Bio-barcode DNA assay amplification and detection
Fig. 3A is a schematic showing the multiple bio-barcode assay.
After immobilization of oligonucleotides on the surface of nanoparticles,
both nanoparticles bind to the tDNA to form a sandwich
structure as a result of the specificity of pDNA. Before hybridization,
two bio-barcoded AuNPs were mixed in a 1:1 ratio. One was
PbS-AuNP-bDNA-1pDNA which recognizes the pagA gene from B.
anthracis, and the other was CdS-AuNP-bDNA-1pDNA which recognizes
the Iel gene of S. enteritidis. Then two 2pDNA coated MNPs
were mixed in a 1:1 ratio also. One was specific to pagA gene from
B. anthracis and the other was specific to Iel gene of S. enteritidis.
When the tDNA samples hybridize with the pDNA on the MNPs, a
MNP-2pDNA/tDNA complex (middle picture) is formed. Then the
1pDNA-AuNP-bDNA-NTs complex is added to form a sandwich
structure consisting of MNP-2pDNA/tDNA/1pDNA-AuNP-bDNANTs.
After hybridization is complete, the NTs on the bDNA are
released in 1Mnitric acid and the NT ions are measured by SWASV
on the SPCE chip. Fig. 3B shows SWASV measurements performed
with an in situ deposition of bismuth film and target metals (Pb
and Cd) in the presence of dissolved oxygen using a potentiostat/
galvanostat.