Tissue Engineering And Nanotheranostics

“9.61x6.69” b2815 Tissue Engineering and Nanotheranostics

Plasmonic Nanoparticles Application in Biosensor and Bioimaging 171

occurring on the surface of AuNPs bring electron injection into the

nanoparticles and change their local environment. This change sur­

rounding nanoparticles result in a shift in DF spectra, which can be

obviously monitored by DFM at the single molecular level. As spectra

shift caused by catalytic reactions is small and hardly observed by other

technologies, such as UV, AFM, TEM and microscopy, a serial of

novel nanosensors system­based DFM has been invented to investigate

and monitor catalysis reactions.^116 Fan et al. proposed to apply red­

shift in DFM by enlargement of AuNPs to sensor catalytic reac­

tion.117,118 They discovered that AuNPs with 50 nm size, acting like

glucose oxidation (GOX), produces H 2 O 2 , which, in turn, induces the

AuNP’ seeded growth in situ in the presence of HAuCl 4. They dem­

onstrated that the surface of AuNPs prefer to adsorb singlestranded

(ss ) DNA than doublestranded (ds ) DNA due to nitrogen containing

nucleotides. For example, addition of growing solution (H 2 O 2 and

HAuCl 4 ) leads to a 100 nm red­shift of scattering peak for bare AuNPs

(Fig. 3(a)). The ss­DNA and the ds­DNA suppressed the catalytic

activity of AuNPs and, in turn, their growth in varying degrees by

adsorbing on its surface. Especially, the scattering profile of nanopar­

ticle exhibited almost identical in the presence of ss­DNA with bare

nanoparticle. Therefore, the conclusions that the adsorption ss­DNA

on the surface of AuNPs inhibits their GOX­like catalytic activity and

finally inhibits AuNPs’ further growth were obtained.^117 With this sen­

sor based on DFM, they not only monitor the mechanism of AuNPs

growth but also propose a novel method for regulating the GOX­like

catalytic activity of AuNPs with the help of DNA nanotechnology.^118

Furthermore, this nanosensor system of AuNP­catalyzed GOX

was extended to detect biomolecules, such as adenosine triphosphate

(ATP).^118 Similar to the mechanism mentioned above, an anti­ATP

aptamer physically covers the surface of AuNPs and inhibits its cata­

lytic activity. In the presence of ATP, the aptamer forms tertiary struc­

ture, resulting in it detaching from the surface of AuNPs. Therefore,

AuNPs’ catalytic activity recovers and the AuNPs start to grow in the

presence of a growing solution, resulting in a visible red­shift in scat­

tering spectra. Experiments indicate that this ATP aptamer­based

plasmonic nanoparticle sensor has a detection limit of nM. This system

holds great promise for real­time imaging of multiple targets by using