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Contrast agents for magnetic resonance imaging (MRI) improve anatomical visualizations. However, owing to poor image resolution in whole-body MRI, resolving fine structures is challenging. Here, we report that a nanoparticle with a polysaccharide supramolecular core and a shell of amorphous-like hydrous ferric oxide generating strong T1 MRI contrast (with a relaxivity coefficient ratio of ~1.2) facilitates the imaging, at resolutions of the order of a few hundred micrometres, of cerebral, coronary and peripheral microvessels in rodents and of lower-extremity vessels in rabbits. The nanoparticle can be synthesized at room temperature in aqueous solution and in the absence of surfactants, has blood circulation and renal clearance profiles that prevent opsonization, and leads to better imaging performance than Dotarem (gadoterate meglumine), a clinically approved gadolinium-based MRI contrast agent. The nanoparticle's biocompatibility and imaging performance may prove advantageous in a broad range of preclinical and clinical applications of MRI.

The current gold standard for COVID-19 confirmation is RT-PCR, which possesses high sensitivity and specificity, but a long turnaround time has been a drawback. Here, we introduce a nanoPCR platform that can yield breakthroughs in RT-PCR speed and decentralize the diagnostic testing. A key innovation is to exploit magneto-plasmonic nanoparticles for dual purposes: fast thermocycling through plasmonic heating and enhanced signal detection via magnetic fluorescence switch. We further integrated these functionalities into a portable system to streamline point-of-care (POC) COVID-19 diagnostics with a “one-step-finish” approach from sampling to result. When applied with clinical COVID-19 samples, nanoPCR achieved an analytical performance of sensitivity and specificity comparable to that of a benchtop instrument but completed the entire detection within 18 minutes (vs. 2.5 hours for regular RT-PCR), which makes it ideal for rapid POC diagnostics. This platform technology is readily scalable for higher throughput and expandable to other disease targets, promising broader impacts in on-site molecular testing.

Contrast agents for magnetic resonance imaging (MRI) improve anatomical visualizations. However, owing to poor image resolution in whole-body MRI, resolving fine structures is challenging. Here, we report that a nanoparticle with a polysaccharide supramolecular core and a shell of amorphous-like hydrous ferric oxide generating strong T