Polymerase chain reaction/ligase detection reaction/hybridization assays using flow-through microfluidic devices for the detection of low-abundant DNA point mutations.
We have microfabricated a flow-through biochip for the analysis of single base mutations in genomic DNA using two different materials: (1) a polycarbonate (PC) chip for performing a primary polymerase chain reaction (PCR) followed by an allele-specific ligation detection reaction (LDR) and (2) a poly(methyl methacrylate) (PMMA) chip for the detection of the LDR products using a universal array platform. The operation of the device was demonstrated by detecting low-abundant DNA mutations in gene fragments (K-ras) that carry point mutations with high diagnostic value for colorectal cancers. The PC microchip was used for sequential PCR/LDR in a continuous-flow format, in which the following three steps were carried out: (1) exponential amplification of gene fragments from genomic DNA; (2) mixing of the resultant PCR product with a LDR mixture via a Y-shaped passive micromixer and (3) ligation of two primers only when the particular mutation was present in the genomic DNA. A PMMA chip was employed as the microarray device, where zip code sequences (24-mer), which were complementary to sequences present on the discriminating primer, were micro-printed into fluidic channels embossed into the PMMA substrate. We successfully demonstrate the ability to detect one mutant DNA in 80 normal sequences with the integrated microfluidic device. The PCR/LDR/hybridization assay using the microchips performed the entire assay at a relatively fast processing speed: 18.7 min for PCR, 8.1 min for LDR, 5 min for hybridization, 10 min for washing and 2.6 min for fluorescence scanning (total processing time=ca. 50 min) with an order of magnitude reduction in reagents compared to bench-top formats.
Center for Bio-modular Multi-scale Systems, and Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA.
Masahiko
M
Hashimoto
Francis
F
Barany
Steven A
SA
Soper
D000818:Animals; D015374:Biosensing Techniques; D011088:DNA Ligases / Q000737:chemistry / Q000235:genetics; D004273:DNA, Neoplasm / Q000032:analysis* / Q000737:chemistry / Q000235:genetics*; D006801:Humans; D044085:Microfluidics; D009693:Nucleic Acid Hybridization; D017354:Point Mutation; D016133:Polymerase Chain Reaction
D004273:DNA, Neoplasm; D011088:DNA Ligases