Effective One-for-All Phototheranostic Agent for Hypoxia-Tolerant NIR-II Fluorescent/PA Image-Guided Phototherapy

Near-infrared (NIR)-triggered type-I photosensitizers are crucial to address the constraints of hypoxic tumor microenvironments in phototherapy; however, significant challenges remain. By selecting an electron-deficient unit, a matched energy gap in the upper-level state is instrumental in boosting the efficiency of intersystem crossing for the type-I electron transfer process. 2-Cyanothiazole, an electron acceptor, is covalently linked with N, N-diphenyl-4-(thiophen-2-yl)aniline to yield a multifunctional photosensitizer (TTNH) that exhibits intrinsic NIR absorbance and compatible T2 energy levels, facilitating both radiative and nonradiative transitions. The prepared nanoparticles (TTNH NPs) assembled from TTNH are activated by an 808 nm laser and generated the O2•- for hypoxia-tolerant type-I photodynamic therapy under both normoxia and hypoxic conditions. TTNH NPs emitted NIR-II fluorescence with an impressive NIR-II fluorescence quantum yield of 2.08%. With a high photothermal conversion efficiency of 51.8% under 808 nm laser stimulation, TTNH NPs exhibit photothermal therapy performance, accompanied by enhanced photoacoustic imaging capability owing to their strong NIR absorption. These characteristics make TTNH an effective NIR-wavelength-triggered phototheranostic agent that outperforms NIR-II fluorescence/photoacoustic dual-model imaging-guided type-I photodynamic therapy/photothermal therapy against hypoxic tumors. This results provide valuable insight for developing high-performance NIR-II-emissive superoxide radical phototheranostic agents.

NIR-II Emissive Superoxide Radical Photogenerator for Photothermal/Photodynamic Therapy against Hypoxic Tumor

Due to the "Achilles' heels" of hypoxia, complicated location in solid tumor, small molecular photosensitizers with second near-infrared window (NIR-II) fluorescence, type-I photodynamic therapy (PDT), and photothermal therapy (PTT) have attracted great attention. However, these photosensitizers are still few but yet challenging. Herein, an "all in one" NIR-II acceptor-donor-acceptor fused-ring photosensitizer, Y6-Th, is presented for the in-depth diagnosis and efficient treatment of cancer. Benefiting from the strong intramolecular charge transfer, promoted highly efficient intersystem crossing, largely p-conjugated fused-ring structure, and reduced planarity, the fabricated nanoparticles (Y6-Th nanoparticles) can emit NIR-II fluorescence with the peak located at 1020 nm, exclusively generate O2•- for type-I PDT, and display excellent PTT performance under an 808 nm laser stimulation. These characteristics make Y6-Th a distinguished NIR-wavelength-triggered phototheranostic agent, which can effectively therapy the hypoxic tumor using NIR-II-fluorescence-guided type-I PDT/PTT. This work provides a valuable guideline for fabricating high-performing NIR-II emissive superoxide radical photogenerators.

Multifunctional Plasmon-Tunable Au Nanostars and Their Applications in Highly Efficient Photothermal Inactivation and Ultra-Sensitive SERS Detection

The development and application in different fields of multifunctional plasmonic nanoparticles (NPs) have always been research hotspots. Herein, multi-tip Au nanostars (NSs) with an anisotropic structure were fabricated for the photothermal therapy (PTT) of bacteria and surface-enhanced Raman scattering (SERS) detection of pollutants. The size and localized surface plasmon resonance (LSPR) characteristics of Au NSs were adjusted by varying Au seed additions. In addition, photothermal conversion performance of Au NSs with various Au seed additions was evaluated. Photothermal conversion efficiency of Au NSs with optimal Au seed additions (50 μL) was as high as 28.75% under 808 nm laser irradiation, and the heat generated was sufficient to kill Staphylococcus aureus (S. aureus). Importantly, Au NSs also exhibited excellent SERS activity for the 4-mercaptobenzoic acid (4-MBA) probe molecule, and the local electromagnetic field distribution of Au NSs was explored through finite-difference time-domain (FDTD) simulation. As verified by experiments, Au NSs' SERS substrate could achieve a highly sensitive detection of a low concentration of potentially toxic pollutants such as methylene blue (MB) and bilirubin (BR). This work demonstrates a promising multifunctional nanoplatform with great potential for efficient photothermal inactivation and ultra-sensitive SERS detection.

Synergistic photothermal-photodynamic-chemotherapy toward breast cancer based on a liposome-coated core-shell AuNS@NMOFs nanocomposite encapsulated with gambogic acid

A multifunctional nanoplatform with core–shell structure was constructed in one-pot for the synergistic photothermal, photodynamic, and chemotherapy against breast cancer. In the presence of gambogic acid (GA) as the heat-shock protein 90 (HSP90) inhibitor and the gold nanostars (AuNS) as the photothermal reagent, the assembly of Zr⁴⁺ with tetrakis (4-carboxyphenyl) porphyrin (TCPP) gave rise to the nanocomposite AuNS@ZrTCPP-GA (AZG), which in turn, further coated with PEGylated liposome (LP) to enhance the stability and biocompatibility, and consequently the antitumor effect of the particle. Upon cellular uptake, the nanoscale metal − organic framework (NMOF) of ZrTCPP in the resulted AuNS@ZrTCPP-GA@LP (AZGL) could be slowly degraded in the weak acidic tumor microenvironment to release AuNS, Zr⁴⁺, TCPP, and GA to exert the synergistic treatment of tumors via the combination of AuNS-mediated mild photothermal therapy (PTT) and TCPP-mediated photodynamic therapy (PDT). The introduction of GA serves to reduce the thermal resistance of the cell to re-sensitize PTT and the constructed nanoplatform demonstrated remarkable anti-tumor activity in vitro and in vivo. Our work highlights a facile strategy to prepare a pH-dissociable nanoplatform for the effective synergistic treatment of breast cancer.

An Enhanced Photothermal Therapeutic Iridium Hybrid Platform Reversing the Tumor Hypoxic Microenvironment

As hypoxia is closely associated with tumor progression, proliferation, invasion, metastasis, and strong resistance to therapy, regulating and overcoming the hypoxia tumor microenvironment are two increasingly important aspects of tumor treatment. Herein, we report a phototherapeutic platform that uses the organic photosensitizer diketopyrrolopyrrole (DPP) derivative and inorganic iridium salts (IrCl₃) with photothermal activity and the capacity to decompose H₂O₂ efficiently. The characterization of their photophysical properties proved that DPP-Ir nanoparticles are capable of remarkable near-infrared (NIR) absorption, and compared to DPP nanoparticles, the photothermal conversion efficiency (PCE) increases from 42.1% in DPP nanoparticles to 67.0% in DPP-Ir nanoparticles. The hybrid nanoparticles utilize the catalytic decomposition of endogenous H₂O₂ to produce oxygen for the downregulation of the hypoxia-inducible factor 1 subunit alpha (HIF-1α) protein, which could reverse the tumor hypoxic microenvironment. Benefiting from the excellent optical properties and good biocompatibility, the hybrid platform exhibits efficient photothermal therapeutic effects as well as good biological safety. In conclusion, such a hybrid platform could improve photothermal therapy against cancer.

Development of Nickel Selenide@polydopamine Nanocomposites for Magnetic Resonance Imaging Guided NIR-II Photothermal Therapy

The penetration depth of near-infrared laser has greatly restricted the development of most photothermal agents. Recently, photothermal agents in the second near-infrared (NIR-II) window have drawn great attention as they can overcome above barrier. Herein, a novel "all in one" NIR-II responsive nanoplatform (nickel selenide @polydopamine nanocomposites, NiSe@PDA NCs) based on in situ coating the polydopamine (PDA) on the surface of biomineralized nickel selenide nanoparticles (NiSe NPs) for dual-model imaging-guided photothermal therapy is reported. Under the illumination of NIR-II laser (1064 nm), the photothermal conversion efficiency of NiSe@PDA NCs can reach 48.4%, which is higher than that of single NiSe NPs due to the enhanced molar extinction coefficient. In addition, because of the paramagnetic effect of NiSe NPs, the constructed NiSe@PDA NCs can be acted as T₁ contrast agent for magnetic resonance imaging (MRI). Most importantly, the MRI contrast effect is enhanced with the coating of PDA layer due to the loose structure of PDA. Ultimately, both in vitro and in vivo experiments demonstrate that the developed NCs can achieve efficient MRI-guided photothermal therapy for treating malignant tumor. Therefore, the designed NiSe@PDA NCs with excellent features show great potential for clinical MRI-guided cancer therapy.

An Acceptor-π-Donor Structured Organic Chromophore for NIR Triggered Thermal Ablation of Tumor via DNA Damage-Mediated Apoptosis

INTRODUCTION

It will be challenging to develop high-performance organic chromophores for light-triggered thermal ablation of the tumor. Besides, the mechanisms of organic chromophores for tumor therapy remain unclear. Herein, an acceptor-π-donor (A-π-D) structured organic chromophore based on 2-dicyanomethylenethiazole named PTM was developed for photothermal therapy (PTT) of tumors.

METHODS AND RESULTS

Biocompatible PTM nanoparticles (PTM NPs) were fabricated by enclosing PTM with Pluronic F-127. The results of optical and photothermal properties of PTM NPs showed robust near-infrared (NIR) absorption, excellent photostability and high photothermal conversion efficiency (56.9%). The results of flow cytometry, fluorescence microscopy, apoptosis, CCK-8 assays and animal experiments showed that PTM NPs had a good killing effect on tumors under NIR laser irradiation. Furthermore, mechanistic studies, RNA-seq and biological analysis revealed that PTM NPs can cause tumor cell death via DNA damage-mediated apoptosis.

CONCLUSION

Light-induced thermal ablation effects of PTM NPs in vitro and vivo were surveyed. Collectively, our studies provided a new approach to developing a safe and effective photothermal agent for cancer treatment.

A high-contrast photoacoustic agent with near-infrared emission

Benzobisthiadiazole as a typical electron acceptor, has been widely used to design fluorescent dyes and photoacoustic (PA) agents. With the strategy of constructing donor-acceptor-donor (D-A-D) type of electron characteristics, benzobisthiadiazole derivatives tend to behave stable in near-infrared absorption and emission, which is beneficial to PA imaging. In this chapter, two molecular design strategies are combined to improve the photoacoustic imaging effects of new PA contrast agent IR-1302 NPs, by installing strengthened conjugated bridges and electron donors. The nanoparticles exhibit high-contrast noninvasive photoacoustic imaging in tumor models with longer wavelength absorption and emission and show potential as a clinic contrast agent.

Near-infrared photothermally activated nanomachines for cancer theragnosis

Near-infrared photothermal-activated nanomaterials are emerging as a promising tool in precise cancer theranostics. This Frontier article highlights the recent advances of photothermal-activated nanoagents in biomedical applications, namely photothermal-initiated drug/contrast agent release, gene silencing, programmed targeting and gas theranostics. In the end, we give a perspective on the further development of photothermal-sensitive nanomedicines.