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We herein report the design of a novel semiconducting silicon nanowire field-effect transistor (SiNW-FET) biosensor array for ultrasensitive label-free and real-time detection of nucleic acids. Highly responsive SiNWs with narrow sizes and high surface-to-volume-ratios were "top-down" fabricated with a complementary metal oxide semiconductor compatible anisotropic self-stop etching technique. When SiNWs were covalently modified with DNA probes, the nanosensor showed highly sensitive concentration-dependent conductance change in response to specific target DNA sequences. This SiNW-FET nanosensor revealed ultrahigh sensitivity for rapid and reliable detection of 1 fM of target DNA and high specificity single-nucleotide polymorphism discrimination. As a proof-of-concept for multiplex detection with this small-size and mass producible sensor array, we demonstrated simultaneous selective detection of two pathogenic strain virus DNA sequences (H1N1 and H5N1) of avian influenza.

Silicon nanowire (SiNW) field effect transistors (FETs) have emerged as powerful sensors for ultrasensitive, direct electrical readout, and label-free biological/chemical detection. The sensing mechanism of SiNW-FET can be understood in terms of the change in charge density at the SiNW surface after hybridization. So far, there have been limited systematic studies on fundamental factors related to device sensitivity to further make clear the overall effect on sensing sensitivity. Here, we present an analytical result for our triangle cross-section wire for predicting the sensitivity of nanowire surface-charge sensors. It was confirmed through sensing experiments that the back-gated SiNW-FET sensor had the highest percentage current response in the subthreshold regime and the sensor performance could be optimized in low buffer ionic strength and at moderate probe concentration. The optimized SiNW-FET nanosensor revealed ultrahigh sensitivity for rapid and reliable detection of target DNA with a detection limit of 0.1 fM and high specificity for single-nucleotide polymorphism discrimination. In our work, enhanced sensing of biological species by optimization of operating parameters and fundamental understanding for SiNW FET detection limit was obtained.

MicroRNAs (miRNAs) have been identified as promising cancer biomarkers due to their stable presence in serum. As an alternative to PCR-based homogenous assays, surface-based electrochemical biosensors offer great opportunities for low-cost, point-of-care tests (POCTs) of disease-associated miRNAs. Nevertheless, the sensitivity of miRNA sensors is often limited by mass transport and crowding effects at the water-electrode interface. To address such challenges, we herein report a DNA nanostructure-based interfacial engineering approach to enhance binding recognition at the gold electrode surface and drastically improve the detection sensitivity. By employing this novel strategy, we can directly detect as few as attomolar (<1, 000 copies) miRNAs with high single-base discrimination ability. Given that this ultrasensitive electrochemical miRNA sensor (EMRS) is highly reproducible and essentially free of prior target labeling and PCR amplification, we also demonstrate its application by analyzing miRNA expression levels in clinical samples from esophageal squamous cell carcinoma (ESCC) patients.

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Three-dimensional (3D) DNA nanostructures have shown great promise for various applications including molecular sensing and therapeutics. Here we report kinetic studies of DNA-mediated charge transport (CT) within a 3D DNA nanostructure framework. A tetrahedral DNA nanostructure was used to investigate the through-duplex and through-space CT of small redox molecules (methylene blue (MB) and ferrocene (Fc)) that were bound to specific positions above the surface of the gold electrode. CT rate measurements provide unambiguous evidence that the intercalative MB probe undergoes efficient mediated CT over longer distances along the duplex, whereas the nonintercalative Fc probe tunnels electrons through the space. This study sheds new light on DNA-based molecular electronics and on designing high-performance biosensor devices.

Vitrimers are expected to combine features of thermosets and thermoplastics but their continuous reprocessing is still a challenge; poly­(ethylene terephthalate) (PET) has been widely used in our daily life, while its cross-linking upcycle contradicts with processability. Herein, we combined polyol with a tertiary amine structure and diepoxy to transform PET to continuously reprocessable vitrimers through an industrial twin-screw extruder. The cross-linking of PET was determined by swelling and rheology experiments, and the vitrimer feature was characterized by stress relaxation and oscillatory frequency sweep experiments. Creep resistance and mechanical properties of PET vitrimers were improved greatly relative to neat PET. Meanwhile, PET vitrimers exhibited excellent reprocessability via compression, extrusion, and injection molding suitable for industrial production. According to this work, any thermoplastics containing ester bonds should be able to be upgraded to vitrimers for additional advantages such as creep resistance, dimensional stability, insolubility, etc., without sacrificing the original processability.

Herein, we have developed a simple and facile method to synthesize yolk-shell nanostructured FeO@C nanoparticles (NPs) as a multifunctional biosensing platform for the label-free colorimetric detection of HO and glucose. It was demonstrated that FeO@C yolk-shell nanostructures (YSNs) retained the magnetic properties that can be used for separation and concentration. Also importantly, the FeO@C YSNs exhibited an intrinsic peroxidase-like activity that could quickly catalyze the enzyme substrate in the presence of HO and produce a blue color. Compared to other similar ferric oxide-based NPs with different structures, FeO@C YSNs exhibited greatly enhanced catalytic activities due to their unique structural features. Moreover, steady-state kinetics indicated the catalytic behaviors in agreement with the classic Michaelis-Menten models. Taking advantage of the high catalytic activity, FeO@C YSNs were employed as novel peroxidase mimetics for label-free, rapid, sensitive, and specific colorimetric sensing of HO and glucose, suggesting that FeO@C YSNs have the potential for construction of portable sensors in the application of point-of-care (POC) diagnosis and on-site tests.