A Rhodamine-based fluorescent sensor for chromium ions and its application in bioimaging

A rhodamine-based sensor（1） has been developed for the detection of chromium ions.Cr-（3＋）-induced opening of the rhodamine spirocycle in sensor（1） led to the distinct colorimetric and fluorescence responses.Among all the tested ions,only Cr-（3＋） generated a significant fluorescence enhancement of up to13-fold,which indicated the high selectivity of 1.Sensor（1） was successfully applied in the in vivo fluorescence imaging of Cr-（3＋） in C.elegans.The results provided solid evidences for the future estimation of Cr-（3＋） in environmental applications and tobacco samples.

Molecular imaging of enzyme activity in vivo using activatable probes

Precise measurement of enzyme activity in living systems with molecular imaging probes is becoming an important technique to unravel the functional roles of different enzymes in biological processes. Recent progress has been made in the development of a myriad of molecular imaging probes featuring different imaging modalities, including optical imaging, magnetic resonance imaging, nuclear imaging, and photoacoustic imaging, allowing for non-invasive detection of various enzyme activities in vivo with high sensitivity and high spatial resolution. Among these imaging probes, activatable or ＂smart＂ probes, whose imaging signal can be specifically switched from the ＂off＂ to ＂on＂ state upon interaction with a target enzyme, are particularly attractive due to their improved sensitivity and specificity. Here, recent advances in the development of activatable probes capable of imaging different enzyme activities in vivo are summarized based on different imaging modalities, and current challenges and future perspectives are discussed.

Theranostic gold cluster nanoassembly for simultaneous enhanced cancer imaging and photodynamic therapy

As one of near-infrared（NIR） fluorescent（FL） nanoprobes, gold nanoclusters（Au NCs） are delicated to passive-targeting tumors for NIR FL imaging, but which easily cleared by the kidneys for the small size（〈1.5 nm）. Herein, the well-defined gold clusters nanoassembly（Au CNA） was synthesized by the selfassembly of Au NCs based on protein cross-linking approach. The as-prepared Au CNA demonstrated highly effective cellular uptake and precise tumor targeting compared to that of Au NCs. Moreover, with the irradiation of 660 nm laser, Au CNA generated largely reactive oxygen species（ROS） for photodynamic therapy（PDT）. In vitro and [39TD$IF]in vivo PDT revealed that Au CNA exhibited largely cell death and significantly tumor removal at a low power density of 0.2 W/cm^2. It could be speculated that the laser-excited Au CNA produced photon energy, which further obtained electron from oxygen to generate radical species.Therefore, Au CNA as a photosensitizer could realize NIR FL imaging and NIR laser induced PDT.

A Cascade Targeted and Activatable NIR-ⅡNanoprobe for Highly Sensitive Detection of Acute Myeloid Leukemia in an Orthotopic Model

Acute myeloid leukemia(AML)remains a significant concern in modern medicine.Early diagnosis is the key to improving the therapeutic effects of AML.In the present work,a cascade-targeted and activatable NIR-Ⅱ nanoprobe(Ald&A1094@Ag_(2)S)was developed for early detection of AML in an orthotopic model.Upon intravenous injection,Ald&A1094@Ag_(2)S effectively accumulated in bone tissue due to its high affinity for alendronate(Ald)to the bone.Thereafter,the AML microenvironment allowed for the membrane-penetrating peptide TAT(cell‐penetrating peptide(CGRRRQRRKKRG))to be exposed via pH-sensitive hydrazone bond-mediated detaching of bone-targeted ligands,resulting in efficient internalization of nanoprobes in HL60 cells.Endogenous peroxynitrite(ONOO–)in HL60 cells further activated NIR-Ⅱ fluorescence of Ag_(2)S QDs via A1094 oxidation,thereby inhibiting fluorescence resonance energy transfer(FRET).Such a unique cascade-targeted and activatable strategy enables the nanoprobes to only light up the AML lesion region in the bone marrow with negligible background effects,which holds great potential for clinical applications in the future.