Large Hollow Cavity Luminous Nanoparticles with Near-Infrared Persistent Luminescence and Tunable Sizes for Tumor Afterglow Imaging and Chemo-/Photodynamic Therapies

Persistent luminous nanoparticles (PLNPs) have been capturing increasing attention in biomedical imaging because of their long-life emission and concomitant benefits ( e.g., zero-autofluorescence background, high signal-to-noise ratio). Although there are quite some synthetic methodologies to synthesize PLNPs, those for constructing functional structured PLNPs remain largely unexplored. Herein we report the design principle, synthesis route, and proof-of-concept applications of hollow structured PLNPs with near-infrared (NIR) persistent luminescence, namely afterglow, and tunable sizes for tumor afterglow imaging and chemical/photodynamic therapies. The design principle leverages on the crystallization of the immobilized parent ions on the purgeable carbon spheres. This strategy provides large and size-tunable hollow cavities to PLNPs after calcination. Building on the hollow cavity of PLNPs, high chemical drug (DOX) or photosensitizer (Si-Pc) loading can be achieved. The DOX/Si-Pc-loaded hollow PLNPs exhibit efficient tumor suppression based on the features of large cavity and afterglow of PLNPs. These hollow structured PLNPs, like traditional solid PLNPs, are quite stable and can be repeatedly activated, and particularly can selectively target tumor lesion, permitting rechargeable afterglow imaging in living mice. Our research supplies a strategy to synthesize hollow structured PLNPs, and hopefully it could inspire other innovative structures for cancer theranostics.

Semiconducting Photosensitizer-Incorporated Copolymers as Near-Infrared Afterglow Nanoagents for Tumor Imaging

The fact that cancer metastasis is the main cause of death for most cancer patients necessitates the development of imaging tools for sensitive detection of metastases. Although optical imaging has high temporospatial resolution, tissue autofluorescence compromises the sensitivity for in vivo imaging of cancer metastasis. Herein, the synthesis of a series of photosensitizer-incorporated poly(p-phenylenevinylene)-based semiconducting copolymers and their utility as near-infrared (NIR) afterglow imaging nanoagents that emit light after cessation of light irradiation are reported. As compared with nondoped nanoparticles, the nanoparticles derived from the photosensitizer-incorporated copolymers have red-shifted NIR luminescence and amplified afterglow signals, allowing the detection of tiny peritoneal metastatic tumors almost invisible to naked eye. Moreover, the intrinsic oxygen-sensitive nature of afterglow makes those nanoagents potentially useful for in vivo imaging of oxygen levels. Thus, this study introduces a generation of light-excitation-free background-minimized optical imaging agents for the sensitive detection of diseased tissues in vivo.

Ultralong Organic Phosphorescent Nanocrystals with Long-Lived Triplet Excited States for Afterglow Imaging and Photodynamic Therapy

The development of novel applications of ultralong organic phosphorescent (UOP) materials is highly desired. Herein, a series of UOP materials (EDCz, E = O, S, Se, and Te) for bacterial afterglow imaging and photodynamic therapy (PDT) is reported. By structurally bonding with the chalcogen atoms with π-conjugated scaffolds, EDCz not only absorbs visible light but also emits UOP with an efficiency of ca. 0.01-6.8% and a long lifetime of 0.08-0.318 s under ambient conditions. Benefiting from the long-lived triplet excited states, the SeDCz nanocrystals (NCs) possessed the best optical properties in the series, generating ¹O₂ under white light irradiation and performing as an agent for Staphylococcus aureus afterglow imaging and PDT at a low concentration (98 ng mL^-1). The SeDCz NCs are also utilized as real-time UOP imaging agents and promoted healing of infected wounds in living mice. To the best of our knowledge, this study presents the first example of UOP-based bacterial photodynamic theranostic agents and creates a platform for the next-generation efficient UOP-based photosensitizers for bioimaging and skin regeneration.

Progress on Carbon Dots with Intrinsic Bioactivities for Multimodal Theranostics

Carbon dots (CDs) with intrinsic bioactivities are candidates for bioimaging and disease therapy due to their diverse bioactivities, high biocompatibility, and multiple functionalities in multimodal theranostics. It is a multidisciplinary research hotspot that includes biology, physics, materials science, and chemistry. This progress report discusses the CDs with intrinsic bioactivities and their applications in multimodal theranostics. The relationship between the synthesis and structure of CDs is summarized and analyzed from a material and chemical perspective. The bioactivities of CDs including anti-tumor, antibacterial, anti-inflammatory etc. are discussed from biological points of view. Subsequently, the optical and electronic properties of CDs that can be applied in the biomedical field are summarized from a physical perspective. Based on the functional review of CDs, their applications in the biomedical field are reviewed, including optical diagnosis and treatment, biological activity, etc. Unlike previous reviews, this review combines multiple disciplines to gain a more comprehensive understanding of the mechanisms, functions, and applications of CDs with intrinsic bioactivities.

Dual-purposing disulfiram for enhanced chemotherapy and afterglow imaging using chlorin e6 and semiconducting polymer combined strategy

Rationale: One of the main challenges in chemotherapy is achieving high treatment efficacy while minimizing adverse events. Fully exploiting the therapeutic potential of an old drug and monitoring its effects in vivo is highly valuable, but often difficult to achieve. Methods: In this study, by encapsulating disulfiram (DSF) approved by US Food and Drug Administration, semiconducting polymer nanocomplex (MEHPPV), and Chlorin e6 into a polymeric matrix F127 via nanoprecipitation method, a nanosystem (FCMC) was developed for afterglow imaging guided cancer treatment. The characteristics, stability as well as the ability of singlet oxygen (1O2) production of FCMC were first carefully examined. Then, we studied the mechanism for enhanced anti-cancer efficiency and afterglow luminescence in vitro. For experiments in vivo, 4T1 subcutaneous xenograft tumor mice were injected with FCMC via the tail vein every three days and the antitumor effect of FCMC was evaluated by monitoring tumor volume and body weight every three day. Results: The nanosystem, which combines DSF with Ce6, can generates abundant 1O2 that enhances the antitumor activity of DSF. The in vivo results show that FCMC-treated group exhibits an obviously higher tumor-growth inhibition rate of 67.89% after 15 days of treatment, compared to the control group of F127@MEHPPV-CuET. Moreover, Ce6 also greatly enhances the afterglow luminescence intensity of MEHPPV and promotes the redshift of the afterglow emission towards the ideal near-infrared imaging window, thereby enabling efficient afterglow tumor imaging in vivo. Conclusions: This multifunctional nanoplatform not only improves the anticancer efficacy of DSF, but also enables monitoring tumor via robust afterglow imaging, thus exhibiting great potential for cancer therapy and early therapeutic outcome prediction.

"All-in-One" Photochemical Afterglow Nanoplatform Based on Perovskite Quantum Dots

Photochemical reaction-based afterglow materials offer a promising solution to the tissue autofluorescence issues associated with real-time excitation in traditional fluorescence probes. Conventional photochemical afterglow systems typically consist of three components: a photosensitizer, an energy cache unit (ECU), and an emitter. However, their physical separation leads to inefficient energy transfer. We present a strategy for constructing an "all-in-one" afterglow nanoplatform (AGNP) based on perovskite quantum dots (PQDs) to enhance the energy transfer efficiency by minimizing physical separation. Modified with 1-pyrenecarboxylic acid (PCA), CsPbBr3 PQDs can serve as a photosensitizer, emitter, and ECU-phenylacetic acid (ECU-COOH) host simultaneously. The afterglow intensity of the AGNP shows a remarkable 30-fold enhancement compared with the separated ECU afterglow system, attributed to the decreased energy transfer distance. The AGNP also exhibits great versatility, enabling tunable afterglow emission across the visible region. The AGNP is further adopted for in vivo afterglow imaging with a signal-to-noise ratio of 41. This work provides an idea for constructing "all-in-one" afterglow systems and demonstrates their potential for background-free bioimaging.

Ultrasound-Activated Near-Infrared-II Afterglow Luminescence for Precise Cancer Imaging

Afterglow fluorescence imaging has been extensively assessed in ultrasensitive bioimaging. Since it eliminates the need for real-time excitation light and thereby circumvents the autofluorescence background of tissue, it holds tremendous potential in accurate biomedical imaging. However, current afterglow probes are rare and emit light only in the visible to near-infrared (NIR) range, which is inadequate for in vivo imaging. To resolve this issue, an ultrasound (US)-activated NIR-II afterglow luminescence probe (NPs-Ce4-SN) emitting afterglow luminescence with a peak at ∼1100 nm was developed. This peak is nearly 400 nm red-shifted compared with other reported afterglow probes. Of note, after US termination, NPs-Ce4-SN undergoes energy transformation to produce 1O2 and subsequently undergoes internal oxidation-reduction reaction to produce NIR-II afterglow, generating high signal-to-noise ratio and high-penetration depth imaging. In vitro and in vivo NIR-II afterglow imaging experiments revealed that NPs-Ce4-SN has good biocompatibility and deep tissue penetration depth, suggesting a diagnostic strategy for in vivo tumor imaging with a high signal-to-noise ratio.