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

Carboxymethyl Chitosan and Chitosan as a Bioactive Delivery System: A Review

The functionality and mechanism of bioactive agents (BA) in treating various diseases have been studied as a progressive route. Designing an effective delivery system for transferring these molecules and components is a major challenge. For that reason, a wide range of biomaterials has been introduced to deliver BA to the target tissue or cells. Chitosan (CTS) is a nontoxic, biocompatible, biodegradable, and notable point low-cost polymer, and, as a result, can be effectively utilized in the formulation of diverse delivery systems, in biomedical applications. However, CTS has some limitations, such as poor solubility in aqueous and alkaline media, rapid swelling and degradation, and consequence fast release agent. The CTS derivative carboxymethyl chitosan (CMC) is an acceptable candidate for overcoming these limitations. CMC is a high-impact grade for pharmaceutical and biomedical applications because of its nontoxic, biocompatible, biodegradable, gelation, mucoadhesive, antibacterial, and antifungal. CMC bioactivity potentials are related to carboxyl and methyl groups added through chemical modification in the CTS backbone. In this review, the physical and chemical properties of CTS and CMC have been introduced and discussed. Afterward, its biomedical applications with delivery approaches for various BA (drugs, genes, proteins), microfluidic, and cancer have been considered.

N-acetylcysteine and chitosan conjugate modified dexamethasone nanostructured lipid carriers: Enhanced permeability, precorneal retention and lower inflammation for the treatment of dry eye syndrome

Dexamethasone (Dex) is a primary medication for treating dry eye syndrome, and tobramycin-dexamethasone eye drops are commercially available. However, the eye's complex physiological environment reduces its bioavailability, and repeated use can lead to significant systemic toxicity and side effects. This study introduces a novel conjugate of chitosan (CS) and N-acetylcysteine (NAC), a bioadhesive material, which was grafted onto the surface of a Dex-supported nanostructured lipid carrier (NLC) to develop an innovative nanoparticle lipid ocular drug delivery system (CS-NAC@Dex-NLC). The enhancements afforded by CS-NAC, such as adhesion, osmotic, and targeting properties, address the limitations of traditional eye drops. NMR characterization confirmed the successful synthesis of the copolymer (CS-NAC). Particle size (PS), zeta potential, and transmission electron microscopy (TEM) verified the proper formation of the CS-NAC@Dex-NLC system. Cytotoxicity tests confirmed its excellent biocompatibility and safety. Cellular uptake studies showed that CS-NAC@Dex-NLC achieved the highest efficiency. Pharmacokinetic assessments revealed a significant increase in Dex's bioavailability in tears and aqueous humor. In vitro corneal penetration and in vivo imaging experiments demonstrated effective corneal penetration and retention, enhancing the drug's duration on the ocular surface and overcoming the barrier effect. Pharmacodynamic studies in rabbits with dry eye syndrome indicated that CS-NAC@Dex-NLC effectively alleviates symptoms, repairs corneal damage, and stabilizes the tear film. ELISA results showed a reduction in inflammation caused by dry eye. These findings suggest that CS-NAC@Dex-NLC is a promising vector for dry eye treatment, offering significant clinical relevance.

Emerging trends in designing polysaccharide based mucoadhesive network hydrogels as versatile platforms for innovative delivery of therapeutic agents: A review

INTRODUCTION

The rapid progress in polymer science has designed innovative materials for biomedical applications. In the case of drug design, for each new therapeutic agent, a drug delivery system (DDS) is required to improve its pharmacokinetic and pharmacodynamic parameters. Therefore, significant research has been carried out to develop drug delivery (DD) carriers for these new therapeutic agents. Hydrogels have been explored as potential candidates to prepare controlled drug delivery (CDD) systems to address the challenges related to the performance of the conventional DD formulations. Mucoadhesive drug delivery system (MUCO-DDS) is a specialized form of CDD system, facilitating site-specific DD, protecting the drug from first pass metabolism and enhancing its overall bioavailability.

METHODS

The present article provides a comprehensive discussion of the synthesis, properties and applications of polysaccharide-derived MUCO-DDS. Different natural polymer-derived MUCO-DDS including chitosan, alginate, pectin, xanthan gum, psyllium, gelatin, cellulose, hyaluronic acid, guar gum, sterculia gum and tragacanth gum have been reported. Herein, these DDS were elaborately discussed along with their applications and future-prospective. These DDS are classified on the basis of drug administration (nasal, ocular, vagina/rectal & buccal DDS) and drug distribution (reservoir and monolithic polymer matrix). Factors contributing to modifications of properties of MUCO-DDS were also demonstrated along with different stages and theories of mucoadhesion.

RESULTS

Polysaccharides exhibit properties such as biocompatibility, biodegradability, and flexibility, making them ideal for CDD applications. MUCO-DDS demonstrates several significant advantages. Moreover, the article bridges theoretical insights with practical applications and future research prospects, ensuring its relevance for advancements in the concerned field. This review serves as a comprehensive resource, addressing gaps in previous literature and paving the way for innovations in MUCO-DDS, through a comparative analysis of the advantages, limitations, and modifications of natural polymers.

CONCLUSIONS

In conclusion, this review gives an overview of the current developments in the field of mucoadhesive DD systems and also gives insights into the future perspectives. The MUCOAD of DDS could be modulated by the inclusion of various natural and synthetic components in hydrogels. Future directions for the researchers are underway to integrate nanotechnology with mucoadhesive systems to create hybrid platforms. Overall, by addressing current limitations and leveraging emerging technologies, these systems can revolutionize drug delivery for a wide range of therapeutic applications.

Advances in the Study of Age-Related Macular Degeneration Based on Cell or Cell-Biomaterial Scaffolds

Age-related macular degeneration (AMD), a progressive neurodegenerative disorder affecting the central retina, is pathologically defined by the irreversible degeneration of photoreceptors and retinal pigment epithelium (RPE), coupled with extracellular drusen deposition and choroidal neovascularization (CNV), and AMD constitutes the predominant etiological factor for irreversible vision impairment in adults aged ≥60 years. Cell-based or cell-biomaterial scaffold-based approaches have been popular in recent years as a major research direction for AMD; monotherapy with cell-based approaches typically involves subretinal injection of progenitor-derived or stem cell-derived RPE cells to restore retinal homeostasis. Meanwhile, cell-biomaterial scaffolds delivered to the lesion site by vector transplantation have been widely developed, and the implanted cell-biomaterial scaffolds can promote the reintegration of cells at the lesion site and solve the problems of translocation and discrete cellular structure produced by cell injection. While these therapeutic strategies demonstrate preliminary efficacy, rigorous preclinical validation and clinical trials remain imperative to validate their long-term safety, functional durability, and therapeutic consistency. This review synthesizes current advancements and translational challenges in cell-based and cell-biomaterial scaffold approaches for AMD, aiming to inform future development of targeted interventions for AMD pathogenesis and management.

The role of metal nanocarriers, liposomes and chitosan-based nanoparticles in diabetic retinopathy treatment: A review study

Diabetic Retinopathy (DR) is a significant and progressive eye complication associated with diabetes mellitus, leading to potential vision loss. The pathophysiology of DR involves complex neurovascular changes due to prolonged hyperglycemia, resulting in microangiopathy and neurodegeneration. Current treatment modalities come with limitations such as low bioavailability of therapeutic agents, risk of side effects, and surgical complications. Consequently, the prevention and management of DR, particularly in its advanced stages, present ongoing challenges. This review investigates recent advancements in nanotechnology as a novel approach to enhance the treatment of DR. A comprehensive literature review of recent studies focusing on nanocarriers for drug delivery in DR treatment and an analysis of their efficacy compared to traditional methods was conducted for this study. The findings indicate that nanotechnology can significantly enhance the bioavailability of therapeutic agents while minimizing systemic exposure and associated side effects. The novelty of this study lies in its focus on the intersection of nanotechnology and ophthalmology, exploring innovative solutions that extend beyond existing literature on DR treatments. By highlighting recent advancements in this field, the study paves the way for future research aimed at developing more effective therapeutic strategies for managing DR.

Chondroitin Sulphate-Chitosan Based Nanogels Loaded with Naringenin-β-Cyclodextrin Complex as Potential Tool for the Treatment of Diabetic Retinopathy: A Formulation Study

Purpose

The main purpose of the study was the formulation development of nanogels (NHs) composed of chondroitin sulfate (CS) and low molecular weight chitosan (lCH), loaded with a naringenin-β-cyclodextrin complex (NAR/β-CD), as a potential treatment for early-stage diabetic retinopathy.

Methods

Different formulations of NHs were prepared by varying polymer concentration, lCH ratio, and pH and, then, characterized for particle size, zeta potential, particle concentration (particles/mL) and morphology. Cytotoxicity and internalization were assessed in vitro using Human Umbilical Vein Endothelial Cells (HUVEC). The NAR/β-CD complex was prepared and evaluated for morphology, complexation efficiency, and solubility. Finally, the most promising NH prototype was loaded with NAR/β-CD (NH@NAR/β-CD) and further characterized for encapsulation efficiency, loading capacity, opacity and cytotoxicity on HUVEC; in vitro release test and DPPH assay were performed to investigate NH capability to sustain NAR release and NH@NAR/β-CD antioxidant properties, respectively.

Results

NH properties were influenced by polymer concentration, lCH ratio, and pH. N3 (0.5 mg/mL; lCH=1.5:1; pH = 5) and N9 (0.5 mg/mL; lCH=1:1; pH = 5) showed optimal characteristics, including small size (<350 nm) and positive zeta potential, facilitating cellular uptake. The NAR/β-CD complex showed 71% complexation efficiency and enhanced NAR solubility. Since characterized by superior properties and better in vitro biocompatibility, N3 was loaded with NAR/β-CD. N3@NAR/β-CD capability to sustain in vitro NAR release, radical scavenging activity and in vitro biocompatibility were finally demonstrated.

Conclusion

The physico-chemical properties of N3@NAR/β-CD were responsible for their cell uptake, suggesting their potential to target retinal endothelial cells. The high NAR/β-CD complexation efficiency and the sustained NAR release over 72 hours could guarantee the maintenance of an effective drug concentration at the damage site while reducing the injection number. Further studies about the safety and the effectiveness of the intravitreal injection of NHs@NAR/β-CD will be performed on a diabetic animal model.

From Preformulative Design to In Vivo Tests: A Complex Path of Requisites and Studies for Nanoparticle Ocular Application. Part 1: Design, Characterization, and Preliminary In Vitro Studies

Ocular pathologies are widely diffused worldwide, and their effective treatment, combined with a high patient compliance, is sometimes challenging to achieve due to the barriers of the eye; in this context, the use of nanoparticles for topical ophthalmic application could represent a successful strategy. Aiming to develop nanoplatforms with potential clinical applications, great attention has to be paid to their features, in relation to the route of administration and to the pharmacopoeial requirements. This review (part 1) thus embraces the preliminary steps of nanoparticle development and characterization. At the beginning, the main barriers of the eye and the different administration routes are resumed, followed by a general description of the advantages of the employment of nanoparticles for ocular topical administration. Subsequently, the preformulative steps are discussed, deepening the choice of raw materials and determining the quantitative composition. Then, a detailed report of the physicochemical and technological characterization of nanoparticles is presented, analyzing the most relevant tests that should be performed on nanoparticles to verify their properties and the requisites (both mandatory and suggested) demanded by regulatory agencies. In conclusion, some preliminary noncellular in vitro evaluation methods are described. Studies from in vitro cellular assays to in vivo tests will be discussed in a separate (part 2) review paper. Hence, this overview aims to offer a comprehensive tool to guide researchers in the choice of the most relevant studies to develop a nanoplatform for ophthalmic drug administration.

Recent developments in the biomedical and anticancer applications of chitosan derivatives

Chitosan is a natural polymer derived from chitin. It has significant applications in various fields due to its unique physicochemical properties, biocompatibility, and biodegradability. These important properties of chitosan make it an attractive candidate for various anti-cancer activities and biomedical applications, including tissue engineering. This review emphasizes the latest literature on anticancer applications of chitosan derivatives and in-depth study of biomedical applications. This review highlights the importance of biomedical applications and anti-cancer activities like breast, liver, colon, gastric, melanoma, colorectal, cervical, oral, and lymphoma cancer. Currently, there is a notable absence of recent reviews that comprehensively address these aspects such as Alejandro Elizalde-Cárdenas, et al. 2024, focuses only on Biomedical applications of Cs and its derivatives (Elizalde-Cárdenas et al., 2024). Jingxian Ding, et al. 2022 discussed the applications of Cs in some Cancer treatments (Mabrouk et al., 2024). However, our article aims to provide a comprehensive overview of the latest advancements in Cs derivatives in both fields. This manuscript is designed with proper diagrams, flow sheets and summarized tables to enhance the understanding of the reader. It also highlights recent advancements in the development of various chitosan derivatives, offering a comprehensive perspective for researchers and practitioners to further progress in biomedical and anticancer technologies.

Polymers and their engineered analogues for ocular drug delivery: Enhancing therapeutic precision

Ocular drug delivery is constrained by anatomical and physiological barriers, necessitating innovative solutions for effective therapy. Natural polymers like hyaluronic acid, chitosan, and gelatin, alongside synthetic counterparts such as PLGA and PEG, have gained prominence for their biocompatibility and controlled release profiles. Recent strides in polymer conjugation strategies have enabled targeted delivery through ligand integration, facilitating tissue specificity and cellular uptake. This versatility accommodates combined drug delivery, addressing diverse anterior (e.g., glaucoma, dry eye) and posterior segment (e.g., macular degeneration, diabetic retinopathy) afflictions. The review encompasses an in-depth exploration of each natural and synthetic polymer, detailing their individual advantages and disadvantages for ocular drug delivery. By transcending ocular barriers and refining therapeutic precision, these innovations promise to reshape the management of anterior and posterior segment eye diseases.

A review on revolutionizing ophthalmic therapy: Unveiling the potential of chitosan, hyaluronic acid, cellulose, cyclodextrin, and poloxamer in eye disease treatments

Ocular disorders, encompassing both common ailments like dry eye syndrome and more severe situations for instance age-related macular degeneration, present significant challenges to effective treatment due to the intricate architecture and physiological barriers of the eye. Polysaccharides are emerging as potential solutions for drug delivery to the eyes due to their compatibility with living organisms, natural biodegradability, and adhesive properties. In this review, we explore not only the recent advancements in polysaccharide-based technologies and their transformative potential in treating ocular illnesses, offering renewed optimism for both patients and professionals but also anatomy of the eye and the significant obstacles hindering drug transportation, followed by an investigation into various drug administration methods and their ability to overcome ocular-specific challenges. Our focus lies on biological adhesive polymers, including chitosan, hyaluronic acid, cellulose, cyclodextrin, and poloxamer, known for their adhesive characteristics enhancing drug retention on ocular surfaces and increasing bioavailability. A detailed analysis of material designs used in ophthalmic formulations, such as gels, lenses, eye drops, nanofibers, microneedles, microspheres, and nanoparticles, their advantages and limitations, the potential of formulations in improving therapeutic outcomes for various eye conditions. Moreover, we underscore the discovery of novel polysaccharides and their potential uses in ocular drug delivery.

Biopolymeric Innovations in Ophthalmic Surgery: Enhancing Devices and Drug Delivery Systems

The interface between material science and ophthalmic medicine is witnessing significant advances with the introduction of biopolymers in medical device fabrication. This review discusses the impact of biopolymers on the development of ophthalmic devices, such as intraocular lenses, stents, and various prosthetics. Biopolymers are emerging as superior alternatives due to their biocompatibility, mechanical robustness, and biodegradability, presenting an advance over traditional materials with respect to patient comfort and environmental considerations. We explore the spectrum of biopolymers used in ophthalmic devices and evaluate their physical properties, compatibility with biological tissues, and clinical performances. Specific applications in oculoplastic and orbital surgeries, hydrogel applications in ocular therapeutics, and polymeric drug delivery systems for a range of ophthalmic conditions were reviewed. We also anticipate future directions and identify challenges in the field, advocating for a collaborative approach between material science and ophthalmic practice to foster innovative, patient-focused treatments. This synthesis aims to reinforce the potential of biopolymers to improve ophthalmic device technology and enhance clinical outcomes.

Chitosan as a promising materials for the construction of nanocarriers for diabetic retinopathy: an updated review

Diabetic retinopathy (DR) is a condition that causes swelling of the blood vessels of the retina and leaks blood and fluids. It is the most severe form of diabetic eye disease. It causes vision loss in its advanced stage. Diabetic retinopathy is responsible for causing 26% of blindness. Very insufficient therapies are accessible for the treatment of DR. As compared to the conventional therapies, there should be enhanced research on the controlled release, shorter duration, and cost-effective therapy of diabetic retinopathy. The expansion of advanced nanocarriers-based drug delivery systems has been now employed to exploit as well as regulate the transport of many therapeutic agents to target sites via the increase in penetration or the extension of the duration of contact employing production by enclosing as well as distributing tiny molecules in nanostructured formulation. Various polymers have been utilized for the manufacturing of these nanostructured formulations. Chitosan possesses incredible biological and chemical properties, that have led to its extensive use in pharmaceutical and biomedical applications. Chitosan has been used in many studies because of its enhanced mucoadhesiveness and non-toxicity. Multiple studies have used chitosan as the best candidate for manufacturing nanocarriers and treating diabetic retinopathy. Numerous nanocarriers have been formulated by using chitosan such as nanostructured lipid carriers, solid lipid nanoparticles, liposomes, and dendrimers for treating diabetic retinopathy. This current review elaborates on the recent advancements of chitosan as a promising approach for the manufacturing of nanocarriers that can be used for treating diabetic retinopathy.

Overview of processed excipients in ocular drug delivery: Opportunities so far and bottlenecks

Ocular drug delivery presents a unique set of challenges owing to the complex anatomy and physiology of the eye. Processed excipients have emerged as crucial components in overcoming these challenges and improving the efficacy and safety of ocular drug delivery systems. This comprehensive overview examines the opportunities that processed excipients offer in enhancing drug delivery to the eye. By analyzing the current landscape, this review highlights the successful applications of processed excipients, such as micro- and nano-formulations, sustained-release systems, and targeted delivery strategies. Furthermore, this article delves into the bottlenecks that have impeded the widespread adoption of these excipients, including formulation stability, biocompatibility, regulatory constraints, and cost-effectiveness. Through a critical evaluation of existing research and industry practices, this review aims to provide insights into the potential avenues for innovation and development in ocular drug delivery, with a focus on addressing the existing challenges associated with processed excipients. This synthesis contributes to a deeper understanding of the promising role of processed excipients in improving ocular drug delivery systems and encourages further research and development in this rapidly evolving field.

Catechol chitosan coated dual-loaded liposomes based on oxidation and saccharification mechanisms for enhancing skin anti-aging effects

Skin aging has become a major urgent problem to be solved. Evidence reveals that oxidation and glycosylation are two dominant inducements of aging. Resveratrol (RES) with outstanding anti-oxidant effect and carnosine (CAR) with superb anti-glycation property were selected as two model drugs to evaluate the feasibility of their synergistic anti-aging effect. RES and CAR at the most desired mass ratio, supplying the most superior synergistic anti-aging effects were further encapsulated in liposomes (LP), which were separately coated with chitosan (CS) and catechol chitosan (Cat-CS) to increase the transdermal penetration. Their anti-aging efficacy was explored in human skin fibroblast (HSF) and human immortalized keratinocytes (HaCaT) cells, as well as the back skin of guinea pigs. Herein, RES and CAR at the mass ratio of 2:1 exhibited the most ideal synergistic anti-aging effect. The constructed liposomes have been shown to possess excellent fundamental properties and sustained-release properties. The aging-related indicator levels in the two cells and guinea pigs were obviously improved for the RES + CAR@Cat-CS-LP group. Additionally, skin appearance, tissue morphology, and collagen content were visibly improved, indicating its perfect anti-aging effect. In conclusion, RES + CAR@Cat-CS-LP is expected to be exploited as a potential anti-aging drug delivery system.

Polymer-Based Self-Assembled Drug Delivery Systems for Glaucoma Treatment: Design Strategies and Recent Advances

Glaucoma has become the world's leading cause of irreversible blindness, and one of its main characteristics is high intraocular pressure. Currently, the non-surgical drug treatment scheme to reduce intraocular pressure is a priority method for glaucoma treatment. However, the complex and special structure of the eye poses significant challenges to the treatment effect and safety adherence of this drug treatment approach. To address these challenges, the application of polymer-based self-assembled drug delivery systems in glaucoma treatment has emerged. This review focuses on the utilization of polymer-based self-assembled structures or materials as important functional and intelligent carriers for drug delivery in glaucoma treatment. Various drug delivery systems, such as eye drops, hydrogels, and contact lenses, are discussed. Additionally, the review primarily summarizes the design strategies and methods used to enhance the treatment effect and safety compliance of these polymer-based drug delivery systems. Finally, the discussion delves into the new challenges and prospects of employing polymer-based self-assembled drug delivery systems for the treatment of glaucoma.

Trends in Formulation Approaches for Sustained Drug Delivery to the Posterior Segment of the Eye

The eye, an intricate organ comprising physical and physiological barriers, poses a significant challenge for ophthalmic physicians seeking to treat serious ocular diseases affecting the posterior segment, such as age-related macular degeneration (AMD) and diabetic retinopathy (DR). Despite extensive efforts, the delivery of therapeutic drugs to the rear part of the eye remains an unresolved issue. This comprehensive review delves into conventional and innovative formulation strategies for drug delivery to the posterior segment of the eye. By utilizing alternative nanoformulation approaches such as liposomes, nanoparticles, and microneedle patches, researchers and clinicians can overcome the limitations of conventional eye drops and achieve more effective drug delivery to the posterior segment of the eye. These innovative strategies offer improved drug penetration, prolonged residence time, and controlled release, enhancing therapeutic outcomes for ocular diseases. Moreover, this article explores recently approved delivery systems that leverage diverse polymer technologies, such as chitosan and hyaluronic acid, to regulate drug-controlled release over an extended period. By offering a comprehensive understanding of the available formulation strategies, this review aims to empower researchers and clinicians in their pursuit of developing highly effective treatments for posterior-segment ocular diseases.

Fabrication of chitosan nanocomposites loaded with biosynthetic metallic nanoparticles and their therapeutic investigation

The present research demonstrates the formation of zinc oxide nanoparticles facilitated by Cissus quadrangularis (CQ-ZnONPs) and subsequent synthesis of chitosan-conjugated nanocomposites (CQ-CS/ZnONCs) along with their biological assessment. The biosynthesized nanoparticles and nanocomposites were physicochemically characterized and therapeutically assessed for their antioxidant, antibacterial, and antidiabetic potential. The formation of CQ-ZnONPs and CQ-CS/ZnONCs was preliminarily validated by the change in color and subsequently by UV-visible spectroscopic analysis. The crystalline peaks associated with the CQ-ZnONPs in CQ-CS/ZnONCs were established by XRD analysis. Morphological evaluation of CQ-ZnONPs and CQ-CS/ZnONCs was carried out through FE-SEM and HRTEM studies. The particle size of the CQ-ZnONPs and CQ-CS/ZnONCs was 243.3 nm and 176.6 nm, with a PDI of 0.188 and 0.199, respectively. Nanoparticles and nanocomposites expressed Zeta potential of -15.7 mV and -16.2 mV, respectively. The CQ-ZnONPs and CQ-CS/ZnONCs showed good radical effectiveness with various in-vitro assays. The formulated nanoparticles and nanocomposites displayed significant antibacterial activity against the selected bacterial pathogens. CQ-CS/ZnONCs presented noteworthy α-amylase and α-glucosidase inhibitory effects compared to CQ-ZnONPs with IC50 of 73.66 ± 1.21 μg/mL and 87.59 ± 1.29 μg/mL, respectively. Moreover, the synthesized CQ-CS/ZnONCs demonstrated 98.92 ± 0.39% and 99.58 ± 0.16% wound contraction (at 7 and 14 mg, respectively), significantly (p < 0.05) higher than the standard and CQ-ZnONPs. Thus, the CQ-ZnONPs and CQ-CS/ZnONCs could effectively develop promising drug delivery systems to inhibit pathogens and chronic tissue repair.

Perspective use of bio-adhesive liquid crystals as ophthalmic drug delivery systems

The success of many drugs in ophthalmic treatments is hindered by their physico-chemical properties and the limited precorneal retention time. Here, lyotropic liquid crystals are proposed as a new ophthalmic drug delivery system. Acyclovir was chosen as model drug for its solubility and its controlled release from cubic phase was achieved. We demonstrated the effortless application of lamellar phase on corneal surface and its ability to convert itself in cubic phase in situ. While the complex viscosity of lamellar phase was affected by temperature (5.1 ± 1.4 kPa·s at 25 °C and 0.12 ± 0.001 Pa·s at 35 °C, respectively), the cubic phase shown no changes in viscosity values and shear thinning behaviour at both temperatures and even in presence of the drug The degradation kinetic of drug-loaded cubic phase was slightly slower than the empty formulation, recording 27.92 ± 1.43% and 33.30 ± 3.11% of weight loss after 8 h. Ex vivo studies conducted on porcine eyeballs and isolated cornea confirmed the instantaneous transition to cubic phase, its ability to resist to gravity force, and forced dripping of simulated tear fluid. Histopathological investigation showed how treated cornea did not report changes in epithelial and stroma structures. In summary, lyotropic liquid crystals could represent an advantageous ophthalmic drug delivery system.

Chitosan-Based Nanogels Designed for Betanin-Rich Beetroot Extract Transport: Physicochemical and Biological Aspects

Nanotechnology has emerged as a possible solution to improve phytochemicals' limitations. The objective of the present study was to encapsulate beetroot extract (BR Ext) within a chitosan (CS)-based nanogel (NG) designed via ionic crosslinking with tripolyphosphate (TPP) for betanin (Bet) delivery, mainly in the ophthalmic environment. BR Ext is rich in betanin (Bet) according to thin layer chromatography (TLC), UV-visible spectroscopy, and HPLC analysis. NG presented a monodisperse profile with a size of 166 ± 6 nm and low polydispersity (0.30 ± 0.03). ζ potential (ζ-Pot) of +28 ± 1 is indicative of a colloidally stable system. BR Ext encapsulation efficiency (EE) was 45 ± 3%. TEM, with the respective 3D-surface plots and AFM, showed spherical-elliptical-shaped NG. The BR Ext release profile was biphasic with a burst release followed by slow and sustained phase over 12 h. Mucoadhesion assay demonstrated interactions between NG with mucin. Moreover, NG provided photoprotection and pH stability to BR Ext. FRAP and ABTS assays confirmed that BR Ext maintained antioxidant activity into NG. Furthermore, in vitro assays using human retinal cells displayed absence of cytotoxicity as well as an efficient protection against injury agents (LPS and H2O2). NGs are a promising platform for BR Ext encapsulation, exerting controlled release for ophthalmological use.

Challenges and strategies for ocular posterior diseases therapy via non-invasive advanced drug delivery

Posterior segment diseases, such as age-related macular degeneration (AMD) and diabetic retinopathy (DR) are vital factor that seriously threatens human vision health and quality of life, the treatment of which poses a great challenge to ophthalmologists and ophthalmic scientists. In particular, ocular posterior drug delivery in a non-invasive manner is highly desired but still faces many difficulties such as rapid drug clearance, limited permeability and low drug accumulation at the target site. At present, many novel non-invasive topical ocular drug delivery systems are under development aiming to improve drug delivery efficiency and biocompatibility for better therapy of posterior segment oculopathy. The purpose of this review is to present the challenges in the noninvasive treatment of posterior segment diseases, and to propose strategies to tackle these bottlenecks. First of all, barriers to ocular administration were introduced based on ocular physiological structure and behavior, including analysis and discussion on the influence of ocular structures on noninvasive posterior segment delivery. Thereafter, various routes of posterior drug delivery, both invasive and noninvasive, were illustrated, along with the respective anatomical obstacles that need to be overcome. The widespread and risky application of invasive drug delivery, and the need to develop non-invasive local drug delivery with alternative to injectable therapy were described. Absorption routes through topical administration and strategies to enhance ocular posterior drug delivery were then discussed. As a follow-up, an up-to-date research advances in non-invasive delivery systems for the therapy of ocular fundus lesions were presented, including different nanocarriers, contact lenses, and several other carriers. In conclusion, it seems feasible and promising to treat posterior oculopathy via non-invasive local preparations or in combination with appropriate devices.

Recent Advances in Chitosan-Based Applications-A Review

Chitosan derived from chitin gas gathered much interest as a biopolymer due to its known and possible broad applications. Chitin is a nitrogen-enriched polymer abundantly present in the exoskeletons of arthropods, cell walls of fungi, green algae, and microorganisms, radulae and beaks of molluscs and cephalopods, etc. Chitosan is a promising candidate for a wide variety of applications due to its macromolecular structure and its unique biological and physiological properties, including solubility, biocompatibility, biodegradability, and reactivity. Chitosan and its derivatives have been known to be applicable in medicine, pharmaceuticals, food, cosmetics, agriculture, the textile and paper industries, the energy industry, and industrial sustainability. More specifically, their use in drug delivery, dentistry, ophthalmology, wound dressing, cell encapsulation, bioimaging, tissue engineering, food packaging, gelling and coating, food additives and preservatives, active biopolymeric nanofilms, nutraceuticals, skin and hair care, preventing abiotic stress in flora, increasing water availability in plants, controlled release fertilizers, dye-sensitised solar cells, wastewater and sludge treatment, and metal extraction. The merits and demerits associated with the use of chitosan derivatives in the above applications are elucidated, and finally, the key challenges and future perspectives are discussed in detail.

Recent Progress in Chitosan-Based Nanomedicine for Its Ocular Application in Glaucoma

Glaucoma is a degenerative, chronic ocular disease that causes irreversible vision loss. The major symptom of glaucoma is high intraocular pressure, which happens when the flow of aqueous humor between the front and back of the eye is blocked. Glaucoma therapy is challenging because of the low bioavailability of drugs from conventional ocular drug delivery systems such as eye drops, ointments, and gels. The low bioavailability of antiglaucoma agents could be due to the precorneal and corneal barriers as well as the low biopharmaceutical attributes of the drugs. These limitations can be overcome by employing nanoparticulate drug delivery systems. Over the last decade, there has been a lot of interest in chitosan-based nanoparticulate systems to overcome the limitations (such as poor residence time, low corneal permeability, etc.) associated with conventional ocular pharmaceutical products. Therefore, the main aim of the present manuscript is to review the recent research work involving the chitosan-based nanoparticulate system to treat glaucoma. It discusses the significance of the chitosan-based nanoparticulate system, which provides mucoadhesion to improve the residence time of drugs and their ocular bioavailability. Furthermore, different types of chitosan-based nanoparticulate systems are also discussed, namely nanoparticles of chitosan core only, nanoparticles coated with chitosan, and hybrid nanoparticles of chitosan. The manuscript also provides a critical analysis of contemporary research related to the impact of this chitosan-based nanomedicine on the corneal permeability, ocular bioavailability, and therapeutic performance of loaded antiglaucoma agents.

Novel Approaches in the Drug Development and Delivery Systems for Age-Related Macular Degeneration

The number of patients with ocular disorders has increased due to contributing factors such as aging populations, environmental changes, smoking, genetic abnormalities, etc. Age-related macular degeneration (AMD) is one of the common ocular disorders which may advance to loss of vision in severe cases. The advanced form of AMD is classified into two types, dry (non-exudative) and wet (exudative) AMD. Although several therapeutic approaches are explored for the management of AMD, no approved therapy can substantially slow down the progression of dry AMD into the later stages. The focus of researchers in recent times has been engaged in developing targeted therapeutic products to halt the progression and maintain or improve vision in individuals diagnosed with AMD. The delivery of anti-VEGF agents using intravitreal therapy has found some success in managing AMD, and novel formulation approaches have been introduced in various studies to potentiate the efficacy. Some of the novel approaches, such as hydrogel, microspheres, polymeric nanoparticles, liposomes, implants, etc. have been discussed. Apart from this, subretinal, suprachoroidal, and port delivery systems have also been investigated for biologics and gene therapies. The unmet potential of approved therapeutic products has contributed to several patent applications in recent years. This review outlines the current treatment options, outcomes of recent research studies, and patent details around the novel drug delivery approach for the treatment of AMD.

Chitosan-graphene quantum dot based active film as smart wound dressing

Graphene quantum dots (GQDs), are biocompatible materials, with mechanical strength and stability. Chitosan, has antibacterial and anti-inflammatory properties, and biocompatibility. Wound healing is a challenging process especially in chronic diseases and infection. In this study, films consisting of chitosan and graphene quantum dots were developed for application in infected wounds. The chitosan-graphene films were prepared in the acidic solution followed by slow solvent evaporation and drying. The chitosan-graphene films were characterized by the scanning electron microscopy, x-ray diffraction, atomic force microscopy, Raman spectroscopy and thermogravimetric analysis. The films' was evaluated by the wound healing assays, hemolytic potential, and nitrite production, cytokine production and swelling potential. The obtained films were flexible and well-structured, promoting cell migration, greater antibacterial activity, lower hemolytic activity, and maintaining wound moisture. Our data suggested that the use of graphene quantum dot-containing chitosan films would be an efficient and promising way in combating wounds.

Implantable sustained-release drug delivery systems: a revolution for ocular therapeutics

PURPOSE

Due to the inimitable anatomical structure of the eyeball and various physiological barriers, conventional ocular local administration is often complicated by apparent shortcomings, such as limited bioavailability and short drug retention. Thus, developing methods for sustainable, safe and efficient drug delivery to ocular target sites has long been an urgent need. This study briefly summarizes the barriers to ocular drug administration and various ocular drug delivery routes and highlights recent progress in ocular implantable sustained-release drug delivery systems (DDSs) to provide literature evidence for developing novel ocular implants for sustained drug delivery.

METHODS

We conducted a comprehensive search of studies on ocular implantable sustained-release DDSs in PubMed and Web of Science using the following keywords: ocular, implantable and drug delivery system. More than 400 papers were extracted. Publications focused on sustained and controlled drug release were primarily considered. Experimental articles involving DDSs that cannot be implanted into the eye through surgeries and cannot be inserted into ocular tissues in solid form were excluded. Approximately 143 publications were reviewed to summarize the most current information on the subject.

RESULTS

In recent years, numerous ocular sustained-release DDSs using lipids, nanoparticles and hydrogels as carriers have emerged. With unique properties and systematic design, ocular implantable sustained-release DDSs are able to continuously maintain drug release, effectively sustain the therapeutic concentration in target tissues, and substantially enhance the therapeutic efficacy. Nevertheless, few ocular implantable sustained-release DDSs have been available in clinical use.

CONCLUSIONS

Ocular implantable sustained-release DDSs have become a new focus in the field of ocular drug development through unique designs and improvements in the materials of drug carriers, administration methods and dosage forms. With more ocular implantable sustained-release DDSs being commercialized, ocular therapeutics may be revolutionized.

Polysaccharide-based nanocomposites for biomedical applications: a critical review

Polysaccharides (PSA) have taken specific position among biomaterials for advanced applications in medicine. Nevertheless, poor mechanical properties are known as the main drawback of PSA, which highlights the need for PSA modification. Nanocomposites PSA (NPSA) are a class of biomaterials widely used as biomedical platforms, but despite their importance and worldwide use, they have not been reviewed. Herein, we critically reviewed the application of NPSA by categorizing them into generic and advanced application realms. First, the application of NPSA as drug and gene delivery systems, along with their role in the field as an antibacterial platform and hemostasis agent is discussed. Then, applications of NPSA for skin, bone, nerve, and cartilage tissue engineering are highlighted, followed by cell encapsulation and more critically cancer diagnosis and treatment potentials. In particular, three features of investigations are devoted to cancer therapy, i.e., radiotherapy, immunotherapy, and photothermal therapy, are comprehensively reviewed and discussed. Since this field is at an early stage of maturity, some other aspects such as bioimaging and biosensing are reviewed in order to give an idea of potential applications of NPSA for future developments, providing support for clinical applications. It is well-documented that using nanoparticles/nanomaterials above a critical concentration brings about concerns of toxicity; thus, their effect on cellular interactions would become critical. We compared nanoparticles used in the fabrication of NPSA in terms of toxicity mechanism to shed more light on future challenging aspects of NPSA development. Indeed, the neutralization mechanisms underlying the cytotoxicity of nanomaterials, which are expected to be induced by PSA introduction, should be taken into account for future investigations.

Biopolymeric Nanoparticles-Multifunctional Materials of the Future

Nanotechnology plays an important role in biological research, especially in the development of delivery systems with lower toxicity and greater efficiency. These include not only metallic nanoparticles, but also biopolymeric nanoparticles. Biopolymeric nanoparticles (BPNs) are mainly developed for their provision of several advantages, such as biocompatibility, biodegradability, and minimal toxicity, in addition to the general advantages of nanoparticles. Therefore, given that biopolymers are biodegradable, natural, and environmentally friendly, they have attracted great attention due to their multiple applications in biomedicine, such as drug delivery, antibacterial activity, etc. This review on biopolymeric nanoparticles highlights their various synthesis methods, such as the ionic gelation method, nanoprecipitation method, and microemulsion method. In addition, the review also covers the applications of biodegradable polymeric nanoparticles in different areas-especially in the pharmaceutical, biomedical, and agricultural domains. In conclusion, the present review highlights recent advances in the synthesis and applications of biopolymeric nanoparticles and presents both fundamental and applied aspects that can be used for further development in the field of biopolymeric nanoparticles.

Fluorescent Nanosystems for Drug Tracking and Theranostics: Recent Applications in the Ocular Field

The greatest challenge associated with topical drug delivery for the treatment of diseases affecting the posterior segment of the eye is to overcome the poor bioavailability of the carried molecules. Nanomedicine offers the possibility to overcome obstacles related to physiological mechanisms and ocular barriers by exploiting different ocular routes. Functionalization of nanosystems by fluorescent probes could be a useful strategy to understand the pathway taken by nanocarriers into the ocular globe and to improve the desired targeting accuracy. The application of fluorescence to decorate nanocarrier surfaces or the encapsulation of fluorophore molecules makes the nanosystems a light probe useful in the landscape of diagnostics and theranostics. In this review, a state of the art on ocular routes of administration is reported, with a focus on pathways undertaken after topical application. Numerous studies are reported in the first section, confirming that the use of fluorescent within nanoparticles is already spread for tracking and biodistribution studies. The first section presents fluorescent molecules used for tracking nanosystems’ cellular internalization and permeation of ocular tissues; discussions on the classification of nanosystems according to their nature (lipid-based, polymer-based, metallic-based and protein-based) follows. The following sections are dedicated to diagnostic and theranostic uses, respectively, which represent an innovation in the ocular field obtained by combining dual goals in a single administration system. For its great potential, this application of fluorescent nanoparticles would experience a great development in the near future. Finally, a brief overview is dedicated to the use of fluorescent markers in clinical trials and the market in the ocular field.

Lipid Nanoparticles as a Promising Drug Delivery Carrier for Topical Ocular Therapy-An Overview on Recent Advances

Due to complicated anatomical and physical properties, targeted drug delivery to ocular tissues continues to be a key challenge for formulation scientists. Various attempts are currently being made to improve the in vivo performance of therapeutic molecules by encapsulating them in various nanocarrier systems or devices and administering them via invasive/non-invasive or minimally invasive drug administration methods. Biocompatible and biodegradable lipid nanoparticles have emerged as a potential alternative to conventional ocular drug delivery systems to overcome various ocular barriers. Lipid-based nanocarrier systems led to major technological advancements and therapeutic advantages during the last few decades of ocular therapy, such as high precorneal residence time, sustained drug release profile, minimum dosing frequency, decreased drug toxicity, targeted site delivery, and, therefore, an improvement in ocular bioavailability. In addition, such formulations can be given as fine dispersion in patient-friendly droppable preparation without causing blurred vision and ocular sensitivity reactions. The unique advantages of lipid nanoparticles, namely, solid lipid nanoparticles, nanostructured lipid carriers, nanoemulsions, and liposomes in intraocular targeted administration of various therapeutic drugs are extensively discussed. Ongoing and completed clinical trials of various liposome-based formulations and various characterization techniques designed for nanoemulsion in ocular delivery are tabulated. This review also describes diverse solid lipid nanoparticle preparation methods, procedures, advantages, and limitations. Functionalization approaches to overcome the drawbacks of lipid nanoparticles, as well as the exploration of new functional additives with the potential to improve the penetration of macromolecular pharmaceuticals, would quickly progress the challenging field of ocular drug delivery systems.

Applications of Chitosan-Alginate-Based Nanoparticles-An Up-to-Date Review

Chitosan and alginate are two of the most studied natural polymers that have attracted interest for multiple uses in their nano form. The biomedical field is one of the domains benefiting the most from the development of nanotechnology, as increasing research interest has been oriented to developing chitosan-alginate biocompatible delivery vehicles, antimicrobial agents, and vaccine adjuvants. Moreover, these nanomaterials of natural origin have also become appealing for environmental protection (e.g., water treatment, environmental-friendly fertilizers, herbicides, and pesticides) and the food industry. In this respect, the present paper aims to discuss some of the newest applications of chitosan-alginate-based nanomaterials and serve as an inception point for further research in the field.