Jiadong Huang

A novel sandwich-type electrochemical aptasensor for sensitive detection of kanamycin based on GR–PANI and PAMAM–Au nanocomposites

In this work, we report a novel sandwich-type electrochemical aptasensor for sensitive and selective detection of antibiotic kanamycin. This aptasensor was constructed by assembling graphene–polyaniline (GR–PANI) and polyamidoamine dendrimer–Au nanoparticle (PAMAM–Au) nanocomposites on the surfaces of a glass carbon electrode, which as electrode materials exhibited excellent charge-transport property and loading capacity of biomolecules. Followed by the sandwich-type specific identification, kanamycin detection was realized by outputting a redox current from electro-reduction reaction of H2O2 catalyzed by HRP. It was demonstrated that the developed strategy had a wide linear response range from 5 × 10−6 to 4 × 10−2 μg mL−1 and a low detection limit of 4.6 × 10−6 μg mL−1. Additionally, this aptasensor had the advantages in its low cost, high sensitivity, and superb specificity. Thus, it might provide a useful tool for kanamycin determination and related food safety analysis and clinical diagnosis.

A novel sandwich-type electrochemical aptasensor based on GR-3D Au and aptamer-AuNPs-HRP for sensitive detection of oxytetracycline

In this paper, a novel sandwich-type electrochemical aptasensor has been fabricated and applied for sensitive and selective detection of antibiotic oxytetracycline (OTC). This sensor was based on graphene-three dimensional nanostructure gold nanocomposite (GR-3D Au) and aptamer-AuNPs-horseradish peroxidase (aptamer-AuNPs-HRP) nanoprobes as signal amplification. Firstly, GR-3D Au film was modified on glassy carbon electrode only by one-step electrochemical coreduction with graphite oxide (GO) and HAuCl4 at cathodic potentials, which enhanced the electron transfer and loading capacity of biomolecules. Then the aptamer and HRP modified Au nanoparticles provide high affinity and ultrasensitive electrochemical probe with excellent specificity for OTC. Under the optimized conditions, the peak current was linearly proportional to the concentration of OTC in the range of 5×10-10-2×10-3gL-1, with a detection limit of 4.98×10-10gL-1. Additionally, this aptasensor had the advantages in high sensitivity, superb specificity and showed good recovery in synthetic samples. Hence, the developed sandwich-type electrochemical aptasensor might provide a useful and practical tool for OTC determination and related food safety analysis and clinical diagnosis.

Visible photoelectrochemical sensing platform by in situ generated CdS quantum dots decorated branched-TiO2 nanorods equipped with Prussian blue electrochromic display

In this study, based on in situ generation of CdS quantum dots (QDs) on the surface of branched TiO2 (B-TiO2) nanorods, an solar innovative photoelectrochemical (PEC) sensing platform was constructed for real-time, and sensitive detection of cellular H2S. Specifically, B-TiO2 nanorods arrays consisting of TiO2 nanorods directly grown on fluorine-doped tin oxide (FTO) further using TiCl3 mediated surface treatment of TiO2 nanorods are designed and fabricated as a new type of photoelectrode. CdS quantum dots (QDs) was formed on the surface of B-TiO2 nanorods arrays through the reaction between Cd2+ and S2-. And a significant enhancement in the photocurrent was obtained that ascribed to the formation of CdS-B-TiO2 heterostructures, thus leading to sensitive PEC recording of the H2S level in buffer and cellular environments. By using Prussian blue (PB) a electrochromic material to capture the photoelectron generated from the photoelectrode, a new visual system was proposed due to the formation of Prussian white (PW), which could be used to visualize the quantum photoelectric effect. This novel PEC sensing platform not only achieved satisfied analysis results toward S2-, but also showed excellent sensitivity, selectivity, low cost, and portable features. The strategy through the in situ generation of semiconductor nanoparticles on the surface of wide band-gap semiconductor paves the way for the improvements of PEC analytical performance. Meanwhile, the quantitative read-out electrochromic display paves a facile avenue and initiates new opportunities for creation of cheap, miniaturization sensors for other relevant analytes.

Ultrasensitive and rapid detection of miRNA with three-way junction structure-based trigger-assisted exponential enzymatic amplification.

Aberrant expression of micro RNA (miRNA) is associated with development of cancers and diseases, so miRNA has become a tissue-based biomarker for cancer prognosis and diagnosis. Herein, a novel trigger-assisted exponential enzymatic amplification (T-EXPEA) method for ultrasensitive miRNA detection based on three-way junction (3-WJ) structure driven has been reported, which can be used in potential applications in cancer prognosis and diagnoses. In this assay, target miRNA can unfold hairpin probe and start the reaction, and thus specifically form stable 3-WJ structure with helper. Then it can produce triggers under the synergetic polymerase and restriction endonucleases amplification. The produced triggers could be used to unfold molecular beacon (MB) and initiate T-EXPEA process. In the EXPEA part, the exponential triggers were generated to initiate new T-EXPEA and high enhancement fluorescence amplification efficiency was obtained. The feature of our strategy lies in the T-EXPEA combining with 3-WJ structure has been utilized for fluorescence miRNA detection. It is worth noting that the sequence of the triggers in T-EXPEA part is the same to that of triggers generated from the 3-WJ part. In addition, the design of restriction enzyme cutting sites using the same restriction enzyme (Nt.BbvCI) in hairpin probe and MB respectively, improved reaction efficiency cost-efficiently. This method can quantitatively detect sequence-specific miRNA in a dynamic range from 10 aM to 10 pM with a detection limit as low as 7.8 aM.

An RNA aptamer-based electrochemical biosensor for sensitive detection of malachite green

An RNA aptamer-based electrochemical biosensing strategy has been developed for sensitive and selective detection of malachite green (MG). This biosensor is fabricated by the self-assembly of a thiolated MG aptamer (MGA) on AuNPs/graphene–chitosan nanocomposite modified glass carbon electrode. In addition, a short alkanethiol is further assembled on the AuNPs surface to generate uniform packing and reduce nonspecific adsorption. When the modified electrode is incubated in the presence of MG, MGA combines specifically with MG, which causes the horseradish peroxidase (HRP)-labelled MG antibody close to the electrode surfaces. As a result, MG detection is realized by outputting a redox current from electro-reduction of the hydrogen peroxide reaction catalyzed by HRP. Differential pulse voltammetry (DPV) is performed to record the signal responses. The results reveal the biosensor displays a very low detection limit as low as 16.3 pg mL−1 and a wide linear range from 1 × 10−4 to 10 μg mL−1 of MG. Hence, this proposed RNA aptamer-based electrochemical strategy may offer a simple, rapid, cost-effective, highly selective and sensitive method for the quantification of MG.

Signal-on electrochemical detection of antibiotics based on exonuclease III-assisted autocatalytic DNA biosensing platform

In this work, a novel electrochemical DNA sensor based on exonuclease III (Exo III)-assisted autocatalytic DNA biosensing platform for ultrasensitive detection of antibiotics has been reported. When the arched probe was challenged with target, the released primer caused by the specific recognition of the aptamer and target antibiotics hybridized with the 3′-protruding terminus in the HP1. Then, Exo III could catalyze the stepwise removal of mononucleotides from this flat terminus, resulting in the release of the primer and trigger. As a secondary target, trigger could replace Helper from the 5′-MB labeled HP2, and HP2 formed a “close” probe structure, confining MB close to the electrode surface for efficient electron transfer. To our best knowledge, such work is the first report about Exo III-assisted autocatalytic DNA biosensing platform combing with signal-on sensing strategy, which has been utilized for quantitative determination of antibiotics. It would be further used as a general strategy associated with more analytical techniques toward the detection of a wide spectrum of analytes. Thus, it holds great potential for the development of ultrasensitive biosensing platform for the applications in bioanalysis, disease diagnostics, and clinical biomedicine.

Target-activated cascaded digestion amplification of exonuclease III aided signal-on and ultrasensitive fluorescence detection of ATP

In this work, a rapid, one-step and ultrasensitive signal-on fluorescence sensing for the detection of adenosine triphosphate (ATP) based on target-activated cascaded digestion amplification with Exo III aid was developed. Our strategy integrates the target-activated cascaded digestion amplification with Exo III assistance into a signal-on fluorescence sensing platform. This advance greatly enhances the specificity and significantly improves the sensitivity for ATP detection. Specifically, an arch probe containing an anti-ATP aptamer (Apt) and a trigger probe (T) is used for recognizing the target. In the presence of ATP, the cascaded digestion amplification with the help of Exo III was activated, generating a remarkably strong signal-on fluorescence response. Our strategy features several virtues. First, the background signal is effectively eliminated owing to the specially designed hairpin probes (one is named HAP, the other is named MB short for molecular beacon) successfully avoiding the effect of Exo III. Second, the combination of target-activation with Exo III-aided cascade digestion amplification is integrated with fluorescence sensing, affording high specificity and ultrasensitive detection of ATP. Third, our method achieved the reliable and accurate detection of ATP in human serum. Furthermore, under optimized conditions, the results suggest that the proposed fluorescence sensing exhibits excellent specificity and ultrasensitivity toward ATP with the limit of detection as low as 0.63 pM and the broad analytical range from 1 pM to 1.0 × 105 pM. This target-activated cascaded digestion amplification with Exo III assistance combined with the fluorescence sensing strategy paves a luciferous and practical way for detecting ATP and other analytes with trace amounts in bio-analysis and clinical biomedicine.