A point-of-care aptasensor based on the upconversion nanoparticles/MoS2 FRET system for the detection of Pseudomonas aeruginosa infection

The rapid detection of Pseudomonas aeruginosa (P. aeruginosa) is of great significance for the diagnosis of medical infection. In view of the above, a novel aptasensor based on fluorescence resonance energy transfer (FRET) was developed. It contained aptamer-coupled upconversion nanoparticles (UCNPs-apt) as a donor (excitation 980 nm) and molybdenum disulfide (MoS2) nanosheets as an acceptor. The upconversion fluorescence aptamer system was investigated to obtain the optimal parameters of MoS2 concentration, the incubation time of UCNPs-apt/MoS2 and P. aeruginosa, and pH. Based on the optimal parameters, a linear calibration equation (emission 654 nm) with a wide detection range 8.7 × 10 ~ 8.7 × 107 cfu/mL, a high coefficient of determination R2 0.9941, and a low limit of determination (LOD) 15.5 cfu/mL were established. The method was validated with P. aeruginosa infected foci of mouse wound. The advantage of this aptasensor is that analysis results can be obtained  within 1.5 h, which was much faster than that of the standard method (18-24 h). Furthermore, combined with a portable instrument, it can be used as a point-of-care testing for the early detection of P. aeruginosa infection, which is useful for selecting the correct antibiotics to achieve good therapeutic effects. Additionally, it also has a broad application prospect in food and environmental areas.

Rapid detection of Pseudomonas aeruginosa using a DNAzyme-based sensor

In the present study, a DNAzyme was screened in vitro through the use of a DNA library and crude extracellular mixture (CEM) of Pseudomonas aeruginosa. Following eight rounds of selection, a DNAzyme termed PAE-1 was obtained, which displayed high rates of cleavage with strong specificity. A fluorescent biosensor was designed for the detection of P. aeruginosa in combination with the DNAzyme. A detection limit as low as 1.2 cfu/ml was observed. Using proteases and filtration, it was determined that the target was a protein with a molecular weight of 10 kDa-50 kDa. The DNAzyme was combined with a polystyrene board to construct a simple indicator plate sensor which produced a color that identified the target within 10 min. The results were reliable when tap water and food samples were tested. The present study provides a novel experimental strategy for the development of sensors based on a DNAzyme to rapidly detect P. aeruginosa in the field.

Gold nanoparticle-based immunochromatographic assay for detection Pseudomonas aeruginosa in water and food samples

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An ICA was developed for P. aeruginosa detection.

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The ICA strip showed a limit of detection of 2.41 × 10⁴ CFU/mL.

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The ICA could be applied to detect P. aeruginosa in water and food samples.

Pseudomonas aeruginosa (P. aeruginosa) is the common infection-causing bacterial pathogen. Conventional methods for the detection of P. aeruginosa are time-consuming, and therefore, a more rapid analytical method is required. Here, monoclonal antibodies (Mabs) against P. aeruginosa (CICC 10419) were prepared and based on paired Mabs, an immunochromatographic assay (ICA) was developed. The ICA strip showed a limit of detection of 2.41 × 10⁴ CFU/mL and the linear range of detection was 3.13 × 10⁴-1.0 × 10⁶ CFU/mL. No cross-reactivity was observed when other common Gram-negative and Gram-positive bacteria were used. The analytical performance of the ICA strip indicated that the developed ICA had good specificity and stability. Moreover, the feasibility of the ICA strip was verified by detecting P. aeruginosa (CICC 10419) in spiked water and food samples. The ICA strip could detect samples contaminated with a low-level of P. aeruginosa (CICC 10419) after 8 h enrichment.

Multifunctional Receptor with Tunable Selectivity: A Comparative Recognition Profile of Organic Nanoparticles with Carbon Dots

The exponential growth in the research field of water pollution control demands the evolution of novel sensing materials for regulation and quantification of metals ions. Within this context, the current work reports a new strategy for the synthesis of carbon dots from the hydrothermal treatment of organic nanoparticles. The organic nanoparticles are found to be selective towards Cs(I) ions with a detection limit of 5.3 nM, whereas the highly fluorescent carbon dots are found to be selective towards Ag(I) ions with a detection limit of 4.8 nM. Both sensing systems illustrate rapid sensing with a working pH range from 4-9. The interfacial molecular restructuring of the sensing systems in the aqueous phase has been investigated in the absence and presence of targeted metal ions using a sum frequency generation vibrational spectroscopic tool. The practical applicability of the sensors was checked in environmental samples. This work opens new avenues for the exploration of temperature-guided sensing modulation in nanomaterials.

Dual-aptamers labeled polydopamine-polyethyleneimine copolymer dots assisted engineering a fluorescence biosensor for sensitive detection of Pseudomonas aeruginosa in food samples

To ensure the food security and protect public health, development of rapid and reliable approaches to detecting foodborne pathogens is of great significance. In this study, polydopamine-polyethyleneimine (PDA-PEI) copolymer dots are prepared via the self-polymerization of dopamine and cross-linking with branched PEI at room temperature. The PDA-PEI copolymer dots are very stable against photobleaching, extreme pH, as well as high ionic strength. They are used as a fluorescent probe to fabricate a biosensor for rapid and sensitive detection and quantification of Pseudomonas aeruginosa (P. aeruginosa). In the biosensor, dual-aptamers of P. aeruginosa are used to label PDA-PEI copolymer dots. Compared to single aptamer labeled PDA-PEI dots, the dual-aptamers labeled PDA-PEI dots endow the biosensor with enhanced sensitivity for target pathogen. The fluorescence biosensor demonstrates a wide linear response to P. aeruginosa in the concentration range of 10¹-10⁷ cfu mL^-1 with acceptable selectivity. The limit of detection is calculated to be 1 cfu mL^-1. The whole detection process can be finished in 1.5 h. The feasibility of the fabricated biosensor is verified by successful determination of P. aeruginosa in skim milk, orange juice, and popsicle samples. The biosensor provides an alternative and attractive platform for rapid and sensitive detection of bacteria in food products.

Impedimetric aptasensor for Pseudomonas aeruginosa by using a glassy carbon electrode modified with silver nanoparticles

An aptasensor is described for the ultrasensitive detection of Pseudomonas aeruginosa (P. aeruginosa). A glassy carbon electrode (GCE) was first modified by electrodeposition of silver nanoparticles (AgNPs). Immobilization of NH₂-aptamer was covalently attached to the AgNP/GCE surface. The morphology, distribution and size of the sensor were characterized by field emission scanning electron microscopy. Cyclic voltammetry and electrical impedance spectroscopy were used to study conductivity of the aptasensor and the electrochemical properties. Detection of P. aeruginosa was carried out by evaluation of the charge transfer resistance after and before the adding of P.aeruginosa and by using the hexacyanoferrate redox system as an electrochemical probe. The impedance increases on going from 10² to 10⁷ CFU·mL^-1 concentrations of P. aeruginosa, and the detection limit is 33 CFU·mL^-1 (for S/N = 3). The assay was successfully applied for the determination of P. aeruginosa in spiker serum samples. Graphical abstract Schematic representation of an impedimetric assay for Pseudomonas aeruginosa by using a [Fe(CN)₆]^3-/4- probe based on immobilization of amino-modified aptamer onto a glassy carbon electrode (GCE) modified with silver nanoparticles (AgNPs): Incubation with P. aeruginosa leads to an increase of the charge-transfer resistance.

Designing of New Optical Immunosensors Based on 2-Amino-4-(anthracen-9-yl)-7-hydroxy-4H-chromene-3-carbonitrile for the Detection of Aeromonas hydrophila in the Organs of Oreochromis mossambicus Fingerlings

A one-pot greener methodology has been adopted for the synthesis of a simple 4H-chromene core-based fluorescent tag of (S)-2-amino-4-(anthracen-9-yl)-7-hydroxy-4H-chromene-3-carbonitrile (AHC), and its structure has been analyzed using NMR spectroscopy. The physicochemical properties of AHC were well-studied by UV-vis and fluorescent spectroscopy techniques. As a result of excellent emitting property (ϕ ≈ 0.75), it has been coupled with anti-AH through amide linkage, and the AHC-tagged anti-AH has been used as an immunoassay for the selective detection of Aeromonas hydrophila in the presence of interfering pathogens. Under optimized conditions, immunosensors could successfully quantify A. hydrophila from 4 to 736 CFU/mL, and the LOD was 2 CFU/mL. Saliently, the immunoassay has been successfully demonstrated for the analysis of A. hydrophila in the organs of Oreochromis mossambicusfingerlings, and results have shown a very good agreement with our optimized neat AH fluorimetric titration results.

Aptamer-mediated colorimetric and electrochemical detection of Pseudomonas aeruginosa utilizing peroxidase-mimic activity of gold NanoZyme

Despite of various advancements in biosensing, a rapid, accurate, and on-site detection of a bacterial pathogen is a real challenge due to the lack of appropriate diagnostic platforms. To address this unmet need, we herein report an aptamer-mediated tunable NanoZyme sensor for the detection of Pseudomonas aeruginosa, an infectious bacterial pathogen. Our approach exploits the inherent peroxidase-like NanoZyme activity of gold nanoparticles (GNPs) in combination with high affinity and specificity of a Pseudomonas aeruginosa-specific aptamer (F23). The presence of aptamer inhibits the inherent peroxidase-like activity of GNPs by simple adsorption on to the surface of GNPs. However, in the presence of cognate target (P. aeruginosa), owing to the high affinity for P. aeruginosa, the aptamer leaves the GNP surface, allowing GNPs to resume their peroxidase-like activity, resulting in oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). As TMB is an electrochemically active species, we have been able to translate the NanoZyme-based method into an ultrasensitive electrochemical assay using disposable carbon screen-printed electrode. This approach is highly sensitive and allows us to rapidly detect P. aeruginosa with a low-end detection limit of ~ 60 CFU/mL in water within 10 min. This generic aptamer-NanoZyme-based electrochemical sensing strategy may, in principle, be applicable for the detection of various other bacterial pathogens.

Disaggregation-induced ESIPT: a novel approach towards development of sensors for hyperglycemic condition

An oxazolonapthoimidazo[1,2-a]pyridine-based fluorescence probe ONIP1 was designed and synthesized via multicomponent reaction. ONIP1 was able to distinguish human serum albumin (HSA) from and glycated-HSA via modulation of AIEE- and ESIPT-based dual channel emission properties.

Organic Fluorescent Dye-based Nanomaterials: Advances in the Rational Design for Imaging and Sensing Applications

Self-assembled fluorescent nanomaterials based on small-molecule organic dyes are gaining increasing popularity in imaging and sensing applications over the past decade. This is primarily due to their ability to combine spectral properties tunability and biocompatibility of small molecule organic fluorophores with brightness, chemical and colloidal stability of inorganic materials. Such a unique combination of features comes with rich versatility of dye-based nanomaterials: from aggregates of small molecules to sophisticated core-shell nanoarchitectures involving hyperbranched polymers. Along with the ongoing discovery of new materials and better ways of their synthesis, it is very important to continue systematic studies of fundamental factors that regulate the key properties of fluorescent nanomaterials: their size, polydispersity, colloidal stability, chemical stability, absorption and emission maxima, biocompatibility, and interactions with biological interfaces. In this review, we focus on the systematic description of various types of organic fluorescent nanomaterials, approaches to their synthesis, and ways to optimize and control their characteristics. The discussion is built on examples from reports on recent advances in the design and applications of such materials. Conclusions made from this analysis allow a perspective on future development of fluorescent nanomaterials design for biomedical and related applications.

Self-assembled organic nanoparticles of benzimidazole analogue exhibit enhanced uptake in 3D tumor spheroids and oxidative stress induced cytotoxicity in breast cancer

Organic nanoparticles (ONPs) possess great research interests for their promising effects in the enhancement of bioactivity including anticancer activity with less toxicity. The present study describes the preparation, characterization and biological evaluation of aqueous phase ONPs of potent 1,2-disubstituted benzimidazole derivative (BZ6) for anticancer activity. BZ6-ONPs were characterized through UV-absorption and fluorescence spectroscopic analysis for their photo-physical properties. DLS, TEM and SEM studies were carried out for morphological and structural analysis. Cytotoxicity determination on a panel of four different cancer cell lines (MCF-7, MiaPaca-2, HT-29 and HCT-116) revealed that the BZ6-ONPs show highest activity in human breast cancer MCF-7 cells. Surprisingly, the BZ6-ONPs were found to be non-toxic towards normal breast epithelial fR2 cells. Additionally, the FITC-ONPs showed enhanced uptake in 3D tumor spheroids of MCF-7 cells compared to the free FITC. BZ6-ONPs strongly halted cell proliferation and induced apoptosis, possibly through oxidative stress-mediated reactive oxygen species (ROS) generation and loss of mitochondrial membrane potential (MMP) in MCF-7 cells. Moreover, molecular mechanism-based studies revealed that BZ6-ONPs downregulated AKT/NF-κB/vimentin/survivin-mediated oncogenic signaling pathway promoting cell proliferation and malignancy. In a nutshell, BZ6-ONPs are therapeutically efficacious, which needs further development as a treatment option in human mammary gland carcinomas.

Aminoazole-Based Diversity-Oriented Synthesis of Heterocycles

The comprehensive review contains the analysis of literature data concerning reactions of heterocyclization of aminoazoles and demonstrates the application of these types of transformations in diversity-oriented synthesis. The review is oriented to wide range of chemists working in the field of organic synthesis and both experimental and theoretical studies of nitrogen-containing heterocycles.

Selective capture and sensitive fluorometric determination of Pseudomonas aeruginosa by using aptamer modified magnetic nanoparticles

A fluorometric assay is described for the detection of the food pathogen Pseudomonas aeruginosa (P. aeruginosa). It is based on the hybridization of aptamer and fluorescein-labeled complementary DNA (FAM-cDNA) in combination with magnetic separation. In the absence of P. aeruginosa, FAM-cDNA is assembled on the surface of aptamer modified magnetic particles (MNPs) via hybridization between aptamer and cDNA. Upon addition of P. aeruginosa, FAM-cDNA is replaced by the bacteria and released from the MNPs since the aptamer preferentially binds to bacteria. After magnetic separation, the amount of bacteria can be quantified by determination of the fluorescence intensity (λexc/em = 494/525 nm) of the supernatant containing the released FAM-cDNA. This kind of assay allows for both selective enrichment and sensitive fluorometric determination of bacteria in a single step. The assay has a response to the logarithm of P. aeruginosa concentration that is linear in the range between 10 and 10⁸ cfu·mL^-1, with a detection limit as low as 1 cfu·mL^-1. The detection process can be finished within <1.5 h. The feasibility of the assay was verified by detecting P. aeruginosa in spiked food samples. Graphical abstract Hybridization of aptamer and carboxyfluorescein labeled complementary DNA is combined with magnetic separation for detection of as low as 1 cfu·mL^-1 Pseudomonas aeruginosa. This kind of assay allows for both selective enrichment and sensitive fluorometric determination of bacteria in a single step.

Cobalt complexes of Biginelli derivatives as fluorescent probes for selective estimation and degradation of organophosphates in aqueous medium

Bonding between metal complexes of Biginelli derivatives and organophosphates leads to enhancement of emission intensity.

Novel Pyrimidine Tagged Silver Nanoparticle Based Fluorescent Immunoassay for the Detection of Pseudomonas aeruginosa

A simple pyrimidine-based fluorescent probe (R)-4-(anthracen-9-yl)-6- (naphthalen-1-yl)-1,6-dihydropyrimidine-2-amine (ANDPA) was synthesized through the greener one pot reaction and characterized by IR, NMR, and ESI-Mass. Glucose stabilized silver nanoparticles (Glu-AgNPs) were also synthesized and characterized using UV, IR, XRD, SEM, and TEM. When ANDPA was tagged with Glu-AgNPs, the fluorescent intensity of ANDPA decreased drastically. When the monoclonal antibody (Ab) [immunoglobulin G (IgG)] of Pseudomonas aeruginosa (PA) was attached with ANDPA/Glu-AgNPs, the original intensity of the probe was recovered with minimal enhancement at 446 nm. On further attachment of PA with ANDPA/Glu-AgNPs/PA, the fluorescence intensity of the probe was enhanced obviously at 446 nm with red shift. This phenomenon was further supported by SEM and TEM. The linear range of detection is from 8 to 10^-1 CFU/mL, and LOD is 1.5 CFU/mL. The immunosensor was successfully demonstrated to detect Pseudomonas aeruginosa in water, soil, and food products like milk, sugar cane, and orange juices.

Synthesis and photophysical study of new fluorescent proton transfer dihydropyrimidinone hybrids as potential candidates for molecular probes

New photoactive hybrid dihydropyrimidinones were achieved by the Biginelli multicomponent reaction.

Benzimidazolium-Based Self-Assembled Fluorescent Aggregates for Sensing and Catalytic Degradation of Diethylchlorophosphate

The unregulated use of chemical weapons has aroused researchers to develop sensors for chemical warfare agents (CWA) and likewise to abolish their harmful effects, the degradation through catalysis has great advantage. Chemically, the CWAs are versatile; however, mostly they contain organophosphates that act on inhibition of acetyl cholinesterase. In this work, we have designed and synthesized some novel benzimidazolium based fluorescent cations and their fluorescent aggregates were fabricated using anionic surfactants (SDS and SDBS) in aqueous medium. The prepared fluorescent aggregates have shown aggregation induced emission enhancement, which was further used as detection of chemical warfare agent in aqueous medium. The aggregates (Benz-2/SDBS and Benz-3/SDBS) have shown significant changes in emission profile upon interaction with diethylchlorophosphate. Contrarily, the pure dipodal receptor Benz-4 has not shown any response in emission after interaction with organophosphate, and consequently, it was concluded that benzimidazolium cation plays a decisive role in sensing. The mechanism of sensing was fully validated using ³¹P NMR spectroscopy as well as GC-MS, which highlights the transformation of diethylchlorophosphate into diethylhydrogen phosphate. The aggregates selectively interact with diethylchlorophosphate over other biological important phosphates.

A Biginelli-based organic nanoprobe for simultaneous estimation of tyramine and 1,2-diaminopropane: application in real samples

An Ag(i) complex of organic nanoparticles has been developed for the detection of biogenic amines in milk and wine samples.

Selective recognition of lithium(i) ions using Biginelli based fluorescent organic nanoparticles in an aqueous medium

Detection of lithium ions using fluorescent organic nanoparticles.