The gamut of perspectives, challenges, and recent trends for in situ hydrogels: a smart ophthalmic drug delivery vehicle

Formulation Advances in Posterior Segment Ocular Drug Delivery

Posterior segment ocular diseases, such as diabetic retinopathy, age-related macular degeneration, and retinal vein occlusion, are leading causes of vision impairment and blindness worldwide. Effective management of these conditions remains a formidable challenge due to the unique anatomical and physiological barriers of the eye, including the blood-retinal barrier and rapid drug clearance mechanisms. To address these hurdles, nanostructured drug delivery systems are proposed to overcome ocular barriers, target the retina, and enhance permeation while ensuring controlled release. Traditional therapeutic approaches, such as intravitreal injections, pose significant drawbacks, including patient discomfort, poor compliance, and potential complications. Therefore, understanding the physiology and clearance mechanism of eye could aid in the design of novel formulations that could be noninvasive and deliver drugs to reach the target site is pivotal for effective treatment strategies. This review focuses on recent advances in formulation strategies for posterior segment ocular drug delivery, highlighting their potential to overcome these limitations. Furthermore, the potential of nanocarrier systems such as in-situ gel, niosomes, hydrogels, dendrimers, liposomes, nanoparticles, and nanoemulsions for drug delivery more effectively and selectively is explored, and supplemented with illustrative examples, figures, and tables. This review aims to provide insights into the current state of posterior segment drug delivery, emphasizing the need for interdisciplinary approaches to develop patient-centric, minimally invasive, and effective therapeutic solutions.

miRNA-124 loaded extracellular vesicles encapsulated within hydrogel matrices for combating chemotherapy-induced neurodegeneration

Chemotherapy-induced neurodegeneration represents a significant challenge in cancer survivorship, manifesting in cognitive impairments that severely affect patients' quality of life. Emerging neuroregenerative therapies offer promise in mitigating these adverse effects, with miRNA-124 playing a pivotal role due to its critical functions in neural differentiation, neurogenesis, and neuroprotection. This review article delves into the innovative approach of using miRNA-124-loaded extracellular vesicles (EVs) encapsulated within hydrogel matrices as a targeted strategy for combating chemotherapy-induced neurodegeneration. We explore the biological underpinnings of miR-124 in neuroregeneration, detailing its mechanisms of action and therapeutic potential. The article further examines the roles and advantages of EVs as natural delivery systems for miRNAs and the application of hydrogel matrices in creating a sustained release environment conducive to neural tissue regeneration. By integrating these advanced materials and biological agents, we highlight a synergistic therapeutic strategy that leverages the bioactive properties of miR-124, the targeting capabilities of EVs, and the supportive framework of hydrogels. Preclinical studies and potential pathways to clinical translation are discussed, alongside the challenges, ethical considerations, and future directions in the field. This comprehensive review underscores the transformative potential of miR-124-loaded EVs in hydrogel matrices, offering insights into their development as a novel and integrative approach for addressing the complexities of chemotherapy-induced neurodegeneration.

Magnetic engineering nanoparticles: Versatile tools revolutionizing biomedical applications

The use of nanoparticles has increased significantly over the past few years in a number of fields, including diagnostics, biomedicine, environmental remediation, and water treatment, generating public interest. Among various types of nanoparticles, magnetic nanoparticles (MNPs) have emerged as an essential tool for biomedical applications due to their distinct physicochemical properties compared to other nanoparticles. This review article focuses on the recent growth of MNPs and comprehensively reviews the advantages, multifunctional approaches, biomedical applications, and latest research on MNPs employed in various biomedical techniques. Biomedical applications of MNPs hold on to their ability to rapidly switch magnetic states under an external field at room temperature. Ideally, these MNPs should be highly susceptible to magnetization when the field is applied and then lose that magnetization just as quickly once the field is removed. This unique property allows MNPs to generate heat when exposed to high-frequency magnetic fields, making them valuable tools in developing treatments for hyperthermia and other heat-related illnesses. This review underscores the role of MNPs as tools that hold immense promise in transforming various aspects of healthcare, from diagnostics and imaging to therapeutic treatments, with discussion on a wide range of peer-reviewed articles published on the subject. At the conclusion of this work, challenges and potential future advances of MNPs in the biomedical field are highlighted.

Photo-crosslinking methacrylated-amylopectin/polyacrylamide hydrogels loading curcumin for applications as degradable, injectable, and antibacterial wound dressings

The preparation of biodegradable and antibacterial hydrogels has important clinical value. In this work, a novel strategy has been developed to prepare degradable hydrogel dressings without chemical crosslinking agent using methacrylate anhydride (MA)-modified amylopectin (APMA) and polyacrylamide (PAM). After introducing CC bonds, APMA/PAM hydrogels can be formed under light irradiation. This strategy improves the gelling ability of AP and degradation properties of the hydrogel by avoiding the addition of crosslinking agent. The degradation rate of APMA/PAM hydrogel is 74.04 ± 0.69 % within 12 weeks, while that of APMA/PAM hydrogel containing crosslinking agent is only 38.5 ± 0.1 %. The APMA/PAM hydrogel loading curcumin (Cur) (APMA/PAM-Cur) exhibits high antibacterial efficiency of 98.29 ± 0.41 % and 97.18 ± 0.81 % against S. aureus and E. coli, respectively, with light irradiation. Animal experiments show that the APMA/PAM-Cur hydrogel reduces the infiltration of inflammatory factors, increases the density of collagen, and makes the newly formed granulation tissue thicker and tighter. This study not only proves the promising potential of the APMA/PAM-Cur hydrogel as degradable and antibacterial wound dressing for clinical treatment, but also provides a new strategy for developing low-cost, degradable, and antibacterial wound dressings and reducing antibiotic abuse and environmental pollution caused by medical waste.

State-of-the-art progress on locust bean gum polysaccharide for sustainable food packaging and drug delivery applications: A review with prospectives

Locust bean gum (LBG), a polysaccharide-based natural polymer, is being widely researched as an appropriate additive for various products, including food, gluten-free formulations, medicines, paper, textiles, oil well drilling, cosmetics, and medical uses. Drug delivery vehicles, packaging, batteries, and catalytic supports are all popular applications for biopolymer-based materials. This review discusses sustainable food packaging and drug delivery applications for LBG. Given the benefits of LBG polysaccharide as a source of dietary fiber, it is also being investigated as a potential treatment for many health disorders, including colorectal cancer, diabetes, and gastrointestinal difficulties. The flexibility of LBG polysaccharide allows it to form hydrogen bonds with water molecules, a crucial characteristic of biomaterials, and the film-forming properties of LBG are critical for food packaging applications. The extraction process of LBG plays an important role in properties such as viscosity and gel-forming properties. Moreover, there are multiple factors such as temperature, pressure, pH, etc. The LBG-based functional composite film is effective in improving the shelf life as well as monitoring the freshness of fruits, meat and other processed food. The LBG-based hydrogel is excellent carrier of drugs and can be used for slow and sustainable release of active components present in drugs. Thus, the primary goal of this review was to conduct a comprehensive evaluation of the literature with a focus on the composition, properties, processing, food packaging, and medicine delivery applications of LBG polysaccharides. Thus, we investigated the chemical composition, extraction, and characteristics of LBG polysaccharides that underlie their applications in the food packaging and medicine delivery fields.

Injectable hydrogels as emerging drug-delivery platforms for tumor therapy

Tumor therapy continues to be a prominent field within biomedical research. The development of various drug carriers has been propelled by concerns surrounding the side effects and targeting efficacy of various chemotherapeutic drugs and other therapeutic agents. These carriers strive to enhance drug concentration at tumor sites, minimize systemic side effects, and improve therapeutic outcomes. Among the reported delivery systems, injectable hydrogels have emerged as an emerging candidate for the in vivo delivery of chemotherapeutic drugs due to their minimal invasive drug delivery properties. This review systematically summarizes the composition and preparation methodologies of injectable hydrogels and further highlights the delivery mechanisms of diverse drugs using these hydrogels for tumor therapy, along with an in-depth discussion on the optimized therapeutic efficiency of drugs encapsulated within the hydrogels. The work concludes by providing a dynamic forward-looking perspective on the potential challenges and possible solutions of the in situ injectable hydrogels for non-surgical and real-time diagnostic applications.

Digestion of lipid micelles leads to increased membrane permeability

Lipid-based drug carriers are an attractive option to solubilise poorly water soluble therapeutics. Previously, we reported that the digestion of a short tail PC lipid (2C6PC) by the PLA2 enzyme has a significant effect on the structure and stability of the micelles it forms. Here, we studied the interactions of micelles of varying composition representing various degrees of digestion with a model ordered (70 mol% DPPC & 30 mol% cholesterol) and disordered (100% DOPC) lipid membrane. Micelles of all compositions disassociated when interacting with the two different membranes. As the percentage of digestion products (C6FA and C6LYSO) in the micelle increased, the disassociation occurred more rapidly. The C6FA inserts preferentially into both membranes. We find that all micelle components increase the area per lipid, increase the disorder and decrease the thickness of the membranes, and the 2C6PC lipid molecules have the most significant impact. Additionally, there is an increase in permeation of water into the membrane that accompanies the insertion of C6FA into the DOPC membranes. We show that the natural digestion of lipid micelles result in molecular species that can enhance the permeability of lipid membranes that in turn result in an enhanced delivery of drugs.

Emphasis on Nanostructured Lipid Carriers in the Ocular Delivery of Antibiotics

BACKGROUND

Drug distribution to the eye is still tricky because of the eye's intricate structure. Systemic delivery, as opposed to more traditional methods like eye drops and ointments, is more effective but higher doses can be harmful.

OBJECTIVE

The use of solid lipid nanoparticles (SLNPs) as a method of drug delivery has been the subject of research since the 1990s. Since SLNPs are derived from naturally occurring lipids, they pose no health risks to the user. To raise the eye's absorption of hydrophilic and lipophilic drugs, SLNs can promote corneal absorption and improve the ocular bioavailability of SLNPs.

METHODS

To address problems related to ocular drug delivery, many forms of nano formulation were developed. Some of the methods developed are, emulsification and ultra-sonication, high-speed stirring and ultra-sonication, thin layer hydration, adapted melt-emulsification, and ultrasonication techniques, hot o/w micro-emulsion techniques, etc. Results: Nanostructured lipid carriers are described in this review in terms of their ocular penetration mechanism, structural characteristic, manufacturing process, characterization, and advantages over other nanocarriers.

CONCLUSION

Recent developments in ocular formulations with nanostructured bases, such as surfacemodified attempts have been made to increase ocular bioavailability in both the anterior and posterior chambers by incorporating cationic chemicals into a wide variety of polymeric systems.

Progress of Research in In Situ Smart Hydrogels for Local Antitumor Therapy: A Review

Cancer seriously threatens human health. Surgery, radiotherapy and chemotherapy are the three pillars of traditional cancer treatment, with targeted therapy and immunotherapy emerging over recent decades. Standard drug regimens are mostly executed via intravenous injection (IV), especially for chemotherapy agents. However, these treatments pose severe risks, including off-target toxic side effects, low drug accumulation and penetration at the tumor site, repeated administration, etc., leading to inadequate treatment and failure to meet patients’ needs. Arising from these challenges, a local regional anticancer strategy has been proposed to enhance therapeutic efficacy and concomitantly reduce systemic toxicity. With the advances in biomaterials and our understanding of the tumor microenvironment, in situ stimulus-responsive hydrogels, also called smart hydrogels, have been extensively investigated for local anticancer therapy due to their injectability, compatibility and responsiveness to various stimuli (pH, enzyme, heat, light, magnetic fields, electric fields etc.). Herein, we focus on the latest progress regarding various stimuli that cause phase transition and drug release from smart hydrogels in local regional anticancer therapy. Additionally, the challenges and future trends of the reviewed in situ smart hydrogels for local drug delivery are summarized and proposed.

Responsive Hydrogels Based on Triggered Click Reactions for Liver Cancer

Globally, liver cancer, which is one of the major cancers worldwide, has attracted the growing attention of technological researchers for its high mortality and limited treatment options. Hydrogels are soft 3D network materials containing a large number of hydrophilic monomers. By adding moieties such as nitrobenzyl groups to the network structure of a cross-linked nanocomposite hydrogel, the click reaction improves drug-release efficiency in vivo, which improves the survival rate and prolongs the survival time of liver cancer patients. The application of a nanocomposite hydrogel drug delivery system can not only enrich the drug concentration at the tumor site for a long time but also effectively prevents the distant metastasis of residual tumor cells. At present, a large number of researches have been working toward the construction of responsive nanocomposite hydrogel drug delivery systems, but there are few comprehensive articles to systematically summarize these discoveries. Here, this systematic review summarizes the synthesis methods and related applications of nanocomposite responsive hydrogels with actions to external or internal physiological stimuli. With different physical or chemical stimuli, the structural unit rearrangement and the controlled release of drugs can be used for responsive drug delivery in different states.

Eco-Friendly Synthesized PVA/Chitosan/Oxalic Acid Nanocomposite Hydrogels Embedding Silver Nanoparticles as Antibacterial Materials

PVA/chitosan (PVA/CS) composite hydrogels incorporating silver nanoparticles (AgNPs) were prepared by double-cross-linked procedures: freeze−thawing and electrostatic interactions. Oxalic acid (OA) was used both for solubilization and ionic cross-linking of CS. AgNPs covered by CS (CS-AgNPs) with an average diameter of 9 nm and 18% silver were obtained in the presence of CS, acting as reducing agent and particle stabilizer. The increase of the number of freeze−thaw cycles, as well as of the PVA:CS and OA:CS ratios, resulted in an increase of the gel fraction and elastic modulus. Practically, the elastic modulus of the hydrogels increased from 3.5 kPa in the absence of OA to 11.6 kPa at a 1:1 OA:CS weight ratio, proving that OA was involved in physical cross-linking. The physicochemical properties were not altered by the addition of CS-AgNPs in low concentration; however, concentrations higher than 3% resulted in low gel fraction and elastic modulus. The amount of silver released from the composite hydrogels is very low (<0.4%), showing that AgNPs were well trapped within the polymeric matrix. The composite hydrogels displayed antimicrobial activity against S. aureus, K. pneumoniae or P. gingivalis. The low cytotoxicity and the antibacterial efficacy of hydrogels recommend them for wound and periodontitis treatment.

Design of Magnetic Hydrogels for Hyperthermia and Drug Delivery

Hydrogels are spatially organized hydrophilic polymeric systems that exhibit unique features in hydrated conditions. Among the hydrogel family, composite hydrogels are a special class that are defined as filler-containing systems with some tailor-made properties. The composite hydrogel family includes magnetic-nanoparticle-integrated hydrogels. Magnetic hydrogels (MHGs) show magneto-responsiveness, which is observed when they are placed in a magnetic field (static or oscillating). Because of their tunable porosity and internal morphology they can be used in several biomedical applications, especially diffusion-related smart devices. External stimuli may influence physical and chemical changes in these hydrogels, particularly in terms of volume and shape morphing. One of the most significant external stimuli for hydrogels is a magnetic field. This review embraces a brief overview of the fabrication of MHGs and two of their usages in the biomedical area: drug delivery and hyperthermia-based anti-cancer activity. As for the saturation magnetization imposed on composite MHGs, they are easily heated in the presence of an alternating magnetic field and the temperature increment is dependent on the magnetic nanoparticle concentration and exposure time. Herein, we also discuss the mode of different therapies based on non-contact hyperthermia heating.

Chitosan/β-glycerophosphate in situ forming thermo-sensitive hydrogel for improved ocular delivery of moxifloxacin hydrochloride

The aim of the current work is to develop a thermo-sensitive hydrogel system of moxifloxacin hydrochloride (MOX) for improved ocular delivery. Fifteen formulations were prepared at different concentrations of β-glycerophosphate disodium salt (β-GP) 12-20% (w/v) and chitosan (CS) 1.7-1.9% (w/v). The optimized MOX loaded thermo-sensitive hydrogel system (F8), consisting of CS (1.8%, w/v) and β-GP (16%, w/v), showed optimum gelation temperature (35 °C) and gelation time (2 min), thus was selected for further investigations. It showed a significant decrease (p < 0.05) in the zeta potential value compared to CS solution with a favorable pH value (7.1) and confirmed thermoreversible behavior. MOX loaded F8 displayed a porous structure under scanning electron microscopy. Rheological investigation of MOX loaded F8 revealed the presence of a strong hydrogel network with high elasticity along with a small loss factor of 0.08 indicating a great ease of gel formation. The release of MOX from F8 was found to be governed by a combined mechanism of diffusion and relaxation. Biological assessment of two concentrations of MOX loaded F8 (0.25 and 0.5%) was conducted using healthy and infected male albino New Zealand rabbits, where an improved and prolonged antibacterial activity against Staphylococcus aureus compared to plain MOX (0.5%), marketed MOX eye drops (0.5%), was shown. Moreover, histopathological examination of ocular tissues confirmed the antibacterial efficacy of the optimized formulation eight days post topical therapy. Consequently, the developed CS/β-GP thermo-sensitive hydrogel system (F8) reveals a promising potential for enhancing the ocular delivery of MOX for treatment of bacterial infections.

Advances in Injectable In Situ-Forming Hydrogels for Intratumoral Treatment

Chemotherapy has been linked to a variety of severe side effects, and the bioavailability of current chemotherapeutic agents is generally low, which decreases their effectiveness. Therefore, there is an ongoing effort to develop drug delivery systems to increase the bioavailability of these agents and minimize their side effects. Among these, intratumoral injections using in situ-forming hydrogels can improve drugs' bioavailability and minimize drugs' accumulation in non-target organs or tissues. This review describes different types of injectable in situ-forming hydrogels and their intratumoral injection for cancer treatment, after which we discuss the antitumor effects of intratumoral injection of drug-loaded hydrogels. This review concludes with perspectives on the future applicability of, and challenges for, the adoption of this drug delivery technology.

Thermo-Gelling Dendronized Chitosans as Biomimetic Scaffolds for Corneal Tissue Engineering

Biomimetic scaffolds with transparent, biocompatible, and in situ-forming properties are highly desirable for corneal tissue engineering, which can deeply fill corneal stromal defects with irregular shapes and support tissue regeneration. We here engineer a novel class of corneal scaffolds from oligoethylene glycol (OEG)-based dendronized chitosans (DCs), whose aqueous solutions show intriguing sol-gel transitions triggered by physiological temperature, resulting in highly transparent hydrogels. Gelling points of these hydrogels can be easily tuned, and furthermore, their mechanical strengths can be significantly enhanced when injected into PBS at 37 °C instead of pure water. In vitro tests indicate that these DC hydrogels exhibit excellent biocompatibility and can promote proliferation and migration of keratocyte. When applied in the rabbit eyes with corneal stromal defects, in situ formed DC hydrogels play a positive effect for new tissue regeneration. Overall, this thermo-gelling DCs possess appealing features as corneal tissue substitutes with their excellent biocompatibility and unprecedented thermoresponsiveness.

Lollipop-Inspired Multilayered Drug Delivery Hydrogel for Dual Effective, Long-Term, and NIR-Defined Glaucoma Treatment

Glaucoma is an ophthalmic disease that is characterized by elevated intraocular pressure (IOP). Eye drops are the preferred choice to reduce IOP for the treatment of glaucoma. However, the bioavailability of eye drops is low (<5%). Their long-term frequent administration cannot ensure patient compliance, which is the main reason for treatment failure. Inspired by lollipop, herein, a multilayered sodium alginate-chitosan (SA-CS) hydrogel ball (HB) decorated by zinc oxide-modified biochar (ZnO-BC) is developed as a new drug delivery system. The multilayer structure encapsulate timolol maleate (TM) and levofloxacin inside the different layers to realize the sustained release of drugs, which can control ocular hypertension and prevent infection effectively. The results show that the release of TM can be sustained in vitro for longer than 2 weeks. Moreover, IOP is also effectively reduced in vivo. Meanwhile, the photothermal conversion activity of ZnO-BC can regulate drug release on demand after stimulation by near-infrared irradiation. More importantly, the designed HB also shows good biocompatibility and antibacterial properties in vitro and in vivo. In summary, ZnO-BC-SA-CS HB can effectively reduce IOP and is expected to replace the classical tedious eye drop strategy, having potential utilization value in the treatment of glaucoma.

Genipin-cross-linked hydrogels based on biomaterials for drug delivery: a review

Genipin is a naturally occurring nontoxic cross-linker, which has been widely used for drug delivery due to its excellent biocompatibility, admirable biodegradability and stable cross-linked attributes. These advantages led to its extensive application in the fabrication of hydrogels for drug delivery. This review describes the physicochemical characteristics and pharmacological activities of genipin and attempts to elucidate the detailed mechanisms of the cross-linking reaction between genipin and biomaterials. The current article entails a general review of the different biomaterials cross-linked by genipin: chitosan and its derivatives, collagen, gelatin, etc. The genipin-cross-linked hydrogels for various pharmaceutical applications, including ocular drug delivery, buccal drug delivery, oral drug delivery, anti-inflammatory drug delivery, and antibiotic and antifungal drug delivery, are reported. Finally, the future research directions and challenges of genipin-cross-linked hydrogels for pharmaceutical applications are also discussed in this review.