Animikh Ray

A comprehensive insight on ocular pharmacokinetics.

The eye is a distinctive organ with protective anatomy and physiology. Several pharmacokinetics compartment models of ocular drug delivery have been developed for describing the absorption, distribution, and elimination of ocular drugs in the eye. Determining pharmacokinetics parameters in ocular tissues is a major challenge because of the complex anatomy and dynamic physiological barrier of the eye. In this review, pharmacokinetics of these compartments exploring different drugs, delivery systems, and routes of administration is discussed including factors affecting intraocular bioavailability. Factors such as precorneal fluid drainage, drug binding to tear proteins, systemic drug absorption, corneal factors, melanin binding, and drug metabolism render ocular delivery challenging and are elaborated in this manuscript. Several compartment models are discussed; these are developed in ocular drug delivery to study the pharmacokinetics parameters. There are several transporters present in both anterior and posterior segments of the eye which play a significant role in ocular pharmacokinetics and are summarized briefly. Moreover, several ocular pharmacokinetics animal models and relevant studies are reviewed and discussed in addition to the pharmacokinetics of various ocular formulations.

Nanotechnology in Intracellular Trafficking, Imaging, and Delivery of Therapeutic Agents

Abstract Drug delivery to intracellular compartment is gaining importance as a field of investigation. Many important drugs for various diseases have intracellular organelle as site of action. The anticancer drug doxorubicin acts in the nucleus. Hence it is necessary to design delivery strategies such that the drug will reach its targeted site of action, which often times is located inside the cell. However, there are many challenges to design therapeutic strategies for successful intracellular delivery. Factors such as lysosomal degradation and size restriction to organelle entry are some of the issues that need to be addressed. Design of nanostructures and targeting ligands are few of the effective strategies adopted to meet those challenges. However, to design a better therapeutic platform it is necessary to monitor the pathway undertaken by these nanostructures once they cross the plasma membrane. The technology that allows such monitoring has been discussed in this review. It is also necessary to know the endosomal pathway undertaken by these nanostructures after they enter the intracellular environment. These pathways and their role in drug delivery platforms such as nanoparticles and other nanostructures have been explored in this review.

Doxorubicin prodrug for cytoplasmic and nuclear delivery in breast cancer cells

Purpose: The objective of this study was to develop a novel peptide prodrug of doxorubicin which can evade over-expressed efflux pumps in breast cancer cells. This approach may lead to increased uptake and higher drug accumulation in nuclei of cancer cells. Materials and Methods: L-val-L-val doxorubicin prodrug was synthesized following standard f-moc chemistry. The prodrug was analyzed for stability, cellular and nuclear uptake and interaction with efflux and peptide transporters. Breast cancer cells (T47D) were grown on polystyrene 12-well plates. Result: The prodrug Val-Val-doxorubicin was found to be very stable in breast cancer cell homogenate. It was able to evade efflux pumps. The prodrug penetrated cytoplasm and nucleus of cancer cells by interacting with peptide transporters.These transporters (pepT1 and pepT2) are expressed both on plasma and nuclear membrane of breast cancer cells. Uptake of prodrug was found to be 10 times more than parent drug. Conclusion: Peptide prodrug derivatization of doxorubicin has potential to evade efflux pumps and increase availability and nuclear accumulation of doxorubcin in breast cancer cells.

Recent Patents on Nanoparticles and Nanoformulations for Cancer Therapy.

Cancer is a major malignancy which has claimed numerous lives worldwide. Despite huge resources being utilized to develop cancer therapeutics, no effective cure has been found so far. Hence there is a need to look at emerging technologies for a solution. Nanoparticle is one such technology that has become feasible and popular in the past few years. Though, it has not emerged as a drug delivery platform of choice for cancer therapeutics it has shown enormous promise. Different types of materials such as polymer, lipid, magnet, metal based nanoparticles have been developed to enhance the effectiveness of current treatment. This manuscript will review different aspects of nanoparticles and recent research advances and patents for treatment of cancer.

Uptake and bioconversion of stereoisomeric dipeptide prodrugs of ganciclovir by nanoparticulate carriers in corneal epithelial cells

Abstract Purpose: The objective of this study is to investigate cellular uptake of prodrug-loaded nanoparticle (NP). Another objective is to study bioconversion of stereoisomeric dipeptide prodrugs of ganciclovir (GCV) including L-Val-L-Val-GCV (LLGCV), L-Val-D-Val-GCV (LDGCV) and d-Val-l-Val-GCV (DLGCV) in human corneal epithelial cell (HCEC) model. Methods: Poly(D,L-lactic-co-glycolic acid) (PLGA) NP encapsulating prodrugs of GCV were formulated under a double emulsion method. Fluorescein isothiocyanate isomer–PLGA conjugates were synthesized to fabricate biocompatible fluorescent PLGA NP. Intracellular uptake of FITC-labeled NP was visualized by a fluorescent microscope in HCEC cells. Results: Fluorescent PLGA NP and non-fluorescent NP display similar hydrodynamic diameter in the range of 115–145 nm with a narrow particle size distribution and zeta potentials around −13 mV. Both NP types showed identical intracellular accumulation in HCEC cells. Maximum uptake (around 60%) was noted at 3 h for NP. Cellular uptake and intracellular accumulation of prodrugs are significantly different among three stereoisomeric dipeptide prodrugs. The microscopic images show that NPs are avidly internalized by HCEC cells and distributed throughout the cytoplasm instead of being localized on the cell surface. Following cellular uptake, prodrugs released from NP gradually bioreversed into parent drug GCV. LLGCV showed the highest degradation rate, followed by LDGCV and DLGCV. Conclusion: LLGCV, LDGCV and DLGCV released from NP exhibited superior uptake and bioreversion in corneal cells.

Modification of adenoviral nuclear localization signal for efficient drug delivery in retinoblastoma

Results: Uptake of [14C] AA was observed to be sodium, chloride, temperature, pH and energy dependent in both cell lines. [14C] AA uptake was found to be saturable, with Km values of 46.14±6.03 and 47.26±3.24 μM and Vmax values of 17.34±0.58 and 31.86±0.56 pmol/min/mg protein, across HCEC and D407 cells, respectively. The process is inhibited bystructural analogs (LAA and D-Iso AA) but not by structurally unrelated substrates (glucose and PAHA). Ca++/calmodulin and protein kinase C (PKC) pathways play an important role in modulating uptake of AA. A 626bp band corresponding to a vitamin C transporter (SVCT2) has been identified by RT-PCR analysis in both the cell lines.Purpose: Recurrent intravitreal injections are obligatory to maintain therapeutic levels at choroid and retina for wet-MAD treatment. Several drug administrations to retina may result in possible impediments such as retinal hemorrhage, retinal detachment, endophthalmitis, and patient nonconformity. The objective of this research is to synthesize and assess pentablock (PB) copolymers for the precise and non-aggressive delivery of macromolecules in the treatment of posterior segment diseases of the eye.R (RB) is a vision threatening intraocular malignancy. Though chemoreduction has been effective in the early stages of Rb, it is not very effective against extensive and recurrent Rb tumors having vitreal and retinal seeds. There is an urgent need to design a novel targeted drug delivery system. Nuclear localization signal (NLS) can facilitate cargo entry across nuclear membrane. However NLS has limited application in drug delivery due to lack of specificity towards cancer cells. Moreover NLS sequences have not been optimized for selective nuclear transport. Hence this project aims to develop an optimum NLS which would carry cargo selectively to cancer .cells while not affecting normal cells. This optimized NLS will be later conjugated to nanoparticles for efficient drug delivery Synthesis of NLS Peptides-Modified NLSs have been synthesized by solid phase synthesis following general protocol for Fmoc chemistry. The peptide sequences have been purified by preparative HPLC. Structure of peptide and purity have been confirmed by LC/MS. Conjugation to Gold NanoparticlesGold nanoparticle has been conjugated to peptides following a published protocol with some modifications (Wang et al pubmed ID:22051699). Uptake of conjugated nanoparticle in y-79 and D407Uptake studies were performed to determine efficacy of the peptides to transport nanoparticles. Analysis was done with confocal and transmission electron microscopy. It was observed that modified NLSs were able to transport nanoparticles across the nuclear membrane selectively in the cancer cells while not affecting normal cells. Modification of Nuclear Localization Signal might be a novel approach for development of targeted therapeutics.Introduction: Hypoxia mediated signalingcauses a number of vascular retinal diseases. Their treatmentsremain challenging. To date, the effect of hypoxia onexpression of drug transporters (efflux and influx) in retinal cells has not been studied. Therefore, we have investigated molecular and functional expression of membrane transporters in human retinal pigmented epithelial (RPE) cells cultured under normoxic and hypoxic conditions.

Characterization of ocular transporters

Abstract: This chapter describes various techniques for the characterization of ocular transporters. Transporters are membrane-bound proteins that can be broadly classified as efflux and influx transporters. They play a crucial role in determination of drug bioavailability. Discussed in this review are various methods to analyze their structural, functional and kinetic properties. Also included are various in vitro and in vivo models that help us to understand these proteins. The readers are also directed to peruse the references cited to gain better understanding of this exciting field of research.

Transporters and receptors in the posterior segment of the eye

Abstract: The eye requires nutrients, ions and vitamins for its survival but the diffusion of polar molecules across the lipid bilayer is very limited. As a consequence, essential carrier proteins (transporters) are evolved for permeation of anions, cations, vitamins, sugars, nucleosides, amino acids, peptides, etc. To protect the eye from xenobiotics and metabolites, efflux transporters are developed to reduce their intracellular accumulation. Ocular tissues possess many transporter/receptors that are required for their appropriate functioning. Various specialized cell membrane transporter and receptor proteins regulate the exchange of solutes into and out of intraocular chambers. These proteins aid in maintaining the visual function, regulate intraocular pressure, supply nutrients and protect ocular tissues from xenobiotics. Moreover, these transporters and receptors play a role in drug absorption, distribution and elimination as well as in drug-drug interactions. In this chapter we describe the various transporters and receptors identified on anterior ocular tissues (cornea, conjunctiva, iris-ciliary body and lens) and their role in drug adsorption, distribution, metabolism and elimination. Also, this chapter describes the various ions and solute transport processes in the eye. We have tried to update readers with the current strategies of using these transporters and receptors to deliver drugs into the cell. This strategy helps to target and to deliver drugs at therapeutic level into the cells thereby avoiding/minimizing drug-induced toxic effects. The discussion also includes recently identified different multidrug resistance proteins or drug efflux pumps such as permeability glycoprotein, multidrug resistance protein and breast cancer resistance protein in anterior ocular tissues. The active participation of efflux pumps in reducing intracellular xenobiotic levels is described.