Selective optosensing of iron(III) ions in HeLa cells using NaYF4:Yb3+/Tm3+ upconversion nanoparticles coated with polyepinephrine.

Novel polyepinephrine-modified NaYF4:Yb,Tm upconversion luminescent nanoparticles (UCNP@PEP) were prepared via the self-polymerization of epinephrine on the surfaces of the UCNPs for selective sensing of Fe3+ inside a cell and for intracellular imaging. The proposed UCNP@PEP probe is a strong blue light emitter (λmax = 474 nm) upon exposure to an excitation wavelength of 980 nm. The probe was used for detecting Fe3+ owing to the complexation reaction between UCNP@PEP and Fe3+, resulting in reduced upconversion luminescence (UCL) intensity. The proposed probe has a detection limit of 0.2 µM and a good linear range of 1-10 µM for sensing Fe3+ ions. Moreover, the UCNP@PEP probe displays high cell viability (90%) and is feasible for intracellular imaging. The ability of the probe to sense Fe3+ in a human serum sample was tested and shows promising output for diagnostic purposes. The prepared UCNP@PEP probe was characterized by using UV-visible (UV-Vis) absorption spectrometry, fluorescence (FL) spectrometry, field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR).

Novel "turn on-off" paper sensor based on nonionic conjugated polythiophene-coated CdTe QDs for efficient visual detection of cholinesterase activity.

An increasing number of patients are living with Alzheimer's disease (AD); thus, the need for a method to detect AD early and sensitively has become urgent, and the demand for an intelligent analytical platform is growing year by year. Abnormal levels of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are known to be indicative of AD. In this work, a novel conjugated polythiophene (CP) compound was successfully combined with CdTe quantum dots (QDs) to improve their selectivity and sensitivity. The QDs successfully enabled the detection of low concentrations of AChE by turning on the fluorescence of the CdTe/CP via the interaction between CP and thiocholine produced by ATCh hydrolysis and aggregation induced emission enhancement (AIEE). Under optimal conditions, we reached a low detection limit of 0.14 U L-1, which is 7.9 times lower than that of pristine QDs. More importantly, an efficient, inexpensive, and disposable paper-based platform, which allows the efficient visual detection of AChE activity via the color variation of CdTe/CP, was designed. Moreover, the accuracy of the method was demonstrated by conducting a recovery test in human serum, in which the recoveries reached 107% and 110%, proving that CdTe/CP has considerable potential to be used for analyzing real biological samples. The advantages of this method are its simplicity, fast detection capability, affordability, and the fact that it can be used for on-site detection of AChE activity. Furthermore, it has certain guiding significance for detecting AD.

Preparing cuprous oxide nanomaterials by electrochemical method for non-enzymatic glucose biosensor.

Cuprous oxide (Cu2O) nanostructure has been synthesized using an electrochemical method with a two-electrode system. Cu foils were used as electrodes and NH2(OH) was utilized as the reducing agent. The effects of pH and applied voltages on the morphology of the product were investigated. The morphology and optical properties of Cu2O particles were characterized using scanning electron microscopy, x-ray diffraction, and diffuse reflectance spectra. The synthesized Cu2O nanostructures that formed in the vicinity of the anode at 2 V and pH = 11 showed high uniform distribution, small size, and good electrochemical sensing. These Cu2O nanoparticles were coated on an Indium tin oxide substrate and applied to detect non-enzyme glucose as excellent biosensors. The non-enzyme glucose biosensors exhibited good performance with high response, good selectivity, wide linear detection range, and a low detection limit at 0.4 µM. Synthesized Cu2O nanostructures are potential materials for a non-enzyme glucose biosensor.

LED-induced in-column molecular imprinting for solid phase extraction/capillary electrophoresis.

A novel light-emitting diode-induced polymerization technology was demonstrated, which could be applied for the on-line construction of an in-column molecularly imprinted solid phase extraction concentrator for capillary electrophoresis. Such a strategy exhibited the advantages of simplicity, zero dead volume, and ease of renewing the concentrator.

Straightforward smartphone assay for quantifying tannic acid in beverages based on colour change of Eu3+/polyethyleneimine complex.

Tannic acid (TA)-a natural product-is a polyphenol derivative that occurs in certain kinds of beverages. A large amount of TA could give rise to an unpleasant flavour and could negatively affect the human body by causing stomach irritation, abdominal pain, nausea, vomiting, and even death. Thus, the need exists for a simple TA detection procedure that meets specific criteria such as on-site analysis, portability, and affordability. Herein, we present a new TA assay, which is based on the fluorescent quenching effect of an efficient fluorophore, and which comprises a smartphone-integrated homemade reader system. The fluorescent polyethyleneimine-derivatised polymer (FP), a strong emitter at 510 nm, was synthesised with the aid of a facile sonication method. In the presence of Eu3+ ions, TA quenches the fluorescence of the FP via electrostatic interaction. A smartphone was used to capture an image of the FP undergoing fluorescence for conversion to RGB values. The blue channel was chosen for further analysis because it offered the highest R2-value compared to the red and green channels. We verified these results using a commercial spectrofluorometer and calculated the limit of detection of this assay as 87 nM and 20 nM for the homemade reader and spectrofluorometer, respectively. The detection range for TA with the proposed assay is 0.16-66.66 µM. The application of the proposed method to real beverage samples for TA detection demonstrates its analytical applicability.

Simple fluorescence optosensing probe for spermine based on ciprofloxacin-Tb3+ complexation.

We developed a facile detection method of spermine based on the fluorescence (FL) quenching of the ciprofloxacin-Tb3+ complex, which shows astrong green emission. Ciprofloxacin (CP) makes efficient bondings to Tb3+ ion as a linker molecule through carboxylic and ketone groups to form a kind of lanthanide coordination polymer. The addition of spermine that competes with Tb3+ ions for the interaction with CP due to its positive charge brings about weakened coordination linkage of CP and Tb3+. The probe exhibited high sensitivity, selectivity, and good linearity in the range of 2-180 µM with a low limit of detection of 0.17 µM. Moreover, we applied this method on the paper strip test (PST), along with the integration of a smartphone and Arduino-based device. The practical reliability of the developed probe was evaluated on human serum samples with acceptable analytical results.

Dual emission nonionic molecular imprinting conjugated polythiophenes-based paper devices and their nanofibers for point-of-care biomarkers detection.

Enzyme-based assays have been extensively used for the early diagnosis of disease-related biomarkers. However, these assays are time-consuming, resource-intensive, and infrastructure-dependent, which renders them unsuitable and impractical for use in resource-constrained areas. Thus, there is a strong demand for a biocompatible and potentially generalizable sensor that can rapidly detect cancer biomarkers at ultralow concentration. Herein, an enzyme-free, cost-efficient, and easy-to-use assay based on a novel approach that entails fluorescent molecularly imprinting conjugated polythiophenes (FMICPs) for cancer biomarkers detection is developed. The promising conjugated polythiophenes structure, with a PLQY as high as 55%, provides a straightforward, and affordable method for free-enzyme signal generation. More importantly, the feasibility of integrating printed-paper technology with a sensitive and cost-effective smartphone and portable prototype testing device that could be utilized for rapid point-of-care (POC) cancer diagnostics is successfully introduced. Significantly, the unique structure of FMICP nanofibers (FMICP NFs) displays superior performance with enhanced sensitivity that is 80 times higher than that of pristine FMICP. This assay could lower the limits of detection to 15 fg mL-1 and 3.5 fg mL-1 for α-fetoprotein (AFP) and carcinoembryonic antigen (CEA), respectively, which are three orders of magnitude exceeding that of the standard enzyme-based assay. Moreover, the developed sensors are successfully applied to the fast diagnosis of AFP in liver cancer patients and the FMICP and FMICP NFs results are in excellent agreement with those of clinical ELISA.

Fabrication of a Selective and Sensitive Sensor Based on Molecularly Imprinted Polymer/Acetylene Black for the Determination of Azithromycin in Pharmaceuticals and Biological Samples.

A new selective and sensitive sensor based on molecularly imprinted polymer/acetylene black (MIP/AB) was developed for the determination of azithromycin (AZM) in pharmaceuticals and biological samples. The MIP of AZM was synthesized by precipitation polymerization. MIP and AB were then respectively introduced as selective and sensitive elements for the preparation of MIP/AB-modified carbon paste (MIP/ABP) electrode. The performance of the obtained sensor was estimated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. Compared with non-molecularly imprinted polymer (NIP) electrodes, NIP/ABP electrodes, and MIP-modified carbon paste electrodes, MIP/ABP electrode exhibited excellent current response toward AZM. The prepared sensor also exhibited good selectivity for AZM in comparison with structurally similar compounds. The effect of electrode composition, extraction parameters, and electrolyte conditions on the current response of the sensor was investigated. Under the optimized conditions, the prepared sensor showed two dynamic linear ranges of 1.0 × 10-7 mol L-1 to 2.0 × 10-6 mol L-1 and 2.0 × 10-6 mol L-1 to 2.0 × 10-5 mol L-1, with a limit of detection of 1.1 × 10-8 mol L-1. These predominant properties ensured that the sensor exhibits excellent reliability for detecting AZM in pharmaceuticals and biological fluids without the assistance of any separation techniques. The results were validated by the high-performance liquid chromatography-tandem mass spectrometry method.

Rapid and selective extraction of multiple macrolide antibiotics in foodstuff samples based on magnetic molecularly imprinted polymers.

Magnetic molecularly imprinted polymers (MMIPs) were prepared based on surface molecular imprinting using erythromycin (ERY) as template molecule and Fe3O4 nanoparticles as support substrate. The MMIPs possessed high adsorption capacity of 94.1 mg/g for ERY and the imprinting factor was 11.9 indicating good imprinted effect for ERY. Selective evaluation demonstrated favorable selectivity of MMIPs for multiple macrolide antibiotics (MACs). Using MMIPs as adsorptive material, a rapid and convenient magnetic solid-phase extraction (MSPE) procedure was established for simultaneous and selective separation of six MACs in pork, fish and shrimp samples, then the MACs was subjected to high-performance liquid chromatography-ultraviolet (HPLC-UV) analysis. At different fortified concentrations, the extraction recoveries could reach 89.1% and the relative standard deviations were lower than 12.4%. Chromatogram revealed the response signals of MACs in spiked samples were greatly enhanced and matrix interferences were effectively eliminated after treatment with MSPE. The proposed MSPE procedure coupled with HPLC-UV realized selective and sensitive determination of multiple MACs in foodstuff samples.

Molecularly imprinted solid phase microextraction fiber for trace analysis of catecholamines in urine and serum samples by capillary electrophoresis.

A selective and flexible monolithic moleculary imprinted polymer (MIP) fiber was developed in batch for solid phase microextraction (SPME) of catecholamines (CAs), i.e., dopamine (DA), epinephrine (E) and norepinephrine (NE), and coupled with capillary electrophoresis (CE) for trace analysis of urine and serum samples. The polymer fiber was synthesized in-situ simply using a flexible capillary as a mold and the polymerization protocols and SPME experimental conditions were examined in detail. The reproducibility of fiber to fiber fabrication (n=5) was in range of 5.9-9.8% for three CAs. The fiber also shows high stability without any deterioration of extraction performance after 30 times use. Under the established optimum conditions, the limits of detection for DA, E, and NE were 7.4, 4.8, and 7.1 nmol L(-1), respectively, with the enhancement factor over 100 after MIP-SPME. The specific selectivity to three CAs was discovered with the developed MIP fibers compared with non-imprinted polymer (NIP) fiber. Finally, the MIP fibers were successfully applied for selective extraction of CAs in urine and serum samples with the relative recoveries ranging from 85% to 103%. The fabricated MIP-fibers were promising in preparation of biological samples in batch followed by CE-UV detection.

Rapid and selective determination of urinary lysozyme based on magnetic molecularly imprinted polymers extraction followed by chemiluminescence detection.

A rapid, low cost and selective chemiluminescence method coupled with magnetic molecularly imprinted polymers extraction was developed to detect lysozyme in human urine samples. Compared with traditional solid-phase extraction, this method could achieve selective extraction for the lysozyme, avoid the time consuming elution from a column or centrifugation steps, and then showed great potential in the high-throughput screening of clinical samples. The parameters affecting the performance of extraction and chemiluminescence were investigated. Under optimal conditions, the whole analytical procedure was completed within 12 min and spiked recovery ranged from 90.1% to 103.7% (R.S.D.≤6.7%). The limit of quantitation was 5 ng mL(-1). Furthermore, the results obtained by the proposed method were linearly correlated to those by commercial lysozyme detection kit (r=0.9595). Finally, the validated method was used to measure the urinary lysozyme of renal disease patients and healthy controls. The results confirmed the reliability and practicality of the protocol and revealed a good perspective of this method for biological sample analysis.