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Reduced Graphene Oxide Functionalized with Gold Nanostar Nanocomposites for Synergistically Killing Bacteria through Intrinsic Antimicrobial Activity and Photothermal Ablation
摘要： The exploration of multifunctional photothermal agent is important for antibacterial photothermal lysis, which has emerged as an effective approach to address the problem of pathogenic bacteria infection irrespective of the drug resistant effect. In the present work, a 2D reduced graphene oxide supported Au nanostar nanocomposite (rGO/AuNS) was prepared by the seed mediated growth method for synergistically killing multidrug resistant bacteria. Owing to the prickly and sharp-edge nanostructure, the rGO/AuNS displayed superior antibacterial activity probably due to the damaging of the cell walls or membranes. The cell viability of MRSA was as low as 32% when the MRSA were incubated with rGO/AuNS for 180 min in the absence of light. The 2D structure of the rGO/AuNS facilitated the strong binding affinity towards bacteria. Upon the 808 nm NIR laser irradiation, significant enhancement in bactericidal efficiency (complete death) was obtained due to the localized hyperthermal effect of rGO/AuNS. Moreover, the RGO/AuNS displayed promising biocompatibility. It indicates that the rGO/AuNS can be an alternative and effective dual functional photothermal agent for synergistically killing the multidrug resistant bacteria.
关键词： Reduced Graphene Oxide,Multidrug-resistant bacteria,Antibacterial photothermal lysis,Gold nanostars,Prickly nanostructure
更新于2025-09-23 15:22:29
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Measurement of Photosynthesis Using PAM Technology in a Purple Sulfur Bacterium <i>Thermochromatium tepidum</i> (Chromatiaceae)
摘要： We demonstrate that Blue-diode-based pulse amplitude modulation (PAM) technology can be used to measure the photosynthetic electron transport rate (ETR) of purple sulfur bacteria (Thermochromatium tepidum, Chromatiaceae). Previous studies showed that PAM technology could be used to estimate photosynthesis in purple nonsulfur bacteria and so PAM technology can be used to estimate photosynthesis of both kinds of purple photosynthetic bacteria. The absorptance of Thermochromatium films on glass fiber disks was measured and used to calculate actual ETR. ETR vs Irradiance curves fitted the waiting-in-line model (ETR = (ETRmax * E/Eopt) * exp (1-E/Eopt)). Yield (Y) was only 0.3–0.4. Thermochromatium saturates at 325 ± 13.8 μmol photons m?2 s?1 or ~15% sunlight and shows photoinhibition at high irradiances. A pond of Thermochromatium would exhibit classic surface inhibition. Photosynthesis is extremely low in the absence of an electron source: ETR increases in the presence of acetate (5 mol m?3) provided as an organic carbon source and also increases in the presence of sulfite (3 mol m?3) but not sulfide and is only marginally increased by the presence of Fe2?. Nonphotochemical quenching does occur in Thermochromatium but at very low levels compared to oxygenic photo-organisms or Rhodopseudomonads.
关键词： photosynthesis,PAM technology,photoinhibition,absorptance,Thermochromatium tepidum,purple sulfur bacteria,electron transport rate
更新于2025-09-23 15:22:29
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Differentiation of Taxonomically Closely Related Species of the Genus Acinetobacter Using Raman Spectroscopy and Chemometrics
摘要： In recent years, several efforts have been made to develop quick and low cost bacterial identification methods. Genotypic methods, despite their accuracy, are laborious and time consuming, leaving spectroscopic methods as a potential alternative. Mass and infrared spectroscopy are among the most reconnoitered techniques for this purpose, with Raman having been practically unexplored. Some species of the bacterial genus Acinetobacter are recognized as etiological agents of nosocomial infections associated with high rates of mortality and morbidity, which makes their accurate identification important. The goal of this study was to assess the ability of Raman spectroscopy to discriminate between 16 Acinetobacter species belonging to two phylogroups containing taxonomically closely related species, that is, the Acinetobacter baumannii-Acinetobacter calcoaceticus complex (six species) and haemolytic clade (10 species). Bacterial spectra were acquired without the need for any sample pre-treatment and were further analyzed with multivariate data analysis, namely partial least squares discriminant analysis (PLSDA). Species discrimination was achieved through a series of sequential PLSDA models, with the percentage of correct species assignments ranging from 72.1% to 98.7%. The obtained results suggest that Raman spectroscopy is a promising alternative for identification of Acinetobacter species.
关键词： species,bacteria,vibrational spectroscopy,typing,haemolytic clade
更新于2025-09-23 15:22:29
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A self-assembly/disassembly two-photo ratiometric fluorogenic probe for bacteria imaging
摘要： A fluorogenic probe for bacteria imaging was reported. The binding with anionic bacterial surfaces disassembled the self-assembly probe to turn-on the fluorescence and shift pyrene monomer/excimer ratiometric signals.
关键词： Self-assembly,Pyrene,Bacteria,Fluorogenic probe,Imidazolium
更新于2025-09-23 15:21:21
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Live E. coli bacteria label-free sensing using a microcavity in-line Mach-Zehnder interferometer
摘要： The paper presents the first study to date on selective label-free biosensing with a microcavity in-line Mach-Zehnder interferometer induced in an optical fiber. The sensing structures were fabricated in a single-mode fiber by femtosecond laser micromachining. In contrast to other studies of this sensing scheme, where only the sensitivity to refractive index changes in the cavity was investigated, this research used chemical surface treatment of the sensor to ensure detection specificity. Immobilized MS2 bacteriophages were applied as recognition elements specifically targeting live E. coli C3000 bacteria. It is shown that the sensor allows for real-time monitoring of biological phenomena taking place on the surface of the microcavity. The developed biosensor exhibits ultrahigh refractive index sensitivity of 15,000 nm/RIU and is capable of detecting live E. coli bacteria concentrations as low as 100 colony forming units (CFU)/mL in liquid volume as low as picoliters.
关键词： label-free biosensing,E. coli C3000 bacteria,refractive index sensitivity,MS2 bacteriophages,femtosecond laser micromachining,microcavity in-line Mach-Zehnder interferometer,optical fiber
更新于2025-09-23 15:21:21
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High-throughput laser generation of Si-nanoparticle based surface coatings for antibacterial applications
摘要： High-productivity regime of nanosecond IR-laser ablative generation of silicon colloidal solutions in water for anti-bacterial applications was found in terms of GW/cm2-level laser intensity and scanning velocity by measuring multi-shot ablative mass loss and extinction coefficients of the colloids as sub-linear and third-power intensity functions, respectively. This advantageous regime implies sub-linear mass loss versus laser intensity at the simultaneous third-power yield of nanoparticles, resulting from the subcritical-density, opaque ablative plasma regulating the sample ablation rate and the related plasma-mediated dissociation (dispergation) of the ablation products. In contrast, at higher intensities, there is a drastic increase in mass loss with the corresponding increased yield of (sub) micrometer-sized particles owing to intense plasma-driven expulsion of micro-scale melt droplets and the corresponding saturation of the extinction coefficient of the colloidal solutions because of their dynamic local “self-limiting” effect during the high-rate ablation. The optimal low-intensity regime for Si nanoparticle production demonstrates the monotonous correlated increase of mass loss and extinction coefficient in terms of increasing laser scanning velocity, indicating the diminished cumulative effects. Surface coatings prepared from the generated Si nanoparticles exhibit minor surface oxidation, as acquired as their elemental composition via energy-dispersive X-ray spectroscopy, making their contact angle for water droplets (≈51°) close to that of bare Si wafer (≈58°) with its nanometer-thick native oxide layer. Owing to good wetting, the nanoparticle-based surface coatings show strong antibacterial response regarding Gram-negative Pseudomonas auereginosa bacteria even despite their minor oxidative passivation.
关键词： Silicon nanoparticles,Colloids,Surface oxidation,Extinction coefficient,Wetting,Antibacterial tests,Gram-negative bacteria Pseudomonas auereginosa,Sub-critical ablative plasma,Nanosecond laser ablation,Mass loss
更新于2025-09-23 15:21:21
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Degradation of Ciprofloxacin and Inactivation of Ciprofloxacin Resistant E. Faecium during UV-LED (275 nm)/Chlorine Process
摘要： Ciprofloxacin and ciprofloxacin-resistant bacteria are emerging concerns that threaten public health due to the heavy use of antibiotics and the development of bacterial resistance in water environments. In this study, we examined an energy-efficient treatment driven by a UV-LED/chlorine reaction with UV-LED chip emitting UV275 nm to remove ciprofloxacin and ciprofloxacin-resistant bacteria in water. Ciprofloxacin degradation during the UV-LED/chlorine reaction followed pseudo-first-order kinetics, and the excessive chlorine dosage has a negative effect on ciprofloxacin removal. Alkaline pH showed the best efficiency for ciprofloxacin removal, and the reactive chlorine species (RCS) played a major role at alkaline pH values. The cleavages of piperazine, cyclopropyl, and quinolone moieties are considered as the principal degradation reactions in the UV-LED/chlorine reaction. Seven byproducts (m/z = 362.9262, 306.1246, 289.0995, 288.1504, 263.0825, 147.0657, and 1183.9977), two chlorinated compounds (chloroform and chlorate) and two anions (formate and nitrate ions) were observed as the identified byproducts. Toxicity of tentatively identified byproducts were estimated by using quantitative structure activity relationship (QSAR). The complete detoxification of D. magna was achieved when applying UV-LED/chlorine process into hospital wastewater containing CIP. The UV-LED/chlorine process showed the best disinfection ability of E. faecium compared to UV-LED photolysis, chlorination, and UV-LED/H2O2 reactions. A significantly lower EE/O value (6.63 × 10-2 kWh/m3/order) during the UV-LED/chlorine reaction was also observed. Our results indicate that the UV-LED/chlorine process can effectively degrade ciprofloxacin and inactivate ciprofloxacin-resistant bacteria.
关键词： toxicity,UV-LED,ciprofloxacin,byproducts,antibiotic-resistant bacteria,Chlorine
更新于2025-09-23 15:21:01
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A sensitive immunoassay for simultaneous detection of foodborne pathogens using MnO2 nanoflowers-assisted loading and release of quantum dots
摘要： In this study, a sensitive immunoassay using immunomagnetic nanobeads (MNBs), manganese dioxide nanoflowers (MnO2 NFs) and quantum dots (QDs) was developed for simultaneous detection of E. coli O157: H7 and Salmonella typhimurium. MnO2 NFs were synthesized, functionalized and incubated with QDs to obtain QDs@MnO2 nanocomposites, followed by modification with antibodies (pAbs) to obtain pAb-QDs@MnO2 nanocomposites (QM NCs). Target bacteria were first conjugated with MNBs and QM NCs to form MNB-bacteria-QM complexes. Then, QDs were quickly released from the complexes using glutathione to reduce MnO2 to Mn2+. Finally, fluorescent intensity at characteristic wavelength was measured by optical detector to determine target bacteria. This immunoassay could simultaneously and quantitatively detect E. coli from 1.5 × 101 to 1.5 × 106 CFU/mL with detection limit of 15 CFU/mL and Salmonella from 4.0 × 101 to 4.0 × 106 CFU/mL with detection limit of 40 CFU/mL in 2 h. The mean recovery for both bacteria in spiked chicken samples was ～96%.
关键词： Pathogenic bacteria,Quantum dots,Simultaneous detection,Manganese dioxide nanoflowers,Fluorescent immunoassay
更新于2025-09-23 15:21:01
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High-Throughput Fingerprinting of Rhizobial Free Fatty Acids by Chemical Thin-Film Deposition and Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry
摘要： Fatty acids (FAs) represent an important class of metabolites, impacting on membrane building blocks and signaling compounds in cellular regulatory networks. In nature, prokaryotes are characterized with the most impressing FA structural diversity and the highest relative content of free fatty acids (FFAs). In this context, nitrogen-fixing bacteria (order Rhizobiales), the symbionts of legumes, are particularly interesting. Indeed, the FA profiles influence the structure of rhizobial nodulation factors, required for successful infection of plant root. Although FA patterns can be assessed by gas chromatography—(GC-) and liquid chromatography—mass spectrometry (LC-MS), sample preparation for these methods is time-consuming and quantification suffers from compromised sensitivity, low stability of derivatives and artifacts. In contrast, matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) represents an excellent platform for high-efficient metabolite fingerprinting, also applicable to FFAs. Therefore, here we propose a simple and straightforward protocol for high-throughput relative quantification of FFAs in rhizobia by combination of Langmuir technology and MALDI-TOF-MS featuring a high sensitivity, accuracy and precision of quantification. We describe a step-by-step procedure comprising rhizobia culturing, pre-cleaning, extraction, sample preparation, mass spectrometric analysis, data processing and post-processing. As a case study, a comparison of the FFA metabolomes of two rhizobia species—Rhizobium leguminosarum and Sinorhizobium meliloti, demonstrates the analytical potential of the protocol.
关键词： bacteria,metabolic fingerprinting,matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS),barium monocarboxylates,free fatty acids (FFAs),chemical deposition technique,Langmuir film technology,rhizobia
更新于2025-09-23 15:21:01
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Bacteria functionalized gold nanoparticle matrix based fiber-optic sensor for monitoring heavy metal pollution in water
摘要： In the present study, E.coli B40 bacteria were explored as possible receptors on localized surface plasmon resonance (LSPR) based biosensor for sensing heavy metal ions viz. mercury (Hg2+) and cadmium (Cd2+) in water. The E.coli B40 bacteria were immobilized on gold nanoparticles (AuNP) coated fiber-optic probes by depositing two bi-layers of oppositely charged polyelectrolytes. The E.coli immobilized sensor probes were subjected to different concentrations of Hg2+ and Cd2+ ions, ranging from 0.5 ppb to 2000 ppb. These metal ions interact with the thiols and other surface groups present on the bacterial cells, resulting in the change of refractive index around AuNP coated sensor probes, thereby modulating the sensor response. The detection was performed by spiking de-ionized (DI) water and tap water with metal ions and the limit of detection was found to be 0.5 ppb. The proposed sensor could detect heavy metal ions within 10 min from a small sample (< 1 ml) and showed good selectivity towards heavy metal ions over other transition metal ions. Control studies performed using amino acids like cysteine as receptors were found to be less sensitive than the proposed scheme using bacterial cells.
关键词： polyelectrolytes,fiber-optic sensor,Bacteria,gold nanoparticles,heavy metal ions,localized surface plasmon resonance
更新于2025-09-23 15:21:01