Enhanced electrochemiluminescence biosensing of gene-specific methylation in thyroid cancer patients' plasma based integrated graphitic carbon nitride-encapsulated metal-organic framework nanozyme optimized by central composite design

Circulating cell free DNA (cfDNA) methylation is a novel type of cancer biomarker, but its minuscule proportion of total DNA makes proper analysis difficult in clinical samples. Herein, a sensitive electrochemiluminescence immuno-DNA sensor was designed to analyze DNA methylation using sandwiching the target methylated DNA between the magnetic nanoparticles/anti-5-methylcytosine monoclonal antibody (MNPs/anti-5mc) bioconjugate and luminol-loaded within phosphorylated DNA capture probe-immobilized C 3 N 4 NS@UiO-66 core@shell nanozyme. Taking advantages of increased concentration of C 3 N 4 NS nanozymes' • OH-generation, nanoproximity effect of C 3 N 4 NS and luminol, high density coordination of capture probe on the UiO-66 metal organic framework (MOF), MNPs' function in improving the signal-to-background ratio (S/B) in complicated plasma media, and remarkable electrocatalytic activity of reduced graphene oxide-modified pencil graphite electrode (rGO/PGE), multiple signal amplification was achieved without bisulfite and PCR amplification. The immuno-DNA sensor offers a linear response across a wide dynamic range from 20 pg to 20 ng, with a detection limit of 10 pg, when optimized by a face-centered central composite design (FCCD). Our method can differentiate methylation levels as low as 0.1%. Tumor-specific methylation DNA is definitely identified in the plasma of 9 of 10 thyroid cancer patients' plasma. The 91% clinical sensitivity implies strong clinical diagnosis consistency. The suggested method was successfully utilized to evaluate methylated DNA in human blood plasma, demonstrating the platform's potential for disease diagnostics and biochemistry research. • Multi-signal amplification electrochemiluminescence approach for sensitive detection of 5-methylcytosine in the RASSF1A promoter region has been introduced. • A rational design of artificial enzyme mimics of C 3 N 4 NS@/UiO-66 core@shell has been introduced to detect DNA methylation. • High peroxidase-like catalytic activity of C 3 N 4 NS core as well as functionalizing UiO-66 surface with oligonucleotides at high density opens a new horizon for high sensitive DNA methylation. • Tumor-specific methylation DNA is definitely identified in the plasma of 9 of 10, 91% clinical sensitivity, thyroid cancer patients' plasma. • The immuno-DNA sensor offers a linear response across a wide dynamic range from 20 pg to 20 ng, with a detection limit of 10 pg.