Sequential Protein-Responsive Nanophotosensitizer Complex for Enhancing Tumor-Specific Therapy

Advancements in molecular disassembly of optical probes: a paradigm shift in sensing, bioimaging, and therapeutics

The majority of self-assembled fluorescent dyes suffer from aggregation-caused quenching (ACQ), which detrimentally affects their diagnostic and therapeutic effectiveness. While aggregation-induced emission (AIE) active dyes offer a promising solution to overcome this limitation, they may face significant challenges as the intracellular environment often prevents aggregation, leading to disassembly and posing challenges for AIE fluorogens. Recent progress in signal amplification through the disassembly of ACQ dyes has opened new avenues for creating ultrasensitive optical sensors and enhancing phototherapeutic outcomes. These advances are well-aligned with cutting-edge technologies such as single-molecule microscopy and targeted molecular therapies. This work explores the concept of disaggregation-induced emission (DIE), showcasing the revolutionary capabilities of DIE-based dyes from their design to their application in sensing, bioimaging, disease monitoring, and treatment in both cellular and animal models. Our objective is to provide an in-depth comparison of aggregation versus disaggregation mechanisms, aiming to stimulate further advancements in the design and utilization of ACQ fluorescent dyes through DIE technology. This initiative is poised to catalyze scientific progress across a broad spectrum of disciplines.

Telomerase-activated Au@DNA nanomachine for targeted chemo-photodynamic synergistic therapy

We successfully designed a smart activatable nanomachine for cancer synergistic therapy. Photodynamic therapy (PDT) and chemotherapy can be activated by intracellular telomerase while anti-cancer drugs can be effectively transported into tumour cells. An Sgc8 aptamer was designed, which can specifically distinguish tumour cells from normal cells and perform targeted therapy. The nanomachine entered the tumour cells by recognising PTK7, which is overexpressed on the surface of cancer cells. Then, the "switch" of the system was opened by TP sequence extension under telomerase stimulus. So, the chemotherapeutic drug DOX was released to achieve the chemotherapy, and the Ce6 labelled Sgc8-apt was released to activate the PDT. It was found that if no telomerase existed, the Ce6 would always be in an "off" state and could not activate the PDT. Telomerase is the key to controlling the activation of the PDT, which effectively reduces the damage photosensitisers cause to normal cells. Using in vitro and in vivo experiments, the nanomachine shows an excellent performance in targeted synergistic therapy, which is expected to be utilised in the future.

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.

Surface protein-retractive and redox-degradable mesoporous organosilica nanoparticles for enhanced cancer therapy

Targeted delivery along with controlled drug release is considered crucial in development of a drug delivery system (DDS) for efficient cancer treatment. In this paper, we present a strategy to obtain such a DDS by utilizing disulfide-incorporated mesoporous organosilica nanoparticles (MONs), which were engineered to minimize the surface interactions with proteins for better targeting and therapeutic performance. That is, after MONs were loaded with a chemodrug doxorubicin (DOX) through the inner pores, their outer surface was treated for conjugation to the glutathione-S-transferase (GST)-fused cell-specific affibody (Afb) (GST-Afb). These particles exhibited prompt responsivity to the SS bond-dissociating glutathione (GSH), which resulted in considerable degradation of the initial particle morphology and DOX release. As the protein adsorption to the MON surface appeared largely reduced, their targeting ability with GSH-stimulated therapeutic activities was demonstrated in vitro by employing two kinds of the GST-Afb protein, which target human cancer cells with the surface membrane receptor, HER2 or EGFR. Compared with unmodified control particles, the presented results show that our system can significantly enhance cancer-therapeutic outcomes of the loaded drug, offering a promising way of designing a more efficacious DDS.

Recent Advances in Hydrogel-Based Phototherapy for Tumor Treatment

Phototherapeutic agent-based phototherapies activated by light have proven to be safe modalities for the treatment of various malignant tumor indications. The two main modalities of phototherapies include photothermal therapy, which causes localized thermal damage to target lesions, and photodynamic therapy, which causes localized chemical damage by generated reactive oxygen species (ROS). Conventional phototherapies suffer a major shortcoming in their clinical application due to their phototoxicity, which primarily arises from the uncontrolled distribution of phototherapeutic agents in vivo. For successful antitumor phototherapy, it is essential to ensure the generation of heat or ROS specifically occurs at the tumor site. To minimize the reverse side effects of phototherapy while improving its therapeutic performance, extensive research has focused on developing hydrogel-based phototherapy for tumor treatment. The utilization of hydrogels as drug carriers allows for the sustained delivery of phototherapeutic agents to tumor sites, thereby limiting their adverse effects. Herein, we summarize the recent advancements in the design of hydrogels for antitumor phototherapy, offer a comprehensive overview of the latest advances in hydrogel-based phototherapy and its combination with other therapeutic modalities for tumor treatment, and discuss the current clinical status of hydrogel-based antitumor phototherapy.

pH-Responsive non-antibiotic polymer prodrugs eradicate intracellular infection by killing bacteria and regulating immune response

Intracellular bacterial infections pose enormous challenges to food safety and public health. Antibiotic-based polymer prodrugs have been used to treat intracellular bacterial infection. However, the overuse of antibiotics may lead to the emergence of antibiotic resistance. In this work, we aimed to develop antibiotic-free pH-responsive polymeric prodrugs to combat intracellular S. aureus infection. Amphiphilic poly(ethylene glycol)-b-poly[(3-phenylprop-2-ene-1,1-diyl)bis(oxy)bis(enthane-2,1- diyl)diacrylate] (PEG-b-PCAE) was obtained by radical polymerization and they could self-assemble to form micelles. PEG-b-PCAE micelles could uptake by macrophage. Upon exposure to the acidic phagolysosome, PEG-b-PCAE micelles could release cinnamaldehyde (CA) through hydrolysis of the acetal linkage. PEG-b-PCAE could kill intracellular bacteria by damaging the bacterial membrane. Furthermore, PEG-b-PCAE micelles could generate reactive oxygen species (ROS) in macrophages and subsequently activate immune system to clear bacteria by inducing macrophages differentiation to M1 phenotype. PEG-b-PCAE micelles could accelerate the wound healing process of the S. aureus-infected model in vivo. It is anticipated that multifunctional antibiotic-free PEG-b-PCAE micelles with intrinsic antibacterial activities hold promise for improved outcomes in intracellular S. aureus infections.

Nanomaterials-based photosensitizers and delivery systems for photodynamic cancer therapy

The increasing cancer morbidity and mortality requires the development of high-efficiency and low-toxicity anticancer approaches. In recent years, photodynamic therapy (PDT) has attracted much attention in cancer therapy due to its non-invasive features and low side effects. Photosensitizer (PS) is one of the key factors of PDT, and its successful delivery largely determines the outcome of PDT. Although a few PS molecules have been approved for clinical use, PDT is still limited by the low stability and poor tumor targeting capacity of PSs. Various nanomaterial systems have shown great potentials in improving PDT, such as metal nanoparticles, graphene-based nanomaterials, liposomes, ROS-sensitive nanocarriers and supramolecular nanomaterials. The small molecular PSs can be loaded in functional nanomaterials to enhance the PS stability and tumor targeted delivery, and some functionalized nanomaterials themselves can be directly used as PSs. Herein, we aim to provide a comprehensive understanding of PDT, and summarize the recent progress of nanomaterials-based PSs and delivery systems in anticancer PDT. In addition, the concerns of nanomaterials-based PDT including low tumor targeting capacity, limited light penetration, hypoxia and nonspecific protein corona formation are discussed. The possible solutions to these concerns are also discussed.

Simultaneous Imaging of Dual microRNAs in Cancer Cells through Catalytic Hairpin Assembly on a DNA Tetrahedron

Accurate detection and imaging of tumor-related microRNA (miRNA) in living cells hold great promise for early cancer diagnosis and prognosis. One of the challenges is to develop methods that enable the identification of multiple miRNAs simultaneously to further improve the detection accuracy. Herein, a simultaneous detection and imaging method of two miRNAs was established by using a programmable designed DNA tetrahedron nanostructure (DTN) probe that includes a nucleolin aptamer (AS1411), two miRNA capture strands, and two pairs of metastable catalytic hairpins at different vertexes. The DTN probe exhibited enhanced tumor cell recognition ability, excellent stability and biocompatibility, and fast miRNA recognition and reaction kinetics. It was found that the DTN probe could specifically enter tumor cells, in which the capture strand could hybridize with miRNAs and initiate the catalytic hairpin assembly (CHA) only when the overexpressed miR-21 and miR-155 existed simultaneously, resulting in a distinct fluorescence resonance energy transfer signal and demonstrating the feasibility of this method for tumor diagnosis.

Structurally defined tandem-responsive nanoassemblies composed of dipeptide-based photosensitive derivatives and hypoxia-activated camptothecin prodrugs against primary and metastatic breast tumors

Substantial progress in the use of chemo-photodynamic nano-drug delivery systems (nano-DDS) for the treatment of the malignant breast cancer has been achieved. The inability to customize precise nanostructures, however, has limited the therapeutic efficacy of the prepared nano-DDS to date. Here, we report a structurally defined tandem-responsive chemo-photosensitive co-nanoassembly to eliminate primary breast tumor and prevent lung metastasis. This both-in-one co-nanoassembly is prepared by assembling a biocompatible photosensitive derivative (pheophorbide-diphenylalanine peptide, PPA-DA) with a hypoxia-activated camptothecin (CPT) prodrug [(4-nitrophenyl) formate camptothecin, N-CPT]. According to computational simulations, the co-assembly nanostructure is not the classical core-shell type, but consists of many small microphase regions. Upon exposure to a 660 nm laser, PPA-DA induce high levels of ROS production to effectively achieve the apoptosis of normoxic cancer cells. Subsequently, the hypoxia-activated N-CPT and CPT spatially penetrate deep into the hypoxic region of the tumor and suppress hypoxia-induced tumor metastasis. Benefiting from the rational design of the chemo-photodynamic both-in-one nano-DDS, these nanomedicines exhibit a promising potential in the inhibition of difficult-to-treat breast tumor metastasis in patients with breast cancer.

Sequence-Activated Fluorescent Nanotheranostics for Real-Time Profiling Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC), as one of the most malignant tumors with dense desmoplastic stroma, forms a specific matrix barrier to hinder effective diagnosis and therapy. To date, a paramount challenge is in the search for intelligent nanotheranostics for such hypopermeable tumors, especially in breaking the PDAC-specific physical barrier. The unpredictable in vivo behaviors of nanotheranostics, that is, real-time tracking where, when, and how they cross the physical barriers and are taken up by tumor cells, are the major bottleneck. Herein, we elaborately design sequence-activated nanotheranostic TCM-U11&Cy@P with dual-channel near-infrared fluorescence outputs for monitoring in vivo behaviors in a sequential fashion. This nanotheranostic with a programmable targeting capability effectively breaks through the PDAC barriers. Ultimately, the released aggregation-induced emission (AIE) particle TCM-U11 directly interacts with PDAC cells and penetrates into the deep tissue. Impressively, this fluorescent nanotheranostic intraoperatively can map human clinical PDAC specimens with high resolution. We believe that this unique sequence-activated fluorescent strategy expands the repertoire of nanotheranostics in the treatment of hypopermeable tumors.

Mesoporous silica nanoparticle-supported nanocarriers with enhanced drug loading, encapsulation stability, and targeting efficiency

For efficient drug delivery, stable encapsulation of a large amount of anticancer drug is crucial, not to mention cell-specific delivery. Among many possible nanocarriers, mesoporous silica nanoparticles are versatile frameworks...

Phthalocyanine and Its Formulations: A Promising Photosensitizer for Cervical Cancer Phototherapy

Cervical cancer is one of the most common causes of cancer-related deaths in women worldwide. Despite advances in current therapies, women with advanced or recurrent disease present poor prognosis. Photodynamic therapy (PDT) has emerged as an effective therapeutic alternative to treat oncological diseases such as cervical cancer. Phthalocyanines (Pcs) are considered good photosensitizers (PS) for PDT, although most of them present high levels of aggregation and are lipophilic. Despite many investigations and encouraging results, Pcs have not been approved as PS for PDT of invasive cervical cancer yet. This review presents an overview on the pathophysiology of cervical cancer and summarizes the most recent developments on the physicochemical properties of Pcs and biological results obtained both in vitro in tumor-bearing mice and in clinical tests reported in the last five years. Current evidence indicates that Pcs have potential as pharmaceutical agents for anti-cervical cancer therapy. The authors firmly believe that Pc-based formulations could emerge as a privileged scaffold for the establishment of lead compounds for PDT against different types of cervical cancer.

Intelligent Pore Switch of Hollow Mesoporous Organosilica Nanoparticles for High Contrast Magnetic Resonance Imaging and Tumor-Specific Chemotherapy

Hollow mesoporous organosilica nanoparticles (HMONs) are widely considered as a promising drug nanocarrier, but the loaded drugs can easily leak from HMONs, resulting in the considerably decreased drug loading capacity and increased biosafety risk. This study reports the smart use of core/shell Fe₃O₄/Gd₂O₃ (FG) hybrid nanoparticles as a gatekeeper to block the pores of HMONs, which can yield an unreported large loading content (up to 20.4%) of DOX. The conjugation of RGD dimer (R2) onto the DOX-loaded HMON with FG capping (D@HMON@FG@R2) allowed for active tumor-targeted delivery. The aggregated FG in D@HMON@FG@R2 could darken the normal tissue surrounding the tumor due to the high r₂ value (253.7 mM^-1 s^-1) and high r₂/r₁ ratio (19.13), and the intratumorally released FG as a result of reducibility-triggered HMON degradation could brighten the tumor because of the high r₁ value (20.1 mM^-1 s^-1) and low r₂/r₁ ratio (7.01), which contributed to high contrast magnetic resonance imaging (MRI) for guiding highly efficient tumor-specific DOX release and chemotherapy.

Phototherapy of Brain Tumours Using a Fibre Optic Neurosystem

In this work, a new approach was tested to assess the cellular composition of tissues by time-resolved methods of fluorescence analysis of exogenous and endogenous fluorophores. First of all, the differences in fluorescence kinetics of endogenous fluorophores (coenzymes NADH and FAD) in tumour and immunocompetent cells were determined. After that, differences in fluorescence kinetics of photosensitizer 5 ALA-induced protoporphyrin IX were established due to its different metabolism in cells of different phenotypes. Kinetics of photoluminescence of NADH and FAD coenzymes as well as photosensitizer were studied by means of two different methods: time-resolved spectroscopy based on a streak-camera and fibre optic neuroscopy, which served to perform process monitoring and regular fluorescence diagnosis of the probed region. Time-resolved fluorescence microscopy (FLIM) was used as a control technique. Time-resolved spectroscopic fluorescence lifetime analysis was performed on sexually mature female rats induced with glioma C6 brain tumour under in vivo conditions; thus, under conditions where the immune system actively intervenes in the process of oncogenesis. In this regard, the aim of the study was to recognize the cellular composition of the brain tumour tissue, namely the ratio of cancer and immunocompetent cells and their mutual localization. Understanding the role of the immune system thus provides new ways and approaches for further diagnosis and therapy, making tumour-associated immune cells a prime target for modern therapies.

Human serum albumin-based doxorubicin prodrug nanoparticles with tumor pH-responsive aggregation-enhanced retention and reduced cardiotoxicity

Doxorubicin (DOX) is a widely-used anticancer drug, but its cardiotoxicity severely hampers its potency in chemotherapy. Herein, human serum albumin (HSA) is engaged as a biocompatible nanocarrier to load a pH-sensitive DOX prodrug, DMDOX, generating HSA-DMDOX nanoparticles via self-assembly driven by hydrophobic interactions. HSA-DMDOX disperses well in a physiological environment (∼40 nm) but aggregates in a tumor acidic microenvironment (pH 6.5, ∼140 nm) owing to the hydrophobicity increase of DMDOX by protonation of carboxylic groups. In vitro anticancer study showed that HSA-DMDOX exhibited enhanced cellular uptake by 4T1 cells and superior cytotoxicity in comparison to HSA-DOX nanoparticles. In vivo study suggested that HSA-DMDOX achieved long blood circulation, aggregation enhanced tumor retention, comparable antitumor efficacy and reduced cardiotoxicity relative to free DOX. Our work presents a facile and effective approach to delivering anthracyclines by HSA-based tumor pH-responsive nanoparticles with aggregation-enhanced tumor retention and reduced toxicity.

Self-Illuminated, Oxygen-Supplemented Photodynamic Therapy via a Multienzyme-Mimicking Nanoconjugate

Current photodynamic therapy (PDT) faces several intrinsic limitations, including insufficient oxygen supply and limited penetration of external light sources. Herein, we report a nanoconjugate, which, in response to the elevated hydrogen peroxide levels associated with tumor tissues, can supplement the oxygen needed for PDT and provide local self-illumination. Consisting of a MnFe₂O₄ core, a metal-organic framework shell loaded with the chemiluminescence reagent luminol, and a hyaluronic acid surface coating, the nanoconjugate is highly effective for suppressing cancer tissues in vivo via PDT in the absence of externally delivered light.

Advances in Nanomaterial-Mediated Photothermal Cancer Therapies: Toward Clinical Applications

Photothermal therapy (PTT) has attracted extensive research attention as a noninvasive and selective treatment strategy for numerous cancers. PTT functions via photothermal effects induced by converting light energy into heat on near-infrared laser irradiation. Despite the great advances in PTT for cancer treatment, the photothermal therapeutics using laser devise only or non-specific small molecule PTT agents has been limited because of its low photothermal conversion efficiency, concerns about the biosafety of the photothermal agents, their low tumor accumulation, and a heat resistance of specific types of cancer. Using nanomaterials as PTT agents themselves, or for delivery of PTT agents, offers improved therapeutic outcomes with fewer side effects through enhanced photothermal conversion efficiency, accumulation of the PTT agent in the tumor tissue, and, by extension, through combination with other therapies. Herein, we review PTT’s current clinical progress and present the future outlooks for clinical applications. To better understand clinical PTT applications, we describe nanomaterial-mediated photothermal effects and their mechanism of action in the tumor microenvironment. This review also summarizes recent studies of PTT alone or in combination with other therapies. Overall, innovative and strategically designed PTT platforms are promising next-generation noninvasive cancer treatments to move closer toward clinical applications.

Nucleolin-Targeted DNA Nanotube for Precise Cancer Therapy through Förster Resonance Energy Transfer-Indicated Telomerase Responsiveness

Precise drug delivery holds great promise in cancer treatment but still faces challenges in controllable drug release in tumor cells specifically. Herein, a nucleolin-targeted and telomerase-responsive DNA nanotube for drug release was developed. First, a DNA nanosheet with four capture strands on its surface was prepared, which could bind and load ricin A chain (RTA). The RTA-loaded nanosheet was further converted into a DNA nanotube with a high Förster resonance energy transfer (FRET) efficiency in the presence of a Cy3-modified DNA fastener by hybridizing with the Cy5-modified DNA and another DNA-containing telomerase primer sequence along the long sides. Moreover, the aptamer of nucleolin was assembled on the DNA nanotube by combining with the hybrid chain at the terminal. The aptamer-functionalized and RTA-loaded DNA nanotube displayed enhanced tumor permeability and precise drug release in response to the telomerase in tumor cells, following the change of the FRET signal and RTA-induced cell death. Moreover, the DNA nanotube was applied successfully in vivo, and there was an obvious inhibition of tumor growth on xenograft-bearing mice following systemic administration, indicating that the constructed DNA nanotube represents a promising platform for precise RTA delivery in target cancer therapy.

A phthalocyanine-based self-assembled nanophotosensitizer for efficient in vivo photodynamic anticancer therapy

To develop highly efficient photosensitizers for photodynamic therapy, herein a zinc(II) phthalocyanine-folate conjugate (PcN-FA) used to construct an activatable nanophotosensitizer (NanoPcN-FA) through a facile self-assembly. The self-assembled nanophotosensitizer (NanoPcN) without folate-modification was used as a negative control. After self-assembly, the photoactivities of NanoPcN-FA was quenched. The in vitro studies showed that NanoPcN-FA could be taken in by folate-receptor (FR)-positive SKOV3 cells and activated in the cells. It also exhibited slightly higher photocytotoxicity against SKOV3 cells than NanoPcN. Moreover, the competitive assay confirmed that the cellular uptake of NanoPcN-FA was through a FR-mediated process. Finally, the in vivo results indicated that NanoPcN-FA could target tumor tissue of S180 rat ascitic tumor-bearing mice due to the folic acid (FA) ligand, leading to a highly efficient antitumor photodynamic efficacy with the tumor inhibition rate of 95%.

Recent Advances in Photodynamic Therapy for Deep-Seated Tumors with the Aid of Nanomedicine

Photodynamic therapy (PDT) works through photoactivation of a specific photosensitizer (PS) in a tumor in the presence of oxygen. PDT is widely applied in oncology to treat various cancers as it has a minimally invasive procedure and high selectivity, does not interfere with other treatments, and can be repeated as needed. A large amount of reactive oxygen species (ROS) and singlet oxygen is generated in a cancer cell during PDT, which destroys the tumor effectively. However, the efficacy of PDT in treating a deep-seated tumor is limited due to three main reasons: Limited light penetration depth, low oxygen concentration in the hypoxic core, and poor PS accumulation inside a tumor. Thus, PDT treatments are only approved for superficial and thin tumors. With the advancement of nanotechnology, PDT to treat deep-seated or thick tumors is becoming a reachable goal. In this review, we provide an update on the strategies for improving PDT with nanomedicine using different sophisticated-design nanoparticles, including two-photon excitation, X-ray activation, targeting tumor cells with surface modification, alteration of tumor cell metabolism pathways, release of therapeutic gases, improvement of tumor hypoxia, and stimulation of host immunity. We focus on the difficult-to-treat pancreatic cancer as a model to demonstrate the influence of advanced nanomedicine in PDT. A bright future of PDT application in the treatment of deep-seated tumors is expected.

Mesoporous Silica Nanoparticles as Carriers for Biomolecules in Cancer Therapy

Mesoporous silica nanoparticles (MSNs) offer many advantageous properties for applications in the field of nanobiotechnology. Loading of small molecules into MSNs is straightforward and widely applied, but with the upswing of both research and commercial interest in biological drugs in recent years, also biomacromolecules have been loaded into MSNs for delivery purposes. MSNs possess many critical properties making them a promising and versatile carrier for biomacromolecular delivery. In this chapter, we review the effects of the various structural parameters of MSNs on the effective loading of biomacromolecular therapeutics, with focus on maintaining stability and drug delivery performance. We also emphasize recent studies involving the use of MSNs in the delivery of biomacromolecular drugs, especially for cancer treatment.

A minireview on multiparameter-activated nanodevices for cancer imaging and therapy

Tumor microenvironment (TME)-responsive nanodevices are essential tools for cancer imaging and therapy. Exploiting the advantages of molecular engineering, nanodevices are emerging for biomedical applications. In order to reach targeted cancer areas, activated nanodevices first respond to the TME and then serve as an actuator for sensing, imaging and therapy. Most nanodevices depend on a single parameter as an input for their downstream activation, potentially leading to inaccurate diagnostic results and poor therapeutic outcomes. However, in the TME, some biomarkers are cross-linked, and such correlated biomarkers are potentially useful for cancer imaging and theranostic applications. Based on this phenomenon, researchers have developed approaches for the construction of multiparameter-activated nanodevices (MANs) to improve accuracy. This minireview summarizes the recent advances in the development of MANs for cancer imaging including fluorescence imaging, photoacoustic (PA) imaging, magnetic resonance imaging (MRI) and computed tomography (CT) imaging, as well as cancer therapy including radiotherapy, chemotherapy, photoinduced therapy and immunotherapy. We highlight different approaches for improving the specificity and precision of cancer imaging and therapy. In the future, MANs will show promise for clinical work in multimodal diagnosis and therapeutics.

Inhibiting Radiative Transition-Mediated Multifunctional Polymeric Nanoplatforms for Highly Efficient Tumor Phototherapeutics

It is highly desired to explore ideal phototherapeutic nanoplatforms, especially containing satisfactory phototherapeutic agents (PTAs), for potential cancer therapies. Herein, we proposed an effective strategy for designing a highly efficient PTA through inhibiting radiative transition (IRT). Specifically, we developed an ultralow radiative BODIPY derivative (TPA-IBDP) by simply conjugating two triphenylamine units to iodine-substituted BODIPY, which could simultaneously facilitate the nonradiative decay channels of singlet-to-triplet intersystem crossing and intramolecular charge transfer. In comparison to the normal BODIPY compound, TPA-IBDP exhibited an outstanding singlet oxygen yield (31.8-fold) and a higher photothermal conversion efficiency (PCE; over 3-fold), respectively, benefiting from the extended π-conjugated donor-to-accepter (D-A) structure and the heavy atom effect. For tumor phototherapy using TPA-IBDP, TPA-IBDP was conjugated with a H₂O₂-responsive amphiphilic copolymer POEGMA₁₀-b-[PBMA₅-co-(PS-N₃)₂] to construct a multifunctional phototherapeutic BODIPY-based nanoplatform (PB). PB produced abundant singlet oxygen (¹O₂) and heat along with negligible fluorescence emission under near-infrared laser irradiation. Additionally, PB could generate a GSH-depletion scavenger (quinone methide, QM) after reacting with the abundant intracellular H₂O₂ in tumor for the cooperative enhancement of IRT-mediated phototherapy. We envision that this highly efficient multifunctional phototherapeutic nanoplatform cooperated by GSH-depletion could be a valuable paradigm for tumor treatments.

In Vivo-assembled phthalocyanine/albumin supramolecular complexes combined with a hypoxia-activated prodrug for enhanced photodynamic immunotherapy of cancer

Immunogenic photodynamic therapy (PDT) has the potential to moderate the shortfalls of cancer immunotherapy. However, its efficacy is severely limited particularly because of the lack of optimal photosensitizers and smart delivery processes and the inherent shortcomings of PDT (e.g., hypoxia resistance). Here, we demonstrate a clinically promising approach that utilizes a water-soluble phthalocyanine derivative (PcN4) concomitantly delivered with a hypoxia-activated prodrug (AQ4N) to amplify the effect of PDT and enhance cancer immunotherapy. After intravenous injection, PcN4 selectively interacted with endogenous albumin dimers and formed supramolecular complexes, providing a facile and green approach for tumor-targeted PDT. The concomitant delivery of AQ4N overcame the limitations of hypoxia in PDT and improved the antitumor activity of PDT. Treatment with PcN4-mediated and AQ4N-amplified PDT almost completely eradicated sizable primary tumors in a triple-negative breast cancer model and significantly activated CD8⁺ T cells. As the majority of tumor infiltrating CD8⁺ T cells were both PD-1- and TIM3-positive, additional combination therapy using PD-L1/PD-1 pathway blockade was warranted. After combination with immune checkpoint blockade treatment, an enhanced abscopal effect was achieved in both distant and metastatic tumors.

Molecular Design of Highly Efficient Heavy-Atom-Free Triplet BODIPY Derivatives for Photodynamic Therapy and Bioimaging

Novel BODIPY photosensitizers were developed for imaging-guided photodynamic therapy. The introduction of a strong electron donor to the BODIPY core through a phenyl linker combined with the twisted arrangement between the donor and the BODIPY acceptor is essential for reducing the energy gap between the lowest singlet excited state and the lowest triplet state (ΔE_ST ), leading to a significant enhancement in the intersystem crossing (ISC) of the BODIPYs. Remarkably, the BDP-5 with the smallest ΔE_ST (ca. 0.44 eV) exhibited excellent singlet oxygen generation capabilities in both organic and aqueous solutions. BDP-5 also displayed bright emission in the far-red/near-infrared region in the condensed states. More importantly, both in vitro and in vivo studies demonstrated that BDP-5 NPs displayed a high potential for photodynamic cancer therapy and bioimaging.

Supramolecular Phthalocyanine Assemblies for Improved Photoacoustic Imaging and Photothermal Therapy

Phototheranostic nanoplatforms are of particular interest for cancer diagnosis and imaging-guided therapy. Herein, we develop a supramolecular approach to fabricate a nanostructured phototheranostic agent through the direct self-assembly of two water-soluble phthalocyanine derivatives, PcS4 and PcN4. The nature of the molecular recognition between PcS4 and PcN4 facilitates the formation of nanostructure (PcS4-PcN4) and consequently enables the fabrication of PcS4-PcN4 with completely quenched fluorescence and reduced singlet oxygen generation, leading to the high photoacoustic and photothermal activity of PcS4-PcN4. In vivo evaluations suggest that PcS4-PcN4 could not only efficiently visualize a tumor with high contrast through whole-body photoacoustic imaging but also enable excellent photothermal therapy for cancer.

Advances in nanomaterials for photodynamic therapy applications: Status and challenges

Photodynamic therapy (PDT), as a non-invasive therapeutic modality that is alternative to radiotherapy and chemotherapy, is extensively investigated for cancer treatments. Although conventional organic photosensitizers (PSs) are still widely used and have achieved great progresses in PDT, the disadvantages such as hydrophobicity, poor stability within PDT environment and low cell/tissue specificity largely limit their clinical applications. Consequently, nano-agents with promising physicochemical and optical properties have emerged as an attractive alternative to overcome these drawbacks of traditional PSs. Herein, the up-to-date advances in the fabrication and fascinating applications of various nanomaterials in PDT have been summarized, including various types of nanoparticles, carbon-based nanomaterials, and two-dimensional nanomaterials, etc. In addition, the current challenges for the clinical use of PDT, and the corresponding strategies to address these issues, as well as future perspectives on further improvement of PDT have also been discussed.

GSH-Activatable NIR Nanoplatform with Mitochondria Targeting for Enhancing Tumor-Specific Therapy

Developing smart photosensitizers that are sensitive to tumor-specific signals for minimal side effects and enhanced antitumor efficacy is a tremendous challenge for tumor phototherapies. Herein, we construct a nanoplatform with glutathione (GSH)-activatable and mitochondria-targeted pro-photosensitizer encapsulated by ultrasensitive pH-responsive polymer for achieving imaging-guided tumor-specific photodynamic therapy (PDT). The GSH-activatable pro-photosensitizer, di-cyanine (DCy7), has been synthesized where two cyanine moieties are covalently conjugated by a disulfide bond, and the hydrophobic DCy7 is further encapsulated with an amphiphilic pH-responsive diblock copolymer POEGMA-b-PDPA to form P@DCy7 nanoparticles. Upon endocytosis by cancer cells, P@DCy7 nanoparticles dissociate at endosome first and then DCy7 is released to cytoplasm and subsequently activated by the high concentration of GSH, finally targets mitochondria for organelle-targeted PDT. Moreover, intracellular antioxidant GSH is consumed during the activation procedure that is beneficial to efficient PDT. These P@DCy7 nanoparticles display selective phototoxicity against tumor cells (HepG2 or 4T1 cells) over normal cells (BEAS-2B cells) in vitro, and their GSH-activatable enhanced PDT efficacy is further confirmed in tumor-bearing mice. Thus, P@DCy7 nanoparticles allow for accurate and highly efficient PDT with minimal side effects, providing an attractive nanoplatform for organelle-targeted precise PDT.