Panpan Gai

Ultrasensitive Self-Powered Aptasensor Based on Enzyme Biofuel Cell and DNA Bioconjugate: A Facile and Powerful Tool for Antibiotic Residue Detection

Herein, we reported a novel ultrasensitive one-compartment enzyme biofuel cells (EBFCs)-based self-powered aptasensing platform for antibiotic residue detection. By taking full advantage of the unique features of both EBFCs-based self-powered sensors and aptamers, the as-proposed aptasensing platform has the merits of simple instrumentation, anti-interference ability, high selectivity, and low cost. In this study, DNA bioconjugate, i.e., SiO2@gold nanoparticles-complementary strand of aptamer (SiO2@AuNPs-csDNA), was elaborately designed and played a key role in blocking the mass transport of glucose to the bioanode. While in the presence of the target antibiotic, SiO2@AuNPs-csDNA bioconjugate broke away from the bioanode due to the aptamer recognition of the target. Without the blocking of glucose by the DNA bioconjugate, a significantly elevated open circuit voltage of the EBFCs-based aptasensor was obtained, whose amplitude was dependent on the antibiotic concentration. In addition, this proposed aptasensor was the first reported self-powered aptasensing platform for antibiotic determination and featured high sensitivity owing to the elaborate design of the DNA bioconjugate modified bioanode of EBFC, which was superior to those previously reported in the literature. Furthermore, due to the anti-interference ability and the excellent selectivity of the aptasensor, no special sample pretreatment was needed for the detection of antibiotics in milk samples. Therefore, the proposed EBFCs-based self-powered aptasensor has a great promise to be applied as a powerful tool for on-site assay in the field of food safety.

Ultrasensitive Ratiometric Homogeneous Electrochemical MicroRNA Biosensing via Target-Triggered Ru(III) Release and Redox Recycling

A new label-free and enzyme-free ratiometric homogeneous electrochemical microRNA biosensing platform was constructed via target-triggered Ru(III) release and redox recycling. To design the effective ratiometric dual-signal strategy, [Ru(NH3)6]3+ (Ru(III)), as one of the electroactive probes, was ingeniously entrapped in the pores of the positively charged mesoporous silica nanoparticle (PMSN), and another electroactive probe, [Fe(CN)6]3- (Fe(III)), was selected to facilitate Ru(III) redox recycling due to its distinctly separated reduction potential and different redox properties. Owing to the liberation of the formed RNA-ssDNA complex from PMSN, the target miRNA triggered the Ru(III) release and was quickly electroreduced to Ru(II), and then, the in-site-generated Ru(II) could be chemically oxidized back to Ru(III) by Fe(III). Thus, with the release of Ru(III) and the consumption of Fe(III), a significant enhancement for the ratio of electroreduction current [Ru(NH3)6]3+ over [Fe(CN)6]3- (IRu(III)/IFe(III)) value was observed, which was dependent on the concentration of the target miRNA. Consequently, a simple, accurate, and ultrasensitive method for the miRNA assay was readily realized. Furthermore, the limit of detection (LOD) of our method was down to 33 aM (S/N = 3), comparable or even superior to other approaches reported in literature. More importantly, it also exhibited excellent analytical performance in the complex biological matrix cell lysates. Therefore, this homogeneous biosensing strategy not only provides an ingenious idea for realizing simple, rapid, reliable, and ultrasensitive bioassays but also has a great potential to be adopted as a powerful tool for precision medicine.

Synthesis of a three-layered SiO2@Au nanoparticle@polyaniline nanocomposite and its application in simultaneous electrochemical detection of uric acid and ascorbic acid

Novel nanocomposites fabricated by incorporating different types of nanomaterials, especially inorganic and organic nanomaterials, have attracted much attention, and shown promising prospects in the applications in biological research fields. Herein, we propose a facile method to synthesize a novel three-layered SiO2@Au nanoparticle@polyaniline nanocomposite, which exhibited excellent electrical conductivity and good dispersibility in water. The as-proposed nanocomposite has been adopted to construct the modified electrode SiO2@AuNP@PANI/CS/GCE, which was characterized by electrochemical impedance spectroscopy and cyclic voltammetry, and demonstrated excellent electrochemical behaviors in neutral and even alkaline media, making it suitable for sensing species in biological fluids under physiological conditions. Moreover, the SiO2@AuNP@PANI/CS/GCE exhibited excellent catalytic activity towards the electro-oxidation of uric acid (UA) and ascorbic acid (AA), and a difference of 384 mV between the oxidation potentials for UA and AA was obtained, which is large enough for the selective and simultaneous determination of UA and AA in a binary mixture. Thus, the modified electrode has been successfully adopted for the simultaneous electrochemical detection of UA and AA, and the detection limits of 2 μM and 6 μM were obtained, respectively.

Enzymatic Fuel Cell-Based Self-Powered Homogeneous Immunosensing Platform via Target-Induced Glucose Release: An Appealing Alternative Strategy for Turn-On Melamine Assay

Enzymatic fuel cell (EFC)-based self-powered biosensors have attracted considerable attention because of their unique feature of no need for extra power sources during the entire detection process, which endows them with the merits of simplicity, rapidness, low cost, anti-interference, and ease of use. Herein, we proposed, for the first time, an EFC-based self-powered homogeneous immunosensing platform by integrating the target-induced biofuel release and bioconjugate immunoassay for ultrasensitive melamine (ME) detection. In this design, the biofuel, i.e., glucose molecules, was entrapped in the pores of positively charged mesoporous silica nanoparticles and capped by the biogate AuNPs-labeled anti-ME antibody (AuNPs-Ab). The presence of the target ME triggered the entrapped glucose release due to the removal of the biogate via immunoreaction, which resulted in the transfer of electrons produced by glucose oxidation at the bioanode to the biocathode, and thus, the open-circuit voltage of the EFC-based self-powered immunosensor dramatically increased, realizing the ultrasensitive turn-on assay for ME. The limit of detection for ME assay was down to 2.1 pM (S/N = 3), superior to those previously reported in the literature. Notably, real milk samples need no special sample pretreatment for the detection of ME because of the good anti-interference ability of EFC-based self-powered biosensors and the excellent selectivity of the homogeneous immunoassay. Therefore, this appealing self-powered homogeneous immunosensing platform holds great promise as a successful prototype of portable and on-site bioassay in the field of food safety.

Unique quenching of fluorescent copper nanoclusters based on target-induced oxidation effect: a simple, label-free, highly sensitive and specific bleomycin assay

In this contribution, a novel label-free fluorescence biosensor for bleomycin (BLM) detection was developed by combining the excellent fluorescence properties of copper nanoclusters (CuNCs) and the unique oxidation capability of a BLM–Fe2+ complex toward CuNCs. The CuNCs probe was prepared through in situ formation of CuNCs using single-stranded DNAs as the templates, endowing the probe with good water-dispersibility that is important for analyzing biological samples. After their recognition of BLM, the CuNCs were destroyed and the red fluorescence of the probe was quenched, thus realizing the detection of BLM. Such a fluorescence sensing strategy allows for highly sensitive BLM biosensing with a detection limit as low as 0.26 nM and minimal interference from complex mixtures. Compared to previously reported methods, the as-proposed assay does not need specific DNA sequences, complex designing or signal molecule labeling, and further avoids tedious experimental procedures, thus providing the strategy with additional advantages of simplicity and cost-effectiveness. Furthermore, our probe was also adopted for the detection of BLM in human serum samples and excellent performance was achieved, which makes the as-proposed strategy a promising candidate for highly sensitive and specific analysis of BLM in cancer treatment.

Target-induced diffusivity enhancement for rapid and highly sensitive homogeneous electrochemical detection of BLM in human serum

A simple, rapid, and sensitive homogeneous electrochemical bleomycin (BLM) bioassay has been successfully developed through the target-induced specific/efficient cleavage reaction. The designed probe, denoted as MB-DNA, contains both methylene blue (MB) and target recognizable sequences, and presents relatively low electrochemical signal. Upon the addition of BLM, the recognition/cleavage reaction occurs and leads to the in-situ generation of MB tag (MB-DNA-1), leading to the reduced electrostatic repulsive force. As a result, an obvious enhancement in differential pulse voltammetry (DPV) current is determined, which is relied on the amount of BLM. Thus, a turn on homogeneous electrochemical method for BLM is really achieved, and exhibits high sensitivity of 33 pM, and the shortest response time of 20 min. Furthermore, this electrochemical bioassay presents excellent sensing performance in the analysis of BLM in real samples. Comparing with other sensing strategies for BLM, this proposed electrochemical platform is just consisted of one DNA probe alone, and affords a really rapid and sensitive strategy for BLM analysis.

Light-Driven Self-Powered Biosensor for Ultrasensitive Organophosphate Pesticides Detection via Integration of the Conjugated Polymer Sensitized CdS and Enzyme Inhibition Strategy

Herein, a light-driven self-powered biosensor based on a photoelectrochemical enzymatic fuel cell (PEFC) was proposed for ultrasensitive organophosphate pesticide (OP) detection. To construct this fuel cell, poly(3,4-ethylenedioxythiophene)-sensitized CdS quantum dot (PEDOT/CdS) photoanode and multiwalled carbon nanotubes/gold nanoparticals/bilirubin oxidase (CNTs/AuNPs/BOD) biocathode were elaborately designed. Initially, the enzyme acetylcholinesterase (AChE) immobilized on the CdS/PEDOT photoanode could hydrolyze acetylthiocholine iodide (ATCh) into thiocholine as the electron donor to enhance the charge separation efficiency; thus, PEFC produced relatively high open circuit voltage (EOCV) upon illumination. OPs could inhibit the AChE enzymatic catalytic activity on hydrolysis, and in this case, a smaller EOCV obtained. Thus, based on the constructed PEFC, self-powered biosensing of OPs was realized, and the detection limit was as low as 0.012 ng mL-1 (S/N = 3), which was comparable or superior to those of the reported methods. In this study, we not only constructed a facile, ultrasensitive and low-cost sensing platform for OP detection, but also provided an ingenious idea for designing light-driven self-powered biosensing based on PEFC.

Label-Free and Ultrasensitive Biomolecule Detection Based on Aggregation Induced Emission Fluorogen via Target-Triggered Hemin/G-Quadruplex-Catalyzed Oxidation Reaction

Fluorescence biosensing strategy has drawn substantial attention due to their advantages of simplicity, convenience, sensitivity, and selectivity, but unsatisfactory structure stability, low fluorescence quantum yield, high cost of labeling, and strict reaction conditions associated with current fluorescence methods severely prohibit their potential application. To address these challenges, we herein propose an ultrasensitive label-free fluorescence biosensor by integrating hemin/G-quadruplex-catalyzed oxidation reaction with aggregation induced emission (AIE) fluorogen-based system. l-Cysteine/TPE-M, which is carefully and elaborately designed and developed, obviously contributes to strong fluorescence emission. In the presence of G-rich DNA along with K+ and hemin, efficient destruction of l-cysteine occurs due to hemin/G-quadruplex-catalyzed oxidation reactions. As a result, highly sensitive fluorescence detection of G-rich DNA is readily realized, with a detection limit down to 33 pM. As a validation for the further development of the proposed strategy, we also successfully construct ultrasensitive platforms for microRNA by incorporating the l-cysteine/TPE-M system with target-triggered cyclic amplification reaction. Thus, this proposed strategy is anticipated to find use in basic biochemical research and clinical diagnosis.