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Ultrasensitive tantalum oxide nano-coated long-period gratings for detection of various biological targets
摘要： In this work we discussed a label-free biosensing application of long-period gratings (LPGs) optimized in refractive index (RI) sensitivity by deposition of thin tantalum oxide (TaOx) overlays. Comparing to other thin film and materials already applied for maximizing the RI sensitivity, TaOx offers good chemical and mechanical stability during its surface functionalization and other biosensing experiments. It was shown theoretically and experimentally that when RI of the overlay is as high as 2 in IR spectral range, for obtaining LPGs ultrasensitive to RI, the overlay’s thickness must be determined with subnanometer precision. In this experiment the TaOx overlays were deposited using Atomic Layer Deposition method that allowed for achieving overlays with exceptionally well-defined thickness and optical properties. The TaOx nano-coated LPGs show RI sensitivity determined for a single resonance exceeding 11,500 nm/RIU in RI range nD=1.335-1.345 RIU, as expected for label-free biosensing applications. Capability for detection of various in size biological targets, i.e., proteins (avidin) and bacteria (Escherichia coli), with TaOx-coated LPGs was verified using biotin and bacteriophage adhesin as recognition elements, respectively. It has been shown that functionalization process, as well as type of recognition elements and target analyte must be taken into consideration when the LPG sensitivity is optimized. In this work optimized approach made possible detection of small in size biological targets such as proteins with sensitivity reaching 10.21 nm/log(ng/ml).
关键词： protein detection,label-free biosensing,optical fiber sensor,tantalum oxide,bacteria detection,long-period grating,atomic layer deposition
更新于2025-11-28 14:23:57
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Bacteria induced pH changes in tissue-engineered human skin detected non-invasively using Raman confocal spectroscopy
摘要： Skin has a highly regulated pH environment of around pH 7.2 but with an acid barrier mantle of around pH 5.5. Trauma, inflammation, and infection are all thought to disrupt this pH environment but the lack of a non-invasive technique to measure pH within discrete locations within skin has hindered investigating what role pH plays in wound healing. In this study, a confocal Raman microspectroscopy method was used for measuring pH in a 3D tissue engineered model of human skin (TE-skin) and evaluated for its ability to detect changes in pH in response to wounding, inflammation and bacterial infection. The state of protonation of phosphate groups within the TE-skin was used to indicate pH in a non-destructive manner exploring depths of skin from the stratum corneum to 600 microns into the dermis. Deliberate wounding or inflammation (induced by IL-17) resulted in a loss of the acid mantle. Detailed scanning of TE-skin infected with Staphylococcus aureus or Pseudomonas aeruginosa revealed heterogeneous pH microenvironments ranging in size from 10 (cid:1) 10 to 50 (cid:1) 100 microns and ranging from pH 5 to 9. These microenvironments were not detected if an average pH for the TE-skin model was used.
关键词： bacteria,tissue-engineered,skin,pH
更新于2025-11-21 11:24:58
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Vancomycin functionalized WO3 thin film-based impedance sensor for efficient capture and highly selective detection of Gram-positive bacteria
摘要： In this study, we report a facile, reusable, and highly sensitive label-free impedance sensor for discriminating Gram-positive and Gram-negative bacteria. The impedance sensor was fabricated using gold interdigitated electrodes onto a tungsten oxide thin film. X-Ray diffraction confirmed the formation of polycrystalline tungsten oxide. Field emission scanning electron microscopy and atomic force microscopy revealed that tungsten oxide has a porous structure. Tungsten oxide was functionalized with vancomycin, a glycopeptide antibiotic known to have a specific interaction with the peptidoglycan layer of Gram-positive bacteria. fourier transform infrared microscopy and scanning electron microscopy were employed to test the morphological coating of vancomycin on interdigitated electrodes/ tungsten oxide sensor. The functionalized tungsten oxide sensor was highly efficient in the capture of Gram-positive bacteria. The impedance measurement was also sensitive to differentiate between viable and non-viable Gram-positive bacteria. Limit of detection 102 colony forming unit/ml, linear dynamic range 102 - 107 colony forming unit/ml under physiological conditions and reusable nature of this vancomycin coated impedance sensor provide a label-free strategy for quick, sensitive and highly selective detection of Gram-positive bacteria.
关键词： Vancomycin,WO3 thin film,Gram-positive bacteria,Impedance sensor
更新于2025-11-21 11:18:25
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A Fluorescent Supramolecular Biosensor for Bacterial Detection via Binding-Induced Changes in Coiled-Coil Molecular Assembly
摘要： The essential elements required for any sensors are a receptor, a signal converter, and a detector. Here, we report the construction of bacterial biosensors in which all of the required biosensor elements are furnished in one supramolecular assembly. The supramolecular biosensor is based on a double-layered octa-helical coiled-coil peptide assembly that contains tetravalent bioreceptors on the outer surface and environment-sensitive fluorophores in the core. The signal conversion takes advantage of the noncovalent and reversible nature of the self-assembled system, i.e., the multivalent binding of bacteria induces conformational changes in the supramolecular state, which is translated into differential fluorescence emissions. We show that fluorescent supramolecular biosensors (fSBs) can selectively detect E. coli over other bacteria. Because the fSBs were resistant to heat-induced denaturation, they retained their bacterial-sensing capability even at an elevated temperature (50 ℃). Biosensors based on responsive supramolecular assemblies can be further developed to detect various large and flat biological objects and biomacromolecules.
关键词： Escherichia coli,Supramolecule,Biosensor,Bacteria,Self-assembly,Peptide-based probe
更新于2025-11-21 11:08:12
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Soil Particles and Phenanthrene Interact in Defining the Metabolic Profile of Pseudomonas putida G7: A Vibrational Spectroscopy Approach
摘要： In soil, organic matter and mineral particles (soil particles; SPs) strongly influence the bio-available fraction of organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs), and the metabolic activity of bacteria. However, the effect of SPs as well as comparative approaches to discriminate the metabolic responses to PAHs from those to simple carbon sources are seldom considered in mineralization experiments, limiting our knowledge concerning the dynamics of contaminants in soil. In this study, the metabolic profile of a model PAH-degrading bacterium, Pseudomonas putida G7, grown in the absence and presence of different SPs (i.e., sand, clays and humic acids), using either phenanthrene or glucose as the sole carbon and energy source, was characterized using vibrational spectroscopy (i.e., FT-Raman and FT-IR spectroscopy) and multivariate classification analysis (i.e., PLS-DA). The different type of SPs specifically altered the metabolic profile of P. putida, especially in combination with phenanthrene. In comparison to the cells grown in the absence of SPs, sand induced no remarkable change in the metabolic profile of the cells, whereas clays and humic acids affected it the most, as revealed by the higher discriminative accuracy (R2, RMSEP and sensitivity) of the PLS-DA for those conditions. With respect to the carbon-source (phenanthrene vs. glucose), no effect on the metabolic profile was evident in the absence of SPs or in the presence of sand. On the other hand, with clays and humic acids, more pronounced spectral clusters between cells grown on glucose or on phenanthrene were evident, suggesting that these SPs modify the way cells access and metabolize PAHs. The macromolecular changes regarded mainly protein secondary structures (a shift from α-helices to β-sheets), amino acid levels, nucleic acid conformation and cell wall carbohydrates. Our results provide new interesting evidences that SPs specifically interact with PAHs in defining bacteria metabolic profiles and further emphasize the importance of studying the interaction of bacteria with their surrounding matrix to deeply understand PAHs degradation in soils.
关键词： phenanthrene,FTIR spectroscopy,soil particles,multivariate classification analysis,bacteria,metabolic profile,FT-Raman spectroscopy
更新于2025-11-14 15:16:37
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Photoluminescence carbon dot as a sensor for detecting of Pseudomonas aeruginosa bacteria: Hydrothermal synthesis of magnetic hollow NiFe2O4-carbon dots nanocomposite material
摘要： The purpose of this research is synthesis of photoluminescence nanoparticles for detection of Pseudomonas aeruginosa that is feasible for bio medial applications. Carbon nano-templates were prepared from soot by burning of almond as a green precursor. Then NiFe2O4 nanoparticles were synthesized on the carbon templates. For preparation of hollow structures, the product was calcinated for removing of carbon templates. Finally, carbon dots were synthesized on the hollow nickel ferrite cores by applying ethylene diamine and citric acid. Phase of the products was approved by X-ray diffraction (XRD), scanning electron microscopy (SEM) depict the morphology and transmission electron microscopy (TEM) probe the grain size and hollow structures of the nickel ferrite, carbon dot and nanocomposites. Fourier transform infrared (FT-IR) spectroscopy approved the purity of the nanostructures. Ultraviolet-visible (UV-Vis) absorption and photo-luminescence (PL) spectroscopy confirmed appropriate photo-luminescence under ultraviolet irradiation. Vibrating sample magnetometer (VSM) shows ferromagnetic property of the both hollow NiFe2O4 and nickel ferrite-carbon nanocomposite. This work presents a new nanostructure as green prepared photoluminescence sensor for detecting of Pseudomonas aeruginosa bacteria, lead and mercury ions. Outcomes confirm decreasing in photoluminescence intensity of the nanocomposite by enhancing of Pseudomonas aeruginosa, Pb(II) and Hg(II) ions. Antibacterial effect of NiFe2O4-carbon dot on the degradation of Pseudomonas aeruginosa bacteria was also examined.
关键词： Nanostructures,Carbon Dots,Magnetic,Photoluminescence,P. Aeruginosa Bacteria
更新于2025-09-23 15:23:52
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Physico-mechanical and antimicrobial properties of an orthodontic adhesive containing cationic curcumin doped zinc oxide nanoparticles subjected to photodynamic therapy
摘要： Background: Potential complications on the crown level during fixed orthodontic procedures are white spot, enamel demineralization and the tooth decay. This study evaluated the antimicrobial properties of an orthodontic adhesive incorporating cationic curcumin doped zinc oxide nanoparticles (cCur/ZnONPs), which can have the highest concentration of cCur/ZnONPs and shear bond strength (SBS) value simultaneously, on the against cariogenic bacteria including Streptococcus mutans, Streptococcus sobrinus, and Lactobacillus acidophilus. Materials and methods: Following synthesis and confirmation of cCur/ZnONPs, SBS and adhesive remnant index (ARI) of the test adhesives containing cCur/ZnONPs (1.2, 2.5, 5, 7.5, and 10% wt.) were measured using universal testing machine and stereomicroscope, respectively. After continuously rinsed (up to 180 day), the residual antimicrobial ability of modified adhesives which can have the highest concentration of cCur/ZnONPs and SBS value simultaneously were determined by disc agar diffusion (DAD), biofilm formation inhibition, and metabolic activity assays following photo-activation using light-emitting diode (LED) for 5 min against multispecies cariogenic biofilm-producing bacteria. Results: Adhesive with 7.5% wt. cCur/ZnONPs showed the highest concentration of cCur/ZnONPs and SBS value (14.89 ± 3.26 MPa, P < 0.05) simultaneously. No significant differences in ARI scores were found between the modified adhesive and control (Transbond XT without the cCur/ZnONPs). 7.5% wt. cCur/ZnONPs following photo-activation was not colonized by the test microorganisms and suppressed 100% metabolic activity of the test microorganisms up to 90 day compared to the control group (cCur/ZnONPs free LED irradiation; P < 0.05). In DAD assay, the reduction of photodynamic disinfection of the 7.5% wt. cCur/ZnONPs against test bacteria was positively associated to the time, in such a way that it was decreased significantly after 60 day. From days 120 onwards, microbial biofilm formation and metabolic activity was progressively increased on 7.5% wt. cCur/ZnONPs adhesive discs compared to the control group (cCur/ZnONPs free LED irradiation). Conclusions: Our findings highlight the photo-activated 7.5% wt. cCur/ZnONPs can serve as an orthodontic adhesive additive for control the cariogenic multispecies biofilm, and also to reduce their metabolic activity.
关键词： Cariogenic bacteria,Orthodontic adhesive,Antimicrobial photodynamic therapy,Cationic curcumin,Zinc oxide nanoparticles
更新于2025-09-23 15:23:52
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Development of a photocatalytic filter to control indoor air quality
摘要： Background: The aim of this work was the development and characterization of a photocatalytic filter for the treatment of indoor air, characterized by a low pressure drop. Methods: The filter (photocatalytic filter) was based on a polyester substrate additivated with active carbon (Carbotex 150-6), treated with a sol of titanium dioxide (Sol 121-AB; NextMaterials Ltd.) and illuminated with UV LEDs to induce photocatalytic activity. Results: Tests showed that this filter, used in a suitable device for air circulation with a very low noise level, had the ability to block solid particulates, to photocatalytically oxidize a major fraction of volatile organic compounds (VOCs) and deactivate all of the bacteria blocked on the filter, in contrast to traditional commercial air filters on which the bacteria remain viable. Conclusions: Activated charcoal filters treated with TiO2 and illuminated by UV LEDs were found to be extremely effective in killing bacteria and effective in decreasing VOC and total suspended particulates (TSP).
关键词： Bacteria,Titanium oxide,Photocatalysis,Filters,Total solid particulate,Volatile organic compounds
更新于2025-09-23 15:23:52
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Dual-Modal In Vivo Fluorescence/Photoacoustic Microscopy Imaging of Inflammation Induced by GFP-Expressing Bacteria
摘要： In this study, dual-modal fluorescence and photoacoustic microscopy was performed for noninvasive and functional in vivo imaging of inflammation induced by green fluorescent protein (GFP) transfected bacteria in mice ear. Our imaging results demonstrated that the multimodal imaging technique is able to monitor the tissue immunovascular responses to infections with molecular specificity. Our study also indicated that the combination of photoacoustic and fluorescence microscopy imaging can simultaneously track the biochemical changes including the bacterial distribution and morphological change of blood vessels in the biological tissues with high resolution and enhanced sensitivity. Consequently, the developed method paves a new avenue for improving the understanding of the pathology mechanism of inflammation.
关键词： GFP-expressing bacteria,fluorescence imaging,biosensor,photoacoustic microscopy,inflammation/infection
更新于2025-09-23 15:22:29
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Empirical system of image enhancement for digital microscopic pneumonia bacteria images
摘要： In this paper the image processing method is used to enhance the pneumonia bacteria images. This paper recognized the bacteria images based on two domains. The enhancement techniques used for bacteria image enhancement were median filter, wiener filter, single scale retinex and multiscale retinex. Image enhancement has a very important role in digital image processing. The median and wiener filters were used for grayscale image enhancement. Then single scale retinex and multiscale retinex were used for color image enhancement. Based on performance metrics identified median filter is suitable for bacteria images in grayscale image enhancement and multiscale retinex is suitable for bacteria color image enhancement (Tab. 2, Fig. 8, Ref. 21). Text in PDF www.elis.sk.
关键词： image processing,median filter,multiscale retinex,image enhancement,wiener filter,single scale retinex,Pneumonia bacteria
更新于2025-09-23 15:22:29