Sachin S. Salunkhe

High-Throughput Screening (HTS) is an approach to drug discovery that has gained widespread popularity over the last two decades and has become a standard method for drug discovery in the pharmaceutical industry. Progress from traditional one-compound-at-a time approach, low throughput screening to high throughput screening involving fully automated robotic systems, enables testing of large numbers of compounds daily for different activities in miscellaneous areas of biology. HTS reveals screening of more than 100,000 samples per day. Compared to traditional drug screening methods, HTS is characterized by its simplicity, rapidness, low cost, and high efficiency. Identification of good hits using HTS can minimize the time span of drug discovery noticeably. However, synthetic chemistry for lead optimization and the low throughput of secondary assays for defining the crucial pharmacological properties of active compounds, limits the overall rate of identification of candidate molecules for clinical evaluation. Coupling of compound library with wide chemical diversity along with HTS shows massive drug discovery potential, but to be successful screening technique it depends on several factors. These include the number and quality of validated targets, the number and diversity of compounds in the collections, and the ability to screen these in a timely and cost effective manner using robust informative assays. In this review we have discussed the types of HTS assays, assay miniaturization automation and different detection techniques like fluorescence resonance energy transfer (FRET), fluorescence polarization (FP), homogeneous time resolved fluorescence (HTRF) etc.

A liposome is a microscopic vesicle consisting of an aqueous core enclosed in one or more phospholipid layers, used to convey vaccines, drugs, enzymes, or other substances to target cells or organs. Liposomes are bilayered structures made of amphipathic (both hydrophobic and hydrophilic) phospholipids/cholesterol that spontaneously form closed structures when hydrated in aqueous solutions. Liposomes are acceptable and superior carriers having ability to encapsulate hydrophilic and lipophilic drugs and protect them from degradation. Topical liposomes have similarity to biological membranes they can store water-soluble and lipophilic substances in their different phases. Moreover, they are similar to the epidermis with respect to their lipid composition, which enables them to penetrate the epidermal barrier to a greater extent compared to other dosage forms. According to studies performed so far liposomes are biodegradable and non-toxic. The really new aspect with liposomes is that they are thought to act not only as drug transporters but also drug localizers. Thus vehicles can transport drugs to the wanted site of action within the skin by preventing systemic absorption and consecutively unwanted effects. The liposomal semisolid formulations could perform therapeutically better effects than the conventional formulations, as prolonged and controlled release topical dosage forms, which may lead to improved efficiency and better patient compliance. Such review giving an emphasis on topically applied liposomal formulations which encompasses methods of preparation, evaluation, mechanisms for enhancement in drug delivery through the skin and regulatory requirements necessitates as topical dosage form.