Arunava Goswami

Luminescent S-doped carbon dots: an emergent architecture for multimodal applications

A facile route has been developed to synthesise and isolate sulphur doped fluorescent carbon dots for the first time. Such carbogenic quantum dots exhibit a wide band gap of 4.43 eV with a high open circuit voltage (VOC) of 617 mV along with a fill factor (FF) as high as 37%, using phenyl-C60-butyric acid methyl ester (PCBM) as the electron transporting layer. Besides the wide band gap, which is useful in the fabrication of solar cells, sulphur modified carbon dots also exhibit a high fluorescence quantum yield of 11.8% without any additional surface passivation, producing a unique fluorescent probe for further applications. In addition, the particles have a strong tendency to interact with the surface of gold nanoparticles and produce a thin fluorescent layer over their surfaces. Moreover, as they are completely biocompatible in nature, the highly fluorescent S-doped carbon dots have a strong potential for use in bioimaging applications. Interestingly, owing to the presence of oxygen and sulphur functionality, the highly negatively charged particles can easily bind with positively charged DNA-PEI complexes, simply by mixing them, and after interaction with DNA, bright blue fluorescence has been observed under an excitation wavelength of 405 nm .

Mechanical Downsizing of a Gadolinium(III)-based Metal-Organic Framework for Anticancer Drug Delivery

A Gd(III) -based porous metal-organic framework (MOF), Gd-pDBI, has been synthesized using fluorescent linker pDBI (pDBI=(1,4-bis(5-carboxy-1H-benzimidazole-2-yl)benzene)), resulting in a three-dimensional interpenetrated structure with a one-dimensional open channel (1.9×1.2 nm) filled with hydrogen-bonded water assemblies. Gd-pDBI exhibits high thermal stability, porosity, excellent water stability, along with organic-solvent and mild acid and base stability with retention of crystallinity. Gd-pDBI was transformed to the nanoscale regime (ca. 140 nm) by mechanical grinding to yield MG-Gd-pDBI with excellent water dispersibility (>90 min), maintaining its porosity and crystallinity. In vitro and in vivo studies on MG-Gd-pDBI revealed its low blood toxicity and highest drug loading (12 wt %) of anticancer drug doxorubicin in MOFs reported to date with pH-responsive cancer-cell-specific drug release.

Tuning of photoluminescence on different surface functionalized carbon quantum dots

A simple microwave assisted route has been formulated to synthesise various surface functionalized carbogenic quantum dots from biodegradable polysaccharides. The photoluminescence (PL) properties of such surface functional carbon quantum dots (CQDs) have been tuned by the in situ addition of high boiling organic solvents during the synthesis of CQDs under microwave irradiation. Several divalent cations have also been added to investigate the variation of PL intensity after cationic modifications. Some straightforward mechanistic approaches have been predicted to rationalize the enhancement or quenching of the fluorescence by the introduction of organic and inorganic substrates.

Rapid microwave synthesis of fluorescent hydrophobic carbon dots

Fluorescent hydrophobic carbon dots (HCDs) have been fabricated from a poloxamer by a simple microwave assisted process within a few minutes for the first time. Small and distinct spherical HCDs emitted bright blue and green fluorescent light depending upon the excitation wavelength and were dispersed easily in a wide variety of organic solvents. HCDs exhibited excellent water resistant behavior with a contact angle of ∼122° enforcing good hydrophobic character which will be quite useful in potential surface applications.

Photochemical Modulation of Biosafe Manganese Nanoparticles on Vigna radiata: A Detailed Molecular, Biochemical, and Biophysical Study

Manganese (Mn) is an essential element for plants which intervenes mainly in photosynthesis. In this study we establish that manganese nanoparticles (MnNP) work as a better micronutrient than commercially available manganese salt, MnSO4 (MS) at recommended doses on leguminous plant mung bean (Vigna radiata) under laboratory condition. At higher doses it does not impart toxicity to the plant unlike MS. MnNP-treated chloroplasts show greater photophosphorylation, oxygen evolution with respect to control and MS-treated chloroplasts as determined by biophysical and biochemical techniques. Water splitting by an oxygen evolving complex is enhanced by MnNP in isolated chloroplast as confirmed by polarographic and spectroscopic techniques. Enhanced activity of the CP43 protein of a photosystem II (PS II) Mn4Ca complex influenced better phosphorylation in the electron transport chain in the case of MnNP-treated chloroplast, which is evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and corresponding Western blot analysis. To the best of our knowledge this is the first report to augment photosynthesis using MnNP and its detailed correlation with different molecular, biochemical and biophysical parameters of photosynthetic pathways. At effective dosage, MnNP is found to be biosafe both in plant and animal model systems. Therefore MnNP would be a novel potential nanomodulator of photochemistry in the agricultural sector.

Room temperature and solvothermal green synthesis of self passivated carbon quantum dots

Highly fluorescent, self passivated carbon quantum dots (CQDs) have been synthesized using PEG-200 at room temperature for the first time followed by solvothermal modification to increase the quantum yield of these nano carbons. At elevated temperature and pressure good surface passivation has been observed. No sophisticated instrument nor passivating agent is required to fabricate these CQDs, making the procedure unique and novel with respect to all the existing protocols. Solvothermally synthesized carbon quantum dots (ST-CQDs) exhibited minimum toxicity and can be used easily for bioimaging.

Surface-modified sulfur nanoparticles: an effective antifungal agent against Aspergillus niger and Fusarium oxysporum

Surface-modified sulfur nanoparticles (SNPs) of two different sizes were prepared via a modified liquid-phase precipitation method, using sodium polysulfide and ammonium polysulfide as starting material and polyethylene glycol-400 (PEG-400) as the surface stabilizing agent. Surface topology, size distribution, surface modification of SNPs with PEG-400, quantitative analysis for the presence of sulfur in nanoformulations, and thermal stability of SNPs were determined by atomic force microscopy (AFM), dynamic light scattering (DLS) plus high-resolution transmission electron microscopy (HR-TEM), fourier transform infrared (FT-IR) spectroscopy, energy dispersive X-ray (EDX) spectroscopy, and thermogravimetric analysis (TGA), respectively. A simultaneous study with micron-sized sulfur (S0) and SNPs was carried out to evaluate their fungicidal efficacy against Aspergillus niger and Fusarium oxysporum in terms of radial growth, sporulation, ultrastructural modifications, and phospholipid content of the fungal strains using a modified poisoned food technique, spore-germination slide bioassay, environmental scanning electron microscopy (ESEM), and spectrometry. SNPs expressed promising inhibitory effect on fungal growth and sporulation and also significantly reduced phospholipid content.

Porous ZnO nanorod for targeted delivery of doxorubicin: in vitro and in vivo response for therapeutic applications

Cancer cell specific targeted delivery (TDD) by porous nanocarrier is on a high role. Here in a simple route for the synthesis of porous ZnO nanorods (ZnO) has been demonstrated. ZnO expressed very high surface area of 305.14 m2 g−1 (SBET) and uniformly distributed pores of 5 nm. In continuation ZnO has been fabricated with 3-aminophosphonic acid followed by folic acid to yield folate conjugated porous ZnO nanorod (ZnO-FA). High surface area, uniformly distributed pores on its surface make the nanocarrier suitable for high drug loading (88%) of the anticancer drug doxorubicin (DOX). A pH triggered drug release was observed with minimum release in pathophysical conditions. In vitro efficacy of DOX loaded ZnO-FA (ZnO-FA-DOX) has been evaluated against breast cancer cells MDA-MB-231, which is not possible alone by DOX or ZnO-FA. Targeted scaffold with pendant –NH2 group has been covalently bonded with fluorescent dye (RITC) for cellular uptake and imaging studies in MDA-MB-231 cells; the possible pathway for cancer regression has also been evaluated. Even in vivo acute and intravenous toxicological evaluation on murine model system complemented biocompatibility of ZnO-FA in TDD. All together we have collaged a template free synthesis of porous ZnO nanorod, successful targeting on to cancer cells, high drug loading, pH triggered drug release, in vitro efficacy of ZnO-FA-DOX against MDA-MB-231 cells and in vivo compatibility as well. We envisioned the future prospect of porous ZnO nanostructures in TDD.

Biochemical-, biophysical-, and microarray-based antifungal evaluation of the buffer-mediated synthesized nano zinc oxide: an in vivo and in vitro toxicity study.

Here we describe a simple, novel method of zinc oxide nanoparticle (ZNP) synthesis and physicochemical characterization. The dose-dependent antifungal effect of ZNPs, compared to that of micronized zinc oxide (MZnO), was studied on two pathogenic fungi: Aspergillus niger and Fusarium oxysporum. Superoxide dismutase (SOD) activity, ascorbate peroxidase activity, catalase activity, glutathione reductase (GR) activity, thiol content, lipid peroxidation, and proline content in ZNP-treated fungal samples were found to be elevated in comparison to the control, which strongly suggested that the antifungal effect of ZNPs was due to the generation of reactive oxygen species (ROS). Protein carbonylation, another marker of oxidative stress, was also evaluated by the dinitrophenyl hydrazine (DNPH) binding assay and Fourier transform infrared (FTIR) spectral analysis followed by Western blot and microarray analysis of fungal samples to confirm ROS generation by ZNPs. Micrographic studies for the morphological analysis of fungal samples (ZNP-treated and a control) exhibited an alteration in fungal morphology. The bioavailability of ZNPs on fungal cell was confirmed by energy-dispersive X-ray (EDX) analysis followed by high-resolution transmission electron microscopy (HR-TEM) and confocal microscopic analysis of the fungal samples. In vivo acute oral toxicity, acetylcholine esterase activity, and a fertility study using a mice model were also investigated for ZNPs. The long-term toxicity of ZNPs through intravenous injection was evaluated and compared to that of MZnO. The in vitro comparative toxicity of ZNPs and MZnO was evaluated on MRC-5 cells with the help of water-soluble tetrazolium (WST-1) and lactate dehydrogenase (LDH) assays. These results suggested that ZNPs could be used as an effective fungicide in modern medical and agricultural sciences.

Surface functionalized amorphous nanosilica and microsilica with nanopores as promising tools in biomedicine

Cellular interactions with engineered nanoparticles (NPs) are dependent on many properties, inherent to the nanoparticle (viz. size, shape, surface characteristics, degradation, agglomeration/dispersal, and charge, etc.). Modification of the surface reactivity via surface functionalization of the nanoparticles to be targeted seems to be important. Utilization of different surface functionalization methods of nanoparticles is an emerging field of basic and applied nanotechnology. It is well known that many disease-causing organisms induce host lipids and if deprived, their growth is inhibited in vivo. Amorphous nanosilica (ANS) and amorphous microsilica with nanopores (AMS) were prepared by a combination of wet chemistry and high-energy ball milling. Lipophilic moieties were attached to both ANS and AMS via chemical surface functionalization method. Lipophilic ANS and AMS were found to inhibit the growth of Bombyx mori nuclear polyhedrosis virus (BmNPV) and chicken malarial parasites via absorption of silkworm hemolymph and chicken serum lipids/lipoproteins, respectively, in vivo. Therefore, intelligent surface functionalization of NP is an important concept, and its application in curing chicken malaria and BmNPV is presented here. Surface functionalization method reported in this paper might serve as a valuable technology for treating many diseases where pathogens induce host lipid.