The arginase enzyme developed in early life forms and was maintained during evolution. As the last step in the urea cycle, arginase cleaves l-arginine to form urea and l-ornithine. The urea cycle p...

Arginase: A Multifaceted Enzyme Important in Health and Disease.

Amongst the various routes of drug delivery, the field of ocular drug delivery is one of the most interesting and challenging endeavors facing the pharmaceutical scientist. Recent research has focused on the characteristic advantages and limitations of the various drug delivery systems, and further research will be required before the ideal system can be developed. Administration of drugs to the ocular region with conventional delivery systems leads to short contact time of the formulations on the epithelium and fast elimination of drugs. This transient residence time involves poor bioavailability of drugs which can be explained by the tear production, non-productive absorption and impermeability of corneal epithelium. Anatomy of the eye is shortly presented and is connected with ophthalmic delivery and bioavailability of drugs. In the present update on ocular dosage forms, chemical delivery systems such as prodrugs, the use of cyclodextrins to increase solubility of various drugs, the concept of penetration enhancers and other ocular drug delivery systems such as polymeric gels, bioadhesive hydrogels, in-situ forming gels with temperature-, pH-, or osmotically induced gelation, combination of polymers and colloidal systems such as liposomes, niosomes, cubosomes, microemulsions, nanoemulsions and nanoparticles are discussed. Novel ophthalmic delivery systems propose the use of many excipients to increase the viscosity or the bioadhesion of the product. New formulations like gels or colloidal systems have been tested with numerous active substances by in vitro and in vivo studies. Sustained drug release and increase in drug bioavailability have been obtained, offering the promise of innovation in drug delivery systems for ocular administration. Combining different properties of pharmaceutical formulations appears to offer a genuine synergy in bioavailability and sustained release. Promising results are obtained with colloidal systems which present very comfortable conditions of use and prolonged action.

Recent advances in ocular drug delivery

Freeze-drying of emulsified systems: A review.

Background: The purpose of this study was to develop microemulsion-based hydrogel formulation for topical delivery of bifonazole with an objective to increase the solubility and skin permeability of the drug. Materials and Methods: Oleic acid was screened as the oil phase of microemulsions, due to a good solubilizing capacity of the microemulison systems. The pseudo-ternary phase diagrams for microemulsion regions were constructed using oleic acid as the oil, Tween 80 as the surfactant and isopropyl alcohol (IPA) as the cosurfactant. Various microemulsion formulations were prepared and optimized by 3 2 factorial design on the basis of percentage (%) transmittance, globule size, zeta potential, drug release, and skin permeability. The abilities of various microemulsions to deliver bifonazole through the skin were evaluated ex vivo using Franz diffusion cells fitted with rat skins. The Hydroxy Propyl Methyl Cellulose (HPMC) K100 M as a gel matrix was used to construct the microemulsion-based hydrogel for improving the viscosity of microemulsion for topical administration. The optimized microemulsion-based hydrogel was evaluated for viscosity, spreadability, skin irritancy, skin permeability, stability, and antifungal activity by comparing it with marketed bifonazole cream. Results: The mechanism of drug release from microemulsion-based hydrogel was observed to follow zero order kinetics. The studied optimized microemulsion-based hydrogel showed a good stability over the period of 3 months. Average globule size of optimized microemulsion (F5) was found to be 18.98 nm, zeta potential was found to be -5.56 mv, and permeability of drug from microemulsion within 8 h was observed 84%. The antifungal activity of microemulsion-based hydrogel was found to be comparable with marketed cream. Conclusion: The results indicate that the studied microemulsion-based hydrogel (F5) has a potential for sustained action of drug release and it may act as promising vehicle for topical delivery of ibuprofen.

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Formulation and evaluation of microemulsion-based hydrogel for topical delivery.

Electroactive polymers (EAPs) are promising candidate materials for the design of drug delivery technologies, especially in conditions where an "on-off" drug release mechanism is required. To achieve this, EAPs such as polyaniline, polypyrrole, polythiophene, ethylene vinyl acetate, and polyethylene may be blended into responsive hydrogels in conjunction with the desired drug to obtain a patient-controlled drug release system. The "on-off" drug release mechanism can be achieved through the environmental-responsive nature of the interpenetrating hydrogel-EAP complex via (i) charged ions initiated diffusion of drug molecules; (ii) conformational changes that occur during redox switching of EAPs; or (iii) electroerosion. These release mechanisms are not exhaustive and new release mechanisms are still under investigation. Therefore, this review seeks to provide a concise incursion and critical overview of EAPs and responsive hydrogels as a strategy for advanced drug delivery, for example, controlled release of neurotransmitters, sulfosalicyclic acid from cross-linked hydrogel, and vaccine delivery. The review further discusses techniques such as linear sweep voltammetry, cyclic voltammetry, impedance spectroscopy, and chronoamperometry for the determination of the redox capability of EAPs. The future implications of the hydrogel-EAP composites include, but not limited to, application toward biosensors, DNA hybridizations, microsurgical tools, and miniature bioreactors and may be utilized to their full potential in the form of injectable devices as nanorobots or nanobiosensors.

A review of integrating electroactive polymers as responsive systems for specialized drug delivery applications

The concept of wearable products such as textile antenna are being developed which are capable of monitoring, alerting, and demanding attention whenever hospital emergency is needed, hence minimizing labor and resource. In the proposed work using textile material as a substrate, the ultra wideband antenna is designed especially for medical applications. Simulated and measured results here shows that the proposed antenna design meets the requirements of wide working bandwidth and provides 13.08 GHz bandwidth with very small size, washable (if using conductive thread for conductive parts) and flexible materials. Results in terms of bandwidth, radiation pattern, return loss as well as gain and efficiency are presented to validate the usefulness of the current proposed design. The work done here has many implications for future research and it could help patients with such flexible and comfortable medical monitoring techniques. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1553–1557, 2015

Design and performance of wearable ultrawide band textile antenna for medical applications

Treatment effect of l-Norvaline on the sexual performance of male rats with streptozotocin induced diabetes

During the past decades, researchers involved in the development of ophthalmic pharmaceuticals have understood that ophthalmic drug delivery is a challenging subject for optimization. Normal vision is dependent upon the optimal functioning of ocular barriers and intact membranes that function to selectively regulate the environment of ocular tissues. Novel pharmacotherapeutic modalities have aimed to overcome the biological barriers which can impede efficient ocular drug delivery. To explore the impact of ocular barriers on research related to ophthalmic drug delivery and targeting, herein we provide a review of the literature of work carried out on the biological constraints and new approaches to ophthalmic drug delivery.

The challenges of ophthalmic drug delivery: a review

There is an increasing interest in investigating antecedents of employee engagement at workplace. The present article examines the role of psychological empowerment as an antecedent of employee engagement in organizations and simultaneously explored the mediating role of constructive deviance. Data was collected from 233 Indian IT sector employees. A mediation effect was documented through multiple regression analysis suggested by Barron and Kenny. Findings suggest that both psychological empowerment and constructive deviance positively affect employee engagement while constructive deviance acts as significant mediator between them. Theoretical and practical implications of the findings are discussed.

Psychological Empowerment and Employee Engagement: Testing the Mediating Effects of Constructive Deviance in Indian IT Sector

Background: Stimuli-sensitive hydrogels are three-dimensional, hydrophilic, polymeric networks capable of imbibing large amounts of water or biological fluids on stimulation, such as pH, temperature and ionic change. Aim: To develop hydrogels that are sensitive to stimuli, i.e. pH, in the cul-de-sac of the eye for providing a prolonged effect and increased bioavailability with reduction in frequency of administration. Materials and Methods: Hydrogels were formulated by using timolol maleate as the model drug, polyacrylic acid as the gelling agents, hydroxyl ethyl cellulose as the viscolizer and sodium chloride as the isotonic agent. Stirring of ingredients in pH 4 phosphate buffer at high speed was carried out. The dynamic dialysis technique was used for drug release studies. In vivo study for reduction in intraocular pressure was carried out by using albino rabbits. Statistical Analysis: Drug release studies data were used for statistical analysis in first-order plots, Higuchi plots and Peppas exponential plots. Student t-test was performed for in vivo study. Results: Viscosity of the hydrogel increases from 3.84 cps to 9.54 cps due to change in pH 4 to pH 7.4. The slope value of the Peppas equation was found to be 0.3081, 0.3743 and 0.2964. Up to 80% of drug was released in an 8 h drug release study. Sterile hydrogels with no ocular irritation were obtained. Conclusions: Hydrogels show increase in viscosity due to change in pH. Hydrogels were therapeutically effacious, stable, non-irritant and showed Fickian diffusion. In vivo results clearly show a prolonged reduction in intraocular pressure, which was helpful for reduction in the frequency of administration.

Vinod Kumar Singh

Papers

Design and performance of wearable ultrawide band textile antenna for medical applications

Treatment effect of l-Norvaline on the sexual performance of male rats with streptozotocin induced diabetes

The challenges of ophthalmic drug delivery: a review

Psychological Empowerment and Employee Engagement: Testing the Mediating Effects of Constructive Deviance in Indian IT Sector

Stimuli-sensitive hydrogels: a novel ophthalmic drug delivery system.