Browsing by Author "Atul Kumar Tiwari"

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A whole cell fluorescence quenching-based approach for the investigation of polyethyleneimine functionalized silver nanoparticles interaction with Candida albicans
(Frontiers Media S.A., 2023) Atul Kumar Tiwari; Munesh Kumar Gupta; Roger J. Narayan; Prem C. Pandey
The antimicrobial activity of metal nanoparticles can be considered a two-step process. In the first step, nanoparticles interact with the cell surface; the second step involves the implementation of the microbicidal processes. Silver nanoparticles have been widely explored for their antimicrobial activity against many pathogens. The interaction dynamics of functionalized silver nanoparticles at the biological interface must be better understood to develop surface-tuned biocompatible nanomaterial-containing formulations with selective antimicrobial activity. Herein, this study used the intrinsic fluorescence of whole C. albicans cells as a molecular probe to understand the cell surface interaction dynamics of polyethyleneimine-functionalized silver nanoparticles and antifungal mechanism of the same. The results demonstrated that synthesized PEI-f-Ag-NPs were ~ 5.6 ± 1.2 nm in size and exhibited a crystalline structure. Furthermore, the recorded zeta potential (+18.2 mV) was associated with the stability of NPS and shown a strong electrostatic interaction tendency between the negatively charged cell surface. Thus, rapid killing kinetics was observed, with a remarkably low MIC value of 5 μg/mL. PEI-f-Ag-NPs quenched the intrinsic fluorescence of C. albicans cells with increasing incubation time and concentration and have shown saturation effect within 120 min. The calculated binding constant (Kb = 1 × 105 M−1, n = 1.01) indicated strong binding tendency of PEI-f-Ag-NPs with C. albicans surface. It should also be noted that the silver nanoparticles interacted more selectively with the tyrosine-rich proteins in the fungal cell. However, calcofluor white fluorescence quenching showed non-specific binding on the cell surface. Thus, the antifungal mechanisms of PEI-f-Ag-NPs were observed as reactive oxygen species (ROS) overproduction and cell wall pit formation. This study demonstrated the utility of fluorescence spectroscopy for qualitative analysis of polyethyleneimine-functionalized silver nanoparticle interaction/binding with C. albicans cell surface biomolecules. Although, a quantitative approach is needed to better understand the interaction dynamics in order to formulate selective surface tuned nanoparticle for selective antifungal activity. Copyright © 2023 Tiwari, Gupta, Narayan and Pandey.
Aggregation-Resistant, Turn-On-Off Fluorometric Sensing of Glutathione and Nickel (II) Using Vancomycin-Conjugated Gold Nanoparticles
(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Atul Kumar Tiwari; Munesh Kumar Gupta; Hari Prakash Yadav; Roger J. Narayan; Prem C. Pandey
Glutathione (GSH) and nickel (II) cation have an indispensable role in various physiological processes, including preventing the oxidative damage of cells and acting as a cofactor for lipid metabolic enzymes. An imbalance in the physiological level of these species may cause serious health complications. Therefore, sensitive and selective fluorescent probes for the detection of GSH and nickel (II) are of great interest for clinical as well as environmental monitoring. Herein, vancomycin-conjugated gold nanoparticles (PEI-AuNP@Van) were prepared and employed for the detection of GSH and nickel (II) based on a turn-on-off mechanism. The as-synthesized PEI-AuNP@Van was ~7.5 nm in size; it exhibited a spherical shape with face-centered cubic lattice symmetry. As compared to vancomycin unconjugated gold nanoparticles, GSH led to the turn-on state of PEI-AuNP@Van, while Ni2+ acted as a fluorescence quencher (turn-off) without the aggregation of nanoparticles. These phenomena strongly justify the active role of vancomycin conjugation for the detection of GSH and Ni2+. The turn-on-off kinetics was linearly proportional over the concentration range between 0.05–0.8 µM and 0.05–6.4 μM. The detection limits were 205.9 and 90.5 nM for GSH and Ni2+, respectively; these results are excellent in comparison to previous reports. This study demonstrates the active role of vancomycin conjugation for sensing of GSH and Ni2+ along with PEI-AuNP@Van as a promising nanoprobe. © 2024 by the authors.
Amine-Functionalized Silver Nanoparticles: A Potential Antiviral-Coating Material with Trap and Kill Efficiency to Combat Viral Dissemination (COVID-19)
(Springer Nature, 2023) Atul Kumar Tiwari; Munesh Kumar Gupta; Govind Pandey; Shivangi Pandey; Prem C. Pandey
The outbreak of COVID-19 has drastically affected the daily lifestyles of people globally where specific Coronavirus-2 transmits primarily by respiratory droplets. Structurally, the SARS-CoV-2 virus is made up of four types of proteins in which S-protein is indispensable among them, as it causes rapid replication in the host body. Therefore, the glycine and alanine composed of HR1 of S-protein is the ideal target for antiviral action. Different forms of surface-active PPEs can efficiently prevent this transmission in this circumstance. However, the virus can survive on the conventional PPEs for a long time. Hence, the nanotechnological approaches based on engineered nanomaterials coating on medical equipments can potentially prevent the dissemination of infections in public. Silver nanoparticles with tuneable physicochemical properties and versatile chemical functionalization provide an excellent platform to combat the disease. The coating of amine-functionalized silver nanoparticle (especially amine linked to aliphatic chain and trialkoxysilane) in its nanostructured form enables cloths trap and kill efficient. PPEs are a primary and reliable preventive measure, although they are not 100% effective against viral infections. So, developing and commercializing surface-active PPEs with trap and kill efficacy is highly needed to cope with current and future viral infections. This review article discusses the COVID-19 morphology, antiviral mechanism of Ag-NPs against SARS-CoV-2 virus, surface factors that influence viral persistence on fomites, the necessity of antiviral PPEs, and the potential application of amine-functionalized silver nanoparticles as a coating material for the development of trap and kill-efficient face masks and PPE kits. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC 2022. Springer Nature or its licensor holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
Analysis of agile supply chain enablers for an Indian manufacturing organisation
(Inderscience Publishers, 2020) Bharat Singh Patel; Atul Kumar Tiwari; Manish Kumar; Cherian Samuel; Goutam Sutar
The objective of present work is to categorise agile supply chain (ASC) enablers and examine its relative importance for better implementation of agility in perspective of the Indian manufacturing industry. This study deploys, analytic hierarchy process (AHP), a popular multi-criteria decision making (MCDM) tool as a solution methodology, such that the decision problem breaks into a hierarchy of different levels constituting goal, criteria and alternatives. The results show that there are three enablers namely virtual enterprises, customer satisfaction and adaptability are among the top priority enablers; enabler collaborative relationship is the moderate priority enabler and remaining three enablers i.e., use of information technology, market sensitivity and flexibility are the lowest priority enablers. To effectively implement agility in the supply chain, this study proposes that the manufacturing industries need to focus on the most important ASC enablers and also address the enablers with the least important at a later stage. Copyright © 2020 Inderscience Enterprises Ltd.
Antifungal Susceptibility Profile of Aspergillus Strains Isolated From the Lower Respiratory Tract in Eastern Indian Patients: A Hospital-Based Study
(John Wiley and Sons Inc, 2025) Aishwarya Nikhil; Sradha Choudhury; Mohit Bhatia; Atul Kumar Tiwari; Ritika Srivastava; Abhirami Prasad; Ragini Tilak; Munesh Kumar Gupta; Roger Jagdish Narayan
Respiratory aspergillosis refers to a range of infections, from allergic to chronic and invasive, which can be life-threatening and are primarily caused by Aspergillus fumigatus and Aspergillus flavus. Other species, including Aspergillus terreus, Aspergillus nidulans, and Aspergillus versicolor, have also been implicated in respiratory infections. Treatment for chronic to invasive pulmonary aspergillosis typically involves azole antifungal drugs, although studies have shown varying minimum inhibitory concentrations (MIC) for these medications, with a growing concern over voriconazole resistance. During the period from August 2022 to May 2024, characteristic hyphae were detected in 7.2% of lower respiratory samples, with culture positivity in 12.8%, including early morning sputum and bronchoalveolar lavage fluid samples. A. flavus (n = 282) was the most frequently isolated species, followed by A. fumigatus (n = 86). Additionally, a seasonal trend was observed for Aspergillus infections, with peaks in April and September. The MIC of itraconazole, voriconazole, posaconazole, amphotericin B, ravuconazole, and caspofungin were assessed for the isolated Aspergillus species. A higher MIC of amphotericin B was observed against A. flavus and A. terreus, whereas azoles exhibited a relatively lower MIC. Caspofungin and posaconazole exhibited the lowest MIC against the isolated Aspergillus species. Therefore, it is crucial to identify the causative fungi and determine the antifungal MIC for Aspergillus species responsible for lower respiratory tract infections. This study emphasizes the significance of respiratory aspergillosis in TB-endemic regions of Eastern India. © 2025 The Author(s). MicrobiologyOpen published by John Wiley & Sons Ltd.
Effect of the Organic Functionality on the Synthesis and Antimicrobial Activity of Silver Nanoparticles
(World Scientific Publishing Co., 2025) Prem Chandra Pandey; Atul Kumar Tiwari; Munesh Kumar Gupta; Govind Pandey; Roger Jagdish Narayan
In this paper, the effects of the organic reducing agent and 3-aminopropyltrimethoxysilane on the synthesis and properties of mono-, bi-, and trimetallic noble metal nanoparticles were considered; the antimicrobial activity of these nanomaterials was also evaluated. It was shown that 3-aminoptopyltrimethoxysilane- treated noble metal cations undergo rapid conversion into nanoparticles in the presence of three organic reducing agents, namely, 3-glycidoxypropyltrimethoxysilane (3-GPTMS), cyclohexanone and formaldehyde; the nanoparticles were formed on the order of one minute under microwave incubation. Bimetallic nanoparticles were formed by simultaneous or sequential reduction of metal cations; the formation of trimetallic nanoparticles containing gold, silver and palladium was demonstrated using a similar approach. The nanoparticles were characterized using UV-Visible light spectrophotometry, transmission electron microscopy and zeta potential measurements. All three nanoparticles exhibited a size ≤ 10nm size. The nanoparticles showed antimicrobial activity against Acinetobacter baumannii. Scanning electron microscopy imaging showed an alteration in the size and shape of nanoparticle-treated bacterium, with bleb formation and cell wall disruption observed within 1 h of incubation at the MBC values of the nanoparticles. Fluorescence spectrophotometric imaging of silver nanoparticle-Acinetobacter baumannii interactions suggested selective binding of silver nanoparticles to surface proteins. Our results showed the preparation of the novel silver nanoparticles with potent Anti- Acinetobacter baumannii activity, which can serve as an alternative to conventional antimicrobial agents. © 2025 by World Scientific Publishing Co. Pte. Ltd. All rights reserved.
Fuzzy number with nonlinear membership functions to provide flexibility in a multi objective travelling salesman problem
(Springer Verlag, 2013) Atul Kumar Tiwari; Cherian Samuel; Vinay Pratap Singh; Vivek Saraswati
Travelling Salesman Problem (TSP), as extensively discussed in literature is an NP hard problem and among the most challenging problems in operations research, industrial engineering and computational mathematics, which has been deciphered and scrutinized under different headings and using different approaches e.g. Artificial Intelligence techniques, evolutionary algorithms and linear programming models under deterministic conditions. However, the information about real life processes is not always crisp but is often available as vague, uncertain and imprecise data. Fuzzy numbers finds application in handling vague terms, and therefore they can be suitably used to model real life scenarios involving vague parameters so as to obtain optimal solutions. Fuzzy multi-objective linear programming usually deals with flexible aspiration levels that are indicative of optimality when considering all objectives or goals simultaneously with possible deviation in objectives or constraints. Therefore in this study we develop a fuzzy multi-objective linear programming model with nonlinear membership functions for solving a multi objective TSP in order to simultaneously minimize the three parameters cost, distance and time. The importance of these parameters is assigned as weights to these objectives in the final model using AHP. The proposed model will give a compromised solution for best optimality and higher satisfaction level for the three parameters being considered in uncertain environment. The primary contribution of this study is a fuzzy mathematical model using nonlinear membership functions, more precisely the exponential functions to ensure an optimal solution in vague, imprecise and uncertain environment. © 2013 Springer.
Making vancomycin a potent broad-spectrum antimicrobial agent using polyaziridine-stabilized gold nanoparticles as a delivery vehicle
(SAGE Publications Ltd, 2025) Atul Kumar Tiwari; Aishwarya Nikhil; Avinash Kumar Chaurasia; Prem Chandra Pandey; Roger Jagdish Narayan; Munesh Kumar Gupta
The rise of antimicrobial drug resistance among microorganisms presents a global challenge to clinicians. Therefore, it is essential to investigate drug delivery systems to combat resistant bacteria and fungi. This study examined the potential and mode of action of vancomycin-conjugated gold nanoparticles (PEI-AuNP@Van) to enhance vancomycin’s biocidal activity against C. tropicalis, C. albicans, E. coli, and P. aeruginosa. Drug conjugation and nanoparticle characterization were assessed using UV-Vis spectroscopy, X-ray diffraction, TEM, ATR-FTIR, and fluorescence spectroscopy. Effective vancomycin conjugation on polyethyleneimine-stabilized gold nanoparticles was achieved via electrostatic interactions or hydrogen bonding between the COO-/OH groups of vancomycin and the NH- groups of polyethyleneimine, yielding nanoparticles with a narrow size distribution and high zeta potential. The high luminescence of the nanoparticles facilitated their detection in microbial cells. PEI-AuNP@Van was internalized in C. albicans and C. tropicalis but showed surface adsorption in E. coli and P. aeruginosa. The in vitro results indicated that the nanodelivery system exhibited superior biocidal activity against the tested strains compared to free vancomycin and unconjugated AuNPs. The mode of action of PEI-AuNP@Van was cell-type-dependent, involving intracellular reactive oxygen species accumulation, cell membrane integrity loss, and apoptosis. The development of antimicrobial nanoformulations using AuNPs and efficient conjugation systems offers a promising approach to address antimicrobial drug resistance. © The Author(s) 2025.
Measuring procurement flexibility in disastrous environment
(Inderscience Publishers, 2014) Atul Kumar Tiwari; Anunay Tiwari; Cherian Samuel
Flexibility in supply chain is proved to be a way of countering uncertainties and planning strategies. In this paper an attempt is made to evaluate procurement flexibility at supplier buyer interface in disastrous scenarios. This can be considered to be an extension of research work carried out by Das and Abdel-Malek (2003). This paper contributes by analysing supply chain disruptions in extremely risky environments that are coupled with uncertainties in demand and lead times from downstream. These uncertainties are captured by a probability density functions, more precisely the normal distributions. A flexibility measure ψ is designed which not only ensures timely supply of material from the supplier but also ensures to maintain a continuous supply at minimal risk to buyer in case of complete disruptions at supplier's production sites. As this flexibility measure ψ varies from 0 to 1, it reflects a 0 to 100% flexibility of supplier from buyers' viewpoint. Copyright © 2014 Inderscience Enterprises Ltd.
Molecular weight of polyethylenimine-dependent transfusion and selective antimicrobial activity of functional silver nanoparticles
(Cambridge University Press, 2020) Atul Kumar Tiwari; Munesh Kumar Gupta; Govind Pandey; Roger J. Narayan; Prem C. Pandey
Synthetic cationic polymer-mediated synthesis of silver nanoparticles and selective antimicrobial activity of the same were demonstrated. Polyethyleneimine (PEI)-coated silver nanoparticles showed antimicrobial activity against Acinetobacter baumannii as a function of the polymeric molecular weight (MW) of PEI. Silver nanoparticles were coated with PEI of three different MWs: Ag-NP-1 with PEI exhibiting a MW of 750,000, Ag-NP-2 with PEI exhibiting a MW of 1300, and Ag-NP-3 with PEI exhibiting a MW of 60,000. These nanoparticles showed a particle size distribution of 4-20 nm. The nanoparticles exhibited potent antimicrobial activity against A. baumannii, with the minimum inhibitory concentration of Ag-NP-1, Ag-NP-2, and Ag-NP-3 on the order of 5, 10, and 5 μg/mL, respectively, and minimum bactericidal concentration of Ag-NP-1, Ag-NP-2, and Ag-NP-3 on the order of 10, 20, and 10 μg/mL, respectively. Fluorescence imaging of Ag-NPs revealed selective transfusion of Ag-NPs across the cell membrane as a function of the polymeric MW; differential interaction of the cytoplasmic proteins during antimicrobial activity was observed. Copyright © Materials Research Society 2020.
Molecular Weights of Polyethyleneimine-Dependent Physicochemical Tuning of Gold Nanoparticles and FRET-Based Turn-On Sensing of Polymyxin B
(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Atul Kumar Tiwari; Munesh Kumar Gupta; Ramovatar Meena; Prem C. Pandey; Roger J. Narayan
Environmental monitoring and the detection of antibiotic contaminants require expensive and time-consuming techniques. To overcome these challenges, gold nanoparticle-mediated fluorometric “turn-on” detection of Polymyxin B (PMB) in an aqueous medium was undertaken. The molecular weight of polyethyleneimine (PEI)-dependent physicochemical tuning of gold nanoparticles (PEI@AuNPs) was achieved and employed for the same. The three variable molecular weights of branched polyethyleneimine (MW 750, 60, and 1.3 kDa) molecules controlled the nano-geometry of the gold nanoparticles along with enhanced stabilization at room temperature. The synthesized gold nanoparticles were characterized through various advanced techniques. The results revealed that polyethyleneimine-stabilized gold nanoparticles (PEI@AuNP-1-3) were 4.5, 7.0, and 52.5 nm in size with spherical shapes, and the zeta potential values were 29.9, 22.5, and 16.6 mV, respectively. Accordingly, the PEI@AuNPs probes demonstrated high sensitivity and selectivity, with a linear relationship curve over a concentration range of 1–6 μM for polymyxin B. The limit of detection (LOD) was calculated as 8.5 nM. This is the first unique report of gold nanoparticle nano-geometry-dependent FRET-based turn-on detection of PMB in an aqueous medium. We believe that this approach would offer a complementary strategy for the development of a highly sophisticated and advanced sensing system for PMB and act as a template for the development of new nanomaterial-based engineered sensors for rapid antibiotic detection in environmental as well as biological samples. © 2024 by the authors.
Nano–Bio Interaction and Antibacterial Mechanism of Engineered Metal Nanoparticles: Fundamentals and Current Understanding: Nano–bio interaction and antibacterial mechanism…: A. K. Tiwari et al.
(Springer, 2025) Atul Kumar Tiwari; Prem Chandra Pandey; Munesh Kumar Gupta; Roger Jagdish Narayan
The rapid development of multidrug resistance in a wide range of microorganisms poses a significant clinical challenge for healthcare professionals treating infectious diseases. Over the last decade, research has focused on the preparation of metal-based nanomaterials with antibacterial, antiviral, and antifungal activities to combat communicable diseases. Several metal nanomaterials, such as gold, copper, silver, palladium, and metal oxides, such as titanium, zinc, and iron, have demonstrated encouraging antimicrobial properties against multidrug-resistant microorganisms. The nano–bio interaction of metal nanoparticles are particularly influenced by their physicochemical properties, including shape, size, surface charge, ligand capping, doping, pH stability, roughness, and crystal structure. Once interacting, nanoparticles exert their biocidal effects through various pathways, such as enhanced intracellular reactive oxygen species, cell membrane damage, membrane potential depolarization, DNA damage, biofilm destabilization followed by interactions with biofilm components. However, a clear understanding of the connection between the specific physicochemical properties and antimicrobial mechanisms of metal nanoparticles is lacking. Thus this comprehensive review article discusses different fundamental aspects of nano–bio interactions of metal nanoparticles with planktonic as well as biofilm form of bacteria, the associated antimicrobial mechanisms along with recent advancements and therapeutic challenges. Graphical abstract: (Figure presented.) © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.
New D-π-A-Based Coumarin- Derived Fluorescent Theranostic Probes With Broad-Spectrum Antimicrobial Activity
(John Wiley and Sons Inc, 2025) Himanshu Rai; Atul Kumar Tiwari; Aishwarya Nikhil; Ankit Tiwari; Prahalad Singh Bharti; Suresh Kumar Maury; Munesh Kumar Gupta; Sundaram Singh; Saroj Kumar; Gyan Prakash Modi
Understanding how multidrug-resistant (MDR) bacteria and fungi defy the existing antimicrobial agents requires innovative tools and techniques for real-time, in situ exploration of bacterial responses to antibiotics. Fluorescence-tagged antibiotics or dyes with inherent antimicrobial activity can provide a profound understanding of the molecular biology underlying antibiotic action and resistance mechanisms. Cutting-edge research highlights the pursuit of benzo-α-pyrone (coumarin) derivatives due to their excellent pharmacokinetics, diverse pharmacological activities, and innovative fluorescence molecular probes. In this study, donor-π-acceptor-based coumarin dyes were designed and evaluated for antimicrobial efficacy against fungal strains (Candida albicans), Gram-negative pathogens (Escherichia coli), and Gram-positive bacteria (Staphylococcus aureus). I-6 exhibited notable antimicrobial activity against S. aureus and C. albicans compared with E. coli. Conversely, I-9, a congener of I-6, showed a comparable affinity for S. aureus but found poor activity against the remaining tested strains. Mechanistic investigative studies unveiled that the inhibitory efficacy of I-6 can be attributed to its capacity to generate high reactive oxygen species (ROS) formation. Despite the evident antimicrobial potential of I-6 in the data, our future prospects, including real-time visualization to study physiological processes like uptake, distribution, and mechanism of action through fluorescence-based imaging modalities, could enhance the applicability of these probes. © 2025 Deutsche Pharmazeutische Gesellschaft.
Photocatalytic and Antibacterial NiO/MgO Nanocomposites for Efficient Dyes Removal From Industrial Wastewater
(John Wiley and Sons Inc, 2025) Anuradha Kumari; Annesha Roy; Manjot Kaur; Akshay Kumar; Kajal Kumari; Usha Singh Gaharwar; Atul Kumar Tiwari; Ramovatar Meena
The presence of non-biodegradable industrial waste, particularly dyes, has led to pollution of aquatic ecosystems. Consequently, it is crucial to devise effective strategies to remove industrial contaminants. This study focused on creating nanomaterials for wastewater treatment. NiO/MgO nanocomposites (NCs) were produced via chemical precipitation and subsequently characterized. X-ray diffraction (XRD) verified the crystalline nature of NiO/MgO with a face-centered cubic (FCC) structure, which promoted strong interfacial interactions. Scanning electron microscopy (SEM) showed that the NiO/MgO NCs agglomerated into spherical and irregular shapes, whereas transmission electron microscopy (TEM) confirmed a size range of 65–100 nm. UV–vis spectroscopy indicated absorption in the UV–vis spectrum, suggesting its photocatalytic potential. The photocatalytic performance of the NiO/MgO NCs was assessed for organic dyes such as methylene blue (MB), Congo red (CR), and methyl orange (MO) under UV–vis light, demonstrating notable efficiency at higher dye concentrations. The highest degradation efficiency was recorded for CR (∼77% at 100 ppm over 60 min), followed by MO (∼71.6%) and MB (∼70%). The enhanced photocatalytic activity was linked to the nanostructured morphology, effective charge separation, and decreased electron-hole recombination. NiO/MgO NCs also showed strong antibacterial properties against both gram-positive and gram-negative bacterial strains. Antimicrobial mechanisms include the production of reactive oxygen species (ROS), disruption of membranes, and interactions with metal ions, which demonstrate the multi-functionality of NiO/MgO NCs as efficient wastewater treatment agents. © 2025 Wiley-VCH GmbH.
Role of different polymer-stabilized metal nanoparticles in fluorescein reporter–based turn-off-on glutathione detection
(Springer Nature, 2025) Atul Kumar Tiwari; Prem Chandra Pandey; Roger Jagdish Narayan
In a fluorescence-reporter-based system, fluorescence quenching occurs when colloidal metal nanoparticles are added to fluorescein solutions owing to Förster resonance energy transfer (FRET) and the inner filter effect (IFE), depending on the physicochemical properties of the nanoparticles. This study examined the impact of various polymeric stabilizing agents on the fluorescence quenching behaviour of metal nanoparticles. Polyethyleneimine-stabilized gold nanoparticles exhibited superior fluorescence quenching of fluorescein due to strong dipole–dipole interactions, which led to FRET between the nanoparticle and fluorescein. Ligand exchange between loosely bound polyethyleneimine to the metal core and glutathione (GSH), in the presence of glutathione, led to fluorescence recovery. © The Author(s), under exclusive licence to The Materials Research Society 2025.
Size and Zeta Potential Clicked Germination Attenuation and Anti-Sporangiospores Activity of PEI-Functionalized Silver Nanoparticles against COVID-19 Associated Mucorales (Rhizopus arrhizus)
(MDPI, 2022) Atul Kumar Tiwari; Munesh Kumar Gupta; Govind Pandey; Ragini Tilak; Roger J. Narayan; Prem C. Pandey
The SARS-CoV-2 infections in Indian people have been associated with a mucormycotic fungal infection caused by the filamentous fungi Rhizopus arrhizus. The sporangiospores of R. arrhizus are omnipresent in the environment and cause infection through inhalation or ingestion of contaminated air and foods. Therefore, the anti-sporangiospore activity of polyethyleneimine functionalized silver nanoparticles (PEI-f-Ag-NPs) with variable size and surface charge as a function of the molecular weight of PEI was explored. The results showed that both PEI-f-AgNP-1 and PEI-f-AgNP-2, potentially, attenuated the germination and reduced the viability of sporangiospores. Furthermore, the results showed that the minimum inhibitory concentration (MIC) values of both PEIf-AgNP-1 and PEI-f-AgNP-2 (1.65 and 6.50 μg/mL, respectively) were dependent on the nanoparticle size and surface ζ potentials. Similarly, the sporangiospore germination inhibition at MIC values was recorded, showing 97.33% and 94% germination inhibition, respectively, by PEI-f-AgNP-1 and 2 within 24 h, respectively. The confocal laser scanning microscopy, SEM-EDS, and confocal Raman spectroscopy investigation of PEI-f-Ag-NPs treated sporangiospores confirmed size and surface charge-dependent killing dynamics in sporangiospores. To the best of our knowledge, this is the first investigation of the polyethyleneimine functionalized silver nanoparticle-mediated size and surface charge-dependent anti-sporangiospore activity against R. arrhizus, along with a possible antifungal mechanism. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
Synthesis of vancomycin functionalized fluorescent gold nanoparticles and selective sensing of mercury (II)
(Frontiers Media SA, 2023) Atul Kumar Tiwari; Hari Prakash Yadav; Munesh Kumar Gupta; Roger J. Narayan; Prem C. Pandey
Mercury ions (Hg2+) are widely found in the environment; it is considered a major pollutant. Therefore, the rapid and reliable detection of Hg2+ is of great technical interest. In this study, a highly fluorescent, sensitive, and selective fluorometric assay for detecting Hg2+ ions was developed using vancomycin functionalized and polyethyleneimine stabilized gold nanoparticles (PEI-f-AuNPs@Van). The as-made gold nanoparticles were highly fluorescent, with excitation and emission maxima occurring at 320 and 418 nm, respectively. The size of nanoparticles was ~7 nm; a zeta potential of ~38.8 mV was determined. The XRD analysis confirmed that the nanoparticles possessed crystalline structure with face centerd cubic symmetry. Using the PEI-f-AuNP@Van probe, the detection limit of Hg2+ ion was achieved up to 0.988 nM (within a linear range) by calculating the KSV. However, the detection limit in a natural environmental sample was shown to be 12.5 nM. Furthermore, the selectivity tests confirmed that the designed probe was highly selective to mercury (II) cations among tested other divalent cations. Owing to its sensitivity and selectivity, this approach for Hg2+ ions detection can be utilized for the analysis of real water samples. Copyright © 2023 Tiwari, Yadav, Gupta, Narayan and Pandey.
Vancomycin-Conjugated Polyethyleneimine-Stabilized Gold Nanoparticles Attenuate Germination and Show Potent Antifungal Activity against Aspergillus spp.
(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Aishwarya Nikhil; Atul Kumar Tiwari; Ragini Tilak; Saroj Kumar; Prahlad Singh Bharti; Prem C. Pandey; Roger J. Narayan; Munesh Kumar Gupta
Antifungal drug resistance in filamentous fungi, particularly Aspergillus species, is increasing worldwide. Therefore, new antifungal drugs or combinations of drugs are urgently required to overcome this public health situation. In the present study, we examined the antifungal activity of vancomycin-functionalized AuNPs. These functionalized AuNPs were characterized, and their antifungal activity and associated killing mechanism were investigated using conventional methodologies against the conidia of A. fumigatus and A. flavus. The differential antifungal activity of vancomycin-functionalized Au-NPs against the conidia of Aspergillus species is dependent on structural differences in the conidial cell wall. The results demonstrated potent fungicidal activity against A. fumigatus, with a MIC value of 4.68 µg/mL, 93% germination inhibition, and 38.4% killing rate within 8 h of exposure. However, the activity against A. flavus was fungistatic; a MIC value of 18.7 µg/mL and 35% conidial germination inhibition, followed by 28.4% killing rate, were noted under similar conditions. Furthermore, endogenous reactive oxygen species (ROS) accumulation was 37.4 and 23.1% in conidial populations of A. fumigatus and A. flavus, respectively. Raman spectroscopy analysis confirmed the possible (but not confirmed) binding of functionalized AuNPs with the chitin and galactomannan components of the cell wall. A potential strategy that involves the exploration of antibacterial drugs using AuNPs as efficient drug carriers may also be appropriate for countering emerging drug resistance in filamentous fungi. © 2024 by the authors.