We demonstrate the utility of the opto-fluidic ring resonator (OFRR) sensor for analyzing methylated oligonucleotides. Cytosine methylation, a regular epigenetic function in cellular growth and metabolism, may have ties to abnormal suppression of key genes involved with cellular proliferation. Such behavior is suspected to be strongly related to the occurrence of several types of cancers. The OFRR is demonstrated as a tool both for detecting DNA hybridization and methylated cytosines residues.