The Centers for Disease Control and Prevention reports that Down syndrome is one of the most common birth defects, with one affected case observed in every 700 births. However, conventional non-invasive prenatal tests for the condition are not just unreliable but are also risky for the mother and the fetus.
Currently, scientists have created a new sensitive biosensor that could be eventually used to detect fetal Down syndrome DNA in the blood of pregnant women. The outcomes of the study have been reported in the ACS journal Nano Letters.
Down syndrome is characterized by varying degrees of developmental and intellectual difficulties and is known to be caused by the presence of an additional copy of chromosome 21. Although it is possible to screen for the condition in pregnant women by means of indirect blood biomarker tests or ultrasound scans, misdiagnosis rates are high.
Amniocentesis, which involves the insertion of a needle into the uterus to gather amniotic fluid by the doctor, offers a definitive diagnosis; however, the procedure is risky to both the pregnant woman and the fetus. Although whole-genome sequencing, an emerging technique, is highly accurate, it is a slow and high-cost process. Zhiyong Zhang and team intended to devise a rapid, cost-effective, and sensitive test that could detect increased DNA concentrations of chromosome 21 DNA in the blood of pregnant women.
Field-effect transistor biosensor chips developed on a single molybdenum disulfide layer were used by the researchers. Gold nanoparticles were attached to the surface. Probe DNA sequences with the ability to recognize a particular sequence from chromosome 21 were immobilized on the nanoparticles. Upon adding chromosome 21 DNA fragments to the sensor, they attached to the probes, leading to a decrease in the electrical current of the device.
The biosensor was able to detect DNA concentrations as low as 0.1 fM/L, which is considerably more sensitive compared to other reported field-effect transistor DNA sensors. According to the researchers, some day, the test could be employed to compare chromosome 21 DNA levels in the blood with that of another chromosome, such as 13, to establish whether there are additional copies, indicating a fetus is affected by Down syndrome.
The study has been funded by the National Key Research & Development Program, the National Natural Science Foundation of China, and the Beijing Municipal Science and Technology Commission.