Highly Robust, Recyclable Displacement Assay for Mercuric Ions in Aqueous Solutions and Living Cells

We designed a recyclable Hg²⁺ probe based on Rhodamine B isothiocyanate (RBITC)-poly(ethylene glycol) (PEG)-comodified gold nanoparticles (AuNPs) with excellent robustness, selectivity, and sensitivity. On the basis of a rational design, only Hg²⁺ can displace RBITC from the AuNP surfaces, resulting in a remarkable enhancement of RBITC fluorescence initially quenched by AuNPs. To maintain stability and monodispersity of AuNPs in real samples, thiol-terminated PEG was employed to bind with the remaining active sites of AuNPs. Besides, this displacement assay can be regenerated by resupplying free RBITC into the AuNPs solutions that were already used for detecting Hg²⁺. Importantly, the detection limit of this assay for Hg²⁺ (2.3 nM) was lower than the maximum limits guided by the United States Environmental Protection Agency as well as that permitted by the World Health Organization. The efficiency of this probe was demonstrated in monitoring Hg²⁺ in complex samples such as river water and living cells

A Facile, One-Step Nanocarbon Functionalization for Biomedical Applications

Despite their immense potential in biomedicine, carbon nanomaterials suffer from inefficient dispersion and biological activity in vivo. Here we utilize a single, yet multifunctional, hyaluronic acid-based biosurfactant to simultaneously disperse nanocarbons and target single-walled carbon nanotubes (SWCNTs) to CD44 receptor positive tumor cells with prompt uptake. Cellular uptake was monitored by intracellular enzyme-activated fluorescence, and localization of SWCNTs within cells was further confirmed by Raman mapping. In vivo photoacoustic, fluorescence, and positron emission tomography imaging of coated SWCNTs display high tumor targeting capability while providing long-term, fluorescence molecular imaging of targeted enzyme events. By utilizing a single biomaterial surfactant for SWCNT dispersion without additional bioconjugation, we designed a facile technique that brings nanocarbons closer to their biomedical potential