A Nanostructured Phthalocyanine/Albumin Supramolecular Assembly for Fluorescence Turn-On Imaging and Photodynamic Immunotherapy

Albumins constrainting the conformation of mitochondria-targeted photosensitizers for tumor-specific photodynamic therapy

Tumor ablation Preclinical organelle-targeted phototherapies have effectively achieved tumor photoablation for regenerative biomedical applications in cancer therapies. However, engineering effective phototherapy drugs with precise tumor-localization targeting and organelle direction remains challenging. Herein, we report a albumins constrainting mitochondrial-targeted photosensitizer nanoparticles (PSs@BSAs) for tumor-specific photodynamic therapy. X-ray crystallography elucidates the two-stage assembly mechanism of PSs@BSAs. Femtosecond transient absorption spectroscopy and quantum mechanical calculations reveal the implications of conformational dynamics at the excited state. PSs@BSAs can efficiently disable mitochondrial activity, and further disrupt tumor angiogenesis based on the photodynamic effect. This triggers a metabolic and oxidative stress crisis to facilitate photoablation of solid tumor and antitumor metastasis. The study fully elucidates the interdisciplinary issues of chemistry, physics, and biological interfaces, thereby opening new horizons to inspire the engineering of organelle-targeted tumor-specific photosensitizers for biomedical applications.

Benzo-pyrrolidinyl substituted silicon phthalocyanines: A novel two-photon lysosomal nanoprobe for in vitro photodynamic therapy

Lysosomes are pivotal in diverse physiological phenomena, encompassing autophagy, apoptosis, and cellular senescence. The demand for precise tumors treatment has led to the development of specific lysosome-targeting probes capable of elucidating lysosomal dynamics and facilitating targeted cell death. In this research, we report the synthesis and characterization of a novel benzopyrrolidinyl-substituted silicon phthalocyanine (Py-SiPc), designed for selective lysosome labeling and Fluorescence imaging-guided in vitro photodynamic therapy. Furthermore, we encapsulated Py-SiPc within a biocompatible nanocarrier, dipalmitoylphosphatidylethanolamine-polyethylene glycol 2000 (DSPE), to create water-soluble nanoparticles (DSPE@Py-SiPc). These nanoparticles exhibit exceptional lysosome labeling capabilities, as evidenced by bioimaging techniques. Upon exposure to laser irradiation, DSPE@Py-SiPc efficiently induces the production of reactive oxygen species, impairing lysosomal function and triggering lysosomal-mediated cell death. The DSPE@Py-SiPc system emerges as a promising photosensitizer.

Near-Infrared Chemiluminophore Switches Photodynamic Processes via Protein Complexation for Biomarker-Activatable Cancer Therapy

Despite the potential in cancer therapy, phototheranostic agents often face two challenges: limited diagnostic sensitivity due to tissue autofluorescence and suboptimal therapeutic efficacy due to the Type-II photodynamic process with the heavy oxygen reliance. In contrast, chemiluminescent theranostic agents without the requirement of real-time light excitation can address the issue of tissue autofluorescence, which however have been rarely reported for photodynamic therapy (PDT), not to mention less oxygen-dependent Type-I PDT. In this work, we synthesize near-infrared (NIR) chemiluminophores with the specific binding towards human serum albumin (HSA) to form chemiluminophore-protein complex for cancer detection and photodynamic therapy. Interestingly, after the complexation with HSA, the chemiluminescence (CL) intensities of chemiluminophores are enhanced by over 10-fold; meanwhile, the photodynamic process switches from Type-II (singlet-oxygen-generation dominated) to Type-I (superoxide anion and hydroxyl radical dominated), while the previously reported activated chemiluminophore with non-specific HSA binding can't switch photodynamic process. Based on the optimal chemiluminophore, a nitroreductase-activatable CL probe-protein complex is synthesized, which specially turns on its CL and Type-I PDT in hypoxic tumors for precision therapy. Thus, this study provides a complexation strategy to improve phototheranostic performance of chemiluminophores.

NIR-activated multifunctional agents for the combined application in cancer imaging and therapy

Anticancer therapies that combine both diagnostic and therapeutic capabilities hold significant promise for enhancing treatment efficacy and patient outcomes. Among these, agents responsive to near-infrared (NIR) photons are of particular interest due to their negligible toxicity and multifunctionality. These compounds are not only effective in photodynamic therapy (PDT), but also serve as contrast agents in various imaging modalities, including fluorescence and photoacoustic imaging. In this review, we explore the photophysical and photochemical properties of NIR-activated porphyrin, cyanine, and phthalocyanines derivatives as well as aggregation-induced emission compounds, highlighting their application in synergistic detection, diagnosis, and therapy. Special attention is given to the design and optimization of these agents to achieve high photostability, efficient NIR absorption, and significant yields of fluorescence, heat, or reactive oxygen species (ROS) generation depending on the application. Additionally, we discuss the incorporation of these compounds into nanocarriers to enhance their solubility, stability, and target specificity. Such nanoparticle-based systems exhibit improved pharmacokinetics and pharmacodynamics, facilitating more effective tumor targeting and broadening the application range to photoacoustic imaging and photothermal therapy. Furthermore, we summarize the application of these NIR-responsive agents in multimodal imaging techniques, which combine the advantages of fluorescence and photoacoustic imaging to provide comprehensive diagnostic information. Finally, we address the current challenges and limitations of photodiagnosis and phototherapy and highlight some critical barriers to their clinical implementation. These include issues related to their phototoxicity, limited tissue penetration, and potential off-target effects. The review concludes by highlighting future research directions aimed at overcoming these obstacles, with a focus on the development of next-generation agents and platforms that offer enhanced therapeutic efficacy and imaging capabilities in the field of cancer treatment.

Reversible pH-switchable NIR-II nano-photosensitizer for precise imaging and photodynamic therapy of tumors

Photodynamic therapy (PDT) has attracted widespread attention from researchers as an emerging cancer treatment method. There have been many reports on various types of NIR-II photosensitizers for imaging and treatment of tumor sites. However, there are few reports on the development of NIR-II organic small molecule photosensitizers that have intelligent response to the tumor microenvironment, precise imaging, real-time treatment, and high biocompatibility. In this work, we developed a series of NIR-II photosensitizers (RBTs) with near-infrared excitation, good photostability, and large Stokes shift. Among them, RBT-Br exhibited higher reactive oxygen species (ROS) generation efficiency due to the introduction of halogen heavy atoms to enhance intersystem crossing (ISC). It is noteworthy that RBT-Br can generate singlet oxygen (1O2) and superoxide anion radicals (•O2-) simultaneously under 730 nm laser. Subsequently, we used molecular engineering technology to construct three pH-responsive NIR-II photosensitizers (RBT-pHs) by utilizing the closure of the lactam ring, among which RBT-pH-1 (pKa = 6.78) is able to be directionally activated under the stimulation of tumor micro-acid environment, with its fluorescence emission window reaching 933 nm. Subsequently, RBT-pH-1 NPs encapsulated in DSPE-mPEG5k were applied for PDT treatment of mouse tumors. The results showed that RBT-pH-1 NPs were activated by the acidic tumor microenvironment and generated ROS under laser excitation, exhibiting precise tumor imaging and significant tumor growth inhibition. We look forward to these multifunctional NIR-II organic small molecule photosensitizers providing a more efficient approach for clinical treatment of tumors. STATEMENT OF SIGNIFICANCE: A reversible pH-switchable NIR-II nano-photosensitizer RBT-pH-1 NPs (pKa = 6.76) is developed for precise imaging and PDT therapy of mouse tumors, which can be effectively used for targeted enrichment and activation of tumor micro-acid environments. The results show that this NIR-II photosensitizer generates ROS through tumor micro-acid environment stimulation and laser triggering, showing precise tumor imaging guidance and significant tumor growth inhibition.

Chitosan/agarose hydrogel dressing: pH response real-time monitoring and chemo-/photodynamic therapy synergistic treatment of infected wounds

The early diagnosis and real-time monitoring of bacterial infections are of great significance for the establishment of integrated diagnosis and treatment systems. In this study, a pH-responsive smart hydrogel patch system, named CABP, was developed to monitor and treat wound infections. CABP has a sandwich structure, with non-woven fabric/chitosan (NF/CS) as the intermediate skeleton layer, Agarose/chitosan/Bromothymol Blue (AG/CS/BTB) hydrogel as the detection layer, and Agarose/chitosan/phthalocyanine (AG/CS/Pc) hydrogel as the treatment layer. When Staphylococcus aureus (S. aureus) infection occurs, the pH of the environment decreases, which triggers the CABP to change from its original blue color to yellow, achieving an intuitive visual transformation. Moreover, the hydrogel patch showed a significant inhibition rate of up to 99.99971 % against S. aureus under 660 nm light radiation, showing a good photodynamic therapy (PDT)/ chemotherapy (CT) synergistic effect. In addition, CABP showed excellent antibacterial and wound healing effects on S. aureus infection in a full-layer skin defect experiment. In short, the patch system is simple to prepare and easy to use, and can provide important research value for the integrated diagnosis and treatment system in biomedical applications.

CuPc-Fe@BSA nanocomposite: Intracellular acid-sensitive aggregation for enhanced sonodynamic and chemo-therapy

Due to their rigid π-conjugated macrocyclic structure, organic sonosensitizers face significant aggregation in physiological conditions, hindering the production of reactive oxygen species (ROS). An acid-sensitive nanoassembly was developed to address this issue and enhance sonodynamic therapy (SDT) and emission. Initially, copper phthalocyanine (CuPc) was activated using a H2SO4-assisted hydrothermal method to introduce multiple functional groups (-COOH, -OH, and -SO3H), disrupting strong π-π stacking and promoting ROS generation and emission. Subsequently, negatively charged CuPc-SO4 was incorporated into bovine serum albumin (BSA) to form CuPc-Fe@BSA nanoparticles (10 nm) with Fe3+ ions serving as linkers. In acidic conditions, protonation of CuPc-SO4 and BSA weakened the interactions, leading to Fe3+ release and nanostructure dissociation. Protonated CuPc-SO4 tended to self-aggregate into nanorods. This acidity-sensitive aggregation is vital for achieving specific accumulation within the tumor microenvironment (TME), thereby enhancing retention and SDT efficacy. Prior to this, the nanocomposites demonstrated cycling stability under neutral conditions. Additionally, the released Fe ions exhibited mimicry of glutathione peroxidase and peroxidase activity for chemotherapy (CDT). The synergistic effect of SDT and CDT increased intracellular oxidative stress, causing mitochondrial injury and ferroptosis. Furthermore, the combined therapy induced immunogenic cell death (ICD), effectively activating anticancer immune responses and suppressing metastasis and recurrence.

Remote Control of Energy Transformation-Based Cancer Imaging and Therapy

Cancer treatment requires precise tumor-specific targeting at specific sites that allows for high-resolution diagnostic imaging and long-term patient-tailorable cancer therapy; while, minimizing side effects largely arising from non-targetability. This can be realized by harnessing exogenous remote stimuli, such as tissue-penetrative ultrasound, magnetic field, light, and radiation, that enable local activation for cancer imaging and therapy in deep tumors. A myriad of nanomedicines can be efficiently activated when the energy of such remote stimuli can be transformed into another type of energy. This review discusses the remote control of energy transformation for targetable, efficient, and long-term cancer imaging and therapy. Such ultrasonic, magnetic, photonic, radiative, and radioactive energy can be transformed into mechanical, thermal, chemical, and radiative energy to enable a variety of cancer imaging and treatment modalities. The current review article describes multimodal energy transformation where a serial cascade or multiple types of energy transformation occur. This review includes not only mechanical, chemical, hyperthermia, and radiation therapy but also emerging thermoelectric, pyroelectric, and piezoelectric therapies for cancer treatment. It also illustrates ultrasound, magnetic resonance, fluorescence, computed tomography, photoluminescence, and photoacoustic imaging-guided cancer therapies. It highlights afterglow imaging that can eliminate autofluorescence for sustained signal emission after the excitation.

Heterogeneous-Structure-Based AuNBs@TiO2 Nano-Photosensitizers for Computed Tomography Imaging Guided NIR-II Photodynamic Therapy and Cancer Metastatic Prevention

Photodynamic therapy (PDT) is a minimally invasive cancer treatment that, despite its significant attention, faces limitations in penetration depth, which restrict its effectiveness. Herein, it is found that gold nanobipyramid (AuNBs) coated with TiO2 can form a core-shell heterogeneous structure (AuNBs@TiO2) with strong absorption at second near infrared (NIR-II) region. A substantial quantity of reactive oxygen species (ROS), including singlet oxygen (1O2), superoxide anion radicals, and hydroxyl radicals, can be rapidly generated when subjecting the AuNBs@TiO2 aqueous suspension to 1064 nm laser irradiation. The quantum yield for sensitization of 1O2 by AuNBs@TiO2 is 0.36 at 1064 nm light excitation. In addition, the Au element as high-Z atoms in the nanosystem can improve the ability of computed tomographic (CT) imaging. As compared to commercial iohexol, the AuNBs@TiO2 nanoparticle exhibits significantly better CT imaging effect, which can be used to guide PDT. In addition, the nano-photosensitizer shows a remarkable therapeutic effect against established solid tumors and prevents tumor metastasis and potentiates immune checkpoint blockade therapy. More importantly, here the great potentials of AuNBs@TiO2 are highlighted as a theranostic platform for CT-guided cancer photodynamic immunotherapy.

Supramolecular dye nanoassemblies for advanced diagnostics and therapies

Dyes have conventionally been used in medicine for staining cells, tissues, and organelles. Since these compounds are also known as photosensitizers (PSs) which exhibit photoresponsivity upon photon illumination, there is a high desire towards formulating these molecules into nanoparticles (NPs) to achieve improved delivery efficiency and enhanced stability for novel imaging and therapeutic applications. Furthermore, it has been shown that some of the photophysical properties of these molecules can be altered upon NP formation thereby playing a major role in the outcome of their application. In this review, we primarily focus on introducing dye categories, their formulation strategies and how these strategies affect their photophysical properties in the context of photothermal and non-photothermal applications. More specifically, the most recent progress showing the potential of dye supramolecular assemblies in modalities such as photoacoustic and fluorescence imaging, photothermal and photodynamic therapies as well as their employment in photoablation as a novel modality will be outlined. Aside from their photophysical activity, we delve shortly into the emerging application of dyes as drug stabilizing agents where these molecules are used together with aggregator molecules to form stable nanoparticles.

Near-Infrared-II Nanomaterials for Activatable Photodiagnosis and Phototherapy

Near-Infrared-II (NIR-II) spans wavelengths between 1,000 to 1,700 nanometers, featuring deep tissue penetration and reduced tissue scattering and absorption characteristics, providing robust support for cancer treatment and tumor imaging research. This review explores the utilization of activatable NIR-II photodiagnosis and phototherapy based on tumor microenvironments (e. g., reactive oxygen species, pH, glutathione, hypoxia) and external stimulation (e. g., laser, ultrasound, photothermal) for precise tumor treatment and imaging. Special emphasis is placed on the advancements and advantages of activatable NIR-II nanomedicines in novel therapeutic modalities like photodynamic therapy, photothermal therapy, and photoacoustic imaging. This encompasses achieving deep tumor penetration, real-time monitoring of the treatment process, and obtaining high-resolution, high signal-to-noise ratio images even at low material concentrations. Lastly, from a clinical perspective, the challenges faced by activatable NIR-II phototherapy are discussed, alongside potential strategies to overcome these hurdles.

Recent Progress in Anti-Tumor Nanodrugs Based on Tumor Microenvironment Redox Regulation

The growth state of tumor cells is strictly affected by the specific abnormal redox status of the tumor microenvironment (TME). Moreover, redox reactions at the biological level are also central and fundamental to essential energy metabolism reactions in tumors. Accordingly, anti-tumor nanodrugs targeting the disruption of this abnormal redox homeostasis have become one of the hot spots in the field of nanodrugs research due to the effectiveness of TME modulation and anti-tumor efficiency mediated by redox interference. This review discusses the latest research results of nanodrugs in anti-tumor therapy, which regulate the levels of oxidants or reductants in TME through a variety of therapeutic strategies, ultimately breaking the original "stable" redox state of the TME and promoting tumor cell death. With the gradual deepening of study on the redox state of TME and the vigorous development of nanomaterials, it is expected that more anti-tumor nano drugs based on tumor redox microenvironment regulation will be designed and even applied clinically.

Nanodrug Delivery Systems in Antitumor Immunotherapy

Cancer has become one of the most important factors threatening human health, and the global cancer burden has been increasing rapidly. Immunotherapy has become another clinical research hotspot after surgery, chemotherapy, and radiotherapy because of its high efficiency and tumor metastasis prevention. However, problems such as lower immune response rate and immune-related adverse reaction in the clinical application of immunotherapy need to be urgently solved. With the development of nanodrug delivery systems, various nanocarrier materials have been used in the research of antitumor immunotherapy with encouraging therapeutic results. In this review, we mainly summarized the combination of nanodrug delivery systems and immunotherapy from the following 4 aspects: (a) nanodrug delivery systems combined with cytokine therapy to improve cytokines delivery in vivo; (b) nanodrug delivery systems provided a suitable platform for the combination of immune checkpoint blockade therapy with other tumor treatments; (c) nanodrug delivery systems helped deliver antigens and adjuvants for tumor vaccines to enhance immune effects; and (d) nanodrug delivery systems improved tumor treatment efficiency and reduced toxicity for adoptive cell therapy. Nanomaterials chosen by researchers to construct nanodrug delivery systems and their function were also introduced in detail. Finally, we discussed the current challenges and future prospects in combining nanodrug delivery systems with immunotherapy.

Acid-triggered controlled release and fluorescence-switchable phthalocyanine nanoassemblies combined with O2-economizer for tumor imaging and collaborative photodynamic antitumor therapy

Photodynamic therapy (PDT) has emerged as a highly efficacious therapeutic modality for malignant tumors owing to its non-invasive property and minimal adverse effects. However, the pervasive hypoxic microenvironment within tumors significantly compromises the efficacy of oxygen-dependent PDT, posing a formidable challenge to the advancement of high-efficiency PDT. Here, we developed a nanostructured photosensitizer (PS) assembled by cationic and anionic zinc phthalocyanines to load oxygen-throttling drug atovaquone (ATO), which was subsequently coated with polydopamine to obtain the final product ATO/ZnPc-CA@DA. ATO/ZnPc-CA@DA exhibited excellent stability, particularly in the blood milieu. Interestingly, the acidic microenvironment can trigger drug release from ATO/ZnPc-CA@DA, leading to a significant enhancement in fluorescence and an augmented generation of reactive oxygen species (ROS). ATO/ZnPc-CA@DA can induce synergistic cytotoxicity of PS and ATO, and significantly enhance the killing ability against tumor cells under hypoxic conditions. The mechanism underlying cytotoxicity of ATO/ZnPc-CA@DA was demonstrated to be associated with augmented cell apoptosis, disruption of mitochondrial membrane potential, diminished ATP production, heightened intracellular ROS generation, and reduced intracellular oxygen consumption. The animal experiments indicated that ATO/ZnPc-CA@DA possessed enhanced tumor targeting capability, along with a reduction in PS distribution within normal organs. Furthermore, ATO/ZnPc-CA@DA exhibited enhanced inhibitory effect on tumor growth and caused aggravated damage to tumor tissue. The construction strategy of nanostructured PS and the synergistic antitumor principle of combined oxygen-throttling drugs can be applied to other PSs, thereby advancing the development of photodynamic antitumor therapy and promoting the clinical translation.

Mitochondrial Disruption Nanosystem Simultaneously Depressed Programmed Death Ligand-1 and Transforming Growth Factor-β to Overcome Photodynamic Immunotherapy Resistance

Currently, limited photosensitizers possess the capacity to reverse tumor hypoxia and reduce programmed death ligand-1 (PD-L1) and transforming growth factor-β (TGF-β) expression simultaneously, hindering the perfect photodynamic therapy (PDT) effect due to acquired immune resistance and the tumor hypoxic microenvironment. To tackle these challenges, in this research, we demonstrated that mitochondrial energy metabolism depression can be utilized as an innovative and efficient approach for reducing the expression of PD-L1 and TGF-β simultaneously, which may offer a design strategy for a more ideal PDT nanosystem. Through proteomic analysis of 5637 cells, we revealed that tamoxifen (TMX) can incredibly regulate PD-L1 expression in tumor cells. Then, to selectively deliver clinically used mitochondrial energy metabolism depressant TMX to solid tumors as well as design an ideal PDT nanosystem, we synthesized MHI-TMX@ALB by combining a mitochondria-targeted heptamethine cyanine PDT-dye MHI with TMX through self-assembly with albumin (ALB). Interestingly enough, the MHI-TMX@ALB nanoparticle demonstrated effective reversion of tumor hypoxia and inhibition of PD-L1 protein expression at a lower dosage (7.5 times to TMX), which then enhanced the efficacy of photodynamic immunotherapy via enhancing T-cell infiltration. Apart from this, by leveraging the heptamethine dye's targeting capacity toward tumors and TMX's role in suppressing TGF-β, MHI-TMX@ALB also more effectively mitigated 4T1 tumor lung metastasis development. All in all, the MHI-TMX@ALB nanoparticle could be used as a multifunctional economical PD-L1 and TGF-β codepression immune-regulating strategy, broadening the potential clinical applications for a more ideal PDT nanosystem.

Innovative Design Strategies Advance Biomedical Applications of Phthalocyanines

Owing to their long absorption wavelengths, high molar absorptivity, and tunable photosensitivity, phthalocyanines have been widely used in photodynamic therapy (PDT). However, phthalocyanines still face the drawbacks of poor targeting, "always-on" photosensitizing properties, and unsatisfactory therapeutic efficiency, which limit their wide applications in biomedical fields. Thus, new design strategies such as modification of targeting molecules, formation of nanoparticles, and activating photosensitizers are developed to improve the above defects. Notably, recent studies have shown that novel phthalocyanines are not only used in fluorescence imaging and PDT, but also in photoacoustic imaging, photothermal imaging, sonodynamic therapy, and photothermal therapy. This review focuses on recent design strategies, applications in biomedicine, and clinical development of phthalocyanines, providing ideas and references for the design and application of phthalocyanine, so as to promote their future transformation into clinical applications.

Promotion of ICD via Nanotechnology

Immunotherapy represents the most promising treatment strategy for cancer, but suffers from compromised therapeutic efficiency due to low immune activity of tumor cells and an immunosuppressive microenvironment, which significantly hampers the clinical translations of this treatment strategy. To promote immunotherapy with desired therapeutic efficiency, immunogenic cell death (ICD), a particular type of death capable of reshaping body's antitumor immune activity, has drawn considerable attention due to the potential to stimulate a potent immune response. Still, the potential of ICD effect remains unsatisfactory because of the intricate tumor microenvironment and multiple drawbacks of the used inducing agents. ICD has been thoroughly reviewed so far with a general classification of ICD as a kind of immunotherapy strategy and repeated discussion of the related mechanism. However, there are no published reviews, to the authors' knowledge, providing a systematic summarization on the enhancement of ICD via nanotechnology. For this purpose, this review first discusses the four stages of ICD according to the development mechanisms, followed by a comprehensive description on the use of nanotechnology to enhance ICD in the corresponding four stages. The challenges of ICD inducers and possible solutions are finally summarized for future ICD-based enhanced immunotherapy.

A smart and visible way to switch the aromaticity of silicon(IV) phthalocyanines

Unlike traditional methods of modifying phthalocyanines (Pcs), we herein report a smart and visible way to switch the aromaticity of silicon(IV) phthalocyanines via a reversible nucleophilic addition reaction of the Pc skeleton induced by alkalis and acids, leading to an interesting allochroism phenomenon and the switching of photosensitive activities.

Phthalocyanine-Blue Nanoparticles for the Direct Visualization of Tumors with White Light Illumination

The current standard of care for colon cancer surveillance relies heavily on white light endoscopy (WLE). However, dysplastic lesions that are not visible to the naked eye are often missed when conventional WLE equipment is used. Although dye-based chromoendoscopy shows promise, current dyes cannot delineate tumor tissues from surrounding healthy tissues accurately. The goal of the present study was to screen various phthalocyanine (PC) dye-loaded micelles for their ability to improve the direct visualization of tumor tissues under white light following intravenous administration. Zinc PC (tetra-tert-butyl)-loaded micelles were identified as the optimal formulation. Their accumulation within syngeneic breast tumors led the tumors to turn dark blue in color, making them clearly visible to the naked eye. These micelles were similarly able to turn spontaneous colorectal adenomas in Apc+/Min mice a dark blue color for easy identification and could enable clinicians to more effectively detect and remove colonic polyps.

Understanding the Photodynamic Therapy Induced Bystander and Abscopal Effects: A Review

Photodynamic therapy (PDT) is a clinically approved minimally/non-invasive treatment modality that has been used to treat various conditions, including cancer. The bystander and abscopal effects are two well-documented significant reactions involved in imparting long-term systemic effects in the field of radiobiology. The PDT-induced generation of reactive oxygen and nitrogen species and immune responses is majorly involved in eliciting the bystander and abscopal effects. However, the results in this regard are unsatisfactory and unpredictable due to several poorly elucidated underlying mechanisms and other factors such as the type of cancer being treated, the irradiation dose applied, the treatment regimen employed, and many others. Therefore, in this review, we attempted to summarize the current knowledge regarding the non-targeted effects of PDT. The review is based on research published in the Web of Science, PubMed, Wiley Online Library, and Google Scholar databases up to June 2023. We have highlighted the current challenges and prospects in relation to obtaining clinically relevant robust, reproducible, and long-lasting antitumor effects, which may offer a clinically viable treatment against tumor recurrence and metastasis. The effectiveness of both targeted and untargeted PDT responses and their outcomes in clinics could be improved with more research in this area.

Reverse-QTY code design of active human serum albumin self-assembled amphiphilic nanoparticles for effective anti-tumor drug doxorubicin release in mice

Human serum albumin (HSA) is a highly water-soluble protein with 67% alpha-helix content and three distinct domains (I, II, and III). HSA offers a great promise in drug delivery with enhanced permeability and retention effect. But it is hindered by protein denaturation during drug entrapment or conjugation that result in distinct cellular transport pathways and reduction of biological activities. Here we report using a protein design approach named reverse-QTY (rQTY) code to convert specific hydrophilic alpha-helices to hydrophobic to alpha-helices. The designed HSA undergo self-assembly of well-ordered nanoparticles with highly biological actives. The hydrophilic amino acids, asparagine (N), glutamine (Q), threonine (T), and tyrosine (Y) in the helical B-subdomains of HSA were systematically replaced by hydrophobic leucine (L), valine (V), and phenylalanine (F). HSArQTY nanoparticles exhibited efficient cellular internalization through the cell membrane albumin binding protein GP60, or SPARC (secreted protein, acidic and rich in cysteine)-mediated pathways. The designed HSArQTY variants displayed superior biological activities including: i) encapsulation of drug doxorubicin, ii) receptor-mediated cellular transport, iii) tumor cell targeting, and iv) antitumor efficiency compare to denatured HSA nanoparticles. HSArQTY nanoparticles provided superior tumor targeting and antitumor therapeutic effects compared to the albumin nanoparticles fabricated by antisolvent precipitation method. We believe that the rQTY code is a robust platform for specific hydrophobic modification of functional hydrophilic proteins with clear-defined binding interfaces.

Morpholinyl silicon phthalocyanine nanoparticles with lysosome cell death and two-photon imaging functions for in vitro photodynamic therapy of cancer cells

The lysosome is an important target for realizing antitumor therapy. Lysosomal cell death exerts significant therapeutic effects on apoptosis and drug-resistance. The development of lysosome-targeting nanoparticles to obtain efficient cancer treatment is challenging. In this article, nanoparticles composed of DSPE@M-SiPc and possessing bright two-photon fluorescence, lysosome targeting ability, and photodynamic therapy multifunctionalities are prepared by encapsulating morpholinyl-substituted silicon phthalocyanine (M-SiPc) with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(poly(ethylene glycol))-2000] (DSPE). Two photon fluorescence bioimaging showed that M-SiPc and DSPE@M-SiPc mainly locate in lysosomes after cellular internalization. Upon irradiation, DSPE@M-SiPc effectively generates reactive oxygen species and damages the function of lysosome, subsequently leading to lysosomal cell death. DSPE@M-SiPc is a promising photosensitizer for cancer treatment.

Cancer Immunotherapy Elicited by Immunogenic Cell Death Based on Smart Nanomaterials

Cancer immunotherapy has been a revolutionary cancer treatment modality because it can not only eliminate primary tumors but also prevent metastases and recurrent tumors. Immunogenic cell death (ICD) induced by various treatment modalities, including chemotherapy, phototherapy, and radiotherapy, converts dead cancer cells into therapeutic vaccines, eliciting a systemic antigen-specific antitumor. However, the outcome effect of cancer immunotherapy induced by ICD has been limited due to the low accumulation efficiency of ICD inducers in the tumor site and concomitant damage to normal tissues. The boom in smart nanomaterials is conducive to overcoming these hurdles owing to their virtues of good stability, targeted lesion site, high bioavailability, on-demand release, and good biocompatibility. Herein, the design of targeted nanomaterials, various ICD inducers, and the applications of nanomaterials responsive to different stimuli, including pH, enzymes, reactive oxygen species, or dual responses are summarized. Furthermore, the prospect and challenges are briefly outlined to provide reference and inspiration for designing novel smart nanomaterials for immunotherapy induced by ICD.

Nanostructured organic photosensitizer aggregates in disease phototheranostics

Aggregate science provides promising opportunities for the discovery of novel disease phototheranostics. Under the guidance of aggregology and the Jablonski energy level diagram, photosensitizer aggregates with tunable photophysical properties can consequently result in tailorable diagnosis and treatment modalities. This review summarizes recent advances in the formation of nanostructured organic photosensitizer aggregates, their photophysical processes (e.g., radiative emission, vibrational relaxation, and intersystem crossing), and particularly, their applications in disease phototheranostics such as fluorescence imaging and sensing, photothermal therapy, photoacoustic imaging, and photodynamic therapy. It is expected that this comprehensive summary will provide guidance for the construction of nanostructured organic photosensitizer aggregates, for establishment of aggregation-photophysical property relationships and the development of novel disease phototheranostic nanomedicines. Teaser: This article reviews the electron-delocalized π system-caused formation of nanostructured organic photosensitizer aggregates, which undergo radiative emission, vibrational relaxation, or intersystem crossing pathways to achieve fluorescence imaging and sensing, photothermal therapy, photoacoustic imaging, and photodynamic therapy.

Immuno-photodynamic Therapy (IPDT): Organic Photosensitizers and Their Application in Cancer Ablation

Photosensitizer-based photodynamic therapy (PDT) has been considered as a promising modality for fighting diverse types of cancers. PDT directly inhibits local tumors by a minimally invasive strategy, but it seems to be incapable of achieving complete eradication and fails to prevent metastasis and recurrence. Recently, increasing events proved that PDT was associated with immunotherapy by triggering immunogenic cell death (ICD). Upon a specific wavelength of light irradiation, the photosensitizers will turn the surrounding oxygen molecules into cytotoxic reactive oxygen species (ROS) for killing the cancer cells. Simultaneously, the dying tumor cells release tumor-associated antigens, which could improve immunogenicity to activate immune cells. However, the progressively enhanced immunity is typically limited by the intrinsic immunosuppressive tumor microenvironment (TME). To overcome this obstacle, immuno-photodynamic therapy (IPDT) has come to be one of the most beneficial strategies, which takes advantage of PDT to stimulate the immune response and unite immunotherapy for inducing immune-OFF tumors to immune-ON ones, to achieve systemic immune response and prevent cancer recurrence. In this Perspective, we provide a review of recent advances in organic photosensitizer-based IPDT. The general process of immune responses triggered by photosensitizers (PSs) and how to enhance the antitumor immune pathway by modifying the chemical structure or conjugating with a targeting component was discussed. In addition, future perspectives and challenges associated with IPDT strategies are also discussed. We hope this Perspective could inspire more innovative ideas and provide executable strategies for future developments in the war against cancer.

Recent Progress in Carrier-Free Nanomedicine for Tumor Phototherapy

Safe and effective strategies are urgently needed to fight against the life-threatening diseases of various cancers. However, traditional therapeutic modalities, such as radiotherapy, chemotherapy and surgery, exhibit suboptimal efficacy for malignant tumors owing to the serious side effects, drug resistance and even relapse. Phototherapies, including photodynamic therapy (PDT) and photothermal therapy (PTT), are emerging therapeutic strategies for localized tumor inhibition, which can produce a large amount of reactive oxygen species (ROS) or elevate the temperature to initiate cell death by non-invasive irradiation. In consideration of the poor bioavailability of phototherapy agents (PTAs), lots of drug delivery systems have been developed to enhance the tumor targeted delivery. Nevertheless, the carriers of drug delivery systems inevitably bring biosafety concerns on account of their metabolism, degradation, and accumulation. Of note, carrier-free nanomedicine attracts great attention for clinical translation with synergistic antitumor effect, which is characterized by high drug loading, simplified synthetic method and good biocompatibility. In this review, the latest advances of phototherapy with various carrier-free nanomedicines are summarized, which may provide a new paradigm for the future development of nanomedicine and tumor precision therapy.

Repeated photodynamic therapy mediates the abscopal effect through multiple innate and adaptive immune responses with and without immune checkpoint therapy

In combination with immune checkpoint inhibitors, photodynamic therapy can induce robust immune responses capable of preventing local tumor recurrence and delaying the growth of distant, untreated disease (ie. the abscopal effect). Previously, we found that repeated photodynamic therapy (R-PDT) using porphyrin lipoprotein (PLP) as a photosensitizer, without the addition of an immune checkpoint inhibitor, can induce the abscopal effect. To understand why PLP mediated R-PDT alone can induce the abscopal effect, and how the addition of an immune checkpoint inhibitor can further strengthen the abscopal effect, we investigated the broader immune mechanisms facilitated by R-PDT and combination R-PDT + anti-PD-1 monoclonal antibody (αPD-1) in a highly aggressive, subcutaneous AE17-OVA mesothelioma dual tumor-bearing C57BL/6 mice. We found a 46.64-fold and 61.33-fold increase in interleukin-6 (IL-6) after R-PDT and combination R-PDT + αPD-1 relative to PBS respectively, suggesting broad innate immune activation. There was a greater propensity for antigen presentation in the spleen and distal, non-irradiated tumor draining lymph nodes, as dendritic cells and macrophages had increased expression of MHC class II, CD80, and CD86, after R-PDT and combination R-PDT + αPD-1. Concurrently, there was a shift in the proportions of CD4+ T cell subsets in the spleen, and an increase in the frequency of CD8+ T cells in the distal, non-irradiated tumor draining lymph nodes. While R-PDT had an acceptable safety profile, combination R-PDT + αPD-1 induced 1.26-fold higher serum potassium and 1.33-fold phosphorus, suggestive of mild laboratory tumor lysis syndrome. Histology revealed an absence of gross inflammation in critical organs after R-PDT and combination R-PDT + αPD-1 relative to PBS-treated mice. Taken together, our findings shed light on how the abscopal effect can be induced by PDT and strengthened by combination R-PDT + αPD-1, and suggests minimal toxicities after R-PDT.

Cascade Immune Activation of Self-Delivery Biomedicine for Photodynamic Immunotherapy Against Metastatic Tumor

Photodynamic therapy (PDT) can generate reactive oxygen species (ROS) to cause cell apoptosis and induce immunogenic cell death (ICD) to activate immune response, becoming a promising antitumor modality. However, the overexpressions of indoleamine 2,3-dioxygenase (IDO) and programmed cell death ligand 1 (PD-L1) on tumor cells would reduce cytotoxic T cells infiltration and inhibit the immune activation. In this paper, a simple but effective nanosystem is developed to solve these issues for enhanced photodynamic immunotherapy. Specifically, it has been constructed a self-delivery biomedicine (CeNB) based on photosensitizer chlorine e6 (Ce6), IDO inhibitor (NLG919), and PD1/PDL1 blocker (BMS-1) without the need for extra excipients. Of note, CeNB possesses fairly high drug content (nearly 100%), favorable stability, and uniform morphology. More importantly, CeNB-mediated IDO inhibition and PD1/PDL1 blockade greatly improve the immunosuppressive tumor microenvironments to promote immune activation. The PDT of CeNB not only inhibits tumor proliferation but also induces ICD response to activate immunological cascade. Ultimately, self-delivery CeNB tremendously suppresses the tumor growth and metastasis while leads to a minimized side effect. Such simple and effective antitumor strategy overcomes the therapeutic resistance against PDT-initiated immunotherapy, suggesting a potential for metastatic tumor treatment in clinic.

A carboxylesterase-activatable near-infrared phototheranostic probe for tumor fluorescence imaging and photodynamic therapy

Phototheranostic probes have been proven to be a promising option for cancer diagnosis and treatment. However, near-infrared phototheranostic probes with specific tumor microenvironment responsiveness are still in demand. In this paper, a carboxylesterase (CES)-responsive near-infrared phototheranostic probe was developed by incorporating 6-acetamidohexanoic acid into a hemicyanine dye through an ester bond. The probe exhibits highly sensitive and selective fluorescence enhancement towards CES because CES-catalyzed cleavage of the ester bond leads to the release of the fluorophore. By virtue of its near-infrared analytical wavelengths and high sensitivity, the probe has been employed for endogenous CES activatable fluorescence imaging of tumor cells. Moreover, under 660 nm laser irradiation, the probe can generate toxic reactive oxygen species and efficiently kill tumor cells, with low cytotoxicity in dark. As far as we know, the probe was the first CES-responsive phototheranostic probe with both near-infrared analytical wavelengths and photosensitive capacity, which may be useful in the real-time and in situ imaging of CES as well as imaging-guided photodynamic therapy of tumors. Therefore, the proposed probe may have wide application prospect in cancer theranostics.

Multifunctional Hollow MnO2 @Porphyrin@Bromelain Nanoplatform for Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) has been showing great potential in cancer treatment. However, the efficacy of PDT is always limited by the intrinsic hypoxic tumor microenvironment (TME) and the low accumulation efficiency of photosensitizers in tumors. To address the issue, a multifunctional hollow multilayer nanoplatform (H-MnO₂ @TPyP@Bro) comprising manganese dioxide, porphyrin (TPyP) and bromelain (Bro), is developed for enhanced photodynamic therapy. MnO₂ catalyzes the intracellular hydrogen peroxide (H₂ O₂ ) to produce oxygen (O₂ ), reversing the hypoxic TME in vivo. The generated O₂ is converted into singlet oxygen (¹ O₂ ) by the TPyP shell under near-infrared light, which can inhibit tumor proliferation. Meanwhile, the Bro can digest collagen in the extracellular matrix around the tumor, and can promote the accumulation of H-MnO₂ @TPyP@Bro in the deeper tumor tissue, further improving the therapeutic effect of PDT. In addition, MnO₂ can react with the overexpressed glutathione in TME to release Mn²⁺ . Consequently, Mn²⁺ not only induces chemo-dynamic therapy based on Fenton reaction by converting H₂ O₂ into hydroxyl radicals, but also activates the Mn²⁺ -based magnetic resonance imaging. Therefore, the developed H-MnO₂ @TPyP@Bro nanoplatform can effectively modulate the unfavorable TME and overcome the limitations of conventional PDT for cancer diagnostic and therapeutic.

Nanomaterials: small particles show huge possibilities for cancer immunotherapy

With the economy's globalization and the population's aging, cancer has become the leading cause of death in most countries. While imposing a considerable burden on society, the high morbidity and mortality rates have continuously prompted researchers to develop new oncology treatment options. Anti-tumor regimens have evolved from early single surgical treatment to combined (or not) chemoradiotherapy and then to the current stage of tumor immunotherapy. Tumor immunotherapy has undoubtedly pulled some patients back from the death. However, this strategy of activating or boosting the body's immune system hardly benefits most patients. It is limited by low bioavailability, low response rate and severe side effects. Thankfully, the rapid development of nanotechnology has broken through the bottleneck problem of anti-tumor immunotherapy. Multifunctional nanomaterials can not only kill tumors by combining anti-tumor drugs but also can be designed to enhance the body's immunity and thus achieve a multi-treatment effect. It is worth noting that the variety of nanomaterials, their modifiability, and the diversity of combinations allow them to shine in antitumor immunotherapy. In this paper, several nanobiotics commonly used in tumor immunotherapy at this stage are discussed, and they activate or enhance the body's immunity with their unique advantages. In conclusion, we reviewed recent advances in tumor immunotherapy based on nanomaterials, such as biological cell membrane modification, self-assembly, mesoporous, metal and hydrogels, to explore new directions and strategies for tumor immunotherapy.

Constructing Hypoxia-Tolerant and Host Tumor-Enriched Aggregation-Induced Emission Photosensitizer for Suppressing Malignant Tumors Relapse and Metastasis

Photodynamic immunotherapy is a promising treatment strategy that destroys primary tumors and inhibits the metastasis and relapse of distant tumors. As reactive oxygen species are an intermediary for triggering immune responses, photosensitizers (PSs) that can actively target and efficiently trigger oxidative stress are urgently required. Herein, pyrrolo[3,2-b]pyrrole as an electronic donor is introduced in acceptor-donor-acceptor skeleton PSs (TP-IS1 and TP-IS2) with aggregation-induced emission properties and high absorptivity. Meanwhile, pyrrolo[3,2-b]pyrrole derivatives innovatively prove their ability of type I photoreaction, indicating their promising hypoxia-tolerant advantages. Moreover, M1 macrophages depicting an ultrafast delivery through the cell-to-cell tunneling nanotube pathway emerge to construct TP-IS1@M1 by coating the photosensitizer TP-IS1. Under low concentration of TP-IS1@M1, an effective immune response of TP-IS1@M1 is demonstrated by releasing damage-associated molecular patterns, maturating dendritic cells, and vanishing the distant tumor. These findings reveal insights into developing hypoxia-tolerant PSs and an efficient delivery method with unprecedented performance against tumor metastasis.

Tumor Selective Metabolic Reprogramming as a Prospective PD-L1 Depression Strategy to Reactivate Immunotherapy

Currently, the role of the lysosome, endoplasmic reticulum, or dictyosome in the transcription and translation of programmed cell death ligand 1 (PD-L1) is well revealed, but the role and function of mitochondria in the PD-L1 expression in tumors is still not fully researched, making it hard to offer a novel PD-L1 regulation strategy. In this research, it is newly revealed that mitochondria oxidative phosphorylation (OXPHOS) depression can be used as an effective PD-L1 down-regulation method. To offer an ideal and high-effective tumor mitochondria-targeted OXPHOS depression nanosystem, IR-LND is prepared by conjugating mitochondria-targeted heptamethine cyanine dye IR-68 with mitochondrial complexes I and II depression agent lonidamine (LND), which then further self-assembled with albumin (Alb) to form IR-LND@Alb nanoparticles. By doing this, PD-L1 expression in tumors is selectively and effectively depressed by IR-LND@Alb nanoparticles. As expected, the anti-tumor efficacy of such a PD-L1 depression strategy is superior to conventional anti-PD-L1 monoclonal antibodies. Interestingly, IR-LND can also be served as a novel ideal promising photodynamic therapy (PDT) drug with self-oxygen and self-PD-L1 regulation capacity. All in all, this tumor-selective metabolic reprogramming platform to reactivate immunotherapy and sensitize for PDT effect, would open a new window for mitochondrial immunotherapy for cancer patients.

Molecular Tailoring Based on Forster Resonance Energy Transfer for Initiating Two-Photon Theranostics with Amplified Reactive Oxygen Species

The fabrication of multifunctional photosensitizers (PSs) with abundant Type I/II ROS for efficient theranostics in the "therapeutic window" (700-900 nm) is an appealing yet significantly challenging task. We herein report a molecular tailoring strategy based on intramolecular two-photon Forster Resonance Energy Transfer (TP-FRET) to obtain a novel theranostic agent (Lyso-FRET), featuring the amplified advantage of energy donor (NH) and acceptor (COOH), because of the reuse of fluorescence energy with high efficiency of FRET (∼83%). Importantly, under the excitation by the near-infrared (840 nm) window, Lyso-FRET can not only penetrate the deeper tissue with a higher resolution for fluorescence imaging due to the nonlinear optical (NLO) nature, but also generate more Type I (superoxide anion) and Type II (singlet oxygen) reactive oxygen species for hypoxic PDT. Moreover, Lyso-FRET targeting lysosomes further promotes the effect of treatment. The experiments in vitro and in vivo also verify that the developed TP-FRET PS is conducive to treating deep hypoxic tumors. This strategy provides new and significant insights into the design and fabrication of advanced multifunctional PSs.

Activation of pyroptosis by specific organelle-targeting photodynamic therapy to amplify immunogenic cell death for anti-tumor immunotherapy

Pyroptosis, a unique lytic programmed cell death, inspired tempting implications as potent anti-tumor strategy in pertinent to its potentials in stimulating anti-tumor immunity for eradication of primary tumors and metastasis. Nonetheless, rare therapeutics have been reported to successfully stimulate pyroptosis. In view of the intimate participation of reactive oxygen species (ROS) in stimulating pyroptosis, we attempted to devise a spectrum of well-defined subcellular organelle (including mitochondria, lysosomes and endoplasmic reticulum)-targeting photosensitizers with the aim of precisely localizing ROS (produced from photosensitizers) at the subcellular compartments and explore their potentials in urging pyroptosis and immunogenic cell death (ICD). The subsequent investigations revealed varied degrees of pyroptosis upon photodynamic therapy (PDT) towards cancerous cells, as supported by not only observation of the distinctive morphological and mechanistic characteristics of pyroptosis, but for the first-time explicit validation from comprehensive RNA-Seq analysis. Furthermore, in vivo anti-tumor PDT could exert eradication of the primary tumors, more importantly suppressed the distant tumor and metastatic tumor growth through an abscopal effect, approving the acquirement of specific anti-tumor immunity as a consequence of pyroptosis. Hence, pyroptosis was concluded unprecedently by our proposed organelles-targeting PDT strategy and explicitly delineated with molecular insights into its occurrence and the consequent ICD.

Chondroitin sulfate-based prodrug nanoparticles enhance photodynamic immunotherapy via Golgi apparatus targeting

Photodynamic therapy (PDT) is an emerging therapeutic approach that can inhibit tumor growth by destroying local tumors and activating systemic antitumor immune responses. However, PDT can be ineffective because of photosensitizer aggregation, tumor-induced dendritic cells (DC_S) dysfunction and PDT-mediated immunosuppression. Therefore, we designed chondroitin sulfate-based prodrug nanoparticles for the co-delivery of the photosensitizer chlorin e6 (Ce6) and retinoic acid (RA), which can reduce PDT-mediated immunosuppression by disrupting the Golgi apparatus and blocking the production of immunosuppressive cytokines. Moreover, CpG oligodeoxynucleotide was combined as immunoadjuvant to promote the maturation of DCs. As expected, the strategy of Golgi apparatus targeting immunotherapy combined PDT was confirmed to relieve PDT-induced immunosuppression, showed excellent PDT antitumor efficacy in B16F10-subcutaneous bearing mice model. Thus, our finding offers a promising approach for photodynamic immunotherapy of advanced cancers. STATEMENT OF SIGNIFICANCE: Golgi apparatus has been shown to be a potential target of immunosuppression for producing several immunosuppressive cytokines. In this work, a Golgi apparatus-targeted prodrug nanoparticle was developed to enhance the immune response in photodynamic immunotherapy. The nanoparticle can target and disrupt the Golgi apparatus in tumor cells, which reduced PDT-mediated immunosuppression by blocking the production of immunosuppressive cytokines. This work provides an effective strategy of PDT in combination with the Golgi apparatus-targeted nanovesicle for enhanced cancer therapy.

Albumin-mediated “Unlocking” of supramolecular prodrug-like nanozymes toward selective imaging-guided phototherapy

An adaptive nanozyme without producing off-target toxicity has been successfully applied in phototherapy.