Embedding CdS@Au into Ultrathin Ti3–xC2Ty to Build Dual Schottky Barriers for Photocatalytic H2 Production

Suffering from the laborious synthesis and undesirable tumor microenvironment response, the exploitation of novel NIR-II absorbing organic photothermal agents is of importance to promote phototherapeutic efficacy. Herein, two kinds of charge-transfer complex nanoparticles (TMB-F4TCNQ and TMB-TCNQ) are prepared by supramolecular assembly. Because of the larger energy gap between donor and acceptor, TMB-F4TCNQ presents higher charge-transfer degree (72 %) than that of TMB-TCNQ (48 %) in nanoaggregates. Therefore, TMB-F4TCNQ exhibits stronger NIR-II absorption ability with a mass extinction coefficient of 15.4 Lg-1  cm-1 at 1300 nm and excellent photothermal effect. Impressively, the specific cysteine response can make the TMB-F4TCNQ effectively inhibit the intracellular biosynthesis of GSH, leading to redox dsyhomeostasis and ROS-mediated ferroptosis. TMB-F4TCNQ can serve as a contrast agent for NIR-II photoacoustic imaging to guide precise and efficient photothermal therapy in vivo.

Biodegradable Charge-Transfer Complexes for Glutathione Depletion Induced Ferroptosis and NIR-II Photoacoustic Imaging Guided Cancer Photothermal Therapy

Precise manipulation of optical properties through the structure-evolution of plasmonic nanoparticles is of great interest in biomedical fields including bioimaging and phototherapy. However, previous success has been limited to fixed assembled structures or visible-NIR-I absorption. Here, an activatable NIR-II plasmonic theranostics system based on silica-encapsulated self-assembled gold nanochains (AuNCs@SiO2 ) for accurate tumor diagnosis and effective treatment is reported. This transformable chain structure breaks through the traditional molecular imaging window, whose absorption can be redshifted from the visible to the NIR-II region owing to the fusion between adjacent gold nanoparticles in the restricted local space of AuNCs@SiO2 triggered by the high H2 O2 level in the tumor microenvironment (TME), leading to the generation of a new string-like structure with strong NIR-II absorption, which is further confirmed by finite-difference-time-domain (FDTD) simulation. With the TME-activated characteristics, AuNCs@SiO2 exhibits excellent properties for photoacoustic imaging and a high photothermal conversion efficiency of 82.2% at 1064 nm leading to severe cell death and remarkable tumor growth inhibition in vivo. These prominent intelligent TME-responsive features of AuNCs@SiO2 may open up a new avenue to explore optical regulated nano-platform for intelligent, accurate, and noninvasive theranostics in NIR-II window.

Activatable NIR-II Plasmonic Nanotheranostics for Efficient Photoacoustic Imaging and Photothermal Cancer Therapy.

Small organic photothermal agents (SOPTAs) that absorb in the second near-infrared (NIR-II, 1000-1700 nm) window are highly desirable in photothermal therapy for their good biocompatibility and deeper tissue penetration. However, the design of NIR-II absorbing SOPTAs remains a great challenge. Herein, we report that molecular engineering of BF2 complex via strengthening the donor-acceptor conjugation and increasing the intramolecular motions is an efficient strategy to achieve NIR-II absorbing SOPTAs with high photothermal performance. Based on this strategy, a BF2 complex, BAF4, was designed and synthesized. BAF4 exhibits an intense absorption maximum at 1000 nm and negligible fluorescence. Notably, the nanoparticles of BAF4 achieve a high photothermal conversion efficiency value of 80 % under 1064 nm laser irradiation (0.75 W cm-2 ). In vitro and in vivo studies reveal the great potential of BAF4 nanoparticles in photoacoustic imaging-guided photothermal therapy in the NIR-II window.

A Borondifluoride-Complex-Based Photothermal Agent with an 80% Photothermal Conversion Efficiency for Photothermal Therapy in the NIR-II Window

Summary Phototheranostics integrates deep-tissue imaging with phototherapy (containing photothermal therapy and photodynamic therapy), holding great promise in early diagnosis and precision treatment of cancers Recently, second near-infrared (NIR-II) fluorescence imaging exhibits the merits of high accuracy and specificity, as well as real-time detection Among the NIR-II fluorophores, organic small molecular fluorophores have shown superior properties in the biocompatibility, variable structure, and tunable emission wavelength than the inorganic NIR-II materials What's more, some small molecular fluorophores also display excellent cytotoxicity when illuminated with the NIR laser This review summarizes the progress of small molecular NIR-II fluorophores with different central cores for cancer phototheranostics in the past few years, focusing on the molecular structures and phototheranostic performances Furthermore, challenges and prospects of future development toward clinical translation are discussed

Small Molecular NIR-II Fluorophores for Cancer Phototheranostics.

The localized surface plasmon resonance (LSPR) of plasmonic nanomaterials is highly dependent on their structures. Going beyond simple shape and size, further structural diversification demands the growth of non-wetting domains. Now, two new dimensions of synthetic controls in Au-on-Au homometallic nanohybrids are presented: the number of the Au islands and the emerging shapes. By controlling the interfacial energy and growth kinetics, a series of Au-on-AuNR hybrid structures are successfully obtained, with the newly grown Au domains being sphere and branched wire (nanocoral). The structural variety allowed the LSPR to be fine-tuned in full spectrum range, making them excellent candidates for plasmonic applications. The nanocorals exhibit black-body absorption and outstanding photothermal conversion capability in NIR-II window. In vitro and in vivo experiments verified them as excellent photothermal therapy and photoacoustic imaging agents.

Fine-Tuning the Homometallic Interface of Au-on-Au Nanorods and Their Photothermal Therapy in the NIR-II Window.

The plasmonic property of a nanostructure is highly dependent on its morphology, but there are few methods for appending a domain as the "functional group" or modifier. As a means of modulating plasmonic properties, we create and modulate Au hats on Au nanoparticles, including mortarboards, beret hats, helmets, crowns, antler hats and antenna hats. The structural control arises from the active surface growth as a result of dynamic competition between ligand absorption and metal deposition. It allows the continuous tuning of hat morphologies, from the facet-controlled growth of mortarboards, to the spreading-favored growth of beret hats and helmets, and to the vertical growth of pillars in crowns, antler hats and antenna hats. Among these plasmonic nanostructures, the mortarboards show excellent SERS enhancement of 8.1 × 105, which is among the best in colloidal nanostructures; and the antler hats show the photothermal conversion efficiency of 66.2%, which compares favorably with the literature reports.

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Shuaibin Li

Papers

Fine-Tuning the Homometallic Interface of Au-on-Au Nanorods and Their Photothermal Therapy in the NIR-II Window.

Designing caps for colloidal Au nanoparticles.

Partial Silica Encapsulation of Fe3O4 Nanoparticles in Reverse Emulsion by Internal Energy Modulation