A H2O2 responsive self-activatable fluorescent probe and pro-photosensitizer based on a pyridine-chalcone skeleton

Hydrogen peroxide (H2O2) is closely associated with various physiological and pathological processes, particularly in tumor microenvironment. It has been designed for the activation and release of fluorescent probes and tumor-related drugs. In this work, we proposed a self-activatable fluorescent probe and pro-photosensitizer (pro-PS) MN-BP based on a pyridine-chalcone photosensitizer (PS) MN and a H2O2 responsive boronate moiety. The endogenous H2O2 in tumor cells triggers partial release of PS MN from the pro-PS MN-BP. Under light irradiation, the generated PS MN can produce Reactive oxygen species (ROS) and be partially converted to H2O2 to proceed the self-activatable process. The generated H2O2 can be used as an activator to accelerate the release of PS MN, thus amplifying the effect of photodynamic therapy (PDT) by generating more ROS. In addition, the enhanced fluorescence of pro-PS MN-BP can be used for the detection of H2O2 and the visualization of photosensitizer, so as to realize the real-time monitoring and regulation of the PDT process.

Switchable Nanophotosensitizers as Pyroptosis Inducers for Targeted Boosting of Antitumor Photoimmunotherapy

Photodynamic therapy (PDT) has emerged as a promising modality for cancer treatment, but its clinical application is constrained by unexpected phototoxicity arising from nonspecific photosensitizer activation and their "always-on" nature. Herein, we developed a switchable nanophotosensitizer, poly(cation-π) nanoparticles (NP), which achieves supramolecular assembly through cation-π interactions. By coupling choline cationic moieties with aromatic photosensitizers (ZnPc), the polymer facilitates self-assembly driven by cation-π interactions for NP engineering. Surprisingly, the photoactivity of ZnPc was completely quenched upon complexation via cation-π interactions, thereby significantly avoiding skin phototoxicity. Upon targeting tumor cells, NP undergoes a GSH-responsive degradation process that weakens cation-π interactions, leading to spontaneous restoration of photoactivity and amplifying tumor immunogenic pyroptosis. In vivo studies demonstrated that NP achieved a high tumor inhibition rate of 84% while effectively avoiding skin phototoxicity. This work provides a novel perspective for enhancing the safety and efficacy of PDT-based tumor treatment.

Next generation of porphysomes for improved photodynamic therapy applications

Porphysomes are a class of liposome-like nanoparticles that have demonstrated efficacy in photothermal therapy (PTT) and photodynamic therapy (PDT) against cancer. These nanoparticles results from the self-assembly of amphiphilic phospholipid-porphyrin (PL-Por) conjugates. Despite their potential, porphysomes exhibit a high photothermal effect and a weak photodynamic activity as long as they remain intact within the body. In this study, we present the design of a novel generation of smart porphysomes capable of undergoing active dissociation and releasing porphyrin moieties upon illumination, thereby enabling tunable photothermal properties with enhanced photodynamic efficiency. These new porphysomes are composed of smart PL-Por conjugates that exhibit one or two ROS-responsive linkers separating the polar head group from the porphyrin moiety. Among the designed molecules, we demonstrated that monosubstituted conjugates bearing either pyro-a or pheo-a porphyrinoids with one ROS-responsive bond and shorter linker showed the best performance in terms of stability, photothermal and photodynamic efficiencies in vitro. Moreover, these assemblies were found to achieve complete tumor ablation in 80 % of PC3 prostate subcutaneous tumor-bearing mice after 30 days post-PDT, compared to 0 % using conventional porphysomes. Consequently, our strategy enabled the development of a versatile platform for delivering porphyrin-based photosensitizers for enhanced photodynamic applications.

Photoacoustic contrast agents: a review focusing on image-guided therapy

Photoacoustic (PA) imaging is a burgeoning imaging modality that has a broad range of applications in the early diagnosis of cancer, detection of various diseases, and relevant scientific research. It is a non-invasive imaging modality that relies on the absorption coefficient of the imaging tissue and the injected PA-imaging contrast agent. Nevertheless, PA imaging exhibits weak imaging depth due to its exponentially decaying signal intensity with increasing tissue depth. To improve the depth and heighten the contrast of imaging, a series of PA contrast agents has been developed based on nanomaterials. In this review, we present a comprehensive overview of recent advancements in contrast agents for photoacoustic (PA) imaging, encompassing the emergence of first near-infrared region (NIR-I, 700-950 nm) PA contrast agents, second near-infrared region (NIR-II, 1000-1700 nm) PA contrast agents, and ratiometric PA contrast agents. Subsequently, the latest advances in PA image-guided cancer therapy were introduced, such as photothermal therapy (PTT), photodynamic therapy (PDT), sonodynamic therapy (SDT), and PTT-based synergistic therapy. Finally, the prospects of PA contrast agents and their biomedical applications were also discussed. This review provides a systematic summary of the development and utilization of the cutting-edge photoacoustic agents, which may inspire fresh thinking in the fabrication and application aspects of imaging agents.

SIM imaging of bacterial membrane dynamics and lipid peroxidation during photodynamic inactivation with a dual-functional activatable probe

Photodynamic inactivation (PDI) has emerged as a promising antibacterial strategy that mitigates the risk of bacterial resistance. However, the precise morphological dynamics and mechanisms underlying bacterial cell death during PDI remain insufficiently understood. In this study, we developed a dual-functional activatable probe, RDP, which integrated rhodamine B as a fluorophore with moderate brightness and fatty chains for selective bacterial membrane localization. The probe employed an aggregation-disaggregation mechanism to achieve both fluorescence activation and PDI functionality. Using super-resolution fluorescence imaging, we unveiled the selective rupture of bacterial membranes at specific sites during PDI, followed by membrane contraction and internalization, ultimately leading to the formation of lipid-enriched droplets within the bacteria. Further mechanistic investigations confirmed that this membrane rupture was driven by lipid peroxidation. Statistical analysis of bacterial morphological changes during PDI revealed that membrane rupture predominantly occurred at the septum during cell division, whereas in other growth phases, rupture sites were mainly localized at the poles. These findings provide critical insights into the role of selective membrane rupture in bacterial growth and viability, paving the way for the rational design of targeted and highly efficient antibacterial agents.

A simple co-assembly strategy to control the dimensions of nanoparticles for enhanced synergistic therapy

Despite phthalocyanine has excellent photodynamic and photothermal effects as a photosensitizer and photothermal agent, hydrophobicity and aggregation limits its biological application. In this paper, phthalocyanine-cyanine co-assembled nanoparticles were designed to modulate the dimensions and morphology by introducing water-soluble cyanine. The cyanine had the ability to transform the nanomaterials from microrods to nanospheres, thus successfully constructing photoactivated nanomedicines. Their appropriate size effect and improved water solubility conferred the nanoparticles with extended blood circulation time and tumor accumulation capacity. Meanwhile, the fluorescence effect of cyanine enabled the nanoparticles to have the ability of fluorescence imaging. The nanoparticles achieved enhanced PDT/PTT synergistic effect under single laser induction, especially the generation of type I photodynamics.

Improved Orthogonality in Naphthalimide/Cyanine Dyad Boosts Superoxide Generation: a Tumor-Targeted Type-I Photosensitizer for Photodynamic Therapy of Tumor by Inducing Ferroptosis

It is highly desired to achieve Type-I photosensitizer (PS) to overcome the hypoxic limitation found in most clinically used PSs. Herein, a new heavy-atom-free Type-I PS T-BNCy5 is presented by incorporating a biotin-modified naphthalimide (NI) unit into the meso-position of a N-benzyl-functionalized, strongly photon-capturing pentamethine cyanine (Cy5) dye. Such molecular engineering induces a rigid orthogonal geometry between NI and Cy5 units by introducing an intramolecular sandwich-like π-π stacking assembly, which effectively promotes intersystem crossing (ISC) and greatly extends the triplet-state lifetime (τ = 389 µs), thereby markedly improving the superoxide (O2 •-)-generating ability. In vitro assays reveal that T-BNCy5 specifically accumulates in mitochondria, where it not only generates O2 •- under photoirradiation but also induces the burst of the most cytotoxic hydroxy radical (HO•) by a cascade of biochemical reactions, ultimately triggering cell ferroptosis with the IC50 value up to ≈0.45 µm whether under normoxia or hypoxia. In vivo assays manifest that, benefiting from its biotin unit, T-BNCy5 displays a strong tumor-targeting ability, and after a single PDT treatment, it can not only ablate the tumor almost completely but also be cleared from the body through biosafe urinary excretion, indicating its potential for future clinical translation.

NIR-II Photosensitizer-Based Nanoparticles Defunctionalizing Mitochondria to Overcome Tumor Self-Defense by Promoting Heat Shock Protein 40

Inherent self-defense pathways within malignant tumors include the action of heat shock proteins (HSPs) and often impede photothermal therapy efficacy. Interestingly, HSP40 inhibits glycolysis and disrupts mitochondrial function to overcome tumor self-defense mechanisms and exhibits a tumor-suppressive effect. Reactive oxygen species (ROS), especially hydroxyl radicals, generated by type-I photodynamic therapy inhibit adenosine triphosphate (ATP) production and lead to ATP-independent HSP40 overexpression during heat stress. However, the regulatory mechanisms linking heat and hydroxyl radicals to induce HSP40 expression remain unclear. Therefore, it is imperative to elucidate the underlying mechanism governing the induction of HSP40 expression during heat stress and explore its potential as a promising therapeutic strategy against tumor development. By strategically modifying the aza-BODIPY structure to precisely distribute the excited-state energy, we have demonstrated that HSP40 specific expression is correlated with the proportion of heat to hydroxyl radicals rather than their individual levels. This orchestrated NIR-II photosensitizer-based nanoparticles reduced tumor glycolysis and disrupted ATP production, driving cell apoptosis and amplifying the efficacy of photothermal therapy. Silencing and compensation of HSPs under heat and ROS stress represent a promising and effective strategy for overcoming tumor self-defense mechanisms in cancer therapy.

Transforming malignant tumors into vulnerable phenotypes via nanoscale coordination polymer mediated cell senescence and photodynamic therapy

Induction of senescence in cancer cells can thwart the proliferation of malignant tumors. Herein we report the design of AZT-P/pyro nanoscale coordination polymer particles consisting of 3-azido-2,3-dideoxythymidine monophosphate (AZT-P) in the core and photosensitizing pyro-lipid (pyro) in the shell for potent antitumor treatment. Gradual release of AZT-P in response to an acidic tumor microenvironment transforms cancer cells with unlimited proliferation capacity into senescent cells that are vulnerable to reactive oxygen species (ROS). Pyro selectively induces ROS generation and immunogenic cell death of cancer cells upon light irradiation. Co-delivery of AZT-P and pyro in a single particle prolongs their blood circulation times and enhances their accumulation in tumors. Additionally, the induction of senescence and ROS generation both contribute to the recruitment of immune cells to the tumors, resulting in an effective immune response to inhibit the growth of large subcutaneous tumors and metastatic spread of orthotopic tumors.

Activatable Photosensitizers: From Fundamental Principles to Advanced Designs

Photodynamic therapy (PDT) is a promising treatment that uses light to excite photosensitizers in target tissue, producing reactive oxygen species and localized cell death. It is recognized as a minimally invasive, clinically approved cancer therapy with additional preclinical applications in arthritis, atherosclerosis, and infection control. A hallmark of ideal PDT is delivering disease-specific cytotoxicity while sparing healthy tissue. However, conventional photosensitizers often suffer from non-specific photoactivation, causing off-target toxicity. Activatable photosensitizers (aPS) have emerged as more precise alternatives, offering controlled activation. Unlike traditional photosensitizers, they remain inert and photoinactive during circulation and off-target accumulation, minimizing collateral damage. These photosensitizers are designed to "turn on" in response to disease-specific biostimuli, enhancing therapeutic selectivity and reducing off-target effects. This review explores the principles of aPS, including quenching mechanisms stemming from activatable fluorescent probes and applied to activatable photosensitizers (RET, PeT, ICT, ACQ, AIE), as well as pathological biostimuli (pH, enzymes, redox conditions, cellular internalization), and bioresponsive constructs enabling quenching and activation. We also provide a critical assessment of unresolved challenges in aPS development, including limitations in targeting precision, selectivity under real-world conditions, and potential solutions to persistent issues (dual-lock, targeting moieties, biorthogonal chemistry and artificial receptors). Additionally, it provides an in-depth discussion of essential research design considerations needed to develop translationally relevant aPS with improved therapeutic outcomes and specificity.

Phototherapy in cancer treatment: strategies and challenges

Phototherapy has emerged as a promising modality in cancer treatment, garnering considerable attention for its minimal side effects, exceptional spatial selectivity, and optimal preservation of normal tissue function. This innovative approach primarily encompasses three distinct paradigms: Photodynamic Therapy (PDT), Photothermal Therapy (PTT), and Photoimmunotherapy (PIT). Each of these modalities exerts its antitumor effects through unique mechanisms-specifically, the generation of reactive oxygen species (ROS), heat, and immune responses, respectively. However, significant challenges impede the advancement and clinical application of phototherapy. These include inadequate ROS production rates, subpar photothermal conversion efficiency, difficulties in tumor targeting, and unfavorable physicochemical properties inherent to traditional phototherapeutic agents (PTs). Additionally, the hypoxic microenvironment typical of tumors complicates therapeutic efficacy due to limited agent penetration in deep-seated lesions. To address these limitations, ongoing research is fervently exploring innovative solutions. The unique advantages offered by nano-PTs and nanocarrier systems aim to enhance traditional approaches' effectiveness. Strategies such as generating oxygen in situ within tumors or inhibiting mitochondrial respiration while targeting the HIF-1α pathway may alleviate tumor hypoxia. Moreover, utilizing self-luminescent materials, near-infrared excitation sources, non-photoactivated sensitizers, and wireless light delivery systems can improve light penetration. Furthermore, integrating immunoadjuvants and modulating immunosuppressive cell populations while deploying immune checkpoint inhibitors holds promise for enhancing immunogenic cell death through PIT. This review seeks to elucidate the fundamental principles and biological implications of phototherapy while discussing dominant mechanisms and advanced strategies designed to overcome existing challenges-ultimately illuminating pathways for future research aimed at amplifying this intervention's therapeutic efficacy.

Supramolecular gels for antimicrobial photodynamic therapy against E. coli and S. aureus

Singlet oxygen (SO) reacts with organic molecules, for example in degrading environmental contaminants and causing toxicity to cells in photodynamic therapy (PDT). The relevance of SO in the environmental and biomedical domains has fuelled research towards improved methodologies for its efficient generation. In this paper, we report the use of a bis-imidazolium-based amphiphile that forms supramolecular gels in water-ethanol mixtures encapsulating SO generating chromophores. The gels comprise twisted fibres that incorporate one of four different porphyrins: 5,10,15,20-tetrakis(N-methyl-4-pyridinium)porphyrin tetraiodide (TPPP), 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP), 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin (TPP-3OH) and 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (TPP-4OH). Rheological measurements confirmed viscoelastic properties characteristic of these types of supramolecular gels, suggesting their potential as effective local PDT delivery systems. Enhanced SO generation within the hydrogel matrix compared to the solution of the chromophores was observed in suspension in a spectrophotometer using uric acid as the molecular probe. The SO generation was also shown through antimicrobial PDT (aPDT) studies. The TPPP-containing gel showed the highest reduction in the colony forming unit (CFU) count, which is 94% against E. coli and 100% against S. aureus. These results indicate that the porphyrin gels based on a gemini amphiphile with a high level of SO production are of significant interest and have a lot of potential use in aPDT.

Proximal Oblique-Packing of Heptamethine Cyanines through Spiro-Connection Boosts Triplet State Generation in Near-Infrared

Near-infrared (NIR) triplet dyes are the cornerstones of cutting-edge biomedical and material applications. The difficulty in rational development of triplet dyes increases exponentially as the absorption wavelength shifts deeper into the NIR range. Although classical H-/J-typed packing of NIR dyes has the potential to enhance intersystem crossing (ISC) compared with that in single-chromophore dyes, the triplet state quantum yields remain limited in such strategy. Herein, proximal oblique-packed (V-shaped) heptamethine cyanines (SZ780) through spiro-connection were achieved. Multi-channel ultrafast ISC were direct observed in SZ780 and a record high ISC rate constant (up to ~1011 s-1) is registered among all the reported NIR triplet dyes. SZ780 exhibits a triplet state quantum yield of 18.9 % upon excitation at 750 nm, which is almost an order of magnitude higher than that of the monomer (IR780, 2.1 %) and nearly threefold increase compared to that of the H-packed dimer (SC780) (6.7 %). Moreover, SZ780 efficiently generates singlet oxygen under 808 nm light irradiation, inducing cancer cell apoptosis in vivo. These findings demonstrate that constructing V-aggregated dyes system by spiro-connection offers a powerful approach for the design of high-performance NIR triplet sensitizers.

Electrostatic Co-Assembly of Cyanine Pair for Augmented Photoacoustic Imaging and Photothermal Therapy

Molecular phototheranostic dyes are of eminent interest for oncological diagnosis and imaging-guided phototherapy. However, it remains challenging to develop photosensitizers (PSs) that simultaneously integrate high-contrast photoacoustic imaging and efficient therapeutic capabilities. In this work, a supramolecular strategy is employed to construct a molecular pair phototheranostic agent via the direct self-assembly of two cyanines, C5TNa (anionic) and Cy-Et (cationic). The Coulombic interactions between C5TNa and Cy-Et facilitate the formation of a complementary cyanine pair (C5T-ET) and the creation of supramolecular CT-J-type aggregates in water. This complementary cyanine pair (C5T-ET) results in completely quenched fluorescence and significantly enhances nonradiative deactivation (≈22 ps), leading to a 3.3-fold increase in photothermal conversion efficiency and a 7.1-fold enhancement in photoacoustic response compared to indocyanine green (ICG). As a result, the J-type aggregate cyanine pair (C5T-ET) demonstrates high photoacoustic imaging capability and remarkable antitumor phototheranostic efficacy in vivo, highlighting its potential for clinical applications. This work provides strong experimental evidence for the superior performance of the complementary cyanine pair (C5T-ET) in enhancing photosensitization and photoacoustic response. It is believed that this strategy will propel the advancement of controllable dye J-aggregates and contribute to the practical implementation of photoacoustic imaging and phototherapy in vivo.

Hollow nanosystem-boosting synergistic effects between photothermal therapy and chemodynamic therapy via self-supplied hydrogen peroxide and relieved hypoxia

Nanomedicine-based photothermal therapy (PTT) has been considered as an excellent alternative for treatment of tumor tissue due to its high therapeutic efficiency and controllable range. However, the overexpression of heat shock proteins (HSPs) during PTT and the hypoxic properties of the tumor microenvironment can lead to intracellular thermal resistance and reduce its effectiveness. Reactive oxygen species (ROS), followed by the application of chemodynamic therapy (CDT) and photodynamic therapy (PDT), can eliminate HSPs and overcome thermal resistance. High concentration H2O2 was used to catalyze oxygen production in the tumor microenvironment to improve the anaerobic state. Therefore, we present a multifunctional nanocarrier system driving chemodynamic-photodynamic-photothermal synergistic therapy via self-supplied hydrogen peroxide and relieved hypoxia for prostate tumor treatment.

Orthogonally conjugated phthalocyanine-porphyrin oligomer for NIR photothermal-photodynamic antibacterial treatment

With the increase of antibiotic resistance worldwide, there is an urgent demand to develop new fungicides and approaches to address the threat to human health posed by the ineffectiveness of traditional antibiotics. In this work, an orthogonal conjugated uniform oligomer bactericide of SiPc-ddCPP was constructed between silicon phthalocyanine and porphyrin, which can effectively treat infection through photodynamic-photothermal combined therapy without considering drug resistance. Compared with organic photothermal agents induced by unstable H-aggregation with blue-shifted absorption and fluorescence/ROS quenching, this orthogonal-structured uniform SiPc-ddCPP nanoparticle shows remarkably stability and NIR photothermal effect (η = 31.15%) along with fluorescence and ROS generation. Antibacterial studies have shown that both Gram-positive and Gram-negative bacteria could be efficiently annihilated in a few minutes through synergistic PDT-PTT along with satisfactory bacterial targeting. These results suggest SiPc-ddCPP is a multifunctional NIR bactericide, which afford a new approach of synergistic PDT-PTT sterilization to conquer the crisis of antibiotic resistance.

In Situ NADH-Activated BODIPY-Based Macrocyclic Supramolecular Photosensitizer for Chemo-Photodynamic Synergistic Tumor Therapy

Photodynamic therapy (PDT) based on supramolecular assembly has been receiving wide attention due to its great potential application in clinical treatment. Herein, we report a supramolecular photoelectron "reservoir" (SPR) constructed by tetracationic boron dipyrromethene (BODIPY)-based macrocycle (BBox·4Cl), doxorubicin (Dox), and tumor-targeted β-cyclodextrin-grafted hyaluronic acid (HACD). Upon irradiation, BBox·4Cl can in situ catalyze nicotinamide adenine dinucleotide (NADH) to continuously generate electrons to inject into SPR, which further transfers electrons to oxygen, inducing highly efficient hydroxyl radical generation even under hypoxia. Synergistically, Dox in SPR as "pump" can be encapsulated by BBox·4Cl and transport photoelectrons between two BODIPY units, while HACD as "sponge" can enrich BBox·4Cl by the electrostatic interaction to concentrate them closer in space, which facilitates intramolecular and intermolecular photoelectron transfer, respectively, and significantly enhances the generation of hydroxyl radicals. Meanwhile, electron replenishment in SPR causes NADH depletion and redox dysfunction, thereby accelerating the apoptosis and achieving highly effective synergistic tumor therapy.

Flexible Formation of Nanoparticles: Selectively Self-Assembling with Glycoclusters to Form Nano-Photosensitizers for Multipurpose Bioimaging and Photodynamic Therapy

The smart construction of nano-photosensitizers (PSs) is significant for multipurpose applications, such as bioimaging, efficient photodynamic anti-tumor or anti-bacterial studies. This work reports a flexible self-assembling strategy for the construction of nano-PSs, in which PSs spontaneously form amorphous aggregates for killing bacteria, or self-assemble with tetraphenylethene (TPE) based glycoclusters (TPE-Glc4) to construct glyco-dots for cell imaging and photodynamic anti-tumor studies. Tricyanofuran (TCF) and TPE units were bridged with furan or thiophene moiety to construct two PSs (1 and 2) with NIR fluorescence in monomers, and a performance of the aggregation-induced generation of reactive oxygen species (AIG-ROS) in an aggregated state. Compared to the large amorphous aggregates (2-a), TPE-based glycoclusters encapsulated with PS form glyco-dots (2-Glc) that exhibit a smaller and more homogeneous hydrated size of approximately 40 nm, as well as enhanced water-solubility and biocompatibility. TPE-glycoclusters facilitate the cellular uptake of 2 into HepG2 cells, therefore enhancing the NIR fluorescence imaging signal and photodynamic therapy. Meanwhile, 2-a exhibits satisfied phototoxicity against Escherichia coli. This work highlights the flexible self-assembly of nano-PSs for multifunctional bioapplications.

Engineered Au@MOFs silk fibroin-based hydrogel phototherapy platform for enhanced wound healing performance

Wound bacterial infections not only impede the healing process but can also give rise to a range of serious complications, thereby posing a substantial risk to human health. Developing effective wound dressings incorporating phototherapy functionalities, specifically photothermal therapy (PTT) and photodynamic therapy (PDT), remains a critical area of research in modern wound care. Existing PTT-PDT systems often suffer from challenges such as nanoparticle aggregation and inefficient reactive oxygen species (ROS) generation, which are essential for therapeutic efficacy. This study presents a pioneering approach by combining zeolitic imidazolate framework derivatives (ZIFs) and Au NPs in a silk fibroin (SF) hydrogel for the first time. This combination not only prevents particle aggregation but also significantly enhances photothermal conversion efficiency and ROS generation capacity. The digital light processing (DLP) printability of our hydrogel allows for customized wound dressings tailored to individual patient needs, improving therapeutic efficacy. The hydrogel's effectiveness was evaluated through rigorous in vivo experiments, demonstrating enhanced antibacterial properties and accelerated wound healing. The biocompatibility of our hydrogel ensures its suitability for clinical applications, minimizing adverse reactions while promoting healing. A wound healing rate of 99.06 % represents a substantial improvement over the control groups, indicating markedly enhanced therapeutic efficacy. These findings underscore its multifunctionality in addressing infected wounds, presenting a promising strategy for facilitating the rapid healing of acute complex wounds in clinical applications.

A One Stone Three Birds Paradigm of Photon-Driven Pyroptosis Dye for Amplifying Tumor Immunotherapy

Activating the pyroptosis pathway of tumor cells by photodynamic therapy (PDT) for immunogenic cell death (ICD) is considered a valid strategy in pursuit of antitumor immunotherapy, but it remains a huge challenge due to the lack of reliable design guidelines. Moreover, it is often overlooked that conventional PDT can exacerbate the development of tumor immunosuppressive microenvironment, which is apparently unfavorable to clinical immunotherapy. The endoplasmic reticulum's (ER) pivotal role in cellular homeostasis and its emerging link to pyroptosis have galvanized interest in ER-centric imaging and therapeutics. Herein, using the targeted group-assisted strategy (TAGS), an intriguing cyclooxygenase-2-targeted photodynamic conjugate, Indo-Cy, strategically created, which exploits the enzyme's overabundance in the tumoral ER, especially under proinflammatory hypoxic conditions. This conjugate, with its highly precise ER imaging, embodies a trifunctional strategy: i) innovating an electron transfer mechanism, converting the hemicyanine moiety into an oxygen-independent type I photosensitizer, thereby navigating around the hypoxia constraints of traditional PDT; ii) executing precise ER-targeted PDT, amplifying caspase-1/GSDMD-mediated pyroptosis for ICD; 3) attenuating immunosuppressive pathways by inhibiting cyclooxygenase-2 downstream factors, including HIF-1α, PGE2, and VEGF. Indo-Cy's multimodal approach potently induces in vivo tumor pyroptosis and bolsters antitumor immunity, underscoring cyclooxygenase-2-targeted dyes' potential as a versatile oncotherapeutics.

Microneedle technology for enhanced topical treatment of skin infections

Skin infections caused by microbes such as bacteria, fungi, and viruses often lead to aberrant skin functions and appearance, eventually evolving into a significant risk to human health. Among different drug administration paradigms for skin infections, microneedles (MNs) have demonstrated superiority mainly because of their merits in enhancing drug delivery efficiency and reducing microbial resistance. Also, integrating biosensing functionality to MNs offers point-of-care wearable medical devices for analyzing specific pathogens, disease status, and drug pharmacokinetics, thus providing personalized therapy for skin infections. Herein, we do a timely update on the development of MN technology in skin infection management, with a special focus on how to devise MNs for personalized antimicrobial therapy. Notably, the advantages of state-of-the-art MNs for treating skin infections are pointed out, which include hijacking sequential drug transport barriers to enhance drug delivery efficiency and delivering various therapeutics (e.g., antibiotics, antimicrobial peptides, photosensitizers, metals, sonosensitizers, nanoenzyme, living bacteria, poly ionic liquid, and nanomoter). In addition, the nanoenzyme-based multimodal antimicrobial therapy is highlighted in addressing intractable infectious wounds. Furthermore, the MN-based biosensors used to identify pathogen types, track disease status, and quantify antibiotic concentrations are summarized. The limitations of antimicrobial MNs toward clinical translation are offered regarding large-scale production, quality control, and policy guidance. Finally, the future development of biosensing MNs with easy-to-use and intelligent properties and MN-based wearable drug delivery for home-based therapy are prospected. We hope this review will provide valuable guidance for future development in MN-mediated topical treatment of skin infections.

Recent advances in near-infrared organic photosensitizers for photodynamic cancer therapy

With the advancement of photodynamic therapy, various photosensitizers have been developed to enhance the efficacy of cancer treatment while minimizing side effects. Recently, near-infrared organic fluorophores have gained significant attention as promising photodynamic agents for cancer therapy due to their tunable photophysical properties, structural versatility, good biocompatibility, high biosafety, and synthetic flexibility. In particular, near-infrared organic photosensitizers offer several notable advantages, including deep tissue penetration, a low fluorescence background for bioimaging, and reduced damage to biological tissues compared to traditional visible-spectrum photosensitizers. In this minireview, we will discuss the current developments in near-infrared organic photosensitizers for photodynamic cancer therapy. Furthermore, we will briefly highlight the challenges and prospects in this field. This minireview aims to encourage more researchers to develop advanced near-infrared organic photosensitizers and facilitate their transition from laboratory research to preclinical studies and ultimately to clinical use.

Antibacterial and surface properties of post-light-activated metal-free phthalocyanine-deposited TiO2 nanotube smart surfaces

The utilisation of implantable medical devices has become safer and more prevalent since the establishment of sterilisation methods and techniques a century ago. Nevertheless, device-associated infections remain a significant and growing concern, particularly in light of the continued rise in the number of medical device implantations. This underscores the imperative for the development of efficacious prevention and treatment strategies for device-associated infections, as well as further investigation into the design of innovative antibacterial surfaces for medical device applications. The motivation of this work is to investigate the post-light-activated antibacterial photosensitive surfaces fabricated on medical titanium (Ti) surfaces. Thus, in this work, metal-free phthalocyanine (H2Pc)-deposited TiO2 nanotube (TNT) array smart photosensitive surfaces were fabricated on titanium (Ti) surfaces for medical device applications. First, well-ordered nanotube surfaces were produced on titanium using an anodic oxidation (AO) process. Then, H2Pc was accumulated onto TNT surfaces using a physical vapour deposition (PVD-TE) process. H2Pc-deposited TNT surfaces were fabricated on Ti substrates by combining AO and physical vapour deposition (PVD-TE) processes in this work for the first time in the literature. H2Pc was largely coated onto TNT arrays and exhibited elemental homogeneity throughout the whole surface. The contact angle of H2Pc-deposited TNT surfaces was about 89° whereas other Ti and TNT surfaces demonstrated hydrophilic characteristics. Therefore, they exhibited remarkable hydrophobic behavior in terms of antibacterial properties. Importantly, compared to Ti and TNT surfaces, the bacterial inhibition on sunlight-activated H2Pc-deposited TNT surfaces was 94.9% for S. aureus and 97.3% for E. coli, respectively. According to these results, H2Pc-deposited TNT innovative surfaces provided superior antibacterial activity post-light-activation under sunlight due to their photosensitive character.

Dynamic Nanostructure-Based DNA Logic Gates for Cancer Diagnosis and Therapy

DNA logic gates with dynamic nanostructures have made a profound impact on cancer diagnosis and treatment. Through programming the dynamic structure changes of DNA nanodevices, precise molecular recognition with signal amplification and smart therapeutic strategies have been reported. This enhances the specificity and sensitivity of cancer theranostics, and improves diagnosis precision and treatment outcomes. This review explores the basic components of dynamic DNA nanostructures and corresponding DNA logic gates, as well as their applications for cancer diagnosis and therapies. The dynamic DNA nanostructures would contribute to cancer early detection and personalized treatment.

Current trends and research advances on the application of TiO2 nanoparticles in dentistry: How far are we from clinical translation?

The great potential of nanotechnology-based knowledge during the past decade has shown great potential to elevate human living standards and enhance healthcare conditions through diagnosing, preventing, and treating different diseases. Among abundant nanoparticles (NPs), inorganic NPs feature distinctive biological and physicochemical properties compared to their conventional counterparts which do not endow. TiO2 NPs possess excellent properties including low-cast, antibacterial properties, biocompatibility, and physicochemical stability. The present review highlights and discusses the current trends in applying TiO2 NPs in dentistry ranging from TiO2-based nanocomposite in endodontics, orthodontics, and biofilm prevention. Moreover, the potential of TiO2 NPs in developing new photodynamic therapy and the next generation of oral care products is outlined. In the end, the clinical translation of TiO2-based dental materials is brought to the forefront which is impetus and of great importance to developing inorganic NP-based dental materials.

Formation of self-assembly aggregates in traditional Chinese medicine decoctions and their application in cancer treatments

Traditional Chinese Medicine (TCM) formulas, based on the principles of Chinese medicine, have a long history and are widely applied in the treatment of diseases. Compared to single-component drugs, TCM formulas demonstrate superior therapeutic efficacy and fewer side effects owing to their synergistic effects and mechanisms of detoxification and efficacy enhancement. However, various drawbacks, such as the uncertainty of functional targets and molecular mechanisms, poor solubility of components, and low bioavailability, have limited the global promotion and application of TCM formulas. To overcome these limitations, self-assembled aggregate (SA) nanotechnology has emerged as a promising solution. SA nanotechnology significantly enhances the bioavailability and anti-tumor efficacy of TCM by improving its absorption, distribution, and precise targeting capabilities, thereby providing an innovative solution for the modernization and internationalization of TCM. This review delves into the nature and common interactions of SAs based on the latest research developments. The structural characteristics of SAs in TCM formulas, paired-herb decoctions, and single-herb decoctions are analyzed and their self-assembly mechanisms are systematically elucidated. In addition, this article elaborates on the advantages of SAs in cancer treatment, particularly in enhancing the bioavailability and targeting capabilities. Furthermore, this review aims to provide new perspectives for the study of TCM compatibility and its clinical applications, thereby driving the innovative development of nanomaterials in this field. On addressing the technological challenges, SAs are expected to further promote the global application and recognition of TCM in the healthcare sector.

pH-Sensitive and Lysosome Targetable Photosensitizers Based on BODIPYs

Photodynamic therapy (PDT) is an effective and U.S. Food and Drug Administration (FDA) approved treatment for cancer and other diseases. Photosensitizer is one of the three key components that harvest the energy of light at a certain wavelength. Compared to the conventional fluorophores used as photosensitizers, boron dipyrromethene (BODIPY) derivatives have grown fast in recent years due to their low dark toxicity, versatile tunable sites, and easiness of being paired with other treatments. In this paper, two pH-sensitive BODIPY-based photosensitizers (BDC and BDBrC) were synthesized by adding carbazole moieties onto the BODIPY cores (BD and BDBr) through condensation reactions. BDBrC has two Br atoms at the BODIPY core that promote singlet oxygen generation and further red-shift the absorption maximum peak. Both compounds showed sensitivity toward pH change and generated more singlet oxygen under acidic conditions. The cellular uptake and cell imaging experiments showed that BDBrC can selectively target the lysosome organelle. The further dark cell viability and light cytotoxicity indicate the light triggered PDT treatment can be accomplished with BDBrC.

Phenazinium- and Malachite Green-Based Pd(II) Cages: Chiroptical Discrimination of Nucleoside Triphosphates

Organic chromophores have been successfully implemented into supramolecular systems to bestow them with distinct photophysical properties for various applications, ranging from solar energy conversion, photochemical reactions or as receptors for guest molecules with optical readout. We had previously introduced first members of the large family of coal-tar dyes (methylene blue, crystal violet and rhodamine) as integral components of coordination cages. Here, we add two new chromophores, malachite green (MGP) and a purple phenazinium dye (PHP), serving as backbones of bis-monodentate banana-shaped ligands with pyridine donors. We show the formation of corresponding green and purple coloured Pd2L4 coordination cages and investigate their interaction with chiral guest molecules via UV-Vis and CD spectroscopy. The PHP cage can be used to recognize nucleoside triphosphates, based on chirality transfer from the guests to the structurally flexible helicate. In combination with the already known methylene blue cage MBP we could further differentiate between all four canonical NTPs through characteristic changes in the observed CD signatures.

Recent advances in biotin-based therapeutic agents for cancer therapy

Biotin receptors, as biomarkers for cancer cells, are overexpressed in various tumor types. Compared to other vitamin receptors, such as folate receptors and vitamin B12 receptors, biotin receptor-based targeting strategies exhibit superior specificity and broader potential in treating aggressive cancers, including ovarian cancer, leukemia, colon cancer, breast cancer, kidney cancer, and lung cancer. These strategies promote biotin transport via receptor-mediated endocytosis, which is triggered upon ligand binding. Biotin, as the ligand of the biotin receptor, can be conjugated to anti-cancer drugs to form targeted therapies that bind to receptors overexpressed on tumor cells, thus increasing drug uptake. Despite these advantages, many candidate drugs have progressed slowly and remain in the preclinical stage, impeding clinical translation. This is mainly due to the effects of various conjugation methods and drug formulations on their functionality and efficacy. Therefore, developing novel biotin-based therapeutics is crucial. The innovation of this strategy lies in its multifunctionality-researchers can use different conjugation methods to design and synthesize these drugs, enabling precise targeting of various tumor types while minimizing toxicity to normal cells. These drugs include small-molecule-biotin conjugates (SMBCs) and nano-biotin conjugates (NBCs). This dual-platform approach represents a significant advancement in targeted therapy, offering unprecedented flexibility in drug design and delivery. Compared to chemotherapy drugs and traditional delivery systems, biotin-based drugs with tumor-specific targeting demonstrate enhanced targeting, improved efficacy, and reduced toxicity. This review examines strategies and applications for enhancing the delivery of chemotherapy drugs to cancer cells, highlighting the need for high-quality conjugates and strategies. It not only summarizes the latest progress but also provides key insights into how this emerging field could revolutionize personalized cancer treatment, especially in the context of precision medicine. Additionally, it offers perspectives on future research directions in this field.

Toluidine blue O demethylated photoproducts as type II photosensitizers

Toluidine blue O (TBO) is a type I-type II photosensitizer that has shown good efficacy and selectivity in antimicrobial and anticancer photodynamic therapy applications. However, its complex photochemistry with multiple photoproducts hinders its application as a photosensitizer. We have previously described the mechanism for photooxidative demethylation of TBO which in acetonitrile yields two main products: demethylated-TBO (d-TBO) and double-demethylated-TBO (dd-TBO). In the current work, we describe the photophysical properties of these two photoproducts. In acetonitrile and phosphate buffer, demethylation induces an hypsochromic shift in the absorption and fluorescence emission maxima. Fluorescence quantum yields increase slightly for the demethylated photoproducts, in agreement with the lengthening of the fluorescence lifetimes. Triplet excited states lifetimes in the presence of oxygen decreased slightly upon demethylation. However, the singlet oxygen quantum yield increased significantly reaching unity for the dd-TBO photoproduct. These results are interpreted in terms of the competing pathways of TBO photochemistry. For TBO, demethylation is the main pathway for deactivation of the excited state, while for d-TBO, demethylation and singlet oxygen generation are significant. For dd-TBO, singlet oxygen generation is the main deactivation pathway. Overall, TBO demethylated photoproducts demonstrate good potential as candidates for photodynamic therapy applications.

Pivotal Role of the Intracellular Microenvironment in the High Photodynamic Activity of Cationic Phthalocyanines

To investigate the influence of phthalocyanine aggregation on their photodynamic activity, a series of six cationic water-soluble zinc(II) phthalocyanines bearing from four to sixteen 4-((diethylmethylammonium)methyl)phenoxy substituents was synthesized. Depending on their structure, the phthalocyanines have different aggregation behaviors in phosphate buffer solutions ranging from fully assembled to monomeric states. Remarkably, independent of aggregation in buffer, very high photodynamic efficiencies against the tumor cell lines MCF-7 and MDA-MB-231 in the nanomolar range were found for all investigated phthalocyanine, and the IC50(light) varied from 27 to 358 nM (3.5 J/cm2, 660 nm) with IC50(dark)/IC50(light) ratios up to ∼3700. This is due to the intracellular disassembly of aggregated phthalocyanines with the formation of monomeric photoactive forms, as demonstrated by fluorescence microscopy. Indeed, the interaction of aggregated phthalocyanines with serum proteins in a buffer resulted in the disassembly of nonluminescent aggregate species with the release of photoactive monomers bound to protein macromolecules.

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.

An Activatable Heavy-Atom-Free Upconversion Photosensitizer for Targeted Imaging and Treatment of Tumors

Photodynamic therapy (PDT) is an innovative and promising method for treating tumors that has attracted significant interest but still faces several challenges, such as a lack of selectivity, deep penetration of light, and efficient ROS generation. To address these challenges, we optimized and synthesized a series of photosensitizers and successfully developed a heavy-atom-free near-infrared FUCL photosensitizer NFh-NMe-2. This photosensitizer can generate singlet oxygen (1O2) and induce cellular apoptosis under 808 nm light. For the safe ablation of microtumors in vivo, an activatable FUCL photosensitizer NFh-NTR was developed based on the overexpression of nitroreductase (NTR). NFh-NTR could be activated by NTR, leading to the release of the photosensitizer NFh-NMe-2, restoring the fluorescence signal, and effectively killing tumor cells under 808 nm light irradiation. This work opens new possibilities in the chemical design of an FUCL photosensitizer for cancer treatment.

Nonemissive Iridium(III) Solvent Complex as a Self-Reporting Photosensitizer for Monitoring Phototherapeutic Efficacy in a "Signal on" Mode

Photodynamic therapy (PDT) has long been receiving increasing attention for the minimally invasive treatment of cancer. The performance of PDT depends on the photophysical and biological properties of photosensitizers (PSs). The always-on fluorescence signal of conventional PSs makes it difficult to real-time monitor phototherapeutic efficacy in the PDT process. Therefore, functional PSs with good photodynamic therapy effect and self-reporting properties are highly desired. Here, two nonemissive iridium(III) solvent complexes, [(dfppy)2Ir(DMSO)]Cl (Ir-DMSO, dfppy = 2,4-difluorophenyl)pyridine, DMSO = dimethyl sulfoxide) and [(dfppy)2Ir(ACN)]Cl (Ir-ACN, ACN = acetonitrile) as PSs, were synthesized. Both of them exhibit intense high-energy absorption bands, low photoluminescence (PL) emission, and low dark toxicity. Thanks to the lower dark toxicity of Ir-DMSO, we chose it as a PS for further PDT. In this work, Ir-DMSO functions as a specific PL "signal on" PS for self-reporting therapeutic efficacy during its own PDT process. Colocalization experiments indicated that Ir-DMSO accumulated in the endoplasmic reticulum and mitochondria. Under light irradiation, Ir-DMSO not only exhibited the ability to kill cancer cells but also presented a "signal on" PL response toward cell death. During Ir-DMSO-induced PDT, cell death modality was further investigated and immunogenic cell death was revealed, in which main hallmarks, including ROS generation, upregulation of surface-exposed calreticulin, high-mobility group box 1, and adenosine triphosphate secretion, were observed. Thanks to the specific coordination reaction between Ir-DMSO and histidine (His)/His-containing proteins, the phototherapeutic efficacy can be monitored in real time without other signal probes. This work provides a new and promising strategy for the development of PSs with self-reporting ability, which is of great importance for imaging-guided PDT.

Moderately Heavy Atom-Substituted BODIPY Photosensitizer with Mitochondrial Targeting Ability for Imaging-Guided Photodynamic Therapy

Advanced photodynamic therapy requires photosensitizers with targeting, diagnostic, and therapeutic properties. To fulfill this multifunctionality, we report the synthesis of two triphenylphosphonium (TPP)-functionalized boron-dipyrromethene (BODIPY) dyes, TPPB-H and TPPB-Br, which incorporate a hydrogen atom and dibrominated vinyl moiety at the 6-position of the BODIPY core, respectively. The heavy-atom effect of the moderately heavy bromine atoms allowed TPPB-Br to achieve a proper balance between the toxic singlet oxygen (1O2) production and fluorescence efficiencies. In this dye, the bromine atom-induced stimulation of the singlet-to-triplet intersystem crossing dynamics resulted in an approximately 45-fold increase in the 1O2 quantum yield with respect to that of the nonbrominated counterpart (0.0059 and 0.28 for TPPB-H and TPPB-Br, respectively). This increase was accompanied only a 2-fold reduction in the fluorescence quantum yield (0.54 and 0.22 for TPPB-H and TPPB-Br, respectively). During multicolor confocal laser scanning microscopy observations conducted using two carcinomas, MCF-7 and HeLa, both BODIPY dyes exhibited high targeting specificity toward cancer cell mitochondria owing to the TPP cation functionalization. The two dyes also showed the feasibility of fluorescence cell imaging; however, only the dibrominated BODIPY TPPB-Br manifested pronounced photocytotoxicity with half-maximal inhibitory concentrations of 0.12 and 0.77 μM obtained for MCF-7 and HeLa cells, respectively. These findings demonstrate the potential applicability of TPPB-Br as an imaging-guided photodynamic therapy agent with mitochondrial specificity.

Tetramethyl Cucurbit[6]uril-Porphyrin Supramolecular Polymer Enhances Photosensitization

Porphyrins serve as photosensitizers (PS) in the realm of cancer photodynamic therapy (PDT). Upon excitation by laser light, porphyrins are capable of converting molecular oxygen into highly cytotoxic singlet oxygen (1O2). However, the rigid π-conjugated structure of porphyrins frequently results in the formation of aggregates in aqueous solutions, which leads to the self-quenching of the excited state. Cucurbit[n]urils exhibit the capacity to stably bind with porphyrins via host-guest interactions, effectively inhibiting their aggregation and potentially enhancing the therapeutic efficacy of PDT. In this study, water-soluble tetramethyl cucurbit[6]uril (TMeQ[6]) was selected as the host, while four propionic acid group-appended porphyrin cationic (TPPOR) was utilized as guests to construct a supramolecular photosensitizer (TPPOR-2TMeQ[6]) in a molar ratio of 2:1. Further experimental findings demonstrate that the presence of TMeQ[6] inhibits the aggregation of TPPOR through non-covalent interactions. This inhibition reduces the energy difference between the excited singlet and triplet states, thereby enhancing the conversion efficiency of 1O2. Moreover, TPPOR-2TMeQ[6] exhibits favorable biocompatibility and minimal dark toxicity against breast cancer cells (4T1). Upon intracellular excitation, the levels of reactive oxygen species (ROS) significantly increase, inducing oxidative stress in 4T1 cells and leading to apoptosis. Consequently, the findings of this study suggest that the enhanced photosensitization achieved through this supramolecular approach is likely to promote the anticancer therapeutic effects of PDT, thereby broadening the application prospects of porphyrins within PDT systems.

Defect-Engineered Tin Disulfide Nanocarriers as "Precision-Guided Projectile" for Intensive Synergistic Therapy

Nanoformulations with endogenous/exogenous stimulus-responsive characteristics show great potential in tumor cell elimination with minimal adverse effects and high precision. Herein, an intelligent nanotheranostic platform (denoted as TPZ@Cu-SnS2-x/PLL) for tumor microenvironment (TME) and near-infrared light (NIR) activated tumor-specific therapy is constructed. Copper (Cu) doping and the resulting sulfur vacancies can not only improve the response range of visible light but also improve the separation efficiency of photogenerated carriers and increase the carrier density, resulting in the ideal photothermal and photodynamic performance. Density functional theory calculations revealed that the introduction of Cu and resulting sulfur vacancies can induce electron redistribution, achieving favorable photogenerated electrons. After entering cells through endocytosis, the TPZ@Cu-SnS2-x/PLL nanocomposites show the pH responsivity property for the release of the TPZ selectively within the acidic TME, and the released Cu2+ can first interact with local glutathione (GSH) to deplete GSH with the production of Cu+. Subsequently, the Cu+-mediated Fenton-like reaction can decompose local hydrogen peroxide into hydroxyl radicals, which can also be promoted by hyperthermia derived from the photothermal effect for tumor cell apoptosis. The integration of photoacoustic/computed tomography imaging-guided NIR phototherapy, TPZ-induced chemotherapy, and GSH-elimination/hyperthermia enhanced chemodynamic therapy results in synergistic therapeutic outcomes without obvious systemic toxicity in vivo.

Orthogonal Geometry Enhancing the Intersystem Crossing and Photosensitive Efficiency of Spiro Organoboron Compounds

Based on the reported spiro organoboron compounds (PS1 and PS2 as potent 1O2 sensitizers), several new organoboron molecules (PS4-PS9) were constructed through structural modification, and their low-lying excited states and photophysical properties have been explored by density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. The predicted effective intersystem crossing (ISC) processes arise from the S1→T2 transition for PS4-PS6 and the S1→T4 transition for PS1, and corresponding KISC rate constants reach the order of magnitude of 109 (s-1). The organoboron compounds with a (N, N) chelate acceptor are predicted to exhibit relatively higher ISC efficiency than those bearing a (N, O) acceptor, and the planar C3NBN ring and the orthogonal configuration between the donor and acceptor moieties are responsible for the ISC rate enhancement. Importantly, the geometric features of the lowest singlet excited state (S1) for these compounds play a decisive role in their photosensitive efficiency. The present results provide a basis for better understanding of the photosensitivity of these spiro organoboron compounds and the structural modification effect.

Light switchable Ir(III)-based photosensitizers: a dual-state system for non-invasive, reversible ROS control in tumor therapy

Photodynamic therapy (PDT), a powerful anticancer approach converting oxygen to ROS for tumor ablation, encounters hurdles like limited spatio-temporal selectivity and the consequent unnecessary damage to normal tissues. Addressing these challenges, developing controllable Ir(III)-based photosensitizers (PSs) emerges as a promising solution, offering enhanced efficacy and precision in cancer therapy, while propelling the clinical progression of metal-based PSs. Herein, we proposed a series of light-controlled PSs, integrating an Ir(III)-based moiety with a light-responsive module, enabling non-invasive "off-on" control of ROS production via efficient energy transfer. The open form (OF) in this dual-state system has better lipid solubility and cellular uptake compared to the closed form (CF), which facilitates targeted delivery of metal drugs. Comprehensive intracellular experiments demonstrated the OF complex's superior cytotoxicity under light irradiation, with the CF complex achieving comparable toxicity post-conversion. Notably, the PSs inhibited 3D tumor growth and modulated intracellular ROS production. These findings underscore the potential of Ir(III)-based dual-state photoswitchable complexes as a platform for non-invasive, reversible ROS control, offering broad prospects in tumor therapy and beyond.

Determination of singlet oxygen quantum yield based on the behavior of solvent dimethyl sulfoxide oxidation by singlet oxygen

BACKGROUND

Photodynamic therapy (PDT) is emerging as a promising cancer treatment. The PDT efficacy is primarily attributed to the generation of singlet oxygen (1O2), stemming from the integrated effects of the photosensitizer, oxygen, and light. The singlet oxygen quantum yield (ΦΔ) serves as a bridge that links these parameters to the overall efficacy of PDT. The near-infrared luminescence of 1O2 provides a direct way for determining ΦΔ, but suffers from a poor signal-to-noise ratio. While the chemical trap probe method is detection-friendly, but it has a strict requirement for the excitation wavelength. Therefore, the existing methods for ΦΔ measurement are insufficient.

RESULTS

In this work, we developed an approach to determine ΦΔ of a broader range of photosensitizers using only the commonly used solvent dimethyl sulfoxide (DMSO), which can be oxidized by 1O2 to dimethyl sulfone. This method establishes the relationship between 1O2 production and changes in DMSO absorption spectra, eliminating the need for additional chemical probes. This method was validated by measuring the ΦΔ of rose bengal (RB) through systematic changes in absorption spectrum of DMSO under various RB concentrations and different excitation light power densities. Moreover, the ΦΔ of hematoporphyrin monomethyl ether (HMME), as determined by this method, is consistent with measurements obtained using the 1,3-diphenylisobenzofuran (DPBF) trapping probe. This consistency further validates the reliability of this method.

SIGNIFICANCE AND NOVELTY

This work presents a direct, probe-free method to determine ΦΔ, reducing potential interference and expanding the range of useable excitation wavelengths. Its ability to measure ΦΔ using only DMSO enhances the accuracy of photosensitizer measurement, and broadens the applicability of the method to a wide range of samples, thereby advancing research on the properties of photosensitizers and further promoting the development of PDT.

Curcumin-based residue-free and reusable photodynamic inactivation system for liquid foods and its application in freshly squeezed orange juice

To enhance curcumin's application in photodynamic inactivation (PDI) of liquid foods, a supramolecular complex of biotin-modified β-cyclodextrin and curcumin (Biotin-CD@Cur) was synthesized. This complex significantly improves curcumin's solubility, stability, and PDI efficiency. Following PDI, Biotin-CD@Cur can be magnetically separated from the liquid matrix using streptavidin-coated magnetic beads (SA-MBs). Leveraging the reversible binding between streptavidin and biotin, Biotin-CD@Cur and SA-MBs fully dissociate in ultrapure water at 70 °C, enabling reuse. Antibacterial tests in freshly squeezed orange juice demonstrated that a low dose of 1.5 J/cm2 from a 420 nm LED array and 10 μg/mL of Biotin-CD@Cur achieved log reductions of 3.287 ± 0.015 for Staphylococcus aureus and 2.961 ± 0.011 for Listeria monocytogenes, while preserving the juice's flavor and nutritional contents. The PDI system remained effective for at least four cycles. Ultra-performance liquid chromatography and atomic absorption spectroscopy confirmed no residues of system components in the juice after magnetic separation.

Recent Biomedical Applications of Functional Materials Based on Polyhedral Oligomeric Silsesquioxane (POSS)

Polyhedral oligomeric silsesquioxane (POSS) is a 3D, cage-like nanoparticle with an inorganic Si-O-Si core and eight tunable corner functional groups. Its well-defined structure grants it distinctive physical, chemical, and biological properties and has been widely used for preparing high-performance materials. Recently, click chemistry has enabled the synthesis of various functional POSS-based materials for diverse biomedical applications. This article reviews the recent applications of POSS-based materials in the biomedical field, including cancer treatment, tissue engineering, antibacterial use, and biomedical imaging. Representative examples are discussed in detail. Among the various POSS-based applications, cancer treatment and tissue engineering are the most important. Finally, this review presents the current limitations of POSS-based materials and provides guidance for future research.

Hybrid Homodimeric Prodrug Nanoassemblies for Low-Toxicity and Synergistic Chemophotodynamic Therapy of Melanoma

Synergistically active nanoparticles hold great promise for facilitating multimodal cancer therapy. However, strategies for their feasible manufacture and optimizing their formulations remain lacking. Herein, we developed hybrid homodimeric prodrug nanotherapeutics with tumor-restricted drug activation and chemophotodynamic pharmacology by leveraging the supramolecular nanoassembly of small molecules. The covalent dimerization of cytotoxic taxane chemotherapy via reactive oxygen species (ROS)-activated linker yielded a homodimeric prodrug, which was further coassembled with a ROS-generating dimeric photosensitizer. The nanoassemblies were readily refined in an amphiphilic PEGylation matrix for particle surface cloaking and in vivo intravenous injection. The nanoassemblies were optimized with favorable stability and combinatorial synergism to kill cancer cells. Upon near-infrared laser irradiation, the neighboring dimer photosensitizer generated ROS, subsequently triggering bond cleavage to facilitate drug activation, which in turn produced synergistic chemophotodynamic effects against cancer. In a preclinical model of melanoma, the intravenous administration of PEGylated nanoassemblies followed by near-infrared tumor irradiation led to significant tumor regression. Furthermore, animals treated with this efficient, photo-activatable nanotherapy exhibited low systemic toxicity even at high doses. This study describes a simple and cost-effective approach to integrate multimodal therapies by creating self-assembling small-molecule prodrugs for designing a combinatorial therapeutic nanosystem. We consider that this new paradigm holds substantial potential for advancing clinical translation.

pH-Responsive self-assembled polymer-photosensitizer conjugate for activable photodynamic therapy

This paper reports synthesis, aqueous self-assembly and relevance of the pH-triggered activable photodynamic therapy of amphiphilic polyurethane (P1S) functionalized with a heavy-atom free organic photosensitizer. Condensation polymerization between 1,4-diisocyanatobutane and two different dihydroxy monomers (one having a pendant hydrophilic wedge and the other having 1,3-dihydroxypropan-2-one with a reactive carbonyl group) in the presence of a measured amount of (S)-2-methylbutan-1-ol (chain-stopper) and DABCO catalyst produces a reactive pre-polymer P1. Hydrazide-functionalized thionated-naphthalenemonoimide (NMIS), which acts as a photosensitizer, reacted with the carbonyl-functionality of P1 to obtain the desired polymer-photosensitizer conjugate P1S in which the dye was attached to the polymer backbone via an acid-labile hydrazone linker. In water, P1S adopted an intra-chain H-bonding stabilized folded structure, which further assembled to produce a polymersome structure (Dh ≈ 200 nm), in which the hydrophobic membrane consists of aggregated NMIS and trialkoxy-benzene chromophores, as evident from UV/vis, CD and small-angle X-ray diffraction studies. In the aggregated state, NMIS loses its reactive oxygen species (ROS) generation ability and remains in a dormant state. However, under acidic conditions (pH 5.5), the photosensitizer is detached (presumably because of the cleavage of the hydrazone linker) and regains its full ROS-generation activity under photoirradiation, as evidenced from the standard DCFH assay. To test the possibility of such pH-activable intra-cellular ROS generation, P1S was treated with HeLa cells, as it is known that cancer cells are more acidic than normal cells. Indeed, photoirradiation-induced intra-cellular ROS generation was evident by the DCFH assay, resulting in efficient cell killing.

Photodynamic Therapy: Past, Current, and Future

The Greek roots of the word "photodynamic" are as follows: "phos" (φω~ς) means "light" and "dynamis" (δύναμις) means "force" or "power". Photodynamic therapy (PDT) is an innovative treatment method based on the ability of photosensitizers to produce reactive oxygen species after the exposure to light that corresponds to an absorbance wavelength of the photosensitizer, either in the visible or near-infrared range. This process results in damage to pathological cancer cells, while minimizing the impact on healthy tissues. PDT is a promising direction in the treatment of many diseases, with particular emphasis on the fight against cancer and other diseases associated with excessive cell growth. The power of light contributed to the creation of phototherapy, whose history dates back to ancient times. It was then noticed that some substances exposed to the sun have a negative effect on the body, while others have a therapeutic effect. This work provides a detailed review of photodynamic therapy, from its origins to the present day. It is surprising how a seemingly simple beam of light can have such a powerful healing effect, which is used not only in dermatology, but also in oncology, surgery, microbiology, virology, and even dentistry. However, despite promising results, photodynamic therapy still faces many challenges. Moreover, photodynamic therapy requires further research and improvement.

Supramolecular Porphyrin Photosensitizers Based on Host-Guest Recognition for In Situ Bacteria-Responsive Near-Infrared Photothermal Therapy

Antibiotic resistance resulting from the overuse of antibiotics sets a high challenge for brutal antimicrobial treatment. Although photothermal therapy (PTT) overcomes the awkward situation of antibiotic resistance, it usually mistakenly kills the beneficial bacteria strains when eliminating pernicious bacteria. Specifically recognizing and damaging the target pathogens is urgently required for PTT-mediated sterilization strategy. Based on the host-guest recognition between cucurbit[10]uril (CB[10]) and porphyrins, two water-soluble supramolecular porphyrins are designed and implement selective bactericidal effect via in situ bacteria-responsive near-infrared (NIR) PTT. With the help of CB[10], the π-π stacking and hydrophobic interactions of porphyrins are efficiently inhibited, thus contributing to a good photostability and a high photothermal conversion efficiency. Attributing to the matching reduction potential between facultative anaerobic Escherichia coli (E. coli) and porphyrins, they are selectively in situ reduced into supramolecular phlorin and supramolecular chlorin by E. coli, successfully achieving a selective sterilization against E. coli. In vivo, the in situ bacteria-responsive NIR PTT systems also promote the quick recovery of E. coli-infected abscesses and trauma on mice without inducing obvious systemic toxicity, providing a new alternative to the current antibiotics and helping relieve the global public health crisis of abusive antibiotics.

In situ pain relief during photodynamic therapy by ROS-responsive nanomicelle through blocking VGSC

Pain in photodynamic therapy (PDT), resulting from the stimulation of reactive oxygen species (ROS) and local acute inflammation, is a primary side effect of PDT that often leads to treatment interruption or termination, significantly compromising the efficacy of PDT and posing an enduring challenge for clinical practice. Herein, a ROS-responsive nanomicelle, poly(ethylene glycol)-b-poly(propylene sulphide) (PEG-PPS) encapsulated Ce6 and Lidocaine (LC), (ESCL) was used to address these problems. The tumor preferentially accumulated micelles could realize enhanced PDT effect, as well as in situ quickly release LC due to its ROS generation ability after light irradiation, which owes to the ROS-responsive property of PSS. In addition, PSS can suppress inflammatory pain which is one of the mechanisms of PDT induced pain. High LC-loaded efficiency (94.56 %) owing to the presence of the thioether bond of the PPS made an additional pain relief by inhibiting excessive inflammation besides blocking voltage-gated sodium channels (VGSC). Moreover, the anti-angiogenic effect of LC offers further therapeutic effects of PDT. The in vitro and in vivo anti-tumor results revealed significant PDT efficacy. The signals of the sciatic nerve in mice were measured by electrophysiological study to evaluate the pain relief, results showed that the relative integral area of neural signals in ESCL-treated mice decreased by 49.90 % compared to the micelles without loaded LC. Therefore, our study not only develops a very simple but effective tumor treatment PDT and in situ pain relief strategy during PDT, but also provides a quantitative pain evaluation method.

Oral Heterojunction Coupling Interventional Optical Fiber Mediates Synergistic Therapy for Orthotopic Rectal Cancer

Catalytic therapy has shown great potential for clinical application. However, conventional catalytic therapies rely on reactive oxygen species (ROS) as "therapeutic drugs," which have limitations in effectively inhibiting tumor recurrence and metastasis. Here, a biomimetic heterojunction catalyst is developed that can actively target orthotopic rectal cancer after oral administration. The heterojunction catalyst is composed of quatrefoil star-shaped BiVO4 (BVO) and ZnIn2S4 (ZIS) nanosheets through an in situ direct growth technique. Poly-norepinephrine and macrophage membrane coatings afford the biomimetic heterojunction catalyst (BVO/ZIS@M), which has high rectal cancer targeting and retention abilities. The coupled optical fiber intervention technology activates the multicenter coordination of five catalytic reactions of heterojunction catalysts, including two reduction reactions (O2→·O2 - and CO2→CO) and three oxidation reactions (H2O→·OH, GSH→GSSG, and LA→PA). These catalytic reactions not only induce immunogenic death in tumor cells through the efficient generation of ROS/CO and the consumption of GSH but also specifically lead to the use of lactic acid (LA) as an electron donor to improve catalytic activity and disrupt the LA-mediated immunosuppressive microenvironment, mediating synergistic catalysis and immunotherapy for orthotopic rectal cancer. Therefore, this optical fiber intervention triggered the combination of heterojunction catalytic therapy and immunotherapy, which exhibits prominent antitumor effects.

Advancements of Porphyrin-Derived Nanomaterials for Antibacterial Photodynamic Therapy and Biofilm Eradication

The threat posed by antibiotic-resistant bacteria and the challenge of biofilm formation has highlighted the inadequacies of conventional antibacterial therapies, leading to increased interest in antibacterial photodynamic therapy (aPDT) in recent years. This approach offers advantages such as minimal invasiveness, low systemic toxicity, and notable effectiveness against drug-resistant bacterial strains. Porphyrins and their derivatives, known for their high molar extinction coefficients and singlet oxygen quantum yields, have emerged as crucial photosensitizers in aPDT. However, their practical application is hindered by challenges such as poor water solubility and aggregation-induced quenching. To address these limitations, extensive research has focused on the development of porphyrin-based nanomaterials for aPDT, enhancing the efficacy of photodynamic sterilization and broadening the range of antimicrobial activity. This review provides an overview of various porphyrin-based nanomaterials utilized in aPDT and biofilm eradication in recent years, including porphyrin-loaded inorganic nanoparticles, porphyrin-based polymer assemblies, supramolecular assemblies, metal-organic frameworks (MOFs), and covalent organic frameworks (COFs). Additionally, insights into the prospects of aPDT is offered, highlighting its potential for practical implementation.