Redox-Gated Optical Modulation of Coumarin-Triphenyliminophosphorane Fluorophores

Novel coumarin-triphenyliminophosphorane (TPIPP) fluorophores, synthesized via a nonhydrolytic Staudinger reaction, exhibit remarkable redox-responsive optical properties. Upon chemical and electrochemical oxidation, these compounds display a hypsochromic shift in absorption from 430 to 350 nm, accompanied by up to 11-fold fluorescence enhancement under 405 nm excitation. The fluorescence switching occurs at an electrochemical oxidation potential of approximately +2.0 V. This enhanced one-photon excited fluorescence is attributed to an emissive radical effect, stemming from in situ generated radical cations at the polarizable iminophosphorane (P=N) bond. The radical formation was confirmed by trapping experiments using tetracyanoquinodimethane, which produced characteristic absorption of radical anions around 850 nm, and by electron spin resonance studies using 5,5-dimethyl-1-pyrroline N-oxide as a spin trap. Conversely, two-photon excited fluorescence under 800 nm pulsed laser excitation decreases upon oxidation, likely due to reduced two-photon absorption resulting from altered π-conjugation. This work demonstrates that external redox modulation can induce significant changes in absorption profiles and enable switching between enhanced one-photon and diminished two-photon excited fluorescence, highlighting the potential of leveraging the controllable radical character of the P=N bond in designing redox-responsive fluorophores.

Polymeric Dendrimers as Nanocarrier Vectors for Neurotheranostics

Dendrimers are polymers with well-defined 3D branched structures that are vastly utilized in various neurotheranostics and biomedical applications, particularly as nanocarrier vectors. Imaging agents can be loaded into dendrimers to improve the accuracy of diagnostic imaging processes. Likewise, combining pharmaceutical agents and anticancer drugs with dendrimers can enhance their solubility, biocompatibility, and efficiency. Practically, by modifying ligands on the surface of dendrimers, effective therapeutic and diagnostic platforms can be constructed and implemented for targeted delivery. Dendrimer-based nanocarriers also show great potential in gene delivery. Since enzymes can degrade genetic materials during their blood circulation, dendrimers exhibit promising packaging and delivery alternatives, particularly for central nervous system (CNS) treatments. The DNA and RNA encapsulated in dendrimers represented by polyamidoamine that are used for targeted brain delivery, via chemical-structural adjustments and appropriate generation, significantly improve the correlation between transfection efficiency and cytotoxicity. This article reports a comprehensive review of dendrimers' structures, synthesis processes, and biological applications. Recent progress in diagnostic imaging processes and therapeutic applications for cancers and other CNS diseases are presented. Potential challenges and future directions in the development of dendrimers, which provide the theoretical basis for their broader applications in healthcare, are also discussed.

A bioluminescent probe for NQO1 overexpressing cancer cell imaging in vitro and in vivo

A bioluminescent probe NQO1-Luc toward NQO1 was constructed, which exhibits high selectivity and sensitivity toward NQO1 in vitro and adequate capability of distinguishing NQO1-overexpressing tumors in vivo.