Routes to Potentially Safer T1 Magnetic Resonance Imaging Contrast in a Compact Plasmonic Nanoparticle with Enhanced Fluorescence.

Engineering a compact, near-infrared plasmonic nanostructure with integrated image-enhancing agents for combined imaging and therapy is an important nanomedical challenge. Recently, we showed that Au@SiO2@Au nanomatryoshkas (NM) are a highly promising nanostructure for hosting either T1 MRI or fluorescent contrast agents with a photothermal therapeutic response in a compact geometry. Here, we show that a near-infrared-resonant NM can provide simultaneous contrast enhancement for both T1 magnetic resonance imaging (MRI) and fluorescence optical imaging (FOI) by encapsulating both types of contrast agents in the internal silica layer between the Au core and shell. We also show that this method of T1 enhancement is even more effective for Fe(III), a potentially safer contrast agent compared to Gd(III). Fe-NM-based contrast agents are found to have relaxivities 2× greater than those found in the widely used gadolinium chelate, Gd(III) DOTA, providing a practical alternative that would eliminate Gd(III) patient exposure entirely. This dual-modality nanostructure can enable not only tissue visualization with MRI but also fluorescence-based nanoparticle tracking for quantifying nanoparticle distributions in vivo, in addition to a near-infrared photothermal therapeutic response.

Aluminum Nanocrystals: A Sustainable Substrate for Quantitative SERS-Based DNA Detection.

Since its discovery in the 1970s, surface-enhanced Raman scattering (SERS) has been primarily associated with substrates composed of nanostructured noble metals. Here we investigate chemically synthesized nanocrystal aggregates of aluminum, an inexpensive, highly abundant, and sustainable metal, as SERS substrates. Al nanocrystal aggregates are capable of substantial near-infrared SERS enhancements, similar to Au nanoparticles. The intrinsic nanoscale surface oxide of Al nanocrystals supports molecule-substrate interactions that differ dramatically from noble metal substrates. The preferential affinity of the single-stranded DNA (ssDNA) phosphate backbone for the Al oxide surface preserves both the spectral features and nucleic acid cross sections relative to conventional Raman spectroscopy, enabling quantitative ssDNA detection and analysis.