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A nucleic acid dye-enhanced electrochemical sensor was designed based on an Au nanoparticle (AuNPs)-modified screen-printed carbon electrode (SPCE) and a thymine (T)–Hg2+–thymine (T) mismatch for the detection of Hg2+ in water.

In this paper, a nucleic acid dye-enhanced electrochemical biosensor based on a screen-printed carbon electrode (SPCE) modified with Au nanoparticles (AuNPs) was designed for the detection of Hg

The quantification of proteins is essential in fundamental research or clinical applications. Here, we developed a facile electrochemical aptasensor based on target-induced turn-off of photosensitization for label-free and ultrasensitive detection of protein (exemplified by lysozyme). EB (ethidium bromide) molecules that were embedded in dsDNA between lysozyme binding aptamer and complementary DNA immobilized on the electrode, could photo-cleave the dsDNA via singlet oxygen (O21) during photosensitization, resulting in a high voltammetry current of the [Fe(CN)6]3-/4-. Upon recognition of the lysozyme by aptamer, the EB molecules were released from dsDNA, and its photosensitization activity was turned off. As a result, more amount of complementary DNA was retained on the Au nanoparticles modified carbon nanotube paste electrode (AuNPs-CNPE), leading to a declined voltammetry current. Such a sensing strategy allowed detection of 10 pM-1 µM lysozyme with a low detection limit (about 2 pM). Besides, the sensor was free of labeling procedure as well as extra signal amplification step, and the CNPE modification was quite simple, only with AuNPs. The sensor also showed excellent selectivity toward lysozyme in the presence of interfering proteins, such as thrombin, bovine serum albumin, myoglobin, etc. The proposed sensor was applied to the determination of lysozyme in urine samples with the recoveries ranging from 96.6% to 101%. The proposed biosensor holds a great promise in developing other electrochemical sensors based on photosensitization.

An ultrasensitive 1O2-based electrochemical aptasensor by on-line assembly of photosensitizers using graphene oxide (GO) as a cartridge is reported. In the presence of target protein lysozyme, the interaction of lysozyme with aptamer led to the dissociation of dsDNA and release of the aptamer-lysozyme complex to solution, with DNA-c retaining on the electrode; then, the photosensitizer phloxine B (PB) was assembled on the electrode since GO can simultaneously adsorb DNA-c and PB molecules. Upon irradiation by a green LED, 1O2 was generated by photocatalysis of PB molecules and then cleaved the DNA-c, leading to remarkably decreased impedance signals that linearly respond with the logarithm of lysozyme concentration. Benefitting from the efficient photosensitization ability of PB and the high PB-loading capacity of GO, the developed sensor allowed determination of 0.001 to 100 nM lysozyme with a limit of detection of about 0.14 pM. The relative standard deviation (RSD) for five independent electrodes with 1 nM lysozyme was 3.1%, indicating satisfactory reproducibility. The sensor also showed excellent selectivity toward lysozyme in the presence of interfering substances and was applied to the determination of lysozyme in urine samples with recoveries ranging from 91 to 101%. The on-line assembly of photosensitizer technique opens a new way for amplified electrosensing of biomolecules.

An ultrasensitive