ABSTRACT
ObjectiveThe traditional detection method of recombinase polymerase amplificaton (RPA) is not suitable for rapid field detection due to the complicated operation and other factors. Taking the detection of hepatitis b virus (HBV) nucleic acid as an example, it established a detection method of HBV nucleic acid isothermal amplification based on recombinase polymerase amplificaton (RPA) and designed a matching visual detection device of RPA product.MethodsFirstly, a RPA product detection device was designed, which can be used to collect images by taking photos of mobile phones and visually interpret the detection results. Secondly, RPA primers and probes were designed according to the design of HBV gene conserved sequence. Amplification efficiency of each primer pairs were compared though monitoring the RPA reaction of real-time fluorescence curve to screen the best primers and optimize the optimal reaction conditions. Visual detection sensitivity was investigated by using artificial synthesis of HBV target plasmid, and was investigated the specificity of the method by the detection of synthetic plasmid containing hepatitis c virus (HCV), human immunodeficiency virus, treponema pallidum, influenza virus, human papilloma virus DNA fragment. Thirdly, the feasibility of RPA product visualization detection device was verified by comparing with the real-time fluorescence amplification curve. Finally, RPA visual detection was performed on 20 serum DNA samples detected by real-time fluorescence PCR to evaluate the applicability of this method to the detection of actual clinical samples.ResultsThe visual detection device of RPA product was used to realize the negative and positive signals that could be detected by mobile phone photography and visual observation. The visual detection method of HBV nucleic acid RPA amplification could realize the visual detection of DNA targets as low as 1-10 copies of HBV within 30 min at 39 ℃ and had good specificity. The test results of 20 serum DNA samples were completely consistent with those of the commercially available qPCR kit, which preliminarily verified the practicability of the method and the device.ConclusionCombined the established HBV-RPA amplification system with the RPA product visualized detection device, it would be expected to develop a low-cost rapid visualization screening technology platform for HBV nucleic acid in blood.
ABSTRACT
Preimplantation genetic diagnosis (PGD) was developed to play a supporting role in assisted reproductive technology. With this kind of detection method, embryos with copy number variations, chromosome translocations or single mutations were excluded and the normal embryos were chosen and implanted. Theoretically, the application of these procedures could improve the implantation and pregnancy rate and help to delivery healthy offspring. PGD was considered to be more precise, higher specific and non-invasive with the appearance of microarray hybridization technology, the next generation sequencing and time-lapse monitoring technology. This paper presented a review of new Methods used in PGD, including fluorescence in situ hybridization, array comparative genomic hybridization, SNP array, next generation sequencing, MicroSeq-PGD, MaReCs, time-lapse monitoring and cfDNA-based method, and their advantages and disadvantages as well as efficacy in the procedures in which they are used.
ABSTRACT
<p><b>OBJECTIVE</b>To establish a method to detect Down's syndrome through quantitative pyrosequencing of the heterozygous single nucleotide polymorphisms (SNPs) on the chromosome 21.</p><p><b>METHODS</b>An improved allele-specific-amplification was used to screen heterozygous SNPs on the chromosome 21 from 84 normal samples. Pyrosequencing was used to quantitatively determine the ratio between the two alleles of a heterozygote, and the diagnosis of Down's syndrome was thus carried out based on the ratio.</p><p><b>RESULTS</b>By genotyping 84 genomic DNA samples from normal Chinese population, 6 SNPs with a relatively high level of heterozygosity were screened out. Heterozygote coverage of 92.9% was achieved by using a panel of 6 SNPs on the chromosome 21. Ten clinical samples from Down's syndrome patients were quantitatively determined by pyrosequencing, and 9 samples were accurately diagnosed by comparing the ratio of the two alleles. The pyrosequencing results showed that the ratio of the two alleles were 2:1 or 1:2 for the Down's syndrome patients.</p><p><b>CONCLUSION</b>The method has the advantage of a low cost, simple process, and time-saving operation and could be potentially applicable to the rapid diagnosis of Down's syndrome.</p>
Subject(s)
Female , Humans , Pregnancy , Alleles , Asian People , Genetics , Chromosomes, Human, Pair 21 , Cloning, Molecular , DNA , Down Syndrome , Diagnosis , Genetics , Genetic Testing , Karyotyping , Methods , Polymorphism, Single Nucleotide , Genetics , Prenatal Diagnosis , Economics , MethodsABSTRACT
ATP sulfurylase (ATPS,EC 2.7.7.4) reversibly catalyzes the reaction between ATP and sulfate to produce APS and pyrophosphate (PPi), and has been used in pyrosequencing. The gene coding ATP sulfurylase was amplified from the genomic DNA of Saccharomyces cerevisias (CICC 1202), and cloned into prokaryotic expression plasmid pET28a( + ) to provide a recombinant expression plasmid pET28a( + )-ATPS. Upon IPTG induction, ATP sulfurylase was produced by E. coli BL21 (DE3) harboring the recombinant expression plasmid pET28a( + )-ATPS. The relative molecular weight of recombinant ATP sulfurylase with His tag was about 60 kD. The recombinant ATP sulfurylase with electrophoretic pure grade was obtained only by two purification steps: His * Bind Resin affinity chromatography and ultrafiltration. The specific activity of the purified recombinant ATP sulfurylase was as high as 5.1 x 10(4) u/mg. The successful application of the enzyme in pyrosequencing was also demostrated.