Nanoparticles for Signaling in Biodiagnosis and Treatment of Infectious Diseases

Colino, Clara I.; Millán, Carmen Gutiérrez; Lanao, José M.

More recently, another group has been working on an electrochemical aptasensor that uses coaxial capillary with immune magnetic nanoparticles for the separation of bacteria [54] . Streptavidin-modified magnetic nanoparticles (MNP) are injected into the coaxial capillary and are subjected to a magnetic field. Biotinylated polyclonal antibodies (PAbs) are injected to produce immune magnetic nanoparticles and a sample containing bacteria is injected into the capillary to form a MNP-PAb bacteria complex called "magnetic bacteria". Gold nanoparticles (AuNP) modified with the aptamer against the bacteria and urease are injected into the system to produce a MNP-PAb-bacteria-aptamer-GNP-urease complex called "enzymatic bacteria". Urea is injected into the capillary and then ammonium and carbonate ions are produced by the catalysis of the urea by the bacteria. This produces a reduction in the impedance that is measured by the PCB gold electrode and is related to the concentration of the bacteria. This method is very rapid and sensitive for the detection of E. coli O157:H7 ( Figure 1 ) [54] . Nanodecorated electrodes have also recently been developed for the detection of bacteria such as E. coli and Streptococcus pneumoniae [55, 56] .