Tapan Kumar Pal

Improvement of cellular uptake, in vitro antitumor activity and sustained release profile with increased bioavailability from a nanoemulsion platform

Paclitaxel, a potential anticancer agent against solid tumors has been restricted from its oral use due to poor water solubility as well as Pgp efflux property. The present study was aimed to improve the oral bioavailability of paclitaxel through development of (o/w) nanoemulsion consisting of Capryol 90 as internal phase with Tween 20 as emulsifier with water as an external phase. Formulations were selected from the nanoemulsion region of pseudo-ternary phase diagrams, formulated by aqueous titration method. The developed nanoemulsion has been characterized by its thermodynamic stability, morphology, droplet size, zeta potential, viscosity where in vitro release was evaluated through dialysis. Paclitaxel nanoemulsion exhibited thermodynamical stability with low viscosity, nano-sized oil droplets in water with low poly-dispersity index. The shelf life of the paclitaxel nanoemulsion was found to be approximately 2.38 years. Increased permeability through the Caco-2 cell monolayer and decreased efflux is great advantageous for nanoemulsion formulation. The effects of paclitaxel nanoemulsion on breast cancer cell proliferation, morphology and DNA fragmentation were analyzed in vitro which showed significant anti-proliferation and decreased IC50 values in nanoemulsion group which may be due to enhanced uptake of paclitaxel through the oil core. Moreover, the absolute oral bioavailability and sustained release profile of the paclitaxel nanoemulsion evaluated in mouse model was found to improve up to 55.9%. The concentration of paclitaxel in mice plasma was determined by our validated LC-MS/MS method. By reviewing the significant outcome of the present investigation based on stability study, Caco-2 permeability, cell proliferative assay and pharmacokinetic profile it may be concluded that the oral nanoemulsion has got encouraging advantages over the presently available formulations of this injectable chemotherapeutic drug.

Simultaneous determination of metoprolol succinate and amlodipine besylate in human plasma by liquid chromatography-tandem mass spectrometry method and its application in bioequivalence study

A simple, sensitive and specific liquid chromatography-tandem mass spectrometry method was developed and validated for quantification of metoprolol succinate (MPS) and amlodipine besylate (AM) using hydrochlorothiazide (HCTZ) as IS in human plasma. Both the drugs were extracted by simple liquid-liquid extraction with chloroform. The chromatographic separation was performed on a reversed-phase peerless basic C18 column with a mobile phase of methanol-water containing 0.5% formic acid (8:2, v/v). The protonated analyte was quantitated in positive ionization by multiple reaction monitoring with a mass spectrometer. The method was validated over the concentration range of 1-100 ng/ml for MPS and 1-15 ng/ml AM in human plasma. The MRM transition of m/z 268.10-103.10, m/z 409.10-334.20 and m/z 296.00-205.10 were used to measure MPS, AM and HCTZ (IS), respectively. This method was successfully applied to the pharmacokinetic study of fixed dose combination (FDC) of MPS and AM formulation product after an oral administration to Indian healthy human volunteers.

Poly(styrene-co-maleic acid)-based pH-sensitive liposomes mediate cytosolic delivery of drugs for enhanced cancer chemotherapy.

pH-responsive polymers render liposomes pH-sensitive and facilitate the intracellular release of encapsulated payload by fusing with endovascular membranes under mildly acidic conditions found inside cellular endosomes. The present study reports the use of high-molecular weight poly(styrene-co-maleic acid) (SMA), which exhibits conformational transition from a charged extended structure to an uncharged globule below its pK(1) value, to confer pH-sensitive property to liposomes. The changes in the co-polymer chain conformation resulted in destabilization of the liposomes at mildly acidic pH due to vesicle fusion and/or channel formation within the membrane bilayer, and ultimately led to the release of the encapsulated cargo. The vesicles preserved their pH-sensitivity and stability in serum unlike other polymer-based liposomes and exhibited no hemolytic activity at physiological pH. The lysis of RBCs at endosomal pH due to SMA-based liposome-induced alterations in the bilayer organization leading to spherocyte formation indicated the potential of these vesicles to mediate cytosolic delivery of bio-active molecules through endosome destabilization. The SMA-loaded liposomes exhibiting excellent cytocompatibility, efficiently delivered chemotherapeutic agent 5-Fluorouracil (5-FU) within colon cancer cells HT-29 in comparison to neat liposomes. This caused increased cellular-availability of the drug, which resulted in enhanced apoptosis and highlighted the clinical potential of SMA-based vesicles.

Nanoemulsion strategy for olmesartan medoxomil improves oral absorption and extended antihypertensive activity in hypertensive rats.

Olmesartan medoxomil (OM) is hydrolyzed to its active metabolite olmesartan by the action of aryl esterase to exert its antihypertensive actions by selectively blocking angiotensin II-AT1 receptor. Poor aqueous solubility and uncontrolled enzymatic conversion of OM to its poorly permeable olmesartan limits its oral bioavailability. The aim of the current study was to formulate a novel nanoemulsion of OM to improve its pharmacokinetics and therapeutic efficacy. The oil-in-water (o/w) nanoemulsion of OM was developed using lipoid purified soybean oil 700, sefsol 218 and solutol HS 15. We have characterized the nanoemulsions by considering their thermodynamic stability, morphology, droplet size, zeta potential and viscosity and in vitro drug release characteristics in fasting state simulated gastric fluid (pH 1.2) and intestinal fluid (pH 6.5). The thermodynamically stable nanoemulsions comprises of spherical nanometer sized droplets (<50 nm) with low polydispersity index showed enhanced permeability through the Caco-2 cell monolayer. The concentration of active olmesartan in rat plasma following oral absorption study was determined by our validated LC-MS/MS method. The result of the pharmacokinetic study showed 2.8-fold increased in area under the curve (AUC0-27) of olmesartan upon oral administration of OM nanoemulsion and sustained release profile. Subsequent, in vivo studies with nanoemulsion demonstrated better and prolonged control of experimentally induced hypertension with 3-fold reduction in conventional dose. By analysing the findings of the present investigations based on stability study, Caco-2 permeability, pharmacokinetic profile and pharmacodynamic evaluation indicated that the nanoemulsion of OM (OMF6) could significantly enhance the oral bioavailability of relatively insoluble OM contributing to improved clinical application.

Preparation, Characterization, and Biodistribution of Letrozole Loaded PLGA Nanoparticles in Ehrlich Ascites Tumor Bearing Mice

Letrozole (LTZ) incorporated PLGA nanoparticles were prepared by solvent displacement technique and characterized by transmission electron microscopy, poly-dispersity index and zeta potential measurement. Radiolabeling of free LTZ and LTZ-loaded PLGA NPs was performed with technetium-99m with high labeling efficiency. The labeled complex showed good in vitro stability as verified by DTPA challenge test. The labeled complexes also showed significant in vivo stability when incubated in rat serum for 24 h. Biodistribution studies of (99m)Tc-labeled complexes were performed after intravenous administration in normal mice and Ehrlich Ascites tumor bearing mice. Compared to free LTZ, LTZ-loaded PLGA NPs exhibited significantly lower uptake by the organs of RES. The tumor concentration of LTZ-loaded PLGA NPs was 4.65 times higher than that of free LTZ at 4 h post-injection. This study indicates the capability of PLGA nanopartcles in enhancing the tumor uptake of letrozole.

Studies on Separation Characteristics of Hexavalent Chromium from Aqueous Solution by Fly Ash

Abstract Hexavalent chromium has been separated from an aqueous solution by fly ash. The particle size distribution and physical properties of fly ash have been illustrated. It is observed that the percent removal of Cr6 + by fly ash is affected by its concentration in aqueous solution, temperature, particle size, and pH. Better separation is obtained at acidic pH and at higher temperature. Particle size has a nonsignificant effect on separation. The reaction kinetics of separation follows first-order kinetics more satisfactorily at higher temperature.

Determination of gemifloxacin in different tissues of rat after oral dosing of gemifloxacin mesylate by LC–MS/MS and its application in drug tissue distribution study

A simple, sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated to evaluate the accumulation of gemifloxacin in different tissues of Wister albino rat. The analytical method consists of the homogenization of tissues followed by simple liquid-liquid extraction and determination of gemifloxacin by an LC-MS/MS. The analyte was separated on a Peerless basic C(18) column (33 mm x 4.6 mm, 3 microm) with an isocratic mobile phase of methanol-water containing formic acid (1.0%, v/v) (9:1, v/v) at a flow rate of 0.6 ml/min. The MS/MS detection was carried out by monitoring the fragmentation of m/z 390.100-->372.100 for gemifloxacin and m/z 332.100-->314.200 for ciprofloxacin (internal standard; IS) on a triple quadrupole mass spectrometer. The validated method was accurate, precise and rugged with good linearity in all tissue homogenates. The accuracy and precision value obtained from six different sets of quality control samples of all tissues and serum analyzed in separate occasions within 91.833-102.283% and 0.897-5.291%, respectively. The method has been successfully applied to tissue distribution studies of gemifloxacin. The present study demonstrates that the highest tissue concentration of gemifloxacin was obtained in lung (11.891 ng/g), followed by liver (10.110 ng/g), kidney (10.095 ng/g), heart (4.251 ng/g), testis (3.750 ng/g), stomach (3.182 ng/g), adipose tissue (1.116 ng/g) and brain (0.982 ng/ml) in 3h after multiple oral dosing of 200mg gemifloxacin mesylate for 7 days. This method may also be used for gemifloxacin tissue distribution modeling study in rat tissues and antibiotic residue analyses in other animal tissues.

Formulation and In Vitro Studies of a Fixed-Dose Combination of a Bilayer Matrix Tablet Containing Metformin HCl as Sustained Release and Glipizide as Immediate Release

The emerging new fixed dose combination of metformin hydrocholride (HCl) as sustained release and glipizide as immediate release were formulated as a bilayer matrix tablet using hydroxy propyl methyl cellulose (HPMC) as the matrix-forming polymer, and the tablets were evaluated via in vitro studies. Three different grades of HPMC (HPMC K 4M, HPMC K 15M, and HPMC K 100M) were used. All tablet formulations yielded quality matrix preparations with satisfactory tableting properties. In vitro release studies were carried out at a phosphate buffer of pH 6.8 with 0.75% sodium lauryl sulphate w/v using the apparatus I (basket) as described in the . The release kinetics of metformin were evaluated using the regression coefficient analysis. There was no significant difference in drug release for different viscosity grade of HPMC with the same concentration. Tablet thus formulated provided sustained release of metformin HCl over a period of 8 hours and glipizide as immediate release.

Chromatography-tandem mass spectrometry method for the simultaneous quantitation of metoprolol succinate and simvastatin in human plasma.

The liquid chromatographic-tandem mass spectrometry method was developed for the accurate quantitation of metoprolol succinate (MET) and simvastatin (SIM) in human plasma which were obtained from the pharmacokinetic (PK) study. The sample purification and pre-concentration was performed by protein precipitation technique using propranolol hydrochloride as working internal standard (WIS). The chromatographic separation was achieved using an isocratic mobile phase consisting of a mixture of acetonitrile and 0.5% formic acid (90:10 (v/v), pH 3.5) flowing through C18 column at a flow rate of 0.2ml/min. Electro spray ionization (ESI) with multiple reaction monitoring (MRM) was used to acquire mass spectra. Ions were monitored in positive mode and the mass transitions measured were m/z 268.1-->m/z 103.2, m/z 441.3-->m/z 325.1 and m/z 260.0-->m/z 129.5 for MET, SIM and WIS, respectively. An extensive pre-study method validation was carried out in accordance with USFDA guidelines. The linearity for the calibration curve in the concentration range of 1.0-500.0 and 0.1-20ng/ml for MET and SIM, respectively and the lower limits of quantitations (LLOQ) were 1.0 and 0.1ng/ml for MET and SIM, respectively. The method was successfully applied to a PK study on fixed dose combination (FDC) tablet containing MET and SIM in healthy human subjects.

Influence of Heat Input on Martensite Formation and Impact Property of Ferritic-Austenitic Dissimilar Weld Metals

The effect of heat input on martensite formation and impact properties of gas metal arc welded modified ferritic stainless steel (409M) sheets (as received) with thickness of 4 mm was described in detail in this work. The welded joints were prepared under three heat input conditions, i.e. 0.4, 0.5 and 0.6 kJ/mm using two different austenitic filler wires (308L and 316L) and shielding gas composition of Ar + 5% CO2. The welded joints were evaluated by microstructure and charpy impact toughness. The dependence of weld metal microstructure on heat input and filler wires were determined by dilution calculation, Creq/Nieq ratio, stacking fault energy (SFE), optical microscopy (OM) and transmission electron microscopy (TEM). It was observed that the microstructure as well as impact property of weld metal was significantly affected by the heat input and filler wire. Weld metals prepared by high heat input exhibited higher amount of martensite laths and toughness compared with those prepared by medium and low heat inputs, which was true for both the filler wires. Furthermore, 308L weld metals in general provided higher amount of martensite laths and toughness than 316L weld metals.