Based on ligand assembly between l-arginine and 4-hydroxy-2-mercapto-6-methylpyrimidine, gold nanoclusters with enhanced electrochemiluminescence efficiency and stability were prepared for the detection of hemoglobin in urine samples.

Electrochemiluminescence (ECL) is a powerful tool for clinical diagnosis due to its exceptional sensitivity. However, the standard tripropylamine (TPrA) coreactant for Ru(bpy)3Cl2, the most widely studied and used ECL system, is highly toxic. Despite extensive research on alternative coreactants, they often fall short in poor efficiency. From a reaction kinetics perspective, accelerating electrooxidation rate of Ru(bpy)3Cl2 is an essential way to compensate the efficiency limitation of coreactants, but is rarely reported. Here, a hybrid electrocatalyst@coreactant dots for the ECL of Ru(bpy)3Cl2 is reported. The as-prepared WSe2@bovine serum albumin (WSe2@BSA) dots is biocompatible, and demonstrate dual functions, i.e., the BSA shell works as a coreactant, meanwhile, the WSe2 core effectively catalyzes Ru(bpy)3Cl2 oxidation. As a result, WSe2@BSA dots exhibit an exceptionally high efficiency comparable to TPrA for the ECL of Ru(bpy)3Cl2. In addition, the procedure for synthesizing WSe2@BSA dots is facile (room temperature, atmospheric conditions), rapid (5 min), and scalable (for millions of bioassays). A biosensor utilizing WSe2@BSA dots shows promise for highly sensitive detecting glypican-3 in clinical liver cancer serum samples, especially for alpha-fetoprotein-negative patients. This work opens a new avenue for developing a highly efficient ECL system for biosensing and clinical diagnosis.

Gold nanoclusters (Au NCs) have appeared as an essential alternative to traditional quantum dots and fluorescent molecules for the development of intelligent stimuli-responsive photoluminescence (PL), but the low PL emission of Au NCs restricts their broad applications. Herein, we reported a simple yet effective strategy for preparing Au NCs with high PL by ligands engineering of 4-hydroxy-2-mercapto-6-methylpyrimidine (MTU) and L-Arginine (Arg). Owing to the rigidified shell and the ligand-to-metal charge transfer (LMCT) effects, it was found that the assembly of Arg ligand on MTU-protected Au NCs (Arg/MTU-Au NCs) led to a significantly enhanced PL in the alkaline solution up to 30 times. Moreover, utilizing the tunable LMCT, the Arg/MTU-Au NCs displayed rapid responses to multi-type ionic interaction in a reversible manner, such as H+/OH- and Cu2+/glutathione (GSH) pairs. Inspired by these intriguing ions-responsive LMCT and the associated switchable PL emission, the Arg/MTU-Au NCs were successfully used as excellent stimuli-responsive PL probes for intriguing deceptive information encryption and biosensing as well. This work would provide new insight into regulating the PL emission of Au NCs by ligands engineering and advance their potential applications in information encryption and bioassay.

Photoelectrochemical (PEC) sensing enables the rapid, accurate, and highly sensitive detection of biologically important chemicals. However, achieving high selectivity without external biological elements remains a challenge because the PEC reactions inherently have poor selectivity. Herein, we report a strategy to address this problem by regulating the charge-transfer pathways using polymeric carbon nitride (pCN)-based heterojunction photoelectrodes. Interestingly, because of redox reactions at different semiconductor/electrolyte interfaces with specific charge-transfer pathways, each analyte demonstrated a unique combination of photocurrent-change polarity. Based on this principle, a pCN-based PEC sensor for the highly selective sensing of ascorbic acid in serum against typical interferences, such as dopamine, glutathione, epinephrine, and citric acid was successfully developed. This study sheds light on a general PEC sensing strategy with high selectivity without biorecognition units by engineering charge-transfer pathways in heterojunctions on photoelectrodes.

Alzheimer’s disease (AD) is the most common neurodegenerative disease and is manifested by memory loss and spatialdisorientation. There is currently no effective treatment for AD. Abnormalities of the chromosome 9 open reading frame72 (C9orf72) gene have been associated with various neurodegenerative diseases. However, its intrinsic roles in AD remainto be elucidated. Here we found that Aβ25‑35 increased the expression of C9orf72 in PC12 cells at both mRNA and proteinlevels. In Aβ25‑35‑treated PC12 cells, C9orf72 overexpression induced an abnormally condensed and fragmented nucleus andapoptosis, as well as significantly enhanced reactive oxygen species (ROS) levels. Mechanistically, an Aβ25‑35‑induced decreaseof superoxide dismutase activity was augmented by C9orf72 overexpression, which in contrast increased malondialdehydecontent. Consistently, further apoptotic analysis revealed significant downregulation of Bcl‑2 and Bcl‑xL expression andenhanced cleavage of caspase‑3 with Aβ25‑35 treatment, all of which were exacerbated by C9orf72 overexpression. In addition,tau phosphorylation, another hallmark of AD pathology, was induced by Aβ25‑35 and was remarkably enhanced by C9orf72overexpression. Our data indicate that C9orf72 plays important roles in intracellular ROS signaling and Aβ25‑35‑induced neuronalapoptosis in AD. These findings provide insights into C9orf72 function in the pathogenesis of many related neurodegenerativediseases and provide a basis for potential therapeutic interventions.

Carbon dots (CDs) have shown enormous potential as electrochemiluminescence (ECL) probes for biosensing and bioimaging applications due to their ease of synthesis and modification, high biocompatibility, stable optical and electrochemical properties. However, the mild ECL emission of CDs often restricts their practical applications. Herein, an ECL biosensor for mutant BRAF gene determination was proposed based on the surface plasmon resonance-enhanced ECL (SPR-ECL) between asymmetrically modified amine-gold nanodendrites (am-AuNDs) and phosphorus (P) and nitrogen (N) co-doped CDs (PNCDs). Compared to the N-doped CDs (NCDs), PNCDs exhibited an 8-fold enhanced ECL because of the larger atom size and higher electron-donating ability of P atom compared to N. Due to the surface plasmon resonance effect of am-AuNDs and proper distance controlled by catalytic hairpin assembly (CHA), the ECL signal of PNCDs was remarkably improved based on a nonradiative energy transfer between PNCDs and the am-AuNDs. The as-constructed SPR-ECL biosensor performed well for the detection of mutant B-type Raf kinase (BRAF) gene with high sensitivity, stability and accuracy in the range from 0.5 pM to 2000 pM with a limit of detection (LOD) of 0.34 pM. This work would open a new avenue to boost the ECL performance of carbon nanomaterials for practical applications, especially for bioanalysis and diagnostics.

A "signal-on" photoelectrochemical (PEC) immunosensor for highly sensitive detection of Human Epididymis Protein 4 (HE4), a new serum biomarker of ovarian cancer with small molecular weight, was fabricated by coupling the porphyrin-based metal-organic framework (MOF) nanosphere (nPCN-224) and Nanobody (Nb). To label the Nb, the nPCN-224 with an average size of 160-200 nm was prepared by solvothermal method. The mechanism for the photocurrent generation of nPCN-224 was systematically investigated, showing that the dissolved O-2 in aqueous solution participated in the charge separation and transport during the photoelectric conversion by generating O-2(-), which resulted in a 6-fold enhanced photocurrent by using ascorbic acid as the O-2(-) scavenger. Moreover, the inherent structural porosity of nPCN-224 demonstrated advantage for reactant accessibility. Due to the superior properties of nPCN-224, and the high specificity and affinity of Nbs, the immunosensor exhibited a broad detection range from 1.00 pg mL(-1) to 10.0 ng mL(-1) and a detection limit of 0.560 pg mL(-1), lower than most methods reported before. The immunosensor could clearly distinguish ovarian cancer patients in different stages from healthy individuals, and the as-obtained results matched well with those by traditional electrochemiluminescence immunoassay method from the hospital. This work would open a new avenue for PEC immunosensors in clinical diagnostics and evaluation of potential clinical efficacy. (C) 2020 Elsevier B.V. All rights reserved.

A simple photoelectrochemical (PEC) immunoassay based on an amino-terminated perylene derivative (PTCNH2) was developed for highly sensitive and specific detection of tumor necrosis factor-alpha (TNF-alpha). Simple grinding and sonication afforded a pi-pi stacked graphene oxide (GO)/PTCNH2 assembly exhibiting fast electron transfer kinetics and excellent photoelectric performance, and this assembly was applied as a PEC probe. The GO-PTCNH2 assembly provided not only a large surface area, fast electron transfer kinetics and abundant active sites for further biomolecule conjugation but also high PEC activity. A "signal-off" PEC immunoassay for TNF-alpha was developed by assembling GO-PTCNH2 on the electrode, followed by conjugation of anti-TNF-alpha with GO-PTCNH2 and subsequent capture of the target protein TNF-alpha. The linear detection range was from 10 pg/mL-100 ng/mL with a limit of detection (LOD) of 3.33 pg/mL. This method was also successfully applied for detecting TNF-alpha in human serum with recoveries ranging from 92,5% to 96.6% and a relative standard deviation of less than 9.99%. For the first time, this work reports a simple PEC immunoassay achieved by using PTC-NH2 as a photoelectrochemically active probe for the detection of a tumor biomarker. This assay could be applicable to the detection of other biomarkers for clinical diagnosis.

Aflatoxin B1 (AFB1 ), one of the most toxic mycotoxins, is classified as a group I carcinogen and ubiquitous in various foods and agriproducts. Thus, accurate and sensitive determination of AFB1 is of great significance to meet the criteria of food safety. Direct detection of AFB1 is difficult by monoclonal antibody (mAb) with large molecular size (≈150 kD) since the target is too small to produce a detectable signal change. Herein, by combining the electrochemical properties of nanomaterials and the advantages of nanobodies, we developed a direct, highly selective and sensitive electrochemical immunosensor for small molecule detection. The proposed immunosensor had a wide calibration range of 0.01 to 100 ng mL-1 and a low detection limit of 3.3 pg mL-1 (S/N=3). Compared with the immunosensor prepared with mAb which was applied in the typical indirect immunoassay, the immunosensor in this work possessed two orders of magnitudes wider linear range and 10-fold more sensitivity. The as-obtained immunosensor was further successfully applied for sensing AFB1 in real samples. This proposed assay would provide a simple, highly sensitive and selective approach for the direct immunoassay of small molecule AFB1 , and is extendable to the development of direct immunosensing systems for other small molecules detection by coupling nanocarbon and nanobody.

The problems of environmental security and the potential risks of human health caused by transgenic crops have attracted much attention. Recent studies reveal 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) from Agrobacterium sp. strain CP4 protein (CP4-EPSPS), which shows very high resistance to herbicide glyphosate, is a typical biomarker of genetically modified (GM) crops. For this reason, it is highly anticipated to devise a sensitive and convenient strategy to detect CP4-EPSPS protein in crops. Herein, we report a simple electrochemical immunosensor by coupling nanobody, ordered mesoporous carbon (OMC), and thionine (Th). As a capture agent, the nanobody was screened out from an immunized Bactrian camel, and exhibited superior properties with respect to conventional antibody, such as higher stability and stronger heat resistance. Moreover, OMC offered an effective platform with high surface area, electrical conductivity, and biocompatibility, which greatly facilitated the assembly of redox probe Th, and further coupling of large amount of capture nanobodies. As a result, the CP4-EPSPS protein could be determined with high sensitivity and efficiency by differential pulse voltammetry (DPV) in a wide linear range from 0.001 to 100 ng·mL-1 with a low detection limit of 0.72 pg·mL-1, which was more than 3 orders of magnitude lower than those of previously reported works. As an example, the proposed electrochemical immunosensor was successfully applied to spiked samples, demonstrating its great potential in CP4-EPSPS screening and detection.