Energy-Absorbing and Local Plasmonic Nanodiamond/Gold Nanocomposites for Sustained and Enhanced Photoacoustic Imaging

Photoacoustic (PA) imaging is a laser-mediated optical ultrasound-based visualization that allows imaging of optical energy absorbers in deep tissue, offering higher spatial resolution, compared with that of NIR fluorescence. To enhance a gold nanoparticles-based PA agent, carbon crystalline nanodiamonds and gold nanocomposites (NDAuNPs) were synthesized by chemical reduction of a carboxylate nanodiamond and gold precursor. Reduced hydroxyl-terminated nanodiamonds have stable colloidal dispersion and provide a platform where AuNPs are localized on the ND surface with high density. NDAuNP agglutinates were 100 nm in size, and AuNPs with a size distribution of 5–20 nm were chemically conjugated on the ND surface. The surface-enhanced Raman scattering spectra showed enhanced intensity of NDAuNPs in a concentration-dependent manner. Energy-absorbing nanodiamonds facilitated energy transfer into AuNPs, inducing a local plasmonic effect. The PA signal of NDAuNPs was stronger than that of the AuNPs, as well as t...