Mn2+-modified black phosphorus nanosensor for detection of exosomal microRNAs and exosomes.

The development and performance of a DNA probe adsorbing Mn2+-modified black phosphorus (BP@Mn2+/DNA) hybrid nanosensor is reported that enables rapid detection of cancer-derived exosomal microRNAs (miRNAs) and exosomes. This two-dimensional (2D) nanosensor can spontaneously penetrate the lipid bilayer of exosome membranes owing to its ultra-thin geometry. Subsequently, the adsorbed probe specifically hybridizes with the target miRNA and then dissociates from the nanosensor surface, generating fluorescent signals. Therefore, the BP@Mn2+/DNA nanosensor can differentiate between colorectal cancer (CRC) cell-derived exosomes and those derived from intestinal epithelial cells through sensing of exosomal miRNAs. Furthermore, when the epithelial cell adhesion molecule (EpCAM) aptamer is adsorbed onto BP@Mn2+ instead of the miRNA probe, the nanosensor is able to distinguish exosomes derived from the plasma of CRC patients from those of healthy controls by the recognition ability of the EpCAM aptamer. By utilizing this nanosensor, we were able to effectively differentiate cancer-derived exosomes through the direct detection of miRNA-21 within the exosomes, as well as the identification of specific exosomal membrane proteins. This nanosensor design paves the way for the development of rapid and efficient cancer-derived exosomal miRNA and exosome biosensing nanoplatforms.

Fluorescent nucleotide-lanthanide nanoparticles for highly selective determination of picric acid.

A new method based on coordination polymer nanoparticles (CPNs) derived from nucleotides and Tb3+ ions (GMP/Tb) for the selective and sensitive determination of aqueous 2,4,6-trinitrophenol (TNP) (picric acid) is established. The fluorescence of GMP/Tb nanoparticles is effectively quenched by TNP via photo-induced charge transfer (PCT), thus achieving its selectivity toward TNP over other nitroaromatic explosives. The decreased fluorescence of GMP/Tb shows a good linear relationship to the concentrations of TNP ranging from 5.0 to 40.0 µM, and the limit of detection is 26.0 nM (5.96 ppb). The proposed GMP/Tb probe also achieves satisfactory results in real samples. The obtained recoveries of this method in river water samples are in the range 93.15-106.10%. The relative standard deviation (RSD) are 0.57 to 1.01% based on three repeated determinations. This fabricated detector provides a feasible path for determination of ppb-level TNP in natural water samples, which can help humans to avoid TNP-contaminated drinking water. Graphical abstract.

Mesoporous MIP-capped luminescent MOF as specific and sensitive analytical probe: application for chlorpyrifos.

Specific recognition of organophosphate pesticides (OPs) is a significant challenge for analytical researchers. Herein, surface imprinted terbium-based luminescent metal-organic framework (MOF-76) are presented as a highly specific probe for the measurement of chlorpyrifos (CP). A mesoporous molecular imprinted polymer (mMIP) layer was generated on the surface of nano-sized MOF-76 using CP, as template. The resulting mMIP-capped MOF-76 (mMIP@MOF-76) contained specific sites for adsorption of CP molecules, guaranteeing the selectivity of the designed probe. The high porosity of rod-shape MOF-76, as well as the mesoporous structure of the MIP layer improved the diffusion process and caused the high sensitivity of the probe. The detection process is based on the remarkable quenching effect of CP on the fluorescence emission of mMIP@MOF-76. Plotting the CP concentration against the fluorescence intensity (λex = 285 nm and λem = 544 nm) gave a linear curve in the concentration range 10-1000 ng mL-1 CP, with 3.41 ng mL-1 limit of detection. The designed probe was utilized for CP determination in fruit juice and environmental samples. The combination of the stable MOF-based support, as well as its remarkable fluorescence features and specific MIP sites, led to a highly selective and ultrasensitive detection system.Graphical abstract.

A molecularly imprinted fluorescence nanosensor based on upconversion metal-organic frameworks for alpha-cypermethrin specific recognition.

A sensitive molecularly imprinted fluorescent nanosensor based on zeolitic imidazolate frameworks-8 (ZIF-8) and upconversion nanoparticles (UCNPs) was developed for the determination of trace alpha-cypermethrin (α-CPM) for the first time. The sensor was synthesized by a layer-by-layer self-assembly strategy. UCNPs with a maximum emission wavelength of 544.5 nm under 980 nm excitation were firstly prepared as the luminous core. Then, ZIF-8 with the large specific surface and porosity was introduced, which not only improved the mass transfer and adsorption capacity of the sensor but also increased the fluorescence intensity of UCNPs as a protective layer. Finally, molecularly imprinted polymers (UCNPs@ZIF-8@MIPs) were fabricated in mixed solutions containing UCNPs@ZIF-8 (support material), α-CPM (template), acrylamide (functional monomer), and divinylbenzene (cross-linker). Under the optimal condition, the fluorescence intensity of UCNPs@ZIF-8@MIP was linearly quenched with increasing concentration of α-CPM in the range 0.10-12 mg L-1 with a detection limit of 0.03 mg L-1 (S/N = 3). The developed UCNPs@ZIF-8@MIP probe was used to detect α-CPM in real samples; the satisfactory results obtained were consistent with those obtained by GC-MS.Graphical abstract.

A turn-on fluorescent nanoprobe based on N-doped silicon quantum dots for rapid determination of glyphosate.

N-Doped silicon quantum dots (N-SiQD) were synthesized using N-[3-(trimethoxysily)propyl]-ethylenediamine and citric acid as silicon source and reduction agent, respectively. The N-SiQD shows a strong blue fluorescence with a high quantum yield of about 53%. It is found that a selective static quenching process occurs between N-SiQDs and Cu2+. Glyphosate can inhibit this phenomenon and trigger the rapid fluorescence enhancement of the quenched N-SiQDs/Cu2+ system due to the specific interaction between Cu2+ and glyphosate. With such a design, a turn-on fluorescent nanoprobe based on N-SiQD/Cu2+ system was established for rapid determination of glyphosate. The determination signal of N-SiQD/Cu2+ was measured at the optimum emission wavelength of 460 nm after excitation at 360 nm. Under optimal conditions, the turn-on nanoprobe showed a linear relationship between fluorescent response and glyphosate concentrations in the range 0.1 to 1 µg mL-1. The limit of determination was calculated to 7.8 ng mL-1 (3σ/S). Satisfactory recoveries were obtained in the determination of spiked water samples, indicating the potential use for environmental monitoring. Graphical abstract Schematic representation of N-SiQD/Cu2+ system for glyphosate determination. Fluorescence quenching of N-SiQDs induced by copper ions and the succedent fluorescent "turn on" triggered by glyphosate.

Surface Molecularly Imprinted Carbon Dots Based Core-Shell Material for Selective Fluorescence Sensing of Ketoprofen.

In this work, we report an environment friendly core-shell material based on Carbon Dot core and Molecularly Imprinted Polymer shell as sensor for highly selective fluorescence detection of ketoprofen. The Carbon Dots (CDs) were prepared by a hydrothermal method and the polymer layer around the CDs core was synthesised by sol-gel polymerisation. The prepared material was characterized by Fluorescence Spectroscopy, FT-IR Spectroscopy and Transmission Electron Spectroscopy (TEM). Fluorescence from the Carbon Dots- Molecularly Imprinted Polymer (CDs-MIP) was found to quench selectively in the presence of ketoprofen and quenching effect was found to be greater than for Non-Imprinted Polymer (CDs-NIP) which indicated the potential of CDs-MIP as a fluorescence sensing material for ketoprofen. The imprinting factor was obtained to be 2.35. Under optimized conditions, a linear response was obtained in the concentration range from 0.039 to 3.9 µM with a detection limit of 0.01 µM. The correlation coefficient was 0.999. The developed sensor was applied to determination of ketoprofen in human serum and urine samples with good recoveries ranging from 96 to 104% indicating successful application of the proposed sensor in biological fluids.

Fluorescent folic acid-capped copper nanoclusters for the determination of rifampicin based on inner filter effect.

Development of excellent sensors to determine trace concentrations of rifampicin is of intense importance for medicine analysis and human health. Herein, a facile and green fluorescent probe was established for the determination of rifampicin by using folic acid protected copper nanoclusters (FA-Cu NCs). Many characterization methods were applied for the analysis of the as-prepared FA-Cu NCs including UV-visible absorption spectra, fluorescence spectra, Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), fluorescence lifetime and X-ray photoelectron spectroscopy (XPS). The TEM image suggested that the as-prepared FA-Cu NCs were highly dispersed. The as-synthesized FA-Cu NCs emerged blue fluorescence under UV light and demonstrated maximum emission wavelength at 446 nm under the maximum excitation wavelength of 358 nm. After the addition of rifampicin, the FL intensities of FA-Cu NCs were uncommonly quenched. The related experimental data intimated that the quenching mechanisms were assumed to the inner filter effect (IFE) and static quenching. The as-proposed probe platform displayed an obvious linear relationship with rifampicin concentrations varying from 0.5 to 100 µM, and the corresponding detection limit (LOD) was 0.073 µM (S/N = 3). Finally, the as-established detection platform was successfully employed to analyze trace concentrations of rifampicin in real samples.

Programmable DNA Circuit-Facilitated Determination of Circulating Extracellular Vesicle PD-L1 for Lung Cancer Diagnosis and Immunotherapy Response Prediction.

Circulating extracellular vesicle (EV) PD-L1 is correlated with the occurrence and progression of lung cancer and has great potential as a valuable diagnostic and immunotherapy predictive biomarker. In this work, we propose a fluorescent biosensing method for the sensitive and accurate determination of circulating EV PD-L1. Specifically, after the phosphatidylserine-targeting peptide-assisted magnetic enrichment, a programmable DNA circuit is designed to translate the presence of PD-L1 to the appearance of numerous duplex DNA probes on the circulating EV surface. Upon fructose treatment, these newly formed duplex DNA probes are released from the EV surface to activate the trans-cleavage activity of CRISPR/Cas12a system, which finally produces a significant fluorescence signal. Experimental results reveal that the method not only enables sensitive determination of EV PD-L1 with a detection limit of 67 particles/mL but also demonstrates the potential use in the diagnosis and immunotherapy response prediction of lung cancer in a principle-of-proof study. Therefore, the method may provide a useful tool for EV PD-L1 determination, which may provide valuable information for the precise diagnosis and personalized treatment of lung cancer patients.

A novel fluorescence sensor based on a tripodal carboxylic acid for detection and measurement of Cu2+ in tomato: Experimental and computational studies.

A tripod organic compound, (4,4',4''-[1,3,5-Triazine-2,4,6-triyltris(oxy)] tribenzoic acid, TCPT), with donor triazine core and multiple fluorophore carboxylic motives, was prepared as an efficient ligand with high emission properties. The TCPT fluorescence emission properties as a chemical sensor were studied (λex = 370 nm) upon the addition of an appropriately diverse set of metal cations. The obtained results revealed the highly selective and efficient role of Cu2+ in quenching of TCPT, even with relevant interfering metal ions. The emission of TCPT was independent of the pH. The interaction of the sensor with Cu2+ and followed by absorption spectra and linear trend of the Stern-Volmer diagram, suggested a static quenching process. The density functional theory calculations were carried out to explore the identity of the electronic transition levels, HOMO-LUMO, and bandgap energies of TCPT. The linear range 1.00 × 10-7-1.00 × 10-6 M was obtained by fluorescence titration of a TCPT solution with Cu2+ ions at optimum conditions. The detection limit was calculated as 5.45 × 10-8 M from the established calibration of titration data. The effect of various ions was studied, and there was no significant interference from the studied metal ions. For the real sample analysis, trace levels of Cu2+ ions were successfully determined in the tomato.

Ultrasound-assisted synthesis of europium doped BPO4 nanoparticles; a new approach for Zn2+ (aq) detection.

In this work, europium ion was doped into boron phosphate nanoparticles (BPO4) using an ultrasonic method followed by the calcination process. The nanoparticles were characterized by various techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy, transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, and scanning electron microscopy (SEM). Doping of europium ion into the BPO4 host crystal was proved by cell volume calculation from XRD patterns, the shift in Raman spectra, and photoluminescence properties. In addition, the europium doped boron phosphate (BPE) as a fluorescence sensor for the quantification of Zn2+ cation was studied. The obtained results showed the enhancement and shift of the photoluminescence peak from 292 to 340 nm. The sensor's selectivity toward this ion was verified in the presence of a variety of common interfering cations. Surprisingly, BPE revealed excellent selectivity and sensitivity towards Zn2+ in the presence of Pb2+, Na+, Fe2+, Al3+, Ca2+, Mg2+, Cu2+, Co2+, Ni2+, Mn2+, Cd2+, Hg2+, Ba2+ and Fe3+ cations. The fluorescence response was linearly proportional to the Zn2+concentration. After the addition of trace amounts of Zn2+ ions into the aqueous solution, a significant enhancement of fluorescence emission occurred with the detection limit of 0.3 µM.

Fluorescence determination of trace level of cadmium with pyrene modified nanocrystalline cellulose in food and soil samples.

Cadmium is one of the most toxic metal that accumulates in the human body via food chain, industrial/agricultural activites. It also has negative effects in organs such as the brain, liver and central nervous system. Therefore, International Agency for Research on Cancer is classified cadmium as "carcinogenic to humans" (group 1). In this work, novel pyrene modified nanocrystalline cellulose (NP-1) was designed as a fluorescence sensor for selective determination of Cd2+ in food and soil samples. FTIR, UV-Vis, SEM, TEM and TGA were used for structural, morphological characterizations and thermal properties of NP-1. The experimental conditions such as selectivity, pH, sensor concentration, photostability, time and interaction mechanism were examined and optimized. The LOD was determined as 0.09 µM (10.70 µg/L) which was lower than WHO's permissible limit of cadmium in plant with 0.10-60.00 µM linear working range. Validation of the present method was performed by spike/recovery test and ICP-MS, then fluorescence determination of Cd2+ in food and soil samples was succesfully applied. The results indicated that the proposed method based on "turn-on" fluorescence of NP-1 was a simple, sensitive and reliable for rapid determination of Cd2+ in real samples with high applicability and stability.

Chiral recognition of naproxen enantiomers based on fluorescence quenching of bovine serum albumin-stabilized gold nanoclusters.

A simple, fast and green method for chiral recognition of S- and R-naproxen has been introduced. The method was based on quenching of the fluorescence intensity of bovine serum albumin-stabilized gold nanoclusters in the presence of naproxen enantiomers. The quenching intensity in the presence of S-naproxen was higher than R-naproxen when phosphate buffer solution at pH7.0 was used. The chiral recognition occurred due to steric effect between bovine serum albumin conformation and naproxen enantiomers. Two linear determination range were established as 7.4×10-7-9.1×10-6 and 9.1×10-6-3.1×10-5molL-1 for both enantiomers and detection limits of 7.4×10-8molL-1 and 9.5×10-8molL-1 were obtained for S- and R-naproxen, respectively. The developed method showed good repeatability and reproducibility for the analysis of a synthetic sample. To make the procedure applicable to biological samples, the removal of heavy metals from the sample is suggested before any analytical attempt.

Isolation and analysis of amyloid-ß 1-42 monomer and oligomers in liquid droplets using an immunoaffinity membrane.

Monomeric molecules such as amyloid-ß can aggregate and transform into oligomeric and fibrous forms, which are implicated in the development and progression of Alzheimer's disease. Novel analytical techniques for the formation of oligomers are required to examine the neurotoxic amyloid-ß oligomers involving fibrils. After isolating amyloid-ß monomer 1-42 using a biotinylated antibody bound to membrane-immobilized avidin (immunoaffinity membrane), their masses were determined by MALDI-TOF MS. Fluorometric determination of more than 0.5µM of aggregated amyloid-ß in pipette droplets was performed after aggregation and dilution of 1mM amyloid-ß. Thus, large (>105nm) amyloid-ß oligomers in microliter volumes of fluids were isolated using the immunoaffinity membrane and quantitatively analyzed after removal of amyloid-ß monomers and small oligomers by non-denaturing electrophoresis. In addition, amyloid-ß oligomers were specifically isolated from a mixture of human plasma and aggregated amyloid-ß and then fluorometrically analyzed. Our results show that the combination of immunoaffinity membrane-binding and fluorescence determinations together with one drop analysis could be used to isolate and detect huge neurotoxic amyloid-ß oligomers such as fibrils in plasma samples.