Current Progress in Aptasensors for Heavy Metal Ions Based on Photoelectrochemical Method: A Review

Background: Heavy metal contamination in natural environment is a serious problem due to increasing industrial activities. Since heavy metal ions are non-biodegradable, they are considered as a serious source to pollute the biosphere throughout the world and cause many healthy and physiological diseases. Therefore, it is imperative to develop simple, sensitive and selective methods for their detection. Methods: This review is based on SCI full-text database, with Web of Science and Google as search tools, using "Photoelectrochemical (PEC)" and "Metal ions" as the theme of the search keywords, selecting the papers published in 2009-2016. Results: It can be seen that a number of PEC sensors for heavy metal ions show an overall increasing trend of this research.The PEC sensors without DNA/DNAzymes were developed relatively earlier, and more related papers were published. The proportions of PEC sensors for Cu2+, Hg2+ and Cr (VI) on the total PEC sensor research for heavy metal ions in research papers are 52.63%, 21.05% and 10.53%, respectively. However, the field of metal ions detection research focused on PEC biosensor in recent years. The proportions of PEC biosensors for Pb2+ and Hg2+ are 46.67% and 40%, respectively. Therefore, the PEC detection of heavy metal ions currently focuses on using DNA/DNAzymes. Conclusion: This paper summarized the mechanisms of PEC biosensors which were developed for heavy metal ions in recent years. In addition, this paper highlights the immobilization and sensing strategies of biosensors with DNAzymes/DNA molecules. The challenges and future directions are also discussed. Keywords: Heavy metal ions, DNAzymes, DNA molecules, PEC aptasensors, physiological diseases, photoelectrochemical method.