This innovative, label-free approach offers a simple and reliable method for antibiotic susceptibility testing, with a detection limit (initial bacterial count) of 1.67×107 CFU/mL, without requiring expensive reagents or equipment.
Abstract
Antimicrobial resistance has emerged as a significant threat to global public health, necessitating accurate and rapid detection methods. To address this need, a colorimetric nanobiosensor was developed that exploits antibiotic-induced metabolic changes in bacteria, detected via the redox-dependent activity of a peroxidase-mimicking nanozyme (γ-Fe₂O₃@Prussian blue). This study aimed to differentiate resistant from susceptible E. coli strains and determine the minimum inhibitory concentration for susceptible ones using this novel principle. The experiments were conducted on two susceptible and two resistant strains of E. coli along with antibiotics, including ampicillin, cefazolin, ceftriaxone, and kanamycin. The γ-Fe2O3@PB NPs were characterized using UV-vis spectroscopy, dynamic light scattering (DLS), X-ray diffraction (XRD), transmission electron microscopy, and Fourier-transform infrared spectroscopy (FTIR). The synthesis of cubic crystalline nanoparticles with average crystallite size and hydrodynamic size of 31 nm and 219 nm, respectively, was confirmed. Upon adding H₂O₂ and the chromogenic substrate TMB to the bacterial culture supernatant, the intensity of the blue color (measured at 652 nm) in sensitive strains correlated with antibiotic concentrations. Compared to sub-MIC concentrations, a significant and sharp increase in absorbance at 652 nm was observed at the MIC, and similarly high absorbance levels were maintained at higher concentrations. By comparing the absorbance levels below and at the MIC, the MIC range can be determined. In contrast, for resistant strains, the intensity of the produced color remained nearly constant across different antibiotic concentrations. This innovative, label-free approach offers a simple and reliable method for antibiotic susceptibility testing. It achieves results in approximately 4 hours, with a detection limit (initial bacterial count) of 1.67×107 CFU/mL, without requiring expensive reagents or equipment.
The rapid emergence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae has significantly limited the effectiveness of conventional antibiotics, highlighting the urgent need for alternative antimicrobial agents. In the present study, silver nanoparticles (AgNPs) were green synthesized using Saussurea costus root extract as a natural reducing and stabilizing agent. The biosynthesized AgNPs were comprehensively characterized by UV–visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential analysis, and energy-dispersive X-ray spectroscopy (EDX), confirming the successful formation of stable, crystalline, predominantly spherical nanoparticles. TEM and DLS analyses demonstrated nanoscale particle dimensions, while the negative zeta potential indicated favorable colloidal stability. The antibacterial activity of the synthesized AgNPs was evaluated against clinical ESBL-producing E. coli and K. pneumoniae isolates using agar well diffusion, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-kill assays. The AgNPs exhibited pronounced concentration-dependent antibacterial activity, producing clear inhibition zones and low MIC and MBC values against both pathogens. Time-kill analysis further demonstrated rapid bactericidal activity, with increasing nanoparticle concentrations resulting in enhanced bacterial killing over time. Cytocompatibility evaluation using primary human dermal fibroblasts (HDFa) revealed acceptable cell viability within the antibacterial concentration range, supporting the preliminary biocompatibility of the biosynthesized nanoparticles. Collectively, these findings demonstrate that S. costus-mediated AgNPs possess favorable physicochemical properties, potent in vitro antibacterial activity against clinically important ESBL-producing pathogens, and promising preliminary cytocompatibility. The study highlights the potential of S. costus as a sustainable plant source for green nanoparticle synthesis and provides a basis for the future development of plant-mediated antimicrobial nanomaterials. Nevertheless, additional investigations, including mechanistic studies, long-term stability assessment, comprehensive biosafety evaluation, and in vivo validation, are required before biomedical or clinical translation can be considered.
R. Hamasalih· Journal of Genetic Engineeri...· 0 citations
Multidrug-resistant (MDR) bacteria pose a major global health threat, necessitating the development of novel therapeutic strategies for wound infections. Gelidiella acerosa (G. acerosa), a red marine alga rich in bioactive compounds, was investigated for the green synthesis of silver nanoparticles (AgNPs) and their pharmacological potential against MDR bacterial pathogens. GC-MS analysis confirmed the presence of bioactive phytoconstituents in the aqueous extract of G. acerosa. The synthesized AgNPs were characterized using UV-Vis spectroscopy, FT-IR, SEM, XRD, EDX-mapping, AFM, DLS, and zeta potential analyses. Antibacterial activity was evaluated by zone-of-inhibition, minimum inhibitory concentration, minimum bactericidal concentration, AO/PI confocal imaging, scanning electron microscopy, and protein leakage assays. Characterization confirmed the formation of stable, crystalline, spherical AgNPs with a surface plasmon resonance peak at 417 nm, a hydrodynamic diameter of 172.3 nm (PDI 0.3133), and a zeta potential of 24.94 mV. Acinetobacter baumannii_SN1 and Pseudomonas aeruginosa_SN2 isolated from wound infections were identified by 16S rRNA gene sequencing. The biosynthesized AgNPs exhibited significant antioxidant, antidiabetic, and antibacterial activities against both MDR isolates. Mechanistic studies demonstrated increased membrane permeability, disruption of bacterial membrane integrity, and enhanced protein leakage following AgNPs treatment. The biosynthesized AgNPs exhibited potent antibacterial activity against multidrug-resistant wound pathogens by disrupting bacterial membrane integrity, along with significant antioxidant and antidiabetic properties. These findings suggest that G. acerosa AgNPs represent a promising alternative therapeutic strategy for the management of MDR bacterial wound infections.
R. Snega, Aruchamy Mohanprasanth, Jeyasingh Immanuel Suresh et al.· Microbial Pathogenesis· 0 citations
The rapid emergence of multidrug-resistant Staphylococcus aureus (MRSA), specifically, methicillin-resistant strains, has become a global health concern. Biofilm-forming ability, enhanced virulence and resistance to multiple antibiotics have challenged treatment strategies. Therefore, immediate attention is necessary to design alternative therapeutic strategies including nanotechnology-based solutions, novel drug targets, and anti-virulence strategies, to combat this global public health threat. Findings of this study elucidates the binding interaction and inhibition potential of zinc oxide nanoparticles (ZnONPs) biosynthesized using an endophytic isolate obtained from Hibiscus rosa-sinensis and identified as Penicillium citrinum using morphology and ITS rRNA gene sequencing. The comprehensive characterization of biosynthesized ZnONPs was done using UV- visible spectrophotometry, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential analysis. XRD and TEM analyses revealed the ZnONPs with spherical to elliptical shape with mean size of ~58 nm. The FTIR analysis confirmed the functional groups responsible for stabilizing and capping of ZnONPs. The biosynthesized ZnONPs displayed colloidal stability with a mean hydrodynamic diameter of 240.4 nm with a ζ-potential of −13 mV, as revealed in Dynamic light scattering (DLS) studies. The anti-staphylococcal studies of ZnONPs revealed an excellent antibacterial activity (22 ± 1.42) with a minimum inhibitory concentration (MIC) of 1000 µg/mL and demonstrated time-dependent bactericidal effects as revealed in time-kill assay. In addition, ZnONPs inhibited biofilm formation in a concentration-dependent manner, with highest reduction (68.7% ± 1.12%) in biofilm biomass, as revealed in a dye-based assay, accompanied by suppression of metabolic activity in biofilm-embedded cells. Importantly, ZnONPs displayed excellent inhibitory activities against the key virulence-associated exoenzymes, including lipase (IC₅₀ ≈ 380 ± 1.12) and hyaluronidase (IC₅₀ ≈ 330 ± 1.12 µg/mL). The cytotoxicity assessment using human red blood cells (hRBCs) revealed negligible haemolytic activity (< 2%) at biologically effective concentrations, confirming their safety and hemocompatibility. Considering the green synthesis, biocompatible nature and outstanding anti-staphylococcal potential, the endophyte derived ZnONPs showcases their potential as a sustainable nanotechnology-based alternative to conventional antimicrobial strategies against biofilm-associated infections of S. aureus.
Amruta A. Joshi, V. M. Songire, Ravindra H. Patil· Bioscience Nanotechnology· 1 citation
This study reports the green synthesis of silver nanoparticles (PV-Ag NPs) using a pigment-producing environmental fungus, Penicillium verrucosum (PV) RPF011, as a biological reducing and stabilizing agent. The formation of nanoparticles was initially evidenced by a distinct color change from light to dark brown, corresponding to the reduction of Ag⁺ ions, and was further confirmed by UV–visible spectroscopy showing a characteristic surface plasmon resonance peak at 433 nm. Fourier transform infrared (FTIR) analysis indicated the involvement of proteinaceous biomolecules in the reduction and capping processes, ensuring nanoparticle stability. X-ray diffraction (XRD) patterns revealed the crystalline nature of the synthesized nanoparticles, while high-resolution transmission electron microscopy (HR-TEM) analysis demonstrated that the PV-Ag NPs were predominantly spherical and polydisperse, with an average particle size of 78 ± 2 nm. The biologically synthesized nanoparticles exhibited potent antibacterial activity against clinically relevant pathogens, including Escherichia coli, Staphylococcus aureus, and Klebsiella pneumoniae. Furthermore, in vitro cytotoxicity assays revealed significant anticancer activity against the human lung carcinoma A549 cell line, with an IC50 value of 53.22 ± 1.5 µg/mL. The enhanced bioactivity of PV-Ag NPs can be attributed to their nanoscale dimensions and the presence of bioactive capping agents derived from the fungal extract. Overall, the findings highlight the potential of P. verrucosum-mediated silver nanoparticles as an eco-friendly and cost-effective nanoplatform with dual therapeutic applications in antimicrobial and anticancer treatments. This study underscores the promise of fungal-mediated nanotechnology in developing novel nano-drug formulations for managing infectious diseases and lung cancer.
Silver nanoparticles (AgNPs) are promising therapeutic agents against multidrug‐resistant (MDR) bacterial infections and cancer. The biogenic AgNPs were synthesized from
Argyreia speciosa (
As) leaf extract and characterized using UV–vis spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM)‐energy‐dispersive x‐ray spectroscopy (EDX), x‐ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT‐IR). The synthesized As‐AgNPs had a spherical shape, a crystalline morphology, showed a surface plasma resonance (SPR) peak at 440 nm, a hydrodynamic size of 61.8 nm, and a zeta potential of −24.7 mV. As‐AgNPs demonstrated potent antibacterial activity against MDR strains,
Escherichia coli, Klebsiella pneumoniae, Enterococcus faecalis
, and
Staphylococcus aureus
, exhibiting significantly greater zones of inhibition (16–18 mm) than AgNO
3
. Increased lipid and protein oxidation, decreased activity of catalase (CAT), superoxide dismutase (SOD), and reduced glutathione (GSH) levels in bacterial cells at concentrations of 0.32, 0.64, and 1.28 µg/mL, as compared to the control, suggest that As‐AgNP induces oxidative stress. Anticancer activity was evaluated by assessing cytotoxicity, ROS levels, apoptosis, and cytokine release in A549 cells. As‐AgNP significantly increased cytotoxicity (IC
50
1.99 µg/mL) and ROS. Increased sub G0/G1 cell population and
BAX/BCL2
ratio in As‐AgNP‐treated cells indicated apoptotic cell death. Further, As‐AgNP at sublethal concentrations modulated inflammatory cytokine levels. Overall, in vitro bactericidal and cytotoxic results support As‐AgNP as a potential antimicrobial and anticancerous agents, thereby paving the way for further in vivo investigations.
Aakash Shukla, Swapnil Tripathi, D. Parmar et al.· ChemistrySelect· 0 citations
