Stepwise-Enhanced Tumor Targeting of Near-Infrared Emissive Au Nanoclusters with High Quantum Yields and Long-Term Stability

Abstract

We developed an in situ coordination-driven spatially confined strategy for preparing near-infrared emissive gold nanoclusters encapsulated by fluorinated polymers (AuNCs@PF, λmax = 810 nm) with good stability and high quantum yields (27.7%), far higher than those previously reported for NIR AuNCs (>800 nm). Based on the stepwise enhancements including long blood circulation-induced passive tumor targeting, fluoro-enhanced tumor permeation, and tumor microenvironment (weak acid)-induced aggregation retention in cells, these AuNCs demonstrated bright and stable NIR fluorescence imaging ability in tumors. Additionally, the AuNCs@PF were capable of fluorine magnetic resonance imaging and computed tomographic imaging. The multimodal imaging of tumor-bearing mice clearly implied the potential of AuNCs@PF in biomedical fields.

Tunable Nanomaterials of Intracellular Crystallization for In Situ Biolabeling and Biomedical Imaging

“…Compared with fluorescent organic small molecules, nanomaterials have unique advantages, such as full-spectrum fluorescence emission and excitation, and can realize near-infrared two-zone fluorescence. − They have a long Stokes shift and a narrow half-peak width of fluorescence emission, which is difficult for small fluorescent organic molecules to achieve. The fluorescence effect is consistent with the luminescence mechanism of Jablonski diagram. , Fluorescent nanomaterials are excited from the ground state (S0) to the excited state (S1) after energy absorption under the appropriate excitation light, and then return from S1 to S0 through radiation relaxation to produce fluorescent luminescence. ,− Or phosphorescence can be generated through intersystem crossing. , At present, the research focus of fluorescent nanomaterials is some quantum dots or nanoclusters, such as carbon quantum dots, rare earth quantum dots, gold nanoclusters, etc. ,,, The emergence of biosynthesized fluorescent nanomaterials provides a new research direction for chemical biomedical imaging, which can effectively improve the shortcomings of chemical synthesized nanomaterials, such as biocompatibility.…”

“…Chemical biomedical imaging is a new field that applies optical technology to biomedical science. , Among them, optical probes are developed by chemical means, such as fluorescent (FL) probes, surface-enhanced Raman scattering (SERS) probes, nuclear magnetic resonance contrast agents (MRI), computed tomography (CT) contrast agents, and photoacoustic imaging (PAI) contrast agents. − The noninvasive study of physiological and pathological processes is realized by functionalizing the probe or contrast agent. , Different types of probes have different design rules and structures for different research or applications. A large number of fluorescent biological probes have been developed to be used for protein labeling and tracing.…”

Luminescent Gold Nanoclusters for Bioimaging: Increasing the Ligand Complexity

“…Another study by Zhu. et al described an NIR-emitting nanostructure based on Ag(I)-doped GSH-AuNCs encapsulated with fluorinated polymer (PF) with a high quantum yield as a multimodal nanoprobe for in vitro and in vivo imaging [ 120 ]. GSH-AuNCs were mineralized inside cysteamine-grafted poly(ethylene-alt-malic anhydride) functionalized with 2,2,2-trifluoroethylamine as a template agent.…”

Metal Nanoclusters in Point-of-Care Sensing and Biosensing Applications

“…For example, GSH-capped AuNCs embedded by fluorinated polymers (AuNCs@PF) result in a synergetic material with NIR emission at 810 nm. An acid-triggered aggregation brought enhanced PL in tumor cells . On the other hand, the NIR-II region holds great promise in high-reolution and deep tissue penetration studies for biomedical diagnostics .…”