Relative Standard Derivation Research Articles

Headspace separation combined fluorescence detection of hydrogen sulfide with silver-sensitized lanthanide coordination polymer via a simple self-made device

Hydrogen sulfide (H2S), playing unique role on signal transmission in various physiological processes, the rapid and accurate monitoring of it is particularly concerned. The drawbacks of fluorescence probe for H2S, namely poor selectivity or long response time, have always existed. As a test case, here headspace separation combined fluorescence strategy was attempted, on basis of H2S stimuli-responsive AMP/Tb3+/Ag+ or GMP/Tb3+/Ag+ coordination polymer probes. The fluorescence intensity of them is inversely proportional to the concentration of it, due to Ag-S in situ coordination and partial formation of Ag2S. Using the hybrid analysis, a quick response of less than 2.0 min and a high selectivity could be obtained. The signal change (ΔI) of AMP/Tb3+/Ag+ or GMP/Tb3+/Ag+ showed good linearity within the range of 0.5–100 μM and 1.0–150 μM, along with a detection limit (3σ) of 0.2 and 0.4 μM, respectively. When utilized to determine the sulfide level in real samples, it shows recoveries from 96.4 % to 102.3 % with relative standard derivation (RSD) less than 3.0 %. The combination strategy of headspace separation and fluorescence quantitative analysis was verified to effectively eliminate potential interference such as other coexisting non-volatile thiol-containing species, providing a novel avenue to flexibly design the volatile component analysis with high selectivity in complex sample matrixes.

A combination of vortex-assisted liquid–liquid microextraction with fluorescence detection: An innovative approach for a green and highly sensitive determination of sodium dodecyl sulfate in water samples and pharmaceuticals

A new green, highly sensitive, and selective method based on a combination of vortex-assisted liquid–liquid microextraction with fluorescence detection (VALLME-FLD) was developed for the determination of sodium dodecyl sulfate (SDS). The method is based on the reaction of SDS with the fluorophore 3,3′-diethyloxadicarbocyanine iodide (DODC) at pH 3, followed by VALLME of the formed ion associate (IA) into a microvolume of the organic phase (n-amyl acetate). Fluorescence measurements were made at 668 nm, with excitation at 635 nm. During the optimization, the influence of various chemical and physical factors on the relative fluorescence intensity was studied. The linearity of the calibration curve was observed in two concentration ranges of SDS, from 0.30 to 3.0 µg L-1, R2 = 0.9980 (microextraction into 70 µL n-amyl acetate), and 3.0 to 14.0 µg L-1, R2 = 0.9960 (microextraction into 500 µL n-amyl acetate). The limits of detection (LOD) were 0.10 µg L-1 and 0.90 µg L-1, respectively. The accuracy and precision of the proposed method were verified during two consecutive days with a relative standard derivation of 2.2–4.9 % and recovery of 93.3–106.7 %. The system showed high selectivity towards SDS in the presence of at least 200-times higher concentrations of NO3–; 500-times higher concentrations of F-, Br-, HPO42-, and Fe2+, and 1000-times higher concentrations of CO32–, SO42-, Cl-, Mg2+, and Ca2+. The method was developed and applied to the determination of SDS/anionic surfactants in real water samples and pharmaceutical tablets.

Green hydrothermal synthesis of multifunctional carbon dots from cassava pulps for metal sensing, antioxidant, and mercury detoxification in plants

Carbon dots (CDs) have been attracted to nanocarbon materials for metal ion sensing, biological activity, and plant phytotoxicity due to their excellent photophysical properties, such as low cytotoxicity, high quantum yield, tunable fluorescence emission, and biocompatibility. Cassava pulp, which consists mainly of starch, has been identified as a low-cost biomass waste from the cassava starch industry. Therefore, this research developed CDs and nitrogen-doped CDs (NCDs) from cassava pulp using a one-step hydrothermal process in deionized water at 200 °C. The effects of the synthesis conditions, including reaction time (6–24 h) and the nitrogen doping derivatives, were also investigated. CDs and ethylenediamine doped-NCDs exhibited tunable fluorescence emission, strong quantum yield, high photostability, and tolerance to photobleaching. Furthermore, the potential applications of CDs-12 h were demonstrated such as fluorescent sensors for metal ion sensing, antioxidant activity, and mercury detoxification in plants. Fluorescence quenching of the CDs-12 h via both static and dynamic quenching mechanisms was observed in the presence of several metal ions such as Hg2+, Cu2+, and Fe3+ with the detection limit in micromolar levels and further applied to real water samples with good recovery and acceptable relative standard derivation. The paper test strip coated with CDs-12 h could also detect these metal ions under UV light. CDs and NCDs-EDA also showed potential DPPH radical scavenging activity and alleviated mercury toxicity in the Chinese cabbage seedlings with the incubation of CDs-12 h and NCDs-EDA-12 h (30 mg/L).

A highly sensitive and selective rhodamine-semicarbazide based fluorescent sensor for Cu2+ detection in real water samples and fluorescence bioimaging in HepG2 cells

A colorimetric and fluorescent sensor, selective for Cu2+ ions, was synthesized in two steps using a rhodamine-based compound attached to the semicarbazide-picolylamine moiety (RBP). Spectroscopic measurements, including UV–Vis absorption and fluorescence emission, were conducted in the semi-aqueous medium containing acetonitrile/4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, denoted as MeCN/HEPES buffer (2:8, v/v, pH 7.0). The sensor exhibited high selectivity towards Cu2+ ions compared to other cations and demonstrated remarkable sensitivity towards Cu2+ ions, with a limit of detection at the nanomolar level. The calculated transitions indicated a 1:1 stoichiometric binding of RBP to Cu2+ ions based on a 4-coordination mode involving additional chelation in the semi-aqueous medium. The sensing mechanism for the detection of Cu2+ ions was investigated using high-resolution mass spectroscopy. The sensor could be employed as a real-time chemosensor for monitoring Cu2+ ions. Furthermore, the sensor has the potential for utilization in the detection of Cu2+ ions in actual water samples with the high precision and accuracy, as indicated by the small relative standard derivation values. The 50th percentile cytotoxicity concentration of RBP was found to be 22.92 μM. Additionally, the fluorescence bioimaging capability of RBP was demonstrated for the detection of Cu2+ ions in human hepatocellular carcinoma (HepG2) cells.

Electrochemiluminescence bioassay with anti-fouling ability for determination of matrix metalloproteinase 9 secreted from living cells under external stimulation.

An electrochemiluminescence (ECL) bioassay with high sensitivity and anti-fouling ability was developed for determination of matrix metalloproteinase 9 (MMP-9) secreted from living cells under external stimulation. A peptide with sequence of CLGRMGLPGK and a new cyclometalated iridium(III) complex bearing carboxyl group, (pq)2Ir(dcbpy) (pq = 2-phenylquinoline, dcbpy = 2,2'-bipyridyl-4,4'-dicarboxyli acid, abbreviated as Ir) were employed as molecular recognition substrate and ECL emitter, respectively. The peptide was labelled with the Ir to form Ir-peptide as ECL probe. Ir-peptide was self-assembled onto Nafion and gold nanoparticles (AuNPs) modified glassy carbon electrode (AuNPs/Nafion/GCE) and then both of 6-mercapto-1-hexanol (MCH) and zwitterionic peptide as blocking reagents were co-assembled on Ir-peptide/AuNPs/Nafion/GCE to form an anti-fouling ECL peptide-based biosensor. MMP-9 can be quantified in the range 1.0-50ng·mL-1 with adetection limit of 0.50ng·mL-1 based on the decreased ECL intensity. Relative standard derivation was 2.3% for six fabricated anti-fouling ECL peptide-based biosensors after reaction with 50ng·mL-1 MMP-9. The anti-fouling ECL peptide-based biosensor can be used to monitor MMP-9 secreted from living cells under external stimulation. 96.0%-108.0% of recoveries were obtained in 60-diluted cell culture media. This study demonstrates that the ECL biosensor by the combination of iridium(III) complex-based sensitive ECL method and the anti-fouling interface provides a promising way for the determination of MMP-9 in biological sample, which is viable in clinical diagnosis and point-of-care test of protease.

Responsive luminescent silver-based metal-organic frameworks for highly sensitive and selective detection of hydrogen sulfide in biological system via a self-assembled headspace separation device

As a highly toxic gas pollutant and also an endogenous gaseous signaling molecule existing in a variety of physiological processes, the rapid and accurate in-field detection of hydrogen sulfide is of great concern. Nevertheless, two drawbacks as for the optical probes for H2S detection, taking about a long time to reach the optical signal balance or the low selectivity, always exist. Herein, by using a highly photoluminescent and H2S-stimuli responsive silver-based metal-organic frameworks (MOFs): Ag-BDC (BDC = 1, 4-benzene dicarboxylate), we demonstrated that the luminescence intensity of Ag-BDC MOFs was inversely proportional to the concentration of H2S due to the Ag–S coordination and the obstruction of ligand-to-metal charge transfer (LMCT) transition process, and there was a quick response time of below 3.0 min. Combined with a simple customized device to separate H2S from the sample, the selectivity of the method for H2S detection could be greatly improved, and no interference would be caused even if the other sulfur-containing species coexisted. The luminescence probe presented a favorable sensitivity within a linear range of 0.1–1000 μM along with a detection limit of 23.7 nM. When employed to assay the endogenous sulfide level in the human serum and mouse brain tissue, the approach showed recoveries from 96.3% to 102% with relative standard derivation (RSD) less than 2.0%. By the integration of the responsive luminescent silver-based MOFs with a simple self-assembled headspace separation device, obviously the present strategy could be beneficial to the development and design of the in-field fast H2S measurement, possessing particular advantages in biological systems to eliminate the potential interferences.

Building of a three-dimensional apta-nano interface using silver nanoflower for photoelectrochemical detection of carcinoembryonic antigen

Enhancing the sensitivity of photoelectrochemical (PEC) assays poses a challenging task. This study proposes a method to improve the sensitivity of PEC assays by creating a three-dimensional (3D) apta-nano interface using silver nanoflowers (AgNFs) with a 3D flower-like structure as a substrate. The aptamer (Apt) was immobilized on the surface of the AgNF-loaded gold nanoparticles (AuNPs) through the dual action of polyA blocking and Au-S bonding. Despite using cadmium sulfide quantum dots (CdS QDs) as the sole photoactive material, the as-prepared photoelectrode still showed excellent sensitivity. Using carcinoembryonic antigen (CEA) as a model target, the variation value of photocurrent (ΔI) exhibited good linear correlation (R2 = 0.9974) with the logarithm of CEA concentration in a wide detection range from 0.001 to 100 ng mL−1, and the detection limit was as low as 0.64 pg mL−1. In the assay of CEA in 1% serum, the recoveries reached 98.70 ∼ 99.63% with a low relative standard derivation (RSD) ranging from 1.11% to 2.05%. This study introduces novel concepts for the development of PEC sensors, potentially enhancing their utility in the clinical detection of disease markers.

A data selection method for matrix effects and uncertainty reduction for laser-induced breakdown spectroscopy

Severe matrix effects and high signal uncertainty are two key bottlenecks for the quantitative performance and wide applications of laser-induced breakdown spectroscopy (LIBS). Based on the understanding that the superposition of both matrix effects and signal uncertainty directly affects plasma parameters and further influences spectral intensity and LIBS quantification performance, a data selection method based on plasma temperature matching (DSPTM) was proposed to reduce both matrix effects and signal uncertainty. By selecting spectra with smaller plasma temperature differences for all samples, the proposed method was able to build up the quantification model to rely more on spectra with smaller matrix effects and signal uncertainty, therefore improving final quantification performance. When applied to quantitative analysis of the zinc content in brass alloys, it was found that both accuracy and precision were improved using either a univariate model or multiple linear regression (MLR). More specifically, for the univariate model, the root-mean-square error of prediction (RMSEP), the determination coefficients (R 2) and relative standard derivation (RSD) were improved from 3.30%, 0.864 and 18.8% to 1.06%, 0.986 and 13.5%, respectively; while for MLR, RMSEP, R 2 and RSD were improved from 3.22%, 0.871 and 26.2% to 1.07%, 0.986 and 17.4%, respectively. These results prove that DSPTM can be used as an effective method to reduce matrix effects and improve repeatability by selecting reliable data.

Silver nanostar films for surface-enhanced Raman spectroscopy (SERS) of the pesticide imidacloprid

Strategies for synthetic control of anisotropic metal nanostructures have grown in recent years in part due to their great potential for application as surface-enhanced Raman scattering (SERS) sensing substrates. It has been shown that SERS using silver substrates is a powerful tool for identification and qualification of trace chemical analysis on the basis of their unique molecular vibrations. In this work, we synthesized star-shaped silver nanostructures and fabricated SERS substrates to use the SERS enhancement of the Raman signal to detect neonicotinoid pesticides. These silver nanostar substrates were prepared by assembling the nanostar particles on a glass substrate surface using a self-assembly technique with various layers of silver nanostars film. The silver nanostar distribution on the solid substrate surface was found to have good reproducibility, reusability and were a stable SERS substrate giving SERS enhancements for pesticide detection at concentrations as low as 10−6 mg/ml. The distribution of these silver nanostars on the surface allowed excellent reproducibility of the detection with a low relative standard derivation (RSD) of SERS intensity of 8%. This work potentially builds a platform for an ultrasensitive detector where samples can be probed with little to no pre-processing and a range of pollutants can be detected at very low levels.

Reconfigurable multiple beams forming method based on liquid crystal on silicon

With the purpose of meeting the increasing requirement of free-space optical networking, reconfigurable multiple beams are required from a single terminal. In this paper, we demonstrate the role of co-modulation of amplitude and phase on incident laser beam using such a liquid crystal spatial light modulator. It enables arbitrary beam number, arbitrary pointing angle, and power occupation with multiple beams of excellent performance on a relative error and standard derivation when using typical groups of examples. Both numerical simulations and experimental results are presented demonstrating reconfigurable multiple beams forming via liquid crystal on silicon.

A Practical Method for Estimating Mutual Inductance in Wireless Power Transmission System

This paper proposes a practical method for estimating mutual inductance in wireless power transmission system based on the principle of electromagnetic induction. Conventional estimation methods utilize a voltage, current, and phase of current in transmitter side, while our method requires only an amplitude of the voltage and current in transmitter side. Our method is designed so that the mutual inductance can be estimated under challenging situation which there is a measurement noise. Numerical simulations show that if the system has a small mutual inductance, a relative error and standard derivation of estimated mutual inductance tend to become larger. However, it will be shown that these factors can be improved to make a voltage of voltage source in the system high.

Disperse Solid-Phase Extraction Cleanup for the Determination of 1-Deoxynojirimycin in Mulberry Leaves with Ultraperformance Liquid Chromatography-Tandem Mass Spectrometry

A new determination method of 1-deoxynojirimycin (1-DNJ) in mulberry leaves based on ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) has been developed. Dried and crushed mulberry leaves’ sample was extracted by MeCN-water solvent, purified by graphitized carbon black (GCB) and primary secondary amine (PSA) to remove organic acids and pigments, and then analyzed after attenuation and filtration. The calibration curve showed linearity in the concentration range of 10–500 ng/mL, with the correlation coefficient of 0.998. Recoveries of spiked 1-DNJ at three fortification levels ranged from 94.6% to 96.4%, with relative standard derivation below 1.2%. Additionally, the matrix effect was assessed as negligible. Compared with methods by gas chromatography (GC) and liquid chromatography (LC) via real sample detection, the proposed method acquired better stability and detection efficiency. These results proved that this method has advantages of simple operation, complete purification, small pretreatment loss, good precision and accuracy, and high determination specificity, which is suitable for massive monitoring and precise quantitation of 1-DNJ in mulberry leaves.

LC-MS/MS-based non-isotopically paired labeling (NIPL) strategy for the qualification and quantification of monosaccharides

Investigation into monosaccharides is critical for studies of oligosaccharides structure and function in biological processes. However, monosaccharides quantification is still challenge due to their isomeric structure and high hydrophilic properties. Besides, it was difficult to obtain isotopic internal standards (IS) of each monosaccharide in complex matrixes. Herein, we developed a novel strategy for the qualification and quantification of monosaccharides in urine using two structure analogs 1-(4-methylphenyl)-3-methyl-5-pyrazolone (MPMP) and1-phenyl-3-methyl-5-pyrazolone (PMP) as non-isotopically paired labeling (NIPL) reagents by liquid chromatograph-tandem mass spectrometry (LC-MS/MS). The derivatized monosaccharides by NIPL method not only had sufficient retention time differences on reversed-phase column, but also exhibited predominant product ion pairs (m/z 189 &m/z 175) in the multiple reaction monitoring (MRM) mode. In this method, PMP labeled standards were adopted as one-to-one internal standards (ISs). 12 urinary monosaccharides were successfully determined and the linear ranges expanded five orders of magnitude with limit of quantification (LOQ) varied from 0.09 ng mL−1 to 0.36 ng mL−1 as well as the accuracy higher than 98.15% and the relative standard derivation (RSD) lower than 7.92%. With assistance of multivariate analysis, the targeted monosaccharide biomarkers were firstly obtained for the diagnosis of bladder cancer. By the inexpensive NIPL reagents—MPMP/PMP, the developed strategy possessed the specific advantages of low cost, simple operation, high sensitivity and high accuracy for the qualification and quantitation of monosaccharides. As expected, this method will provide an alternative application potential for targeted metabolomics analysis.

Fluorescent Probe for Ag+ Detection Using SYBR GREEN I and C-C Mismatch.

Among heavy metals silver ions (Ag+) severely impact water, the environment and have serious side effects on human health. This article proposes a facile and ultrasensitive fluorescent probe for the detection of Ag+ ions using SYBR Green I (SGI) and cytosine-rich (C-rich) silver-specific oligonucleotide (SSO). Maximum fluorescent intensities with the highest sensitivity were obtained using a 0.61 dye/SSO base ratio (DBR). The established sensing principle using the optimized parameters for bath temperature, SSO concentration, DBR, ionic strength, pH, reaction time, incubation duration and temperature effect achieved a sensitive limit of detection of 59.9 nM for silver ions (calculated through 3σ, n = 11) with a linear working range of 100–1000 nM and 0.997 R2. The total time for one assay is below 10 min; The relative standard derivation for ten repeated measurements is 8.6%. No blatant interferences were observed in the selectivity test when fluorescent probe is evaluated by investigating the effects of 11 common interference factors in the aqueous matrix. In extreme cases, three false-negative factors were observed, including calcium hardness, magnesium hardness, and hypochlorite. The recovery ratios were within the range of 79~110% for three types of diluted water.

Determination of hydroxy terminated polybutadiene in the blends by liquid critical condition chromatography

A method based on liquid critical condition chromatography (LCCC) was established for the quantification of hydroxy-terminated polybutadiene (HTPB) in polymer blends. The critical conditions for HTPB were investigated using a C18 column as the stationary phase, and tetrahydrofuran (THF)-acetonitrile (ACN) or THF-water as the mobile phase. Irrespective of the relative molecular mass, HTPB was eluted under the critical conditions of THF-ACN (70.7:29.3, v/v) or THF-water (92:8, v/v). Under the optimal conditions, the HTPB exhibited satisfactory linearity in the range of 46.7-216.4 mg/L, with a correlation coefficient (r) of 0.997. The limit of detection reached 4.2 mg/L. The recoveries of HTPB from the prepared mixtures of HTPB and mineral oil ranged from 89.2% to 101.1%, with a relative standard derivation of less than 0.66% (n=6). This method was successfully applied to the quantitative analysis of HTPB in a commercial polyurethane adhesive, and 26.6% of HTPB was detected in the product. This LCCC method is simple, convenient, highly selective, and reliable for quality control and failure studies of formulated products.

A novel pH sensor with application to milk based on electrochemical oxidative quinone-functionalization of tryptophan residues

The electrochemical oxidative quinone-functionalization of tryptophan (Trp) residues, and the proton-coupled electron transfer properties between quinonized Trp (Trp=O) and its re-reduced species (Trp-OH) are investigated for potentiometric pH sensors. The Trp=O/Trp-OH couples are assembled on a graphite electrode using multiple cyclic voltammetry, and exhibit a pair of well-defined redox peaks at redox potential of 0.090 V (vs. SCE) at pH 7.0 and 298 K. The proton-coupled electron transfer properties of Trp=O/Trp-OH couples are dependent on electrode substrate material, incubation temperature and pH values, and Trp residue sources including amino acid, peptide and protein. The Trp=O/Trp-OH-based surface-confined exothermic electrode reaction rates show a decrease with increasing incubation temperature from 283 to 323 K at pH 5.0. Both of redox peak potential and open-circuit potential under optimum conditions have a good linear pH dependence between 1.0 and 12.0 with sensitivity of more than 52 mV pH −1 and relative standard derivation of 1.5%. The proposed potentiometric pH sensor has significant advantages of low cost, good stability and reproducibility, and strong anti-interference ability. The present study shows a new approach to endow Trp, Trp-containing peptides and non-conjugated proteins with analogous proton-coupled electron transfer performance to prosthetic groups of quinoproteins for monitoring pH changes in milk samples.

Development of a nanobody tagged with streptavidin-binding peptide and its application in a Luminex fluoroimmunoassay for alpha fetal protein in serum.

Sensitive and accurate detection of disease-related biomarkers can promote the early screening and diagnosis of cancers for improving the prognosis and survival of patients. Herein alpha fetal protein (AFP) was selected as the model macromolecule antigen and we developed AFP-specific alpaca nanobodies (Nbs) from an immunized phage-displayed Nb library. Then Nbs tagged with streptavidin-binding peptide (Nb-SBP) were constructed and used to develop an Nb-SBP-mediated fluoroimmunoassay based on the Luminex-200 system (NS-LFIA). Based on the optimal experimental conditions, the NS-LFIA has a limit of detection of 0.237 ng mL−1 with a linear detection range of 0.49–125 ng mL−1. The average recovery rate and relative standard derivation were in the range of 98.2–110% and 2.8–13.8%, respectively. The NS-LFIA is highly selective for AFP and ignorable cross-reaction was observed with the other biomarkers. The content of AFP in clinical serum samples was determined by both the developed NS-LFIA and the Roche E601 automatic chemiluminescence immunoassay analyzer and a good correlation was obtained between the two methods (R2 = 0.9894). Moreover, the Nb-SBP can significantly improve the homogeneity of the fluorescent signals tested by the Luminex-200 system compared with the biotinylated conventional monoclonal antibodies, which could reduce the magnetic microsphere consumption and test cost by decreasing the repetitions of each sample. Thus the results demonstrated that the Nb-SBP was a very promising immunological diagnostic reagent and indicated the applicability and reliability of the NS-LFIA for sensitive detection of AFP and other disease-related biomarkers.

Aperture scalable liquid crystal optically duplicated array of phased array

To achieve non-mechanical laser beam steering in the scenario of long distance propagation such as free-space laser communication between satellites, large aperture size is an inevitable issue to be considered to narrow the divergence angle of the output beam. Liquid crystal optical phased array, to be one of the solutions of non-mechanical beam steering, has already shown its obvious potential to achieve a relative large aperture on the order of centimeter. To achieve even larger, its driving matrix becomes squared larger. In this paper, we proposed a novel architecture to realize an optical phased array with a scalable aperture. Meanwhile the driving matrix is almost not increased. It provides the feature of a cascade system with a device of spatial phased modulation and an array of duplicating units. Each unit of the duplicating array is consist of a polarization beam splitter and a half wave plate to have the same output optical field distribution as the input beam whose phase front is modulated by a small size spatial modulator. Not only the property of beam deflection is numerically simulated and experimentally verified, but also the property of divergence angle compression and grating lobes limitation are evaluated. Meanwhile, due to the high precision of the experimental alignment, the non-mechanical beam deflection property is still maintained no matter how many the duplicated unit number is. The relative standard derivation steering error is 0.025.

Dual-recognition surface-enhanced Raman scattering(SERS)biosensor for pathogenic bacteria detection by using vancomycin-SERS tags and aptamer-Fe3O4@Au

Rapid and reliable detection of pathogenic bacteria is vital to prevent and control bacterial diseases. In this study, we present a magnetically assisted surface-enhanced Raman scattering (SERS) biosensor based on the dual-recognition of bacterial cell by aptamer and antibiotic molecules. Aptamer-Fe3O4@Au magnetic nanoparticles (AuMNPs) were synthesized as magnetic and SERS activated substrate for specific bacteria enrichment, vancomycin-SERS tags (Au@MBA) were prepared for the sensitive quantification of pathogenic bacteria. Due to the Au-shell based dual-SERS enhancement and aptamer/vancomycin based dual-recognition ability, a detection limit of 3 cells/mL with a wide dynamic linear range from 10 to 107 cells/mL can be achieved within 50 min without other non-target bacteria interference. When applied in real samples, the approach shows recoveries from 95.0% to 106.4% with relative standard derivation (RSD) less than 5.3%. The SERS strategy could be used to detect a broad range of bacteria by using different aptamers, moreover, the simple operation and precise quantification ability empower this assay great potential in the application of food safety and infectious disease point-of-care diagnosis.

Point-of-Care Testing of Pathogenic Bacteria at the Single-Colony Level via Gas Pressure Readout Using Aptamer-Coated Magnetic CuFe2O4 and Vancomycin-Capped Platinum Nanoparticles.

Pressure measurements are performed everyday with simple devices, and in the field of analytical chemistry the pressure-based signaling strategy offers two important advantages, signal amplification and particular applicability in point-of-care settings. Herein, by using vancomycin (Van)-functionalized platinum nanoparticles (PtNPs@Van) and aptamer-coated magnetic CuFe2O4 nanoprobes dual-recognition units integrated with a catalyzed breakdown of H2O2 for O2 generation, we demonstrated that gas pressure can be used as a readout means for highly sensitive pathogenic bacteria identification and quantification. Using Staphylococcus aureus ( S. aureus) as a test case, integration of the molecular dual-recognition component with the catalyzed gas-generation reaction leads to a significant pressure change (Δ P), and the correlation between the concentration of S. aureus and the Δ P signal was found to be linear from 5.0 to 1.0 × 104 cfu/mL with a detection limit of 1.0 cfu/mL. Other nontarget bacteria show negative results, verifying the high specificity of the present strategy. When employed to assay S. aureus in saliva and milk samples, the approach shows recoveries from 93.3% to 107.1% with relative standard derivation (RSD) less than 8.8%. By the integration of catalyzed gas-generation reaction with the designed molecular recognition event, obviously the pressure-based signaling strategy could facilitate pathogenic bacteria identification and quantification not only in the laboratory but also in point-of-care settings, which could have great potential in the application of food safety and infectious disease diagnosis.