With the assistance of peptides, a stable and highly efficient approach for the quick loading of thiol–DNA onto AuNPs is proposed with a high DNA utilization, which is generally applicable to specific DNA detection and diverse AuNP sizes. The maximum efficiency of hybridization reached 93% while the reaction time was shortened to 30 min.

•Au@Ag core–shell nanoparticles with well-dispersed and high SERS efficiency.•A novel As (III) detection method with excellent selectivity and sensitivity.•This biosensor was demonstrated in practical samples with satisfactory results.In this work, we propose for the first time a simple and novel approach based on SERS and As (III) -aptamer for detection of As (III) with excellent selectivity and sensitivity. To maintain the wonderful SERS substrate, Au@Ag shell–core nanoparticle has been successfully synthesized by seeds growth method. As-prepared Au@Ag not only has well-dispersed but also obtains high SERS efficiency. The novel As (III) biosensor has an excellent linear correlation with the concentration of As (III) ranging from 0.5 to 10 ppb. The detection limit of this assay for As (III) is 0.1 ppb (3 times standard deviation rules) which is lower than the maximum limitation guided by the United States Environmental Protection Agency (EPA) and the World Health Organization (WHO). Importantly, the results were demonstrated that no other ions interfered with the detection of As (III) in water. Further, this As (III) biosensor was demonstrated in monitoring As (III) in lake water samples with satisfactory results.Above scheme shows the illustration of fabrication of the assay for As (III). 4-MBA was modified onto Au@Ag via Au-S bonds. 4-MBA served as a Raman reporter molecule that provided simple and narrow characteristic peak. In this complex system, on the one hand, As (III) aptamer was effectively absorbed on Au@Ag by means of coordination interaction between N atom of base and Au@Ag. On the other hand, As (III) could specifically bind to As (III) aptamer to form As (III)-aptamer complex. In other words, As (III) competed with Raman labeled Au@Ag for binding to As (III) aptamer. As (III) added into homogeneous Raman labeled Au@Ag could specifically bind to As (III) aptamer, making the aptamer displace from the surface of Au@Ag and ultimately leading to aggregation of Au@Ag. As a consequence, the signal intensity of Raman reporter molecule 4-MBA was significantly intensified due to the formation of SERS “hot spots”.

A new fluorescence sensor is developed for simultaneous detection of Hg2+ and Ag+. During the detection process, Hg2+ forms complexes with the fluorescent dye rhodamine B isothiocyanate (RBITC) modified onto the surface of gold nanoparticles(AuNPs), resulting in RBITC’s displacement from the surface of AuNPs and the recovery of fluorescence. Meanwhile, Ag+ forms “C-Ag+-C” complex with C-rich 5-carboxyfluorescein (FAM)-ssDNA modified onto the surface of AuNPs, which keeps the fluorescent dye FAM close to the AuNPs and results in quench of fluorescence. The experimental results show a wide linear range and a good sensitivity. The limit of detection is 1.06 nmol/L for Ag+ and 0.48 nmol/L for Hg2+. This detection method is not only easy to operate but also efficient.

For the first time, gold nanoclusters were found to exhibit high fluorescence enhancement ability based on the metal-enhanced fluorescence (MEF) effect, which can effectively enhance the fluorescence of fluorescein isothiocyanate (FITC). By means of this phenomenon, Au nanoclusters have been successfully used in the construction of a fluorescence-enhanced sensing platform for the detection of protooncogene.

•This label-free assay avoids modification, offers cost efficiency.•No separation procedure is needed for the sensing.•The sensor responses rapidly, and takes 20 min to complete the Cys-sensing.•This “turn-on” sensor shows high sensitivity and selectivity.A Hg2+-mediated fluorescence turn-on sensor for cysteine (Cys) detection was developed using the nucleic acid minor groove binding dye DAPI. In this work, two fully complementary DNA sequences, a T-rich single-stranded molecule (ssDNA) and an A-rich single-stranded molecule, were employed to constitute consecutive “AT/TA” base pairs, which could strongly enhance the fluorescence of DAPI. In the absence of cysteine, Hg2+ reacted with T-rich single-stranded DNA and “T–Hg2+–T” base pairs formed, this seriously disrupted consecutive AT base pairs. As a result, the fluorescence of DAPI was not increased efficiently. However, considering that cysteine binds strongly to Hg2+, the structure of the “T–Hg2+–T” complexes was destroyed in the presence of cysteine, resulting in the re-formation of consecutive AT base pairs and increased DAPI fluorescence. Obviously, the amount of cysteine could be easily measured based on the enhancement of DAPI fluorescence, and it took only 20 min to complete the whole cysteine-sensing process. Therefore, a label-free fluorescent “turn-on” sensor for the rapid detection of cysteine was designed, and the detection limit of this sensor was as low as 2.4 nM, which was much lower than those of the most of the previously reported cysteine sensors.In the absence of Cys, Hg2+ bound to thymine and formed “T–Hg2+–T”, so that AT base pairs between S1 and S2 were seriously disrupted and the fluorescence of DAPI was effectively suppressed. However, the presence of Cys completely changed the situation: Cys removed Hg2+ far away from the structure of “T–Hg2+–T” with its active sulfhydryl group, then AT base pairs appeared and the fluorescence of DAPI was successfully enhanced. Therefore, the amount of Cys could be easily measured according to the fluorescence enhancement of DAPI.

•“Turn-on” SERS-based enzymatic assay is newly proposed.•The method works on catalytic property of trypsin to cleave peptides.•Ultrasensitive detection of target was achieved together with potential as a SERS-based label-free approach.•We proved the universality of the method as a general approach for proteases.We describe herein a novel' “turn-on” SERS-based strategy for protease detection based on surface enhanced Raman scattering (SERS) and the mediation of spacing between 4-mercaptobenzoic acid (4-MBA) labeled gold nanoparticles (AuNPs) through enzyme assays. The method employed non-cross-linking aggregation of 4-MBA-modified AuNPs by peptides after treatment with target protease. Thus, SERS signals of 4-MBA are sharply increased because of the decreased electrostatic stability of AuNPs that initiated gold nanoaggregates incorporating Raman reporter molecules due to the formation of “Hot Spots”. Through this strategy, a novel and facile “turn-on” SERS biosensor for trypsin and thrombin based on enzymatic cleavage activity is established with sensitivity, selectivity and simplicity as AuNPs and peptides are easily accessible. Compared with other methods, this newly proposed method has improved sensitivity. The limit of detection was 85 fM (at the ratio of signal to noise, S/N=3:1) for trypsin. Controlled experiments showed that the method exhibited good selectivity over other proteases. We also proved that this principle could be easily adapted to detection of other proteases such as thrombin. The method demonstrated the capability for application in complex matrix samples. The results also presented the potential and superiority of SERS biosensor as a general approach for proteases based on enzyme activity.

•A novel Ag+ probe with excellent robustness, selectivity and sensitivity was successfully developed.•Good water-solubility and high fluorescence quenching efficiency single MoS2 is used for the first time for Ag+ detection.•This Ag+ probe was demonstrated in monitoring Ag+ in practical samples with satisfactory results.•The Ag+ detection method is low-cost and simple.In this work, we use for the first time single layer MoS2 as the fluorescence quencher to design a detection method for Ag+ with excellent robustness, selectivity and sensitivity. To maintain the ultrathin MoS2, bulk MoS2 materials have been exfoliated by intercalation with lithium followed by reaction with water. As-prepared two-dimensional MoS2 not only has good water-solubility but also obtains high fluorescence quenching efficiency within 5 min. Importantly, the detection limit of this assay for Ag+ (1 nM) was lower than the maximum limitation guided by the United States Environmental Protection Agency (EPA) and the World Health Organization (WHO). Further, this new Ag+ probe was demonstrated in monitoring Ag+ in lake water samples with satisfactory results.Above scheme shows the illustration of fabrication of the assay for Ag+ on single layer MoS2. A fluorescein isothiocyanate (FITC)-labeled Ag+ specific oligonucleotide, rich in cytosine, was employed as the fluorescent probe in sensing targets. The conformation of the probe changed from random coil ssDNA to straight stiff dsDNA with “C–Ag+–C” base pairs followed by the addition of Ag+. When FITC-labeled DNA probe was in the state of random coil ssDNA, FRET from FITC-ssDNA to single layer MoS2 occurred because the distance from the energy donor FITC to the energy acceptor single layer MoS2 was shortened by the special p-type nature of ultrathin MoS2 material and Van der Waals forces between nucleotide bases and single layer MoS2. But when the DNA probe was in formation of dsDNA, the energy donor FITC was far away from the surface of single layer MoS2 and FRET disappeared. So, the introduction of enough amounts of Ag+ led to a large degree of fluorescence recovery, and the degree of fluorescence quenching was closely related to the amount of added Ag+ in certain linear range.

A simple, toehold-mediated two-way input DNA machine has been developed. Utilizing symmetric and asymmetric protector sequences, INH, XOR logic gates and a half-subtractor are designed based on this two-way structure.

In this contribution, we report a new type of Au nanoflower-based nitroaromatic pesticide degradation platform that is fast, efficient, and simple. We found a straightforward, economically viable, and “green” approach for the synthesis and stabilization of relatively monodisperse Au nanoflowers by using nontoxic chemical of hydroxylamine (NH2OH) without stabilizer and the adjustment of the pH environment. This experiment shows that these Au nanoflowers function as effective catalyst for the reduction of pendimethalin in the presence of NaBH4 (otherwise unfeasible if NaBH4 is the only agent employed), which was reflected by the UV/vis spectra of the catalytic reaction kinetics. Importantly, the novel degradation platform could be put in use in two different practical soil samples with satisfactory results under laboratory conditions. To demonstrate the feasibility and universality of our design, two other nitroaromatic pesticides, trifluralin, and p-nitrophenol, were selected and were successfully degraded using this degradation platform.

In this essay, three novel nonlinear optical (NLO) azo-materials containing indole and sulfonyl based chromophores were studied in-depth by using Fourier transform (FT) IR, FT-Raman spectra and density functional theory (DFT). The scaled theoretical results were shown to be in good agreement with the experimental data. In addition, the computed 1H nuclear magnetic resonance (NMR) and UV–vis absorption wavelengths were also discussed compared with experimental data. The large β values calculated by the DFT methods showed that the studied molecules were good NLO materials, and the molecule which owned a larger substituent group on the indole chromophore moieties had a larger value. Furthermore, simultaneous infrared and Raman activity suggested that intramolecular charges might transfer through the conjugated framework from the electronic donor group to electronic acceptor group. The HOMO–LUMO gap analysis and molecular electrostatic potential (MEP) maps also supported this viewpoint.Graphical abstractThe simultaneous strong Raman and infrared activity of some vibrations suggests that the charge transfer through the conjugated framework from the donor to acceptor group and the HOMO–LUMO analysis gives the supported information.Highlights► FT-IR, FT-Raman, 1H NMR and UV spectra of three novel NLO materials. ► The relationship between structure, β value and NLO properties is discussed. ► The donor and acceptor groups are discussed by vibrational analysis.

A selective and sensitive fluorescence biosensor for Ag+ ions and cysteine (Cys) was developed based on the chelation actions between Ag+ ions and guanine bases of G-rich fluorogenic oligonucleotide (FAM-ssDNA) and the different electrostatic affinity between FAM-ssDNA and graphene oxide (GO). FAM-ssDNA adsorbed onto the surface of GO through π–π stacking interaction between the ring structure in the nucleobases and the hexagonal cells of GO, and the fluorescence of the dye was quenched. In the presence of Ag+ ions, the random coil structure changed into a G-Ag+ architecture. As a result, the binding released FAM-ssDNA signal probe from the surface of GO, which disrupted the energy transfer from FAM-ssDNA to GO, recovering the fluorescence emission of FAM-ssDNA. On the other hand, because Cys was a strong Ag+ ions binder, it could deactivate the sensor fluorescence by rewrapping FAM-ssDNA around GO. In this way, these changes in fluorescence intensity allowed the selective detection of Ag+ ions and Cys.Highlights► The positive effect of Ag+ on fluorescence of FAM-ssDNA was first proposed. ► A turn-on fluorometric assay for Ag+ and turn-off assay for cysteine were designed. ► The more G units of ssDNA, the stronger enhancement of fluorescence.

•This novel strategy is based on ligand-responsive G-quadruplex formation.•The assay is label free for rapid DNA detection.•This probe is simple and cost-efficiency in design and operation.A facile and label-free assay with label-free molecular beacons (MBs) and fluorescent dye N-methyl mesoporphyrin IX (NMM) was developed for the detection of specific single-stranded DNA sequences. It was demonstrated by a reverse transcription oligonucleotide sequence (target DNA, 20 bases) of RNA fragment of human immunodeficiency virus (HIV) as model systems. In the absence of target DNA, the MBs were in the stem-closed form, the G-quadruplex structure could not form and the fluorescence signal of NMM was very low. In the presence of target DNA the MBs turned “Off” to “On”, thus promoting the formation of G-quadruplex which could greatly enhance the fluorescence of NMM. This biosensor was simple in design, fast in operation, and more convenient and promising than other methods. It took less than 30 min to finish and its detection limit was 1.4 nM. No sophisticated experimental techniques or chemical modification for DNA sequences were required. This new approach could be widely applied to sensitive and selective nucleic acids detection.

A recent study reported by Higuchi's group has shown that Pt–DNA complexes possess peroxidase enzymatic activity similar to natural peroxidases. In this study, we prepared Pt–DNA complexes and demonstrated their use in catalyzing the oxidation of a peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 to the oxidized product which provided a colorimetric detection of H2O2. As low as 3.92 × 10−4 mol L−1 H2O2 could be detected with a linear range from 9.79 × 10−4 to 1.76 × 10−2 mol L−1via our method. Furthermore, PVDF membranes were employed to increase sensitivity and decrease the detection limit of H2O2, enabling a two-fold improvement in the detection sensitivity as compared with the above counterparts. More importantly, a sensitive and selective method for glucose detection was developed using glucose oxidase (GOx) and the as-prepared Pt–DNA complexes. We realized the test of glucose as low as 10−7 mol L−1 by the color change, which was comparable to or even better than the existing methods, and identified the concentration of glucose in Sprite with the naked eye without referring to any sophisticated apparatus. The detection platforms for H2O2 and glucose developed in the present work showed great potential for applications in the future.

A bi-detection system integrated by laser-induced fluorescence (LIF) and retro-reflected beam interference (RBI) based refractive index was established and applied to simultaneously determine erythrosine and sucrose in candy floss. The system realized separation-free analysis of candy floss without prior concentration steps.

Novel functional oligonucleotides, especially DNAzymes with RNA-cleavage activity, evoke current research interest increasingly due to their potential applications in therapeutics and sensors. One of the most attention-attracting is the lead-specific DNAzyme, which is composed of an enzyme strand 17E and a substrate strand 17S, addition of Pb2+ enables the DNAzyme to cleave its substrate. In this study, we took advantage of the unique optical properties of a water-soluble cationic polythiophene (PT) and designed a fluorometric sensing assay for the detection of Pb2+. A simple “mix-and-detect” approach enabled the detection of Pb2+ within 20 minutes due to the distinguishable optical properties of PT–dsDNA and PT–ssDNA. As low as 10 nM Pb2+ could be detected with a detection range from 10 nM to 100 μM via this method. Furthermore, this method was highly selective and only minimally perturbed by nonspecific metal ions. Since common steps such as modification and separation could be successfully avoided, this simple, sensitive, specific, and cost-effective approach showed great potential applications in environmental monitoring, waste management and clinical toxicology.

In this work, a new platform for effective sensing cysteine (Cys) was developed based on fluorescence resonance energy transfer (FRET) between FAM-tagged single-stranded DNA (FAM-ssDNA) and graphene oxide (GO). Due to the noncovalent assembly between FAM-ssDNA and GO, fluorescence quenching of the FAM took place because of FRET. This method relied on the competitive ligation of Ag+ by Cys and “cytosine–cytosine” (C–C) mismatches in a FAM-labeled DNA strand of the self-hybridizing strand. At first, enough amount of Ag+ was introduced to bind “C–C” mismatches and form double-stranded DNA (dsDNA), which had weak affinity to GO and kept FAM away from GO surface. However, the presence of Cys removed Ag+ away from “cytosine–Ag+–cytosine” (C–Ag+–C) base pairs, leading to the formation of ssDNA again and FRET, and then fluorescence of the FAM-ssDNA was efficiently quenched. The fluorescence intensity decrease was found to be proportional to the increase of concentration of Cys in both aqueous buffer (2–200 nM) and human serum (5–200 nM), and the sensitivity of the proposed method towards Cys was much higher than that of other reported assays for Cys.Highlights► A new platform for fluorescent detecting cysteine was designed. ► FRET between FAM-ssDNA and GO was researched to construct the method. ► Detection of cysteine has been effectively realized in buffer and serum.

A simultaneous laser-induced fluorescence (LIF), coaxial thermal lens spectroscopy (TLS) and retro-reflected beam interference (RBI) detection for capillary electrophoresis (CE), has been described. In its optical scheme, a diode-pump solid-state (DPSS) laser was employed as the pump laser in both LIF detection and coaxial TLS detection, and a He–Ne laser was utilized as the probe laser in coaxial TLS detection and RBI detection. In addition, RBI signals with and without thermal lens had been theoretically compared to ensure the reliability of the RBI signal. Moreover, the focus length of the key lens has been optimized to improve the performance of the proposed detection. The last but not least, several determinations were taken to evaluate its limit of detection, linear range as well as relative standard deviation, all of which indicate no worse results compared with former reports. LIF and coaxial TLS detection owned high sensitivity, and RBI detection indicated versatile property, based on which the reported detection achieved a sensitive and universal detection for CE.Highlights► We realize concurrent fluorescence, thermal lens and interference detection for CE. ► Beam interference signals were theoretically calculated to ensure its reliability. ► The lens focus in the detection scheme has been optimized. ► The reported strategy achieved a sensitive and universal detection for CE.

A novel method for simultaneous determination of sucrose and sunset yellow in retail soft drink without separation by combination of retro-reflected beam interference-based refractive index (RBI) and thermal lens (TL) detections was developed. The method proposed here successfully realized individual measurements of sucrose and sunset yellow in one single sample, while their concentrations were thousands of times different in the sample. Under optimized conditions, a separation-free process was carried out so that sucrose and sunset yellow were quantified at the same time. Limits of detection (LODs) of sucrose and sunset yellow were 0. 21 mg ml−1 and 0.23 μg ml−1 and the relative standard deviation (RSDs) were 3.9% and 3.07%. The developed method was successfully applied for the simultaneous analysis of sucrose and sunset yellow in retail soft drink. The soft drink containing 123.6 ± 2.6 mg ml−1 sucrose and 46.6 ± 1.8 μg ml−1 sunset yellow have been simultaneously measured without any separation procedure.

We have synthesized a stable, sensitive and specific surface-enhanced Raman tag, and demonstrated its application in human α-thrombin detection. The tag consists of aptamer-modified core–shell nanoparticles with hydrophobic Au@Ag as core and silica as shell encapsulating Raman active molecules. By taking advantage of the Raman signal enhancement effect by metallic nanostructures, high stability and robustness of glass-coated core–shell nanostructures and the recognition capabilities of aptamers, we designed a sandwich detection for protein identification with high selectivity and sensitivity. In this way, we realized the ultrasensitive detection of α-thrombin. GDNs (glass-coated, dye-tagged nanoparticles), which were conjugated with oligonucleotides or antibodies, were extremely soluble in water, and had mechanical and chemical stability, easily controllable-size distribution and friendly biocompatibility. Specifically, the glass coating renders the particles amenable to use in many solvents without altering the Raman spectral response and makes agglomeration a nonfactor. All these merits open the door of the real applications in diagnostics or medical investigations in complex biofluids, such as human plasma and serum. Using the aptamer-modified GDNs as Raman tags, we successfully performed the detection of α-thrombin in human plasma. Furthermore, the overall method have been proved effective and selective, and may be implemented for multiplex target analysis simultaneously.

A novel optical scheme, which accomplished simultaneous coaxial thermal lens spectroscopy and retro-reflected beam interference detection for capillary electrophoresis, has been described. By a special design, an adjustable pump laser waist relative to the probe laser waist was implemented, while some key elements for both detection modes were optimized. In either detection modes, certain preponderance compared with former reports was indicated. With both coaxial thermal lens spectroscopy and retro-reflected beam interference detection, the reported detection scheme combined high sensitivity and universal property for capillary electrophoresis detection.

Self-assembled monolayers (SAMs) have been widely used in studying interfacial phenomena, biological processes, electrochemistry, photoelectrochemistry, photoactivity and molecular interaction. Much research has been carried out in fabricating and removing SAMs on different substrates. In this work, we report for the first time, to our knowledge, that SAMs of thiolates on gold can be removed by immersing SAMs in 0.5 M NaBH4 solution for 10 min. The procedure of removing thiolates was very convenient. Cyclic voltammetry, surface-enhanced Raman spectroscopy, and X-ray photoelectron spectroscopy were used to characterize this process. The results indicated that the SAMs of thiolates on gold can be removed efficiently by NaBH4.

•A QCM and SERS combination setup was designed to monitor the thrombin aptamer binding kinetics.•A sandwich-structural sensing interface was assembled, and the process was monitored by QCM.•The sensing interface enables QCM response and SERS signals for low concentration thrombin.We reported quartz crystal microbalance (QCM) and surface enhancement Raman spectroscopy (SERS) combination to detect thrombin for the first time. 1,6-hexanedithiol (HDT) monolayer was assembled on the Au electrode of crystal ship and 20 nm Au NPs were assembled on this layer with stable Au-S linkage to form a two-dimensional nanoarray interface. Aptamers modified by thiol groups were assembled on this interface for capturing thrombin in succession. In the QCM detection process, the introduction of 40 nm aptamer-functionalized Au NPs amplify the frequency signal significantly. The thrombin detection limit reduced from 1 μM to 0.1 μM, and a good linear correlation was obtained between the change of frequency and the concentration of the thrombin in a range of 0.1 to 1.0 μM. Meanwhile, with the modification of Raman reporter 4-mercaptobenzoic acid onto the surface of 40 nm Au NPs, SERS signals of thrombin were obtained simultaneously. This assay also exhibited excellent selectivity both in QCM and SERS detection of thrombin.

•Ag+-triggered aggregation of peptide-AuNPs is newly proposed.•The principle depends on the behavior of Ag+-induced folding structure of peptides.•Ultrasensitive detection of silver ions with potential as practical application in complex water samples.•We present a simple, rapid, original method with excellent selectivity.In this article, we for the first time present an original and ultrasensitive assay to detect Ag+ ions, with which the aggregation of the given peptide-modified gold nanoparticles (peptide-AuNPs) can be triggered by the interaction between peptides and Ag+. The approach has rarely been used in the colorimetric determination of Ag+, because the mechanism of the above-mentioned interaction has not been studied through. In our assay, the principle of this interaction was investigated. Moreover, we applied it in the design of an extremely sensitive sensor for Ag+ detection with great selectivity. It is the Ag+-induced folding structure of the peptides that leads to the aggregation of peptide-AuNPs. The aggregation involves the formation of 4-coordinated complexes between Ag+ and peptides via bonding with the carbonyl oxygen and the nitrogen of the α-amino group in the peptides. The result shows that Ag+ ions can be selectively detected as low as 7.4 nM with a linear range of 10–1000 nM. Compared with other approaches, the proposed approach demonstrates superior simplicity, sensitivity, stability and time-saving. Furthermore, the biosensor excels in the practical application in water samples (e.g., lake, tap and drinking water) owing to its non-interference and on-site rapid determination.

Novel functional oligonucleotides, especially DNAzymes with RNA-cleavage activity, evoke current research interest increasingly due to their potential applications in therapeutics and sensors. One of the most attention-attracting is the lead-specific DNAzyme, which is composed of an enzyme strand 17E and a substrate strand 17S, addition of Pb2+ enables the DNAzyme to cleave its substrate. In this study, we took advantage of the unique optical properties of a water-soluble cationic polythiophene (PT) and designed a fluorometric sensing assay for the detection of Pb2+. A simple “mix-and-detect” approach enabled the detection of Pb2+ within 20 minutes due to the distinguishable optical properties of PT–dsDNA and PT–ssDNA. As low as 10 nM Pb2+ could be detected with a detection range from 10 nM to 100 μM via this method. Furthermore, this method was highly selective and only minimally perturbed by nonspecific metal ions. Since common steps such as modification and separation could be successfully avoided, this simple, sensitive, specific, and cost-effective approach showed great potential applications in environmental monitoring, waste management and clinical toxicology.

A bi-detection system integrated by laser-induced fluorescence (LIF) and retro-reflected beam interference (RBI) based refractive index was established and applied to simultaneously determine erythrosine and sucrose in candy floss. The system realized separation-free analysis of candy floss without prior concentration steps.

A simple, toehold-mediated two-way input DNA machine has been developed. Utilizing symmetric and asymmetric protector sequences, INH, XOR logic gates and a half-subtractor are designed based on this two-way structure.

A recent study reported by Higuchi's group has shown that Pt–DNA complexes possess peroxidase enzymatic activity similar to natural peroxidases. In this study, we prepared Pt–DNA complexes and demonstrated their use in catalyzing the oxidation of a peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 to the oxidized product which provided a colorimetric detection of H2O2. As low as 3.92 × 10−4 mol L−1 H2O2 could be detected with a linear range from 9.79 × 10−4 to 1.76 × 10−2 mol L−1via our method. Furthermore, PVDF membranes were employed to increase sensitivity and decrease the detection limit of H2O2, enabling a two-fold improvement in the detection sensitivity as compared with the above counterparts. More importantly, a sensitive and selective method for glucose detection was developed using glucose oxidase (GOx) and the as-prepared Pt–DNA complexes. We realized the test of glucose as low as 10−7 mol L−1 by the color change, which was comparable to or even better than the existing methods, and identified the concentration of glucose in Sprite with the naked eye without referring to any sophisticated apparatus. The detection platforms for H2O2 and glucose developed in the present work showed great potential for applications in the future.