Double recognition of oligonucleotide and protein in the detection of DNA methylation with surface plasmon resonance biosensors.

DNA methylation plays an essential role in maintenance of cellular function. A growing number of human diseases have been found to be associated with aberrant DNA methylation, especially cancer. However, current technologies used in DNA methylation detection are complicated and time consuming. A promotor of the Adenomatous polyposis coli (APC) gene, a well-studied tumor suppressor gene, was used as the detection target DNA sequence. The double recognition mechanism was realized with oligonucleotide probe hybridization and specific protein binding. First, complementary target DNA was captured by the probe immobilized onto a surface plasmon resonance (SPR) sensor chip. Then, the recombinant methyl-CpG binding domain (MBD) protein was passed over the surface to recognize and bind to methylated CpG sites. Binding resulted in an increase in the refractive index, and a detectable optical signal was generated. Five picomoles of methylated APC promotor DNA could be easily detected with this method. The entire detection could be completed within 1h. This work represents the first SPR based biosensor technology, which achieves simple and specific DNA methylation detection and avoids complicated bisulfite treatment and methylation-sensitive restriction digestion. It will improve our ability to detect DNA methylation specifically and rapidly, and promote our understanding of the role of DNA methylation in gene regulation and diseases.