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.