Ultrasensitive and Highly Selective Detection of Staphylococcus aureus at the Single-Cell Level Using Bacteria-Imprinted Polymer and Vancomycin-Conjugated MnO2 Nanozyme.

Pathogenic bacterial infections, even at extremely low concentrations, pose significant threats to human health. However, the challenge persists in achieving high-sensitivity bacterial detection, particularly in complex samples. Herein, we present a novel sandwich-type electrochemical sensor utilizing bacteria-imprinted polymer (BIP) coupled with vancomycin-conjugated MnO2 nanozyme (Van@BSA-MnO2) for the ultrasensitive detection of pathogenic bacteria, exemplified by Staphylococcus aureus (S. aureus). The BIP, in situ prepared on the electrode surface, acts as a highly specific capture probe by replicating the surface features of S. aureus. Vancomycin (Van), known for its affinity to bacterial cell walls, is conjugated with a Bovine serum albumin (BSA)-templated MnO2 nanozyme through EDC/NHS chemistry. The resulting Van@BSA-MnO2 complex, serving as a detection probe, provides an efficient catalytic platform for signal amplification. Upon binding with the captured S. aureus, the Van@BSA-MnO2 complex catalyzes a substrate reaction, generating a current signal proportional to the target bacterial concentration. The sensor displays remarkable sensitivity, capable of detecting a single bacterial cell in a phosphate buffer solution. Even in complex milk matrices, it maintains outstanding performance, identifying S. aureus at concentrations as low as 10 CFU mL-1 without requiring intricate sample pretreatment. Moreover, the sensor demonstrates excellent selectivity, particularly in distinguishing target S. aureus from interfering bacteria of the same genus at concentrations 100-fold higher. This innovative method, employing entirely synthetic materials, provides a versatile and low-cost detection platform for Gram-positive bacteria. In comparison to existing nanozyme-based bacterial sensors with biological recognition materials, our assay offers distinct advantages, including enhanced sensitivity, ease of preparation, and cost-effectiveness, thereby holding significant promise for applications in food safety and environmental monitoring.

Simultaneous Detection of Multiple Respiratory Pathogens Using an Integrated Microfluidic Chip.

Respiratory pathogens pose significant challenges to public health, demanding efficient diagnostic methods. This study presents an integrated microfluidic chip for the simultaneous detection of multiple respiratory pathogens. The chip integrates magnetic bead-based nucleic acid extraction and purification, acoustic streaming-driven mixing, liquid equalization, and multiplex PCR amplification with in situ fluorescence detection. Nucleic acid extraction takes only 12 min, yielding results comparable to commercial kits. Efficient mixing of magnetic beads is achieved through a combination of designed micropillars and bubble-trapping array structures. The micropillars maintain the aqueous phase in the mixing chamber, while the bubble-trapping arrays enable stable formation of bubbles, serving as a micromixer under the acoustic field. To prevent cross-contamination, an oil-encapsulated water droplet system is incorporated throughout nucleic acid extraction and PCR amplification. This assay displays remarkable multiplex analysis capability on a single chip, enabling the simultaneous detection of 12 common respiratory pathogens with a low detection limit of 10 copies/µL. Moreover, this method demonstrates excellent practical applicability in clinical nasal samples. Compared to many microfluidic chip-based molecular biology methods, the assay exhibits comparable or superior multipathogen analysis capability, sensitivity, and speed, completing the sample-to-answer process in approximately 70 min. This integrated microfluidic device offers a promising multiplex molecular diagnosis platform for on-site simultaneous detection of multiple pathogens.

Dual Synthetic Receptor-Based Sandwich Electrochemical Sensor for Highly Selective and Ultrasensitive Detection of Pathogenic Bacteria at the Single-Cell Level.

Sensitive and rapid detection of pathogenic bacteria is essential for effective source control and prevention of microbial infectious diseases. However, it remains a substantial challenge to rapidly detect bacteria at the single-cell level. Herein, we present an electrochemical sandwich sensor for highly selective and ultrasensitive detection of a single bacterial cell based on dual recognition by the bacteria-imprinted polymer film (BIF) and aptamer. The BIF was used as the capture probe, which was in situ fabricated on the electrode surface within 15 min via electropolymerization. The aptamer and electroactive 6-(Ferrocenyl)hexanethiol cofunctionalized gold nanoparticles (Au@Fc-Apt) were employed as the signal probe. Once the target bacteria were anchored on the BIF-modified electrode, the Au@Fc-Apt was further specifically bound to the bacteria, generating enhanced current signals for ultrasensitive detection of Staphylococcus aureus down to a single cell in phosphate buffer solution. Even in the complex milk samples, the sensor could detect as low as 10 CFU mL-1 of S. aureus without any complicated pretreatment except for 10-fold dilution. Moreover, the current response to the target bacteria was hardly affected by the coexisting multiple interfering bacteria, whose number is 30 times higher than the target, demonstrating the excellent selectivity of the sensor. Compared with most reported sandwich-type electrochemical sensors, this assay is more sensitive and more rapid, requiring less time (1.5 h) for the sensing interface construction. By virtue of its sensitivity, rapidity, selectivity, and cost-effectiveness, the sensor can serve as a universal detection platform for monitoring pathogenic bacteria in fields of food/public safety.

Physicochemical and functional property of the Maillard reaction products of soy protein isolate with L-arabinose/D-galactose.

BACKGROUND: Soy protein isolate (SPI) is widely used in the food industry because of its nutritional and functional properties. During food processing and storage, the interaction with co-existing sugars can cause changes in the structural and functional properties of SPI. In this study, SPI-l-arabinose conjugate (SPI:Ara) and SPI-d-galactose conjugate (SPI:Gal) were prepared using Maillard reaction (MR), and the effects of five-carbon/six-carbon sugars on the structural information and function of SPI were compared. RESULTS: MR unfolded and stretched the SPI, changing its ordered conformation into disorder. Lysine and arginine of SPI were bonded with the carbonyl group of sugar. The MR between SPI and l-arabinose has a higher degree of glycosylation compared to d-galactose. MR of SPI enhanced its solubility, emulsifying property and foaming property. Compared with SPI:Ara, SPI:Gal exhibited better aforementioned properties. The functionalities of amphiphilic SPI were enhanced by MR, SPI:Gal possessed better hypoglycemic effect, fat binding capacity and bile acid binding ability than SPI:Ara. MR endowed SPI with enhanced biological activities, SPI:Ara showed higher antioxidant activities, and SPI:Gal exhibited stronger antibacterial activities. CONCLUSION: Our work revealed that l-arabinose/d-galactose exhibited different effects on the structural information of SPI, and further affected its physicochemical and functional property. © 2023 Society of Chemical Industry.

Reusable and universal impedimetric sensing platform for the rapid and sensitive detection of pathogenic bacteria based on bacteria-imprinted polythiophene film.

The rapid and sensitive detection of pathogenic bacteria is highly demanded for early warning of infectious disease epidemics and protection of human health. Herein, a reusable and universal impedimetric sensing platform based on a bacteria-imprinted polythiophene film (BIF) is proposed for the rapid and sensitive detection of pathogenic bacteria using Staphylococcus aureus (S. aureus) as a model analyte. Monomer screening among four 3-substituted thiophenes was first performed based on the imprinting factor, and 3-thiopheneethanol (TE) was eventually selected. The BIF as a recognition layer was quickly deposited in an environmentally friendly process on a glassy carbon electrode via electro-copolymerization of the S. aureus template and TE monomer followed by in situ template removal. Upon rebinding of S. aureus on the BIF, the impedance increased. Under optimal conditions, the BIF-based sensor can quantitatively detect S. aureus in a wide linear range of 10 to 107 CFU mL-1 with a low detection limit of 4 CFU mL-1. Additionally, the sensor exhibits excellent selectivity, capable of identifying S. aureus from multi-bacterial strain mixtures. It also demonstrates applicability in the analysis of real lettuce and shrimp samples with good recoveries. Most significantly, the BIF sensing interface can be reused up to five times with good signal retention. Compared with most reported methods, this sensor is more rapid with a much shorter total assay time of 30 min, including the BIF preparation, bacterial rebinding, and impedance detection. This assay may hold great potential to help in the rapid, sensitive, and label-free detection of pathogenic bacteria in fields of food safety and public health.

Facile Preparation of a Bacteria Imprinted Artificial Receptor for Highly Selective Bacterial Recognition and Label-Free Impedimetric Detection.

The effective identification and quantification of pathogenic bacteria is essential for addressing serious public health issues. Here, we demonstrate a simple and universal impedimetric sensor for highly selective and sensitive detection of pathogenic bacteria based on the recognition by a bacteria-imprinted polypyrrole (BIP) film. The BIP film was facilely prepared via one-step electro-polymerization followed by in situ removal of the bacterial template. The film structure is novel with noncavity-like imprinted sites situated at the surface of the polypyrrole (PPy) matrix, which are more accessible for the target bacteria and should enhance the mass transfer and the binding kinetics. A limit of quantitation low to 103 CFU/mL was achieved within 1 h for the detection of E. coli O157:H7, which is comparable to the antibody-based assays. Moreover, the sensor displayed remarkable selectivity, especially regarding the specific identification of bacterial serotypes. When employed to analyze E. coli O157:H7 in real drinking water, apple juice, and milk samples, the sensor showed recoveries from 96.0% to 107.9% with relative standard derivations (RSDs) less than 4%. The BIP-based sensing strategy provides a universal approach for specific, selective, and rapid detection of pathogenic bacteria. As compared to conventional biosensors based on biomolecular recognition, this sensor shows clear advantages including easy-of-preparation, robustness, and low cost, which may hold great potential in fields of food/public safety monitoring.

Multiplexed aptasensing of food contaminants by using terminal deoxynucleotidyl transferase-produced primer-triggered rolling circle amplification: application to the colorimetric determination of enrofloxacin, lead (II), Escherichia coli O157:H7 and tropomyosin.

A colorimetric assay is described for simultaneous detection of multiple analytes related to food safety. It is based on the use of a sandwich aptasensor and terminal deoxynucleotidyl transferase (TdT) which produces a primer for subsequent rolling circle amplification (RCA). Two split aptamer fragments (Apt1 and Apt2) are firstly immobilized, Apt1 on gold nanoparticles (AuNPs), and Apt2 on magnetic beads (MBs). They are then used in a sandwich aptasensor. In the presence of analyte, two probes could specifically recognize target and form a ternary assembly, and the magnetic beads also act to separate rapidly and enrich the target. Then, the extension of template-free DNA is triggered by TdT at the exposed 3'-hydroxy terminals of Apt1. This produces polyA sequences that serve as primers for subsequent RCA. The product of RCA is hybridized with a complementary horse radish peroxidase (HRP) DNA probe. HRP catalyzes the H2O2-mediated oxidation of tetramethylbenzidine (TMB) and forms a blue chromogenic product. After magnetic separation, the absorption values of the blue product in the supernatant are measured at a wavelength of 600 nm. Based on this dual amplification mechanism, the assay was applied to multiplexed determination of enrofloxacin (ENR), lead(II), Escherichia coli O157:H7 and tropomyosin. Exemplarily, ENR is detectable at concentrations down to 2.5 pg mL-1 with a linear range that extends from 1 pg mL-1 to 1 µg·mL-1. The assay was validated by analysis of spiked fish samples. Recoveries range between 87.5 and 92.1%. Graphical abstractSchematic representation of a TdT-RCA based aptasensor for multiple analytes related to food safety. It makes use of sandwich aptasensors and TdT-produced universal primer-triggered RCA reaction. dATP: deoxyadenosine triphosphate, TdT: Terminal Deoxynucleotidyl Transferase, RCA: rolling circle amplification, TMB: 3,3',5,5'-Tetramethylbenzidine.

Microfluidic Air Sampler for Highly Efficient Bacterial Aerosol Collection and Identification.

The early warning capability of the presence of biological aerosol threats is an urgent demand in ensuing civilian and military safety. Efficient and rapid air sample collection in relevant indoor or outdoor environment is a key step for subsequent analysis of airborne microorganisms. Herein, we report a portable battery-powered sampler that is capable of highly efficient bioaerosol collection. The essential module of the sampler is a polydimethylsiloxane (PDMS) microfluidic chip, which consisted of a 3-loop double-spiral microchannel featuring embedded herringbone and sawtooth wave-shaped structures. Vibrio parahemolyticus (V. parahemolyticus) as a model microorganism, was initially employed to validate the bioaerosol collection performance of the device. Results showed that the sampling efficacy reached as high as >99.9%. The microfluidic sampler showed greatly improved capturing efficiency compared with traditional plate sedimentation methods. The high performance of our device was attributed to the horizontal inertial centrifugal force and the vertical turbulence applied to airflow during sampling. The centrifugation field and turbulence were generated by the specially designed herringbone structures when air circulated in the double-spiral microchannel. The sawtooth wave-shaped microstructure created larger specific surface area for accommodating more aerosols. Furthermore, a mixture of bacterial aerosols formed by V. parahemolyticus, Listeria monocytogenes, and Escherichia coli was extracted by the microfluidic sampler. Subsequent integration with mass spectrometry conveniently identified the multiple bacterial species captured by the sampler. Our developed stand-alone and cable-free sampler shows clear advantages comparing with conventional strategies, including portability, easy-to-use, and low cost, indicating great potential in future field applications.

Nanoporous molybdenum carbide wires as an active electrocatalyst towards the oxygen reduction reaction.

A non-precious metal electrocatalyst has been developed for the oxygen reduction reaction based on nanoporous molybdenum carbide (nano-Mo2C) wires through a facile calcination of sub-nanometer periodic organic-inorganic hybrid nanowires. The highly dispersed Mo2C wires were composed of 10-15 nm nanocrystals with a mesopore size of 3.3 nm. The properties of nano-Mo2C wires were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and N2 adsorption/desorption porosimetry. The highly active surface area and enriched nanoporosity for nano-Mo2C wires are unique features that make them a high-performance electrocatalyst for oxygen reduction in an alkaline medium. The electrocatalysis and reaction kinetics results show that nano-Mo2C-based materials can be developed as new catalysts with high activity at low cost for electrochemical energy conversion applications.

Effect of Mono- and Polysaccharide on the Structure and Property of Soy Protein Isolate during Maillard Reaction.

As a protein extracted from soybeans, soy protein isolate (SPI) may undergo the Maillard reaction (MR) with co-existing saccharides during the processing of soy-containing foods, potentially altering its structural and functional properties. This work aimed to investigate the effect of mono- and polysaccharides on the structure and functional properties of SPI during MR. The study found that compared to oat ß-glucan, the reaction rate between SPI and D-galactose was faster, leading to a higher degree of glycosylation in the SPI-galactose conjugate. D-galactose and oat ß-glucan showed different influences on the secondary structure of SPI and the microenvironment of its hydrophobic amino acids. These structural variations subsequently impact a variety of the properties of the SPI conjugates. The SPI-galactose conjugate exhibited superior solubility, surface hydrophobicity, and viscosity. Meanwhile, the SPI-galactose conjugate possessed better emulsifying stability, capability to produce foam, and stability of foam than the SPI-ß-glucan conjugate. Interestingly, the SPI-ß-glucan conjugate, despite its lower viscosity, showed stronger hypoglycemic activity, potentially due to the inherent activity of oat ß-glucan. The SPI-galactose conjugate exhibited superior antioxidant properties due to its higher content of hydroxyl groups on its molecules. These results showed that the type of saccharides had significant influences on the SPI during MR.

Low-cost industrially available molybdenum boride and carbide as "platinum-like" catalysts for the hydrogen evolution reaction in biphasic liquid systems.

Rarely reported low-cost molybdenum boride and carbide microparticles, both of which are available in abundant quantities due to their widespread use in industry, adsorb at aqueous acid-1,2-dichloroethane interfaces and efficiently catalyse the hydrogen evolution reaction in the presence of the organic electron donor - decamethylferrocene. Kinetic studies monitoring biphasic reactions by UV/vis spectroscopy, and further evidence provided by gas chromatography, highlight (a) their superior rates of catalysis relative to other industrially significant transition metal carbides and silicides, as well as a main group refractory compound, and (b) their highly comparable rates of catalysis to Pt microparticles of similar dimensions. Insight into the catalytic processes occurring for each adsorbed microparticle was obtained by voltammetry at the liquid-liquid interface.

Rapid and Sensitive Detection of Sulfamethizole Using a Reusable Molecularly Imprinted Electrochemical Sensor.

Efficient methods for monitoring sulfonamides (SAs) in water and animal-source foods are of great importance to achieve environmental safety and protect human health. Here, we demonstrate a reusable and label-free electrochemical sensor for the rapid and sensitive detection of sulfamethizole based on an electropolymerized molecularly imprinted polymer (MIP) film as the recognition layer. To achieve effective recognition, monomer screening among four kinds of 3-substituted thiophenes was performed by computational simulation and subsequent experimental evaluation, and 3-thiopheneethanol was finally selected. MIP synthesis is very fast and green, and can be in situ fabricated on the transducer surface within 30 min in an aqueous solution. The preparation process of the MIP was characterized by electrochemical techniques. Various parameters affecting MIP fabrication and its recognition response were investigated in detail. Under optimized experimental conditions, good linearity in the range of 0.001-10 µM and a low determination limit of 0.18 nM were achieved for sulfamethizole. The sensor showed excellent selectivity, which can distinguish between structurally similar SAs. In addition, the sensor displayed good reusability and stability. Even after 7 days of storage, or being reused 7 times, higher than 90% of the initial determination signals were retained. The practical applicability of the sensor was also demonstrated in spiked water and milk samples at the nM determination level with satisfactory recoveries. Compared to relevant methods for SAs, this sensor is more convenient, rapid, economical, and eco-friendly, and had comparable or even higher sensitivity, which offered a simple and efficient method for SA detection.

A Novel Dual Bacteria-Imprinted Polymer Sensor for Highly Selective and Rapid Detection of Pathogenic Bacteria.

The rapid, sensitive, and selective detection of pathogenic bacteria is of utmost importance in ensuring food safety and preventing the spread of infectious diseases. Here, we present a novel, reusable, and cost-effective impedimetric sensor based on a dual bacteria-imprinted polymer (DBIP) for the specific detection of Escherichia coli O157:H7 and Staphylococcus aureus. The DBIP sensor stands out with its remarkably short fabrication time of just 20 min, achieved through the efficient electro-polymerization of o-phenylenediamine monomer in the presence of dual bacterial templates, followed by in-situ template removal. The key structural feature of the DBIP sensor lies in the cavity-free imprinting sites, indicative of a thin layer of bacterial surface imprinting. This facilitates rapid rebinding of the target bacteria within a mere 15 min, while the sensing interface regenerates in just 10 min, enhancing the sensor's overall efficiency. A notable advantage of the DBIP sensor is its exceptional selectivity, capable of distinguishing the target bacteria from closely related bacterial strains, including different serotypes. Moreover, the sensor exhibits high sensitivity, showcasing a low detection limit of approximately 9 CFU mL-1. The sensor's reusability further enhances its cost-effectiveness, reducing the need for frequent sensor replacements. The practicality of the DBIP sensor was demonstrated in the analysis of real apple juice samples, yielding good recoveries. The integration of quick fabrication, high selectivity, rapid response, sensitivity, and reusability makes the DBIP sensor a promising solution for monitoring pathogenic bacteria, playing a crucial role in ensuring food safety and safeguarding public health.

Colloidal SERS measurement of enrofloxacin with petaloid nanostructure clusters formed by terminal deoxynucleotidyl transferase catalyzed cytosine-constituted ssDNA.

We developed petal-like plasmonic nanoparticle (PLNP) clusters-based colloidal SERS method for enrofloxacin (EnFX) detection. PLNPs were synthesized by the regulation of single-stranded DNA composed of homo-cytosine deoxynucleotides (hC) catalyzed by terminal deoxynucleotidyl transferase. SERS hot spots were created via the agglomeration process of PLNPs by adding an inorganic salt potassium iodide solution, in which EnFX molecules were attached to the negatively charged PLNPs surface by electrostatic interactions. This approach enabled direct in situ detection of antibiotic residues, achieving a limit of detection (LOD) of 1.15 µg/kg for EnFX. The spiked recoveries of the SERS method were approximately 92.7% to 107.2% and the RSDs ranged from 1.05% to 7.8%, indicating that the method can be applied to actual sample detection. This colloidal SERS measurement platform would be very promising in various applications, especially in real-time and on-site food safety screening owing to its rapidness, simplicity, and sensitivity.

pH-controlled delivery of doxorubicin to cancer cells, based on small mesoporous carbon nanospheres.

Mesoporous carbon nanospheres (MCNs) with small diameters of ≈90 nm are developed as an efficient transmembrane delivery vehicle of an anticancer drug, doxorubicin (DOX). MCNs exhibit a high loading capacity toward DOX due to hydrophobic interactions and the supramolecular π stacking between DOX and the carbonaceous structures, on which the pH-dependent drug release are successfully achieved. Specifically, DOX can be loaded onto MCNs in basic solution and in a physiological pH range, while release occurs in acidic solution in its ionized state. By effective passive and active targeting, MCNs can be readily internalized into HeLa cells, where the carried DOX can be efficiently released in the acidic microenvironment of the tumors for further therapy. The endocytosis and cytotoxicity of DOX@MCNs toward HeLa cells are investigated by confocal microscopy and MTT assay. This smart pH-dependent drug loading and release property of DOX@MCNs makes it possible to reduce the cytotoxicity to normal tissues during circulation in the body since the normal physiological pH is ≈7.4.

A competitive colorimetric aptasensor for simple and sensitive detection of kanamycin based on terminal deoxynucleotidyl transferase-mediated signal amplification strategy.

We developed a rapid and sensitive colorimetric biosensor based on competitive recognition between kanamycin (KAN), magnetic beads-kanamycin (MBs-KAN) and aptamer and terminal deoxynucleotidyl transferase (TdT)-mediated signal amplification strategy. In the absence of KAN, aptamers recognize MBs-KAN. TdT can amplify oligonucleotides to the 3'-OH ends of aptamers, with biotin-dUTP being embedded in the long single stranded DNA (ssDNA). Then the assay produced visual readout due to the horseradish peroxidase (HRP)-catalyzed color change of the substrate after the linkage between biotin and streptavidin (SA)-HRP. In the presence of KAN, however, aptamers tend to bind free KAN rather than MBs-KAN. In this case, aptamers are isolated by magnetic separation, resulting in the failure of signal amplification and catalytic signals. This competitive colorimetric sensor showed excellent selectivity toward KAN with the limit of detection (LOD) as low as 9 pM. And recovery values were between 93.8 and 107.8% when spiked KAN in milk and honey samples.

Physical, Mechanical and Biological Properties of Phenolic Acid-Grafted Soluble Soybean Polysaccharide Films.

Three kinds of phenolic acid-grafted soluble soybean polysaccharide (SSPS) with similar grafting ratios were prepared, and their structure was characterized by FT-IR, UV-vis and 1 H NMR. The impact of phenolic acid on the antioxidant activity of SSPS was evaluated. Then, films were prepared by using phenolic acid-grafted SSPS. The physical, mechanical and biological performances of phenolic acid-grafted SSPS films were further investigated. The results indicated that an ester linkage was formed between the SSPS and phenolic acid. The grafting ratio of para-hydroxybenzoic acid, protocatechuic acid and gallic acid-grafted SSPS was 29.45, 31.76 and 30.74 mg/g, respectively. Phenolic acid endowed SSPS with improved antioxidant properties. Gallic acid (GA)-grafted SSPS possessed the best DPPH radical scavenging ability and reducing power, which may be related to the three phenolic hydroxyl groups in GA. Phenolic acid-grafted SSPS films showed increased moisture content and decreased water solubility compared to SSPS film. The phenolic acid-g-SSPS decreased the mechanical properties but enhanced the water vapor barrier property, and antioxidant and antibacterial properties of SSPS film. Meanwhile, the para-hydroxybenzoic acid-grafted SSPS film showed the lowest water vapor permeability (3.70 × 10-7 g mm/h cm2 Pa), and the GA-grafted SSPS film exhibited the best antioxidant and antibacterial activities.

Fishing unfunctionalized SERS tags with DNA hydrogel network generated by ligation-rolling circle amplification for simple and ultrasensitive detection of kanamycin.

Simple assay format-based SERS methods for sensitive target substance analysis is of great significance for the development of on-site monitoring biosensors. Herein, taking the typical antibacterial kanamycin (KANA) as a subject, a simple, highly sensitive and specific SERS aptasensor was developed by manipulating DNA hydrogel network to fish plasmonic core-shell nanoparticles. A competitive binding mode of aptamer, ligation-rolling circle amplification (L-RCA), gap-containing Au@Au nanoparticles (GCNPs) with embedded Raman reporters were integrated into the sensor. In the presence of KANA, the double stranded DNA (dsDNA) structure of the aptamer was disrupted, and the released primers were used to construct two kinds of circularized padlock probes (CPPs) which were partially complementary. DNA hydrogel network was formed through the intertwining and self-assembly of two RCA-generated single stranded DNA (ssDNA) chains, during which GCNPs and magnetic beads (MBs) were entangled and incorporated. Finally, KANA quantification was successfully achieved through the quantification of the DNA hydrogel. Overall, this novel SERS aptasensor realized a simple and ultrasensitive quantification of KANA down to 2.3 fM, plus excellent selectivity, and precision even for real food samples. In view of innovative fusion across L-RCA-based DNA hydrogel and SERS technique, the proposed method has promising potential for application in on-site detection and quantification of trace food contaminants.

[Preparation and application of DNA hydrogels: a review].

Deoxyribonucleic acid (DNA) not only serves as the material basis of biological inheritance, but also shows great potential in the development of novel biological materials due to its programmability, functional diversity, biocompatibility and biodegradability. DNA hydrogel is a three-dimensional mesh polymer material mainly formed by DNA. It has become one of the most interesting emerging functional polymer materials in recent years because of the perfect combination of the DNA biological properties that it retained and the mechanical properties of its own skeleton. At present, single- or multi-component DNA hydrogels developed based on various functional nucleic acid sequences or by combining different functional materials have been widely used in the field of biomedicine, molecular detection, and environmental protection. In this paper, the development of preparation methods and classification strategies of DNA hydrogels are summarized, and the applications of DNA hydrogels in drug delivery, biosensing and cell culture are also reviewed. Finally, the future development direction and potential challenges of DNA hydrogels are prospected.

Rapid, sensitive and label-free detection of pathogenic bacteria using a bacteria-imprinted conducting polymer film-based electrochemical sensor.

The rapid and sensitive detection of pathogenic bacteria is very important for timely prevention and treatment of foodborne disease. Here, a bacteria-imprinted conductive poly(3-thiopheneacetic acid) (BICP) film-based impedimetric sensor was developed for the rapid, sensitive and label-free detection of staphylococcus aureus (S. aureus). The BICP film preparation was very convenient and eco-friendly, which was in situ deposited on gold electrode surface without the use of toxic organic solvents and cross-linkers. The process of imprinting and recognition were characterized by electrochemical technique and scanning electron microscope. The BICP had a novel structure without cocci-shaped cavities formed in the poly(3-thiopheneacetic acid) (PTAA) matrices. To obtain the optimal sensing performance, a set of factors affecting the imprinting and recognition were investigated. Under the optimized conditions, an extremely rapid recognition within 10 min, a very low limit of detection (LOD) of 2 CFU/mL, and wide linear range from 10 to 108 CFU/mL were achieved by the BICP film-based impedimetric sensor. The sensor also demonstrated high selectivity, and good universality and repeatability. Furthermore, the feasibility of its application has also been demonstrated in the analysis of real milk samples. This sensor offered a simple and universal method for rapid, sensitive, and selective detection of pathogenic bacteria, which could hold great potentials in fields like food safety.