub-therapeutic management attributed to conventional eye drops and physiological and anatomical barriers. Since the first report of nanoparticles to date, the nanocarrier system has come a long way with the simplicity and versatility offered by the system. Significant progress has been made in the development of noninvasive nanocarrier systems and their interactions with the ocular surface. The nanocarrier system enhances precorneal retention, limits nontherapeutic absorption, and offers controlled drug release. This review aims to provide an overview of the recent advancements in noninvasive nanocarrier-based topical ocular drug delivery systems, including their interaction with the ocular surface, the barriers to their translation to clinical settings, and the associated scale-up challenges.

Bringing ophthalmology into the scientific world: Novel nanoparticle-based strategies for ocular drug delivery

The distinctive benefits and drawbacks of various drug delivery strategies to supply corneal tissue improvement for sense organs have been the attention of studies worldwide in recent decades. Static and dynamic barriers of ocular tissue prevent foreign chemicals from entering and inhibit the active absorption of therapeutic medicines. The distribution of different medications to ocular tissue is one of the most appealing and demanding tasks for investigators in pharmacology, biomaterials, and ophthalmology, and it is critical for cornea wound healing due to the controlled release rate and increased drug bioavailability. It should be mentioned that the transport of various types of medications into the different sections of the eye, particularly the cornea, is exceedingly challenging because of its distinctive structure and various barriers throughout the eye. Nanoparticles are being studied to improve medicine delivery strategies for ocular disease. Repetitive corneal drug delivery using biodegradable nanocarriers allows a medicine to remain in different parts of the cornea for extended periods of time and thus improve administration route effectiveness. In this review, we discussed eye anatomy, ocular delivery barriers, as well as the emphasis on the biodegradable nanomaterials ranging from organic nanostructures, such as nanomicelles, polymers, liposomes, niosomes, nanowafers, nanoemulsions, nanosuspensions, nanocrystals, cubosomes, olaminosomes, hybridized NPs, dendrimers, bilosomes, solid lipid NPs, nanostructured lipid carriers, and nanofiber to organic nanomaterials like silver, gold, and mesoporous silica nanoparticles. In addition, we describe the nanotechnology-based ophthalmic medications that are presently on the market or in clinical studies. Finally, drawing on current trends and therapeutic approaches, we discuss the challenges that innovative optical drug delivery systems confront and propose future research routes. We hope that this review will serve as a source of motivation and inspiration for developing innovative ophthalmic formulations.

Multifunctional Stimuli-Responsive Polyaniline-Based Conductive Composite Film

There is a growing demand for multifunctional materials that can meet the increasingly complex needs of modern society. The combination of functionalization and intellectualization promotes the development of multifunctional smart materials. These materials are not only required to possess excellent basic properties, but also need to integrate multiple functions to adapt to various application scenarios. In this study, a simple solution co-blending method for preparing a polyaniline-based multifunctional conductive composite film was proposed. This methodology employs polyvinyl alcohol (PVA) as a stimuli-responsive matrix, combined with polyaniline (PANI) serving as a functional component, while glutaraldehyde (GA) acts as the crosslinking agent. This PANI-based composite film overcomes the disadvantage that PANI does not easily form a uniform film. The maximum conductivity of this film can reach 0.034 S·cm-1. It is worth noting that the combination of PANI with the stimuli-responsive PVA film resulted in a composite film that not only retained good electrical conductivity, but also exhibited multiple stimuli-responsive properties. These stimuli-responsive properties can be controlled by external stimuli such as heat, voltage, light, or water. The PANI-based composite film could recover its original shape within 25 s when the applied voltage reached 30 V. These characteristics open up possibilities of potential applications where controlled deformation is desired.

Hybrid Biomembrane-Functionalized Nanorobots Penetrate the Vitreous Body of the Eye for the Treatment of Retinal Vein Occlusion

Intravitreal injections of antivascular endothelial growth factor (VEGF) agents are the primary method for treating retinal vein occlusion (RVO). However, the complex structure of eye anatomy presents ocular barriers that impede drug delivery. Additionally, these drugs only manage the complications associated with RVO and fail to address the underlying cause of vessel occlusions. Here, we describe a method that utilizes functionalized magnetically driven nanorobots to overcome ocular barriers and treat RVO. These nanorobots are developed using a hybrid biomembrane that combines stem cell membranes with liposome-derived membranes, enveloping perfluorohexane, iron oxide nanoparticles, and l-arginine. After intravitreal injection, the nanorobots can move directionally through and penetrate the vitreous body to reach the retina, driven by an external magnetic field. Subsequently, the nanorobots actively target the inflammation sites at occluded vessels due to the presence of stem cell membranes. In a rat model of RVO, enhanced targeting and accumulation in ischemic retinal vessels were demonstrated following intravitreal injections. Furthermore, the application of ultrasound triggers the release of l-arginine at the site of occlusion, stimulating the production of nitric oxide, which promotes vasodilation and restores blood flow, thereby achieving excellent therapeutic efficacy for RVO. We believe these methods hold significant promise for overcoming challenges in ocular drug delivery and effectively treating RVO in clinical applications.

Zwitterionic Hydrogels: From Synthetic Design to Biomedical Applications

Zwitterionic hydrogels have emerged as a highly promising class of biomaterials, attracting considerable attention due to their unique properties and diverse biomedical applications. Zwitterionic moieties, with their balanced positive and negative charges, endow hydrogels with exceptional hydration, resistance to nonspecific protein adsorption, and low immunogenicity due to their distinctive molecular structure. These properties facilitate various biomedical applications, such as medical device coatings, tissue engineering, drug delivery, and biosensing. This review explores the structure-property relationships in zwitterionic hydrogels, highlighting recent advances in their design principles, synthesis methods, structural characteristics, and biomedical applications. To meet the evolving and growing demand for the biomedical field, this review examines current challenges and explores future research directions for optimizing the multifunctional properties of zwitterionic hydrogels. As promising candidates for advanced biomaterials, zwitterionic hydrogels are poised to address critical challenges in biomedical applications, paving the way for improved therapeutic outcomes and broader applicability in healthcare.

Light-Activated Anti-Vascular Combination Therapy against Choroidal Neovascularization

Choroidal neovascularization (CNV) underlies the crux of many angiogenic eye disorders. Although medications that target vascular endothelial growth factor (VEGF) are approved for treating CNV, their effectiveness in destroying new blood vessels is limited, and invasive intravitreal administration is required. Additionally, other drugs that destroy established neovessels, such as combretastatin A-4, may have systemic side effects that limit their therapeutic benefits. To overcome these shortcomings, a two-pronged anti-vascular approach is presented for CNV treatment using a photoactivatable nanoparticle system that can release a VEGF receptor inhibitor and a vascular disrupting agent when irradiated with 690 nm light. The nanoparticles can be injected intravenously to enable anti-angiogenic and vascular disrupting combination therapy for CNV through light irradiation to the eyes. This approach can potentiate therapeutic effects while maintaining a favorable biosafety profile for choroidal vascular diseases.

Anti-oxidative mesoporous polydopamine-based hypotensive nano-eyedrop for improved glaucoma management

Conventional hypotensive eye drops remain suboptimal for glaucoma management, primarily due to their limited intraocular bioavailability and the growing concern regarding ocular surface side effects. Therefore, there is an urgent need to develop innovative intraocular pressure (IOP)-lowering formulations that not only possess enhanced corneal penetration ability but also provide ocular surface protection. Herein, anti-oxidative mesoporous polydopamine nanoparticles (MPDA NPs) were explored as a nano-carrier for Brimonidine to address the above issues. Nearly monodisperse MPDA NPs with obvious nanopores were successfully prepared by template-removal method and used for encapsulation of Brimonidine benefiting from their high specific surface area. Interestingly, the PEGylated and drug loaded MPDA-PEG@Brim NPs showed a near neutral surface charge, which is expected to enhance intraocular drug delivery. Consequently, much higher concentration of Brimonidine in the aqueous humor was found after topical administration of MPDA-PEG@Brim nano-dispersion as compared to free Brimonidine solution. Accordingly, superior IOP reduction effect was achieved for the nano-formulation in both hypertensive and normotensive rat eyes. Moreover, MPDA-PEG NPs showed good capability in scavenging diverse free radicals, alleviating intracellular oxidative stress, and mitigating ocular surface oxidative level in a mouse model of preservative-induced dry eye. In addition, the excellent biosafety of this novel Brimonidine nanodrug was confirmed both in vitro and in vivo. Therefore, the present work may shed light on the development of next generation hypotensive formulations for extended ocular surface protection and glaucoma management.

Recent Advances in Nanomedicine for Ocular Fundus Neovascularization Disease Management

As an indispensable part of the human sensory system, visual acuity may be impaired and even develop into irreversible blindness due to various ocular pathologies. Among ocular diseases, fundus neovascularization diseases (FNDs) are prominent etiologies of visual impairment worldwide. Intravitreal injection of anti-vascular endothelial growth factor drugs remains the primary therapy but is hurdled by common complications and incomplete potency. To renovate the current therapeutic modalities, nanomedicine emerged as the times required, which is endowed with advanced capabilities, able to fulfill the effective ocular fundus drug delivery and achieve precise drug release control, thus further improving the therapeutic effect. This review provides a comprehensive summary of advances in nanomedicine for FND management from state-of-the-art studies. First, the current therapeutic modalities for FNDs are thoroughly introduced, focusing on the key challenges of ocular fundus drug delivery. Second, nanocarriers are comprehensively reviewed for ocular posterior drug delivery based on the nanostructures: polymer-based nanocarriers, lipid-based nanocarriers, and inorganic nanoparticles. Thirdly, the characteristics of the fundus microenvironment, their pathological changes during FNDs, and corresponding strategies for constructing smart nanocarriers are elaborated. Furthermore, the challenges and prospects of nanomedicine for FND management are thoroughly discussed.

Nanostructure-Mediated Transport of Therapeutics through Epithelial Barriers

The ability to precisely treat human disease is facilitated by the sophisticated design of pharmacologic agents. Nanotechnology has emerged as a valuable approach to creating vehicles that can specifically target organ systems, effectively traverse epithelial barriers, and protect agents from premature degradation. In this review, we discuss the molecular basis for epithelial barrier function, focusing on tight junctions, and describe different pathways that drugs can use to cross barrier-forming tissue, including the paracellular route and transcytosis. Unique features of drug delivery applied to different organ systems are addressed: transdermal, ocular, pulmonary, and oral delivery. We also discuss how design elements of different nanoscale systems, such as composition and nanostructured architecture, can be used to specifically enhance transepithelial delivery. The ability to tailor nanoscale drug delivery vehicles to leverage epithelial barrier biology is an emerging theme in the pursuit of facilitating the efficacious delivery of pharmacologic agents.

Research progress of photo-crosslink hydrogels in ophthalmology: A comprehensive review focus on the applications

Hydrogel presents a three-dimensional polymer network with high water content. Over the past decade, hydrogel has developed from static material to intelligent material with controllable response. Various stimuli are involved in the formation of hydrogel network, among which photo-stimulation has attracted wide attention due to the advantages of controllable conditions, which has a good application prospect in the treatment of ophthalmic diseases. This paper reviews the application of photo-crosslink hydrogels in ophthalmology, focusing on the types of photo-crosslink hydrogels and their applications in ophthalmology, including drug delivery, tissue engineering and 3D printing. In addition, the limitations and future prospects of photo-crosslink hydrogels are also provided.

Smart Contact Lenses for Healthcare Monitoring and Therapy

The eye contains a wealth of physiological information and offers a suitable environment for noninvasive monitoring of diseases via smart contact lens sensors. Although extensive research efforts recently have been undertaken to develop smart contact lens sensors, they are still in an early stage of being utilized as an intelligent wearable sensing platform for monitoring various biophysical/chemical conditions. In this review, we provide a general introduction to smart contact lenses that have been developed for disease monitoring and therapy. First, different disease biomarkers available from the ocular environment are summarized, including both physical and chemical biomarkers, followed by the commonly used materials, manufacturing processes, and characteristics of contact lenses. Smart contact lenses for eye-drug delivery with advancing technologies to achieve more efficient treatments are then introduced as well as the latest developments for disease diagnosis. Finally, sensor communication technologies and smart contact lenses for antimicrobial and other emerging bioapplications are also discussed as well as the challenges and prospects of the future development of smart contact lenses.

Antioxidant nanoemulsion loaded with latanoprost enables highly effective glaucoma treatment

Glaucoma is the third leading cause of blindness worldwide and is primarily characterized by elevated intraocular pressure (IOP). Common risk factors such as age, myopia, ocular trauma, and hypertension all increase the risk of elevated IOP. Prolonged high IOP not only causes physiological discomfort like headaches, but also directly damages retinal cells and leads to retinal ischemia, oxidative imbalance, and accumulation of reactive oxygen species (ROS) in the retina. This oxidative stress causes the oxidation of proteins and unsaturated lipids, leading to peroxide formation and exacerbating retinal damage. While current clinical treatments primarily target reducing IOP through medication or surgery, there are currently no effective methods to mitigate the retinal cell damage associated with glaucoma. To address this gap, we developed a novel nanoemulsion to co-delivery latanoprost and α-tocopherol (referred to as LA@VNE later) that prolongs ocular retention and enhances retinal permeability through localized administration. By encapsulating latanoprost, an IOP-lowering drug, and α-tocopherol, a potent antioxidant, we effectively reduced ROS accumulation (>1.5-fold in vitro and 2.5-fold in vivo), retinal ganglion cell (RGC) apoptosis (>9 fold), and inflammatory cell infiltration (>1.6 fold). Our approach showed strong biocompatibility and significant potential for clinical translation, providing a promising platform for the treatment of glaucoma.