Nucleic Acids Extraction and Purification

DNA extraction has been achieved using silica beads (5 pm), which were packed in a glass microchannel and held by a sol-gel [913]. This method provided more reproducible extraction than a previous method in which extraction was performed without physically fixing the beads in microchambers [639]. 

DNA was also extracted from lysed E. coli cells using immobilized beads in a chip. The extraction efficiency was found to be high, especially when the number of E. coli cells was small [914]. 

A DNA purification chip was constructed on PDMS. The chip consisted of mixing valves and a rotary mixer with fluidic and valve actuation channels. The chip had 26 access holes, 1 waste hole, and 54 valves to simultaneously carry out three purification procedures of E. coli genomic DNA. After removing DNA from the chip, the gene that encoded the prelipin protein peptidase-dependent protein D (ppdD) was PCR-amplified externally [915]. 

Other nucleic acid extraction methods, which may have been integrated in a microsystem, will be described in subsequent sections. 

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