Sample Recovery Research Articles

A smartphone-assisted fluorescent sensing platform for ochratoxin A using Mn-doped CsPbBr3 perovskite quantum dots embedded in the mesoporous silica as a ratiometric probe

Food sources are susceptible to contamination with ochratoxin A (OTA), which is a serious threat to human health. Thus, the construction of novel, simple sensing platforms for OTA monitoring is of utmost need. Manganese-doped lead halide perovskite quantum dots encapsulated with mesoporous SiO2 (Mn-CsPbBr3 QDs@SiO2) were prepared here and used as a ratiometric fluorescent probe for OTA. Mn-CsPbBr3 QDs, synthesized at room temperature, exhibit dual emission with maximum wavelengths of 440 and 570 nm and, when embedded in the SiO2 layer, produce a stable and robust photoluminescence signal. By adding OTA to the probe, emission at 440 nm increases while emission at 570 nm decreases, so a ratiometric response is obtained. Experimental variables affecting the probe signal were studied and optimized and the mechanism of sensing was discussed. This ratiometric sensor demonstrated excellent selectivity and low detection limit (4.1 ng/ml) as well as a wide linear range from 5.0 to 250 ng/ml for OTA. A simple portable smartphone-based device was also constructed and applied for the fluorescence assay. With different OTA concentrations, the multicolor transition from pink to blue under a UV lamp led to simple visual and smartphone-assisted sensing of OTA by using a color analyzing application. Satisfactory recoveries in black tea, coffee, moldy fig and flour samples confirmed the reliability of the assay. The accuracy of the probe was proved by comparison of the results with high-performance liquid chromatography (HPLC).

A good life with psychosis: rate of positive outcomes in first-episode psychosis at 10-year follow-up.

More knowledge about positive outcomes for people with first-episode psychosis (FEP) is needed. An FEP 10-year follow-up study investigated the rate of personal recovery, emotional wellbeing, and clinical recovery in the total sample and between psychotic bipolar spectrum disorders (BD) and schizophrenia spectrum disorders (SZ); and how these positive outcomes overlap. FEP participants (n = 128) were re-assessed with structured clinical interviews at 10-year follow-up. Personal recovery was self-rated with the Questionnaire about the Process of Recovery-15-item scale (total score ⩾45). Emotional wellbeing was self-rated with the Life Satisfaction Scale (score ⩾5) and the Temporal Experience of Pleasure Scale (total score ⩾72). Clinical recovery was clinician-rated symptom-remission and adequate functioning (duration minimum 1 year). In FEP, rates of personal recovery (50.8%), life satisfaction (60.9%), and pleasure (57.5%) were higher than clinical recovery (33.6%). Despite lower rates of clinical recovery in SZ compared to BD, they had equal rates of personal recovery and emotional wellbeing. Personal recovery overlapped more with emotional wellbeing than with clinical recovery (χ2). Each participant was assigned to one of eight possible outcome groups depending on the combination of positive outcomes fulfilled. The eight groups collapsed into three equal-sized main outcome groups: 33.6% clinical recovery with personal recovery and/or emotional wellbeing; 34.4% personal recovery and/or emotional wellbeing only; and 32.0% none. In FEP, 68% had minimum one positive outcome after 10 years, suggesting a good life with psychosis. This knowledge must be shared to instill hope and underlines that subjective and objective positive outcomes must be assessed and targeted in treatment.

Fe-Co-Based Metal-Organic Frameworks as Peroxidase Mimics for Sensitive Colorimetric Detection and Efficient Degradation of Aflatoxin B1.

Building multifunctional platforms for integrating the detection and control of hazards has great significance in food safety and environment protection. Herein, bimetallic Fe-Co-based metal-organic frameworks (Fe-Co-MOFs) peroxidase mimics are prepared and applied to develop a bifunctional platform for the synergetic sensitive detection and controllable degradation of aflatoxin B1 (AFB1). On the one hand, Fe-Co-MOFs with excellent peroxidase-like activity are combined with target-induced catalyzed hairpin assembly (CHA) to construct a colorimetric aptasensor for the detection of AFB1. Specifically, the binding of aptamer with AFB1 releases the prelocked Trigger to initiate the CHA cycle between hairpin H2-modified Fe-Co-MOFs and hairpin H1-tethered magnetic nanoparticles to form complexes. After magnetic separation, the colorimetric signal of the supernatant in the presence of TMB and H2O2 is inversely proportional to the target contents. Under optimal conditions, this biosensor enables the analysis of AFB1 with a limit of detection of 6.44 pg/mL, and high selectivity and satisfactory recovery in real samples are obtained. On the other hand, Fe-Co-MOFs with remarkable Fenton-like catalytic degradation performance for organic contaminants are further used for the detoxification of AFB1 after colorimetric detection. The AFB1 is almost completely removed within 120 min. Overall, the introduction of CHA improves the sensing sensitivity; efficient postcolorimetric-detection degradation of AFB1 reduces the secondary contamination and risk to the experimental environment and operators. This strategy is expected to provide ideas for designing other multifunctional platforms to integrate the detection and degradation of various hazards.

Mechanism of dentin hardness measurements using a dentin hardness measuring device with a light-emitting diode.

Managing caries is imperative in a rapidly aging society. Current diagnoses use qualitative indices. However, a quantitative evaluation of hardness in a clinical setting may lead to more accurate diagnoses. Previously, hardness meter using indenter with light for tooth monitoring (HAMILTOM) was developed to quantitatively measure tooth hardness. Herein, the physical interpretation of dentin hardness measured using HAMILTOM and the dentin hardness measurement mechanism are discussed. This study evaluates the mechanism of dentin hardness measurements using HAMILTOM physically and compare the invasiveness to dentin by HAMILTOM with those using a dental probe for palpation. Eleven bovine dentin samples were used to create caries models. HAMILTOM measured the dark areas, and its indentations were observed using scanning electron microscopy. Also, its invasiveness was evaluated by comparing the results with those from dental probe palpation. The indentation areas were smaller than the dark areas in HAMILTOM, which may be due to exuded water from the dentin sample and the elastic recovery of dentin sample. Additionally, the dental probe indentation was deeper than the HAMILTOM indentations. The results demonstrate that the indentation areas were smaller than the dark areas measured by HAMILTOM, which might contain the influence of exuded water and the deformation of dentin sample. Also, HAMILTOM is less invasive than dental probe palpation. In the future, HAMILTOM may become a standard hardness measuring method to diagnose root caries.

Ultrasensitive Ochratoxin A Detection in Cereal Products Using a Fluorescent Aptasensor Based on RecJf Exonuclease-Assisted Target Recycling.

Ochratoxin A (OTA) is a mycotoxin widely found in foodstuffs such as cereal grains. It greatly threatens human health owing to its strong toxicity and high stability. Aptasensors have emerged as promising tools for the analysis of small molecule contaminants. Nucleic-acid-based signal amplification enables detectable signals to be obtained from aptasensors. However, this strategy often requires the use of complex primers or multiple enzymes, entailing problems such as complex system instability. Herein, we propose a fluorescent aptasensor for the ultrasensitive detection of OTA in cereal products, with signal amplification through RecJf exonuclease-assisted target recycling. The aptamer/fluorescein-labeled complementary DNA (cDNA-FAM) duplex was effectively used as the target-recognition unit as well as the potential substrate for RecJf exonuclease cleavage. When the target invaded the aptamer-cDNA-FAM duplex to release cDNA-FAM, RecJf exonuclease could cleave the aptamer bonded with the target and release the target. Thus, the target-triggered cleavage cycling would continuously generate cDNA-FAM as a signaling group, specifically amplifying the response signal. The proposed exonuclease-assisted fluorescent aptasensor exhibited a good linear relationship with OTA concentration in the range from 1 pg/mL to 10 ng/mL with an ultralow limit of detection (6.2 ng/kg of cereal). The analytical method showed that recoveries of the cereal samples ranged from 83.7 to 109.3% with a repeatability relative standard deviation below 8%. Importantly, the proposed strategy is expected to become a common detection model because it can be adapted for other targets by replacing the aptamer. Thus, this model can guide the development of facile approaches for point-of-care testing applications.

Development and Fabrication of a Molecularly Imprinted Polymer-Based Electroanalytical Sensor for the Determination of Acyclovir.

Acyclovir (ACV), a synthetic nucleoside derivative of purine, is one of the most potent antiviral medications recommended in the specific management of varicella-zoster and herpes simplex viruses. The molecularly imprinted polymer (MIP) was utilized to create an effective and specific electrochemical sensor using a straightforward photopolymerization process to determine ACV. The polymeric thin coating was developed using the template molecule ACV, a functional monomer acrylamide, a basic monomer 2-hydroxyethyl methacrylate, a cross-linker ethylene glycol dimethacrylate, and a photoinitiator 2-hydroxy-2-methyl propiophenone on the exterior of the glassy carbon electrode (GCE). Scanning electron microscopy, attenuated total reflectance-Fourier transform infrared spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry were employed for the purpose of characterizing the constructed sensor (AM-ACV@MIP/GCE). Differential pulse voltammetry and a 5 mM ferrocyanide/ferricyanide ([Fe(CN)6]3-/4-) redox reagent were used to detect the ACV binding to the specific cavities on MIP. The study involves density functional theory (DFT) calculations, which were conducted to investigate template-functional monomer interactions thoroughly, calculate template-functional monomer interaction energies, and determine the optimal template/functional monomer ratio. DFT calculations were performed using Becke's three-parameter hybrid functional with the Lee-Yang-Parr correlation functional (B3LYP) method and 6-31G(d,p) basis set. The sensor exhibits linear performance throughout the concentration region 1 × 10-11 to 1 × 10-10 M, and the limit of detection and limit of quantification were 7.15 × 10-13 M and 2.38 × 10-12 M, respectively. For the electrochemical study of ACV, the sensor demonstrated high accuracy, precision, robustness, and a short detection time. Furthermore, the developed electrochemical sensor exhibited exceptional recovery in tablet dosage form and commercial human blood samples, with recoveries of 99.40 and 100.44%, respectively. The findings showed that the AM-ACV@MIP/GCE sensor would effectively be used to directly assess pharmaceuticals from actual specimens and would particularly detect ACV compared to structurally similar pharmaceutical compounds.

A comprehensive strategy for quality evaluation of Changan powder by fingerprinting combined with rapid qualitative and quantitative multi-ingredients profiling.

Changan powder (CAP) is mainly used to treat various intestinal diseases. Few studies on CAP have been reported; therefore, it is necessary to clarify the material basis of CAP to lay the foundation for further elucidating its functional mechanism and support the rational use of drugs. In the present study, we aimed to propose a methodology for the quality control of CAP based on qualitative and quantitative analysis of its components. An ultra-performance liquid chromatography coupled with Fourier transform ion cyclotron resonance mass spectrometry (UPLC-FT-ICR-MS) method was developed to identify chemical components in CAP. In addition, fingerprints of 10 different batches of CAP were established, and quantitative analysis based on UPLC was performed to analyze the quality of CAP. A total of 58 compounds were preliminarily characterized. The similarity of 10 batches of CAP was greater than 0.995, and 23 common peaks were calibrated. Investigation of the quantitative analytical methodology showed that the four components had good linear relationships within their respective concentration ranges (r2 ≥ 0.9992), and the relative standard deviation (RSD) of precision and stability was less than 2%. The RSD of sample recovery ranged from 0.78% to 1.52%. The established method can quickly and effectively identify the chemical components of CAP and accurately quantify the known components in CAP. The established fingerprinting and content determination method is stable, reliable, and easy to operate and can be applied in quality control and in vivo research on CAP.

Determination of Nitrofuran in Aquaculture Water by Polycrystal Violet Sensor

The aim of this study is to develop an electrochemical sensor that can detect nitrofuran antibiotic residues in aquaculture water with high sensitivity and selectivity. The polycrystal violet modified glassy carbon electrode (PCV/GCE) was prepared by electropolymerizing crystal violet monomer onto the surface of a glassy carbon electrode (GCE). The optimal preparation and analytical conditions for the sensor were investigated using furazolidone (FZD) as a research model for nitrofurans. The morphology and electrochemical behavior of the sensor were characterized by using scanning electron microscopy, cyclic voltammetry(CV), and electrochemical impedance spectroscopy (EIS). The results showed that the PCV/GCE sensor exhibited a good response to nitrofuran antibiotics. The linear ranges for FZD were 0.25 ∼ 28.0 μM and 28.0 ∼ 60 μM, respectively with detection limits of 0.18 μM. For nitrofurantoin and nitrofurazon, the linear ranges were 6.0 ∼ 40 μM and 3.5 ∼ 20 μM, respectively with detection limits of 0.20 μM and 0.14 μM. The spiked recoveries in real water samples tested ranged from 84% to 106.3%. This method has potential applications for the sensitive detection of nitrofuran antibiotics in aquaculture water due to its low analytical cost and simple sensor preparation.

Method—An Investigation Into Post-Hoc Analysis Methods for Electrochemical Biosensor Data

Recently, researchers are exploring machine learning (ML) algorithms as post-hoc analysis tools to improve performances of electrochemical biosensors (EBs). While reported results are promising, yet comprehensive study on optimal methods for model development is still lacking. For improved efficiency, accuracy, and robustness, it is essential to optimise the relationships between feature extraction techniques and choice of training algorithms. Herein, this paper presents a comparative study between different feature extractions methods, namely principal component analysis (PCA), linear discriminative analysis (LDA), fast Fourier transform (FFT) and discrete wavelet transform (DWT), to compress and extract significant components from differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) datasets. Support Vector Regression (SVR) and Multilayer Perceptron (MLP) models were developed, and their performances were compared with conventional post-analysis methods. The best performing combination for DPV dataset was MLP with DWT, achieving an R2 of 0.995, and for EIS dataset was MLP with PCA, achieving an R2 of 0.960, on test set, respectively. The developed models had achieved an average of 0.61% improvement for real sample recovery tests. The presented approaches demonstrated the capabilities of optimised ML models to automate post hoc analysis for more robust outcomes, while eliminating tedium of post-analysis for end users.

Automated Nanodroplet Dispensing for Large-Scale Spheroid Generation via Hanging Drop and Parallelized Lossless Spheroid Harvesting.

Creating model systems that replicate in vivo tissues is crucial for understanding complex biological pathways like drug response and disease progression. Three-dimensional (3D) in vitro models, especially multicellular spheroids (MCSs), offer valuable insights into physiological processes. However, generating MCSs at scale with consistent properties and efficiently recovering them pose challenges. We introduce a workflow that automates large-scale spheroid production and enables parallel harvesting into individual wells of a microtiter plate. Our method, based on the hanging-drop technique, utilizes a non-contact dispenser for dispensing nanoliter droplets of a uniformly mixed-cell suspension. The setup allows for extended processing times of up to 45 min without compromising spheroid quality. As a proof of concept, we achieved a 99.3% spheroid generation efficiency and maintained highly consistent spheroid sizes, with a coefficient of variance below 8% for MCF7 spheroids. Our centrifugation-based drop transfer for spheroid harvesting achieved a sample recovery of 100%. We successfully transferred HT29 spheroids from hanging drops to individual wells preloaded with collagen matrices, where they continued to proliferate. This high-throughput workflow opens new possibilities for prolonged spheroid cultivation, advanced downstream assays, and increased hands-off time in complex 3D cell culture protocols.

Heparin enables the reliable detection of endotoxin in human serum samples using the Limulus amebocyte lysate assay

The determination of lipopolysaccharide (endotoxin) in serum or plasma samples using Limulus amebocyte lysate (LAL)-based assays is currently not sufficiently reliable in clinical diagnostics due to numerous interfering factors that strongly reduce the recovery of LPS in clinical samples. The specific plasma components responsible for the endotoxin neutralizing capacity of human blood remain to be identified. There are indications that certain endotoxin-neutralizing proteins or peptides, which are part of the host defense peptides/proteins of the innate immune system may be responsible for this effect. Based on our finding that several antimicrobial peptides can be neutralized by the polyanion heparin, we developed a heparin-containing diluent for serum and plasma samples, which enables reliable quantification of LPS measurement in clinical samples using the LAL assay. In a preclinical study involving 40 donors, this improved protocol yielded an over eightfold increase in LPS recovery in serum samples, as compared to the standard protocol. This modified protocol of sample pretreatment could make LPS measurement a valuable tool in medical diagnostics.

Engineering Assembly of Plasmonic Virus-Like Gold SERS Nanoprobe Guided by Intelligent Dual-Machine Nanodevice for High-Performance Analysis of Tetracycline.

Accurate detection of trace tetracyclines (TCs) in complex matrices is of great significance for food and environmental safety monitoring. However, traditional recognition and amplification tools exhibit poor specificity and sensitivity. Herein, a novel dual-machine linkage nanodevice (DMLD) is proposed for the first time to achieve high-performance analysis of TC, with a padlock aptamer component as the initiation command center, nucleic acid-encoded multispike virus-like Au nanoparticles (nMVANs) as the signal indicator, and cascade walkers circuit as the processor. The existence of spike vertices and interspike nanogaps in MVANs enables intense electromagnetic near-field focusing, allowing distinct surface-enhanced Raman scattering (SERS) activity. Moreover, through the sequential activation between multistage walker catalytic circuits, the DLMD system converts the limited TC recognition into massive engineering assemblies of SERS probes guided by DNA amplicons, resulting in synergistic enhancement of bulk plasmonic hotspot entities. The continuously guaranteed target recognition and progressively promoted signal enhancement ensure highly specific amplification analysis of TC, with a detection limit as low as 7.94 × 10-16g mL-1. Furthermore, the reliable recoveries in real samples confirm the practicability of the proposed sensing platform, highlighting the enormous potential of intelligent nanomachines for analyzing the trace hazards in the environment and food.

A liquid chromatographic-mass spectrometric procedure for analysis of pentaerythrityl tetranitrate metabolites – Development, validation and application to ovine serum and human plasma samples

Pentaerythrityl tetranitrate (PETN) is an established drug in the treatment of coronary heart disease and heart failure. It is assumed, that the vasodilative and vasoprotective effects of PETN also have a positive impact on pregnant patients with impaired placental perfusion and studies evaluating the effect of PETN in risk pregnancies have been carried out. In the context of these clinical trials, measuring of serum levels of PETN and its metabolites pentaerythrityl trinitrate (PETriN), pentaerythrityl dinitrate (PEDN), pentaerythrityl mononitrate (PEMN) and pentaerythritol (PE) were required. To evaluate the transfer of PETN and its metabolites (PEXN) from the mother to the fetus using samples from a human clinical trial and animal study, the present work aimed to develop a rapid and simple method to simultaneously analyze PEXN in human and ovine samples.A method employing a rapid and simple liquid–liquid extraction followed by reversed-phase (C18) liquid chromatography coupled to high-resolution mass spectrometry with negative electrospray ionization was developed and validated for the detection of PETN and PEXN in human and ovine samples. PE could only be qualitatively detected at higher concenrations. Method validation requirements, including accuracy, repeatability and intermediate precision were fulfilled in ovine and human samples for all other PEXN with exception PETriN in human samples. The recovery (RE) in ovine samples was 76.7 % ± 12 % for PEMN, 98 % ± 23 % for PEDN, 94 % ± 22 % for PETriN, in human samples RE was 59 % ± 16 % for PEMN, 67 % ± 19 % for PEDN, 71 % ± 17 %. The matrix effects (ME) in ovine samples were 90 % ± 11 % for PEMN, 70 % ± 30 % for PEDN, 107 % ± 17 % for PETriN, in human samples the ME were 93 % ± 13 % for PEMN, 84 % ± 17 % for PEDN, 98 % ± 16 % for PETriN. The limits of quantification (LOQ) in ovine samples were 1.0 ng/mL for PETriN and 0.1 ng/mL for PEMN and PEDN. The LOQs in human samples were 5.0 ng/mL for PETriN and 0.3 ng/mL for PEMN und PEDN. The newly developed method was used to analyze 184 ovine serum samples and 18 human plasma samples.In ovine maternal samples, the highest observed PEDN concentration was 3.5 ng/mL and the highest PEMN concentration was 10 ng/mL, the respective concentrations in fetal serum samples were 4.9 ng/mL for PEDN and 5.4 ng/mL for PEMN. PETriN was only detected in traces in maternal and fetal samples, whereas PETN could not be detected at all. In human maternal samples, the highest concentration for PEDN was 27 ng/mL and for PEMN 150 ng/mL. In umbilical cord plasma, concentrations of 2.3 ng/mL for PEDN and 73 ng/mL for PEMN were detected. Although the PEMN and PEDN concentrations in the human samples were several times higher than in ovine samples, neither PETN nor PETriN signals could be detected. These results demonstrated that the metabolites were transferred from mother to fetus with a slight time delay.

A novel synchronous fluorescence spectrometry combined with fluorescence sensitization for the highly sensitive and simultaneous detection of enoxacin, ofloxacin and tetracycline hydrochloride residues in wastewater

The synergistic effect of sodium dodecyl sulfate (SDS) and Mg2+ could significantly enhance the fluorescence intensity of enoxacin (ENO) at λex/λem = 269.2 nm/385.6 nm, ofloxacin (OFL) at λex/λem = 290.8 nm/466.2 nm and tetracycline hydrochloride (TCH) at λex/λem = 372.6 nm/514.8 nm. Moreover, when the wavelength difference (Δλ) was chosen 135 nm, the synchronous fluorescence spectra of the three antibiotic complexes could be well separated and the interference of the samples matrix were eliminated primely. Therefore, only one synchronous fluorescence scan was needed to simultaneously determine the three antibiotics. Based on these facts, a synchronous fluorescence spectrometry combining fluorescence sensitization for highly sensitive and selective determination of ENO, OFL and TCH residues in wastewater was developed for the first time. The experimental results showed that the concentrations of ENO, OFL and TCH in the range of 0.5–550 ng mL−1, 1–1500 ng mL−1 and 10–5500 ng mL−1 showed a good linear relationship with fluorescence intensity. The limits of detection were 0.0599 ng mL−1, 0.115 ng mL−1 and 0.151 ng mL−1, respectively. The recoveries of the actual sample were 87.50%–99.99 %, 93.00%–98.50 % and 85.70%–98.42 %, respectively. Overall, the novel synchronous fluorescence spectrometry established in the experiment has the advantages of high sensitivity, good selectivity, fast detection speed and high accuracy. It has been successfully applied to the detection of residual amounts of ENO, OFL and TCH in wastewater with satisfactory results.

One step cleanup of 160 pesticides and veterinary drugs in aquatic products using melamine-based automatic pressure filtration purification method combined with HPLC-MS/MS

A 15-channel pressure filtration purification method was presented for high throughput sample preparation of aquatic products. A cost-effective device was constructed and melamine sponge was selected as the cleanup sorbent. Upon interfacing with HPLC-MS/MS, the analytical procedure demonstrated its suitability for quantifying 160 pesticides and veterinary drug residues in aquatic products such as fish, shrimp, and crab. The method achieved sample recoveries ranging from 61.3 to 124.9 %. The detection limits were established between 0.5 and 1.0 μg/kg, while the quantitation limits were confirmed to be within the range of 1.0–2.0 μg/kg. The method was applied to quantify the pesticide and veterinary drug residues in mostly consumed aquatic products from five coastal provinces in China. The results showed significant differences between different aquatic products in the concentrations of pesticide and veterinary drug residues, implying the necessity of supervision for the accurate determination of pesticides and veterinary drugs.

Extreme gradient boosting-enhanced molecularly imprinted fluorescence nanosensor for rapid identification and visual detection of deltamethrin in seawater and aquatic products

Deltamethrin (DEL), a synthetic pyrethroid insecticide, may have long-term adverse effects on the aquatic environment. Extreme Gradient Boosting (XGBoost) is a classic ensemble boosting algorithm framework known for its high training efficiency, strong prediction performance, and versatile applications. In this study, we successfully developed a highly sensitive molecularly imprinted fluorescence nanosensor (MF-sensor) for DEL determination, enhanced by the XGBoost algorithm. The MF-sensor was fabricated by grafting blue and red CdSe/ZnS quantum dots onto a molecularly imprinted silica layer. The MF-sensor consisted of blue-molecularly imprinted polymer (MIP)-quantum dots (QDs) and r-MIP-QDs, which selectively detected DEL, and unmodified green CdSe QDs, which were not selective for DEL. Under optimized conditions, we observed an excellent linear relationship between the I526/(I450 +I630) ratio and DEL concentration ranging from 0.01 mg/L to 40.0 mg/L (R2 = 0.9944). The limit of detection was determined to be 1.34 µg/L. The recoveries in actual samples ranged from 98.5% to 109.0%, with a relative standard deviation (RSD) below 7.5%. Additionally, we utilized the XGBoost algorithm to establish a DEL prediction model, achieving an accuracy of 95.7%. The recoveries ranged from 96.0% to 102.4%, with a RSD below 5.5%. Overall, the proposed MF-sensor, enhanced by the XGBoost algorithm, was successfully utilized for the detection of DEL in environmental and aquatic products.

New application of bimetallic Ag/Pt nanoplates in a colorimetric biosensor for specific detection of E. coli in water.

A fast and sensitive aptasensor was developed using nanoplates with peroxidase activity as a novel approach. E. coli detection is described using a silver/platinum nanoplate (Ag/Pt NPL) that interacts with an oligonucleotide aptamer as a bioreceptor. The size of the Ag/Pt NPLs was about 42 nm according to the FE-SEM images. The EDS result indicates that a thin layer of Pt ions was coated on the surface of the Ag NPLs. This nanobiosensor has the ability to specifically bind to E. coli, increasing the peroxidase activity of the apt-Ag/Pt NPL. Finally, the blue color of the solution in the contaminated water samples was increased in the presence of 3,3',5,5'-tetramethylbenzidine (TMB) as a substrate and H2O2. The assay can be completed in 30 min and the presence of E. coli levels can be distinguished with the naked eye. The absorbance at 652 nm is proportional to pathogen concentration from 10 to 108 CFU·mL-1, with a detection limit of 10 CFU·mL-1. The percent recovery for the water samples spiked with E. coli is 95%. The developed assay should serve as a general platform for detecting other pathogenic bacteria which affect water and food quality. The proposed E. coli detection strategy has appealing characteristics such as high sensitivity, simple operation, short testing time, and low cost.

Spinel Nanoparticles ZnCo2O4 as High Performance Electrocatalyst for Electrochemical Sensing Antibiotic Chloramphenicol

<p>In this study, ZnCo<sub>2</sub>O<sub>4</sub> nanoparticles were synthesized via the coprecipitation method using different annealing temperatures from 200°C to 800°C. By varying the treatment temperature, the morphology changed from amorphous to tetragonal, and finally to polygonal particles. As temperature increased, the sizes of the nanoparticles also changed from 5 nm at 200°C to approximately 500 nm at 800°C. The fabricated material was used to modify the working electrode of a screen-printed carbon electrode (SPE), which was subsequently used to survey the detection performance of the antibiotic, chloramphenicol (CAP). The electrochemical results revealed that the material exhibits a good response to CAP. Further, the sample that annealed at 600°C displayed the best performance, with a linear range of 1–300 μM, and a limit of detection (LOD) of 0.15 μM. The sensor modified with ZnCo<sub>2</sub>O<sub>4</sub> also exhibited the potential for utilitarian application when the recovery in a real sample was above 97%.</p>

Rational Biomimetic Construction of Lignin-based Carbon Nanozyme for Identification of Uric Acid in Human Urine

Nanozymes have made remarkable progress in the field of sensing assays by replacing native enzyme functions. However, it is still a challenge to rationally design active centers from molecular structure to enhance the catalytic performance and develop low-cost nanozymes. In this work, guided by the catalytic site of horseradish peroxidase (HRP), iron source and histidine were coupled to the main chain of aminated sodium lignosulfonate (SL) through the self-assembly biomimetic strategy to construct His-SL-Fe with peroxidase activity. The inherent functional groups and basic framework of aminated SL provide a robust environment and promote the formation of active sites. His-SL-Fe shows excellent robustness over multiple test cycles and has a strong affinity for the substrate compared to HRP. His-SL-Fe had been effectively integrated in the sensing system for catalytic detection of uric acid (UA) to achieve accurate recognition of UA in the range of 0.5–100 μM with the limit of detection as low as 0.18 μM. The recovery of human urine samples is in the range of 96.8%–106.1 % and the error is within 4 %. This work not only provides a new approach for the directed design of high-performance nanozymes, but also demonstrates promising ideas for the refined application of biomass resources.

A novel biosensor based on antibody-controlled strand displacement amplification (SDA) and hybridization chain reaction (HCR) for tetracycline detection

The specificity of antibodies and efficient amplification of nucleic acid molecules play an important role in developing biosensors for monitoring human and environmental health. Herein, integrating their capabilities by site-selective modification of small molecules on DNA, a biosensor based on antibody-controlled strand displacement amplification (SDA) and hybridization chain reaction (HCR) was developed. The SDA–HCR reaction was activated by the competitive binding of antibodies to free small molecules and small molecule-conjugated DNA. As a proof-to-concept, we developed a biosensor capable of detecting tetracycline (TC) with high sensitivity and specificity. First, TC was labeled with azide group through chemical modification, and TC–DNA was prepared by copper-free click chemistry. Further, the antibody-controlled SDA–HCR reaction was developed through serial optimization. By this method, TC could be detected in a linear range of 0.01–100 µM with a detection limit of 0.006 µM, and the recovery of actual samples was 96.62–100.31 % with 1.70–4.00 % RSD, suggesting satisfactory performance by the biosensor. Using this method, TC or any other small molecules can be detected without washing, immobilization, and multiple additional steps, which would simplify detection to a great degree. Consequently, the distinctive strategy proposed in this work may find more applications in the detection of other small molecules.