D. Sakthi Kumar

Toyo University, Tōkyō, Japan

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Publications (66)132.44 Total impact

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    ABSTRACT: The rising consciousness about the benefits of environment friendly and biodegradable materials demand a substitute for the prevailing non-degradable and toxic materials. Towards this aspect bacterial cellulose (BC) has numerous potential applications owing to their vital properties like high biocompatibility, biodegradability, and ecofriendly nature. In the present study, we have synthesized BC using Komagataeibacter sucrofermentans strain through batch fermentation and functionalized it with sulfate groups to form bacterial cellulose sulfate (BCS) that has negligible reports so far. Using this BCS, we have synthesized a highly transparent film by drop casting method, which exhibited high optical transmittance of 90–92% in the visible wavelength range. BCS was thoroughly characterized using SEM and AFM for its surface morphology. The XPS, FTIR, TGA and XRD studies were performed to confirm the successful sulfonation, stability and crystallinity of BC and BCS. The film morphology, surface roughness and mechanical properties were monitored using SEM, AFM, and Instron universal testing machine. The results confirm smooth surface with good integrity and mechanical properties of the BCS film. Furthermore, cell viability studies confirmed the biocompatible nature of the sample. Owing to these salient features, BCS films hold tremendous potential in the field of biomedicine, optoelectronics as well as food packaging.
    Materials Express 10/2014; 4(5).
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    ABSTRACT: A nanoformulation composed of a ribosome inactivating protein-curcin and a hybrid solid lipid nanovector has been devised against glioblastoma. The structurally distinct nanoparticles were highly compatible to human endothelial and neuronal cells. A sturdy drug release from the particles, recorded upto 72 h, was reflected in the time-dependent toxicity. Folate-targeted nanoparticles were specifically internalized by glioma, imparting superior toxicity and curbed an aggressively proliferating in vitro 3D cancer mass in addition to suppressing the anti-apoptotic survivin and cell matrix protein vinculin. Combined with the imaging potential of the encapsulated dye, the nanovector emanates as a multifunctional anti-cancer system.
    Macromolecular Bioscience 09/2014; · 3.74 Impact Factor
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    ABSTRACT: Curcin, a type 1 ribosome inactivating protein (RIP) is investigated here for its cellular competence on six mammalian cell lines. Cells exposed to curcin (100 μg/ml) for 72 h exhibited significant cellular metabolic arrest, with the cancer cell lines being more sensitive. The viability assessment of the cancer cells in a 3D cell culture based assay revealed highly restricted sprouting and proliferation with near to complete dead cell population. Prominent mitochondrial dysfunction, elevated reactive oxygen species levels, nuclear degeneration, structural/mechanical destabilization and suppression of defense mechanisms were imminent with the RIP treated cells. Expression levels of nuclear factor κB (NF-κB), cytoskeletal focal adhesion kinases (FAK) and vinculin were significantly diminished. Vital cellular organelles as nucleus, mitochondria and actin were severely incapacitated on RIP exposure resulting in multimodal apoptosis and necrosis. The ability of curcin to impart comprehensive shutdown of the cells, especially cancer cells, complemented with its hemocompatibility, opens up possibilities of utilizing this ribotoxin as a prospective therapeutic candidate against cancers of diverse origins.
    Scientific Reports 07/2014; · 5.08 Impact Factor
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    ABSTRACT: Extremophiles are the group of organisms that are far overlooked for exploring novel biomaterials in the field of material science and bionanotechnology. Extremophilic bacterial-sulfated exopolysaccharide, mauran (MR), is employed for the bioreduction and passivation of gold nanoparticles (AuNps) to enhance the biocompatibility of AuNps and used for photothermal ablation of cancer cells. Here, various concentrations of MR solution are tested for the reduction of HAuCl4 solution in the presence as well as in the absence of an external reducing agent, to produce mauran-gold nanoparticles (MRAu Nps). These biocompatible nanocomposites are treated with cancer cell lines under in vitro conditions and NIR irradiated for complete ablation. MRAu Nps-treated cancer cells on immediate exposure to infrared radiation from a femtosecond pulse laser of operating wavelength 800 nm are subjected to hyperthermia causing cell death. Biocompatible MR stabilization could fairly reduce the cytotoxicity caused by bare AuNps during biomedical applications. Application of a biocompatible polysaccharide from extremophilic bacterial origin for reduction and passivation of AuNps and used for a biomedical purpose is known to be first of its kind in bionanofusion studies.
    Particle and Particle Systems Characterization 07/2014; · 0.86 Impact Factor
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    ABSTRACT: The nanocrystals, so-called quantum dots (QDs), are undisputedly excellent fluorescent markers for imaging and clinical diagnostics. However, their toxicity is always a perturbing issue and remains as the major hindrance for biocompatible imaging and other biomedical applications. Here, we have demonstrated the extraction and application of an extremophilic bacterial polysaccharide, mauran (MR), from a moderately halophilic bacterium called Halomonas maura in the stabilization of ZnS:Mn2+ QDs for the first time. MR has been employed as a natural polymer for bioconjugation to enhance the cellular acceptance and decrease the cytotoxicity of QDs while being used as a fluorescent marker for imaging purposes. Five nanometer-sized QDs were stabilized using an aqueous MR solution under ambient conditions to yield 10–20 nm-sized nanoparticles. Characterization of MR-QD was performed using UV–vis and fluorescent spectroscopy, TEM, SEM, and FTIR. A cytocompatibility assay revealed that the cellular toxicity of QDs was drastically reduced on MR stabilization. In vitro cellular imaging of mouse fibroblast cells and breast adenocarcinoma cells showed that MR-QDs are equally effective as normal QD imaging without imparting any toxicity issues. Thus, it was shown that extremophilic sulfated bacterial polysaccharide, MR, can be successfully used as a novel stabilizing agent for QDs to reduce toxicity and eventually be used as a safe fluorescent agent for in vitro imaging.
    ACS Sustainable Chemistry & Engineering. 04/2014; 2(7):1551–1558.
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    ABSTRACT: Non-specificity and cardiotoxicity are the primary limitations of current doxorubicin chemotherapy. To minimize side effects and to enhance bioavailability of doxorubicin to cancer cells, dual targeted pH sensitive biocompatible polymeric nanosystem was designed and developed. ATRP based biodegradable triblock copolymer poly(polyethylene glycol methacrylate)-poly(caprolactone)-poly(polyethylene glycol methacrylate) [pPEGMA-PCL-pPEGMA] conjugated with doxorubicin via acid labile hydrazone bond was synthesized and characterized. Dual targeting was achieved by attaching folic acid and AS1411 aptamer through EDC-NHS coupling. Nanoparticles of the functionalized triblock copolymer were prepared using the nanoprecipitation method with an average particle size of ~140 nm. Biocompatibility of the nanoparticles was evaluated using MTT cytotoxicity assay, blood compatibility studies and protein adsorption study. In vitro drug release studies showed higher doxorubicin cumulative release in pH 5.0 (~70%) as compared to that in pH 7.4 (~25%) owing to the presence of acid sensitive hydrazone linkage. Dual targeting with folate and AS1411 aptamer increased the cancer targeting efficiency of nanoparticles resulting in enhanced cellular uptake (10 fold and 100 fold increase in uptake as compared to single targeted NPs and non-targeted NPs respectively) and higher payload of doxorubicin in epithelial cancer cell lines (MCF-7 and PANC-1) with subsequent higher apoptosis, while sparing normal (non-cancerous) cell line (L929) from the adverse effects of doxorubicin. The results indicate that the dual targeted pH sensitive biocompatible polymeric nanosystem can act as a potential drug delivery vehicle against various epithelial cancers like breast, ovarian, pancreas, lung cancer etc.
    Biomacromolecules 04/2014; · 5.37 Impact Factor
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    ABSTRACT: Gliomas have been termed recurrent cancers due to their highly aggressive nature. Their tendency to infiltrate and metastasize has posed significant roadblocks in attaining full proof treatment solutions. An initiative to curb such a scenario was successfully demonstrated in vitro, utilizing a multi-conceptual gold nanoparticle based photo-thermal and drug combination therapy. Gold nanoparticles (Au NPs) were synthesized with a highly environmentally benign process. The Au NPs were PEGylated and conjugated with folate and transferrin antibody to achieve a dual targeted nano-formulation directed towards gliomas. Curcin, a type 1 ribosome inactivating protein, was attached to the Au NPs as the drug candidate, and its multifarious toxic aspects analyzed in vitro. NIR photo-thermal properties of the Au nano-conjugates were studied to selectively ablate the glioma cancer colonies. Highly cyto-compatible, 10-15 nm Au NP conjugates were synthesized with pronounced specificity towards gliomas. Curcin was successfully conjugated to the Au NPs with pH responsive drug release. Prominent toxic aspects of curcin, such as ROS generation, mitochondrial and cytoskeletal destabilization were witnessed. Excellent photo-thermal ablation properties of gold nanoparticles were utilized to completely disrupt the cancer colonies with significant precision. The multifunctional nanoconjugate projects its competence in imparting complete arrest on the future proliferation or migration of the cancer mass. With multifunctionality the essence of nanomedicine in recent years, the present nanoconjugate highlights itself as a viable option for a multimodal treatment option for brain cancers and the like.
    Biochimica et Biophysica Acta 12/2013; · 4.66 Impact Factor
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    ABSTRACT: Mauran (MR), a highly polyanionic sulfated exopolysaccharide was extracted from moderately halophilic bacterium; Halomonas maura and characterized using X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Purified MR was evaluated for antioxidant defense mechanisms under in vitro conditions using L929, mouse fibroblast cell line and mice liver homogenate. It was demonstrated that MR could impart protective effect against oxidative stress in both cells and tissue up to a concentration of 500μg, which is found to be safe under laboratory conditions. Various enzymatic and non-enzymatic parameters of antioxidant mechanisms were evaluated and concluded that MR has the tendency to maintain a balance of antioxidative enzymes with in the test systems studied. Also, hemocompatibility assay performed revealed that MR has a lesser hemolytic index and exhibited a prolonged clotting time, which shows both antihemolytic, and antithrombogenic nature respectively. Furthermore, absorption studies performed using fluorescent-labeled MR confirmed that MR accumulated within the cell cytoplasm neither induced cellular lysis nor affected the cell integrity.
    Carbohydrate polymers. 10/2013; 98(1):108-15.
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    ABSTRACT: Controlled and targeted drug delivery is an essential criterion in cancer therapy to reduce the side effects caused by non-specific drug release and toxicity. Targeted chemotherapy, sustained drug release and optical imaging have been achieved using a multifunctional nanocarrier constructed from poly (D, l-lactide-co-glycolide) nanoparticles (PLGA NPs), an anticancer drug paclitaxel (PTX), a fluorescent dye Nile red (NR), magnetic fluid (MF) and aptamers (Apt, AS1411, anti-nucleolin aptamer). The magnetic fluid and paclitaxel loaded fluorescently labeled PLGA NPs (MF-PTX-NR-PLGA NPs) were synthesized by a single-emulsion technique/solvent evaporation method using a chemical cross linker bis (sulfosuccinimidyl) suberate (BS3) to enable binding of aptamer on to the surface of the nanoparticles. Targeting aptamers were then introduced to the particles through the reaction with the cross linker to target the nucleolin receptors over expressed on the cancer cell surface. Specific binding and uptake of the aptamer conjugated magnetic fluid loaded fluorescently tagged PLGA NPs (Apt-MF-NR-PLGA NPs) to the target cancer cells induced by aptamers was observed using confocal microscopy. Cytotoxicity assay conducted in two cell lines (L929 and MCF-7) confirmed that targeted MCF-7 cancer cells were killed while control cells were unharmed. In addition, aptamer mediated delivery resulting in enhanced binding and uptake to the target cancer cells exhibited increased therapeutic effect of the drug. Moreover, these aptamer conjugated magnetic polymer vehicles apart from actively transporting drugs into specifically targeted tumor regions can also be used to induce hyperthermia or for facilitating magnetic guiding of particles to the tumor regions.
    Journal of Magnetism and Magnetic Materials 10/2013; 344:116–123. · 2.00 Impact Factor
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    ABSTRACT: Fluorinated graphene oxide (FGO) is reported for the first time as a magnetically responsive drug carrier that can serve both as a magnetic resonance imaging (MRI) and photoacoustic contrast agent, under preclinical settings, and as a type of photothermal therapy. Its hydrophilic nature facilitates biocompatibility. FGO as a broad wavelength absorber, with high charge transfer and strong non-linear scattering is optimal for NIR laser-induced hyperthermia.
    Advanced Materials 08/2013; · 14.83 Impact Factor
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    ABSTRACT: Highly conductive biocompatible graphene is synthesized using ecofriendly reduction of graphene oxide (GO). Two strains of non-pathogenic extremophilic bacteria are used for reducing GO under both aerobic and anaerobic conditions. Degree of reduction and quality of bacterially reduced graphene oxide (BRGO) are monitored using UV–vis spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Structural morphology and variation in thickness are characterized using electron microscopy and atomic force microscopy, respectively. Electrical measurements by three-probe method reveal that the conductivity has increased by 104–105 fold from GO to BRGO. Biocompatibility assay using mouse fibroblast cell line shows that BRGO is non-cytotoxic and has a tendency to support as well as enhance the cell growth under laboratory conditions. Hereby, a cost effective, non-toxic bulk reduction of GO to biocompatible graphene for green electronics and bioscience application is achieved using halophilic extremophiles for the first time.
    Particle and Particle Systems Characterization 07/2013; 30(7). · 0.86 Impact Factor
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    ABSTRACT: Extremophilic bacterial polysaccharide based biocompatible nanofibers were produced for the first time via electrospinning technique. Mauran (MR), an extremophilic sulfated exopolysaccharide was extracted from moderately halophilic bacterium, Halomonas maura and characterized for the application of nanofiber synthesis. Thin-uniform MR nanofibers were produced using homogenous solutions of poly (vinyl alcohol) (PVA) blended with different concentrations of MR. Characterization of complex MR/PVA nanofibers were performed using scanning electron microscope and analyzed for the cytotoxicity using mouse fibroblast cells as well as mesenchymal stem cells. An average of 120nm sized nanofibers were produced and tested for an enhanced cell growth under in vitro conditions in comparison with control. MR and MR/PVA nanofibers were found to be an excellent biomaterial for the migration, proliferation and differentiation of mammalian cells, which was confirmed by cell adhesion studies and confocal microcopy. Interestingly, biological and physicochemical properties of MR hasten the application of MR based nanofibers for various biomedical applications like tissue engineering and drug delivery.
    Carbohydrate polymers. 02/2013; 92(2):1225-33.
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    ABSTRACT: Sulfated polysaccharides are complex polysaccharide molecules with excellent physico- chemical properties and bioactivities. On the basis of origin, they are classified as plant, animal, microbial and chemically synthesized sulfated polysaccharides. They have been widely applied in the fields of material and biological sciences. Biocompatibility and biodegradability of these molecules facilitates its increased use in the nanoparticle synthesis and tissue engineering applications. This review focuses on the structure, function and applications of important types of natural and chemically derived sulfated polysaccharides in the fields of nanotechnology and biomedical sciences. In the first part, we discuss about the classification and role of sulfated polysaccharides in various fields. Later, we elaborate the specific bionano applications of commercially important sulfated polysaccharides in ionic gelation, stabilizing, cross- linking, capping and encapsulation of drugs. Finally, we conclude with the future scope and advanced applications of sulfated polysaccharides in various fields of interdisciplinary science.
    Nanomedicine: nanotechnology, biology, and medicine 01/2013; · 6.93 Impact Factor
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    ABSTRACT: Introduction of a novel biocompatible, stable, biomaterial for drug delivery application remains always challenging. In the present study, we report the synthesis of an extremophilic bacterial sulfated polysaccharide based nanoparticle as a stable biocompatible material for drug delivery, evaluation of anticancer efficacy and bioimaging. Mauran (MR), the sulfated exopolysaccharide extracted from a moderately halophilic bacterium, Halomonas maura was used for the synthesis of nanoparticles along with chitosan (CH). MR/CH nanoparticles were synthesized by simple polyelectrolyte complexation of anionic MR and cationic CH. The MR/CH hybrid nanoparticles formed were ranging between 30 and 200nm in diameter with an overall positive zeta potential of 27.5±5mV and was found to be stable under storage in solution for at least 8 weeks. In vitro drug release studies showed a sustained and prolonged delivery of 5-fluorouracil (5FU) for 10-12 days from MR/CH nanoparticles under three different pHs of 4.5, 6.9 and 7.4 respectively. Cytotoxicity assay revealed that MR/CH nanoparticles were non-cytotoxic towards normal cells and toxic to cancer cells. Also, 5FU loaded MR/CH nanoparticles were found more effective than free 5FU in its sustained and controlled manner of killing breast adenocarcinoma cells. Fluorescein isothiocyanate (FITC) labeled MR/CH nanoparticles were used for cell binding and uptake studies; thereby demonstrating the application of dye tagged MR/CH nanoparticles for safe and nontoxic mode of live cellular imaging. We report the introduction of an extremophilic bacterial polysaccharide, MR, for the first time as a novel biocompatible and stable biomaterial to the world of nanotechnology, pharmaceutics and biomedical technology.
    Carbohydrate polymers. 01/2013; 91(1):22-32.
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    ABSTRACT: The photothermal effect of single-walled carbon nanotubes (SWCNTs) in combination with the anticancer drug doxorubicin (DOX) for targeting and accelerated destruction of breast cancer cells is demonstrated in this paper. A targeted drug-delivery system was developed for selective killing of breast cancer cells with polyethylene glycol biofunctionalized and DOX-loaded SWCNTs conjugated with folic acid. In our work, in vitro drug-release studies showed that the drug (DOX) binds at physiological pH (pH 7.4) and is released only at a lower pH, ie, lysosomal pH (pH 4.0), which is the characteristic pH of the tumor environment. A sustained release of DOX from the SWCNTs was observed for a period of 3 days. SWCNTs have strong optical absorbance in the near-infrared (NIR) region. In this special spectral window, biological systems are highly transparent. Our study reports that under laser irradiation at 800 nm, SWCNTs exhibited strong light-heat transfer characteristics. These optical properties of SWCNTs open the way for selective photothermal ablation in cancer therapy. It was also observed that internalization and uptake of folate-conjugated NTs into cancer cells was achieved by a receptor-mediated endocytosis mechanism. Results of the in vitro experiments show that laser was effective in destroying the cancer cells, while sparing the normal cells. When the above laser effect was combined with DOX-conjugated SWCNTs, we found enhanced and accelerated killing of breast cancer cells. Thus, this nanodrug-delivery system, consisting of laser, drug, and SWCNTs, looks to be a promising selective modality with high treatment efficacy and low side effects for cancer therapy.
    International Journal of Nanomedicine 01/2013; 8:2653-67. · 4.20 Impact Factor
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    ABSTRACT: A potential non-destructive harvesting of gold nanoparticles (Au NPs) employing the seed shell and detoxified-defatted seed meal aqueous extracts of Jatropha curcas is reported. The reduction potential of the shell and meal extracts were tested at varied ratios with chloroauric acid under physical parameters of increasing pressure and temperature. The optimal ratio of chloroauric acid to seed meal/shell extracts was determined to be 1:1 under constant shaking in water bath at 60ºC yielding nearly isotropic nanoparticles, which was confirmed by UV-Vis spectroscopy, HRTEM and AFM analysis. With increasing concentrations (1:2, 1:3, 1:4) of reducing agents, temperature (121ºC) and pressure (12 lbs), anisotropy with respect to particle shape and size increased in order. FT-IR, TGA and HRTEM provided evidence of bio-capping of the nanoparticles with biomolecules present in the parent reducing sources. The biocompatibility of these nanoparticles was tested on neuronal HCN-1A and brain cancer glioma Gl-1 cell lines, which revealed their superior cyto-amiability when compared with conventionally synthesized Au NPs. The biodiagnostic and photothermal ablation potential of the Au NPs were also tested and affirmed with the luminescent signals recorded from the cellular cytoplasm indicating the efficient internalization of these nanoparticles as well as the apoptotic events encountered upon irradiating the cells with laser. Nearly 100% of the cells underwent sudden apoptosis within 1 min of laser treatment, providing enough evidence for the thermal ablation potential of the Au NPs. To support the claim of non-destructive harvesting of nanoparticles, the protein and ash content of the seed meal and seed shell, respectively, were analyzed before and after the aqueous extraction. Minimal loss in these inherent characteristic potentials of the seed meal and shell emphasizes the sustainable utilization of bio-resources achieved in this report.
    Nanomaterials and the Environment. 11/2012; 1:3-17.
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    ABSTRACT: The targeting and therapeutic efficacy of dye- and dual-drug-loaded silica nanoparticles, functionalized with triple targeting ligands specific towards cancer and neoangiogenesis simultaneously, are discussed. This synergized, high-precision, multitarget concept culminates in an elevated uptake of nanoparticles by cancer and angiogenic cells with amplified proficiency, thereby imparting superior therapeutic efficacy against breast cancer cells and completely disabling the migration and angiogenic sprouting ability of activated endothelial cells. The exceptional multimodal efficiency achieved by this single therapeutic nanoformulation holds promise for the synergistic targeting and treatment of the yet elusive cancer and its related angiogenesis in a single, lethal shot.
    Small 08/2012; · 7.82 Impact Factor
  • Raju Francis, Deepa K. Baby, D. Sakthi Kumar
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    ABSTRACT: Stimuli-sensitive drug delivery systems (DDSs) have attracted considerable attention in medical and pharmaceutical fields; thermo-sensitive DDS dealing with poly(N-isopropylacrylamide) (PNIPAM) have been widely studied. Hydrogels composed of temperature-sensitive NIPAM and biocompatible and pH-sensitive maleic acid (MAc) were synthesized by sedimentation polymerization. Experiments on drug release from the crosslinked NIPAM-co-MAc hydrogel loaded with ibuprofen into different pH buffer solutions were successfully carried out at temperature swing between 25 and 40°C. The in vitro release studies have showed that the release rate depended on acidity or basicity (polarity) of the medium and the gel and swelling ratio of the gel network as a function of the environmental pH and temperature. The SEM image of the dry bead gave more insight into the surface architecture and the thermal studies shine light on the decomposition pattern and glass transition temperature of the gel. The mechanism of the drug release was discussed in relation to the diffusion rate and the abrupt change in the pH of the medium. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
    Journal of Applied Polymer Science 06/2012; 124(6). · 1.40 Impact Factor
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    Materials Express. 06/2012; 2(2):94-102.
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    Remya Nair, Y. Yoshida, T. Maekawa, D. Sakthi Kumar
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    ABSTRACT: Silica nanoparticles have been prepared from tetraethylorthosilicate dissolved in ethanol followed by base-catalyzed condensation. Earlier works reported that at least four parameters, namely concentration of tetraethylorthosilicate, ethanol, water and ammonia solution are needed to be optimized for the size tuning of silica nanoparticles. In this work size tuning of 5 nm–250 nm has been achieved by varying a single synthesis parameter i.e., the concentration of ammonia solution. Oxygen plasma was found to be successful for generating pores on silica nanoparticles without using any structure directing agents. The properties and morphology of nanoparticles were investigated by transmission electron microscopy, scanning electron microscopy, energy dispersive X- ray spectroscopy and Fourier transformed infrared spectroscopy.
    Progress in Natural Science: Materials International. 06/2012; 22(3):193–200.

Publication Stats

242 Citations
132.44 Total Impact Points

Institutions

  • 2003–2014
    • Toyo University
      • • Bio-Nano Electronics Research Center
      • • Graduate School of Interdisciplinary New Science
      • • Department of Applied Chemistry
      Tōkyō, Japan
  • 2006–2011
    • Cochin University of Science and Technology
      • Department of Physics
      Cochin, Kerala, India