Topical Instillation Research Articles

Promising therapeutic drug delivery systems for glaucoma: a comprehensive review.

The delivery of ophthalmic drugs is challenging despite easy accessibility via the ocular surface. Topical instillation of eye drops is a relatively easy and most commonly used as a conduit for drug delivery for treating a myriad of ocular morbidities, particularly involving the anterior segment, and has an additional benefit of avoiding the first-pass metabolism while passing through the systemic circulation. The primary challenges of drug administration through traditional methods include—inadequate patient education for proper drug instillation technique, compliance, adherence, and persistence. Various dynamic (choroidal and conjunctival blood flow, lymphatic clearance, and tear dilution) and static (namely, different layers of cornea, sclera, and retina including blood aqueous and blood–retinal barriers) ocular barriers limit drug delivery to the target ocular tissues. The maintenance of the therapeutic drug levels on the ocular surface for a prolonged duration is an added challenge, thus preventing persistent delivery for longer durations. These factors result in inadequate management, leading to poor prognosis in vision loss in as many as 27% of the patients diagnosed with glaucoma. We have reviewed the research and advancements in the development of novel and well-tolerated drug delivery systems with the common goal of overcoming the factors limiting adequate drug delivery to the target tissues in glaucomatous patients with traditional techniques. In the recent past, multiple research groups have successfully designed noninvasive, sustained drug delivery systems, promoting the efficacy as well as the feasibility of delivering topical drugs to the anterior segment.

Effect of topical ophthalmic instillation of rocuronium bromide on the intraocular pressure of kestrels (Falco tinnunculus) and little owls (Athene noctuae).

To assess the effect of rocuronium bromide-induced mydriasis on the intraocular pressure (IOP) of kestrels (Falco tinnunculus) and little owls (Athene noctuae). 13 adult kestrels and 13 adult little owls. All birds were ophthalmologically normal. During the first of 2 treatment periods, a 1% rocuronium bromide solution was topically instilled in both eyes of all birds at a dose of 0.12 mg (12 μL) for kestrels and 0.20 mg (20 μL) for little owls. No ophthalmic treatments were administered during the second (control) treatment period, which was conducted 1 week after the first. During both treatment periods, rebound tonometry was used to measure IOP before rocuronium bromide instillation or at the beginning of the control period (baseline) and at predetermined times after baseline or until the pupillary light reflex returned to normal. All IOP measurements were obtained between 8 am and 5 pm. The mean IOP did not differ significantly from baseline for either species during the control treatment period. During the rocuronium bromide treatment period, complete mydriasis was achieved in all birds. The mean IOP was significantly decreased from baseline and from the corresponding mean IOP for the control period beginning 60 and 30 minutes after drug instillation for kestrels and owls, respectively, and reached its nadir at 60 minutes after drug instillation for both species. Results indicated that topical instillation of rocuronium bromide in the eyes successfully induced mydriasis and decreased the IOP of common kestrels and little owls.

Optical Coherence Tomography Angiography Imaging to monitor Anti-VEGF treatment of Corneal Vascularization in a Rabbit Model

Optical coherence tomography angiography (OCTA) is a well-established non-invasive retinal vascular imaging technique. It has been recently adapted to image the anterior segment and has shown good potential to image corneal vascularisation. The purpose of the study is to evaluate the usefulness of OCTA to monitor regression of corneal vessels following anti-VEGF (vascular endothelial growth factor) treatment using a previously established corneal vascularisation rabbit model. The regression of vessels following the treatment with aflibercept and ranibizumab anti-VEGFs using both topical instillation and sub-conjunctival injection was quantified using OCTA and compared with ICGA (indocyanine green angiography). Overall vessel density measurements using OCTA showed good correlation (r = 0.988, p < 0.001) with ICGA, with no significant difference between the two treatment groups (p = 0.795). It was also shown that OCTA provided good repeatability outcomes of the quantitative measurements. Using Bland-Altman plots, vessel growth density values between anti-VEGF treatments were compared to control saline group. It was observed that aflibercept provided longer lasting effect than ranibizumab. We also observed that in both drugs, the topical route of administration topical provided longer regression outcomes compared to one-time sub-conjunctival injection. Thereby, with this pilot study, it was demonstrated that OCTA is a reliable imaging technique to follow-up and monitor corneal vascularisation and its treatment quantitatively.

Ophthalmic Drug Delivery Using Iontophoresis: Recent Clinical Applications.

Background: Iontophoresis is a noninvasive delivery system designed to overcome barriers to ocular penetration of topical ophthalmic medications by employing a low-amplitude electrical current to promote the migration of a charged drug substance across biological membranes. Trans-scleral iontophoresis of dexamethasone phosphate has demonstrated dramatically increased intraocular concentrations of dexamethasone in rabbit ocular tissues compared with topical instillation, including 50- to 100-fold greater aqueous humor concentrations. Methods: This article reviews available data on recent clinical applications of iontophoretic ophthalmic drug delivery. Results: The EyeGate II delivery system (EGDS) is a trans-scleral iontophoresis system that has been used in conjunction with EGP-437, a proprietary-charged formulation of dexamethasone phosphate for iontophoretic delivery. In patients with noninfectious anterior uveitis, EGP-437, delivered through 2 iontophoretic treatments using the EGDS, demonstrated similar efficacy to topical prednisolone acetate 1% eye drops instilled 8 times daily over 28 days, suggesting the potential to decrease or eliminate the need for daily dosing of topical steroids in this patient population. Other applications for EGP-437 delivered through the EGDS that have been explored in clinical trials include treatment of dry eye, postsurgical inflammation and pain, and scleritis. In addition, transcorneal iontophoresis has been used outside of the United States to enhance riboflavin penetration in patients undergoing corneal cross-linking as therapy for progressive keratoconus. Conclusions: The reviewed studies demonstrate the feasibility of using iontophoresis to enhance drug delivery to ocular tissues and support the potential of this noninvasive technique across a range of ophthalmic indications.

Effects of topical autologous serum on the ocular surface in patients with toxic corneal epitheliopathy induced by anti-glaucoma drugs

To investigate the effects of topical autologous serum application on the ocular surface in patients with toxic corneal epitheliopathy induced by anti-glaucoma drugs. The patients who had corneal epitheliopathy because of preservative-containing anti-glaucoma eye drops were prospectively enrolled. The epitheliopathy was refractory to preservative-free artificial tear treatment. The patients topically applied 20% autologous serum to the eye eight times per day for 1month. Baseline and one-month change in symptoms and signs were assessed by the Ocular Surface Disease Index (OSDI) questionnaire, tear film break-up time (TFBUT), Schirmer I values, corneoconjunctival staining scores, corneal sensitivity, InflammaDry® tear immunoassay, and tear cytokine profiles using a bead-based multiplex assay. A total of ten consecutive patients were enrolled between January and August 2018 and evaluated after one-month treatment with 20% autologous serum eye drops. Significant improvement was observed in symptoms (OSDI scores from 25.5 ± 20.9 to 10.5 ± 12.0; P = .039), TFBUT (from 3.1 ± 1.8s to 5.4 ± 2.3s; P = .025), corneoconjunctival staining scores (from 7.7 ± 1.8 to 1.8 ± 1.9 NEI scale; P = .005), corneal sensitivity (from 4.6 ± .9cm to 5.8 ± .5cm; P = .013), and metalloproteinase-9 levels (P = .013). There were no significant changes in Schirmer I values and tear cytokine levels on multiplex assays. Treatment-related side effects were not detected. Topical instillation of 20% autologous serum is an effective treatment for toxic corneal epitheliopathy associated with anti-glaucoma eye drops. KCT0003827.

Optimization, stabilization, and characterization of amphotericin B loaded nanostructured lipid carriers for ocular drug delivery.

The current study sought to formulate, optimize, and stabilize amphotericin B (AmB) loaded PEGylated nanostructured lipid carriers (NLC) and to study its ocular biodistribution following topical instillation. AmB loaded PEGylated NLC (AmB-PEG-NLC) were fabricated by hot-melt emulsification followed by high-pressure homogenization (HPH) technique. 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)] (mPEG-2K-DSPE) was used for surface PEGylation. mPEG-DSPE with different PEG molecular weight, 1 K, 2 K, 5 K, 10 K, and 20 K, were screened for formulation stability. Furthermore, the AmB loaded PEGylated (2K) NLC (AmB-PEG2K-NLC) was optimized using Box-Behnken design with respect to the amount of AmB, castor oil, mPEG-2K-DSPE, and number of high-pressure homogenization cycles as the factors; particle size, zeta potential, PDI, entrapment efficiency, and loading efficiency as responses. Stability of the optimized AmB-PEG2K-NLC was assessed over 4 weeks, at 4 °C as well as 25 °C and effect of autoclaving was also evaluated. AmB-PEG2K-NLC were tested for their in vitro antifungal activity against Candida albicans (ATCC 90028), AmB resistant Candida albicans (ATCC 200955) and Aspergillus fumigatus (ATCC 204305). Cytotoxicity of AmB-PEG2K-NLC was studied in human retinal pigmented epithelium cells. In vivo ocular biodistribution of AmB was evaluated in rabbits, following topical application of PEGylated NLCs or marketed AmB preparations. PEGylation with mPEG-2K-DSPE prevented leaching of AmB and increased the drug load significantly. The optimized formulation was prepared with a particle size of 218 ± 5 nm; 0.3 ± 0.02 PDI, 4.6 ± 0.1% w/w drug loading, and 92.7 ± 2.5% w/w entrapment efficiency. The optimized colloidal dispersions were stable for over a month, at both 4 °C and 25 °C. AmB-PEG2K-NLCs showed significantly (p < 0.05) better antifungal activity in both wild-type and AmB resistant Candida strains and, was comparable to, or better than, commercially available parenteral AmB formulations like Fungizone™ and AmBisome®. AmB-PEG2K-NLC did not show any toxicity up to a highest concentration of 1% (v/v) (percent formulation in medium). Following topical instillation, AmB was detected in all the ocular tissues tested and statistically significant (p > 0.05) difference was not observed between the formulations tested. An optimized autoclavable and effective AmB-PEG2K-NLC ophthalmic formulation with at least one-month stability, in the reconstituted state, has been developed.

Changes of tear film lipid layer thickness by 3% diquafosol ophthalmic solutions in patients with dry eye syndrome.

To evaluate the quantitatively changes in lipid layer thickness (LLT) when 3% diquafosol eye drop is used for dry eye patients using the tear film interferometer. A total 124 participants (32 males, 92 females; mean age, 28.9y) diagnosed with dry eye disease (DED) received topical instillation of 4 ophthalmic solutions in one eye: diquafosol, normal saline, 0.1% sodium hyaluronate and 0.3% gatifloxacin, in a masked manner. LLT was measured using an interferometer at baseline and 20min after the instillation of each ophthalmic solutions. Changes of LLT after instillation (nm, mean± standard error) were as follows: 12.6±2.0 for diquafosol (P<0.001), 1.2±2.2 for normal saline (P=0.301), 1.5±2.0 for hyaluronate (P=0.495), and 0.5±3.2 for gatifloxacin (P=0.884). Topical instillation of diquafosol increases tear film LLT in DED patients. Diquafosol 3% eye drop might be effective treatment option of evaporative DED with meibomian gland dysfunction.

Ocular Distribution of Cyclosporine Following Topical Administration of OTX-101 in New Zealand White Rabbits.

Purpose: Evaluate the ocular distribution, tolerability, and systemic exposure of cyclosporine (CsA) in New Zealand white rabbits following topical administration of OTX-101, a novel, clear aqueous nanomicellar solution developed for the treatment of dry eye disease (DED).Methods: The study design included single- and repeat-dose phases. In the single-dose phase, rabbits received a single instillation of OTX-101 0.05% or CsA ophthalmic emulsion 0.05% (Restasis®; Allergan, Irvine, CA) as a comparator. In the repeat-dosing phase, OTX-101 (0.01%, 0.05%, or 0.1% CsA) or comparator was instilled 4 times per day for 7 days. Samples collected included whole blood, tears, and ocular tissues/fluids (aqueous humor, choroid-retina, conjunctiva, cornea, superior eyelid, third eyelid, iris/ciliary body, lacrimal gland, lens, sclera, and vitreous humor). CsA concentrations were analyzed using liquid chromatography-tandem mass spectrometry.Results: Analysis included samples from 112 rabbits. The highest concentration of CsA following a single OTX-101 0.05% instillation occurred in the third eyelid (Cmax = 1,200 ng/g). Concentrations of CsA in the cornea and superior bulbar conjunctiva increased in a dose-related manner following repeated administration of OTX-101 formulations; Cmax [Tmax (h)] for cornea was 1,543 ng/g (6.50), 5,410 ng/g (7.0), and 8,123 ng/g (6.50), for 0.01%, 0.05%, and 0.1% CsA concentrations, respectively; for superior bulbar conjunctiva was 726 ng/g (6.50), 1,468 ng/g (6.50), and 2,080 ng/g (6.25), respectively.Conclusions: OTX-101 topical ophthalmic instillation resulted in extensive distribution of CsA in ocular tissues, particularly in target tissues for DED (cornea and conjunctiva), while systemic exposure was negligible.

Octopus-like Flexible Vector for Noninvasive Intraocular Delivery of Short Interfering Nucleic Acids.

Gene therapy is promising for chronic posterior ocular diseases, which are causal factors for severe vision impairment and even blindness worldwide. However, the inherent absorption barriers of the eye restrict intraocular delivery of therapeutic nucleic acids via topical instillation. Safe and efficient nonviral vectors for ocular gene therapy are still unmet clinical desires. Herein, an octopus-like flexible multivalent penetratin (MVP) was designed to facilitate condensation and delivery of therapeutic nucleic acids using multiarm polyethylene glycol (PEG) as a core and conjugating penetratin at each end of the PEG arms as outspread tentacles. Among the MVPs, 8-valent penetratin (8VP) stably compacted nucleic acids into positively charged polyplexes smaller than 100 nm, promoting cellular uptake efficiency (approaching 100%) and transfection rate (over 75%). After being instilled into the conjunctival sac, 8VP enabled rapid (<10 min) and prolonged (>6 h) distribution of nucleic acids in the retina via a noncorneal pathway. In a retinoblastoma-bearing mice model, topical instillation of 8VP/siRNA efficiently inhibited the protein expression of intraocular tumor without toxicity. MVP is advantageous over the commercial transfection reagent in safety and efficiency, and therefore provides a promising vector for noninvasive intraocular gene delivery.

Effect of topical steroids on recently developed incomplete nasolacrimal duct obstruction: optical coherence tomography study.

To evaluate the effect of a topical steroid instillation on recently developed incomplete nasolacrimal duct obstruction (NLDO) evaluated by using anterior segment optical coherence tomography (ASOCT). Forty-nine eyes of 31 patients with incomplete NLDO who developed epiphora within 3months were recruited and treated with a topical steroid for 3months. Tear meniscus height (TMH) and area (TMA) were measured by ASOCT. The treatment was considered to be effective when there was improvement of subjective epiphora, normal tear meniscus on slit lamp examination, a fluorescein dye disappearance test with grade 0 or 1, and TMH < 250μm on ASOCT. The treatment effectiveness and associated factors were analyzed. Treatment was effective in 24 eyes (49.0%) after 6months of follow-up. TMH and TMA at 3months were significantly decreased in the effective group on ASOCT (TMH: from 385 to 268μm, p = 0.002, TMA: from 0.0564 to 0.0266mm2, p = 0.001, Wilcoxon test). In the effective group, the eyes with normal tear meniscus at 1month were significantly more frequent than those in the ineffective group (p < 0.001, Fisher's exact test). No patient in the effective group required further invasive management during 3years of follow-up. Topical steroid instillation has a significant therapeutic effect on recently developed incomplete NLDO. Additional invasive procedures were avoided in half of the subjects.

Investigation of comet assays under conditions mimicking ocular instillation administration in a three-dimensional reconstructed human corneal epithelial model

Purpose: A comet assay is one of the genotoxicity methods for evaluating the potential of chemicals to induce DNA strand breaks. To investigate the usefulness of comet assays for evaluating the genotoxic potential of ophthalmic solutions, a three-dimensional (3D) reconstructed human corneal epithelial model (3D corneal model) was exposed to conditions mimicking topical ocular instillation administration.Methods: The 3D corneal model was exposed to acridine orange, ethidium bromide, hydrogen peroxide, 1,1′-dimethyl-4,4′-bipyridinium dichloride (paraquat), 4-nitroquinoline 1-oxide (4-NQO), acrylamide and methyl methanesulfonate (MMS). To mimic the ocular surface condition to which ophthalmic solutions are administered, the exposure time was set to 1 minute. Likewise, human corneal epithelial (HCE-T) cells, as monolayer cultured cells, were exposed to the same chemicals, for comparison.Results: In the 3D corneal model, the amount of DNA fragments was statistically significantly increased in cells treated with each of the test chemicals except acrylamide. In HCE-T cells, the amount of DNA fragments was statistically significantly increased in acridine orange-, ethidium bromide-, hydrogen peroxide-, 4-NQO- and MMS-treated cells but not in paraquat- or acrylamide-treated cells. In the 3D corneal model, the lowest concentrations at which we observed DNA damage were about 100 times higher than the concentrations in HCE-T cells. Since the 3D corneal model is morphologically similar to human corneal tissue, form a multilayer and having tight junctions, it may be that the test chemicals only permeated about 1% into the 3D corneal model.Conclusion: These results suggest that the comet assay using 3D cell culture models may reflect in vivo conditions better than do monolayer cultured cells, and that the comet assay may be useful for the evaluation of genotoxic potential of topical ophthalmic solution.

Ocular Drug Delivery: A Special Focus on the Thermosensitive Approach.

The bioavailability of ophthalmic therapeutics is reduced because of the presence of physiological barriers whose primary function is to hinder the entry of exogenous agents, therefore also decreasing the bioavailability of locally administered drugs. Consequently, repeated ocular administrations are required. Hence, the development of drug delivery systems that ensure suitable drug concentration for prolonged times in different ocular tissues is certainly of great importance. This objective can be partially achieved using thermosensitive drug delivery systems that, owing to their ability of changing their state in response to temperature variations, from room to body temperature, may increase drug bioavailability. In the case of topical instillation, in situ forming gels increase pre-corneal drug residence time as a consequence of their enhanced adhesion to the corneal surface. Otherwise, in the case of intraocular and periocular, i.e., subconjunctival, retrobulbar, peribulbar administration, among others, they have the undoubted advantage of being easily injectable and, owing to their sudden thickening at body temperature, have the ability to form an in situ drug reservoir. As a result, the frequency of administration can be reduced, also favoring the patient’s adhesion to therapy. In the main section of this review, we discuss some of the most common treatment options for ocular diseases, with a special focus on posterior segment treatments, and summarize the most recent improvement deriving from thermosensitive drug delivery strategies. Aside from this, an additional section describes the most widespread in vitro models employed to evaluate the functionality of novel ophthalmic drug delivery systems.

Multifunctional Nanocomposites Based on Liposomes and Layered Double Hydroxides Conjugated with Glycylsarcosine for Efficient Topical Drug Delivery to the Posterior Segment of the Eye.

To achieve efficient drug delivery to the posterior segment of the eye via topical instillation, novel multifunctional nanocomposites were prepared by hybridizing dexamethasone disodium phosphate (DEXP)-loaded liposome (LP) glycylsarcosine (GS)-anchored layered double hydroxides (named DEXP-HSPC@LDH-GS) and then fully characterized. The nanocomposites exhibited sustained-release performance as well as prolonged precorneal retention ability. MTT assays showed that the nanocomposites were not cytotoxic to both human corneal epithelial cells (HCEpiC) and human conjunctival epithelial cells (HConEpiC) at an LDH concentration of 100 μg/mL. The DEXP-HSPC@LDH-GS nanocomposites showed superior in vitro permeability on the HConEpiC-cell-based model. In the case of HConEpiC cells, both clathrin-mediated endocytosis and active transport by the peptide transporter-1 (PepT-1) were involved in the internalization of the nanocomposites. Fluorescent images of frozen sections of ocular tissues suggested that the possible route for the delivery of doxorubicin hydrochloride (DOX)-labeled nanocomposites from the ocular surface to the back of the eye was a non-corneal pathway. Furthermore, in rabbit eyes, the hybrid nanocomposites displayed markedly higher drug concentration in choroid-retina tissue than other single nanocarriers, such as LPs and LDH. Besides, the results of the eye irritancy test showed that nanocomposite eye drops can be classified as nonirritant, which are suitable to be used as eye drops. In a word, multifunctional nanocomposites based on LPs and LDH could be used as promising vehicles for efficient noninvasive drug delivery to the posterior segment of the eye.

Implication of Melanopsin and Trigeminal Neural Pathways in Blue Light Photosensitivity in vivo.

Photophobia may arise from various causes and frequently accompanies numerous ocular diseases. In modern highly illuminated world, complaints about greater photosensitivity to blue light increasingly appear. However, the pathophysiology of photophobia is still debated. In the present work, we investigated in vivo the role of various neural pathways potentially implicated in blue-light aversion. Moreover, we studied the light-induced neuroinflammatory processes on the ocular surface and in the trigeminal pathways. Adult male C57BL/6J mice were exposed either to blue (400–500 nm) or to yellow (530–710 nm) LED light (3 h, 6 mW/cm2). Photosensitivity was measured as the time spent in dark or illuminated parts of the cage. Pharmacological treatments were applied: topical instillation of atropine, pilocarpine or oxybuprocaine, intravitreal injection of lidocaine, norepinephrine or “blocker” of the visual photoreceptor transmission, and intraperitoneal injection of a melanopsin antagonist. Clinical evaluations (ocular surface state, corneal mechanical sensitivity and tear quantity) were performed directly after exposure to light and after 3 days of recovery in standard light conditions. Trigeminal ganglia (TGs), brainstems and retinas were dissected out and conditioned for analyses. Mice demonstrated strong aversion to blue but not to yellow light. The only drug that significantly decreased the blue-light aversion was the intraperitoneally injected melanopsin antagonist. After blue-light exposure, dry-eye-related inflammatory signs were observed, notably after 3 days of recovery. In the retina, we observed the increased immunoreactivity for GFAP, ATF3, and Iba1; these data were corroborated by RT-qPCR. Moreover, retinal visual and non-visual photopigments distribution was altered. In the trigeminal pathway, we detected the increased mRNA expression of cFOS and ATF3 as well as alterations in cytokines’ levels. Thus, the wavelength-dependent light aversion was mainly mediated by melanopsin-containing cells, most likely in the retina. Other potential pathways of light reception were also discussed. The phototoxic message was transmitted to the trigeminal system, inducing both inflammation at the ocular surface and stress in the retina. Further investigations of retina-TG connections are needed.

Topical instillation of vancomycin lowers the rate of CSF shunt infections in children.

Shunt surgery in pediatric patients still bears a significant risk of infection, in addition to mechanical complications of the shunt system. Antibiotic-impregnated systems and perioperative antibiotics have been extensively studied for their potential to reduce shunt infections. We examined the effectiveness of intrawound application of vancomycin powder during shunt surgery. Patient records of 78 primary shunt implantations at a mean age of 40months were reviewed. In total, 52 patients (mean age 50months) had been treated according to standard surgical and perioperative procedures (Std), whereas 26 patients (mean age 20months) additionally had received topical application of vancomycin powder before wound closure (Vmc). Overall infection rate was 3.8%, in Std patients 5.8%, and in Vmc patients 0%. The rates of CSF fistula and revision surgery were similar in both groups (5.8% vs 8% and 23.1% vs. 30%, respectively). To the best of our knowledge, this is the first report on topical vancomycin instillation, indicating its efficacy for the prevention of shunt infection in pediatric patients. Further studies with a higher number of patients are needed to verify this finding.

Protective Action of Linear Polyethylenimine against Staphylococcus aureus Colonization and Exaggerated Inflammation in Vitro and in Vivo.

Increased evolution of multidrug resistant pathogens necessitates the development of multifunctional antimicrobials. There is a perceived need for developing new antimicrobials that can interfere with acute inflammation after bacterial infections. Here, we investigated the therapeutic potential of linear polyethylenimine (LPEI) in vitro and in vivo. The minimum inhibitory concentration of LPEI ranged from 8 to 32 μg/mL and elicited rapid bactericidal activity against clinical isolates of meticillin-resistant Staphylococcus aureus (MRSA). The polymer was biocompatible for human cultured ocular and dermal cells. Prophylactic addition of LPEI inhibited the bacterial colonization of human primary dermal fibroblasts (hDFs). In a scratch wound cell migration assay, LPEI attenuated the migration inhibitory effects of bacterial secretions. The polymer neutralized the cytokine release by hDFs exposed to bacterial secretions, possibly by blocking their accessibility to host cell receptors. Topical instillation of LPEI (1 mg/mL) was noncytotoxic and did not affect the re-epithelialization of injured porcine cornea. In a prophylactic in vivo model of S. aureus keratitis, LPEI was superior to gatifloxacin in terms of reducing stimulation of cytokines, corneal edema, and overall severity of the infection. These observations demonstrate therapeutic potential of LPEI for antimicrobial prophylaxis.

Biodegradable Thermosensitive PLGA-PEG-PLGA Polymer for Non-irritating and Sustained Ophthalmic Drug Delivery.

Challenges of ophthalmic drug delivery arise from not only the limited solubility of hydrophobic therapeutics, but also the restricted permeability and fast clearance of drugs due to the complex anatomy and physiology of the eyes. Biodegradable thermosensitive polymer, poly(dl-lactide-co-glycolide-b-ethylene glycol-b-dl-lactide-co-glycolide) (PLGA-PEG-PLGA) is a desirable ophthalmic drug delivery system because it can be formulated into injectable solution which forms gel in situ to provide prolonged drug release. In this study, excellent biocompatibility of blank PLGA-PEG-PLGA (1800-1500-1800) thermogel was demonstrated with insignificant difference from saline noted in rat eye enucleation test, in vivo inflammation test upon topical instillation, and subconjunctival injection. After subconjunctival injection, thermogel formulations loaded with hydrophilic (rhodamine B) or hydrophobic (coumarin 6) fluorescent dyes were retained up to 4weeks in eye tissues and significantly higher level was detected than rhodamine B solution or coumarin 6 suspension in weeks 3 and 4. Moreover, in vivo whole body imaging showed that dye-loaded (sulfo-cyanine 7 NHS ester, Cy7; or cyanine 7.5 alkyne, Cy7.5) thermogels had longer retention at the injection site and retarded release to other body parts than dye solutions. Generally, the release rate of hydrophobic dyes (coumarin 6 and Cy7.5) was much slower than that of the hydrophilic dyes (rhodamine B and Cy7) from the thermogel. In summary, the thermogel was safe for ophthalmic drug delivery and could deliver both hydrophobic and hydrophilic compounds for sustained drug release into eye tissues with single subconjunctival injection for better patient compliance and reduced risks on repeated injection.

Stability, safety, and pharmacokinetics of ganciclovir eye drops prepared from ganciclovir for intravenous infusion.

Hospital-prepared topical ganciclovir eye drops made from intravenous infusions are used to treat cytomegalovirus corneal endotheliitis. This study assessed the efficacy of these eye drops. Experimental study design. Ganciclovir solutions (0.5% and 1.0%) prepared by diluting DENOSINE® IV Infusion in saline were stored light-shielded at 4, 25, or 37°C for 12 weeks. Every two weeks during storage, macroscopic evaluation was conducted and ganciclovir concentrations were determined by high performance liquid chromatography. Ocular surface toxicity and corneal ganciclovir concentrations were evaluated following topical instillation of ganciclovir solutions in rabbits. Ganciclovir solutions maintained transparency for 6 weeks, with precipitation appearing after 8 weeks. Ganciclovir concentrations were maintained at ~100% for 6 weeks at 4°C and 25°C and decreased gradually to 90% after 12 weeks. At 37°C, ganciclovir concentrations decreased linearly for 12 weeks. Rabbit eyes showed no ocular surface toxicity. Following instillation of 0.5% ganciclovir solution, endothelial ganciclovir concentrations were 28.0 µg/g at one hour and 4.3 µg/g at three hours. Ganciclovir eye drops seem to be safe and penetrate the corneal endothelium. The drug in eye drop form is chemically stable for up to 6 weeks. Eye drops' development for approval by regulatory authorities, especially with improved long-term stability, is anticipated.

Topical bromfenac transiently delays axotomy-induced retinal ganglion cell loss

Optic nerve axotomy in rodents allows detailed studies of the effect of different treatments on the survival of central nervous system neurons, the retinal ganglion cells (RGCs). Here we have analyzed the neuroprotective effect of topical bromfenac treatment, a nonsteroidal anti-inflammatory drug (NSAID) used in clinic to ameliorate post-operative inflammation, on axotomized rat RGCs. The left optic nerve of adult rats was subjected to optic nerve crush (ONC). Half of the rats were treated with a topical instillation of saline. On the other half, immediately after the surgery, 2 drops of bromfenac (0.09% Yellox; Bausch & Lomb) were instilled, and then every 12 h until analysis. Retinas in both groups were dissected 3, 5, 7, 9 and 14 days after ONC (n = 4–8/time point/group). Toxicity of bromfenac was assessed in intact retinas treated during 14 days (n = 6). Intact untreated retinas were used as control of the RGC population. RGCs were identified by Brn3a immunodetection and automatically quantified. Our results show that bromfenac does not cause RGC loss in intact retinas. In the injured groups, the number of RGCs at 7, 9 and 14 days after the lesion was significantly higher in treated vs. untreated retinas. To our knowledge this is the first report showing that a topical treatment with a NSAIDs delays axotomy-induced RGC loss and indicates that treatment with NSAIDs could be used as conjunctive therapy in diseases that proceed with optic nerve damage.

The effectiveness of colchicine combined with mitomycin C to prolong bleb function in trabeculectomy in rabbits.

PurposeTo investigate the potential of colchicine to improve bleb function after trabeculectomy.MethodsTo find the maximum usable colchicine concentration, an ocular irritation study was performed with the Draize test at concentrations of 0.001%, 0.01% and 0.1%. Additionally, the synergistic effect of topical colchicine instillation and MMC application to surgical site was evaluated in a rabbit model by measuring changes after trabeculectomy in intraocular pressure (IOP) and bleb morphology score at 3, 7, 14, 21, 28, 35, 42, and 49 days.ResultsExperiments with a rabbit model of trabeculectomy showed that 0.04% MMC plus 0.01% colchicine was more effective than saline and 0.04% MMC alone in maintaining IOP reduction at days 7–49 (P < 0.01 at all time points) and day 49 (P < 0.05), respectively, while 0.04% MMC alone was more effective than saline only at days 7–35 (P < 0.05 at all time points). 0.04% MMC plus 0.01% colchicine and 0.04% MMC alone were more effective than saline at preserving bleb score at days 7–21 and 35–49 (P < 0.05 at all time points) and at days 7–35 (P < 0.05 at all time points), respectively.ConclusionColchicine may be a promising adjuvant for strengthening the effect of MMC and improving the survival of the filtering bleb in trabeculectomy.