Colorimetric detection of metallothioneins using a thymine-rich oligonucleotide–Hg complex and gold nanoparticles

A simple and sensitive method for label-free, colorimetric detection of metallothioneins (MTs) has been developed by using a thymine (T)-rich oligonucleotide (TRO)–Hg–AuNP system. In this colorimetric strategy, the thiol groups of MTs could interact with mercury from the T–Hg2+–T complex to release TRO, resulting in a color change of the system. The response signals linearly correlated with the concentration of MTs over the range of 2.56 × 10−8 to 3.08 × 10−7 mol L−1, and the limit of detection was 7.67 × 10−9 mol L−1. The relative standard deviation and the recovery were 2.3–4.8% (n = 11) and 94.2–103.9%, respectively. The proposed method avoids the label and derivatization steps in common methods, allows direct analysis of the samples by the naked eye without costly instruments, and is reliable, inexpensive, and sensitive.