Ultrasensitive carbon nanotube-bridged MXene conductive network arrays for one-step homogeneous electrochemical immunosensing of tumor markers.

Developing non-passivating and fully integrated electrode arrays for point-of-care testing of carcinoembryonic antigen (CEA) is crucial, as the serum level of CEA is closely associated with colorectal cancer. Herein, we propose a simple, low-cost, and eco-friendly template-assisted filtration method for the scalable preparation of carbon nanotube-bridged Ti3C2Tx MXene (MX@CNT) electrode arrays with a conductive network. Furthermore, we fabricate a homogeneous electrochemical (HEC) sensor for CEA detection by integrating a magnetic-bead-based alkaline phosphatase-linked immunoassay (MB-aElisa), which enables the in-situ generation of the electroactive substance 1-naphthol (1-NP). Benefiting from the unique electrochemical characteristics of a MX@CNT electrode array, such as ultra-low background signal and superior electrocatalytic activity towards the hydrolyzed 1-NP, the MB-aElisa-based HEC sensor specifically measures CEA within a detection range spanning from 0.005 to 1.0 ng mL-1, achieving a detection limit of 1.6 pg mL-1. Subsequently, this biosensing prototype is successfully utilized for the detection of CEA in serum specimens obtained from colorectal cancer patients. More importantly, the integration of MB-aElisa with a MX@CNT electrode array not only marks a significant advancement but also enables the creation of a one-step homogeneous electrochemical immunosensing platform, serving as a paradigm for the highly sensitive and selective measurement of trace tumor markers in complex biological samples.

Scalable drop-casting construction of light-addressable photoelectrochemical biosensor on laser-induced graphene electrode arrays for high-throughput drug screening.

A drop-casting method for the scalable construction of a solar cell-type light-addressable photoelectrochemical (PEC) sensor on commercial phenol resin (PR) plates is reported. The sensor was fabricated by laser writing of addressable laser-induced graphene (LIG) electrode arrays on PR plates with ring-disc dual-electrode cell configurations using a 405 nm laser machine. Beneficial from the good hydrophilicity of PR-based LIG and the excellent film formation of bismuth sulfide nanorods (Bi2S3 NRs), uniform Bi2S3 photovoltaic films can be reproducibly deposited onto the LIG disc photoanode array via drop casting modification, which show a sensitive photocurrent response toward thiocholine (TCl) when the ring cathode array was coated with Ag/AgCl. An acetylcholinesterase (AChE)-based PEC biosensor was therefore constructed by a similar drop-casting modification method. The resulting biosensor exhibits good sensitivity toward an AChE inhibitor, i.e., galantamine hydrobromide (GH), with a calibration range of 10-300 µM and a detection limit of 7.33 µM (S/N = 3). Moreover, the biosensor possesses good storage stability, which can achieve the high-throughput screening of AChE inhibitor drugs from traditional Chinese medicines (TCMs). The present work thus demonstrates the promising application of LIG technology in constructing light-addressable PEC sensing devices with high performance and low cost.

Machine Learning-Assisted Automatically Electrochemical Addressable Cytosensing Arrays for Anticancer Drug Screening.

The high-throughput and accurate screening of anticancer drugs is crucial to the preclinical assessment of candidate drugs and remains challenging. Herein, an automatically electrochemical addressable cytosensor (AEAC) for the efficient screening of anticancer drugs is reported. This sensor consists of sectionalized laser-induced graphene arrays decorated by the rhombohedral TiO2 and spherical Pt nanoparticles (LIG-TiO2-Pt) with high electrocatalytic activity for H2O2 and a homemade Ag/Pt electrode couple fixed onto the robot arm. The immobilization of laminin on the surface of LIG-TiO2-Pt can promote its biocompatibility for the growth and proliferation of various tumor cells, which empowers the in situ monitoring of H2O2 directly released from these live cells for drug screening. A machine learning (ML) algorithm is employed to eliminate the possible random or systematic errors of AEAC, realizing rapid, high-throughput, and accurate prediction of different types of anticancer drugs. This ML-assisted AEAC provides a powerful approach to accelerate the evolution of sensing-served tumor therapy.

Engineering Sandwiched Nanochannel Aptasensor for Efficiently Screening Cancer Cells.

Cancer cells are a class of important tumor biomarkers and are closely related to tumorous progression. It is urgent to develop a sensitive and highly efficient method for the rapid and accurate detection of cancer cells. Herein, an aptamer sandwiched nanochannel electrochemical sensor was established for the highly selective determination of cancer cells. By virtue of the porous nanochannels as the filter platform and immobilized with DNA aptamers for specifically capturing the cancer cells, the nanochannel-based electrochemical sensor denotes excellent performance for MCF-7 screening, and allowing a low limit of detection of 36 cells mL-1 . The nanochannels-based sandwich structure aptasensor not only presents an efficacious and reliable approach for cancer cell detection but also provides great advantage for preventing electrode passivation in the process of biomarkers analysis.

Photosensitive-Stamp-Inspired Scalable Fabrication Strategy of Wearable Sensing Arrays for Noninvasive Real-Time Sweat Analysis.

Wearable sweat sensing is essential to the development of personalized health monitoring in a noninvasive manner with molecular-level insight. Hence, there is an increasing demand for convenient, facile, and efficient fabrication of wearable sensing arrays. Inspired by a photosensitive stamp (PS), we present herein a simple, low-cost, and eco-friendly vacuum filtration-transfer printing method (termed PS-VFTP) for the scalable preparation of single-walled carbon nanotube (SWCNT) based flexible electrode arrays. This method can economically yield customized flexible SWCNT arrays with praiseworthy performance, such as high reproducibility, precision, uniformity, conductivity, and mechanical stability. In addition, the flexible SWCNT arrays can be easily functionalized into high-performance electrochemical sensors for the simultaneous monitoring of sweat metabolites (glucose, lactate) and electrolytes (Na+, K+). The integration of wearable sensing arrays with a signal acquisition and processing circuit system in the intelligent wearable sensors empowers them to realize noninvasive, real-time, and in situ sweat analysis during exercise. More meaningfully, such a PS-VFTP strategy can be easily expanded to the economical manufacturing of other flexible electronic devices.

Monodispersed Ni active sites anchored on N-doped porous carbon nanosheets as high-efficiency electrocatalyst for hydrogen peroxide sensing.

Metal active species combined with N-doped porous carbon nanosheets usually own excellent electrochemical activity and sensing performance owing to its unique microstructure and composition. In this work, monodispersed Ni active sites anchored on N-doped porous carbon nanosheets (Ni@N-PCN) were facilely prepared via rational metal-organic frameworks (MOFs) route. Firstly, zeolitic imidazolate frameworks-8 (ZIF-8) was in situ grown on physically-exfoliated graphene nanosheets (GN) with homogeneous sandwich-like structure (ZIF-8@GN). Secondly, nickel bonded ZIF-8@GN hybrids (Ni/ZIF-8@GN) were obtained by ionic exchange reaction, and then transformed into Ni@N-PCN by high-temperature pyrolysis. Benefiting from the monodispersed Ni active sites and highly reactive N-doped porous carbon nanosheets (N-PCN), the as-prepared Ni@N-PCN hybrids displayed superior catalytic performance toward hydrogen peroxide (H2O2) sensing. As a result, a highly sensitive electrochemical sensing platform for H2O2 was fabricated with low detection limit (0.032 µM), wide detection linearity (0.2-2332.8 µM), and high sensitivity (6085 µA cm-2 mM-1). Besides, the as-developed electrochemical sensing platform was successfully applied to detect H2O2 contents in biological medicine and food specimens with satisfied results. This study will provide effective guidance for the preparation of novel metal/N-doped carbon nanomaterials and establishment of high-performance electrochemical sensors.

Triethylamine-controlled Cu-BTC frameworks for electrochemical sensing fish freshness.

The simultaneous determination of xanthine (XA) and hypoxanthine (HXA) has been proved to be a feasible approach for the assessment of fish freshness. In this study, copper(II) nitrate and 1,3,5-benzenetricarboxylic acid (H3BTC) were used as precursors to prepare various Cu-BTC frameworks with the addition of various amounts of triethylamine at room temperature. The characterization of X-ray diffraction, Fourier-transform infrared spectroscopy and Raman spectroscopy testified that the obtained materials are Cu-BTC frameworks. However, the amount of triethylamine had significant effects on the morphology, active response area and electron transfer ability of Cu-BTC frameworks. The oxidation behavior of XA and HXA demonstrated that the prepared Cu-BTC frameworks exhibited higher sensing activity, with greatly-enhanced oxidation signals. More importantly, the amount of triethylamine obviously affected the accumulation capacity and signal enhancement ability of Cu-BTCs toward XA and HXA, as confirmed from double potential step chronocoulometry. Based on the triethylamine-tuned signal amplification strategy of Cu-BTC frameworks, a highly-sensitive and simple electrochemical sensing system was developed for the assessment of fish freshness by simultaneous detection of XA and HXA. The developed sensing method was used in practical samples, and the results were validated by high-performance liquid chromatography.

Reduced graphene oxide-ZnO nanocomposite based electrochemical sensor for sensitive and selective monitoring of 8-hydroxy-2'-deoxyguanosine.

Developing reliable and feasible electrochemical sensors for the detection of 8-hydroxy-2'-deoxyguanosine (8-OHdG) is important because the urinary level of 8-OHdG is related to cancer disease. Moreover, the co-existed uric acid (UA) as an interference severe affects the sensitive detection of 8-OHdG. Herein, sensitive monitoring of 8-OHdG was conducted using a nanocomposite of reduced graphene oxide (rGO) and ZnO nanoparticles (ZnO@rGO) as the sensing material. This nanocomposite was prepared via in-situ reduction of GO with Zn powders. Compared with those obtained on the unmodified glassy carbon electrode (GCE) and GO modified GCE (GO/GCE) the oxidation signals of 8-OHdG are significantly enhanced on the ZnO@rGO nanocomposite coated GCE (ZnO@rGO/GCE). Moreover, uricase has been employed successfully to eliminate the interferences of UA. A large amount of UA did not affect the oxidation signals of trace level of 8-OHdG. The linear range for the detection of 8-OHdG using ZnO@rGO/GCE was from 5.0 to 5000.0 nM. The detection limit was 1.25 nM calculated from a three-signal-to-noise ratio. The developed monitoring system is sensitive and selective for the determination of 8-OHdG and thus useful in practical applications, such as for the monitoring of 8-OHdG in the clinic urine samples.