Xanthine microsensor based on polypyrrole molecularly imprinted film modified carbon fiber microelectrodes

A dual-functional module cellular electrochemical sensing platform for simultaneous detection guanine and xanthine

The separation of the superimposed electrochemical signals of intracellular guanine (G) and xanthine (X) is difficult, which is great obstacle to the application of cell electrochemistry. In this paper, independent functional modules, G-functional module (G-FM) and X-functional module (X-FM), were constructed by molecular imprinting technology for sensitive detection of G and X without mutual interference, then integrated in dual-functional module cellular electrochemical sensing platform (DMCEP) as signal sensing units. DMCEP transmitted signals of G and X in cells synchronously to two windows by two signal sensing channels, and achieved the separation of superimposed signals of G and X in cells. DMCEP exhibited satisfactory reproducibility with relative standard deviation (RSD) of 3.10 and 2.22 %, repeatability with RSD of 3.72 and 3.05 % for G and X detection, and detection limit 0.05 μΜ for G and 0.06 μΜ for X. Good linear relationships between cell concentrations and the signals of G and X on DMCEP were shown in range of 0.75-85 × 10⁶ and 3-85 × 10⁶ cells/mL, respectively. The growth of MCF-7 cells was tracked by DMCEP, and showed consistent trend with the cell counting method, while the change of cell viability from lag to logarithmic phase captured by DMCEP was earlier than that of cell counting method. This strategy provided the foundation for the establishment of the cell viability electrochemical detection method, and new insights into the simultaneous recording of other analyses with superimposed peak positions and the simultaneous tracking of multiple biomarkers.

Fabrication of a Selective and Sensitive Sensor Based on Molecularly Imprinted Polymer/Acetylene Black for the Determination of Azithromycin in Pharmaceuticals and Biological Samples

A new selective and sensitive sensor based on molecularly imprinted polymer/acetylene black (MIP/AB) was developed for the determination of azithromycin (AZM) in pharmaceuticals and biological samples. The MIP of AZM was synthesized by precipitation polymerization. MIP and AB were then respectively introduced as selective and sensitive elements for the preparation of MIP/AB-modified carbon paste (MIP/ABP) electrode. The performance of the obtained sensor was estimated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. Compared with non-molecularly imprinted polymer (NIP) electrodes, NIP/ABP electrodes, and MIP-modified carbon paste electrodes, MIP/ABP electrode exhibited excellent current response toward AZM. The prepared sensor also exhibited good selectivity for AZM in comparison with structurally similar compounds. The effect of electrode composition, extraction parameters, and electrolyte conditions on the current response of the sensor was investigated. Under the optimized conditions, the prepared sensor showed two dynamic linear ranges of 1.0 × 10⁻⁷ mol L⁻¹ to 2.0 × 10⁻⁶ mol L⁻¹ and 2.0 × 10⁻⁶ mol L⁻¹ to 2.0 × 10⁻⁵ mol L⁻¹, with a limit of detection of 1.1 × 10⁻⁸ mol L⁻¹. These predominant properties ensured that the sensor exhibits excellent reliability for detecting AZM in pharmaceuticals and biological fluids without the assistance of any separation techniques. The results were validated by the high-performance liquid chromatography–tandem mass spectrometry method.

A facile one-pot method to synthesize a polypyrrole/hemin nanocomposite and its application in biosensor, dye removal, and photothermal therapy

In this work, we introduced a facile method for the construction of a polypyrrole/hemin (PPy/hemin) nanocomposite via one-pot chemical oxidative polymerization. In this process, a hemin molecule serving as a dopant was entrapped in the PPy nanocomposite during chemical oxidative polymerization. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and UV-visible spectroscopy results demonstrated that the PPy/hemin nanocomposite was successfully synthesized. The as-prepared nanocomposite exhibited intrinsic peroxidase-like catalytic activities, strong adsorption properties, and an excellent near-infrared (NIR) light-induced thermal effect. We utilized the nanomaterials to catalyze the oxidation of a peroxidase substrate 3,3,5,5-tetramethylbenzidine by H2O2 to the oxidized colored product which provided a colorimetric detection of glucose. As low as 50 μM glucose could be detected with a linear range from 0.05 to 8 mM. Moreover, the obtained nanocomposite also showed excellent removal efficiency for methyl orange and rhodamine B and a photothermal effect, which implied a promising application as the pollutant adsorbent and photothermal agent. The unique nature of the PPy/hemin nanocomposite makes it very promising for the fabrication of inexpensive, high-performance bioelectronic devices in the future.