Research progress of in-situ gelling ophthalmic drug delivery system

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.

Nanoemulsion-based pseudopolyrotaxane hydrogel for enhanced corneal bioavailability and treatment of corneal inflammation

Corneal inflammation, a condition that can potentially lead to blindness, is often treated with topical eye drops. However, the limited ocular drug bioavailability of the eye drops necessitates frequent dosing. Herein, a nanoemulsion-based pseudopolyrotaxane hydrogel was fabricated to improve corneal bioavailability and thereby suppress inflammation. In this approach, dexamethasone was encapsulated into a nanoemulsion emulsified by Tween 80. The nanoemulsion was then mixed with γ-Cyclodextrin (γ-CD) aqueous solution to produce dexamethasone-loaded nanoemulsion-based pseudopolyrotaxane hydrogel (DEX-NPH) via host-guest interaction between Tween 80 and γ-CD. The hydrogel exhibited a shear-thinning and thixotropy character. In vitro drug release and hydrogel dissolution studies showed that drugs released from hydrogel predominantly in the form of nanoemulsion. The ocular surface fluorescence imaging and tear pharmacokinetics indicated that the hydrogel could significantly prolong precorneal residence time. The corneal pharmacokinetics suggested that DEX-NPH with 35 % γ-CD improved corneal bioavailability by 1.29-fold compared with nanoemulsion and by 4.09-fold compared with free drug solution. In particular, the precorneal retention capacity and corneal bioavailability could be adjusted by changing the γ-CD content in the hydrogel. Moreover, ocular irritation evaluation confirmed the excellent safety of such hydrogel. In an alkali burn-induced corneal inflammation model, the hydrogel exhibited a superior anti-inflammatory effect compared to nanoemulsion or free drug solution alone. In summary, the nanoemulsion-based pseudopolyrotaxane hydrogel is promising for enhancing corneal bioavailability and treating corneal inflammation.

In situ Forming Nanoemulgel for Diabetic Retinopathy: Development, characterization, and in vitro efficacy assessment

Diabetic retinopathy, the most common microvascular complication of diabetes mellitus, is the leading cause of vision impairment worldwide. Flavonoids with antioxidant properties have been shown to slow its progression. Myricetin, a flavonoid polyphenolic compound, possesses antioxidant properties, but its clinical use in ocular delivery is limited by poor aqueous solubility, stability, and bioavailability. Recently, in situ gels have gained interest as ocular drug delivery vehicles due to their ease of installation and sustained drug release. This study aimed to develop a myricetin-loaded thermoresponsive in situ nanoemulgel to enhance its efficacy in treating diabetic retinopathy. Nanoemulsions were developed via aqueous phase titration using Sefsol 218 as the oil phase, Kolliphore RH40 as the surfactant, and PEG 400 as the co-surfactant. Physicochemical evaluations identified formulation batch ISG17, consisting of 10% oil phase, 30% Smix (1:2), and 60% distilled water, as the optimal formulation. The developed in situ nanoemulgel showed significant enhancement in corneal permeation and retention, which was further confirmed by fluorescence microscopy. Ocular tolerability was demonstrated through corneal hydration tests and histopathology investigations. The antioxidant potential of the myricetin-loaded nanoemulgel was assessed using the DPPH assay. Myricetin was found to be an efficient antioxidant, as indicated by its IC50 values compared to ascorbic acid. The MTT cell viability assay results showed that the developed formulation effectively inhibits the proliferation of Y79 retinoblastoma cells, demonstrating comparable efficacy to the standard marketed preparation Avastin (Bevacizumab injection). In conclusion, the nanoemulsion formulation containing a thermoresponsive polymer for in situ gelling presents a promising drug delivery system, offering superior therapeutic efficacy and better patient compliance for the treatment of diabetic retinopathy.

Development of lacosamide-loaded in-situ gels through experimental design for evaluation of ocular irritation in vitro and in vivo

Lacosamide (LCM) selectively increases the slow inactivation of voltage-gated sodium channels (VGSCs) and is a N-methyl d-aspartate acid (NMDA) receptor glycine site antagonist. Therefore, it can be used in dryness-related hyperexcitability of corneal cold receptor nerve terminals. Ocular in-situ gels remain in liquid form until they reach the target site, where they undergo a sol-gel transformation in response to specific stimuli. They can show mucoadhesive properties related to the polymer used and increase the residence time of the drug in the mucosa. In the presented study, ocular in-situ gel formulation of LCM, which has potential for use in ocular diseases and consists of hyaluronic acid and poloxamer 407 as polymers, was developed using cold method. The effect of formulation components on target product properties (pH, gelation temperature and viscosity) was evaluated by design of experiments (DoE) design. The optimized LCM-loaded in-situ gel had a pH value of 6.90 ± 0.01, showed pseudo-plastic flow with a viscosity of 562 ± 58 cP at 25 °C, gelled at 33 ± 0.47 °C, and released drugs via the Peppas-Sahlin mechanism. Ocular safety was confirmed via in vitro tests using two different cell lines (L929 and Arpe-19), along with in vivo Draize tests, histological examinations, and Hen's Egg Chario-Allontioc-Membrane (HET-CAM) analysis. In vitro studies confirmed the optimized LCM-loaded in-situ gel's suitability for ocular use, demonstrating long-acting effects through controlled release. In addition, ocular irritation and histological studies have supported that it will not show any toxic effect on the eye tissue.

Construction of a thermosensitive gel based on hydroxypropyl-β-cyclodextrin/meloxicam inclusion complexes for improving meloxicam solubility and prolonging drug retention time in the cornea

The eyes are easily stimulated by external factors, which can cause inflammation. Anti-inflammatory drugs are usually used to inhibit the production of inflammatory factors. Many nonsteroidal anti-inflammatory drugs have been used for the eye, but due to the poor solubility of meloxicam, there are currently no marketed meloxicam preparations for the treatment of eye diseases. This article uses hydroxypropyl-β-CD (HP-β-CD) to encapsulate meloxicam and combined with thermosensitive gel to prepare an HP-β-CD/meloxicam inclusion complex eye thermosensitive gel, which can improved the water solubility of meloxicam and extend the retention time of the drug in the cornea, and achieve the goal of slow release through continuous dissolution. It not only has the advantages of convenient administration and accurate dosage of eye drops, but also overcomes the disadvantage of easy loss of eye drops, showing the advantages of long retention time and fewer administration times, and provides a basis for the development of other dosage forms of meloxicam.

Nanostructured Lipid Carrier-loaded In Situ Gel for Ophthalmic Drug Delivery: Preparation and In Vitro Characterization Studies

BACKGROUND

Nanostructured lipid carriers (NLCs) are explored as vehicles for ophthalmic drug delivery owing to their better drug loading, good permeation, and satisfactory safety profile.

OBJECTIVES

The purpose of the study was to fabricate and characterize an in situ ocular gel of loratadine as a model drug based on NLCs to enhance the drug residence time.

METHODS

NLCs were fabricated using the microemulsion method in which solid lipid as Compritol 888 ATO, lipid as oleic acid, surfactant as Tween 80, and isopropyl alcohol as co-surfactant as alcohol were used. Based on the evaluation of formulation batches of NLCs, the optimized batch was selected and further utilized for the formulation of in situ gel containing Carbopol 934 and HPMC K15M as gelling agents, and characterized Results: The optimized NLCs of loratadine exhibited entrapment efficiency of 83.13 ± 0.13% and an average particle size of 18.98 ± 1.22 nm. Drug content and drug release were found to be 98.67 and 92.48%, respectively. Excellent rheology and mucoadhesion were demonstrated by the loratadine NLC-loaded in situ gel to enhance its attachment to the mucosa. NLC-based in situ ocular gel showed the desired results for topical administration. The prepared gel was observed to be non-irritating to the eye.

CONCLUSION

The optimized NLC-based in situ gel formulation presented better corneal retention and it was found to be stable, offering sustained release of the drug. Thus, the joined system of sol-gel was found promising for ophthalmic drug delivery.

The effect of mucoadhesive polymers on ocular permeation of thermoresponsive in situ gel containing dexamethasone-cyclodextrin complex

Dexamethasone (DXM) is a commonly used corticosteroid in the treatment of ocular inflammatory conditions that affect more and more people. The aim of this study was to evaluate the effect of the combination of hydroxypropyl-β-cyclodextrin (HPBCD), in situ gelling formulations, and other mucoadhesive polymers, i.e., hydroxypropyl methylcellulose (HPMC) and zinc-hyaluronate (ZnHA), on permeation by applying in vitro and ex vivo ophthalmic permeation models. Additionally, gelling properties, in vitro drug release, and mucoadhesion were measured to determine the impact of these factors on permeation and ultimately on bioavailability. The results showed that GEL1 and GEL2 had an optimal gelling temperature, 36.3 ℃ and 34.6 ℃, respectively. Moreover, the combination of Poloxamer 407 (P407) with other polymers improved the mucoadhesion (GEL1: 1333.7 mN) compared with formulations containing only P407 (P12: 721.8 mN). Both HPBCD and the gel matrix had a considerable influence on the drug release and permeability of DXM, and the combination could facilitate the permeation into the aqueous humor. After 30 min of treatment, the DXM concentration in the aqueous humor was 1.16-1.37 µg∕mL in case of the gels, whereas DXM could not be detected when treated with the DXM suspension. The results of the experiments using an in vitro cell line indicated that the formulations could be considered safe for topical treatment of the eye. In conclusion, with application of a small amount of HPMC (0.2 % w∕w), the concentration of P407 could be reduced to 12 % w/w while maintaining the ideal gelling properties and gel structure without negatively affecting permeability compared with the formulation containing a higher amount of P407. Furthermore, the gel matrix may also provide programmed and elongated drug release.

Development and evaluation of ocular antibiotic-loaded soluble film inserts

Antibiotic eyedrops typically require frequent instillation due to the eye's defensive mechanisms limiting drugs from reaching target sites. This may risk patient non-adherence and treatment inefficacy. The aim of this study was to develop a biocompatible and fully soluble ocular film insert to enhance the delivery of levofloxacin, as well as the handling procedure for its administration; based on the anatomical dimensions and physiological conditions of the human eye. Inserts were prepared by solvent casting method, using HPMC, sodium alginate, gelatin, PEG 400, and levofloxacin solution, and characterised for various physicochemical properties (e.g., uniformity of weight and thickness, loss on dryness, swelling index, water uptake and surface pH). Mechanical properties were assessed and compared against a commercially available buccal film formulation. Uniformity of content and release profile of inserts were assessed by means of a validated analytical method. Antibacterial effectiveness was studied by adapted disc diffusion method on Staphylococcus aureus and Pseudomonas aeruginosa. The formulation including HPMC E15 (1250 mg), low viscosity sodium alginate (750 mg), type A gelatin (250 mg) and PEG 400 (2.5 mL) and 0.1% levofloxacin solution, resulted in high quality inserts, exhibiting uniformity of mass, thickness, and levofloxacin content, that comply with Pharmacopeial standards. Inserts were able to withstand unilinear and repeated mechanical stresses, suggesting suitability for manipulation linked to eye administration. The fully soluble levofloxacin-loaded inserts exhibited good physicochemical and mechanical characteristics, indicating good compatibility with ocular environment and administration procedure. Consistent levofloxacin content and biphasic release pattern showed immediate and sustained antimicrobial efficacy, consistently above the minimum inhibitory concentrations for the model species tested. This work also presents an experimental framework that can be adapted for designing and testing ocular drug delivery systems accounting for anatomical and physiological characteristics of the eye.

Controllable rheological properties of UV-responsive calix[4]arene gel for drug encapsulation and release

This study investigates the potential of calix[4]arene-based supramolecular gels for use in drug delivery systems, focusing on both their rheological properties and controlled drug release behavior. We explore how key factors, including temperature, solvent exchange, and UV exposure, influence the gel's mechanical strength and its ability to encapsulate and release drugs. Specifically, our work examines how these external stimuli affect the stability of the gel matrix and modulate the release rate of the encapsulated drug. By systematically evaluating the effects of each factor, we aim to identify conditions that optimize drug release kinetics. The findings offer valuable insights into the development of a tunable, responsive platform for efficient drug delivery, highlighting the potential of calix[4]arene gels as promising candidates for advanced therapeutic applications.

Optimizing chemically stable chloramphenicol in-situ gel formulations using poloxamer 407 and HPMC through full-factorial design

The primary goal was to enhance the stability and bioavailability of chloramphenicol for ophthalmic use without compromising patient comfort, such as causing blurry vision. This study employed a 2-level full factorial design to optimize the formulation, exploring different concentrations of poloxamer 407 and HPMC to achieve this objective.

Formulation of Thermo-Sensitive In Situ Gels Loaded with Dual Spectrum Antibiotics of Azithromycin and Ofloxacin

In situ gels have been developed as an innovative strategy to prolong corneal residence time and enhance drug absorption compared to traditional eye drops. Our study aimed to formulate an ophthalmic in situ gel with a combination of two thermosensitive poloxamers, P407 and P188, in an optimal ratio not only to increase the time of action but also to increase the solubility of selected antibiotics for the treatment of ophthalmic infections. Two BSC II class substances, Azithromycin and Ofloxacin, with different mechanisms of action, have been incorporated into the in situ gel system after determining their solubility. The antibiotics-loaded in situ gel formulation was evaluated for its clarity, pH, rheological properties, and gel characteristics of gelling time, temperature, and capacity. The formulation demonstrated satisfactory clarity, appropriate pH, effective gelation properties in simulated tear fluid, and suitable rheological characteristics. In addition, APIs release insight has been studied through a dissolution test, and the effectivity against sensitive and resistant bacterial strains has been proved through the antimicrobial study. Therefore, our in situ gel system based on thermosensitive poloxamers, with two hydrophobic antibiotics, AZM and OFX, can be considered a valuable approach for ophthalmic drug delivery with an enhancement of the antibiotics bioavailability through increasing the contact time with the ocular surface and enhancing patient compliance.

Role of Sterilization on In Situ Gel-Forming Polymer Stability

In recent years, stimulus-sensitive drug delivery systems have been developed for parenteral administration as a depot system. In situ systems incorporate smart polymers that undergo a phase transition at the site of administration. All parenteral and ocular dosage forms must meet sterility requirements. Careful selection of the sterilization method is required for any type of stimuli-sensitive system. Current sterilization methods are capable of altering the conformation of polymers or APIs to a certain extent, ultimately causing the loss of pharmacological and technological properties of the drug. Unfortunately, the issues of risk assessment and resolution regarding the sterilization of stimuli-sensitive systems, along with ways to stabilize such compositions, are insufficiently described in the scientific literature to date. This review provides recommendations and approaches, formulated on the basis of published experimental data, that allow the effective management of risks arising during the development of in situ systems requiring sterility.

Advancements in Ocular Therapy: A Review of Emerging Drug Delivery Approaches and Pharmaceutical Technologies

Eye disorders affect a substantial portion of the global population, yet the availability of efficacious ophthalmic drug products remains limited. This can be partly ascribed to a number of factors: (1) inadequate understanding of physiological barriers, treatment strategies, drug and polymer properties, and delivery systems; (2) challenges in effectively delivering drugs to the anterior and posterior segments of the eye due to anatomical and physiological constraints; and (3) manufacturing and regulatory hurdles in ocular drug product development. The present review discusses innovative ocular delivery and treatments, encompassing implants, liposomes, nanoparticles, nanomicelles, microparticles, iontophoresis, in situ gels, contact lenses, microneedles, hydrogels, bispecific antibodies, and gene delivery strategies. Furthermore, this review also introduces advanced manufacturing technologies such as 3D printing and hot-melt extrusion (HME), aimed at improving bioavailability, reducing therapeutic dosages and side effects, facilitating the design of personalized ophthalmic dosage forms, as well as enhancing patient compliance. This comprehensive review lastly offers insights into digital healthcare, market trends, and industry and regulatory perspectives pertaining to ocular product development.

Nanomedicine in glaucoma treatment; Current challenges and future perspectives

Glaucoma presents a significant global health concern and affects millions of individuals worldwide and predicted a high increase in prevalence of about 111 million by 2040. The current standard treatment involves hypotensive eye drops; however, challenges such as patient adherence and limited drug bioavailability hinder the treatment effectiveness. Nanopharmaceuticals or nanomedicines offer promising solutions to overcome these obstacles. In this manuscript, we summarized the current limitations of conventional antiglaucoma treatment, role of nanomedicine in glaucoma treatment, rational design, factors effecting the performance of nanomedicine and different types of nanocarriers in designing of nanomedicine along with their applications in glaucoma treatment from recent literature. Current clinical challenges that hinder real-time application of antiglaucoma nanomedicine are highlighted. Lastly, future directions are identified for improving the therapeutic potential and translation of antiglaucoma nanomedicine into clinic.

Development of Gentamicin Bilosomes Laden In Situ Gel for Topical Ocular Delivery: Optimization, In Vitro Characterization, Toxicity, and Anti-microbial Evaluation

Purpose

The eye drops are the prominent preparation used to treat surface eye disease (bacterial conjunctivitis). However, they have some limitations i.e., short corneal residence, resulting in low ocular bioavailability and necessitating frequent dose administration. The present study developed gentamicin (GE) bilosomes (BM)- laden in situ gel to improve therapeutic activity. The in situ gel system is initially in sol form before administration and converted into gel form in physiological eye conditions.

Methods

The GE-BM was developed using the thin film hydration technique and optimized by D-optimal design. GE-BM was characterized for vesicle size, entrapment efficiency, zeta potential, morphology, and Fourier transform electron microscope (FTIR). The optimized GE-BM (GE-BMopt) was incorporated into an in situ gel and assessed for physicochemical characteristics. GE-BMopt in situ gel was evaluated for in vitro release, ex vivo permeation, toxicity, and antimicrobial study.

Results

GE-BMopt has a vesicle size of 185.1±4.8nm, PDI of 0.254, zeta potential of 27.6 mV, entrapment efficiency of 81.86±1.29 %, and spherical morphology. The FTIR study presented no chemical interactions between GE and excipients. GE-BMopt in situ gel (GE-BMoptIG4) showed excellent viscosity, gelling strength, and ex-vivo bio-adhesion. GE-BMopt-IG4 showed significant high and sustained release of GE (78.08±4.73% in 12h). GE-BMopt-IG4 displayed 3.27-fold higher ex-vivo goat corneal permeation than a pure GE solution. GE-BMopt-IG4 showed good corneal tolerance without any damage or irritation. GE-BMopt-IG4 showed significantly (P<0.05) higher anti-bacterial activity (ZOI) against Staphylococcus aureus and Escherichia coli than pure GE solution.

Conclusion

The study determined that the BM in situ gel system can serve as a substitute carrier for GE to enhance its therapeutic effectiveness, and further preclinical studies are required.

Design, pharmacokinetic, and pharmacodynamic evaluation of a lecithin-chitosan hybrid nanoparticle-loaded dual-responsive in situ gel of nebivolol for effective treatment of glaucoma

In this research work, optimized nebivolol-loaded lecithin-chitosan hybrid nanoparticles (NEB-LCNPs) were prepared using sequential screening and optimization designs. The design of experiments software (DoE) was used to obtain a robust formulation that can improve ocular delivery of the NEB in the treatment of glaucoma. The optimized NEB-LCNPs had a mean particle size of 170.5 ± 5.3 nm and drug loading of 10.5 ± 1.2%. These were further loaded in a dual-responsive in situ gel, designed and reported previously by our group. The NEB-LCNPs loaded in situ gel (NEB-LCNPs-ISG) was characterized for physicochemical properties, rheological behavior, stability, in vitro dissolution, and ocular in vivo studies. The ocular pharmacokinetics showed that NEB-LCNPs-ISG had two-fold higher aqueous humor exposure with AUC0-tlast of 375.4 ng × h/mL and sustained drug concentrations for longer durations (1.7-folds higher duration with a mean residence time of 10.6 h) in comparison to a conventional aqueous suspension of NEB (NEB-Susp). Similarly, the pharmacodynamic study showed that NEB-LCNPs-ISG resulted in a higher percentage reduction in intraocular pressure (% ΔIOP) of 28.1 ± 1.8% × h, which was 2.2-times higher reduction compared to NEB-Susp (74.2 ± 3.2% × h). In addition, the pharmacodynamic effect was more sustained with a mean response time of 11.3 ± 0.2 h, a 2.8-times higher response time compared to NEB-Susp (4.06 ± 0.3 h). These results suggest that NEB-LCNPs-ISG was more effective than the conventional aqueous suspension of NEB in the treatment of glaucoma.

Development of a Temperature and pH Dual-Sensitive In-Situ Gel for Treating Allergic Conjunctivitis

The purpose of this study was to improve the efficacy of olopatadine hydrochloride (OT) in treating allergic conjunctivitis (AC). To achieve this goal, we developed an eye formulation without antimicrobial agents using a temperature-pH dual-sensitive in situ gel technology combined with heat sterilization. Various types of carbomers were evaluated and their optimal doses determined. The prescription containing poloxamer 407 (P407) and poloxamer 188 (P188) was optimized using central composite design for response surface methodology (CCD-RSM). The final optimized dual-sensitive in situ gel (TP-gel) consisted of 0.1% olopatadine hydrochloride, 18.80% P407, 0.40% P188, 0.30% Pemulen™TR-1(TR-1), 4.0% mannitol, and 0.08% Tri(hydroxymethyl)aminomethane(Tris).Sterilization was performed at a temperature of 121℃ for a duration of 20 min. Experimental results showed that TP-gel had good safety profile and remained on the ocular surface for approximately (65.83 ± 8.79) minutes, which is four times longer than eye drops. The expression levels of IL-13, IL-17, and OVA-IgE in mouse ocular tissues with allergic conjunctivitis treated with TP-gel were significantly reduced. This suggests that TP-gel has the potential to be an effective treatment method for allergic conjunctivitis.

Dexamethasone acetate loaded poly(ε-caprolactone) nanofibers for rat corneal chemical burn treatment

Topical eye drop approaches to treat ocular inflammation in dry eyes often face limitations such as low efficiency and short duration of drug delivery. Nanofibers serve to overcome the limitation of the short duration of action of topical eye drops used against ocular inflammation in dry eyes. Several attempts to develop suitable nanofibers have been made; however, there is no ideal solution. Here, we developed polycaprolactone (PCL) nanofibers loaded with dexamethasone acetate (DEX), prepared by electrospinning, as a potential ocular drug delivery platform for corneal injury treatment. Thirty-nine Sprague Dawley rats (7 weeks old males) were divided into four treatment groups after alkaline burns of the cornea; negative control (no treatment group); dexamethasone eyedrops (DEX group); PCL fiber (PCL group); dexamethasone loaded PCL (PCL + DEX group). We evaluated therapeutic efficacy of PCL + DEX by examining the epithelial wound healing effect, the extent of corneal opacity and neovascularization. Additionally, various inflammatory factors, including IL-1β, were investigated through immunochemistry, western blot analysis, and quantitative real-time RT-PCR (qRT-PCR). PCL + DEX group showed histologically alleviated signs of corneal inflammation compared with DEX group, which showed a decrease in IL-1β and MMP9 in the corneal stroma. The quantitative expression on day 1 after alkaline burn of pro-inflammatory markers, including IL-1β and IL-6, in the PCL + DEX group was significantly lower than that in the DEX group. Notably, PCL + DEX treatment significantly suppressed neovascularization, and enhanced the anti-inflammatory function of DEX during the acute phase of ocular inflammation. Collectively, these findings suggest that PCL + DEX may be a promising approach to effective drug delivery in corneal burn injuries.

Timolol Maleate in Situ Ophthalmic Mucoadhesive-Thermosensitive Gel: Development and Characterization

Objectives

The aim of this study was to prepare a sustained-delivery mucoadhesive-thermosensitive formulation containing poloxamer 338 (P338), poloxamer 188 (P188), and mucoadhesive agents, such as chitosan (CHT) and carboxymethylcellulose (CMC), to increase the ophthalmic bioavailability of timolol maleate (TM).

Materials and Methods

Gels were prepared by mixing different amounts of P338, P188, and a mucoadhesive agent in cold isotonic water using a magnetic stirrer. The sol-gel gelation time of the gels was determined using the test tube inversion method. Viscosity measurements and analysis of the mechanical properties of the gel formulations were performed. In vitro release using dialysis membranes and ex vivo permeation studies using fresh-warmed cow eyes were performed.

Results

The gelation times of formulations containing 20:2.5 (P338:P188) and 0.1% CMC and formulations containing 20:2.5 (P338:P188) and 0.1% CHT were 35 s and 26.67 s, respectively. An optimally selected CHT mucoadhesive-thermosensitive in situ gelling system can successfully control the release of moderately hydrophilic drugs, such as TM. In the viscosity study, both formulations showed Newtonian fluid, and the CHT gel's viscosity was found to be higher. The CHT gel showed better mechanical properties than the CMC gel. The amount of TM penetrating the cow cornea after 24 hours was 73.38%, 71.80%, 67.25%, and 60.55% from the CHT gel, CMC gel, TM solution, and commercial preparation, respectively.

Conclusion

The improved mucoadhesive-thermosensitive in situ gelling system successfully controlled the release of TM. The significantly lower drainage of TM into the circulation compared with eye drops is an advantage in treating glaucoma, and the use of mucoadhesive agents increases drug penetration.

Design and Evaluation of Ophthalmic Thermosensitive In Situ Gel of Compound Salvia

The compound Salvia Recipe has been shown to have a relatively significant curative effect in management of cardiovascular and cerebrovascular diseases. This work aimed to prepare a thermosensitive in situ gel (ISG) delivery system that utilizes Poloxamer 407, Poloxamer 188, and hydroxypropyl methylcellulose for ocular administration of the compound Salvia recipe to treat cardiovascular and cerebrovascular diseases. The central composite design-response surface method was utilized to improve the prescription of the gel. The formulated gel was characterized and assessed in terms of stability, retention time, in vitro release, rheology, ocular irritation, pharmacokinetics studies, and tissue distribution. The gel was a liquid solution at room temperature and became semisolid at physiological temperature, prolonging its stay time in the eye. Pharmacokinetics and tissue distribution experiments indicated that thermosensitive ISG had enhanced targeting of heart and brain tissues. Additionally, it could lower drug toxicity and side effects in the lungs and kidneys. The compound Salvia ophthalmic thermosensitive ISG is a promising drug delivery system for the management of cardiovascular and cerebrovascular illnesses.

Nebivolol Polymeric Nanoparticles-Loaded In Situ Gel for Effective Treatment of Glaucoma: Optimization, Physicochemical Characterization, and Pharmacokinetic and Pharmacodynamic Evaluation

Nebivolol hydrochloride (NEB), a 3rd-generation beta-blocker, was recently explored in managing open-angle glaucoma due to its mechanism of action involving nitric oxide release for the vasodilation. To overcome the issue of low ocular bioavailability and the systemic side effects associated with conventional ocular formulation (aqueous suspension), we designed and optimized polycaprolactone polymeric nanoparticles (NEB-PNPs) by applying design of experiments (DoE). The particle size and drug loading of the optimized NEB-PNPs were 270.9 ± 6.3 nm and 28.8 ± 2.4%, respectively. The optimized NEB-PNPs were suspended in a dual-sensitive in situ gel prepared using a mixture of P407 + P188 (as a thermo-sensitive polymer) and κCRG (as an ion-sensitive polymer), reported previously by our group. The NEB-PNPs-loaded in situ gel (NEB-PNPs-ISG) formulation was characterized for its rheological behavior, physical and chemical stability, in vitro drug release, and in vivo efficacy. The NEB-PNPs-loaded in situ gel, in ocular pharmacokinetic studies, achieved higher aqueous humor exposure (AUC0-t = 329.2 ng × h/mL) and for longer duration (mean residence time = 9.7 h) than compared to the aqueous suspension of plain NEB (AUC0-t = 189 ng × h/mL and mean residence time = 6.1 h) reported from our previous work. The pharmacokinetic performance of NEB-PNPs-loaded in situ gel translated into a pharmacodynamic response with 5-fold increase in the overall percent reduction in intraocular pressure by the formulation compared to the aqueous suspension of plain NEB reported from our previous work. Further, the mean response time of NEB-PNPs-loaded in situ gel (12.4 ± 0.6 h) was three times higher than aqueous suspension of plain NEB (4.06 ± 0.3 h).

Magnetic targeting of lornoxicam/SPION bilosomes loaded in a thermosensitive in situ hydrogel system for the management of osteoarthritis: Optimization, in vitro, ex vivo, and in vivo studies in rat model via modulation of RANKL/OPG

Osteoarthritis is a bone and joint condition characterized pathologically by articular cartilage degenerative damage and can develop into a devastating and permanently disabling disorder. This investigation aimed to formulate the anti-inflammatory drug lornoxicam (LOR) into bile salt-enriched vesicles loaded in an in situ forming hydrogel as a potential local treatment of osteoarthritis. This was achieved by formulating LOR-loaded bilosomes that are also loaded with superparamagnetic iron oxide nanoparticles (SPIONs) for intra-muscular (IM) administration to improve joint targeting and localization by applying an external magnet to the joint. A 31.22 full factorial design was employed to develop the bilosomal dispersions and the optimized formula including SPION (LSB) was loaded into a thermosensitive hydrogel. Moreover, in vivo evaluation revealed that the IM administration of LSB combined with the application of an external magnet to the joint reversed carrageen-induced suppression in motor activity and osteoprotegerin by significantly reducing the elevations in mitogen-activated protein kinases, extracellular signal-regulated kinase, and receptor activator of nuclear factor kappa beta/osteoprotegerin expressions. In addition, the histopathological evaluation of knee joint tissues showed a remarkable improvement in the injured joint tissues. The results proved that the developed LSB could be a promising IM drug delivery system for osteoarthritis management.

Antioxidant Carbon Dots Nanozyme Loaded in Thermosensitive in situ Hydrogel System for Efficient Dry Eye Disease Treatment

Purpose

Dry eye disease (DED) is a multifactorial ocular surface disease with a rising incidence. Therefore, it is urgent to construct a reliable and efficient drug delivery system for DED treatment.

Methods

In this work, we loaded C-dots nanozyme into a thermosensitive in situ gel to create C-dots@Gel, presenting a promising composite ocular drug delivery system to manage DED.

Results

This composite ocular drug delivery system (C-dots@Gel) demonstrated the ability to enhance adherence to the corneal surface and extend the ocular surface retention time, thereby enhancing bioavailability. Furthermore, no discernible ocular surface irritation or systemic toxicity was observed. In the DED mouse model induced by benzalkonium chloride (BAC), it was verified that C-dots@Gel effectively mitigated DED by stabilizing the tear film, prolonging tear secretion, repairing corneal surface damage, and augmenting the population of conjunctival goblet cells.

Conclusion

Compared to conventional dosage forms (C-dots), the C-dots@Gel could prolong exhibited enhanced retention time on the ocular surface and increased bioavailability, resulting in a satisfactory therapeutic outcome for DED.

Development and Characterization of Thermosensitive and Bioadhesive Ophthalmic Formulations Containing Flurbiprofen Solid Dispersions

In this study, we aimed to develop thermosensitive and bioadhesive in situ gelling systems containing solid dispersions of flurbiprofen (FB-SDs) using poloxamer 407 (P407) and 188 (P188) for ophthalmic delivery. FB-SDs were prepared with the melt method using P407, characterized by solubility, stability, SEM, DSC, TGA, and XRD analyses. Various formulations of poloxamer mixtures and FB-SDs were prepared using the cold method and P407/P188 (15/26.5%), which gels between 32 and 35 °C, was selected to develop an ophthalmic in situ gelling system. Bioadhesive polymers Carbopol 934P (CP) or carboxymethyl cellulose (CMC) were added in three concentrations (0.2, 0.4, and 0.6% (w/w)). Gelation temperature and time, mechanical properties, flow properties, and viscosity values were determined. The in vitro release rate, release kinetics, and the release mechanism of flurbiprofen (FB) from the ophthalmic formulations were analyzed. The results showed that FB-SDs' solubility in water increased 332-fold compared with FB. The oscillation study results indicated that increasing bioadhesive polymer concentrations decreased gelation temperature and time, and formulations containing CP gel at lower temperatures and in a shorter time. All formulations except F3 and F4 showed Newtonion flow under non-physiological conditions, while all formulations exhibited non-Newtonion pseudoplastic flow under physiological conditions. Viscosity values increased with an increase in bioadhesive polymer concertation at physiological conditions. Texture profile analysis (TPA) showed that CP-containing formulations had higher hardness, compressibility, and adhesiveness, and the gel structure of formulation F4, containing 0.6% CP, exhibited the greatest hardness, compressibility, and adhesiveness. In vitro drug release studies indicated that CP and CMC had no effect below 0.6% concentration. Kinetic evaluation favored first-order and Hixson-Crowell kinetic models. Release mechanism analysis showed that the n values of the formulations were greater than 1 except for formulation F5, suggesting that FB might be released from the ophthalmic formulations by super case II type diffusion. When all the results of this study are evaluated, the in situ gelling formulations prepared with FB-SDs that contained P407/P188 (15/26.5%) and 0.2% CP or 0.2% CMC or 0.4 CMC% (F2, F5, and F6, respectively) could be promising formulations to prolong precorneal residence time and improve ocular bioavailability of FB.

Novel Drug Delivery Systems for the Management of Fungal Keratitis

Fungal keratitis (FK) is a dangerous corneal infection that is common in tropical and subtropical areas. Its incidence is extremely high, and ocular trauma and contact lenses can lead to FK, but its common treatment such as using topical antifungal eye drop instillation is often less effective because of several drawbacks of the drugs typically used, including limited ocular penetration, high frequency of dosing, poor biocompatibility, and the potential for severe drug reactions. Therefore, the development of novel drug delivery devices for the treatment of FK is urgent. The urgent need for novel drug delivery devices to treat FK has led to the development of several techniques, including nanoparticles (NPs), in situ forming hydrogels, contact lenses, and microneedles (MNs). However, it is important to note that the main mechanisms differ between these techniques. NPs can transport large amounts of drugs and be taken up by cells owing to their large surface area and small size. In situ forming hydrogels can significantly extend the residence time of drugs because of their strong adhesive properties. Contact lenses, with their comfortable shape and drug-carrying capacity, can also act as drug delivery devices. MNs can create channels in the cornea, bypassing its barrier and enhancing drug bioavailability. This article will go over novel medication delivery techniques for treating FK and make a conclusion about their advantages and limitations in anticipation to serve the best option for the individual therapy of FK.

The effect of polyethylene cover intervention on ocular surface disorder of intensive care unit patients: a systematic review and meta-analysis

BACKGROUND

Polyethylene covers have been proven to be effective in protecting the eyes in patients with decreased or disappeared blink reflexes, but their advantages compared to other conventional methods are still unclear. This systematic review and meta-analysis study aimed to elucidate the impact of polyethylene covers in the prevention of ocular surface disease (OSD) in patients admitted to the intensive care unit (ICU).

METHODS

We searched the Scopus, PubMed, Web of Science, and Cochrane Central Register of Controlled Trials (CENTRAL) databases to identify randomized controlled trial studies. This study followed the PRISMA guidelines and used the Cochrane Collaboration tool to assess the risk of bias.

RESULTS

The findings were expressed as risk ratio (RR) with 95% confidence intervals. The incidence of OSD in the polyethylene cover group was lower than that in the eye drops group (RR = 0.27; 95% CI (0.07, 1.09), P = 0.07) and adhesive tape group (RR = 0.11, 95%CI (0.04, 0.31), P < 0:0001) but the polyethylene cover group showed no significant difference compared to the eye gel group (RR = 0.79, 95%CI (0.18, 3.51), P = 0.76) and the eye ointment group (RR = 0.85; 95% CI (0.36, 1.99), P = 0.71).

CONCLUSION

This study showed that polyethylene covers, eye gels, and eye ointments had an equal effect on preventing OSD in ICU patients, and eye drops and adhesive tapes were relatively less effective. However, other intervention methods had not been compared due to the small number of articles. Hence, further studies should assess the available methods to choose the best practical method.

In-situ gel: A smart carrier for drug delivery

In-situ gel technology is a promising drug delivery strategy that undergoes a 'sol to gel' transition upon administration, providing controlled and prolonged drug release. These gels are composed of cross-linked 3D networks of polymers, with hydrogels being a specific type of absorbing water while retaining their shape. Gelation can be triggered by various stimuli, such as temperature, pH, ions, and light. They offer several advantages like improved patient compliance, extended drug residence time, localized drug delivery, etc, but also have some disadvantages like drug degradation and limited mechanical strength. In-situ gel falls into three categories: temperature-sensitive, ion-sensitive, and pH-sensitive, but multi-responsive gels that respond to multiple stimuli have better drug release characteristics. The mechanism of in-situ gel formation involves physical and chemical mechanisms. There are various applications of in-situ gel, like ocular drug delivery, nose-to-brain delivery, etc. In this review, we have discussed the types, and mechanisms of in-situ gel & use of in-situ gel in the treatment of different diseases through various routes like buccal, vaginal, ocular, nasal, etc., along with its use in targeted drug delivery.

Commercial hydrogel product for drug delivery based on route of administration

Hydrogels are hydrophilic, three-dimensional, cross-linked polymers that absorb significant amounts of biological fluids or water. Hydrogels possess several favorable properties, including flexibility, stimulus-responsiveness, versatility, and structural composition. They can be categorized according to their sources, synthesis route, response to stimulus, and application. Controlling the cross-link density matrix and the hydrogels' attraction to water while they're swelling makes it easy to change their porous structure, which makes them ideal for drug delivery. Hydrogel in drug delivery can be achieved by various routes involving injectable, oral, buccal, vaginal, ocular, and transdermal administration routes. The hydrogel market is expected to grow from its 2019 valuation of USD 22.1 billion to USD 31.4 billion by 2027. Commercial hydrogels are helpful for various drug delivery applications, such as transdermal patches with controlled release characteristics, stimuli-responsive hydrogels for oral administration, and localized delivery via parenteral means. Here, we are mainly focused on the commercial hydrogel products used for drug delivery based on the described route of administration.

Application of Poloxamer for In Situ Eye Drop Modeling by Enrichment with Propolis and Balsam Poplar Buds Phenolic Compounds

In situ poloxamer-based gels are increasingly being explored as ocular drug delivery carriers to extend the release of active substances, thereby enhancing bioavailability. The objective of this study was to develop thermally stable in situ gels incorporating balsam poplar bud extract, propolis extract, and p-coumaric acid solution and to evaluate the physicochemical parameters of these gelified eye drops. This research assessed the compatibility of poloxamer-based eye drops with active components, their physicochemical properties, stability post-sterilization and during storage, and the release profiles of the active compounds. Fifteen eye drop formulations were prepared and categorized into three groups based on active components. One of the active components was propolis extract. As an alternative to propolis, eye drops containing the plant precursor, balsam poplar bud extract, were developed. The third group's active component was p-coumaric acid, a dominant phenolic acid in propolis and balsam poplar bud extracts. The study reported phenolic contents of 76.63 CAE mg/g for propolis and 83.25 CAE mg/g for balsam poplar bud aqueous extracts, with balsam poplar bud extracts showing higher SPF values (14.0) compared to propolis (12.7), while p-coumaric acid solution exhibited the highest SPF values (25.5). All eye drops were transparent, with pH values meeting the requirements for ocular drops. Formulations containing 8-10% poloxamer 407 met the criteria for in situ gels. All formulations remained stable for 90 days. Conclusion: The study results indicate that the formulated gels possess suitable physicochemical properties, are resistant to applied autoclaving conditions, and exhibit an extended release of active compounds with an increase in poloxamer content.

Fructus Xanthii and Magnolia liliiflora Volatile Oils Liposomes-Loaded Thermosensitive in situ Gel for Allergic Rhinitis Management

Purpose

The aim of the present study was to fabricate a Fructus Xanthii and Magnolia liliiflora volatile oils liposomes-loaded thermosensitive in situ gel (gel/LIP/volatile oil) for effectively treating allergic rhinitis via intranasal administration.

Patients and Methods

Particle size, polymer dispersity index (PDI), entrapment effectiveness, and cumulative drug permeation of the developed liposomes were assessed. Then, a thermoreversible in situ gel was created using the liposomes loaded with volatile oils of Fructus Xanthii and Magnolia liliiflora. The effectiveness of this treatment for allergic rhinitis was confirmed by evaluating nasal symptoms, and hematological results, after injecting the formulation into the ovalbumin (OVA)-sensitized mice, we conducted hematoxylin-eosin staining (HE) and immunohistochemistry to evaluate the outcomes. The effects of the gel/LIP/volatile oil formulation for nasal delivery of volatile oil in the treatment of rhinitis were then assessed.

Results

The average particle size was 95.1 ± 3.6 nm, and the encapsulation efficiencies of Fructus Xanthii and Magnolia liliiflora volatile oils were 70.42 ± 5.41% and 67.10 ± 6.08%, respectively. Drug loadings of Fructus Xanthii and Magnolia liliiflora volatile oils were 9.10 ± 0.98% and 16.10 ± 1.03%, respectively. The binary formulation produced a gel rapidly in the nasal cavity with a strong mucosal adherence at a temperature of delivering volatile oil to the nasal mucosa steadily and continuously. After nasal administration, the gel/LIP/volatile oil sustained the volatile oil delivery into the mucosa. In comparison to the monolithic formulations, the gel/LIP/volatile oil binary formulation exhibited superior performance in terms of drug delivery capability and pharmacodynamic effects.

Conclusion

This binary preparation displayed the ability to deliver drugs to the nasal mucosa and exhibited positive pharmacodynamic effects in treating OVA-induced rhinitis in mice. As a result, it has the potential to serve as a delivery platform for Traditional Chinese medicine in the treatment of allergic rhinitis.

Recent advances in nanocrystal-based technologies applied for ocular drug delivery

INTRODUCTION

The intricate physiological barriers of the eye and the limited volume of eye drops impede efficient delivery of poorly water-soluble drugs. In the last decade, nanocrystals have emerged as versatile drug delivery systems in various administration routes from bench to bedside. The unique superiorities of nanocrystals, mainly embodied in high drug-loading capacity, good mucosal adhesion and penetration, and greatly improved drug solubility, reveal a promising prospect for ocular delivery of poorly water-soluble drugs.

AREAS COVERED

This article focuses on the ophthalmic nanocrystal technologies and products that are in the literature, clinical trials, and even on the market. The recent research progress in the preparation, ocular application, and absorption of nanocrystals are highlighted, and the pros and cons of nanocrystals in overcoming the physiological barriers of the eye are also summarized.

EXPERT OPINION

Nanocrystals have demonstrated success as glucocorticoid eye drops in the treatment of anterior segment diseases. However, the thermodynamic stability of nanocrystals remains the major challenge in product development. New technologies for efficiently optimizing stabilizers and sterilization processes are still expected. Strategies to confer more diverse functions via surface modification are also worth exploration to improve the potential of nanocrystals in delivering poorly water-soluble drugs to posterior segment of the eye.

Advances in the Application of Microneedles in the Treatment of Local Organ Diseases

In recent years, microneedles (MNs) have attracted a lot of attention due to their microscale sizes and high surface area (500-1000 µm in length), allowing pain-free and efficient drug delivery through the skin. In addition to the great success of MNs based transdermal drug delivery, especially for skin diseases, increasing studies have indicated the expansion of MNs to diverse nontransdermal applications, including the delivery of therapeutics for hair loss, ocular diseases, and oral mucosal. Here, the current treatment of hair loss, eye diseases, and oral disease is discussed and an overview of recent advances in the application of MNs is provided for these three noncutaneous localized organ diseases. Particular emphasis is laid on the future trend of MNs technology development and future challenges of expanding the generalizability of MNs.

Developments in Emerging Topical Drug Delivery Systems for Ocular Disorders

According to the current information, using nano gels in the eyes have therapeutic benefits. Industry growth in the pharmaceutical and healthcare sectors has been filled by nanotechnology. Traditional ocular preparations have a short retention duration and restricted drug bioavailability because of the eye's architectural and physiological barriers, a big issue for physicians, patients, and chemists. In contrast, nano gels can encapsulate drugs within threedimensional cross-linked polymeric networks. Because of their distinctive structural designs and preparation methods, they can deliver loaded medications in a controlled and sustained manner, enhancing patient compliance and therapeutic efficacy. Due to their excellent drugloading capacity and biocompatibility, nano-gels outperform other nano-carriers. This study focuses on using nano gels to treat eye diseases and provides a brief overview of their creation and response to stimuli. Our understanding of topical drug administration will be advanced using nano gel developments to treat common ocular diseases such as glaucoma, cataracts, dry eye syndrome, bacterial keratitis, and linked medication-loaded contact lenses and natural active ingredients.

Recent advances in nanotechnology for the treatment of fungal keratitis

Fungal keratitis (FK) is a serious pathogenic disease usually associated with serious ocular complications. The current mainstay of treatment for FK is topical eye drops; however, poor corneal penetration, low bioavailability of the drug and the need to administer high and frequent doses due to the presence of an effective clearance mechanism in the eye result in poor patient compliance. Nanocarriers can extend the duration of drug action through sustained and controlled release of the drug, protect the drug from ocular enzymes and help overcome ocular barriers. In this review, we discussed the mechanisms of action of antifungal drugs, the theoretical basis for the treatment of FK, and recent advances in the clinical treatment of FK. We have summarized the results of research into the most promising nanocarriers for ocular drug delivery and highlight their efficacy and safety in the therapy.

A Mini-review on New Developments in Nanocarriers and Polymers for Ophthalmic Drug Delivery Strategies

The eye is an important and vital organ of the human body consisting of two segments - anterior and posterior segments and these segments are associated with many diseases. This review elaborates upon the various eye-related diseases with their medications and carriers used to deliver them. Delivery strategies include drugs encapsulated into liposomes, polymeric micelles of drugs, solid lipid nanoparticles, nanostructured lipid carriers, nano emulsions, and Nanosuspension used to improve penetrating properties, bioavailability, and residence time of the drugs as examples available in the literature. With regard to this, different forms of ocular drug delivery are classified and elaborated. Additionally, the possibility of addressing the physical and chemical complexities of ocular diseases and how they could be overcome with environmentally stable nanoformulations are briefly discussed. Enhanced drug delivery efficiency with various novel pharmaceuticals along with enhanced uptake by different routes/modes of drug administration. Current advancements in drug carrier systems, i.e., nanocarriers, have shown promise for improving the retention time, drug permeation and prolonging the duration of release of the drug in the ocular site. Bio-degradable polymers investigated for the preparation of nanocarriers for the entrapment of drugs and to enhance the efficacy through improved adherence of tissue in the eye, sustained release measures, enhanced bioavailability, lower toxicity, and targeted delivery is applicable. This review covers the introduction of various nanocarriers and polymers for ocular drug delivery with the purpose of enhancing the absorption, retention and bioavailability of medications in the eye.

Pharmaceutical In Situ Gel for Glaucoma: Recent Trends and Development with an Update on Research and Patents

Glaucoma is a progressive visual polyneuropathy characterized by retinal ganglion cell atrophy and optic nerve head changes. It's generally triggered due to increased intraocular pressure compared with the healthy eye. Glaucoma is treated with various medications in traditional eye drops, such as prostaglandins, carbonic anhydrase inhibitors, beta-blockers, and others. Such treatments are difficult to use and produce lachrymal leakage and inadequate corneal permeability, resulting in lower availability. Ophthalmic in situ gels, introduced in past decades with tremendous effort, are among the finest various choices to solve the drawbacks of eye drops. Employing different polymers with pH-triggered, temperature-triggered, and ion-activated processes have been used to generate ophthalmic in situ gelling treatments. Once those preparations are delivered into the eye, they change phase from sol to gel, allowing the medicine to stay in the eye for longer. These formulations are known as smart gels as they turn into gelling fluids when administered into the eyes. The different mechanisms of in situ gel formulations are used for the management of glaucoma and are discussed in this review article.

A review of recent advances in biomedical applications of smart cellulose-based hydrogels

In biomedical engineering, smart materials act as media to communicate physiological signals inspired by environmentally responsive stimuli with outer indicators for timely scrutiny and precise therapy. Various physical and chemical processes are applied in the design of specific smart functions. Hydrogels are polymeric networks consisting of hydrophilic chains and chemical groups and they have contributed their unique features in biomedical application as one of the most used smart materials. Numerous raw materials can form hydrogels, in which cellulose and its derivatives have been extensively exploited in biomedicine due to their high hydrophilicity, availability, renewability, biodegradability, biocompatibility, and multifunctional reactivity. This review collates cellulose-based hydrogels and their extensive applications in the biomedical domain, specifically benefiting from the "SMART" concept in their design, synthesis and device assembly. The first section discusses the physical and chemical crosslinking and electrospinning techniques used in the fabrication of smart cellulose-based hydrogels. The second section describes the performance of these hydrogels, and the final section is a comprehensive discussion of their biomedical applications.

Development of Carvedilol Nanoformulation-Loaded Poloxamer-Based In Situ Gel for the Management of Glaucoma

The objective of the current study was to fabricate a thermosensitive in situ gelling system for the ocular delivery of carvedilol-loaded spanlastics (CRV-SPLs). In situ gel formulations were prepared using poloxamer analogs by a cold method and was further laden with carvedilol-loaded spanlastics to boost the precorneal retention of the drug. The gelation capacity, rheological characteristics, muco-adhesion force and in vitro release of various in situ gel formulations (CS-ISGs) were studied. The optimized formula (F2) obtained at 22% w/v poloxamer 407 and 5% w/v poloxamer 188 was found to have good gelation capacity at body temperature with acceptable muco-adhesion properties, appropriate viscosity at 25 °C that would ease its ocular application, and relatively higher viscosity at 37 °C that promoted prolonged ocular residence of the formulation post eye instillation and displayed a sustained in vitro drug release pattern. Ex vivo transcorneal penetration studies through excised rabbit cornea revealed that F2 elicited a remarkable (p ˂ 0.05) improvement in CRV apparent permeation coefficient (Papp = 6.39 × 10-6 cm/s) compared to plain carvedilol-loaded in situ gel (CRV-ISG; Papp = 2.67 × 10-6 cm/s). Most importantly, in normal rabbits, the optimized formula (F2) resulted in a sustained intraocular pressure reduction and a significant enhancement in the ocular bioavailability of carvedilol, as manifested by a 2-fold increase in the AUC0-6h of CRV in the aqueous humor, compared to plain CRV-ISG formulation. To sum up, the developed thermosensitive in situ gelling system might represent a plausible carrier for ophthalmic drug delivery for better management of glaucoma.

Poloxamer sols endowed with in-situ gelability and mucoadhesion by adding hypromellose and hyaluronan for prolonging corneal retention and drug delivery

The purpose of this study was to develop poloxamer (P407)-based in-situ thermogellable hydrogels with reducing concentration of P407 by adding hypromellose (HPMC) and with enhancing mucoadhesion of resulting hydrogels by adding hyaluronic acid (HA) for prolonging ocular delivery of hydroxypropyl-β-cyclodextrin (HPβCD)-solubilized testosterone (TES). Results demonstrated that 0.5% TES solution was successfully solubilized with adding 10% HPβCD. Non-gellable 13% P407 sol became in-situ gellable with adding 2.0-2.5% HPMC and mucoadhesibility was further imporved with adding 0.3% HA-L (low MW) or HA-H (high MW). Optimized 0.5% HPβCD-solubilized TES P407-based thermogellable hydrogels with enhancement of mucoadhesion for prolonging ocular delivery comprised 13% P407, 2.5% HPMC, and 0.3% HA-L or HA-H. Furthermore, rheological measurements under simulated eye blinking confirmed that non-thixotropic properties of optimized hydrogels could be spreaded evenly and retain a greater amount of drug-loaded hydrogels on the ocular surface for a longer period to prolong drug delivery. Compared with conventional eye drops, the prolonged residence time of optimized hydrogels from ex vivo and in vivo studies were observed, indicating relationships between rheological properties and in vivo performances. It was concluded that P407-based thermosensitive hydrogels with reducing concentration of P407 and enhancing mucoadhesion was successfully formulated by adding 2.5% HPMC and 0.3% HA in 13% P407 for potentially accomplishing effective clinical treatment of DED.

Nano-composite system of traditional Chinese medicine for ocular applications: molecular docking and three-dimensional modeling insight for intelligent drug evaluation

The absorption of drugs was impeded in the posterior part of the eye due to the special structure. In addition, it was crucial to comprehend transport laws of molecules in ocular drug delivery for designing effective strategies. However, the current quality evaluation methods of the eye were backward and lack of dynamic monitoring of drug processes in vivo. Herein, nano-drug delivery system and three-dimensional (3D) model were combined to overcome the problems of low bioavailability and diffusion law. The model drugs were screened by molecular docking. The flexible nano-liposome (FNL) and temperature-sensitive gel (TSG) composite formulation was characterized through comprehensive evaluation. COMSOL software was utilized to build 3D eyeball to predict the bioavailability of drugs. The size of the preparation was about 98.34 nm which is relatively optimal for the enhanced permeability of the eyes. The formulation showed a stronger safety and non-irritant. The pharmacokinetics results of aqueous humor showed that the AUC of two drugs in this system increased by 3.79 and 3.94 times, respectively. The results of 3D calculation model proved that the concentrations of drugs reaching the retina were 1.90×10-5 mol/m3 and 6.37×10-6 mol/m3. In conclusion, the FNL-TSG markedly improved the bioavailability of multiple components in the eye. More importantly, a simplified 3D model was developed to preliminarily forecast the bioavailability of the retina after drug infusion, providing technical support for the accurate evaluation of ocular drug delivery. It provided new pattern for the development of intelligent versatile ophthalmic preparations.

Design and evaluation of in situ gel eye drops containing nanoparticles of Gemifloxacin Mesylate

Traditional eye drops used for topically administering drugs have poor ocular bioavailability due to the biological barriers of the eye. There is an interest to design and develop novel drug delivery systems that would extend the precorneal residence time, reduce the frequency of administration and decrease dose-related toxicity. This study aimed to prepare Nanoparticles of Gemifloxacin Mesylate and incorporate them into an in situ gel. The nanoparticles were prepared by ionic gelation technique, using 3² factorial design. Sodium tripolyphosphate (STPP) was used to crosslink Chitosan. The optimized formulation of the nanoparticles (GF4) contained 0.15% Gemifloxacin Mesylate, 0.15% Chitosan and 0.20% STPP, producing 71 nm particle size and 81.11% entrapment efficiency. The prepared nanoparticles showed biphasic release, with an initial burst release of 15% in 1.0 hr and a cumulative drug release of 90.53% at the end of 24 hrs. After that, the prepared nanoparticles were incorporated into an in situ gel, using Poloxamer 407, producing a sustained drug release with efficient antimicrobial activity against gram-positive and gram-negative bacteria as confirmed by the cup plate method.

Applications and Recent Developments of Hydrogels in Ophthalmology

Hydrogels are a type of functional polymer material with a three-dimensional network structure composed of physically or chemically cross-linked polymers. All hydrogels have two common features: first, their structure contains a large number of hydrophilic groups; therefore, they have a high water content and can swell in water. Second, they have good regulation, and the physical and chemical properties of their cross-linked network can be changed by environmental factors and deliberate modification methods. In recent years, the application of hydrogels in ophthalmology has gradually attracted attention. By selecting an appropriate composition and cross-linking mode, hydrogels can be used in different fields for various applications, such as gel eye drops, in situ gel preparation, intravitreal injection, and corneal contact lenses. This Review provides a detailed introduction to the classification of hydrogels and their applications in glaucoma, vitreous substitutes, fundus diseases, corneal contact lenses, corneal diseases, and cataract surgery.

Ophthalmic Bimatoprost-Loaded Niosomal In Situ Gel: Preparation, Optimization, and In Vivo Pharmacodynamics Study

This study aimed at formulating the antiglaucoma agent, Bimatoprost (BMT), into niosomal in situ gel (BMT-ISG) for ocular delivery. Niosomes containing cholesterol/span 60 entrapping BMT were fabricated using a thin-film hydration method. The fabricated niosomes were optimized and characterized for entrapment efficiency (%EE) and size. The optimized BMT-loaded niosomal formulation prepared at a cholesterol/span 60 ratio of 1:2 exhibited the highest entrapment (81.2 ± 1.2%) and a small particle size (167.3 ± 9.1 nm), and they were selected for incorporation into in situ gelling systems (BMT-ISGs) based on Pluronic F127/Pluronic F68. Finally, the in vivo efficiency of the BMT-ISG formulation, in terms of lowering the intraocular pressure (IOP) in normotensive male albino rabbits following ocular administration, was assessed and compared to that of BMT ophthalmic solution. All the formulated BMT-ISGs showed sol-gel transition temperatures ranging from 28.1 °C to 40.5 ± 1.6 °C. In addition, the BMT-ISG formulation sustained in vitro BMT release for up to 24 h. Interestingly, in vivo experiments depicted that topical ocular administration of optimized BMT-ISG formulation elicited a significant decline in IOP, with maximum mean decreases in IOP of 9.7 ± 0.6 mm Hg, compared to BMT aqueous solution (5.8 ± 0.6 mm Hg). Most importantly, no signs of irritation to the rabbit's eye were observed following topical ocular administration of the optimized BMT-ISG formulation. Collectively, our results suggested that niosomal in situ gels might be a feasible delivery vehicle for topical ocular administration of anti-glaucoma agents, particularly those with poor ocular bioavailability.

Nanomedicine for the Detection and Treatment of Ocular Bacterial Infections

Ocular bacterial infection is a prevalent cause of blindness worldwide, with substantial consequences for normal human life. Traditional treatments for ocular bacterial infections areless effective, necessitating the development of novel techniques to enable accurate diagnosis, precise drug delivery, and effective treatment alternatives. With the rapid advancement of nanoscience and biomedicine, increasing emphasis has been placed on multifunctional nanosystems to overcome the challenges posed by ocular bacterial infections. Given the advantages of nanotechnology in the biomedical industry, it can be utilized to diagnose ocular bacterial infections, administer medications, and treat them. In this review, the recent advancements in nanosystems for the detection and treatment of ocular bacterial infections are discussed; this includes the latest application scenarios of nanomaterials for ocular bacterial infections, in addition to the impact of their essential characteristics on bioavailability, tissue permeability, and inflammatory microenvironment. Through an in-depth investigation into the effect of sophisticated ocular barriers, antibacterial drug formulations, and ocular metabolism on drug delivery systems, this review highlights the challenges faced by ophthalmic medicine and encourages basic research and future clinical transformation based on ophthalmic antibacterial nanomedicine.

Microemulsions, nanoemulsions and emulgels as carriers for antifungal antibiotics

According to estimates, up to 25% of the world's population has fungal skin diseases, making them the most prevalent infectious disease. Several chemical classes of antifungal drugs are available to treat fungal infections. However, the major challenges of conventional formulations of antifungal drugs include poor pharmacokinetic profiles like solubility, low permeability, side effects and decreased efficacy. Novel drug delivery is a promising approach for overcoming pharmacokinetic limitations and increasing the effectiveness of antibiotics. In this review, we have shed light on microemulsions, nanoemulsions, and emulgels as novel drug delivery approaches for the topical delivery of antifungal antibiotics. We believe these formulations have potential translational value and could be developed for treating fungal infections in humans.

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.

Polysaccharide-Based Nanogels to Overcome Mucus, Skin, Cornea, and Blood-Brain Barriers: A Review

Nanocarriers have been extensively developed in the biomedical field to enhance the treatment of various diseases. However, to effectively deliver therapeutic agents to desired target tissues and enhance their pharmacological activity, these nanocarriers must overcome biological barriers, such as mucus gel, skin, cornea, and blood-brain barriers. Polysaccharides possess qualities such as excellent biocompatibility, biodegradability, unique biological properties, and good accessibility, making them ideal materials for constructing drug delivery carriers. Nanogels, as a novel drug delivery platform, consist of three-dimensional polymer networks at the nanoscale, offering a promising strategy for encapsulating different pharmaceutical agents, prolonging retention time, and enhancing penetration. These attractive properties offer great potential for the utilization of polysaccharide-based nanogels as drug delivery systems to overcome biological barriers. Hence, this review discusses the properties of various barriers and the associated constraints, followed by summarizing the most recent development of polysaccharide-based nanogels in drug delivery to overcome biological barriers. It is expected to provide inspiration and motivation for better design and development of polysaccharide-based drug delivery systems to enhance bioavailability and efficacy while minimizing side effects.

Antibiotic Delivery System for Treating Bacteria-Induced Anterior Blepharitis

The eyelid-related disease of blepharitis remains a tricky ocular disorder and affects patient compliance. However, there is no available and effective treatment, making it extremely challenging. Herein, an antibacterial system based on antibiotic delivery was developed and applied in a blepharitis model induced by bacteria. The antibacterial tests against Staphylococcus aureus both in vitro and in vivo demonstrated that the system shows a favorable bactericidal effect. Then, histological evaluation indicated that the system shows both antibacterial and anti-inflammatory effects. This facile design provided an effective ocular infection management, which displays a promising prospect while addressing other complex ocular disorders.

Enhancement of ocular anti-glaucomic activity of agomelatine through fabrication of hyaluronic acid modified-elastosomes: formulation, statistical optimisation, in vitro characterisation, histopathological study, and in vivo assessment

AIM

The aim of this manuscript was to fabricate agomelatine (AGM) loaded elastosomes to improve its corneal permeation and ocular bioavailability. AGM is a biopharmaceutical classification system (BCS) class II with low water solubility and high membrane permeability. It has a potent agonistic action on melatonin receptors, so it is used for glaucoma treatment.

METHODS

Elastosomes were made using modified ethanol injection technique according to a 22 × 41 full factorial design. The chosen factors were: edge activators (EAs) type, surfactant percent (SAA %w/w), and cholesterol:surfactant ratio (CH:SAA ratio). The studied responses were encapsulation efficiency percent (EE%), mean diameter, polydispersity index (PDI), zeta potential (ZP), percentage of drug released after two hours (Q2h%), and 24 hours (Q24h%).

RESULTS

The optimum formula with the desirability of 0.752 was composed of Brij98 as EA type, 15%w/w SAA%, and 1:1 CH:SAA ratio. It revealed EE% of 73.22%w/v and mean diameter, PDI, ZP, Q2h%, and Q24h% values of 484.25 nm, 0.31, -30.75 mV, 32.7%w/v, and 75.6%w/v, respectively. It demonstrated acceptable stability for three months and superior elasticity than its conventional liposome. The histopathological study ensured the tolerability of its ophthalmic application. Also, it was proven to be safe from the results of the pH and refractive index tests. The in vivo pharmacodynamic parameters of the optimum formula revealed dominance in a maximum % decrease in intraocular pressure (IOP), the area under the IOP response curve, and mean residence time with the value of 82.73%w/v, 820.69%h, and 13.98 h compared to that of the AGM solution (35.92%w/v, 181.30%h, and 7.52 h).

CONCLUSIONS

Elastosomes can be a promising option to improve AGM ocular bioavailability.