Browsing by Author "Rashmi Kesarwani"

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Amine-Functionalized Graphene Quantum Dots Conjugated with Amphotericin B: Synthesis, Characterization, and In Vitro Evaluation for Visceral Leishmaniasis Treatment
(American Chemical Society, 2025) Prasoon Madhukar; Rashmi Kesarwani; Sundaram Pandey; Vishal K. Singh; Mallikarjuna Rao Gedda; Omprakash Singh; Mohammad R. Shaz; Rajiv Kumar; Santhanam Sundar
Visceral Leishmaniasis (VL) is a life-threatening parasitic disease primarily affecting populations in resource-limited, endemic regions. Existing treatments for VL face limitations such as toxicity, high costs, and suboptimal efficacy in specific patient groups. Given the lack of a vaccine, chemotherapy remains the only option, emphasizing the urgent need for safer and more effective treatments. Nanotechnology offers promising avenues to overcome these challenges. This study introduces a novel approach involving amine-functionalized graphene quantum dots (fGQDs) conjugated with Amphotericin B (fGQDAmB) to enhance targeted drug delivery to Leishmania-infected macrophages. This novel approach, which could lead to a safer and more effective treatment for VL, is a significant contribution to the field. Structural characterization by XRD and FTIR confirmed successful GQD synthesis and functionalization, while cellular assays demonstrated significantly higher macrophage uptake and enhanced antileishmanial efficacy. fGQDAmB demonstrated approximately 4.2-fold greater potency against intracellular amastigotes and 2-fold higher efficacy against promastigotes, while also exhibiting reduced cytotoxicity compared to conventional AmB. The safety and effectiveness of fGQDAmB were further validated through hemolysis assay, providing reassurance and confidence about its potential use and instilling confidence in the potential of Quantum Dot-based Nanomedicine formulations. © 2025 The Authors. Published by American Chemical Society.
Catalytic mechanism of TiO2 quantum dots on the de/re-hydrogenation characteristics of magnesium hydride
(Elsevier Ltd, 2021) Sunita Kumari Pandey; Ashish Bhatnagar; Vivek Shukla; Rashmi Kesarwani; Uday Deshpandey; Thakur Prasad Yadav
In the present study, the catalyst anatase titanium dioxide (TiO2) quantum dots (QDs) of size ∼ (2.50–4.00)nm was successfully synthesized by the hydrothermal method. The formation of TiO2: QDs has been established by UV–Vis spectroscopy and confirmed by transmission electron microscopy. Here, we report the catalytic action of TiO2:QDs on de/re-hydrogenation properties of magnesium hydride (MgH2/Mg). By catalyzing MgH2 through this catalyst, the onset desorption temperature of MgH2 gets reduced significantly from ∼360 °C (for ball-milled MgH2) to ∼260 °C. Moreover, the Mg-TiO2: QDs sample absorbed a significant amount of hydrogen up to ∼6.10 wt% in just 77sec at 280 °C. Improved rehydrogenation kinetics has been found even at lower temperatures by absorbing ∼5.30 wt% in 74 s at 225 °C and ∼5.0 wt% of hydrogen in 30 min at 100 °C. Based on structural,.microstructural, and XPS investigations, a feasible mechanism for improved hydrogen sorption and cyclic stability in MgH2 catalyzed with TiO2:QDs has been explained and discussed. To our knowledge, no studies have been carried out on the sorption of hydrogen in MgH2 catalyzed by TiO2:QDs. © 2021 Hydrogen Energy Publications LLC
Enhancement in hydrogen sorption behaviour of MgH2 catalyzed by graphene quantum dots
(Elsevier Ltd, 2024) Rashmi Kesarwani; Ashish Bhatnagar; Satish K. Verma; M. Sterlin Leo Hudson; M.A. Shaz
The present investigation reports the synthesis of graphene quantum dots (GQDs) by the microwave-assisted green synthesis method, and its catalytic effect in improving the hydrogen storage behaviour of magnesium hydride (MgH2). Transmission electron microscopy, UV–Vis, Raman, FTIR and XRD analysis was done to characterize the samples. It has been observed that the as-synthesized GQDs are in the size range of 3–12 nm. The catalytic activity of GQDs on improving the de/re-hydrogenation kinetics of MgH2 has been investigated with different additive concentrations. It has been observed that there is an improvement in the hydrogen sorption characteristics of ball-milled MgH2 when 7 wt.% GQDs was employed. The onset dehydrogenation temperature of 7 wt.% GQDs admixed ball milled MgH2 (7 % GQDs-MgH2) was observed at 300 ᵒC, which is 60 ᵒC lower than that of additive free ball-milled MgH2 under identical condition. Furthermore, the 7 % GQDs-MgH2 sample reabsorbs nearly 5 wt.% hydrogen in 2.5 min at 300 ᵒC and 15 atm hydrogen pressure. The GQDs catalyzed MgH2 sample exhibit good de/re-hydrogenation cyclic stability. No significant loss in hydrogen capacity was noticed even after 25 de-/re-hydrogenation cycles. From the Van't Hoff plot, the formation enthalpy of 7 % GQDs-MgH2 was estimated to be 58 kJmol-1. © 2024 Hydrogen Energy Publications LLC
Immobilization of fenugreek β-amylase onto functionalized graphene quantum dots (GQDs) using Box-Behnken design: Its biochemical, thermodynamic and kinetic studies
(Elsevier B.V., 2020) Dinesh Chand Agrawal; Anjali Yadav; Rashmi Kesarwani; O.N. Srivastava; Arvind M. Kayastha
β-Amylase was immobilized onto GQDs using 3-aminopropyltriethoxysilane and glutaraldehyde. Optimization was carried out by Box-Behnken design and binding was confirmed by SEM, AFM, FTIR and fluorescence microscopy. Predicted optimum immobilization efficiency (88.64%) was very close to actual (87.98%), which confirmed the success of the immobilization process. The immobilized enzyme showed maximum activity at pH 5.0 and 57 °C, whereas Km and Vmax were found to be 6.40 mg/mL and 714.28 μmol/min/mg, respectively. The enzyme retained 75% activity after 12 uses at 30 °C. Increased values of ΔG° ΔH°, half-life and activation energy of the enzyme inactivation (ΔEd) revealed that thermo-stability increases after immobilization and the process followed first-order kinetics (r2 > 0.96). The activation energy of catalysis (ΔEa) and ΔEd for immobilized enzyme were 22.58 and 158.99 ± 1.10 kJ/mol, respectively which revealed that denaturation of the enzyme requires a higher amount of energy rather than catalysis. Thermodynamic and fluorescence spectroscopic studies revealed that the process is non-spontaneous (ΔG > 0) and endothermic (ΔH > 0) and occurred through protein unfolding rather than aggregation (ΔS > 0). Thus increase in thermo-stability of immobilized fenugreek β-amylase and non-toxic nature of GQDs could be exploited for maltose production in beverage, food and pharmaceutical industries. © 2018 Elsevier B.V.
Improved hydrogen storage characteristics of magnesium hydride using dual auto catalysts (MgF2+CsH)
(Elsevier Ltd, 2022) Rashmi Kesarwani; Vivek Shukla; M. Sterlin Leo Hudson; Mohammad Abu Shaz
This study discusses the improvement in the hydrogen sorption properties of MgH2 with dual auto-catalysts, MgF2 and CsH. The auto-catalysts are formed due to the reaction between MgH2 and CsF during the dehydrogenation reaction of MgH2. It has been observed that MgF2 and CsH not only improve MgH2's hydrogen sorption properties, also aids its positive thermodynamic tuning, which is favourable for hydrogen storage. The on-set desorption temperature of MgH2 catalysed by MgF2+CsH is 249 °C, which is 106 °C lower than that of ball-milled MgH2 without any additives measured under identical measurement conditions. The catalysts helped in improving both the de/rehydrogenation kinetics of MgH2. The MgH2 catalysed by MgF2+CsH released 4.73 wt % H2 in 15 min at 300 °C. Furthermore, its initial re-hydrogenation rate under isothermal conditon at 300 °C is 4.62 wt % H2 in 5 min. The catalysed sample exhibits negligible hydrogen storage degradation of 0.39 wt % H2 after 25 de/re-hydrogenation cycles. Using the Kissinger method, the activation energy of MgH2 catalysed by MgF2+CsH was estimated to be 98.1 ± 0.5 kJmol-1. From the Van't Hoff plot, the decomposition and formation enthalpies of MgH2 were determined to be 66.6 ± 1.1 kJmol-1 and 63.1 ± 1.2 kJmol-1, respectively. From the experimental observation, a feasible mechanism for the de/re-hydrogenation behaviour of MgH2 with MgF2+CsH is proposed. © 2022 Hydrogen Energy Publications LLC