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Increased use of pesticides in agriculture requires new advanced techniques to monitor both environmental levels and human exposure of pesticides to avoid potential adverse health outcomes in sensitive populations. Atrazine is widely used to control broadleaf weeds, and here we developed a new sensor capable of detecting diaminochlorotriazine (DACT), the major metabolite and biomarker of atrazine exposure. We established an Au@PtPd nanoparticles labeled lateral flow immunoassay (LFIA) for immunochromatographic based rapid detection of urinary DACT. The detection was based on competitive immunoassay between the analyte and the BSA-conjugated antigen. As evaluated, the coupled mesoporous core-shell Au@PtPd nanoparticles, with superior peroxidase-like activity, as the signal indicator offers a rapid direct chromatographic readout inversely correlated with the concentration of analytes, providing a detection limit of 0.7 ng/mL for DACT. Moreover, the detection limits were boosted to as low as 11 pg/mL with the detectable range from 10 pg/ml to 10 ng/mL, through a one-step catalytic chromogenic reaction. A rapid readout device was developed by 3D printing to provide a stable real-time quantification of the color intensity capable of assessing both chromatographic and absorbance results. This Au@PtPd nanoparticle-based immunosensing platform, as well as the 3D printed readout device, provide a promising tool for on-site and ultrasensitive detection of pesticide biomarkers., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The widespread use of herbicides in agriculture and gardening causes environmental and safety issues such as water pollution. Thus, efficient and convenient analysis of the levels of herbicide residues is of significant importance. Here, we employed 3D-printing to design a multiplex immunosensor for simultaneous detection of two widely used herbicides, atrazine and acetochlor. Multiplexing was achieved through customization of a lateral flow immunoassay, and then integrated with an electrochemical analyzer for ultrasensitive detection. Quantification of herbicide residues was realized through the detection of a novel nanomaterial label, the mesoporous core-shell palladium@platium nanoparticle (Pd@Pt NP), for its outstanding peroxidase-like property. During the electrochemical analysis, the catalytic activity of Pd@Pt NPs on the redox reaction between thionin acetate and hydrogen peroxide provided an electrochemically driven signal that accurately indicated the level of herbicide residues. Using this Nanomaterial-enhanced multiplex electrochemical immunosensing (NEMEIS) system, simultaneous detection of atrazine and acetochlor was realized with a limit of detection of 0.24 ppb and 3.2 ppb, respectively. To further evaluate the feasibility, the optimized NEMEIS was employed for detection in atrazine and acetochlor residue-containing spiked samples, and an overall recovery with 90.8% - 117% range was obtained. The NEMEIS constructed with the aid of 3D-printing provides a rapid, precise, economical, and portable detection device for herbicides, and its success suggests potential broad applications in chemical analysis, biosensors and point-of-care monitoring., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Programmed cell death protein 1 (PD-1) is one of the coinhibitory checkpoints upon T cell activation, the abnormal expression of which severely threatens host immune modulatation for chronic infection. Thus, fast and sensitive monitoring of PD-1 is of vital importance for early diagnosis and cancer treatment. The current detection methods largely based on enzyme-linked immunosorbent assay (ELISA) require time-consuming incubation and complicated washing steps. Herein, we designed a simple and portable nanofiber paper (NFP)-based fluorescence "off-on" immunosensor for PD-1 rapid determination. Molybdenum disulfide (MoS 2 ) nanosheets modified NFP (MoS 2 -NFP) was employed for adsorbing and immobilizing CdSe/ZnS quantum dots-antibody (QDs-Ab) complex to construct a ready-to-use fluorescent immunosensor. The fluorescent signal of QDs-Ab was initially quenched by MoS 2 under the Förster resonance energy transfer (FRET) effect. When the PD-1 target was specifically captured onto NFP by immunization, the QDs-Ab-PD-1 complex was promptly desorbed from the MoS 2 -NFP surface, resulting in FRET impediment and fluorescence recovery. As an alternative quenching agent, graphene oxide (GO) served as a contrast to investigate NFP-based sensing performance. Owing to superior quenching and desorption efficiency, the MoS 2 -NFP-based fluorescence immunosensor exhibited nearly 2-fold lower detection limit (85.5 pg/mL) than GO-NFP-based sensor (151 pg/mL) for PD-1 monitoring. Excellent selectivity and satisfactory recovery in PD-1 mouse cell culture supernatant samples were confirmed as well. In addition, the comparable detectability of the MoS 2 -NFP-based immunosensor was accurately evaluated by a standard PD-1 mouse ELISA kit. This study displayed a simple, rapid, low-cost, and portable point-of-care PD-1 assay, indicating its broad application prospect toward clinical diagnoses.

The development of some sensitive methods for MUC1 is critical for preclinical diagnosis of tumors. In this experiment, we built a triple-amplified electrochemical aptasensor to achieve sensitive detection of MUC1, which was based on exonuclease III (Exo III)-assisted with strand displacement reaction and enzyme catalytic strategy. Firstly, with the help of Exo III, MUC1 and aptamer could be recycled during the cycle I, the single stranded DNA-1 (S-1) was produced during the process and was introduced to the hybride reaction on the electrode. Secondly, during the cycle II, strand displacement reaction was triggered on the electrode with the adding of hairpin DNA-2 (H-2). Thirdly, after the gold nanoparticles (AuNPs)-DNA-enzyme conjugates hybrided with the H-2 on the electrode, the AuNPs-DNA-enzyme conjugates could act as signal probe to produce electrochemical catalytic signal. We used the fabricated triple-amplified electrochemical aptasensor that could detect MUC1 from 0.1 pg mL -1 to 10 ng mL -1 with the detection limit of 0.04 pg mL -1 under the optimized experimental conditions. The constructed triple-amplified electrochemical aptasensor could be applied in real samples determination. Besides, the strategy can be applied to detect other proteins for health monitoring., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Sensitive and specific detection methods are critical to the detection of glycoproteins. Immunoassay has been a powerful tool for this purpose, in which antibodies or their mimics particularly molecularly imprinted polymers (MIPs) are used for specific recognition. Epitope and glycan are two structure features of a glycoprotein. However, immunoassays based on simultaneous recognition towards the two characteristics have been scarcely explored so far. Herein we present a new strategy called orthogonal dual molecularly imprinted polymer-based plasmonic immunosandwich assay (odMIP-PISA). It relies on double recognition towards a target glycoprotein by two different types of MIPs, using epitope-imprinted gold nanoparticles (AuNPs)-coated slide as capturing substrate to recognize the peptide epitope and glycans-imprinted Raman-active silver nanoparticles as labeling nanotags to recognize the glycans. Carcinoembryonic antigen (CEA), a routinely used marker for colon cancer, was used as a test glycoprotein. The orthogonal double recognition apparently improved the specificity, reducing the maximum cross-reactivity from 14.4% for epitope recognition and 15.2% for glycan recognition to 8.2% for double recognition. Meanwhile, the plasmonic nanostructure-based Raman detection provided ultrahigh sensitivity, yielding a limit of detection of 5.56 × 10 -14  M (S/N = 10). Through measuring the CEA level in human serum, this method permitted differentiation of colon cancer patient from healthy individual. Compared with the traditional immunoassay, odMIP-PISA exhibited multiple advantages, including simplified procedure (6 steps), speed (30 min), reduced cost, and so on. Therefore, this new approach holds great promise in many applications particularly clinical diagnosis., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Molecularly imprinted polymers (MIPs) and aptamers, as effective mimics of antibodies, can overcome only some drawbacks of antibodies. Since they have their own advantages and disadvantages, the combination of MIPs with aptamers could be an ideal solution to produce hybrid alternatives with improved properties and desirable features. Although quite a few attempts have been made in this direction, a facile and controllable approach for the preparation of aptamer-MIP hybrids still remains lacking. Herein, we present a new approach for facile and controllable preparation of aptamer-MIP hybrids for high-specificity and high-affinity recognition toward proteins. An aptamer that can bind the glycoprotein alkaline phosphatase (ALP) with relative weak affinity and specificity was used as a ligand, and controllable oriented surface imprinting was carried out with an in-water self-polymerization system of dopamine. A thin layer of polydopamine was formed to cover the template to an appropriate thickness. After removing the template from the polymer, an aptamer-MIP hybrid with apparently improved affinity and specificity toward ALP was obtained, giving cross-reactivity of 3.2-5.6% and a dissociation constant of 1.5 nM. With this aptamer-MIP hybrid, a plasmonic immunosandwich assay (PISA) was developed. Reliable detection of ALP in human serum by the PISA was demonstrated.

Flexible electrochemical sensors for measurement and quantification of biomarkers are attracting a great deal of attention in non-invasive medical applications, due to their high mechanical compatibility and conformability with the human body. Realization of the full potential of such novel systems relies heavily on their effective manufacturing. Particularly, there is a need for manufacturing techniques that can realize complex designs, consisting of multiple functional materials which are required for sensor functionality. Among emerging additive manufacturing techniques, Direct-Ink-Writing (DIW), where polymer nanocomposite inks are dispensed through nozzles and deposited with high spatial control, carries a great potential to address this need. Here, we introduce a 3D printed flexible electrochemical biosensor for glucose detection. We show that our biosensor works linearly in glucose solution with a concentration range between 100 and 1000 μM. The sensitivity of glucose biosensor is estimated to be 17.5 nA μM -1 , and the calculated value of the detection limit (S/N = 3) is 6.9 μM. The demonstrated electrochemical performance and surface properties of the printed sensors show the promising advantages of using this technique over the conventional screen printing method. These advantages include higher sensitivity and specificity and, reduced material consumption., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Non-invasive living cell microscopy in real time is essential for a wide variety of biomedical research. Here, we present a subcellular refractive index imaging technique for living cells based on a graphene biosensor system. Owing to the optical reflectivity differences of graphene to s- and p-polarizations, a 45° generalized-cylindrical-vector-polarized laser beam is employed to demodulate the reflected cylindrical vector beam for differential detecting. Benefitting from the vector beam-enabled common-path graphene biosensor, the imaging spatial resolution and refractive index sensitivity are noticeably improved. Subcellular refractive index mapping of live human colonic cancer cells is perfectly achieved without inducing any cell damage. Furthermore, real-time monitoring of an individual cell is also performed with the disassembly of the cell nucleolus clearly observed. This technique would be a promising tool for the study of living cell morphology, kinetics, and pathology, and for other biomedical research.

The detection of E. coli O157:H7 in foods has held the attention of many researchers because of the seriousness attributed to this pathogen. In this study, we present a simple, sensitive, rapid and portable smartphone based fluorescence device for E. coli O157:H7 detection. This field-portable fluorescent imager on the smartphone involves a compact laser-diode-based photosource, a long-pass (LP) thin-film interference filter and a high-quality insert lenses. The design of the device provided a low noise to background imaging system. Based on a sandwich ELISA and the specific recognition of antibody to E. coli O157:H7, the sensitive detection of E. coli O157:H7 were realized both in standard samples and real matrix in yoghurt and egg on our device. The detection limit are 1 CFU/mL and 10 CFU/mL correspondingly. Recovery percentages of spiked yogurt and egg samples with 10 3 , 10 4 and 10 5 CFU/mL E. coli O157:H7 were 106.98, 96.52 and 102.65 (in yogurt) and 107.37, 105.64 and 93.84 (in egg) samples using our device, respectively. Most importantly, the entire process could be quickly completed within two hours. This smartphone based device provides a simple, rapid, sensitive detection platform for fluorescent imaging which applied in pathogen detection for food safety monitoring., (Copyright © 2017 Elsevier B.V. All rights reserved.)

MicroRNA 21 (MIR21) has garnered much attention in recent years as an important disease biomarker. The detection of it in human system shows great significance for the healthy evaluation and major diseases early detection. Herein, a novel approach tactfully manipulates the in-situ precise preparation of copper nanoclusters on overlapping Y-shaped ds-DNA for MIR21 analysis were developed in the proposed integrated aptasensor. In the presence of target MIR21, overlapping Y-shaped ds-DNA was constructed on electrode. Copper nanoclusters were in-situ prepared on this effective template for target detection. Taking advantage of exonuclease T7 triggered targets recycling, hybridization chain reaction (HCR) and copper nanoclusters triple amplification strategy, linear detection of MIR21 was achieved from 10pM to 0.1fM with a detection limit down to 10aM (S/N > 3). This approach provides a good model for integrating both synthesis and detection into one electrochemistry component. It showed promising potential for applications in aptamer related target detection in human serum analysis., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The real-time and label free detection abilities of surface plasmon resonance (SPR) biosensors provide a way of evaluating the influence of some genes' expression on anti-tumor drug cytotoxicity. However, studies in this field are lacking. Connexin 43 is a tumor suppressor gene and the mechanism of its effect in cisplatin cytotoxicity is still unclear. A phase SPR biosensor was used to determine the influence of connexin 43 expression on cisplatin cytotoxicity in three cancer cell lines. The results showed that the SPR signal curves have two stages. In the first hour, the SPR signal shows dramatic changes which are related to connexin 43 expression. In the subsequent stage, the SPR signal slowly declines and is related to apoptosis. Comparison of SPR measurements from several conventional biological assays showed that connexin 43 expression can affect cellular response to cisplatin in the period of oxidative stress, and results in the cells being more sensitive to cisplatin. The conclusion is further confirmed by long-term SPR measurement results and cellular morphological changes.

Because human immunodeficiency virus (HIV) has been one of the most terrible viruses in recent decades, early diagnosis of the HIV gene is of great importance for all scientists around the world. In our work, we developed a novel electrochemical biosensor based on one-step ultrasonic synthesized graphene stabilized gold nanocluster (GR/AuNC) modified glassy carbon electrode (GCE) with an exonuclease III (Exo III)-assisted target recycling amplification strategy for the detection of HIV DNA. It is the first time that GR/AuNCs have been used as biosensor platform and aptamer with cytosine-rich base set as capture probe to construct the biosensor. With the combination of cytosine-rich capture probe, good conductivity and high surfaces of GR/AuNCs, and Exo III-assisted target recycling amplification, we realized high sensitivity and good selectivity detection of target HIV DNA with a detection limit of 30 aM (S/N = 3). Furthermore, the proposed biosensor has a promising potential application for target detection in human serum analysis.

In this paper, the phase-stepping technique is applied to improve a phase-sensitive surface plasmon resonance biosensor based on differential interferometry between focused radially polarized and azimuthally polarized cylindrical vector beams. Detailed analysis is presented for the phase-stepping method, and the least squares unwrapping algorithm is employed to detect the phase distribution in correspondence to the refractive index of sample. Benefiting from the phase-stepping technique, both the measurement speed and sensitivity are improved significantly. The proposed sensor maintains high sensitivity of 9.4×10 -7   RIU/1° and a wide dynamic range of 0.35 RIU simultaneously. Furthermore, the real-time binding reaction process of bovine serum albumin with antibody is monitored to verify the system for potential biological applications.

Differential phase measurement between radially polarized (RP) and azimuthally polarized (AP) beams is an important technique in microscopic surface plasmon resonance (SPR) biosensors as reported in our earlier works [Opt. Lett.37, 2091 (2012); Appl. Phys. Lett.102, 011114 (2013)]. However, such a technique suffers complex beam splitting, detection, and data processing procedures for RP and AP beams which may lower the accuracy of phase measurement. In this Letter, a novel plasmonic petal-shaped vector beam is proposed instead of RP and AP beams, greatly simplifying the sensor system and enabling single measurement in differential interferometry. Moreover, an improved ultrahigh sensitivity on the order of 10(-7) refractive index units (RIUs) is experimentally verified in the proposed system.