Fang-Ting Zhang

Novel Homogeneous Label-Free Electrochemical Aptasensor Based on Functional DNA Hairpin for Target Detection

We first developed a label-free and immobilization-free homogeneous electrochemical aptasensor, which combined a smart functional DNA hairpin and a designed miniaturized electrochemical device. Cocaine was chosen as a model target. The anticocaine aptamer and peroxidase-mimicking DNAzyme were integrated into one single-stranded DNA hairpin. Both aptamer and G-quadruplex were elaborately blocked by the stem region. The conformation switching induced by the affinity interaction between aptamer and cocaine released G-quadruplex part and turned on DNAzyme activity. The designed electrochemical device, constructed by a disposable micropipet tip and a reproducible carbon fiber ultramicroelectrode, was applied to the detection of homogeneous DNAzyme catalytic activity at the microliter level. The aptasensor realized the quantification of cocaine ranging from 1 to 500 μM with high specificity. The clever combination of the functional DNA hairpin and the novel device achieved an absolutely label-free electrochemical aptasensor, which showed excellent performance like low cost, easy operation, rapid detection, and high repeatability.

Methylene blue as a G-quadruplex binding probe for label-free homogeneous electrochemical biosensing.

Herein, G-quadruplex sequence was found to significantly decrease the diffusion current of methylene blue (MB) in homogeneous solution for the first time. Electrochemical methods combined with circular dichroism spectroscopy and UV-vis spectroscopy were utilized to systematically explore the interaction between MB and an artificial G-quadruplex sequence, EAD2. The interaction of MB and EAD2 (the binding constant, K ≈ 1.3 × 10(6) M(-1)) was stronger than that of MB and double-stranded DNA (dsDNA) (K ≈ 2.2 × 10(5) M(-1)), and the binding stoichiometry (n) of EAD2/MB complex was calculated to be 1.0 according to the electrochemical titration curve combined with Scatchard analysis. MB was proved to stabilize the G-quadruplex structure of EAD2 and showed a competitive binding to G-quadruplex in the presence of hemin. EAD2 might mainly interact with MB, a positive ligand of G-quadruplex, through the end-stacking with π-system of the guanine quartet, which was quite different from the binding mechanism of dsDNA with MB by intercalation. A novel signal read-out mode based on the strong affinity between G-quadruplex and MB coupling with aptamer/G-quadruplex hairpin structure was successfully implemented in cocaine detection with high specificity. G-quadruplex/MB complex will function as a promising electrochemical indicator for constructing homogeneous label-free electrochemical biosensors, especially in the field of simple, rapid, and noninvasive biochemical assays.

Portable, Easy-to-Operate, and Antifouling Microcapsule Array Chips Fabricated by 3D Ice Printing for Visual Target Detection

Herein, we proposed a portable, easy-to-operate, and antifouling microcapsule array chip for target detection. This prepackaged chip was fabricated by innovative and cost-effective 3D ice printing integrating with photopolymerization sealing which could eliminate complicated preparation of wet chemistry and effectively resist outside contaminants. Only a small volume of sample (2 μL for each microcapsule) was consumed to fulfill the assay. All the reagents required for the analysis were stored in ice form within the microcapsule before use, which guaranteed the long-term stability of microcapsule array chips. Nitrite and glucose were chosen as models for proof of concept to achieve an instant quantitative detection by naked eyes without the need of external sophisticated instruments. The simplicity, low cost, and small sample consumption endowed ice-printing microcapsule array chips with potential commercial value in the fields of on-site environmental monitoring, medical diagnostics, and rapid high-throughput point-of-care quantitative assay.

Deuterated hydrazino-s-triazine as highly-efficient labelling reagent for glycan relative quantification analysis using electrospray ionization mass spectrometry

Herein, an innovative stable-isotope relative quantification strategy for N-glycans was achieved using a self-designed non-reductive hydrazino-s-triazine deuterated derivative as a labelling reagent combined with mass spectrometry. As much as a 20 Da mass shift could effectively distinguish different forms of N-glycans labelled with normal and heavy hydrazino-s-triazine at the reducing end. Especially for glycans with high molecular weight, qualitative identification could be significantly simplified on account of avoiding isotopic distributions overlapping in the mass spectra. Meanwhile, a deuterium derivative with high purity guaranteed the accuracy of the relative quantification. The obviously undifferentiated response toward normal and heavy hydrazino-s-triazine labelled glycans in electrospray ionization mass spectrometry confirmed the feasibility and reliability of our proposed strategy, which was further demonstrated by relative quantification of the mixtures of labelled N-glycans cleaved from ovalbumin as a model sample. Finally, we adopted human serum as a complex sample and successfully achieved highly accurate detection of 48 N-glycans. The deuterated hydrazino-s-triazine labelling reagent exhibited a great potential to promote the development of highly-efficient, accurate and reliable N-glycan relative quantification in pharmacy and diagnosis research.

Fabrication of silica nanowire bunch arrays in SiO vapor generated by oxygen plasma etching of silicon

This paper reports a three-step fabrication method for highly ordered silica nanowire bunch arrays of diversiform shapes. After patterning of organic polymers on Si substrates through photo lithography, oxygen plasma bombardment is applied to fabricate nanowire bunch arrays. On one hand, oxygen plasma exploits Si source from the substrates, and, subsequently, the gaseous Si react with active oxygen to form SiO vapor. On the other hand, oxygen plasma erodes the polymer patterns and, simultaneously, make them electrostatically attract the SiO material to form straight silica nanowire bunches. Based on this approach, standing nanowire bunch arrays of different sizes and different shapes are achieved on selective areas or structures. The nanowire bunches are able to bend toward a gallium focused-ion-beam irradiation, from different positions, in different directions and at different angles.

Ultrasensitive mass sensor using the out-of-phase vibration eigenstate of intercoupled dual-microcantilevers

This paper reports a kind of intercoupled silicon dual-microcantilevers for ultrasensitive mass detection based on the relative change in the amplitude ratio of the out-of-phase vibration eigenstate of the dual-cantilevers. The structural intercoupling of the dual-cantilevers arises from the coupling overhang connecting them at the base. The whole structure operation is excited by a piezoactuator under ambient conditions. Experimental results indicate that the relative change in the amplitude ratio of the out-of-phase vibration eigenstate of the structure is linear as a function of added mass, and it is more than one order of magnitude greater than the relative change in resonance frequency of in-phase vibration eigenstate.

Micrcapsule array fabricaed by ice-printing technology for on-site biochemical detection

In this paper, we proposed a portable, easy-to-operate, low cost and anti-fouling microcapsule array aiming for multitarget biochemical assay. This novel microcapsule array is achieved by ice printing and photopolymerization sealing. Only tiny amount of sample (2μL for each microcapsule) is needed to fulfill the assay. All the reagents required for the analysis are tightly sealed within the microcapsule in frozen or liquid form. With the aid of automatic equipment, the ice-printed microcapsule array chip can be massively produced, which enables its disposable use. Nitrite was chosen as a model target as a proof of concept. An instant qualitative detection by naked eyes was achieved without the need of any external sophisticated instruments. The quantitative detection was realized simply by camera photographing and image processing.