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The isolation of nucleic acids (NA) is the preliminary step to carry out genetic studies and DNA biosensor development. The presence of inhibitors in the purified NA interferes with the downstream application. These salts and other organic contaminations particularly challenge the analytical sensitivity of DNA biosensors. The detailed study was carried out to optimize the factors which might affect viral nucleic acid purification. The results suggested that 6 M guanidinium hydrochloride salt concentration was critical for NA isolation. The inverse relation has been found in the pH of the lysis buffer and quality and quantity of NA. The NA yield was relatively stable at pH 4–5. It has been observed that the use of carrier RNA was indispensable for viral genome isolation. The addition of ethanol to lysate in 1:1 ratio greatly improved NA recovery. The elution efficiency of DNase and RNase free water, 1× TE buffer and 1× PCR buffer was compared. The carrier RNA was best eluted in DNase and RNase free water and 1× TE buffer. It was further demonstrated that this method can be automatized for high throughput detection. A simple experiment was conducted to optimize the different parameters of an automated NA extractor to simultaneously extract HBV DNA and HCV RNA. The purified NA was successfully amplified in PCR and RT-PCR to verify the reliability of the established protocol. Thus a semi-automated system for the simultaneous detection of multiple viruses has been demonstrated.

With the help of Fe3O4 nagnetic nanoparticles as a solid carrier and an excellent tool for separation, six SNP loci (rs2279115 of BCL2 gene, rs804270 of NEIL2 gene, rs909253 of LTA gene, rs2294008 of PSCA gene, rs3765524 and rs10509670 of PLCE1 gene) were selected to evaluate their relation to gastric cancer risk. Using two kinds of functionalized magnetic nanoparticles and universal tagged arrays, the whole operation procedure including genome DNA extraction and SNP genotyping was performed. All genotypes and allele frequencies were calculated in the cases and controls respectively to analyze their association with gastric cancer risk. Totally 200 pathological samples and 134 normal control subjects were collected. The results demonstrated that four SNP loci (rs2279115, rs804270, rs909253 and rs3765524) showed a potential association with gastric cancer risk, and the other two (rs2294008, rs10509670) possessed no difference/association among cases and controls.