PEMC-based method of measuring DNA hybridization at femtomolar concentration directly in human serum and in the presence of copious noncomplementary strands.
Piezoelectric-excited, millimeter-sized cantilever (PEMC) sensors having high-mode resonance near 1 MHz are shown to exhibit mass change sensitivity of 1-300 ag/Hz. Gold-coated PEMC sensors immobilized with 15-mer single-stranded DNA (ssDNA) were exposed to 10-mer complementary strands at concentrations of 1 fM, 1 pM, and 1 microM, both separately and sequentially at 0.6 mL/min in a sample flow cell housing the sensor. Decrease in resonance frequency occurred as complementary strands hybridized to the immobilized probe DNA on the sensor surface. Hybridization in three background matrixes--buffer, buffer containing 10,000 times higher noncomplementary strands, and 50% human plasma--were successfully tested. Sensor hybridization responses to 1 fM, 1 pM, and 1 microM complementary strand were nearly the same in magnitude in all three matrixes, but the hybridization rates were different. In each case, the sensor detected the presence of 2 amol of complementary 10-mer strand. The extent of hybridization calculated from resonance frequency change did not decrease in serum. The findings suggest ssDNA can be detected at 2 amol without a sample preparation step and without the use of labeled reagents.
Rijal
Kishan
K
Department of Chemical and Biological Engineering, Drexel University, 32nd and Chestnut Streets, Philadelphia, Pennsylvania 19104, USA.
Mutharasan
Raj
R
D001483:Base Sequence; D015374:Biosensing Techniques; D004247:DNA / Q000097:blood / Q000737:chemistry*; D006801:Humans; D007700:Kinetics; D009693:Nucleic Acid Hybridization; D015345:Oligonucleotide Probes; D012680:Sensitivity and Specificity
D015345:Oligonucleotide Probes; D004247:DNA