Levofloxacin Hemihydrate In Situ Gelling Ophthalmic Solution: Formulation Optimization and In Vitro and In Vivo Evaluation

Mesenchymal Stem Cell-Laden In Situ-Forming Hydrogel for Preventing Corneal Stromal Opacity

PURPOSE

The aims of this study were to construct a mesenchymal stem cell (MSC)-laden in situ-forming hydrogel and study its effects on preventing corneal stromal opacity.

METHODS

The native gellan gum was modified by high temperature and pressure, and the rabbit bone marrow MSCs were encapsulated before adding Ca 2+ to initiate cross-linking. The effects of the hydrogel on 3D culture and gene expression of the rabbit bone marrow MSCs were observed in vitro. Then, the MSC-hydrogel was used to repair corneal stromal injury in New Zealand white rabbits within 28 days postoperation.

RESULTS

The short-chain gellan gum solution has a very low viscosity (<0.1 Pa·s) that is ideal for encapsulating cells. Moreover, mRNA expressions of 3D-cultured MSCs coding for corneal stromal components (decorin, lumican, and keratocan) were upregulated (by 127.8, 165.5, and 25.4 times, respectively) ( P < 0.05) on day 21 in vitro and were verified by Western blotting results. For the in vivo study, the corneal densitometry of the experimental group was (20.73 ± 1.85) grayscale units which was lower than the other groups ( P < 0.05). The MSC-hydrogel downregulated mRNA expression coding for fibrosis markers (α-smooth muscle actin, vimentin, collagen type 5-α1, and collagen type 1-α1) in the rabbit corneal stroma. Furthermore, some of the 5-ethynyl-2'-deoxyuridine (EdU)-labeled MSCs integrated into the upper corneal stroma and expressed keratocyte-specific antigens on day 28 postoperation.

CONCLUSIONS

The short-chain gellan gum allows MSCs to slowly release to the corneal stromal defect and prevent corneal stromal opacity. Some of the implanted MSCs can integrate into the corneal stroma and differentiate into keratocytes.

Hydrogels for Mucosal Drug Delivery

Mucosal tissues are often a desirable site of drug action to treat disease and engage the immune system. However, systemically administered drugs suffer from limited bioavailability in mucosal tissues where technologies to enable direct, local delivery to these sites would prove useful. In this Spotlight on Applications article, we discuss hydrogels as an attractive means for local delivery of therapeutics to address a range of conditions affecting the eye, nose, oral cavity, gastrointestinal, urinary bladder, and vaginal tracts. Considering the barriers to effective mucosal delivery, we provide an overview of the key parameters in the use of hydrogels for these applications. Finally, we highlight recent work demonstrating their use for inflammatory and infectious diseases affecting these tissues.

Sorafenib-loaded nanostructured lipid carriers for topical ocular therapy of corneal neovascularization: development, in-vitro and in vivo study

Sorafenib (SRB), a multikinase inhibitor, is effective in reducing experimental corneal neovascularization (CNV) after oral administration; however, its therapeutic use in ocular surface disorders is restricted due to poor solubility and limited bioavailability. This study aimed to develop and optimize SRB-loaded nanostructured lipid carriers (SRB-NLCs) for topical ocular delivery by a central composite design response surface methodology (CCD-RSM). It was spherical and uniform in morphology with an average particle size of 111.87 ± 0.93 nm and a narrow size distribution. The in vitro drug release from the released SRB-NLC formulation was well fitted to Korsmeyer Peppas release kinetics. The cell counting kit-8 (CCK-8) cell viability assay demonstrated that SRB-NLC was not obviously cytotoxic to human corneal epithelial cells (HCECs). An in vivo ocular irritation test showed that SRB-NLC was well tolerated by rabbit eyes. Ocular pharmacokinetics revealed 6.79-fold and 1.24-fold increase in the area under concentration-time curves (AUC_0-12h) over 12 h in rabbit cornea and conjunctiva, respectively, treated with one dose of SRB-NLC compared with those treated with SRB suspension. Moreover, SRB-NLC (0.05% SRB) and dexamethasone (0.025%) similarly suppressed corneal neovascularization in mice. In conclusion, the optimized SRB-NLC formulation demonstrated excellent physicochemical properties and good tolerance, sustained release, and enhanced ocular bioavailability. It is safe and potentially effective for the treatment of corneal neovascularization.

Stimuli-Responsive Polymers for Transdermal, Transmucosal and Ocular Drug Delivery

Despite their conventional and widespread use, oral and intravenous routes of drug administration face several limitations. In particular, orally administered drugs undergo enzymatic degradation in the gastrointestinal tract and first-pass metabolism in the liver, which tend to decrease their bioavailability. Intravenous infusions of medications are invasive, painful and stressful for patients and carry the risk of infections, tissue damage and other adverse reactions. In order to account for these disadvantages, alternative routes of drug delivery, such as transdermal, nasal, oromucosal, ocular and others, have been considered. Moreover, drug formulations have been modified in order to improve their storage stability, solubility, absorption and safety. Recently, stimuli-responsive polymers have been shown to achieve controlled release and enhance the bioavailability of multiple drugs. In this review, we discuss the most up-to-date use of stimuli-responsive materials in order to optimize the delivery of medications that are unstable to pH or undergo primary metabolism via transdermal, nasal, oromucosal and ocular routes. Release kinetics, diffusion parameters and permeation rate of the drug via the mucosa or skin are discussed as well.

Potential of Stimuli-Responsive In Situ Gel System for Sustained Ocular Drug Delivery: Recent Progress and Contemporary Research

Eyesight is one of the most well-deserved blessings, amid all the five senses in the human body. It captures the raw signals from the outside world to create detailed visual images, granting the ability to witness and gain knowledge about the world. Eyes are exposed directly to the external environment; they are susceptible to the vicissitudes of diseases. The World Health Organization has predicted that the number of individuals affected by eye diseases will rise enormously in the next decades. However, the physical barriers of the eyes and the problems associated with conventional ocular formulations are significant challenges in ophthalmic drug development. This has generated the demand for a sustained ocular drug delivery system, which serves to deliver effective drug concentration at a reduced frequency for consistent therapeutic effect and better patient treatment adherence. Recent advancement in pharmaceutical dosage design has demonstrated that a stimuli-responsive in situ gel system exhibits the favorable characteristics for providing sustained ocular drug delivery and enhanced ocular bioavailability. Stimuli-responsive in situ gels undergo a phase transition (solution-gelation) in response to the ocular environmental temperature, pH, and ions. These stimuli transform the formulation into a gel at the cul de sac to overcome the shortcomings of conventional eye drops, such as rapid nasolacrimal drainage and short contact time with the ocular surface This review highlights the recent successful research outcomes of stimuli-responsive in situ gelling systems in treating in vivo models with glaucoma and various ocular infections. Additionally, it also presents the mechanism, recent development, and safety considerations of stimuli-sensitive in situ gel as the potential sustained ocular delivery system for treating common eye disorders.

Formulation and Evaluation of Levofloxacin and Betamethasone Ophthalmic Emulgel

OBJECTIVE

Drug delivery to ocular tissues is challenging due to rapid removal of instilled drug due to low resident time in ocular tissues. The aim of the study was to formulate an ophthalmic emulgel that delivers two drugs (betamethasone sodium phosphate [BSP] and levofloxacin). The new combination will allow the simultaneous administration and extended release of the two drugs which potentially improve resident time in ocular tissues, patient compliance, and adherence to treatment.

MATERIALS AND METHODS

Formulations containing different gelling agents at different concentrations were prepared to choose the optimum combination regarding physical properties and release. The emulgel formulations F1, F2, F3, and F4 were made using gelling agent 1% and 2% xanthan gum, 1% carbopole 934, and 2% methyl cellulose, respectively. F5 was formulated using 2% methyl cellulose with double the amount of poloxamer 188 as emulsifying agent. All the formulations were examined regarding their physical appearance, pH, viscosity, drug content, and in vitro drug release. The optimum formula was also examined for antibacterial activity.

RESULTS

The results demonstrated that F5 was the optimum formulation having a proper physical characteristics and release profile of both drugs, 96% and 90% for BSP and levofloxacin, respectively, compared to other formulations and commercial eye drops.

CONCLUSION

Simultaneous and extended release of the two drugs was achieved using one formulation of emulgel. The ability to deliver hydrophilic and hydrophobic drug through the same formulation without the need to use two drops will improve patient compliance and hence patient adherence to treatment.

Experimental design, formulation and in vivo evaluation of a novel topical in situ gel system to treat ocular infections

In situ gels have been extensively explored as ocular drug delivery system to enhance bioavailability and efficacy. The objective of present study was to design, formulate and evaluate ion-activated in situ gel to enhance the ocular penetration and therapeutic performance of moxifloxacin in ophthalmic delivery. A simplex lattice design was utilized to examine the effect of various factors on experimental outcomes of the in situ gel system. The influence of polymers (independent variables) such as gellan gum (X₁), sodium alginate (X₂), and HPMC (X₃) on gel strength, adhesive force, viscosity and drug release after 10 h (Q₁₀) were assessed. Selected formulation (MH7) was studied for ex vivo permeation, in vivo irritation and pharmacokinetics in rabbits. Data revealed that increase in concentration of polymers led to higher gel strength, adhesive force and viscosity, however, decreases the drug release. MH7 exhibited all physicochemical properties within acceptable limits and was stable for 6 months. Release profile of moxifloxacin from MH7 was comparable to the check point batches and followed Korsmeyer-Peppas matrix diffusion-controlled mechanism. Ocular irritation study signifies that selected formulation is safe and non-irritant for ophthalmic administration. In vivo pharmacokinetics data indicates significant improvement of moxifloxacin bioavailability (p < 0.0001) from MH7, as evidenced by higher C_max (727 ± 56 ng/ml) and greater AUC (2881 ± 108 ng h/ml), when compared with commercial eye drops (C_max; 503 ± 85 ng/ml and AUC; 978 ± 86 ng h/ml). In conclusion, developed in situ gel system (MH7) could offers a more effective and extended ophthalmic therapy of moxifloxacin in ocular infections when compared to conventional eye drops.

Strategies to prolong the residence time of drug delivery systems on ocular surface

Ocular diseases may be treated via different routes of administration, such as topical, intracameral, intravitreal, oral and parenteral. Among them the topical route is most accepted by patients, although it provides in many cases the lowest bioavailability. Indeed, when a topical formulation reaches the precorneal area, i.e., the drug absorption and/or action site, it is rapidly eliminated due to eye protection mechanisms such as blinking, basal and reflex tearing, and naso-lacrimal draining. To avoid this and to reduce the frequency of dosing, various strategies have been developed to prolong drug residence time after topical administration. These strategies include the use of viscosity increasing and mucoadhesive excipients as well as combinations thereof. From the drug delivery system point of view, liquid and semisolid formulations are preferred over solid formulations such as ocular inserts and contact lenses. Furthermore, liquid and semisolid formulations can contain nano- and microcarrier systems that contribute to a prolonged residence time. Within this review an overview about the different types of excipients and formulations as well as their performance in valid animal models and clinical trials is provided.

Ocular films versus film-forming liquid systems for enhanced ocular drug delivery

The short residence time, corneal barrier functions, and other effective eye protective mechanisms limited the ocular availability after topical application. Ocular inserts are being developed as polymer films for insertion into the conjunctival sac with the goal of increasing ocular availability. Unfortunately, these devices are not convenient for patients and are associated with many problems. The use of in situ gel/film-forming systems may provide promising alternative with comparable efficacy but this requires verification. Therefore, the current study compared ocular inserts with in situ film-forming liquids containing the same polymer components for ocular delivery of pilocarpine nitrate. Solvent casting technique was employed to prepare the inserts using and polyvinyl alcohol (PVA) as film-forming polymer blended with sodium alginate, as bioadhesive polymer. The effect of addition of either carboxymethycellulose, carbopol, polyvinylpyrrolidone, or methylcellulose was investigated. Solid-state characterization of the inserts indicated compatibility of the drug with film component. All inserts were of acceptable bioadhesive parameters and folding endurance that depended on the film composition. In vitro release studies reflected matrix diffusion kinetics for the film and liquid formulations. This confirms the in situ gelation of liquids. The calculated in vivo miotic pharmacokinetics parameters, using albino rabbits, reflected a better rank for the film but the difference was not statistically different from the in situ gel/film-forming systems. Ocular safety, as reflected by tear volume test, indicated acceptable safety of both liquid and inserts to the eye. The study suggested comparable efficacy of film-forming liquids to that of ocular films. Graphical abstract.

Eye drops and eye gels of levofloxacin: comparison of ocular absorption characterizations and therapeutic effects in the treatment of bacterial keratitis in rabbits

The aim was to reveal the characteristic profiles of the marketed levofloxacin eye drops (5 mg/ml) and levofloxacin eye gel (3 mg/g) from the pharmacokinetics and pharmacodynamics views of rabbits' eyes. A mild and a heavy bacterial keratitis models in rabbits were established. Different regimens of levofloxacin eye drops and eye gel, including phosphate buffer solution (the PBS group), the 4-Sol + 1-Gel group (rabbits were treated with 4 doses of levofloxacin eye drops and 1 dose levofloxacin eye gel per day), the 3-Sol + 1-Gel group (3 doses drops and 1 dose gel), the 4-Sol group (4 doses drops), the 4-Gel group (4 doses gel), the 3-Sol group (3 doses drops), and the 3-Gel group (3 doses gel), were applied to evaluate their efficacies. The ocular pharmacokinetics of levofloxacin eye drops and gel were also investigated. The results of mild infection groups showed that all treatment regimens significantly relieved the infection symptoms, and the treatment effect followed this order: 4-Gel > 4-Sol + 1-Gel > 3-Sol + 1-Gel > 4-Sol > 3-Gel > 3-Sol. In the heavy infection groups, all the treatment regimens significantly relieved the infection symptoms, and the treatment effect also followed the order with the mild infection results. All treatment regimens lowered the number of corneal colony forming units (CFU). Levofloxacin eye gel significantly increased intraocular penetration in rabbits' eyes. It can be concluded that the levofloxacin eye gel was more effective in treating bacterial keratitis than the levofloxacin eye drops in rabbit keratitis model with a proper treatment regimen such as 4-Gel.

Advancing the stimuli response of polymer-based drug delivery systems for ocular disease treatment

Recent exploitations of stimuli-responsive polymers as ophthalmic drug delivery systems for the treatment of eye diseases are summarized and discussed.

Biological Role of Gellan Gum in Improving Scaffold Drug Delivery, Cell Adhesion Properties for Tissue Engineering Applications

Over the past few decades, gellan gum (GG) has attracted substantial research interest in several fields including biomedical and clinical applications. The GG has highly versatile properties like easy bio-fabrication, tunable mechanical, cell adhesion, biocompatibility, biodegradability, drug delivery, and is easy to functionalize. These properties have put forth GG as a promising material in tissue engineering and regenerative medicine fields. Nevertheless, GG alone has poor mechanical strength, stability, and a high gelling temperature in physiological conditions. However, GG physiochemical properties can be enhanced by blending them with other polymers like chitosan, agar, sodium alginate, starch, cellulose, pullulan, polyvinyl chloride, xanthan gum, and other nanomaterials, like gold, silver, or composites. In this review article, we discuss the comprehensive overview and different strategies for the preparation of GG based biomaterial, hydrogels, and scaffolds for drug delivery, wound healing, antimicrobial activity, and cell adhesion. In addition, we have given special attention to tissue engineering applications of GG, which can be combined with another natural, synthetic polymers and nanoparticles, and other composites materials. Overall, this review article clearly presents a summary of the recent advances in research studies on GG for different biomedical applications.