Achieving Efficient NIR-II Type-I Photosensitizers for Photodynamic/Photothermal Therapy upon Regulating Chalcogen Elements

Reprogrammed glycolysis-induced augmentation of NIR-II excited photodynamic/photothermal therapy

Small molecule-based multifunctional optical diagnostic materials have garnered considerable interest due to their highly customizable structures, tunable excited-state properties, and remarkable biocompatibility. We herein report the synthesis of a multifaceted photosensitizer, PPQ-CTPA, which exhibits exceptional efficacy in generating Type I reactive oxygen species (ROS) and thermal energy under near-infrared-II (NIR-II, >1000 nm) laser excitation at 1064 nm, thereby combining photodynamic therapy (PDT) and photothermal therapy (PTT) functionalities. To enhance therapeutic efficacy, we engineered lonidamine (LND) by conjugating it with triphenylphosphonium (TPP) cations, producing LND-TPP. This compound inhibits mitochondrial glycolysis and downregulates heat shock protein 90 (HSP 90) levels in a breast cancer mouse model, potentiating both PDT and PTT. For in vivo applications, PPQ-CTPA and LND-TPP are encapsulated within the amphiphilic polymer DSPE-SS-PEG to obtain PPQ-CTPAL NPs. In breast cancer cell lines, PPQ-CTPAL NPs are decomposed by cellular GSH, simultaneously releasing the dual-functioning photosensitizer PPQ-CTPL and the mitochondria-disrupting agent LND-TPP. Upon 1064 nm laser irradiation, we found that tumor growth in breast cancer mice is effectively restrained by PPQ-CTPAL NPs. This work highlights the synergistic integration of PDT, PTT, and chemotherapy facilitated by NIR-II fluorescence, photoacoustic, and photothermal imaging under 1064 nm irradiation, underscoring the clinical potential of multifunctional phototherapeutic agents.

Multi-dimensional donor engineering of NIR-II AIEgens for multimodal phototheranostics of orthotopic breast cancer

"One-for-all" multimodal phototheranostic agents, which integrate multiple photodiagnostic and phototherapeutic functionalities into a single component, have emerged as promising platforms for advancing cancer treatment. Among these, agents featuring second near-infrared (NIR-II) emission are particularly appealing due to their superior tissue penetration depth and high signal-to-background ratio (SBR). However, most reported NIR-II fluorophores suffer from severely imbalanced radiative and non-radiative excited-state energy dissipation in biological environments, resulting in extremely low fluorescence quantum yields (QYs) and limited diagnostic efficacy. This highlights the urgent need for innovative molecular design strategies to develop high-performance NIR-II "one-for-all" multimodal phototheranostic agents. Herein, we present, for the first time, a multi-dimensional donor engineering protocol that optimizes donor design at the molecular, aggregated, and solvent-interaction levels. By introducing 2,4,4-trimethylpentan-2-yl groups into the diphenylamine indeno[1,2-b]thiophene donor unit, we developed a donor-acceptor-donor (D-A-D) type NIR-II aggregation-induced emission-active luminogen (AIEgen), i.e. OPITBT. When formulated into nanoparticles (NPs), OPITBT NPs exhibited a 16-fold enhancement in fluorescence QY compared to OPITBT in tetrahydrofuran, along with excellent photothermal conversion efficiency (PCE) and acceptable type-I reactive oxygen species (ROS) generation. When further fabricated into tumor-targeting NPs, the resulted OPITBT-R NPs effectively eliminated orthotopic breast cancer through fluorescence-photoacoustic-photothermal multimodal imaging-guided photodynamic-photothermal synergistic therapy under single 808 nm laser irradiation. Notably, the exceptional NIR-II fluorescence brightness of OPITBT-R NPs enables high-resolution NIR-IIb whole-body vascular imaging in living mice. This work provides a versatile strategy to enhance radiative dissipation of NIR-II fluorophores for balanced phototheranostic performance and advances the development of "one-for-all" phototheranostic systems.

Engineering long-lived charge separation states boosts type-I ROS generation for efficient cancer therapy

Organic photosensitizers (PSs) with long-lived charge-separated states (CSs) are optimal for converting photonic energy into reactive oxygen species (ROS) by maximizing the interaction between excited electrons and holes in subsequent photoreactions. However, the substantial consumption of oxygen by the singlet oxygen species produced by these PSs can significantly impede their anticancer efficacy, because of the hypoxia nature of solid tumors. Herein, we present a rational strategy for the structural modification of the well-known Fukuzumi acridinium salt (9-mesityl-10-methylacridinium ion) with long-lived CSs, by incorporating a methyl-substituted diphenylamine group (named MTPAA). This modification significantly enhances type-I ROS generation. The "methyl effect" in MTPAA has distinguished merits of stabilized radical species through resonance, leading to an over 8-fold increase in type-I ROS generation compared to TPAA, which lacks the methyl group. Moreover, cellular experiments show that MTPAA with the "methyl effect" significantly enhances photodynamic therapy efficacy under hypoxic conditions. Our molecular design strategy offers a promising approach to creating high-performance type-I PSs and is anticipated to inspire broader exploration in other photosensitizer systems with long-lived CSs, serving as a versatile strategy for advancing type-I PS development.

Dendritic donor engineering to optimize second near-infrared photothermal agents for in situ photothermal therapy

Small organic photothermal agents (PTAs) with dual photothermal and imaging functions in the second near-infrared (NIR-II) window present a promising strategy for deep tumor treatment, however, fluorescence quenching conventional PTAs and low photothermal conversion efficiency (PCE) present obstacles to their widespread application. In this study, a novel "dendritic donor engineering" strategy was employed to design NIR-II organic PTAs (named DCTBBT and TCTBBT) with donor-π-acceptor-π-donor features and aggregation-induced emission (AIE) activity. Owing to the fine-tuning of the dendritic donors, the close co-facial packing of the central π-backbone was disrupted, effectively avoiding fluorescence quenching caused by π-π aggregation, which facilitated molecule-free motions in aggregate state, and as a result, the DCTBBT nanoparticles (NPs) demonstrated a PCE of 59.8 %. Besides, both in vitro and in vivo evaluations demonstrate that DCTBBT NPs exhibit superior antitumor efficacy by the photothermal therapy (PTT). This study provides valuable insights into the development of advanced NIR-II PTAs for practical applications in phototheranostics.

Photochemical bomb: Precision nuclear targeting to activate cGAS-STING pathway for enhanced bladder cancer immunotherapy

Activating the cGAS-STING pathway presents a promising strategy to enhance the innate immunity and combat the immunosuppressive tumor microenvironment. One key mechanism for triggering this pathway involves the release of damaged DNA fragments caused by nuclear DNA damage. However, conventional cGAS-STING agonists often suffer from limited nucleus-targeting efficiency and potential biotoxicity. In this study, we develop a novel nucleus-targeting theranostic nanoplatform designed to synergistically activate the cGAS-STING pathway through the combination of photodynamic therapy (PDT) and cisplatin chemotherapy for orthotopic bladder cancer treatment. The nanoplatform integrates a new high-performance type-I photosensitizer with near-infrared-II emission, a TATSA peptide for enhanced nuclear targeting, and a biosafe platinum (IV) cisplatin prodrug. Upon NIR laser irradiation, the nanoagent delivers synergistic nucleus-targeted PDT and chemotherapy, causing substantial DNA damage and the release of double-stranded DNA, which subsequently activates the cGAS-STING pathway and triggers potent immunomodulation. This activation promotes dendritic cells maturation, enhances cytotoxic T infiltration, and facilitates the formation of memory T cells, leading to immune microenvironment remodeling, and long-lasting immune memory, thus effectively inhibiting orthotopic bladder tumors and reducing the risk of metastasis. These findings highlight the substantial potential of this strategy to overcome the limitations of current immunotherapies by leveraging nucleus-targeted PDT to activate the cGAS-STING pathway for cancer treatment.

Dual-target regulation of glutathione and heat shock proteins via molecular-carrier-pathway triple-engineering for potentiated phototherapy

Photodynamic therapy (PDT) and photothermal therapy (PTT) face efficacy limitations due to overexpressed glutathione (GSH) and activated heat shock proteins (HSPs). Here, we synthesized a multifunctional agent N3-4F (N3) through molecular engineering. Leveraging strong acceptor-donor (A-D) interactions and reduced singlet-triplet energy gap (ΔES-T), N3 demonstrated exceptional type I/II reactive oxygen species (ROS) generation. An extended π-conjugated backbone with long alkyl chains enhanced light absorption and conferred a remarkable photothermal conversion efficiency (PCE) of 44.9%. To overcome tumor microenvironmental limitations, we engineered a disulfide bond-integrated nanocarrier and co-delivered HSP inhibitor KNK437 (437), selectively depleting intracellular GSH while disrupting thermoresistance. In vivo studies revealed that N3@437 under 808 nm laser irradiation achieved 94.9% tumor growth inhibition and markedly suppressed lung metastasis. By employing a triple-pronged strategy of molecular engineering, nanocarrier design, and pathway blockage, this work pioneered a paradigm that concurrently depletes GSH and inhibits HSPs. This breakthrough enables enhanced PDT/PTT performance, offering a transformative solution for combating tumor adaptive resistance.

Recent Advances in Nano-Drug Delivery Strategies for Chalcogen-Based Therapeutic Agents in Cancer Phototherapy

Chalcogen-containing therapeutic agents (TAs), which include sulfur (S), selenium (Se), and tellurium (Te) atoms, have recently emerged as a promising class of photosensitizers (PSs) and photothermal agents (PTAs) for cancer phototherapy. The incorporation of heavier chalcogens into organic chromophores leads to visible-to-near-infrared (VIS-NIR) light absorption, efficient triplet harvesting, and adequate heat and energy transfer efficiency, all of which are paramount for photodynamic therapy (PDT) and photothermal therapy (PTT). However, chalcogen-based PSs/PTAs suffer from photostability, bioavailability, and targeted delivery issues, which minimize their PDT/PTT performances. Nevertheless, significant progress in the rational design of nanoencapsulation strategies has been achieved to overcome the challenges of chalcogen-based TAs for effective phototherapeutic cancer treatment. This review highlights the recent advances (within the last five years) in nano-drug delivery approaches adapted for chalcogen-substituted PSs/PTAs for PDT, PTT, or synergistic PDT/PTT, integrating imaging and treatment. The PSs/PTAs described in this review are classified into three classes: (i) sulfur, (ii) selenium, and (iii) tellurium-containing TAs used in phototherapy applications. This review offers a comprehensive perspective on the design of chalcogen-substituted photosensitizers (PSs) and photothermal agents (PTAs), covering spectroscopic and computational characterization, nanoformulation strategies, and their roles in enhancing reactive oxygen species (ROS) generation and photothermal conversion efficiency for improved in vitro and in vivo performance. We hope this work will encourage further research into nanotechnological strategies designed to enhance the phototherapeutic efficacy of chalcogen-containing therapeutic agents.

Conjugated Polymer-Photosensitizers for Cancer Photodynamic Therapy and Their Multimodal Treatment Strategies

Conjugated polymers (CPs) have emerged as promising candidates for photodynamic therapy (PDT) in cancer treatment due to their high fluorescence quantum yield, excellent photostability, and remarkable reactive oxygen species (ROS) generation capability. This review systematically summarizes molecular design strategies to augment CP photosensitivity efficiency, including: (1) constructing donor-acceptor (D-A) alternating structures, (2) incorporating aggregation-induced emission (AIE) moieties, (3) employing heavy-atom effects, and (4) designing hyperbranched architectures. In addition, considering the limitations of monotherapy like tumor heterogeneity, we will further discuss the synergistic treatment strategies of CP-mediated PDT in combination with other therapeutic modalities, including photothermal therapy (PTT)-PDT, immunotherapy-PDT, chemotherapy-PDT, Chemiluminescence (CL)-PDT, diagnostic technology-PDT, and chemodynamic therapy (CDT)-PDT. These multimodal approaches leverage complementary mechanisms to achieve enhanced tumor eradication efficacy.

Recent Progress of Molecular Design in Organic Type I Photosensitizers

Photodynamic therapy (PDT) represents a high-efficient and non-invasive therapeutic modality for current and future tumor treatments, drawing extensive attention in the fields of antitumor drug and clinical phototherapy. In recent years, the photosensitizer (PS) market and PDT clinical applications have expanded to address various cancers and skin diseases. However, hypoxic environment within tumors poses a substantial challenge to the therapeutic capability of reactive oxygen species-dependent PDT. Consequently, researches have increasingly focus from the type II to type I PDT mechanism, which relies on radical production with less or no oxygen dependence. Despite significant progress in the development of type I PSs, a holistic understanding regarding the design principles for these molecules remains elusive. Specifically, electron transfer-mediated type I PDT are extensively studied in recent years but is insufficiently addressed in existing reviews. This review systematically summarizes recent advancements in the molecular design rationales of organic type I PSs, categorizing them into three key fundamental strategies: modulating PS charge distribution, singlet oxygen forbidden via low triplet excited state, and accelerating PS radical formation via inducing electron transfer. This review aims to offer valuable insights for the future type I PS design and the advancement of anti-hypoxia PDT.

Unlocking the Potential of Disulfidptosis: Nanotechnology-Driven Strategies for Advanced Cancer Therapy

Tumor tissues exhibit elevated oxidative stress, with the cystine-glutamate transporter xCT solute carrier family 7 member 11 (xCT/SLC7A11) protecting cancer cells from oxidative damage by facilitating cystine uptake for glutathione synthesis. Disulfidptosis, a newly identified form of programmed cell death (PCD), occurs in cells with high xCT/SLC7A11 expression under glucose-deprived conditions. Distinct from other PCD pathways, disulfidptosis is characterized by aberrant disulfide bond formation and cellular dysfunction, ultimately resulting in cancer cell death. This novel mechanism offers remarkable therapeutic potential by targeting the inherent oxidative stress vulnerabilities of rapidly growing cancer cells. Advances in nanotechnology enable the development of nanomaterials capable of inducing reactive oxygen species (ROS) generation, disrupting disulfide bonds. In addition, they are capable to deliver therapeutic agents directly to tumors, thereby improving therapeutic precision and minimizing off-target effects. Moreover, combining disulfidptosis with ROS-induced immunogenic cell death can remodel the tumor microenvironment and enhance anti-tumor immunity. This review explores the mechanisms underlying disulfidptosis, its therapeutic potential in cancer treatment, and the synergistic role of nanotechnology in amplifying its effects. Selective induction of disulfidptosis using nanomaterials represents a promising strategy for achieving more effective, selective, and less toxic cancer therapies.

Synthesis and photochromism of a turn-on fluorescent diarylethene having benzo[b]selenophene groups as the aryl units

Herein, we report the synthesis of a novel diarylethene derivative, which has benzo[b]selenophene groups as the aryl units, and its photochromic properties. The derivative exhibited a unique turn-on mode fluorescence photoswitching along with photochromic reactions in solution as well as in solid powder states.

Optical Microneedle-Enhanced Transdermal Light Scattering for In Situ Photothermal Therapy Targeting Basal-Layer Psoriasis

Near-infrared (NIR) light-mediated photothermal and photodynamic therapies are promising for nonsurgical treatment of skin diseases. However, the skin's inherent light absorption, especially from melanin in the epidermis, attenuates NIR energy penetration, limiting photothermal efficacy and potentially causing off-target tissue damage. In this context, we developed subcutaneous light response-enhanced microneedles (SLE MNs) that allow basal layer-localized seeding of therapeutics and leverage physical channels to efficiently transmit light transdermally, facilitating in situ scattered light activation for enhanced photothermal and photodynamic therapy outcomes. Such ultraoptical SLE MNs facilitated NIR light penetration, achieving up to 80% of initial light power at 500 μm subcutaneously, representing an approximate 160% increase compared to the control groups. Additionally, we conceptualized a two-segmented MN structure integrating light-guiding channels with photoresponsive therapeutics to enable precise in situ basal-layer treatment, effectively mitigating local hyperenergy on the skin surface and energy attenuation within tissues. This optical SLE MN patch offers a transformative platform for transdermal light therapy with significant clinical potential.

A NIR-II emissive sonosensitized biotuner for pyroptosis-enhanced sonodynamic therapy of hypoxic tumors

Pyroptosis is considered as a new way to effectively boost the immune response of tumors and inhibit tumor growth. Effective strategies to induce pyroptosis mainly rely on chemotherapeutic drugs and phototherapy, but their potential biotoxicity and phototoxicity limit their application in biomedicine. Herein, we designed a NIR-II emitting pyroptosis biotuner, Rd-TTPA, which induced pyroptosis under ultrasound irradiation to achieve pyroptosis-enhanced sonodynamic therapy (SDT) and immunogenic cell death (ICD) for tumors. Benefiting from its A-π-D1-D2 structure enhanced donor-acceptor interaction, Rd-TTPA can induce cell pyroptosis under both normoxia (21 % O2) and hypoxia (2 % O2) conditions by rapidly generating superoxide radicals (O2-•) upon ultrasound irradiation. The sonodynamic biotuner of pyroptosis overcomes the longstanding weakness of chemical drug and photosensitizer-based pyroptosis, such as drug resistance and limited penetration depth. In-depth studies demonstrated that Rd-TTPA can selectively target tumor cell mitochondria and possess excellent in vivo NIR-II fluorescence imaging capabilities. Administrating a tumor-bearing mouse model with Rd-TPPA, satisfying antitumor efficacy via pyroptosis-augmented SDT was achieved upon the guidance of NIR-II fluorescence imaging.

Donor modulation brings all-in-one phototheranostics for NIR-II imaging-guided type-I photodynamic/photothermal synergistic cancer therapy

Type-I photodynamic (PDT) and photothermal (PTT) synergistic therapy guided by fluorescence imaging in the near-infrared region II (NIR-II) is crucial for cancer diagnosis and treatment. Phototheranostics provide a promising system for efficient imaging-guided phototherapy, combining diagnostics with therapeutics within a single photosensitizer and avoiding the complexity of composition and low reproducibility of combination methods. Herein, we design and synthesize an all-in-one phototheranostic agent OTAB by modifying aza-BODIPY with a methoxy group substituted triphenylamine moiety, followed by the formation of nanoparticle OTAB@cRGD NPs via self-assembly with DSPE-PEG2000-cRGD. Structurally, the methoxy-modified triphenylamine moiety as a strong electron donor can reduce the singlet-triplet energy gap (ΔE S1-T1) by creating a strong intramolecular charge transfer state, thereby accelerating the intersystem crossing process and thus preferentially generating O2˙- via electron transfer. A single 808 nm laser can trigger its NIR-II imaging and excellent type-I photodynamic and photothermal therapy. Furthermore, OTAB@cRGD NPs with high photostability, colloid stability and biocompatibility can actively target tumor tissue via intravenous injection. Thus, tumor localization and imaging diagnosis are successfully realized. The PDT/PTT synergistic therapy brings efficient tumor inhibition and ablation both in vitro and in vivo. Therefore, this work provides a new strategy to construct an all-in-one multifunctional probe for the integration of NIR-II diagnosis and treatment.

Cascade-recharged macrophage-biomimetic ruthenium-based nanobattery for enhanced photodynamic-induced immunotherapy

Photodynamic-induced immunotherapy (PDI) is often hampered by low reactive oxygen species (ROS) yield, intra-tumor hypoxia, high glutathione (GSH) concentration, and immunosuppressive microenvironment. In view of this, a ruthenium (Ru)-based nanobattery (termed as IRD) with cascade-charged oxygen (O2), ROS, and photodynamic-induced immunotherapy by coordination-driven self-assembly of transition-metal Ru, photosensitizer indocyanine green (ICG), and organic ligand dithiobispropionic acid (DTPA). Then, IRD is camouflaged with macrophage membranes to obtain a nanobattery (termed as IRD@M) with targeting and immune evasion capabilities. Upon intravenous administration, IRD@M with a core-shell structure, nano diameter, and good stability can specifically hoard in tumor location and internalize into tumor cells. Upon disassembly triggered by GSH, the released Ru³⁺ not only catalyzes the conversion of endogenous hydrogen peroxide (H₂O₂) into O₂ to alleviate tumor hypoxia and reduce the expression of hypoxia-inducible factor-1α (HIF-1α), but also generates hydroxyl radicals (·OH) to elevate intracellular ROS levels. This process significantly enhances the photodynamic therapy (PDT) efficacy of the released ICG. Meanwhile, the released DTPA can significantly downregulate overexpressed GSH to reduce the elimination of ROS deriving from PDT by the exchange reaction of thiol-disulfide bond. It is also found that alleviating the hypoxic tumor microenvironment synergistically enhances the PDT efficacy, which in turn cascades to recharge the subsequent immune response, significantly improving the immunosuppressive tumor microenvironment and activating systemic tumor-specific immunity. Notably, in vitro and in vivo experimental results jointly confirm that such cascade-recharged macrophage-biomimetic Ru-based nanobattery IRD@M can achieve an obvious tumor elimination while results in a minimized side effect. Taken together, this work highlights a promising strategy for simple, flexible, and effective Ru-based immunogenic cell death (ICD) agents within PDI.

Heterodimeric Photosensitizer as Radical Generators to Promoting Type I Photodynamic Conversion for Hypoxic Tumor Therapy

Photodynamic therapy (PDT) using traditional type II photosensitizers (PSs) has been limited in hypoxic tumors due to excessive oxygen consumption. The conversion from type II into a less oxygen-dependent type I PDT pathway has shown the potential to combat hypoxic tumors. Herein, the design of a heterodimeric PS, NBSSe, by conjugating a widely used type I PS NBS and a type II PS NBSe via molecular dimerization, achieving the aggregation-regulated efficient type I photodynamic conversion for the first time is reported. Electrochemistry characterizations and theoretical calculations elucidate that NBSSe tends to form a S+·/Se-· radical pair via intramolecular electron transfer in the co-excited NBSSe* aggregate, realizing 7.25-fold O2 -· generation compared to NBS and 80% suppression of 1O2 generation compared to NBSe. The enhanced O2 -· generation of NBSSe enables excellent anti-hypoxia PDT efficiency and inhibition of pulmonary metastasis. Additionally, the incorporation of electron-rich bovine serum albumin accelerates the recycling of cationic PS radical NBSSe+·, further boosting photostability and O2 -· generation. The resultant BSA@NBSSe nanoparticles demonstrate successful tumor-targeting PDT capability. This work provides an appealing avenue to convert ROS generation from the type II pathway to the type I pathway for efficient cancer phototherapy in hypoxia.

Zwitterionic Photosensitizer-Assembled Nanocluster Produces Efficient Photogenerated Radicals via Autoionization for Superior Antibacterial Photodynamic Therapy

Photodynamic therapy (PDT) holds significant promise for antibacterial treatment, with its potential markedly amplified when using Type I photosensitizers (PSs). However, developing Type I PSs remains a significant challenge due to a lack of reliable design strategy. Herein, a Type I PS nanocluster is developed via self-assembly of zwitterionic small molecule (C3TH) for superior antibacterial PDT in vivo. Mechanism studies demonstrate that unique cross-arranged C3TH within nanocluster not only shortens intermolecular distance but also inhibits intermolecular electronic-vibrational coupling, thus facilitating intermolecular photoinduced electron transfer to form PS radical cation and anion via autoionization reaction. Subsequently, these highly oxidizing or reducing PS radicals engage in cascade photoredox to generate efficient ·OH and O2‾·. As a result, C3TH nanoclusters achieve a 97.6% antibacterial efficacy against MRSA at an ultralow dose, surpassing the efficacy of the commercial antibiotic Vancomycin by more than 8.8-fold. These findings deepen the understanding of Type I PDT, providing a novel strategy for developing Type I PSs.

Creating Single Atomic Coordination for Hypoxia-Resistant Pyroptosis Nano-Inducer to Boost Anti-Tumor Immunotherapy

General synthesis and mechanical understanding of type I nano-photosensitizers are of great importance for hypoxia-resistant pyroptosis inducers. Herein, a simple solvothermal treatment is developed to convert non-photosensitive small molecules (hemin) into uniform carbon nanodots (HNCDs) with strong type I photodynamic activity and red fluorescence emission. These HNCDs inherit the single atomic Fe-N4 center of hemin while creating sp2-hybridized carbon surroundings, which synergistically modulated the energy level and electron transfer for converting the type II photodynamic process to type I. After encapsulating HNCDs with bovine serum albumin (BSA) to facilitate in vivo applications, the resulting BSA nanoparticles (HB) can image tumors and significantly induce the pyroptosis of tumor cells even under an extremely hypoxic environment (2% O2). This evokes a strong antitumor immune response, effectively restraining tumor growth and lung metastasis in triple-negative breast cancer mice, with good biocompatibility. This work introduces an applicable pyroptosis nano-inducer to combat hypoxic tumors and highlights the regulation of Fe-N4 centers to develop hypoxia-resistant type I nano-photosensitizers for cancer treatment.

Advances in Photonic Materials and Integrated Devices for Smart and Digital Healthcare: Bridging the Gap Between Materials and Systems

Recent advances in developing photonic technologies using various materials offer enhanced biosensing, therapeutic intervention, and non-invasive imaging in healthcare. Here, this article summarizes significant technological advancements in materials, photonic devices, and bio-interfaced systems, which demonstrate successful applications for impacting human healthcare via improved therapies, advanced diagnostics, and on-skin health monitoring. The details of required materials, necessary properties, and device configurations are described for next-generation healthcare systems, followed by an explanation of the working principles of light-based therapeutics and diagnostics. Next, this paper shares the recent examples of integrated photonic systems focusing on translation and immediate applications for clinical studies. In addition, the limitations of existing materials and devices and future directions for smart photonic systems are discussed. Collectively, this review article summarizes the recent focus and trends of technological advancements in developing new nanomaterials, light delivery methods, system designs, mechanical structures, material functionalization, and integrated photonic systems to advance human healthcare and digital healthcare.

Near-Infrared Organic Small-Molecule Photosensitizer With O2 Self-Supply for Cancer Photodynamic-Photothermal Synergistic Therapy

Tumor hypoxia and heat resistance as well as the light penetration deficiency severely compromise the phototherapeutic efficacy, developing phototherapeutic agents to overcome these issues has been sought-after goal. Herein, a diradical-featured organic small-molecule semiconductor, namely TTD-CN, has been designed to show low exciton binding energy of 42 meV by unique dimeric π-π aggregation, promoting near-infrared (NIR) absorption beyond 808 nm and effective photo-induced charge separation. More interestingly, its redox potentials are tactfully manipulated for water splitting to produce O2 and reduction of O2 to generate O2 •-. Besides, both ultrafast internal conversion and high-frequency stretching vibrational relaxation of C≡N bonds favor photothermy. Accordingly, TTD-CN nanoparticles have been prepared to exhibit spatiotemporally-synchronous O2 and O2 •- generation and 63.2% photothermal conversion under 808 nm laser irradiation for high-efficient photodynamic and photothermal synergistic therapy. These findings successfully realize NIR light-triggered spatiotemporally-synchronous O2 self-supply, type-I photosensitization and superior photothermy in an organic small-molecule phototherapeutic agent, significantly boosting the development of phototherapy.

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.

Ultrasound/magnetic resonance bimodal imaging-guided CD20-targeted multifunctional nanoplatform for photothermal/chemo synergistic therapy of B-cell lymphoma

B-cell lymphoma has a poor prognosis due to difficulties in early diagnosis and the negative effects of systemic chemotherapy. Therefore, there is an urgent need to develop highly accurate and effective theranostic strategies for B-cell lymphoma. In this study, we designed a poly (lactic-co-glycolic acid) (PLGA)-based theranostic nanoplatform (denoted as TscNPs) to achieve ultrasound (US)/magnetic resonance (MR) bimodal imaging-guided photothermal (PTT)/chemo synergistic therapy of B-cell lymphoma. The nanoplatform was conjugated with a CD20 monoclonal antibody specifically targeting B-cell lymphoma to promote tumor accumulation. Encapsulated superparamagnetic iron oxide nanoparticles (SPIONs) as photothermal and MR imaging agents enabled thermal ablation of tumors and imaging-guided tumor therapy. When exposed to near-infrared (NIR) laser, TscNPs generate heat that induces optical droplet vaporization (ODV) of perfluoropentane (PFP), which transforms into microbubbles. This process not only enhanced ultrasound imaging, but also facilitated the release of celastrol (CST) from the nanoplatform, ultimately achieving a PTT/chemo synergistic therapy effect. In the tumor-bearing nude mice model, TscNPs were effectively accumulated in the tumor region. Furthermore, the combined treatment mode of TscNPs and NIR laser irradiation demonstrated a tumor inhibition rate of approximately 96.57 %, which was significantly superior to the rates observed with PTT or chemotherapy alone. These results suggest that the multifunctional theranostic nanoplatform represents a promising new strategy for the therapy of B-cell lymphoma.

Recent Advances in Strategies to Enhance Photodynamic and Photothermal Therapy Performance of Single-Component Organic Phototherapeutic Agents

Photodynamic therapy (PDT) and photothermal therapy (PTT) have emerged as promising treatment options, showcasing immense potential in addressing both oncologic and nononcologic diseases. Single-component organic phototherapeutic agents (SCOPAs) offer advantages compared to inorganic or multicomponent nanomedicine, including better biosafety, lower toxicity, simpler synthesis, and enhanced reproducibility. Nonetheless, how to further improve the therapeutic effectiveness of SCOPAs remains a challenging research area. This review delves deeply into strategies to improve the performance of PDT or PTT by optimizing the structural design of SCOPAs. These strategies encompass augmenting reactive oxygen species (ROS) generation, mitigating oxygen dependence, elevating light absorption capacity, broadening the absorption region, and enhancing the photothermal conversion efficiency (PCE). Additionally, this review also underscores the ideal strategies for developing SCOPAs with balanced PDT and PTT. Furthermore, the potential synergies are highlighted between PDT and PTT with other treatment modalities such as ferroptosis, gas therapy, chemotherapy, and immunotherapy. By providing a comprehensive analysis of these strategies, this review aspires to serve as a valuable resource for clinicians and researchers, facilitating the wider application and advancement of SCOPAs-mediated PDT and PTT.

Ferroptosis: A novel cell death modality as a synergistic therapeutic strategy with photodynamic therapy

Although there has been significant progress in current comprehensive anticancer treatments centered on surgery, postoperative recurrence and tumor metastasis still significantly affect both prognosis and quality of life of the patient. Hence, the development of precisely targeted tumor therapies and exploration of immunotherapy represent additional strategies for tumor treatment. Photodynamic therapy (PDT) is a relatively safe treatment modality that not only induces multiple modes of tumor cell death but also mediates the secondary immunological responses against tumor resistance and metastasis. Ferroptosis, an iron-dependent type of programmed cell death characterized by accumulation of reactive oxygen species and lipid peroxidation products to lethal levels, has emerged as an attractive target trigger for tumor therapies. Recent research has revealed a close association between PDT and ferroptosis, suggesting that combining ferroptosis inducers with PDT could strengthen their synergistic anti-tumor efficiency. Here in this review, we discuss the rationale for combining PDT with ferroptosis inducers and highlight the progress of single-molecule photosensitizers to induce ferroptosis, as well as the applications of photosensitizers combined with other therapeutic drugs for collaborative therapy. Furthermore, given the current research dilemma, we propose potential therapeutic strategies to advance the combined usage of PDT and ferroptosis inducers, providing the basis and guidelines for prospective clinical translation and research directionality with regard to PDT.

Oxygen-Independent Photodynamic Therapy-Mediated Selective Consumption of M1 Macrophage Against Ventricular Arrhythmias via Sympathetic Neuromodulation

The occurrence of myocardial infarction (MI)-induced malignant ventricular arrhythmias (VAs) is closely associated with the hyperactivation of left stellate ganglion (LSG). Proinflammatory M1 macrophage is reported to aggravate sympathetic overactivation and cause VAs. Therefore, the depletion of M1 macrophage is anticipated to inhibit LSG overactivation and alleviate MI-induced VAs. Herein, oxygen-independent photodynamic therapy (Oi-PDT) combined with M1 macrophage targeting is applied to selectively deplete M1 macrophage in LSG and further treat MI-induced VAs. Oi-PDT, which overcomes the limitation of extremely dependence on oxygen content in traditional PDT, is constructed through the generation of oxidizing photogenerated holes (h+) under the irradiation of near-infrared (NIR) light on the prepared Oi-PDT agent (PPSCD). Meanwhile, PPSCD targets M1 macrophage through conjunction with SR-A receptor. The selective consumption of M1 macrophage is attributed to both apoptosis and ferroptosis induced by h+, 1O2, and O2 •- generated in Oi-PDT. In vivo tests indicated neural activity experienced a notable reduction from 104.5 ±  2.9 to 51.5 ± 6.7 after MI with Oi-PDT treatment, thereby significantly inhibited VAs. The implementation of this study provides a promising strategy for selective consumption of M1 macrophages and treatment of VAs induced by MI.

Finely Tailored Conjugated Small Molecular Nanoparticles for Near-Infrared Biomedical Applications

Near-infrared (NIR) phototheranostics (PTs) show higher tissue penetration depth, signal-to-noise ratio, and better biosafety than PTs in the ultraviolet and visible regions. However, their further advancement is severely hindered by poor performances and short-wavelength absorptions/emissions of PT agents. Among reported PT agents, conjugated small molecular nanoparticles (CSMNs) prepared from D-A-typed photoactive conjugated small molecules (CSMs) have greatly mediated this deadlock by their high photostability, distinct chemical structure, tunable absorption, intrinsic multifunctionality, and favorable biocompatibility, which endows CSMNs with more possibilities in biological applications. This review aims to introduce the recent progress of CSMNs for NIR imaging, therapy, and synergistic PTs with a comprehensive summary of their molecular structures, structure types, and optical properties. Moreover, the working principles of CSMNs are illustrated from photophysical and photochemical mechanisms and light-tissue interactions. In addition, molecular engineering and nanomodulation approaches of CSMs are discussed, with an emphasis on strategies for improving performances and extending absorption and emission wavelengths to the NIR range. Furthermore, the in vivo investigation of CSMNs is illustrated with solid examples from imaging in different scenarios, therapy in 2 modes, and synergistic PTs in combinational functionalities. This review concludes with a brief conclusion, current challenges, and future outlook of CSMNs.

A Near-Infrared II Luminogen with a Photothermal Effect toward Tumor Drug Resistance Reversal

Multidrug resistance of tumor cells has greatly limited the chemotherapy effect. The development of reliable strategies to deal with tumor multidrug resistance is highly desirable for tumor therapy. In this work, a near-infrared II (NIR II) luminogen was rationally designed and prepared, which could act as a photothermal reagent to reverse the drug resistance of tumor cells by reducing the related protein expression, achieving a high inhibition efficiency with the synergistic effect of chemotherapeutic drugs. By the selection of a strong electron-withdrawing unit, the emission peak of the luminogen could reach 973 nm. Moreover, this luminogen shows outstanding photothermal conversion ability and improved thermal stability compared to ICG. Notably, after the photothermal treatment of drug-resistant tumor cells by the NIR II luminogen, the antitumor efficiency of chemotherapeutic drugs, including paclitaxel, cis-platinum, and doxorubicin, was significantly enhanced. The mechanism exploration revealed that drug resistance-related proteins were remarkably reduced, making the cells more sensitive toward drugs. Thus, this strategy demonstrated a promising and reliable approach to reverse the drug resistance of tumor cells for efficient tumor inhibition in the clinic.

Hypoxia-tolerant polymeric photosensitizer prodrug for cancer photo-immunotherapy

Although photodynamic immunotherapy represents a promising therapeutic approach against malignant tumors, its efficacy is often hampered by the hypoxia and immunosuppressive conditions within the tumor microenvironment (TME) following photodynamic therapy (PDT). In this study, we report the design guidelines towards efficient Type-I semiconducting polymer photosensitizer and modify the best-performing polymer into a hypoxia-tolerant polymeric photosensitizer prodrug (HTPSNiclo) for cancer photo-immunotherapy. HTPSNiclo not only performs Type-I PDT process to partially overcome the limitation of hypoxic tumors in PDT by recycling oxygen but also specifically releases a Signal Transducer and Activator of Transcription-3 (STAT3) inhibitor (Niclosamide) in response to a cancer biomarker in the TME. Consequently, HTPSNiclo inhibits the phosphorylation of STAT3, and suppresses the expression of hypoxia-inducible factor-1α. The synergistic effect results in the enhanced activation of immune cells (including mature dendritic cells, cytotoxic T cells) and production of immunostimulatory cytokines compared to Type-I PDT alone. Thus, HTPSNiclo-mediated photodynamic immunotherapy enhances tumor inhibition rate from 75.53% to 91.23%, prolongs the 100% survival from 39 days to 60 days as compared to Type-I PDT alone. This study not only provides the generic approach towards design of polymer-based Type-I photosensitizers but also uncovers effective strategies to counteract the immunosuppressive TME for enhanced photo-immunotherapy in 4T1 tumor bearing female BALB/c mice.

Potent Covalent Organic Framework Nanophotosensitizers with Staggered Type I/II Motifs for Photodynamic Immunotherapy of Hypoxic Tumors

Photodynamic therapy (PDT) using oxygen-dependent type II photosensitizers is frequently limited by the hypoxic microenvironment of solid tumors. Type I photosensitizers show oxygen-independent reactive oxygen species (ROS) generation upon light irradiation but still face the challenges of aggregation-caused quenching (ACQ) and low efficiency to produce ROS. Herein, we first prepare an efficient type I photosensitizer from a perylene derivative via intramolecular donor-acceptor binding and sulfur substitution, which significantly enhance intersystem crossing between singlet and triplet states and electron transfer capability. After reaction with a type II photosensitizer, the covalent organic framework (COF) nanophotosensitizer is formed with alternated type I and II photosensitizer motifs in the same layer and staggered AB stacking between layers to avoid ACQ. The nanophotosensitizer exhibits high-efficiency generation of singlet oxygen (1O2) and superoxide anion radicals (O2•-) via type I and II mechanism under normoxia upon exposure to light irradiation. Under hypoxia, massive O2•- can be produced continuously. The potent ROS generation capability results in efficient cellular apoptosis and immunogenic cell death (ICD) efficiently. After combination with immune checkpoint inhibitors, tumor immunosuppressive microenvironment is reversed, which effectively ablates bulky hypoxic primary tumors and suppresses metastases via photodynamic immunotherapy. The COF nanophotosensitizers with staggered type I and II photosensitizer motifs represent a promising strategy to boost photodynamic immunotherapy of hypoxic tumors.

Understanding the Structural Modulations in Twisted Donor-Acceptor-Donor (D-A-D) Systems for Boosting Type I Photosensitizing Photocatalytic Activity

Supramolecular assemblies based on the twisted donor-acceptor-donor (D-A-D) building block Qx-Ind have been developed, which interestingly, due to the balanced angle of twist (38.28°), high intermolecular charge transfer, and crystallization induced emission (CIE) characteristics, exhibit high molar absorptivity and a long-lived "lighted" excited state at the supramolecular level. The validity of the design concept was examined by preparing CIE active D-A-D system Qx-Indaz (weak donor, low angle of twist: 35.45°), in which, due to the insertion of an additional binding site for noncovalent interactions, a drastic change in the photophysical behavior is observed. The combined spectroscopic studies of all the compounds unveil the strong impact of modulation of the angle of twist and intermolecular charge transfer upon photophysical behavior in the aggregated state. Due to the favorable photophysical behavior, the supramolecular assemblies of Qx-Ind exhibit high type I photosensitizing activity in comparison to Qx-Indaz. The superior type I photosensitizing activity of Qx-Ind assemblies is manifested in their ability to efficiently catalyze the aerobic oxidative synthesis of quinazolin-4(3H)-ones (via type I ROS) from 2-aminobenzamide and aromatic aldehydes in the absence of additional additives (base/oxidant). Unlike photocatalytic nanoassemblies reported in the literature, due to the CIE characteristics, Qx-Ind does not require preliminary preparation and could be directly introduced in the solid state to reaction media. Thus, the present work demonstrates a simple strategy of upgrading type I photosensitizing activity by improving the ground/excited state behavior of a twisted D-A-D system through modulation of the angle of twist and charge transfer characteristics.

Applications of nanotheranostics in the second near-infrared window in bioimaging and cancer treatment

Achieving accurate and efficient tumor imaging is crucial in the field of tumor treatment, as it facilitates early detection and precise localization of tumor tissues, thereby informing therapeutic strategies and surgical interventions. The optical imaging technology within the second near-infrared (NIR-II) window has garnered significant interest for its remarkable benefits, such as enhanced tissue penetration depth, superior signal-to-background ratio (SBR), minimal tissue autofluorescence, reduced photon attenuation, and lower tissue scattering. This review explained the design and optimization strategies of nano-agents responsive to the NIR-II window, such as single-walled carbon nanotubes, quantum dots, lanthanum-based nanomaterials, and noble metal nanomaterials. These nano-agents enable non-invasive, deep-tissue imaging with high spatial resolution in the NIR-II window, and their superior optical properties significantly improve the accuracy, efficiency, and versatility of imaging-guided tumor treatments. And we discussed the characteristics and advantages of fluorescence imaging (FL)/photoacoustic imaging (PA) in NIR-II window, providing a comprehensive overview of the latest research progress of different nano-agents in FL/PA imaging-guided tumor therapy. Furthermore, we exhaustively reviewed the latest applications of multifunctional nano-phototherapy technologies carried out by NIR-II light including photothermal therapy (PTT), photodynamic therapy (PDT), and combined modalities like photothermal-chemodynamic therapy (PTT-CDT), photothermal-chemotherapy (PTT-CT), and photothermal- immunotherapy (PTT-IO). These imaging-guided integrated tumor therapy approaches within the NIR-II window have gradually matured over the past decade and are expected to become a safe and effective non-invasive tumor treatment. Finally, we outlined the prospects and challenges of development and innovation of the NIR-II integrated diagnosis and therapy nanoplatform. This review aims to provide insightful perspectives for future advancements in NIR-II optical tumor diagnosis and integrated treatment platforms.

Synthesis of heavy-atom-free thienoisoindigo dye as near-infrared photosensitizer for type I photodynamic therapy and photoacoustic imaging

Thienoisoindigo (TIIG) has been extensively employed as promising building block of near-infrared (NIR) dyes and organic semiconductor materials. Herein, heavy-atom-free TIIG-based NIR dye TIIGTPA is reported as photosensitizer for combinational photodynamic and photothermal therapy and photoacoustic imaging (PAI). By introducing two methoxy-substituted triphenylamines as the rotors and electron donors at the periphery sites of the electron-deficient TIIG core, dye TIIGTPA featuring Donor-Acceptor-Donor (D-AD) structure is constructed with intensive NIR absorption. Through co-assembly with amphipathic F-127, water-soluble TIIGTPA NPs were prepared with good superoxide anion radical (O2-•) production and high photothermal conversion efficiency (PCE) of 59.0 % under 730 nm photoirradiation. Additionally, the excellent photothermal effect enabled a superior photoacoustic response for tumor blood vessel visualization through PAI. All results indicated the favorable potential of TIIGTPA NPs for PAI-mediated combinational phototherapy.

Recent advances in nanoagents delivery system-based phototherapy for osteosarcoma treatment

Osteosarcoma (OS) is a prevalent and highly malignant bone tumor, characterized by its aggressive nature, invasiveness, and rapid progression, contributing to a high mortality rate, particularly among adolescents. Traditional treatment modalities, including surgical resection, radiotherapy, and chemotherapy, face significant challenges, especially in addressing chemotherapy resistance and managing postoperative recurrence and metastasis. Phototherapy (PT), encompassing photodynamic therapy (PDT) and photothermal therapy (PTT), offers unique advantages such as low toxicity, minimal drug resistance, selective destruction, and temporal control, making it a promising approach for the clinical treatment of various malignant tumors. Constructing multifunctional delivery systems presents an opportunity to effectively combine tumor PDT, PTT, and chemotherapy, creating a synergistic anti-tumor effect. This review aims to consolidate the progress in the application of novel delivery system-mediated phototherapy in osteosarcoma. By summarizing advancements in this field, the objective is to propose a rational combination therapy involving targeted delivery systems and phototherapy for tumors, thereby expanding treatment options and enhancing the prognosis for osteosarcoma patients. In conclusion, the integration of innovative delivery systems with phototherapy represents a promising avenue in osteosarcoma treatment, offering a comprehensive approach to overcome challenges associated with conventional treatments and improve patient outcomes.

De novo design of type-l photosensitizer agents based on structure-inherent low triplet energy for hypoxia photodynamic therapy

Photodynamic therapy (PDT), owing to its low invasiveness, high efficiency, fewer side effects, spatiotemporal controllability and good selectivity, has attracted increasing attention for its tremendous potential in revolutionizing conventional strategies of tumor treatment. However, hypoxia is a common feature of most malignancies and has become the Achilles' heel of PDT. Currently, Type II photosensitizers (PSs) have inadequate efficacy for PDT due to the inherent oxygen consumption of the anoxic tumor microenvironment. Moreover, due to the absence of a general molecular design strategy and the limitations imposed by the energy gap law, Type-I PSs are less reported. Therefore, the development of Type-I PSs with hypoxia resistant capabilities is urgently required. Herein, in this study, we have obtained pure Type-I materials for the first time by employing a strategy that decreases the triplet energy levels of the π-conjunction bridge. A sufficient donor-acceptor interaction reduces the lowest triplet energy level and aids in the transfer of excitons from singlet to triplet levels. With this strategy, dibenzofulvene derivatives (FEs) displayed purely Type-I ROS generation. Among them, FE-TMI exhibits superior Type-I reactive oxygen species-generation performance, showcasing the great potential of PDT in treating tumor cells under hypoxic conditions and several types of solid tumors in mouse in vivo experiments. This work provides a practical solution for the future design of Type-I PDT materials and is aimed at enhancing PDT efficiency.

A simple hydrogen peroxide-activatable Bodipy for tumor imaging and type I/II photodynamic therapy

Tumor microenvironment-activatable photosensitizers have gained significant attention for cancer theranostics. Considering the hypoxic environment of solid tumors, activatable phototheranostic agents with type I PDT are desired to obtain improved cancer treatment efficiency. Herein, we report a simple, effective and multifunctional Bodipy photosensitizer for tumor imaging and type I/II photodynamic therapy. The photosensitizer featuring a methylphenylboronic acid pinacol ester group at the meso-position of Bodipy specifically responds to tumor-abundant H2O2. Its photophysical properties were characterized using steady-state and time-resolved transient optical spectroscopies. The fluorescence (ΦF = 0.09%) and singlet oxygen efficacy (ΦΔ = 10.2%) of the Bodipy units were suppressed in the caged dyads but significantly enhanced (ΦF = 0.72%, ΦΔ = 20.3%) upon H2O2 activation. Fluorescence emission spectroscopy and continuous wave electron paramagnetic resonance (EPR) spectroscopy confirmed that the Bodipy photosensitizer generates reactive oxygen species (ROS) via both electron transfer-mediated type I and energy transfer-mediated type II mechanisms. In vitro experiments demonstrated rapid internalization into tumor cells, enhanced brightness stimulated by tumor microenvironments, and tumor cell death (phototoxicity, IC50 = 0.5 μM). In vivo fluorescence imaging indicated preferential accumulation of this Bodipy photosensitizer in tumor sites, followed by decaging by tumor-abundant H2O2, further elevating the signal-to-background ratio (SBR) of imaging. Besides outstanding performance in tumor imaging, a prominent inhibition of tumor growth was observed. Given its simple molecular skeleton, this Bodipy photosensitizer is a competitive candidate for cancer theranostics.

Photoimmunotherapy for cancer treatment based on organic small molecules: Recent strategies and future directions

Photodynamic therapy (PDT) is considered as a promising anticancer approach, owning to its high efficiency and spatiotemporal selectivity. Ample evidence indicated that PDT can trigger immunogenic cell death by releasing antigens that activate immune cells to promote anti-tumor immunity. Nevertheless, the inherent nature of tumors and their complex heterogeneity often limits the efficiency of PDT, which can be overcome with a novel strategy of photo-immunotherapy (PIT) strategy. By exploring the principles of PDT induction and ICD enhancement, combined with other therapies such as chemotherapy or immune checkpoint blockade, the tailored solutions can be designed to address specific challenges of drug resistance, hypoxic conditions, and tumor immunosuppressive microenvironments (TIMEs), which enables targeted enhancement of systemic immunity to address most distant and recurrent cancers. The present article summarizes the specific strategies of PIT and discusses recent existing limitations. More importantly, we anticipate that the perspectives presented herein will help address the clinical translation challenges associated with PIT.

Multifunctional NIR-II nanoplatform for disrupting biofilm and promoting infected wound healing

Healing wounds presents a significant challenge due to bacterial biofilm infections and the inherent drug resistance of these biofilms. This report introduces a multifunctional nanoplatform (NPs) designed to combat wound biofilm infections using NIR-II photothermal therapy. The NPs are self-assembled from amphiphilic polymers (AP) to encapsulate photothermal polymers (PT) through classic electrostatic interactions. Importantly, these NPs are electrically neutral, which enhances their ability to penetrate biofilms effectively. Once inside the biofilm, the NPs achieve complete thermal ablation of the biofilm under NIR-II laser irradiation. Additionally, when exposed to laser and the GSH microenvironment, the NPs exhibit strong photothermal effects and self-degradation capabilities. In vitro tests confirm that the NPs have excellent antibacterial and anti-biofilm properties against methicillin-resistant Staphylococcus aureus (MRSA). In vivo studies demonstrate that the NPs can efficiently clear wound biofilm infections and promote wound healing. Notably, the NPs show superior photothermal effects under NIR-II laser irradiation compared to NIR-I lasers. In summary, the developed NPs serve as an integrated diagnostic and therapeutic nano-antimicrobial agent, offering promising applications for biofilm wound infections and wound healing.

Recent advances in biomaterials based near-infrared mild photothermal therapy for biomedical application: A review

Mild photothermal therapy (MPTT) generates heat therapeutic effect at the temperature below 45 °C under near-infrared (NIR) irradiation, which has the advantages of controllable treatment efficacy, lower hyperthermia temperatures, reduced dosage, and minimized damage to surrounding tissues. Despite significant progress has been achieved in MPTT, it remains primarily in the stage of basic and clinical research and has not yet seen widespread clinical adoption. Herein, a comprehensive overview of the recent NIR MPTT development was provided, aiming to emphasize the mechanism and obstacles, summarize the used photothermal agents, and introduce various biomedical applications such as anti-tumor, wound healing, and vascular disease treatment. The challenges of MPTT were proposed with potential solutions, and the future development direction in MPTT was outlooked to enhance the prospects for clinical translation.

Piezoelectric Bilayer Nickel-Iron Layered Double Hydroxide Nanosheets with Tumor Microenvironment Responsiveness for Intensive Piezocatalytic Therapy

Piezocatalytic therapy (PCT) based on 2D layered materials has emerged as a promising non-invasive tumor treatment modality, offering superior advantages. However, a systematic investigation of PCT, particularly the mechanisms underlying the reactive oxygen species (ROS) generation by 2D nanomaterials, is still in its infancy. Here, for the first time, biodegradable piezoelectric 2D bilayer nickel-iron layered double hydroxide (NiFe-LDH) nanosheets (thickness of ≈1.86 nm) are reported for enhanced PCT and ferroptosis. Under ultrasound irradiation, the piezoelectric semiconducting NiFe-LDH exhibits a remarkable ability to generate superoxide anion radicals, due to the formation of a built-in electric field that facilitates the separation of electrons and holes. Notably, the significant excitonic effect in the ultrathin NiFe-LDH system enables long-lived excited triplet excitons (lifetime of ≈5.04 µs) to effectively convert triplet O2 molecules into singlet oxygen. Moreover, NiFe-LDH exhibited tumor microenvironment (TME)-responsive peroxidase (POD)-like and glutathione (GSH)-depleting capabilities, further enhancing oxidative stress in tumor cells and inducing ferroptosis. To the best of knowledge, this is the first report on piezoelectric semiconducting sonosensitizers based on LDHs for PCT and ferroptosis, providing a comprehensive understanding of the piezocatalysis mechanism and valuable references for the application of LDHs and other 2D materials in cancer therapy.

Biomimetic Gold Nanorods-Manganese Porphyrins with Surface-Enhanced Raman Scattering Effect for Photoacoustic Imaging-Guided Photothermal/Photodynamic Therapy

Surface-enhanced Raman scattering (SERS) imaging integrating photothermal and photodynamic therapy (PTT/PDT) is a promising approach for achieving accurate diagnosis and effective treatment of cancers. However, most available Raman reporters show multiple signals in the fingerprint region, which overlap with background signals from cellular biomolecules. Herein, a 4T1 cell membrane-enveloped gold nanorods-manganese porphyrins system (GMCMs) is designed and successfully fabricated as a biomimetic theranostic nanoplatform. Manganese porphyrins are adsorbed on the surface of Au nanorods via the terminal alkynyl group. Cell membrane encapsulation protects the manganese porphyrins from falling off the gold nanorods. The biomimetic GMCMs confirm specific homologous targeting to 4T1 cells with good dispersibility, excellent photoacoustic (PA) imaging properties, and preferable photothermal and 1O2 generation performance. GMCMs exhibit distinct SERS signals in the silent region without endogenous biomolecule interference both in vitro and in vivo. Manganese ions could not only quench the fluorescence of porphyrins to enhance the SERS imaging effect but also deplete cellular GSH to increase 1O2 yield. Both in vitro and in vivo studies demonstrate that GMCMs effectively eradicate tumors through SERS/PA imaging-guided PTT/PDT. This study provides a feasible strategy for augmenting the Raman imaging effects of the alkynyl group and integrating GSH-depletion to enhance PTT/PDT efficacy.

An Active Self-Mitochondria-Targeting Cyanine Immunomodulator for Near-Infrared II Fluorescence Imaging-Guided Synergistic Photodynamic Immunotherapy

Photodynamic therapy targeting mitochondria represents a promising therapeutic strategy for fighting diverse types of cancers. However, the currently available photosensitizers (PSs) suffer from insufficient therapeutic potency, limited mitochondria delivery efficiency, and the inability to treat invisible metastatic distal cancers. Herein, an active self-mitochondria-targeting heptapeptide cyanine (HCy) immunomodulator (I2HCy-QAP) is reported for near-infrared II (NIR-II) fluorescence imaging-guided photodynamic immunotherapy of primary and distal metastatic cancers. The I2HCy-QAP is designed by introducing a quaternary ammonium salt with a phenethylamine skeleton (QAP) into the iodinated HCy photosensitizer. The I2HCy-QAP can precisely target mitochondria due to the lipophilic cationic QAP unit, present strong NIR-II fluorescence tail emission, and effectively generate singlet oxygen 1O2 under NIR laser irradiation, thereby inducing mitochondria-targeted damages and eliciting strong systemic immunogenic cell death immune responses. The combination of the I2HCy-QAP-mediated photodynamic immunotherapy with anti-programmed death-1 antibody therapy achieves remarkable therapeutic efficacy against both primary and distal metastatic cancers with significant inhibition of lung metastasis in a triple-negative breast cancer model. This work provides a new concept for designing high-performance NIR emissive cyanine immunomodulators for NIR-II fluorescence-guided photodynamic immunotherapy.

Supramolecular H-Aggregates of Squaraines with Enhanced Type I Photosensitization for Combined Photodynamic and Photothermal Therapy

Combined photodynamic and photothermal therapy (PDT and PTT) can achieve more superior therapeutic effects than the sole mode by maximizing the photon utilization, but there remains a significant challenge in the development of related single-molecule photosensitizers (PSs), particularly those with type I photosensitization. In this study, self-assembly of squaraine dyes (SQs) is shown to be a promising strategy for designing PSs for combined type I PDT and PTT, and a supramolecular PS (TPE-SQ7) has been successfully developed through subtle molecular design of an indolenine SQ, which can self-assemble into highly ordered H-aggregates in aqueous solution as well as nanoparticles (NPs). In contrast to the typical quenching effect of H-aggregates on reactive oxygen species (ROS) generation, our results encouragingly manifest that H-aggregates can enhance type I ROS (•OH) generation by facilitating the intersystem crossing process while maintaining a high PTT performance. Consequently, TPE-SQ7 NPs with ordered H-aggregates not only exhibit superior combined therapeutic efficacy than the well-known PS (Ce6) under both normoxic and hypoxic conditions but also have excellent biosafety, making them have important application prospects in tumor phototherapy and antibacterial fields. This study not only proves that the supramolecular self-assembly of SQs is an effective strategy toward high-performance PSs for combined type I PDT and PTT but also provides a different understanding of the effect of H-aggregates on the PDT performance.

Sonodynamic Therapy-Driven Immunotherapy: Constructing AIE Organic Sonosensitizers Using an Advanced Receptor-Regulated Strategy

Benefit from the deeper penetration of mechanical wave, ultrasound (US)-based sonodynamic therapy (SDT) executes gratifying efficacy in treating deep-seated tumors. Nevertheless, the complicated mechanism of SDT undeniably hinders the exploration of ingenious sonosensitizers. Herein, a receptor engineering strategy of aggregation-induced emission (AIE) sonosensitizers (TPA-Tpy) with acceptor (A)-donor (D)-A' structure is proposed, which inspects the effect of increased cationizations on US sensitivity. Under US stimulation, enhanced cationization in TPA-Tpy improves intramolecular charge transfer (ICT) and accelerates charge separation, which possesses a non-negligible promotion in type I reactive oxygen species (ROS) production. Moreover, abundant ROS-mediated mitochondrial oxidative stress triggers satisfactory immunogenic cell death (ICD), which further promotes the combination of SDT and ICD. Subsequently, subacid pH-activated nanoparticles (TPA-Tpy NPs) are constructed with charge-converting layer (2,3-dimethylmaleic anhydride-poly (allylamine hydrochloride)-polyethylene glycol (DMMA-PAH-PEG)) and TPA-Tpy, achieving the controllable release of sonosensitizers. In vivo, TPA-Tpy-mediated SDT effectively initiates the surface-exposed of calreticulin (ecto-CRT), dendritic cells (DCs) maturation, and CD8+ T cell infiltration rate through enhanced ROS production, achieving suppression and ablation of primary and metastatic tumors. This study provides new opinions in regulating acceptors with eminent US sensitization, and brings a novel ICD sono-inducer based on SDT to realize superior antitumor effect.

High-Performance NIR-II Fluorescent Type I/II Photosensitizer Enabling Augmented Mild Photothermal Therapy of Tumors by Disrupting Heat Shock Proteins

NIR-II fluorescent photosensitizers as phototheranostic agents hold considerable promise in the application of mild photothermal therapy (MPTT) for tumors, as the reactive oxygen species generated during photodynamic therapy can effectively disrupt heat shock proteins. Nevertheless, the exclusive utilization of these photosensitizers to significantly augment the MPTT efficacy has rarely been substantiated, primarily due to their insufficient photodynamic performance. Herein, the utilization of high-performance NIR-II fluorescent type I/II photosensitizer (AS21:4) is presented as a simple but effective nanoplatform derived from molecule AS2 to enhance the MPTT efficacy of tumors without any additional therapeutic components. By taking advantage of heavy atom effect, AS21:4 as a type I/II photosensitizer demonstrates superior efficacy in producing 1O2 (1O2 quantum yield = 12.4%) and O2 •- among currently available NIR-II fluorescent photosensitizers with absorption exceeding 800 nm. In vitro and in vivo findings demonstrate that the 1O2 and O2 •- generated from AS21:4 induce a substantial reduction in the expression of HSP90, thereby improving the MPTT efficacy. The remarkable phototheranostic performance, substantial tumor accumulation, and prolonged tumor retention of AS21:4, establish it as a simple but superior phototheranostic agent for NIR-II fluorescence imaging-guided MPTT of tumors.

Selective Tumor Inhibition Effect of Drug-Free Layered Double Hydroxide-Based Films via Responding to Acidic Microenvironment

Nickel-titanium alloy stents are widely used in the interventional treatment of various malignant tumors, and it is important to develop nickel-titanium alloy stents with selective cancer-inhibiting and antibacterial functions to avoid malignant obstruction caused by tumor invasion and bacterial colonization. In this work, an acid-responsive layered double hydroxide (LDH) film was constructed on the surface of a nickel-titanium alloy by hydrothermal treatment. The release of nickel ions from the film in the acidic tumor microenvironment induces an intracellular oxidative stress response that leads to cell death. In addition, the specific surface area of LDH nanosheets could be further regulated by heat treatment to modulate the release of nickel ions in the acidic microenvironment, allowing the antitumor effect to be further enhanced. This acid-responsive LDH film also shows a good antibacterial effect against S. aureus and E. coli. Besides, the LDH film prepared without the introduction of additional elements maintains low toxicity to normal cells in a normal physiological environment. This work offers some guidance for the design of a practical nickel-titanium alloy stent for the interventional treatment of tumors.

In situ self-assembled near-infrared phototherapeutic agent: unleashing hydrogen free radicals and coupling with NADPH oxidation

Investigation of electron transfer (ET) between photosensitizers (PSs) and adjacent substrates in hypoxic tumors is integral to highly efficient tumor therapy. Herein, the oxygen-independent ET pathway to generate hydrogen free radicals (H˙) was established by the in situ self-assembled phototherapeutic agent d-ST under near-infrared (NIR)-light irradiation, coupled with the oxidation of reduced coenzyme NADPH, which induced ferroptosis and effectively elevated the therapeutic performance in hypoxic tumors. The higher surface energy and longer exciton lifetimes of the fine crystalline d-ST nanofibers were conducive to improving ET efficiency. In hypoxic conditions, the excited d-ST can effectively transfer electrons to water to yield H˙, during which the overexpressed NADPH with rich electrons can power the electron flow to facilitate the generation of H˙, accompanied by NADP+ formation, disrupting cellular homeostasis and triggering ferroptosis. Tumor-bearing mouse models further showed that d-ST accomplished excellent phototherapy efficacy. This work sheds light onto the versatile electron pathways between PSs and biological substrates.

A NIR-II absorbing conjugated polymer based on tetra-fused isoindigo with ultrahigh photothermal conversion efficiency for cancer therapy

A conjugated polymer, P4TTD-DPP, based on tetra-fused isoindigo-alt-diketopyrrolopyrrole, has been synthesized as a photothermal therapeutic nanotransducer within the near-infrared-II (NIR-II) window. P4TTD-DPP exhibits a notable mass extinction coefficient of 62.8 L g-1 cm-1 at 1064 nm. Additionally, P4TTD-DPP nanoparticles demonstrate remarkable photothermal conversion efficiency of 91.5% at 1064 nm and exhibit excellent anticancer efficacy under photothermal conditions.

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.

Confined semiconducting polymers with boosted NIR light-triggered H2O2 production for hypoxia-tolerant persistent photodynamic therapy

Hypoxia featured in malignant tumors and the short lifespan of photo-induced reactive oxygen species (ROS) are two major issues that limit the efficiency of photodynamic therapy (PDT) in oncotherapy. Developing efficient type-I photosensitizers with long-term ˙OH generation ability provides a possible solution. Herein, a semiconducting polymer-based photosensitizer PCPDTBT was found to generate 1O2, ˙OH, and H2O2 through type-I/II PDT paths. After encapsulation within a mesoporous silica matrix, the NIR-II fluorescence and ROS generation are enhanced by 3-4 times compared with the traditional phase transfer method, which can be attributed to the excited-state lifetime being prolonged by one order of magnitude, resulting from restricted nonradiative decay channels, as confirmed by femtosecond spectroscopy. Notably, H2O2 production reaches 15.8 μM min-1 under a 730 nm laser (80 mW cm-2). Further adsorption of Fe2+ ions on mesoporous silica not only improves the loading capacity of the chemotherapy drug doxorubicin but also triggers a Fenton reaction with photo-generated H2O2 in situ to produce ˙OH continuously after the termination of laser irradiation. Thus, semiconducting polymer-based nanocomposites enables NIR-II fluorescence imaging guided persistent PDT under hypoxic conditions. This work provides a promising paradigm to fabricate persistent photodynamic therapy platforms for hypoxia-tolerant phototheranostics.