LC-MS/MS method for simultaneous quantification of dexamethasone and tobramycin in rabbit ocular biofluids.

The complexity of Tobradex® ointment formulation (dexamethasone 0.1 wt% and tobramycin 0.3 wt%) and the high cost of pharmacokinetic (PK) studies in human aqueous humor may prevent generic drug companies from moving forward with a Tobradex®-equivalent product development. The in vitro drug release test would be an alternative approach for differentiating the generic formulations containing both dexamethasone (DEX) and tobramycin (TOB), and the results should be correlated with the in vivo ocular PK studies for further evaluation. To facilitate the in vivo ocular PK studies, a sensitive, rapid and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method that can simultaneously quantify both DEX and TOB in rabbit ocular matrices including tear, aqueous humor and cornea was established and validated. The lower limit of quantification (LLOQ) was 1.5 ng/ml for DEX and 3 ng/ml for TOB with good precision and accuracy. Both intra- and inter-batch precisions were within ±15%, and the accuracy for all QCs was within the range of 85-115%. This new method was successfully applied for a pilot pharmacokinetic analysis of DEX and TOB in rabbit tears after topical administration of Tobradex® ointment.

Comparative Assessment of Active Targeted Redox Sensitive Polymersomes Based on pPEGMA-S-S-PLA Diblock Copolymer with Marketed Nanoformulation.

In the present work, polymersomes based on self-assembled, folate-targeted, redox-responsive, ATRP-based amphiphilic diblock copolymer poly(polyethylene glycol)-S-S-polylactide with disulfide linkage were developed for efficient doxorubicin (DOX) delivery and compared with marketed DOXIL nanoformulation. The polymersomes formulation was optimized by quality by design approach providing monodisperse nanostructures of ∼110 nm and enhanced DOX loading of ∼20%. Polymersomes showed excellent stability as per the ICH guidelines over the extended storage period of 3 months. The in vitro drug release profile confirmed the redox sensitive behavior of polymersomes providing ∼80% drug release in endosomal pH 5 with 10 mmol GSH as compared to ∼20% release at pH 7.4. The targeted polymersomes achieved enhanced cellular internalization in folate receptor overexpressing cell lines, MDA-MB-231 and HeLa, providing ∼24% higher tumor reduction than DOXIL in Ehrlich ascites tumor bearing Swiss albino mice.

ATRP Fabricated and Short Chain Polyethylenimine Grafted Redox Sensitive Polymeric Nanoparticles for Codelivery of Anticancer Drug and siRNA in Cancer Therapy.

To overcome the limitations of conventional chemotherapy, nanoparticle-mediated combinatorial delivery of siRNA and drugs represents a new approach to overcome its associated side effects. Designing safe and efficient vehicles for their codelivery has emerged as a potential challenge in the clinical translation of these formulations. Herein, we have demonstrated a novel "two-in-one" polyplex nanosystem developed from redox sensitive, short chain polyethylenimine modified poly[(poly(ethylene)glycol methacrylate]-s-s-polycaprolactone copolymer synthesized by atom-transfer free-radical polymerization (ATRP), which can deliver doxorubicin and polo-like kinase I (plk1) siRNA, simultaneously for an enhanced chemotherapeutic effect. The nanoparticles were found to be stable at physiological buffer with and without fetal bovine serum (FBS). The developed polymeric nanosystem was found to be biocompatible and hemocompatible in vitro and in vivo at repeated dose administrations. The polymer could easily self-assemble into ∼100 nm spherical nanoparticles with enhanced doxorubicin loading (∼18%) and effective siRNA complexation at a polymer to siRNA weight ratio of 15. The doxorubicin loaded nanoparticles exhibited ∼4-fold higher drug release in endosomal pH (pH 5) containing 10 mmol of GSH compared to pH 7.4, depicting their redox-sensitive behavior. The polyplexes were capable of delivering both cargos simultaneously to cancer cells in vitro as observed by their excellent colocalization in the cytoplasm of MDA-MB-231 and HeLa cells using confocal laser microscopy. Moreover, in vitro transfection of the cells with polyplexes exhibited 50-70% knockdown of plk1-mRNA expression in both cell lines. In vivo administration of the drug loaded polyplexes to EAT tumor bearing (EAT, Ehrlich ascites tumor) Swiss albino mice showed a ∼29-fold decrease in percent tumor volume in comparison to the control group. The results highlight the therapeutic potential of the polyplexes as a combined delivery of doxorubicin and plk1-siRNA in cancer therapy.