A dual-recognition strategy based on pH-responsive molecularly imprinted membrane for highly selective capture of catecholamines: From construction to practical application.

BACKGROUND: Catecholamines (CAs) are involved in a wide range of physiological and pathological processes in the body and are progressively being used as important biomarkers for a variety of diseases. It is of great significance for accurate quantification of CAs to the diagnosis and treatment of diseases. However, the separation of CAs from complex biological matrices is still a great challenge due to the trace levels of CAs and the limited selectivity of existing pretreatment methods. RESULTS: In this work, a dual-recognition imprinted membrane (BA-MIM) was developed to utilize the synergistic action of pH-responsive boron affinity and molecular imprinted cavities for highly selective capture and release of CAs. The prepared BA-MIM possessed remarkable adsorption capacity (maximum capacity, 43.3 mg g-1), desirable surface hydrophilicity (46.2°), superior selectivity (IF = 6.2, α = 14.3), as well as favorable reusability (number of cycles, 6 times). On this basis, an integrated analytical method based on BA-MIM extraction combined with ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was innovatively developed to highly selective separation, enrichment, and detection of CAs in rat brain tissue. Under the optimum conditions, a low quantitation limits (0.05-0.10 ng mL-1), wide linear range (10-1000 ng mL-1), good linearity (r2 > 0.99), and satisfactory recoveries (88.5%-98.5 %) were obtained for CAs. The proven method was further applied to kidney-yang-deficiency-syndrome (KYDS) group rat model, revealed the intrinsic connection between kidney disease and catecholamine metabolism. SIGNIFICANCE: This work provides an excellent reference paradigm for the effective construction of dual-recognition functional membrane material to the high-selective analysis of trace targets in complex matrices. Additionally, this integrated analytical strategy demonstrates its efficiency, sustainability, versatility, and convenience, showing remarkable prospect in a variety of applications for biological sample analysis.

Highly sensitive SERS nanoplatform based on aptamer and vancomycin for detection of S. aureus and its clinical application.

Staphylococcus aureus (S. aureus) is the most common pathogen in human purulent infections, which can cause local purulent infections, as well as pneumonia, pseudomembranous enteritis, pericarditis, and even systemic infections. The conventional methods including bacteria colony counting, polymerase chain reaction and enzyme-linked immunosorbent assay can't fully meet the requirement of highly sensitive detection of S. aureus due to their own disadvantages. Therefore, it's an urgent need to develop new platform to detect S. aureus in the early infection stage. In this study, a new surface-enhanced Raman scattering (SERS)-based nanoplatform based on dual-recognition of aptamer (Apt) and vancomycin (Van) was developed for the highly sensitive detection of S. aureus. The SERS nanoplatform consisted of two functional parts: aptamer-conjugated Fe3O4 magnetic nanoparticles (Fe3O4-Apt MNPs) for bacteria enrichment and vancomycin modified-Au nanoparticles (Van-Au NPs) as the SERS probes for S. aureus quantitative detection. Upon the target bacteria enrichment, the SERS signals of the supernatant after magnetic separation could be obtained and analyzed under different concentrations of S. aureus. The limit of detection of the proposed assay was found to be 3.27 CFU/mL. We believe that the proposed SERS-based nanoplatform has great potential as a powerful tool in the early detection of specific bacteria.

Engineering of dual recognition functional aptamer-molecularly imprinted polymeric solid-phase microextraction for detecting of 17ß-estradiol in meat samples.

In this study, an enhanced selective recognition strategy was employed to construct a novel solid-phase microextraction fiber coating for the detection of 17ß-estradiol, characterized by the combination of aptamer biorecognition and molecularly imprinted polymer recognition. Benefiting from the combination of molecularly imprinted and aptamer, aptamer-molecularly imprinted (Apt-MIP) fiber coating had synergistic recognition effect. The effects of pH, ion concentration, extraction time, desorption time and desorption solvent on the adsorption capacity of Apt-MIP were investigated. The adsorption of 17ß-estradiol on Apt-MIP followed pseudo-second order kinetic model, and the Freundlich isotherm. The process was exothermic and thermodynamically spontaneous. Compared with polymers that only rely on imprinted recognition, non-imprinted recognition or aptamer affinity, Apt-MIP had the best recognition performance, which was 1.30-2.20 times that of these three materials. Furthermore, the adsorption capacity of Apt-MIP for 17ß-estradiol was 885.36-1487.52 times than that of polyacrylate and polydimethylsiloxane/divinylbenzone commercial fiber coatings. Apt-MIP fiber coating had good stability and could be reused for more than 15 times. Apt-MIP solid-phase microextraction coupled with high-performance liquid chromatography was successfully applied to the determination of 17ß-estradiol in pork, chicken, fish and shrimp samples, with satisfactory recoveries of 79.61 %-105.70 % and low limits of detection (0.03 µg/kg). This work provides new perspectives and strategies for sample pretreatment techniques based on molecular imprinting technology and improves analytical performance.

Dual-recognition colorimetric platform based on porous Au@Pt nanozymes for highly sensitive washing-free detection of Staphylococcus aureus.

A dual-recognition strategy is reported to construct a one-step washing and highly efficient signal-transduction tag system for high-sensitivity colorimetric detection of Staphylococcus aureus (S. aureus). The porous (gold core)@(platinum shell) nanozymes (Au@PtNEs) as the signal labels show highly efficient peroxidase mimetic activity and are robust. For the sake of simplicity the detection involved the use of a vancomycin-immobilized magnetic bead (MB) and aptamer-functionalized Au@PtNEs for dual-recognition detection in the presence of S. aureus. In addition, we designed a magnetic plate to fit the 96-well microplate to ensure consistent magnetic properties of each well, which can quickly remove unreacted Au@PtNEs and sample matrix while avoiding tedious washing steps. Subsequently, Au@PtNEs catalyze hydrogen peroxide (H2O2) to oxidize 3,3',5,5'-tetramethylbenzidine (TMB) generating a color signal. Finally, the developed Au@PtNEs-based dual-recognition washing-free colorimetric assay displayed a response in the range of S. aureus of 5 × 101-5 × 105 CFU/mL, and the detection limit was 40 CFU/mL within 1.5 h. In addition, S. aureus-fortified samples were analyzed to further evaluate the performance of the proposed method, which yielded average recoveries ranging from 93.66 to 112.44% and coefficients of variation (CVs) within the range 2.72-9.01%. These results furnish a novel horizon for the exploitation of a different mode of recognition and inexpensive enzyme-free assay platforms as an alternative to traditional enzyme-based immunoassays for the detection of other Gram-positive pathogenic bacteria.

Dual-recognition "turn-off-on" fluorescent Biosensor triphenylamine-based continuous detection of copper ion and glyphosate applicated in environment and living system.

Heavy metal Cu2+ emitted in industry and residues of glyphosate pesticides are pervasive in ecosystems, accumulated in water bodies and organisms' overtime, constituting hazard to human and ecological balance. The development of rapid, highly selective, reversibility and sensitive biosensor in vivo detection for Cu2+ and glyphosate was imminent. A novel dual-recognition fluorescence biosensor MPH was successfully synthesized based on triphenylamine, which demonstrated remarkable ratiometric fluorescence quenching toward Cu2+, while MPH-Cu2+ (1:1) ensemble exhibited ratiometric fluorescence restoration for glyphosate, both with observable color changes in daylight and UV lamp. The biosensor exhibited rapid, outstanding selectivity, anti-interference, and multiple cycles reversibility through "turn-off-on" fluorescence towards Cu2+ and glyphosate, respectively. Surprisingly, the clearly binding mechanisms of MPH to Cu2+ and MPH-Cu2+ ensemble to glyphosate were determined, respectively, based on the Job's plot, FT-IR, ESI-HRMS, 1H NMR titration and theoretical calculations of dynamics and thermodynamics. In addition, biosensor MPH demonstrated successful detection of Cu2+ and glyphosate across diverse environmental samples including tap water, extraction solutions of traditional Chinese medicine honeysuckle and soil samples. In the meantime, fluorescence imaging of Cu2+ and glyphosate at both micro and macro scales in various living organisms, such as rice roots, MCF-7 cells, zebrafish, and mice, were successfully achieved. Overall, this work was expected to become a promising and versatile fluorescence biosensor for rapid and reversible detection of Cu2+ and glyphosate both in vitro and vivo.

Preparation of dual recognition adsorbents based on molecularly imprinted polymers and aptamer for highly sensitive recognition and enrichment of ochratoxin A.

In light of the significant risks that mycotoxins posed to public health and environmental safety, this research developed an adsorbent MIPs/Apt/AuNPs@ZIF-67 (MA-AZ) utilizing a dual-recognition approach combining molecularly imprinted polymers (MIPs) and aptamer (Apt). This innovative method enabled the effective and highly selective recognition and enrichment of ochratoxin A (OTA). ZIF-67 was utilized as a carrier with a substantial specific surface area, and gold nanoparticles (AuNPs) were loaded on its surface to fix the thiol-modified Apt on the surface of the carrier. Then, an initiator was used to initiate a polymerization reaction, and the generated MIPs coated Apt/AuNPs@ZIF-67, thereby synthesizing the MA-AZ with a "synergistic recognition" effect. The Apt significantly increased the number of recognition sites within the imprinted cavities, and MIPs played roles in identifying targets, fixing and protecting Apt. The combination of the both produced the effect of "1+1>2". The study on the adsorption performance of MA-AZ found that the adsorption capacity of MA-AZ could reach 65.1 mg/g, and the imprinted factor was 5.48. In addition, MA-AZ exhibited excellent stability, specificity, reusability and recovery rate. Thus, this study offers valuable insights for the recognition and enrichment of hazardous substances, and helps to promote the rapid development of safety detection.

A novel dual-recognition fluorescent biosensor for sialyl-Lewisx sensitive detection.

Sialyl-Lewisx (SLex) is a tetrasugar, which plays an important role in initial inflammation and cancer cell metastasis, and can be used as a marker for cancer diagnosis and prognosis or a therapeutic target. Detecting SLex from complex biological media remains a significant challenge. Herein, a single-stranded DNA aptamer of SLex was screened based on the double-stranded DNA library-modified magnetic bead (MB)-SELEX technology. After 14 rounds of screening, 12,639 sequences were obtained and divided into nine families. Three representative sequences were selected based on the number of sequence repeats and Gibbs binding free energy, and the aptamer SLex-Apt2 with 80 nt length (Kd = 23.01 nM) had the best affinity and relatively high specificity for targeting SLex. Then, a novel dual-recognition fluorescent biosensor for SLex-sensitive detection based on aptamer SLex-Apt2 bio-dots and 3-aminobenzoboric acid-modified MB was developed. This method can detect SLex as low as 32 µM and has a good linear response in the range 100 µM to 2 mM. It has the advantages of low preparation cost, good targeting, and avoiding the occurrence of false-positive and false-negative detection results, which makes the biosensor more valuable in biological detection and clinical diagnosis.

A molecularly imprinted electrochemical aptasensor-based dual recognition elements for selective detection of dexamethasone.

In this work, a novel molecularly imprinted electrochemical aptasensor (MIEAS) was developed for highly selective detection of dexamethasone (Dex) in natural water environment. Gold nanoparticles (AuNPs) modified by nitrogen doped molybdenum carbide-graphene (N-Mo2C-Gr) were employed as the supports, where N-Mo2C-Gr improved the conductivity of the electrode and provided a larger specific surface area to polymerize more active substances. Using Dex as template molecule, o-phenylenediamine (o-PD) as the chemical functional monomer and aptamer as the biofunctional monomer, a molecularly imprinted polymer (MIP) membrane with Dex specific recognition sites was formed by electropolymerization. Due to the synergistic effect of MIP and aptamers, the as-prepared MIEAS exhibited a decent linear relationship to Dex detection within a relatively wide range of 10-13 - 10-5 M, and the detection limit was 1.79 × 10-14 M. The recovery in actual water and tablet samples is satisfactory, which confirms the potential application prospects of this sensor in the determination of Dex.

Modularization of dual recognized CRISPR/Cas12a system for the detection of Staphylococcus aureus assisted by hydrazone chemistry.

In this work, a dual recognized CRISPR/Cas12a system has been proposed, in which the activation chain is cleverly divided into two parts that can serve for precise dual target recognition, and hydrazone chemistry is introduced for the formation of a whole activation chain. It has been further explored to construct a new method for the specific and sensitive detection of Staphylococcus aureus (SA) as one of the most common pathogens in infectious diseases. In virtue of proximity effect contributed by complementary base pairing, hydrazone chemistry accelerates the formation of the whole activation strand and improves the specificity of the CRISPR/Cas12a system, serving for the accurate analysis of SA. Moreover, the temporary aggregation of CRISPR/Cas12a around SA enhances its catalytical efficiency so as to further amplify signal. With high sensitivity, stability, reproducibility and specificity, the established method has been successfully applied to detect SA in complex substrates. Meanwhile, our established method can well evaluate the inhibition effect of chlorogenic acid and congo red in comparison with flow cytometry. ENVIRONMENTAL IMPLICATION: Bacterial pathogens exist widely in the environment and seriously threaten the safety of human health. Staphylococcus aureus (SA) is the most common pathogen of human suppurative infection, which can cause local suppurative infection, pneumonia, and even systemic infections such as sepsis. In this work, a dual recognized CRISPR/Cas12a system mediated by hydrazone chemistry has been proposed. With high sensitivity and low detection limit, the established method can specifically detect SA and effectively evaluate the antibacterial effect of inhibitors. This method is expected to be further developed into a detection method in different scenarios such as environmental monitoring and clinical diagnosis.

A dual recognition-based strategy employing Ni-modified metal-organic framework for in situ screening of SIRT1 inhibitors from Chinese herbs.

Sirtuin1 (SIRT1), an NAD+-dependent histone deacetylase, plays a crucial role in regulating molecular signaling pathways. Recently, inhibition of SIRT1 rather than its activation shows the therapeutic potential for central nervous system disorder, however, the discovered SIRT1 inhibitors remains limited. In this work, a dual recognition-based strategy was developed to screen SIRT1 inhibitors from natural resources in situ. This approach utilized a Ni-modified metal-organic framework (Ni@Tyr@UiO-66-NH2) along with cell lysate containing an engineered His-tagged SIRT1 protein, eliminating the need for purified proteins, pure compounds, and protein immobilization. The high-performance Ni@Tyr@UiO-66-NH2 was synthesized by modifying the surface of UiO-66-NH2 with Ni2+ ions to specifically capture His-tagged SIRT1 while persevering its enzyme activity. By employing dual recognition, in which Ni@Tyr@UiO-66-NH2 recognized SIRT1 and SIRT1 recognized its ligands, the process of identifying SIRT1 inhibitors from complex matrix was vastly streamlined. The developed method allowed the efficient discovery of 16 natural SIRT1 inhibitors from Chinese herbs. Among them, 6 compounds were fully characterized, and suffruticosol A was found to have an excellent IC50 value of 0.95 ±â€¯0.12 µM. Overall, an innovative dual recognition-based strategy was proposed to efficiently identify SIRT1 inhibitors in this study, offering scientific clues for the development of drugs targeting CNS disorders.

A magnetic graphene oxide and UiO-66 based homogeneous dual recognition electrochemical aptasensor for accurate and sensitive detection of aflatoxin B1.

Aflatoxin (AFs) contamination is one of the serious food safety issues. Aflatoxin B1 (AFB1) is the most common and toxic aflatoxin, which has been classified as a class 1 carcinogen by the International Agency for Research on Cancer (IARC). It is extremely destructive to liver tissue. Developing a convenient and sensitive detection technique is essential. In this paper, we developed a homogeneous dual recognition strategy based electrochemical aptasensor for accurate and sensitive detection of aflatoxin B1 (AFB1) based on the magnetic graphene oxide (MGO) and UiO-66. The MGO was synthesized for the recognition and magnetic separation of AFB1 from complex samples. UiO-66/ferrocenecarboxylic acid (Fc)/aptamer composites were constructed as both recognition and signal probes. The probes would specifically capture AFB1 enriched by MGO, which enables dual recognition in homogeneous solution, thus further improving the accuracy of AFB1 detection. The electrochemical aptasensor for AFB1 had a linear range from 0.005 to 500 ng mL-1. Additionally, the limit of detection was 1 pg mL-1. It shows a favorable potential for both sensitive and accurate detection of AFB1 in real samples.

Time-resolved fluorescence immunoassay based on glucose oxidase-encapsulated metal-organic framework for amplified detection of foodborne pathogen.

BACKGROUND: Fluorescence immunoassays are commonly employed for the detection of pathogenic bacteria as a means of ensuring food safety and preserving public health. However, the challenges such as poor photostability and background interference have limited their sensitivity and accuracy. The emergence of metal-organic frameworks (MOFs) as a label probe offers a promising solution for advancing fluorescence immunoassays owing to their tunable nature. Nonetheless, the low fluorescence efficiency of MOFs and the potential risk of dye leakage pose obstacles to achieving high detection sensitivity. Therefore, there exists a pressing need to fully utilize the potential of MOF composites in fluorescence immunoassays. RESULTS: We explored the potential of glucose oxidase-encapsulated zeolitic imidazole framework-90 (GOx@ZIF-90) as a label probe to construct a time-resolved fluorescence immunoassay with amplified detection signal. This immunoassay involved functionalizing Fe3O4 nanoparticle with porcine antibody to specifically capture and separate the target bacteria, Staphylococcus aureus (S. aureus). The captured S. aureus was then bound by GOx@ZIF-90 modified with vancomycin, resulting in a fluorescence response in the europium tetracycline (EuTc). The encapsulation of GOx in ZIF-90 provided a confinement effect that significantly enhanced the catalytic activity and stability of GOx. This led to a highly efficient conversion of glucose to H2O2, amplifying the fluorescence signal of EuTc. The immunoassay demonstrated a high sensitivity in detecting S. aureus, with a detection limit of 2 CFU/mL. We also obtained satisfactory results in milk samples. Attractively, the time-resolved detection mode of EuTc allowed the immunoassay to eliminate background fluorescence and enhance accuracy. SIGNIFICANCE: This study not only presented a new method for detecting foodborne pathogens but also highlighted the potential of enzyme-encapsulated MOF composites as label probes in immunoassays, providing valuable insights for the design and fabrication of MOF composites for various applications.

Development of a Magnetically-Assisted SERS Biosensor for Rapid Bacterial Detection.

Introduction: Ultrasensitive bacterial detection methods are crucial to ensuring accurate diagnosis and effective clinical monitoring, given the significant threat bacterial infections pose to human health. The aim of this study is to develop a biosensor with capabilities for broad-spectrum bacterial detection, rapid processing, and cost-effectiveness. Methods: A magnetically-assisted SERS biosensor was designed, employing wheat germ agglutinin (WGA) for broad-spectrum recognition and antibodies for specific capture. Gold nanostars (AuNSs) were sequentially modified with the Raman reporter molecules and WGA, creating a versatile SERS tag with high affinity for a diverse range of bacteria. Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) antibody-modified Fe3O4 magnetic gold nanoparticles (MGNPs) served as the capture probes. Target bacteria were captured by MGNPs and combined with SERS tags, forming a "sandwich" composite structure for bacterial detection. Results: AuNSs, with a core size of 65 nm, exhibited excellent storage stability (RSD=5.6%) and demonstrated superior SERS enhancement compared to colloidal gold nanoparticles. Efficient binding of S. aureus and P. aeruginosa to MGNPs resulted in capture efficiencies of 89.13% and 85.31%, respectively. Under optimized conditions, the developed assay achieved a limit of detection (LOD) of 7 CFU/mL for S. aureus and 5 CFU/mL for P. aeruginosa. The bacterial concentration (10-106 CFU/mL) showed a strong linear correlation with the SERS intensity at 1331 cm-1. Additionally, high recoveries (84.8% - 118.0%) and low RSD (6.21% - 11.42%) were observed in spiked human urine samples. Conclusion: This study introduces a simple and innovative magnetically-assisted SERS biosensor for the sensitive and quantitative detection of S. aureus or P. aeruginosa, utilizing WGA and antibodies. The developed biosensor enhances the capabilities of the "sandwich" type SERS biosensor, offering a novel and effective platform for accurate and timely clinical diagnosis of bacterial infections.

Research progress on preparation methods and sensing applications of molecularly imprinted polymer-aptamer dual recognition elements.

The aptamer (Apt) and the molecularly imprinted polymer (MIP), as effective substitutes for antibodies, have received widespread attention from researchers because of their creation. However, the low stability of Apt in harsh detection environment and the poor specificity of MIP have hindered their development. Therefore, some researchers have attempted to combine MIP with Apt to explore whether the effect of "1 + 1 > 2" can be achieved. Since its first report in 2013, MIP-Apt dual recognition elements have become a highly focused research direction in the fields of biology and chemistry. MIP-Apt dual recognition elements not only possess the high specificity of Apt and the high stability of MIP in harsh detection environment, but also have high sensitivity and affinity. They have been successfully applied in medical diagnosis, food safety, and environmental monitoring fields. This article provides a systematic overview of three preparation methods for MIP-Apt dual recognition elements and their application in eight different types of sensors. It also provides effective insights into the problems and development directions faced by MIP-Apt dual recognition elements.

Coffee grounds-derived carbon quantum dots as peroxidase mimetics for colorimetric and fluorometric detection of ascorbic acid.

In this study, we reported the eco-responsible synthesis of iron-doped carbon quantum dots (Fe-CQDs) from waste coffee grounds through a simple hydrothermal method. The Fe-CQDs exhibited high peroxidase-like activity, which could convert 3,3',5,5'-tetramethylbenzidine (TMB) into blue ox-TMB in the presence of H2O2. After adding ascorbic acid (AA) to above system, the blue solution faded. Based on this phenomenon, a colorimetric method for visual monitoring of H2O2 and AA was developed. Meanwhile, the fluorescence of Fe-CQDs can be quenched by the formed ox-TMB via inner filter effect (IFE), followed by the recovery upon the addition of AA. Therefore, Fe-CQDs can be acted as a fluorescent probe to detect H2O2 and AA through the "on-off-on" mode. Furthermore, the dual-recognition methods based on Fe-CQDs were used to measure AA content in beverage samples. Thus, this work would shed much light on converting waste into biomass CQDs and their potential applications in biomolecular detection.

A SERS bioassay based on vancomycin-modified PEI-interlayered nanocomposite and aptamer-functionalized SERS tags for synchronous detection of Acinetobacter baumannii and Klebsiella pneumoniae.

Klebsiella pneumoniae (KP) and Acinetobacter baumannii (AB) are two important gram-negative bacteria that cause pneumonia and have been recently known to be associated with food. The rapid detection of these pathogens in food is important to minimize their colonization of the gut and stop new threats of the disease from spreading across the food chain. Herein, a double-edged sword aptasensor was developed for the synchronous detection of KP and AB in food and clinical samples. A highly sensitive, selective, specific, and synchronous detection of the target bacteria was achieved, and the limit of detection (LOD) was 10 cells/mL with a liner range of 50 to 105 cells/mL. The total assay time was 1.5 h. This study does not only provide a new tool for the detection of the target bacteria, but also serves as a promising tool for food safety and pneumonia diagnosis.

Dual recognition elements for selective determination of progesterone based on molecularly imprinted electrochemical aptasensor.

A novel molecularly imprinted electrochemical aptasensor (MIEAS) was constructed for selective progesterone (P4) detection based on SnO2-graphene (SnO2-Gr) nanomaterial and gold nanoparticles (AuNPs). SnO2-Gr with a large specific area and excellent conductivity improved the adsorption capacity of P4. Aptamer, as biocompatible monomer, was captured by AuNPs on modified electrode through Au-S bond. An electropolymerized molecularly imprinted polymer (MIP) film consisted of p-aminothiophenol as chemical functional monomer and P4 as template molecule. Due to the synergetic effect of MIP and aptamer towards P4, this MIEAS exhibited better selectivity than the sensor with MIP or aptamer as single recognition element. The prepared sensor had a low detection limit of 1.73 × 10-15 M in a wide linear range from 10-14 M to 10-5 M. Satisfactory recovery obtained in tap water and milk samples proved that this sensor had great potential in environmental and food analysis.

Two-step förster resonance energy transfer amplification for ratiometric detection of pathogenic bacteria in food samples.

We described a two-step förster resonance energy transfer (FRET) system for ratiometric Staphylococcus aureus (S. aureus) detection based on a dual-recognition proximity binding-induced toehold strand displacement reactions (TSDR). Ru(bpy)32+ and platinum nanoparticles (Pt NPs) labeled DNA (Ru-S3 and Pt NPs-S4) hybridized to enable the occurrence of the primary FRET using Ru(bpy)32+ as the energy donor and Pt NPs as the energy acceptor. TSDR happened by integrating vancomycin hydrochloride labeled S1 (Van-S1) and gold nanoclusters labeled S2-aptamer (Au NCs-S2-aptamer) with S. aureus. The single DNA segments of Van-S1 bond to the terminal toehold of Ru-S3, displacing Pt-S4, inducing the secondary FRET using Au NCs as the energy donor and Ru(bpy)32+ as the energy acceptor. This two-step FRET system efficiently improved the reaction efficiency of S. aureus with a detection limit of 1.0 CFU/mL. Furthermore, satisfactory results obtained while detecting S. aureus in food samples, indicating a great potential for food analysis.

Detection of rare CTCs by electrochemical biosensor built on quaternary PdPtCuRu nanospheres with mesoporous architectures.

Circulating tumor cells (CTCs) are promising liquid biopsy biomarkers for early cancer detection and anti-cancer therapy evaluation. The ultra-low abundance of CTCs in blood samples requires highly sensitive and accurate detection ways. In this study, we propose the design of a dual-recognition electrochemical biosensor to improve both the specificity and signal response. PdPtCuRu mesoporous nanospheres (PdPtCuRu MNSs) with excellent three dimensions (3D) nanopore structures were synthesized by one-pot method and connected to mucin 1 (MUC1) aptamer to serve as signal amplification probe. Besides, superconductive carbon black, Ketjen Black (KB), and gold nanoparticles (AuNPs) modified organometallic frame (CeMOF-Au) were combined to work as signal transducer. The characteristic branching structure of KB provides abundant contact points to load CeMOF-Au to heighten the interface electron transfer rate. In addition, AuNPs were reduced on the surface of CeMOF, which could effectively bind the capture antibody and further enhance the conductivity. Under the optimized condition, the limit of detection (LOD) of the as-constructed biosensor was less than 10 cells mL-1 for model A549 cells, and showed good specificity and accuracy in spiked serum samples. We envision the as-proposed electrochemical biosensor would alternate as a useful tool for the clinical detection of CTCs for cancer diagnosis.

Simultaneous detection of foodborne pathogenic bacteria in milk by fluorescence immunoassay.

Rapid, sensitive and simultaneous detection of multiple bacteria in foodborne is still a major challenge in public health field. Here, a fluorescence immunoassay that can achieve high-throughput detection of three Gram-positive foodborne pathogenic bacteria simultaneously was proposed. Vancomycin and bovine serum albumin conjugate (Van-BSA) was immobilized on a polycarbonate chip to capture three Gram-positive foodborne pathogenic bacteria, Staphylococcus aureus (S. aureus), Bacillus cereus (B. cereus) and Listeria monocytogenes (L. monocytogenes). CdSe/ZnS quantum dot modified antibodies (Ab-QD) were prepared by carbodiimide coupling chemistry. Due to the affinity reaction between antibodies and proteins on the bacterial surface, the simultaneous detection of multiple Gram-positive bacteria was achieved by monitoring the fluorescence signal of quantum dot by a portable microfluidic chip analyzer. Under optimal conditions, low detection limits was 18 CFU/well, 3 CFU/well and 36 CFU/well for S. aureus, B. cereus and L. monocytogenes, respectively. With satisfactory accuracy and precision, the proposed fluorescence immunoassay holds good prospects to detect pathogens in real food samples.