A new strategy for methylated DNA detection based on photoelectrochemical immunosensor using Bi2S3 nanorods, methyl bonding domain protein and anti-his tag antibody

• DNA methylation was detected by a novel photoelectrochemical (PEC) immunosensor.
• The photoelectrochemical signal was produced by Bi2S3 nanoparticles.
• Methylated DNA was recognized by methyl bonding domain (MBD) protein.
• The photoelectrochemical signal decreased after capturing MBD protein and his-tag antibody.
• The immunosensor showed a low detection limit of 3.5×10–14 M.

In this work, we fabricated a novel photoelectrochemical immunosensor for assay of DNA methylation, where Bi2S3 nanorods were used as photoelectric conversion material, MBD1 protein (a kind of methyl bonding domain protein) was used as DNA methylation recognizing unit, anti-his tag antibody was used to further inhibit the photocurrent and increase the detection sensitivity. The results demonstrated that Bi2S3 possessed excellent photoelectron property. The detection conditions, such as Bi2S3 concentration, MBD1 protein concentration, incubation time of MBD1 protein, antibody concentration and antibody incubation time, were optimized. Under optimal experimental conditions, the photocurrent variation was proportional to the logarithm of methylated target DNA concentration from 10−9 to 10–13 M with detection limit of 3.5×10–14 M (S/N=3). Moreover, the immunosensor presented high detection specificity, even distinguishing single-base mismatched sequence.

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