Modified methylated DNA immunoprecipitation protocol for noninvasive prenatal diagnosis of Down syndrome

Methylated DNA immunoprecipitation real-time quantitative polymerase chain reaction (MeDIP-real-time qPCR) has been introduced as noninvasive prenatal test that has shown absolute detection rate in the screening of Down syndrome. Herein, we aimed to propose a novel modification of MeDIP-qPCR and assess its potential to alleviate the overall cost of the test, being used in very early weeks of pregnancy, and develop it to a noninvasive prenatal diagnosis biosensor in future researches.

Cell-free fetal DNA (cffDNA) isolated from 60 pregnant women, including 29 normal and 31 trisomy 21 pregnancies, were analyzed using proposed MeDIP protocol. Enriched methylated DNA sequences were amplified through real-time qPCR using eight fetal-specific primer pairs. The status of samples was determined through the calculation of D-value with the cutoff point of zero.

The sensitivity and specificity of the MeDIP protocols using nanoparticles were 100% and 100%, respectively.

Remarkable decrease in the price of MeDIP test per each patient would be a reasonable factor to confirm it on larger sample size. Moreover, the high detection rate of screening and the availability of the required instruments around the world make satisfactory reasons to be tested in earlier weeks of pregnancy, thanks to the high sensitivity of gold shell nanoparticles.