Dileep R. Janagam

Nanoparticles for drug delivery to the anterior segment of the eye

Commercially available ocular drug delivery systems are effective but less efficacious to manage diseases/disorders of the anterior segment of the eye. Recent advances in nanotechnology and molecular biology offer a great opportunity for efficacious ocular drug delivery for the treatments of anterior segment diseases/disorders. Nanoparticles have been designed for preparing eye drops or injectable solutions to surmount ocular obstacles faced after administration. Better drug pharmacokinetics, pharmacodynamics, non-specific toxicity, immunogenicity, and biorecognition can be achieved to improve drug efficacy when drugs are loaded in the nanoparticles. Despite the fact that a number of review articles have been published at various points in the past regarding nanoparticles for drug delivery, there is not a review yet focusing on the development of nanoparticles for ocular drug delivery to the anterior segment of the eye. This review fills in the gap and summarizes the development of nanoparticles as drug carriers for improving the penetration and bioavailability of drugs to the anterior segment of the eye.

Overcoming the Blood-Brain Barrier in Chemotherapy Treatment of Pediatric Brain Tumors

Pediatric brain tumors are most common cancers in childhood and among the leading causes of death in children. Chemotherapy has been used as adjuvant (i.e. after) or neoadjuvant (i.e. before) therapy to surgery and radiotherapy for the management of pediatric brain tumors for more than four decades and gained more attention in the recent two decades. Although chemotherapy has demonstrated its effectiveness in the management of some pediatric brain tumors, failure or inactiveness of chemotherapy is commonly met in the clinics and clinical trials. Some of these failures might be attributed to the blood-brain barrier (BBB), limiting the penetration of systemically administered chemotherapeutics into pediatric brain tumors. Therefore, various strategies have been developed and used to address this issue. Herein, we review different methods reported in the literature to circumvent the BBB for enhancing the present of chemotherapeutics in the brain to treat pediatric brain tumors.

Development and validation of sensitive LC/MS/MS method for quantitative bioanalysis of levonorgestrel in rat plasma and application to pharmacokinetics study

Rapid, sensitive, selective and accurate LC/MS/MS method was developed for quantitative determination of levonorgestrel (LNG) in rat plasma and further validated for specificity, linearity, accuracy, precision, sensitivity, matrix effect, recovery efficiency and stability. Liquid-liquid extraction procedure using hexane:ethyl acetate mixture at 80:20 v:v ratio was employed to efficiently extract LNG from rat plasma. Reversed phase Luna column C18(2) (50×2.0mm i.d., 3μM) installed on a AB SCIEX Triple Quad™ 4500 LC/MS/MS system was used to perform chromatographic separation. LNG was identified within 2min with high specificity. Linear calibration curve was drawn within 0.5-50ng·mL(-1) concentration range. The developed method was validated for intra-day and inter-day accuracy and precision whose values fell in the acceptable limits. Matrix effect was found to be minimal. Recovery efficiency at three quality control (QC) concentrations 0.5 (low), 5 (medium) and 50 (high) ng·mL(-1) was found to be >90%. Stability of LNG at various stages of experiment including storage, extraction and analysis was evaluated using QC samples, and the results showed that LNG was stable at all the conditions. This validated method was successfully used to study the pharmacokinetics of LNG in rats after SubQ injection, providing its applicability in relevant preclinical studies.

An Accelerated Release Study to Evaluate Long-Acting Contraceptive Levonorgestrel-Containing in Situ Forming Depot Systems.

Biodegradable polymer-based injectable in situ forming depot (ISD) systems that solidify in the body to form a solid or semisolid reservoir are becoming increasingly attractive as an injectable dosage form for sustained (months to years) parenteral drug delivery. Evaluation of long-term drug release from the ISD systems during the formulation development is laborious and costly. An accelerated release method that can effectively correlate the months to years of long-term release in a short time such as days or weeks is economically needed. However, no such accelerated ISD system release method has been reported in the literature to date. The objective of the current study was to develop a short-term accelerated in vitro release method for contraceptive levonorgestrel (LNG)-containing ISD systems to screen formulations for more than 3-month contraception after a single subcutaneous injection. The LNG-containing ISD formulations were prepared by using biodegradable poly(lactide-co-glycolide) and polylactic acid polymer and solvent mixtures containing N-methyl-2-pyrrolidone and benzyl benzoate or triethyl citrate. Drug release studies were performed under real-time (long-term) conditions (PBS, pH 7.4, 37 °C) and four accelerated (short-term) conditions: (A) PBS, pH 7.4, 50 °C; (B) 25% ethanol in PBS, pH 7.4, 50 °C; (C) 25% ethanol in PBS, 2% Tween 20, pH 7.4, 50 °C; and (D) 25% ethanol in PBS, 2% Tween 20, pH 9, 50 °C. The LNG release profile, including the release mechanism under the accelerated condition D within two weeks, correlated (r2 ≥ 0.98) well with that under real-time conditions at four months.

Subconjunctivally Implanted Hydrogels for Sustained Insulin Release to Reduce Retinal Cell Apoptosis in Diabetic Rats.

PURPOSE Diabetic retinopathy (DR) is a leading cause of blindness in diabetic patients that involves early-onset retinal cell loss. Here, we report our recent work using subconjunctivally implantable hydrogels for sustained insulin release to the retina to prevent retinal degeneration. METHODS The hydrogels are synthesized by UV photopolymerization of N-isopropylacrylamide and a dextran macromer containing oligolactate-(2-hydroxyetheyl methacrylate) units. Insulin was loaded into the hydrogels during the synthesis. The ex vivo bioactivity of insulin released from the hydrogels was tested on fresh rat retinas using immunoprecipitation and immunoblotting to measure insulin receptor tyrosine and Akt phosphorylation. The biosafety and the effect on the blood glucose of the hydrogels were evaluated in rats 2 months after subconjunctival implantation. The release of insulin from the hydrogels was studied both in vitro in PBS (pH 7.4), and in vivo using confocal microscopy and RIA kit. The in vivo bioactivity of the released insulin was investigated in diabetic rats using DNA fragmentation method. RESULTS The hydrogels could load insulin with approximately 98% encapsulation efficiency and continuously release FITC-insulin in PBS (pH = 7.4) at 37°C for at least 5 months depending on their composition. Insulin lispro released from the hydrogels was biologically active by increasing insulin receptor tyrosine and Akt serine phosphorylation of ex vivo retinas. In vivo studies showed normal retinal histology 2 months post subconjunctival implantation. Insulin released from subconjunctivally implanted hydrogels could be detected in the retina by using confocal microscopy and RIA kit for 1 week. The implanted hydrogels with insulin lispro did not change the blood glucose level of normal and diabetic rats, but significantly reduced the DNA fragmentation of diabetic retinas for 1 week. CONCLUSIONS The developed hydrogels have great potential to sustain release of insulin to the retina via subconjunctival implantation to minimize DR without the risk of hypoglycemia.

Formulation, Development, and In Vitro Evaluation of a CD22 Targeted Liposomal System Containing a Non-Cardiotoxic Anthracycline for B Cell Malignancies

Doxorubicin cardiotoxicity has led to the development of superior chemotherapeutic agents such as AD 198. However, depletion of healthy neutrophils and thrombocytes from AD 198 therapy must be limited. This can be done by the development of a targeted drug delivery system that delivers AD 198 to the malignant cells. The current research highlights the development and in vitro analysis of targeted liposomes containing AD 198. The best lipids were identified and optimized for physicochemical effects on the liposomal system. Physiochemical characteristics such as size, ζ-potential, and dissolution were also studied. Active targeting to CD22 positive cells was achieved by conjugating anti-CD22 Fab’ to the liposomal surface. Size and ζ-potential of the liposomes was between 115 and 145 nm, and −8 to−15 mV. 30% drug was released over 72 h. Higher cytotoxicity was observed in CD22+ve Daudi cells compared to CD22−ve Jurkat cells. The route of uptake was a clathrin- and caveolin-independent pathway. Intracellular localization of the liposomes was in the endolysosomes. Upon drug release, apoptotic pathways were activated partly by the regulation of apoptotic and oncoproteins such as caspase-3 and c-myc. It was observed that the CD22 targeted drug delivery system was more potent and specific compared to other untargeted formulations.

Injectable In Situ Forming Depot Systems for Long-Acting Contraception

Up to date, no long‐acting reversible contraceptive (LARC) is developed to be injectable through needles smaller than 18 G and can also provide contraception for more than 3 months after single injection. In this study, injectable polymeric in situ forming depot (ISD) systems are developed to have injectability through 21–23 G needles, and capability of sustained release of levonorgestrel (LNG) for at least 7 months in vitro and in vivo after single subcutaneous injection in rats. The systems are polymeric solutions composed of biodegradable poly(lactide‐co‐glycolide) and poly(lactic acid) polymers dissolved in a mixture of solvents like N‐methyl‐2‐pyrrolidone and benzyl benzoate or triethyl citrate. LNG released from ISD systems successfully suppressed the estrous cycle of rats at plasma concentration above 0.35 ng mL−1. At the end of the treatment, when LNG plasma concentration drops down to be nondetectable, predictable return of fertility is observed in rats. The designed ISD systems have great potential to be further developed into robust injectable LARCs that can be injected through a 21 G or smaller needle and achieve a variety of contraception durations with high patient compliance and low cost.

Combination Therapy in Glaucoma Treatment

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