A dual biomarker detection platform for quantitating circulating tumor DNA (ctDNA)

Circulating tumor DNA (ctDNA), which includes DNA mutations, epigenetic alterations and other forms of tumor-specific abnormalities, is a promising "real-time" biomarker for noninvasive cancer assessment. Tumor DNA is of great value in the process of cancer treatment, including diagnostic and prognostic information before, during treatment and at progression. Here we introduce a peptide nucleic acids probe-gold nanoparticles (PNA-AuNPs) and lead phosphate apoferritin (LPA)-based dual biomarker detection platform, which could be used in a DNA biosensor to quantify ctDNA by detection of tumor-specific mutations and methylation of PIK3CA gene. On the one hand, PNA probe and anti-5-Methylcytosine monoclonal antibody (anti-5-mC) were used to recognize the different parts of ctDNA, forming a sandwich-structure on a screen-printed electrode (SPE) surface. On the other hand, AuNPs and LPA were introduced to construct the biosensor for double signal amplification. Square-wave voltammetry (SWV) was used to monitor the electrochemical signal of lead ions released from apoferritin. The proposed DNA biosensor yielded a linear current response to ctDNA concentrations over a broad range of 50-10000 fM with a detection limit of 10 fM. It also successfully detected ctDNA collected from cancer patient serum. Therefore, we anticipate this new platform opens up an approach to detect and monitor diverse malignancies, facilitating personalized cancer therapy.