Preparation and characterization of a hydrogel carrier to deliver gatifloxacin and its application as a therapeutic contact lens for bacterial keratitis therapy

Elucidating acceptance and clinical indications to support the rational design of drug-eluting contact lenses

The advent of drug-eluting contact lenses (DECLs) has opened up new avenues for the treatment of eye diseases. DECLs is expected to partially overcome the shortcomings of eye drops due to single-dose packaging, accurate dosing, prolonged drug elution behavior, and simplified dosing procedures. Currently, a significant proportion of the DECLs design effort has been directed towards enhancing the compatibility of contact lenses with drugs. The appropriate elution time for the drug remains unclear. Additionally, it is ambiguous for which ophthalmic diseases DECLs offers the greatest therapeutic advantage. To rationally design DECLs in practice, it is necessary to understand the acceptance of DECLs by patients and practitioners and to clarify the indications for DECLs. This review will first focus on the acceptance of DECLs by different patients and practitioners and discuss the factors that influence its acceptance. Secondly, this review presents an overview of the current effectiveness of DECLs treatments in animals and in the clinical phase, with a particular focus on the suitability of DECLs for the treatment of ophthalmic diseases. Overall, patients and practitioners expressed positive attitudes towards DECLs. However, this is related to factors such as DECLs' treatment cycle, safety, and price. In addition, DECLs has good application prospects for ocular wound healing, postoperative management, and treatment of contact lenses-related complications. Furthermore, chronic diseases such as glaucoma that necessitate long-term medication and intraocular diseases that require implants or injections represent additional potential applications for DECLs. It is hoped that this review will facilitate a deeper understanding of DECLs acceptance and indications, thereby supporting the rational design of DECLs. At the same time, this review provides a reference for the design of other drug-device combination products.

Novel Drug Delivery Systems to Improve the Treatment of Keratitis

Keratitis is a disease characterized by inflammation of the cornea caused by different pathogens. It can cause serious visual morbidity if not treated quickly. Depending on the pathogen causing keratitis, eye drops containing antibacterial, antifungal, or antiviral agents such as besiloxacin, moxifloxacin, ofloxacin, voriconazol, econazole, fluconazole, and acyclovir are used, and these drops need to be applied frequently due to their low bioavailability. Studies are carried out on formulations with extended residence time in the cornea and increased permeability. These formulations include various new drug delivery systems such as inserts, nanoparticles, liposomes, niosomes, cubosomes, microemulsions, in situ gels, contact lenses, nanostructured lipid carriers, carbon quantum dots, and microneedles. Ex vivo and in vivo studies with these formulations have shown that the residence time of the active substances in the cornea is prolonged, and their ocular bioavailability is increased. In addition, in vivo studies have shown that these formulations successfully treat keratitis. However, it has been observed that fluoroquinolones are used in most of the studies; similar drug delivery systems are generally preferred for antifungal drugs, and studies for viral and acanthameba keratitis are limited. There is a need for new studies on different types of keratitis and different drug active substances. At the same time, proving the efficacy of drug delivery systems, which give promising results in in vivo animal models, with clinical studies is of great importance for progress in the treatment of keratitis.

Treatment of Severe Acute Bacterial Keratitis in Rabbits Using Continuous Topical Ocular Instillation with Norvancomycin

Purpose

Efficacy of norvancomycin (NVCM) through continuous topical ocular instillation drug delivery (CTOIDD) system for treating severe acute bacterial keratitis infection with Staphylococcus aureus was investigated.

Methods

Rabbits with bacterial keratitis were treated using CTOIDD with NVCM (n=13), topical NVCM eye drops (n=11), and CTOIDD with saline (n=8). Clinical signs of keratitis in all groups were assessed consecutively for a week. Bacterial quantification of excised corneas was counted on the fourth and eighth days. Histopathologic examinations were performed to assess inflammatory cell infiltration on the eighth day.

Results

All signs of bacterial keratitis were alleviated in CTOIDD with NVCM according to criteria, and the CTOIDD-NVCM group had significantly less inflammation than CTOIDD-saline (p<0.05), and eye drop-NVCM (p<0.05). Two eyes in the eye drop-NVCM group, four eyes in the CTOIDD-saline group had corneal perforation (CP), while none of the rabbits showed CP in the CTOIDD-NVCM group. Bacterial counts were significantly less in the CTOIDD with NVCM group in comparison to the eye drop-NVCM (p<0.05), and CTOIDD-saline (p<0.05) groups. Severe inflammation and marked inflammatory cell infiltration were found in histopathologic examinations in the CTOIDD-saline and eye drop-NVCM groups, while significantly less inflammation was documented in the CTOIDD-NVCM (p<0.05) group.

Conclusion

CTOIDD with NVCM effectively reduced the severity and treated acute bacterial S. aureus keratitis infection in a rabbit model. The presented approach of CTOIDD with NVCM appears to be a promising therapeutic approach for severe acute bacterial keratitis.

Comparative Assessment of Distribution Characteristics and Ocular Pharmacokinetics of Norvancomycin Between Continuous Topical Ocular Instillation and Hourly Administration of Eye Drop

Background

The aim of this study was to compare the distribution characteristics and ocular pharmacokinetics of norvancomycin (NVCM) in ocular tissues of the anterior segment between continuous topical ocular instillation and hourly administration of eye drop in rabbits.

Methods

Sixty rabbits were randomly divided into two groups: continuous topical ocular instillation drug delivery (CTOIDD) group and eye drop (control) group. In the CTOIDD group, NVCM solution (50 mg/mL) was perfused to the ocular surface using the CTOIDD system at 2 mL/h up to 10 h and the same solution was administered at one drop (50 μL) per hour for 10 h in the control group. Animals (N=6 per time-point per group) were humanely killed at 2, 4, 6, 10, and 24 h to analyze their ocular tissues and plasma. The concentrations of NVCM in the conjunctiva, cornea, aqueous humour, iris, ciliary body and plasma were measured by HPLC with photodiode array detector. The pharmacokinetic parameters were calculated by Kinetica 5.1.

Results

The highest concentrations of NVCM for the CTOIDD group and control group were 2105.45±919.89 μg/g and 97.18±43.14 μg/g in cornea, 3033.92±1061.95 μg/g and 806.99±563.02 μg/g in conjunctiva, 1570.19±402.87 μg/g and 46.93±23.46 μg/g in iris, 181.94±47.11 μg/g and 15.38±4.00 μg/g in ciliary body, 29.78±4.90 μg/mL and 3.20±1.48 μg/mL in aqueous humour, and 26.89±5.57 μg/mL and 1.90±1.87 μg/mL in plasma, respectively. The mean NVCM levels significantly increased at all time-points in cornea, iris, and ciliary body (p<0.05) in the CTOIDD group. The AUC_0–24 values in the CTOIDD group were 27,543.70 μg·h/g in cornea, 32,514.48 μg·h/g in conjunctiva, 8631.05 μg·h/g in iris, 2194.36 μg·h/g in ciliary body and 343.9 μg·h/mL in aqueous humour, which were higher than for the eye drop group in all tissues.

Conclusion

Since continuous instillation of NVCM with CTOIDD could reach significantly higher concentrations and was sustained for a longer period compared with hourly administration of eye drop, CTOIDD administered NVCM could be a possible method to treat bacterial keratitis.

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Principles of pharmacology in the eye

The eye is a highly specialized organ that is subject to a huge range of pathology. Both local and systemic disease may affect different anatomical regions of the eye. The least invasive routes for ocular drug administration are topical (e.g. eye drops) and systemic (e.g. tablets) formulations. Barriers that subserve as protection against pathogen entry also restrict drug permeation. Topically administered drugs often display limited bioavailability due to many physical and biochemical barriers including the pre-corneal tear film, the structure and biophysiological properties of the cornea, the limited volume that can be accommodated by the cul-de-sac, the lacrimal drainage system and reflex tearing. The tissue layers of the cornea and conjunctiva are further key factors that act to restrict drug delivery. Using carriers that enhance viscosity or bind to the ocular surface increases bioavailability. Matching the pH and polarity of drug molecules to the tissue layers allows greater penetration. Drug delivery to the posterior segment is a greater challenge and, currently, the standard route is via intravitreal injection, notwithstanding the risks of endophthalmitis and retinal detachment with frequent injections. Intraocular implants that allow sustained drug release are at different stages of development. Novel exciting therapeutic approaches include methods for promoting transscleral delivery, sustained release devices, nanotechnology and gene therapy.

Review: Emerging strategies for antimicrobial drug delivery to the ocular surface: Implications for infectious keratitis

Infectious keratitis is a medical emergency that can cause severe visual morbidity if not treated promptly. Depending upon the causative microorganism, effective management of infectious keratitis requires frequent application of antibacterial, antifungal, or antiviral eye drops, which may have low bioavailability, undesirable side effects, and poor patient compliance. Ocular formulations of antimicrobials that can increase corneal permeation and provide extended presence on ocular surface are being developed. Such formulations include nanoparticles, mucoadhesives, in situ forming hydrogels, and contact lenses. Testing of these formulations in in vitro models and ex vivo excised corneas, and in vivo rabbit testing have demonstrated increased bioavailability and extended presence on the cornea. Many of these formulations have also demonstrated success in treating infectious keratitis in animal models. However, the majority of studies have evaluated fluoroquinolone antibacterials, and more studies are needed to test the delivery of antifungal drugs. Moreover, additional efficacy data in animal models and future studies in humans to determine the duration of inhibitory concentrations of these antimicrobials in tear fluid will be required to prove the effectiveness of these formulations for clinical management of infectious keratitis.

Collagen membranes crosslinked by β-cyclodextrin polyrotaxane monoaldehyde with good biocompatibilities and repair capabilities for cornea repair

Better mechanical properties; suturability; corneal regeneration.

A double network strategy to improve epithelization of a poly(2-hydroxyethyl methacrylate) hydrogel for corneal repair application

This paper presents a novel double network scaffold and its preparation methods, in which a cell-affinitive hydrogel was made by poly(2-hydroxyethyl methacrylate) and modified gelatin.

Curative effect assessment of bandage contact lens in neurogenic keratitis

AIM

To observe the curative effect of bandage contact lens in neurogenic keratitis.

METHODS

Twenty cases of neurogenic keratitis were studied at the Department of Ophthalmology, the first Affiliated Hospital of China Medical University, between October 2012 and June 2013. These included 13 males and 7 females, aged from 35 to 88y. Patients were voluntarily divided into an experimental group (lens wearing group, n=10) and control group (drug therapy, n=10). In experimental group patients wore silicone hydrogel bandage soft contact lens. Both groups used the following eyedrops: 0.5% levofloxacin TID; 0.5% Sodium carboxymethyl cellulose QID; fibroblast growth factor BID; ganciclovir BID [cases complicated with herpes simplex virus (HSV)]; compound tropicamide BID (cases concurrent hypopyon). The healing time of corneal ulcer and complication rates were observed in the two groups.

RESULTS

The healing time of corneal ulcer in the experimental group was 10.80±4.44d versus 46.70±13.88d in the control group (P<0.05). No complications occurred in the experimental group, except for the lens falling off twice in one case, the patient recovered eight days after rewearing the lens. While in the control group, all cases vascularized, 2 cases were complicated with descemetocele that recovered with amniotic membrane transplantation and 1 case was complicated with corneal perforation that recovered by autologous conjunctival flap covering.

CONCLUSION

Bandage contact lens is a safe and effective method of treating neurogenic keratitis and significantly shortened the healing time of corneal ulcer.

Preparation and characterization of molecularly imprinted poly(hydroxyethyl methacrylate) microspheres for sustained release of gatifloxacin

Molecularly imprinted poly(hydroxyethyl methacrylate) microspheres (PHEMA MIPMs) were prepared via precipitation polymerization in this article, using gatifloxacin (GFLX), hydroxyethyl methacrylate (HEMA), and ethylene glycol dimethacrylate (EGDMA) as template molecule, functional monomer and cross-linker, respectively. The effects of reaction medium, initial total monomers, cross-linker and molecular imprinting on the polymerization were investigated systematically. The interaction between GFLX and HEMA in pre-solution was studied by UV-Visible spectrophotometer, both size and morphology of products were characterized by a scanning electron microscope. When the total initial monomer concentration was 1 vol%, EGDMA content was 70 mol%, a group of uniform PHEMA MIPMs were prepared at different GFLX/MAA molar ratios, with diameter range from 2.06 ± 0.07 to 2.82 ± 0.20 μm. The results of drug loading and in vitro release experiments demonstrated that PHEMA MIPMs could achieve a higher GFLX loading content and a more acceptable sustained release than non-imprinted ones.

Nanotechnology-Based Approaches for Ophthalmology Applications: Therapeutic and Diagnostic Strategies

PURPOSE

The purpose of this article was to review recent advances in applications of nanotechnology in ophthalmology.

DESIGN

Literature review.

METHODS

Research articles about nanotechnology-based treatments for particular eye diseases and diagnostic technologies were searched through Web of Science, and the most recent advances were reported.

RESULTS

Nanotechnology enabled to improve drug and gene delivery systems, medicine solubility and short half-life in biological systems, controlled release, targeted delivery, bioavailability, diffusion limitations, and biocompatibility so far. These promising achievements are the assurance of next-generation treatment technologies. As well as treatment, nanofabrications systems such as microelectromechanical manufacturing systems removed the limitations of nanodevice generations and led the development of diagnostic tools such as intraocular pressure monitors and biosensors.

CONCLUSIONS

The pursuit of personalized medicine approaches for combating ocular diseases may be possible only through the development of nanotechnology platforms that include molecular-level engineering. Nanoparticle engineering is a common thread; herein, we attempt to show unmodified nanoparticles as well as interesting and representative biomimetic strategies can be used for specific diseases. Finally, through combining microelectromechanical and nanoelectromechanical manufacturing system strategies, interesting manufacturing and sensor development can be accomplished for early detection and, in some cases, treatment of ocular diseases.