Browsing by Author "Roger Jagdish Narayan"

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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.
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.
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.
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.