Browsing by Author "Sreenivasan, K."
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Item A sensitive estimation of residual ethylene glycol in ethylene oxide sterilized medical devices by HPLC with electrospray ionization mass spectrometric detection(JOURNAL OF CHROMATOGRAPHY B-ANALYTICAL TECHNOLOGIES IN THE BIOMEDICAL AND LIFE SCIENCES, 2009)A novel analytical methodology for the estimation of residual ethylene glycol (EG) in ethylene oxide sterilized polymer is reported. The method involves the monitoring of ammonium adduct of EG ions in the presence of 10 mM ammonium acetate buffer and methanol using electrospray ionization liquid chromatography and mass spectrometry (LC-ESI-MS). The method enables the detection and quantification of EG without prior derivatization up to a level of 0.06 mu g/ml. The potentiality of the method is demonstrated by estimating EG in ethylene oxide (EtO) sterilized polyethylene terephthalate fabric used in heart valve sewing ring. The method is simple, rapid and can routinely be used for the quantification of residual EG in EtO sterilized medical devices. (c) 2008 Elsevier B.V. All rights reserved.Item Bioinspired mineralization and cell adhesion on surface functionalized poly(vinyl alcohol) films(ACTA BIOMATERIALIA, 2009)Poly(vinyl alcohol) (PVA) films, when surface functionalized by phosphorylation, induced biomimetic nucleation and growth of calcium phosphate in a simulated physiological environment. The surface phosphorylation on PVA was ensured by attenuated total reflectance infrared spectroscopy. The morphology of the calcium phosphate phase grown on surface-phosphorylated PVA (PPVA) was analysed using scanning electron microscopy coupled with an energy-dispersive X-ray detector. The primary nucleation of calcium phosphate occurs in 3 days and secondary nucleation occurs after 10 days. The energy-dispersive X-ray analysis shows that the Ca/P ratio of the coating increases with time of exposure to the simulated physiological fluid and reaches 1.67 at 10 days. The PPVA supports in vitro cell adhesion and promotes in vitro biomineralization in the presence of cells, evaluated using human osteosarcoma cells. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.Item Conjugation of curcumin onto hyaluronic acid enhances its aqueous solubility and stability(JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2011)Polymer-drug conjugates have gained much attention largely to circumvent lower drug solubility and to enhance drug stability. Curcumin is widely known for its medicinal properties including its anticancer efficacy. One of the serious drawbacks of curcumin is its poor water solubility which leads to reduced bio-availability. With a view to address these issues, we synthesized hyaluronic acid-curcumin (HA-Cur) conjugate. The drug conjugate was characterized using FT-IR, NMR, Dynamic light scattering and TEM techniques. The conjugates, interestingly found to assembles as micelles in aqueous phase. The formation of micelles seems to improve the stability of the drug in phisiological pH. We also assessed cytotoxicty of the conjugate using L929 fibroblast cells and quantified by MTT assay. (c) 2011 Elsevier Inc. All rights reserved.Item Detection of cholesterol by digitonin conjugated gold nanoparticles(BIOSENSORS & BIOELECTRONICS, 2011)Functionalized colloidal gold is widely used for qualitative and quantitative detection of specific analytes. We report here a novel modification of gold nanoparticles by digitonin, a glycoside used for precipitating membrane cholesterol. The specific molecular recognition of cholesterol by digitonin gold nanoparticles (DGNP), make it an attractive alternative to the existing enzymatic methods for cholesterol sensing. To enable cholesterol binding, we modified mercapto modified GNPs with digitonin, by a simple esterification reaction. The blue shift in the plasmon absorption spectra of DGNP with different cholesterol concentrations accompanied by a decrease in the absorbance is the principle applied here for the estimation. The observed size reduction followed by cholesterol binding is reasoned due to the enhanced hydophobicity of the surface which in turn expels the water layers associated with the particles prior to cholesterol binding. The method exhibited linearity between concentration of cholesterol and the corresponding absorbance of the plasmon peak, in the range of 160-600 ng/mL with a detection limit of 100 +/- 9 ng/mL. Other steroids did not show any binding affinity towards DGNP. The method depicted here has potential for development as an enzyme free sensor for cholesterol although many factors need to be addressed to transform it for assaying samples like blood. (C) 2011 Elsevier B.V. All rights reserved.Item Detection of creatinine enriched on a surface imprinted polystyrene film using FT-ATR-IR(JOURNAL OF MOLECULAR RECOGNITION, 2006)The surface of polystyrene (PS) was chemically modified by coating a thin layer of polyaniline (PANI) by oxidizing aniline using ammonium persulfate. Affinity sites for creatinine, a clinically relevant molecule, were created in the coated layer by adding creatinine as print molecules during the oxidation. The imprinted layer adsorbed creatinine was compared to non-imprinted surface reflecting the creation of creatinine-specific sites on the surface. The equilibrium was attained rapidly, indicating that a material of this kind is suitable for sensing applications. The adsorbed creatinine on the surface was detected using the technique of Fourier transform attenuated total internal reflection infra red spectroscopy (FT-ATR-IR). The results show that molecularly imprinted surface can enrich molecules of interest and the enriched molecules can be detected using FT-IR. Copyright (c) 2006 John Wiley & Sons, Ltd.Item Enhanced Drug Loading on Magnetic Nanoparticles by Layer-by-Layer Assembly Using Drug Conjugates: Blood Compatibility Evaluation and Targeted Drug Delivery in Cancer Cells(LANGMUIR, 2011)Drug targeting using magnetic nanoparticles (MNPs) under the action of an external magnetic field constitutes an important mode of drug delivery. Low cargo capacity, particularly in hydrophobic drugs, is one limitation shown by MNPs. This article describes a simple strategy to enhance the drug-loading capacity of MNPs. The approach was to use polymer-drug conjugates to modify MNPs by layer-by-layer assembly (LbL). Curcumin (CUR) has shown remarkably high cytotoxicity toward various cancer cell lines. However, the drug shows low anticancer activity in vivo because of its reduced systemic bioavailability acquired from its poor aqueous solubility and instability. To address this issue, we synthesized cationic and anionic CUR conjugates by anchoring CUR onto poly(vinylpyrroidone) (PVP-Cur) and onto hyaluronic acid (HA-Cur). We used these oppositely charged conjugates to modify MNPs by layer-by-layer (LbL) assembly. Six double layers of curcumin conjugates were constructed on positively charged amino-terminated magnetic nanoparticles, TMSPEDA@MNPs. Finally, HA was coated onto the outer surface to form HA (HA-Cur/PVP-Cur)(6)@MNPs. Cellular viability studies showed the dose-dependent antiproliferative effect of HA (HA-Cur/PVP-Cur)(6)@MNPs in two cancer cell lines (glioma cells and Caco-2 cells). HA (HA-Cur/PVP-Cur)(6)@MNPs exhibited more cytotoxicity than did free curcumin, which was attributed to the enhanced solubility along with better absorption via hyaluronic acid receptor-mediated endocytosis. Flow cytometry showed enhanced intake of the modified MNPs by cells. Confocal microscope images also confirmed the uptake of HA (HA-Cur/PVP-Cur)(6)@MNPs with greater efficacy. Thus, the strategy that we adopted here appears to have substantial potential in carrying enhanced payloads of hydrophobic drugs to specified targets.Item Fluorescent and superparamagnetic hybrid quantum clusters for magnetic separation and imaging of cancer cells from blood(NANOSCALE, 2011)We demonstrate here the generation of fluorescent superparamagnetic quantum clusters through a greener aqueous route by fusing highly fluorescent gold clusters with superparamagnetic nanoparticles. We conjugated transferrin onto the hybrid clusters to get cell accessibility and assessed their hemocompatibility and cytotoxicity. The ability of the clusters to selectively remove cancer cell lines (C6 glioma cells) from fluids including blood and the fluorescent imaging of the separated cells is demonstrated. The pattering of the clusters in response to an external magnetic field is also shown. Efficient cancer cell separation, imaging and magnetic pattering can be realized by the highly hemocompatible and noncytotoxic hybrid clusters reported here. It seems the probe has potential for further exploration in multimodal imaging of circulating cancer cells.Item Fluorescent gold clusters as nanosensors for copper ions in live cells(ANALYST, 2011)This paper reports the use of fluorescent gold nanoclusters synthesized using bovine serum albumin (Au-BSA) for the sensing of copper ions in live cells. The fluorescence of the clusters was found to be quenched by Cu(2+) enabling its detection in cells. The selectivity of the nanosensor was demonstrated in the presence of several cations excluding Hg(2+). We did not study the effect of Hg(2+) since it was reported earlier. The present study suggests that Cu(2+) induced fluorescence quenching is due to its binding to BSA rather than the fluorescence quenching by metal-metal interaction as in the case of Hg(2+). The Au-BSA showed excellent selectivity to Cu(2+) at various pH conditions. The 'turn off' of fluorescence can be retrieved by a Cu(2+) chelator glycine. Our results showed that gold clusters can be used as a 'turn off' sensor for copper and a 'turn on' sensor for glycine. Under the experimental conditions, the probe showed a response for Cu(2+) over a range of 100 mu M to 5 mM with a detection limit of 50 mu M. The role of Cu(2+) in the misfolding and disassembly of Prion Protein (PrP) leading to various maladies is well ascertained. The methodology we reported here seems to be useful in supplementing other techniques in predicting disease conditions involving Cu(2+).Item Fluorescent molecularly imprinted polymer film binds glucose with a concomitant changes in fluorescence(BIOSENSORS & BIOELECTRONICS, 2010)A fluorescent molecularly imprinted polymeric formulation capable of picking up glucose from aqueous media is reported. The fluorescence intensity of the polymer film was found to reduce proportionally with the concentration of glucose facilitating its use as a glucose sensing element. We used commercially available tear fluid to demonstrate the ability of the film to recognize glucose among other sugar molecules. Fluorescence was measured after equilibrating the film in tear fluid in the presence of a mixture of different sugars. We observed a reduction in fluorescence intensity due to the nonspecific binding of the sugars. The intensity remains the same even if we added additional quantities of the sugars. Interestingly, the fluorescence intensity of the film was found to decrease proportionally when varied concentrations of glucose was added indicating the ability of the film to recognize and bind glucose from a mixture of other sugars. Detectable changes in fluorescence intensity were observed with a concentration of 10 mu g/mL of glucose. The results show that the polymer film could be used for detecting glucose in aqueous fluids such as tear. (C) 2010 Elsevier B.V. All rights reserved.Item Gold nanoparticles generated and stabilized by water soluble curcumin-polymer conjugate: Blood compatibility evaluation and targeted drug delivery onto cancer cells(JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2012)Curcumin (Cur) shows low anticancer activity in vivo due to its reduced systemic bioavailability stemmed from its poor aqueous solubility and instability. Suitably functionalized nanocarriers designed to empty the drug specifically at tumor sites can potentially enhance the antitumor activity of Cur. We devised a simple method for the fabrication of water soluble Cur conjugated gold nanoparticles to target various cancer cell lines. Cur was conjugated to hyaluronic acid (HA) to get a water soluble conjugate (HA-Cur). We generated gold nanoparticles (AuNPs) by reducing chloroauric acid using HA-Cur, which played the dual role of a reducing and stabilizing agent and subsequently anchored folate conjugated PEG. These entities were probed using different analytical techniques, assayed the blood compatibility and cytotoxicity. Their interaction with cancer cell lines (HeLa cells, glyoma cells and Caco 2 cells) was followed by flow cytometry and confocal microscopy. Blood-materials interactions studies showed that the nanoparticles are highly hemocompatible. Flow cytometry and confocal microscopy results showed significant cellular uptake and internalization of the particles by cells. HA-Cur@AuNPs exhibited more cytotoxicity comparing to free Cur. The strategy, we adopted here, resulted the formation blood compatible Cur conjugated AuNPs with enhanced targeting and improved efficacy. (C) 2011 Elsevier Inc. All rights reserved.Item Gold nanoparticles generated through "green route'' bind Hg2+ with a concomitant blue shift in plasmon absorption peak(ANALYST, 2011)We discuss here a quick, simple, economic and ecofriendly method through a completely green route for the selective detection of Hg2+ in aqueous samples. Here we exploited the ability of chitosan to generate gold nanoparticles and subsequently to act as a stabilizer for the formed nanoparticles. When chitosan stabilized gold nanoparticles (CH-Au NPs) are interacted with Hg2+ a blue shift for its localized surface plasmon resonance absorbance (LSPR) band is observed. The blue shift is reasoned to be due to the formation of a thin layer of mercury over gold. A concentration as low as 0.01 ppm to a maximum of 100 ppm Hg2+ can be detected based on this blue shift of the CH-Au NPs. While all other reported methods demand complex reaction steps and costly chemicals, the method we reported here is a simple, rapid and selective approach for the detection of Hg2+. Our results also show that the CH-Au NPs have excellent selectivity to Hg2+ over common cations namely, Pb2+, Cd2+, Mn2+, Fe2+, Ag1+, Ce4+, Ni2+, and Cu2+.Item Hollow microcapsules built by layer by layer assembly for the encapsulation and sustained release of curcumin(COLLOIDS AND SURFACES B-BIOINTERFACES, 2011)Hollow microcapsules fabricated by layer-by-layer assembly (LbL) using oppositely charged polyelectrolytes have figured in studies towards the design of novel drug delivery systems. The possibility of loading a fair amount of active component of poor aqueous solubility is one of the encouraging factors on the wide spread interest of this emerging technology. Curcumin has potent anti-cancer properties. Clinical application of this efficacious agent in cancer and other diseases has been limited due to poor aqueous solubility and consequently minimal systemic bioavailability. LbL constructed polyelectrolyte microcapsules based drug delivery systems have the potential for dispersing hydrophobic agent like curcumin in aqueous media. Here we report the preparation of LbL assembled microcapsules composed of poly(sodium 4-styrene sulfonic acid) and poly(ethylene imine) one after another. The microcapsules were characterized using various analytical techniques. Curcumin was encapsulated in these microcapsules and the efficacy of the released curcumin was studied using L929 cells. (C) 2010 Elsevier B.V. All rights reserved.Item Identification of salicylic acid using surface modified polyurethane film using an imprinted layer of polyaniline(ANALYTICA CHIMICA ACTA, 2007)The surface of polyurethane (PU) was modified by coating a thin layer of polyaniline (PAN) by oxidizing aniline using ammonium persulfate. Affinity sites for salicylic acid (SA) were created in the coated layer by non-covalent imprinting method. The imprinted layer adsorbed SA five times more compared to the nonimprinted surface reflecting the creation of affinity sites specific to SA on the surface. The equilibrium was attained relatively faster indicating that a material of this kind is suitable for sensing applications. The selectivity in recognizing the print molecule by the imprinted surface was assessed by comparing the extent of uptake of other structurally resembling molecules namely O-amino benzoic acid and acetyl salicylic acid. The selectivity factor was found to be 22 and 16.5. The adsorbed SA was detected using the technique of Fourier transform attenuated total internal reflection infrared spectroscopy (FT-ATR-IR). The results show that molecularly imprinted surface in combination with FT-IR is a useful approach for the sensing applications. (c) 2006 Elsevier B.V. All rights reserved.Item Intelligent Thermoresponsive Substrate from Modified Overhead Projection Sheet as a Tool for Construction and Support of Cell Sheets In Vitro(TISSUE ENGINEERING PART C-METHODS, 2011)Cell sheet engineering using thermoresponsive culture dishes allows harvesting of intact in vitro cell sheet. In this study, commercially available polyethylene terephthalate-based overhead projection transparency sheet (OHPS) was identified as a substrate for coating thermoresponsive poly(N-isopropylacrylamide-co-glycidylmethacrylate) (NGMA) copolymer having lower critical solution temperature of 28 degrees C. Since OHPS is highly hydrophobic and rigid, the surface was modified by alkali treatment (OHPS-M) to functionalize the surface with carboxyl and hydroxyl groups so as to make it more suitable for efficient coating of NGMA copolymer and cell culture. To impart thermoresponsiveness, OHPS-M was coated with NGMA (OHPS-MC). Surface morphology, surface chemistry, and thermoresponsive coating were analyzed by profilometry, scanning electron microscopy, water contact angle, and Fourier transform infrared spectroscopy. The cytotoxicity, cell adhesion, and proliferation on OHPS-M and OHPS-MC were analyzed using L929 cells. Specific cytocompatibility analysis was done using SIRC (Rabbit corneal) cells. Data revealed cytocompatible nature of OHPS-M and OHPS-MC. Suitability of OHPS-MC for cell sheet harvest and transfer efficiency was assessed using primary corneal cells. Corneal cell sheet constructs retrieved by temperature variation was characterized by reverse transcriptase polymerase chain reaction for markers specific to differentiated corneal cells (keratin 3 and keratin 12) and proliferating cell nuclear antigen, and assessed for viability using fluorescein diacetate staining, tissue architecture by scanning electron microscopy, and cell-cell contacts by connexin-43 staining. The retrieved cell sheets retained corneal epithelial characteristics such as keratin 3/12, viability, and tissue architecture with intact cell-cell contacts as in native tissue. The results proved that surface modification and coating with NGMA on OHPS offer a novel biocompatible thermosensitive cell culture substrate for generating cell sheet constructs. In addition, OHPS-M can also serve as an efficient carrier tool for retrieved cell sheet.Item Selective detection and estimation of C-reactive protein in serum using surface-functionalized gold nano-particles(ANALYTICA CHIMICA ACTA, 2010)A new method for the detection of C-reactive protein (CRP) in serum using functionalized gold nano-particles (GNP) is reported. The affinity towards CRP is imparted to GNP by tethering O-phosphorylethanolamine (PEA) onto their surface. GNP and modified GNP were characterized using TEM, particle size analysis, zeta potential measurements, absorption spectroscopy and FT-IR techniques. The event of binding of CRP onto the PEA-GNP is followed by visibly observable colour change. We observed a red shift as well as a decrease in absorption in the plasmon peak of the modified GNP with the concentration of CRP. When the concentration of CRP exceeded 450 ng mL(-1), particles were aggregated and the solution became turbid. The method exhibited a linear range for CRP from 50 to 450 ng mL(-1) with a detection limit of 50 ng mL(-1). The colour change and the variation in absorption of the GNP were highly specific to CRP even in the presence of albumin. We estimated CRP in blood serum collected from patients and the results obtained compared well with the estimation using the technique of nephelometry based on the antibody-antigen interaction. (C) 2010 Elsevier B.V. All rights reserved.Item Synthesis and Characterization of a Cytotoxic Cationic Polyvinylpyrrolidone-Curcumin Conjugate(JOURNAL OF PHARMACEUTICAL SCIENCES, 2011)Curcumin has been studied as a potential drug for many diseases including cancer. One of the serious limitations projected on curcumin is its poor water solubility and the substantially low bioavailability. With a view to enhance the aqueous solubility of curcumin, we synthesized polyvinylpyrrolidone curcumin conjugates. Polyvinylpyrrolidone was used for the conjugation considering its long history of safe usage as a biomaterial for various medical applications. The drug conjugates self-assembled in aqueous solution to form nanosized micellar aggregates. The formation of micellae stabilized curcumin against hydrolytic degradation. Another interesting feature of the conjugate was its cationic nature. The net zeta potential in the pH range from 3 to 7.4 was +25 to +20 mV, reflecting the potential stability of the conjugate micellae at physiological pH. We quantified cytotoxic potential of the conjugate by the MTT assay, using L929 fibroblast cells. The results showed that the conjugate had higher cytotoxicity than that of the free curcumin. It is expected that the relative enhanced cytotoxicities are the result of enhanced aqueous solubility and polymer-mediated drug internalization. The conjugate has the potential to circumvent limitations of curcumin and thereby to extrapolate further its applications as an effective anticancer drug. (C) 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 100:504-511, 2011Item The release kinetics of drug eluting stents containing sirolimus as coated drug: Role of release media(JOURNAL OF CHROMATOGRAPHY B-ANALYTICAL TECHNOLOGIES IN THE BIOMEDICAL AND LIFE SCIENCES, 2010)Prior understanding on the in vitro release profile of the drug from drug eluting devices such as stent (DES) is crucial in designing and optimizing the drug embedded coating or matrices. In fact, assessing in vitro release profile is a mandatory requirement prior to the clinical evaluation of DES. The in vitro release is also employed to estimate parameters such as T1/2. The release profile largely depends on the release medium selected for the studies. Normally PBS with a pH of 7.4 is used for assessing the release kinetics of the drug. Often drug undergoes irreversible changes such as hydrolysis in PBS leading to erroneous assessment of the release profile. This is particularly true in the case of sirolimus, one of the widely used drugs in various applications. We studied the influence of various media on the release profile of sirolimus from DES. The data generated Suggested that a release medium consisting of 9:1 (v/v) of normal saline and isopropanol is a most suitable one for assessing in vitro the release kinetics of sirolimus from DES. (C) 2010 Elsevier B.V. All rights reserved.Item Use of chemically modified thermoresponsive copolymers for the detection of C-reactive protein(ANALYTICA CHIMICA ACTA, 2007)Fluorescence intensity of N-isopropylacrylamide-glycidyl methacrylate (NIPAAm-GMA) copolymer conjugated with fluoreseinamine isomer1 was found to decrease considerably in the presence of NIPAAm-GMA copolymer containing O-phosphorylethanolamine (PEA), the specific ligand of C-reactive protein (CRP). The decrease in the emission intensity was reasoned due to the quenching of the fluorescence through the interaction of the polymer chains. The emission intensity was, however, found to increase rapidly when CRP was added in to the solution containing the polymers. The intensity of fluorescence emission was increased by five-fold in the presence of CRP as low as 20 ng mL(-1). Albumin, the major blood protein, did not show any interference in the emission. The presence of a low molecular protein, cytochrome c, on the fluorescence spectra was also studied and this protein also found not have any influence in binding of CRP onto the ligand indicating that other proteins irrespective of their molecular weights did not influence the measurement. A definite correlation was found between the concentration of CRP and the fluorescence intensity. The method appears to be very sensitive and easy to perform. The study reflects, for the first time, the scope of using copolymeric combinations for the measurement of CRP without the use of antibody. (C) 2007 Elsevier B.V. All rights reserved.