Topical Tacrolimus Progylcosomes Nano-Vesicles As a Potential Therapy for Experimental Dry Eye Syndrome.

The present work aimed to evaluate the efficacy of topical tacrolimus (0.01%) loaded propylene glycol (PG) modified nano-vesicles (Proglycosomes Nano-vesicles, PNVs) for the treatment of experimental dry eye syndrome (DES) in rabbits. DES was induced by topical application of atropine (1.0%) and benzalkonium chloride (0.1%) aqueous solution. PNVs treatment (PNV group) was compared with tacrolimus solution 0.01% (TAC group) and untreated group and healthy group were used as controls. PNV treated animals showed improved clinical performance with marked increase in tear production and tear break-up time (TBUT). Further, PNVs also subside ocular inflammation as evident from absence of matrix metalloprotenaise-9 and normal ocular surface temperature (32.3 ± 0.34 °C). Additionally, PNVs have positive effect on ocular and epithelial damage observed through low ocular surface staining score and improved globlet cell density. The PNV treatment was found to more effectively compared to TAC solution and most of the parameters were close to those of healthy animals. In conclusion, tacrolimus PNV formulation (0.01%) could be a potential therapy for treatment of dry eye syndrome.

Formulation development, optimization, and in vitro assessment of thermoresponsive ophthalmic pluronic F127-chitosan in situ tacrolimus gel.

To overcome problems associated with topical delivery of tacrolimus (TCS), a thermoresponsive in situ gel system containing pluronic F127 (PL), and chitosan (CS) was developed, to enhance the precorneal retention, and to sustain the release of the drug. The PL-CS in situ gel was optimized using a 2-factor-3-level central composite experimental design by selecting the concentration of PL and CS as independent variables while gelation time, gelation temperature, and spreadability as dependent variables. The optimized formulation was developed using 22.5 g PL and 0.3 g CS, gels at 33.6 °C, in 22.93 s, and showed the spreadability of 6.2 cm. In vitro studies conducted for the optimized gel revealed the sustained release of TCS (81.73% in 4 h) and improved corneal permeation (74.13% in 4 h), compared with TCS solution. The mechanism of release of TCS followed the Higuchi model with Fickian diffusion transport. Further, histopathology and HET-CAM studies revealed that the developed gel was non-irritating and safe for ocular administration.

Amelioration of Endotoxin-Induced Uveitis in Rabbit by Topical Administration of Tacrolimus Proglycosome Nano-Vesicles.

This work was aimed to improve the efficacy of tacrolimus in the treatment of endotoxin-induced uveitis (EIU) using propylene glycol modified lipid vesicles termed as proglycosome nano-vesicles (PNVs). PNVs were prepared by modified film hydration method. Experimental uveitis in rabbit eye was induced by an intravitreal injection of 20 µL of the endotoxin solution containing 100 ng of lipopolysaccharide endotoxin. In vivo efficacy of PNVs was determined by studying clinical symptoms of uveitis using slit lamp examination and by quantitatively measuring levels of tumor necrosis factor-alpha, interleukin-6, leukocytes and total proteins in aqueous humor, 24 h after intravitreal injection of endotoxin. Comparison was made with healthy, untreated and tacrolimus solution treated eyes. PNVs developed were nano-sized, deformable and showed sustained release of tacrolimus over period of 12 h. In vivo results indicated statistically significant difference between the effects of PNVs in the treatment of EIU compared to tacrolimus. PNV treatment not only subsides clinical symptoms of uveitis but also prevented breakdown of blood aqueous barrier. Tacrolimus loaded PNVs are potential new topical treatment for uveitis.

Proglycosomes: A novel nano-vesicle for ocular delivery of tacrolimus.

Tacrolimus is an emerging candidate for the treatment of immune-mediated inflammatory ocular disorders (IIODs) however its ocular delivery remained a challenge due to its hydrophobic nature, high molecular weight and physiological and anatomical constraints of the eye. The present work describes vesicles composed of propylene glycol, phospholipid and water, proglycosomes (PNVs), as novel carriers for ocular delivery of tacrolimus. Addition of propylene glycol decreases vesicle aggregation, increases encapsulation of tacrolimus and prevented drug leakage. Developed PNVs were of nanosize (111.5±3.2nm) and 5-fold more elastic than conventional liposomes. PNVs showed prolonged drug release over period of 12h and higher corneal permeation, 5-fold and 13-fold, compared to conventional liposomes and tacrolimus solution, respectively. Studies in rabbits demonstrated prolonged precorneal retention (upto 8h) and manifestly improved intraocular drug levels, well above therapeutic levels, at all tested time-points following topical application of PNV formulation compared to drug solution. Further, PNVs were found to be safe for ocular use. In conclusion, the developed PNVs are prospective carriers for enhanced ocular delivery of tacrolimus.

Dorzolamide-loaded PLGA/vitamin E TPGS nanoparticles for glaucoma therapy: Pharmacoscintigraphy study and evaluation of extended ocular hypotensive effect in rabbits.

Poor drug penetration and rapid clearance after topical instillation of a drug formulation into the eyes are the major causes for the lower ocular bioavailability from conventional eye drops. Along with this, poor encapsulation efficiency of hydrophilic drug in polymeric nanoparticles remains a major formulation challenge. Taking this perspective into consideration, dorzolamide (DZ)-loaded PLGA nanoparticles were developed employing two different emulsifiers (PVA and vitamin E TPGS) and the effects of various formulation and process variables on particle size and encapsulation efficiency were assessed. Nanoparticles emulsified with vitamin E TPGS (DZ-T-NPs) were found to possess enhanced drug encapsulation (59.8±6.1%) as compared to those developed with PVA as emulsifier (DZ-P-NPs). Transcorneal permeation study revealed a significant enhancement in permeation (1.8-2.5 fold) as compared to solution. In addition, ex vivo biodistribution study showed a higher concentration of drug in the aqueous humour (1.5-2.3 fold). Histological and IR-camera studies proved the non-irritant potential of the formulations. Pharmacoscintigraphic studies revealed the reduced corneal clearance, as well as naso-lachrymal drainage in comparison to drug solution. Furthermore, efficacy study revealed that DZ-P-NPs and DZ-T-NPs significantly reduced the intraocular pressure by 22.81% and 29.12%, respectively, after a single topical instillation into the eye.

Topical tacrolimus nanoemulsion, a promising therapeutic approach for uveitis.

Uveitis is a sight threatening inflammatory disorder that affects all ages and remains a significant cause of visual loss. Inflammatory activity plays an important role in the whole pathogenesis of uveitis. Treatment of uveitis is mainly driven by corticosteroids that have potential side effects. Recent investigations demonstrated that tacrolimus inhibits T-cell proliferation and suppresses release of inflammatory cytokines. Since tacrolimus is a definite immunosuppressive agent, and since inflammatory process has been involved in uveitis, the compound must have effect on the progression of uveitis through reduction in inflammatory activity. Even results of the clinical trials demonstrate that tacrolimus have useful role in treatment of sight threatening uveitis that is refractory to other therapy. Studies also indicate that long term use of tacrolimus is well tolerated. However, its use in uveitis is limited because of its poor physico-chemical properties including poor aqueous solubility and high molecular weight (822 Da). Therefore, we have proposed that tacrolimus nanoemulsion administered topically is a promising therapeutic approach to treat uveitis. Based on previous evidences, we have hypothesized that nanoemulsion formulation of tacrolimus can improve efficacy and safety profile of tacrolimus.

Therapeutic stratagems for vascular degenerative disorders of the posterior eye.

In this review we discuss insights into therapeutic stratagems that can selectively target the choroid, retinal cells and vitreoretinal space for the treatment of vision-threatening vascular degenerative disorders of the posterior eye. Despite the relative success of these novel drugs, new problems related to its delivery remain. Systems carrying drugs to the target site, such as nanoparticles, liposomes, vectosomes, spanlastics, micelles, dendrimers and implants are also discussed. Further, we also consider drug penetration enhancement approaches along with cutting-edge strategies for regaining vision during vision-threatening vascular degenerative disorders of the eye. Finally, challenges, such as ocular or even systemic complications associated with use of prolonged therapies and future prospects, such as combination of approaches with multidisciplinary integration to optimize delivery to the posterior eye are also addressed.