Self-Assembled Oxaliplatin(IV) Prodrug-Porphyrin Conjugate for Combinational Photodynamic Therapy and Chemotherapy

Application of near-infrared-activated and ATP-responsive trifunctional upconversion nano-jelly for in vivo tumor imaging and synergistic therapy

Upconversion nanoparticles (UCNPs)-mediated in-situ imaging and synergistic therapy may be an effective approach against tumors. However, it remains a challenge to improve therapeutic index and reduce toxicity. Here, we investigated the construction process of a three-layer (core-shell-shell) upconversion nano-jelly hydrogels (UCNJs) coated with stimulus-responsive deoxyribonucleic acid chains, aiming to achieve selective recognition of tumor cells and controlled release of drugs. The UCNJs have a NaYF4: Yb, Er core with an outer silica shell with embedded methylene blue (MB). Then the outer layer was coated with mesoporous silica and loaded with doxorubicin (DOX). Finally, polyacrylamide chains containing anti-adenosine triphosphate (ATP) aptamer sequences were assembled layer-by-layer on the surface of particles to form DNA hydrogels to lock DOX. Under near-infrared irradiation, green light (540 nm) emitted by UCNJs can be used for imaging, while red light (660 nm) is absorbed by MB. The latter generates singlet oxygen, resulting in photodynamic therapy (PDT) effect to inhibit tumor growth. UCNJs also can recognize ATP in tumor cells, leading to hydrogel degradation and DOX release. The hydrogel coating can increase drug-carrying capacity of mesoporous materials and improve biocompatibility. Therefore, the UCNJs has great potential advantages for application in the field of cancer diagnosis and treatment.

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.

Dynamically assembled nanomedicine based on host-guest molecular recognition for NIR laser-excited chemotherapy and phototheranostics

Nanomedicines combining multimodal therapeutic modalities supply opportunities to eliminate tumors in a safe and efficient manner. However, the rigid encapsulation and covalent conjugation of different therapeutic reagents suffer from the complicated preparation process, premature drug leakage and severe adverse events. Herein, we report a self-enhanced supramolecular nanomedicine (SND) based on the host-guest molecular recognition between β-cyclodextrin (β-CD) and camptothecin (CPT) for trimodal synergistic chemotherapy, photodynamic therapy (PDT) and photothermal therapy (PTT) using a single 670 nm near-infrared (NIR) laser. Thioketal bond and polyethylene glycol (PEG) segment are introduced into the structure of CPT-tk-PEG prodrug, thus the premature release of CPT is efficiently inhibited and the specific drug release is realized at tumor site where singlet oxygen (1O2)-generated PDT is performed. A boron dipyrromethene (BODIPY) theranostic agent is anchored onto β-CD, endowing SND with capabilities of fluorescence imaging, PDT and PTT. Benefiting from the supramolecular assembly, not only the solubility of CPT is improved by 40 times, but also the blood circulation time and tumor accumulation of SND are greatly promoted. In vivo, SND can effectively induce the immunogenic cell death (ICD) of tumor cells, thus performing prominent inhibition against both primary and distal tumors, and even anti-metastasis effect against liver without causing obvious systemic toxicity. STATEMENT OF SIGNIFICANCE: Although nanomedicines supply opportunities to eliminate tumors in an efficient manner, they usually suffer from premature drug leakage, complicated preparation process and severe side effects owing to the rigid encapsulation or covalent conjugation. Based on the host-guest molecular recognition, we developed a self-enhanced SND for synergistic chemotherapy, photodynamic therapy and photothermal therapy. Introduction of thioketal bond in CPT prodrug avoided the premature drug release, and the specific drug release was realized in the tumor cells. Profiting from the facile supramolecular assembly strategy, SND not only displayed a primary anticancer efficacy with a low systemic toxicity, but also efficiently inhibited the growth of distal tumors, contributing a vaccine-like function to eradicate the recurrent and metastatic tumors.

Emerging platinum(IV) prodrug nanotherapeutics: A new epoch for platinum-based cancer therapy

Owing to the unique DNA damaging cytotoxicity, platinum (Pt)-based chemotherapy has long been the first-line choice for clinical oncology. Unfortunately, Pt drugs are restricted by the severe dose-dependent toxicity and drug resistance. Correspondingly, Pt(IV) prodrugs are developed with the aim to improve the antitumor performance of Pt drugs. However, as "free" molecules, Pt(IV) prodrugs are still subject to unsatisfactory in vivo destiny and antitumor efficacy. Recently, Pt(IV) prodrug nanotherapeutics, inheriting both the merits of Pt(IV) prodrugs and nanotherapeutics, have emerged and demonstrated the promise to address the underexploited dilemma of Pt-based cancer therapy. Herein, we summarize the latest fronts of emerging Pt(IV) prodrug nanotherapeutics. First, the basic outlines of Pt(IV) prodrug nanotherapeutics are overviewed. Afterwards, how versatile Pt(IV) prodrug nanotherapeutics overcome the multiple biological barriers of antitumor drug delivery is introduced in detail. Moreover, advanced combination therapies based on multimodal Pt(IV) prodrug nanotherapeutics are discussed with special emphasis on the synergistic mechanisms. Finally, prospects and challenges of Pt(IV) prodrug nanotherapeutics for future clinical translation are spotlighted.

Adamantoid Scaffolds for Multiple Cargo Loading and Cellular Delivery as β-Cyclodextrin Inclusion Complexes

There is huge demand for developing guests that bind β-CD and can conjugate multiple cargos for cellular delivery. We synthesized trioxaadamantane derivatives, which can conjugate up to three cargos per guest. 1 H NMR titration and isothermal titration calorimetry revealed these guests form 1 : 1 inclusion complexes with β-CD with association constants in the order of 103  M-1 . Co-crystallization of β-CD with guests yielded crystals of their 1 : 1 inclusion complexes as determined by single-crystal X-ray diffraction. In all cases, trioxaadamantane core is buried within the hydrophobic cavity of β-CD and three hydroxyl groups are exposed outside. We established biocompatibility using representative candidate G4 and its inclusion complex with β-CD (β-CD⊂G4), by MTT assay using HeLa cells. We incubated HeLa cells with rhodamine-conjugated G4 and established cellular cargo delivery using confocal laser scanning microscopy (CLSM) and fluorescence-activated cell sorting (FACS) analysis. For functional assay, we incubated HeLa cells with β-CD-inclusion complexes of G4-derived prodrugs G6 and G7, containing one and three units of the antitumor drug (S)-(+)-camptothecin, respectively. Cells incubated with β-CD⊂G7 displayed the highest internalization and uniform distribution of camptothecin. β-CD⊂G7 showed higher cytotoxicity than G7, camptothecin, G6 and β-CD⊂G6, affirming the efficiency of adamantoid derivatives in high-density loading and cargo delivery.

NIR-II light evokes DNA cross-linking for chemotherapy and immunogenic cell death

As a DNA damaging agent, oxaliplatin (OXA) can induce immunogenic cell death (ICD) in tumors to activate the immune system. However, the DNA damage induced by OXA is limited and the ICD effect is not strong enough to enhance anti-tumor efficacy. Here, we propose a strategy to maximize the ICD effect of OXA through the mild hyperthermia generated by nanoparticles with a platinum (IV) prodrug of OXA (Pt(IV)-C16) and a near-infrared-II (NIR-II) photothermal agent IR1061 upon the irradiation of NIR-II light. The mild hyperthermia (43 °C) holds advantages in two aspects: 1) increase the Pt-DNA cross-linking, leading to enhanced DNA damage and apoptosis; 2) induce stronger ICD effects for cancer immunotherapy. We demonstrated that, compared with OXA and photothermal therapy of IR1061 alone, these nanoparticles under NIR-II light irradiation can significantly improve the anti-cancer efficacy against triple-negative breast cancer 4T1 tumor. This new strategy provides an effective way to improve the therapeutic outcome of OXA. STATEMENT OF SIGNIFICANCE: OXA could induce immunogenic cell death (ICD) via stimulating immune responses by increasing tumor cell stress and death, which triggers tumor-specific immune responses to achieve immunotherapy. However, due to the insufficient Pt-DNA crosslinks, the ICD effect triggered by OXA cannot induce robust immune response. Mild hyperthermia has great potential to maximize the therapeutic outcome of oxaliplatin by increasing the Pt-DNA cross-linking to augment the immunoresponse for enhanced cancer immunotherapy.

Red light active Pt(iv)-BODIPY prodrug as a mitochondria and endoplasmic reticulum targeted chemo-PDT agent

A cisplatin-based platinum(iv) prodrug, [Pt(NH3)2Cl2(OH)(L 1 )], having L 1 as a red-light active boron-dipyrromethene (BODIPY) pendant, was synthesized and characterized and its application as a chemo-cum-photodynamic therapy agent was studied. Me-L 1 as the ligand precursor is structurally characterized. The complex displayed an intense absorption band near 650 nm (ε ∼ 8.8 × 104 dm3 mol-1 cm-1) in 1 : 1 (v/v) DMSO/DPBS. It showed an emission band at 674 nm (λ ex = 630 nm) with a fluorescence quantum yield (Φ F) value of 0.37. In red light (600-720 nm), it generated singlet oxygen as evidenced from the 1,3-diphenylisobenzofuran (DPBF) titration experiment giving a singlet oxygen quantum yield (Φ Δ) value of 0.28 in DMSO. The mechanistic pUC19 DNA photocleavage study and singlet oxygen sensor green (SOSG) assay ascertained its ability to generate singlet oxygen in both extracellular and intracellular media by a type-II photo-process. The complex exhibited high stability in the dark, but on red-light irradiation, it displayed rapid activation in the presence of a reducing environment. It displayed remarkable apoptotic photocytotoxicity with half-maximal inhibitory concentration (IC50) ranging from 0.58 to 0.76 μM in human cervical cancer (HeLa) and breast cancer (MCF-7) cells with a respective photo-cytotoxicity index value of >172 and >131. The photodynamic activity was significantly less in non-cancerous human peripheral lung epithelial (HPL1D) cells. The emissive complex showed localization in the mitochondria and endoplasmic reticulum (ER) with a similar Pearson's correlation coefficient value, making it a dual organelle-targeted therapeutic agent. JC-1, fluo-4-AM and annexin V-FITC/propidium iodide assays in HeLa cells showed cellular apoptosis by arresting cells in the sub-G1 phase via mitochondrial dysfunction and ER stress.

Supramolecular Combination Cancer Therapy Based on Macrocyclic Supramolecular Materials

Supramolecular combination therapy adopts supramolecular materials to design intelligent drug delivery systems with different strategies for cancer treatments. Thereinto, macrocyclic supramolecular materials play a crucial role in encapsulating anticancer drugs to improve anticancer efficiency and decrease toxicity towards normal tissue by host-guest interaction. In general, chemotherapy is still common therapy for solid tumors in clinics. However, supramolecular combination therapy can overcome the limitations of the traditional single-drug chemotherapy in the laboratory findings. In this review, we summarized the combination chemotherapy, photothermal chemotherapy, and gene chemotherapy based on macrocyclic supramolecular materials. Finally, the application prospects in supramolecular combination therapy are discussed.

Porphyrin-Based Nanoparticles: A Promising Phototherapy Platform

Phototherapy, including photodynamic therapy and photothermal therapy, is an emerging form of non-invasive treatment. The combination of imaging technology and phototherapy is becoming an attractive development in the treatment of cancer, as it allows for highly effective therapeutic results through image-guided phototherapy. Porphyrins have attracted significant interest in the treatment and diagnosis of cancer due to their excellent phototherapeutic effects in phototherapy and their remarkable imaging capabilities in fluorescence imaging, magnetic resonance imaging and photoacoustic imaging. However, porphyrins suffer from poor water solubility, low near-infrared absorption and insufficient tumor accumulation. The development of nanotechnology provides an effective way to improve the bioavailability, phototherapeutic effect and imaging capability of porphyrins. This review highlights the research results of porphyrin-based small molecule nanoparticles in phototherapy and image-guided phototherapy in the last decade and discusses the challenges and directions for the development of porphyrin-based small molecule nanoparticles in phototherapy.

A phenolic based tumor-permeated nano-framework for immunogenic cell death induction combined with PD-L1 immune checkpoint blockade

A critical obstacle for programmed death ligand 1 (PD-L1) immune checkpoint blockade immunotherapy is the insufficient T cell infiltration and low immunogenicity of tumor cells. Improving tumor immunogenicity through immunogenic cell death (ICD) can make tumor sensitive to PD-L1 checkpoint blockade immunotherapy. Herein, a phenolic based tumor-permeated nano-framework (EGPt-NF) was fabricated by cross-linking phenylboric acid modified platinum nanoparticles (PBA-Pt, ICD inducer) and epigallocatechin-3-O-gallate (EGCG, PD-L1 inhibitor) via pH-reversible borate ester. In particular, PBA-Pt could not only induce ICD cascade but also relieve tumor hypoxia. Consequently, EGPt-NF could effectively promote dendritic cell maturation and downregulate PD-L1 expression in tumor cells. Furthermore, EGPt-NF could also relieve tumor hypoxia to facilitate cytotoxic T lymphocyte infiltration and IFN-γ secretion. The synergistic effect of EGPt-NF could effectively improve tumor immunogenicity and amplify the therapeutic outcomes of cancer immunotherapy, resulting in a strong antitumor immune response in primary tumor and metastasis inhibition. Our simple approach expands the application of platinum-based drug delivery systems for cancer immunotherapy.

Cyclodextrin-Based Nanoplatforms for Tumor Phototherapy: An Update

Tumor phototherapies are light-mediated tumor treatment modalities, which usually refer to tumor photothermal therapy (PTT) and photodynamic therapy (PDT). Due to the outstanding spatial-temporal control over treatment through light irradiation, tumor phototherapies display extremely low side effects during treatment and are believed to be a tumor treatment method with a clinical translation potential. However, current tumor phototherapy nanoplatforms face obstacles, including light irradiation-induced skin burning, tumor hypoxia microenvironments, limited light penetration depth, et al. Therefore, one important research direction is developing a tumor phototherapy nanoplatform with multifunctionality and enhanced pharmacological effects to overcome the complexity of tumor treatment. On the other hand, cyclodextrins (CDs) are starch-originated circular oligosaccharides with negligible toxicity and have been used to form supermolecular nanostructures through a host–guest interaction between the inner cavity of CDs and functional biomolecules. In the past few years, numerous studies have focused on CD-based multifunctional tumor phototherapy nanoplatforms with an enhanced photoeffect, responsive morphological transformation, and elevated drug bioavailability. This review focuses on the preparation methods of CD-based tumor phototherapy nanoplatforms and their unique physiochemical properties for improving anti-tumor pharmacological efficacy.

A porphyrin-based metallacage for enhanced photodynamic therapy

In this study, we designed an effective nanoplatform to improve the photodynamic therapy (PDT) of porphyrins. Combining a porphyrin-based metallacage (PM), hyaluronidase (HAase) and DSPE-mPEG2000 together, the nanoparticle (PM@HAase-mPEG) showed enhanced PDT efficacy. The PM improved the stability of the porphyrin, avoided its aggregation and provided cavities to concentrate oxygen molecules, which was beneficial for enhancing PDT. HAase degraded HA to increase the intracellular accumulation of nanoparticles, normalized blood vessels and relieved hypoxia in tumors. PM@HAase-mPEG inhibited the growth of tumors in a 4T1 mouse model by the generated singlet oxygen with excellent PDT efficacy. This study resolved the problems of the instability of PSs, less cellular accumulation of drugs, and tumor hypoxia that limited the anti-tumor application of PDT.

Ruthenium photosensitizer anchored gold nanorods for synergistic photodynamic and photothermal therapy

Ruthenium polypyridyl complexes have been widely used as bioprobes and photosensitizers. However, several disadvantages including slow cellular uptake, nonspecific binding with biomolecules and toxicity limit their applications. In this study, a nanocarrier of human serum albumin coated gold nanorods was developed to deliver a ruthenium photosensitizer for PDT/PTT combination therapy. The HSA coating endowed the nanodrug with high biocompatibility and stability under physiological conditions. Ru-GNR-HSANPs generate ¹O₂ and hydroxyl radicals to kill cancer cells under blue light irradiation, and exhibit excellent photothermal anticancer effects under 808 nm light irradiation. Significant synergistic anticancer effects were achieved by combined PDT/PTT therapy. Importantly, Ru-GNR-HSANPs can have the synergistic PDT/PTT functions with no need of drug release from the carrier.

Albumin-Based Therapeutics Capable of Glutathione Consumption and Hydrogen Peroxide Generation for Synergetic Chemodynamic and Chemotherapy of Cancer

A nanoscale therapeutic system with good biocompatibility was facilely fabricated by the coassembly of human serum albumin and glucose oxidase (GOD), where the former was pretreated with metal ions through a chelating agent or the chemotherapeutic prodrug oxaliplatin (Oxa(IV)). Among different chelating metal ions used, Mn²⁺ ion was selected to produce hydroxyl radical (•OH) efficiently through Fenton-like reaction, while GOD loaded in the system was able to generate a large amount of hydrogen peroxide for promoting efficient conversion into highly toxic •OH. In the meanwhile, the conversion of the Oxa(IV) prodrug into chemotherapeutic Oxa(II) was beneficial for the consumption of glutathione, thereby enhancing the chemodynamic therapy (CDT) efficacy. Based on the combined chemotherapy and CDT, the treatment with this system leads to superior antitumor outcome.

Synergic Antitumor Effect of Photodynamic Therapy and Chemotherapy Mediated by Nano Drug Delivery Systems

This review provides a summary of recent progress in the development of different nano-platforms for the efficient synergistic effect between photodynamic therapy and chemotherapy. In particular, this review focuses on various methods in which photosensitizers and chemotherapeutic agents are co-delivered to the targeted tumor site. In many cases, the photosensitizers act as drug carriers, but this review, also covers different types of appropriate nanocarriers that aid in the delivery of photosensitizers to the tumor site. These nanocarriers include transition metal, silica and graphene-based materials, liposomes, dendrimers, polymers, metal–organic frameworks, nano emulsions, and biologically derived nanocarriers. Many studies have demonstrated various benefits from using these nanocarriers including enhanced water solubility, stability, longer circulation times, and higher accumulation of therapeutic agents/photosensitizers at tumor sites. This review also describes novel approaches from different research groups that utilize various targeting strategies to increase treatment efficacy through simultaneous photodynamic therapy and chemotherapy.

Supramolecular Polymeric Prodrug Micelles for Efficient Anticancer Drug Delivery

Polymeric prodrugs have attracted great interest in the field of antitumor drug delivery owing to its integrated advantages of prodrugs and nanoparticles. However, the ambiguous chemical composition of polymeric prodrugs...

Self-assembled semiconducting polymer based hybrid nanoagents for synergistic tumor treatment

There is an impending need for the development of carrier-free nanosystems for single laser triggered activation of phototherapy, as such approach can overcome the drawbacks associated with irradiation by two distinct laser sources for avoiding prolonged treatment time and complex treatment protocols. Herein, we developed a self-assembled nanosystem (SCP-CS) consisting of a new semiconducting polymer (SCP) and encapsulated ultrasmall CuS (CS) nanoparticles. The SCP component displays remarkable near infrared (NIR) induced photothermal ability, enhanced reactive oxygen species (ROS) generation, and incredible photoacoustic (PA) signals upon activation by 808 nm laser for phototherapy mediated cancer ablation. The CuS component improves the PA imaging ability of SCP-CS, and also enhances photo-induced chemodynamic efficacy. Attributed to promoted single laser-triggered hyperthermia and enhanced ROS generation, the SCP-CS nanosystem shows effective intracellular uptake and intratumoral accumulation, enhanced tumor suppression with reduced treatment time, and devoid of any noticeable toxicity.

Metal-Coordinated Supramolecular Self-Assemblies for Cancer Theranostics

Metal-coordinated supramolecular nanoassemblies have recently attracted extensive attention as materials for cancer theranostics. Owing to their unique physicochemical properties, metal-coordinated supramolecular self-assemblies can bridge the boundary between traditional inorganic and organic materials. By tailoring the structural components of the metal ions and binding ligands, numerous multifunctional theranostic nanomedicines can be constructed. Metal-coordinated supramolecular nanoassemblies can modulate the tumor microenvironment (TME), thus facilitating the development of TME-responsive nanomedicines. More importantly, TME-responsive organic-inorganic hybrid nanomaterials can be constructed in vivo by exploiting the metal-coordinated self-assembly of a variety of functional ligands, which is a promising strategy for enhancing the tumor accumulation of theranostic molecules. In this review, recent advancements in the design and fabrication of metal-coordinated supramolecular nanomedicines for cancer theranostics are highlighted. These supramolecular compounds are classified according to the order in which the coordinated metal ions appear in the periodic table. Furthermore, the prospects and challenges of metal-coordinated supramolecular self-assemblies for both technical advances and clinical translation are discussed. In particular, the superiority of TME-responsive nanomedicines for in vivo coordinated self-assembly is elaborated, with an emphasis on strategies that enhance the accumulation of functional components in tumors for an ideal theranostic outcome.

Conjugation of oxaliplatin with PEGylated-nanobody for enhancing tumor targeting and prolonging circulation

Oxaliplatin is a platinum-based drug used in clinic for cancer chemotherapy. Despite of its success, the non-selective effect on normal cells causes severe side-effects and hampers its applications. Targeted delivery of oxaliplatin to cancer cells is an effective approach to enhance drug efficacy and reduce adverse effect. In this work, the Pt(IV) prodrug of oxaliplatin has been conjugated to poly(ethylene glycol) (PEG) modified nanobody in order to achieve tumor targeting as well as improved circulation in vivo. The Pt(IV) prodrug was site-specifically linked to an anti-epidermal growth factor receptor (EGFR) nanobody, so that the drug can be accumulated more pronounced in EGFR positive tumor cells than in normal cells. The effect of different length of PEG on the drug circulation has been investigated, while the fusion of anti-albumin nanobody was used for comparison. The result demonstrates that the prolonged drug circulation significantly increases the in vivo drug efficiency of the oxaliplatin-nanobody conjugate.

Prodrug-based nano-delivery strategy to improve the antitumor ability of carboplatin in vivo and in vitro

Chemotherapy plays a major role in the treatment of cancer, but it still has great limitations in anti-tumor effect. Carboplatin (CAR) is the first-line drug in the treatment of non-small cell lung cancer, but the therapeutic effect is demonstrated weak. Therefore, we modified CAR with hexadecyl chain and polyethylene glycol, so as to realize its liposolubility and PEGylation. The synthesized amphiphilic CAR prodrugs could self-assemble into polymer micelles in water with an average particle size about 11.8 nm and low critical micelles concentration (0.0538 mg·mL^-1). In vivo pharmacodynamics and cytotoxicity experiment evidenced that the polymer micelles were equipped with preferable anti-tumor effect, finally attained the aim of elevating anti-tumor effect and prolonging retention time in vivo. The self-assembled micelles skillfully solve the shortcomings of weak efficacy of CAR, which provides a powerful platform for the application of chemical drug in oncology.

Supramolecular agents for combination of photodynamic therapy and other treatments

Photodynamic therapy (PDT) is a promising treatment for cancers such as superficial skin cancers, esophageal cancer, and cervical cancer. Unfortunately, PDT often does not have sufficient therapeutic benefits due to its intrinsic oxygen dependence and the limited permeability of irradiating light. Side effects from "always on" photosensitizers (PSs) can be problematic, and PDT cannot treat tumor metastases or recurrences. In recent years, supramolecular approaches using non-covalent interactions have attracted attention due to their potential in PS development. A supramolecular PS assembly could be built to maximize photodynamic effects and minimize side effects. A combination of two or more therapies can effectively address shortcomings while maximizing the benefits of each treatment regimen. Using the supramolecular assembly, it is possible to design a multifunctional supramolecular PS to exert synergistic effects by combining PDT with other treatment methods. This review provides a summary of important research progress on supramolecular systems that can be used to combine PDT with photothermal therapy, chemotherapy, and immunotherapy to compensate for the shortcomings of PDT, and it provides an overview of the prospects for future cancer treatment advances and clinical applications.

Recent advances in prodrug-based nanoparticle therapeutics

Extensive research into prodrug modification of active pharmaceutical ingredients and nanoparticle drug delivery systems has led to unprecedented levels of control over the pharmacological properties of drugs and resulted in the approval of many prodrug or nanoparticle-based therapies. In recent years, the combination of these two strategies into prodrug-based nanoparticle drug delivery systems (PNDDS) has been explored as a way to further advance nanomedicine and identify novel therapies for difficult-to-treat indications. Many of the PNDDS currently in the clinical development pipeline are expected to enter the market in the coming years, making the rapidly evolving field of PNDDS highly relevant to pharmaceutical scientists. This review paper is intended to introduce PNDDS to the novice reader while also updating those working in the field with a comprehensive summary of recent efforts. To that end, first, an overview of FDA-approved prodrugs is provided to familiarize the reader with their advantages over traditional small molecule drugs and to describe the chemistries that can be used to create them. Because this article is part of a themed issue on nanoparticles, only a brief introduction to nanoparticle-based drug delivery systems is provided summarizing their successful application and unfulfilled opportunities. Finally, the review's centerpiece is a detailed discussion of rationally designed PNDDS formulations in development that successfully leverage the strengths of prodrug and nanoparticle approaches to yield highly effective therapeutic options for the treatment of many diseases.

Polydopamine-carbon dots functionalized hollow carbon nanoplatform for fluorescence-imaging and photothermal-enhanced thermochemotherapy

The low power photothermal therapy can reduce the tissue damage caused by laser irradiation, thus the near-infrared (NIR) absorbing vehicles with high photothermal conversion efficiency are demanded in the low power treatment. Herein, the NIR-absorbing agent polydopamine (PDA) and carbon dots (CDs) were gated on the openings of hollow mesoporous carbon (HMC) to construct a photothermal enhanced multi-functional system (HMC-SS-PDA@CDs). Interestingly, the fluorescence emission wavelength of HMC-SS-PDA@CDs was red-shifted by FRET effect between PDA and CDs, which solved the dilemma of fluorescence quenching of carbon-based materials and was more conducive to cell imaging. The modification of PDA@CDs not only acts as the gatekeepers to realize multi-responsive release of pH, GSH and NIR, but also endows the HMC vehicle with excellent photothermal generation capacity, the possibility for bio-imaging as well as the enhanced stability. Naturally, both the cytological level and the multicellular tumor sphere level demonstrate that the delivery system has good low-power synergistic therapeutic with combination index (CI) of 0.348 and imaging effects. Meanwhile, the combined treatment group showed the highest tumor inhibition rate of 92.6% at 0.75 W/cm². Therefore, DOX/HMC-SS-PDA@CDs nano-platform had broad application prospects in low power therapy and convenient imaging of carbon-based materials.

Construction of a pH- and near-infrared irradiation-responsive nanoplatform for chemo-photothermal therapy

Au nanoclusters, decorated with graphene quantum dots (GQDs), were obtained through photocatalytic reduction of AuCl₄^3- by UV irradiation, and then cytarabine (Cyt) was loaded to the Au/GQDs via charge-dipole interactions. Mercaptopropionic acid (MPA) was anchored to the Cyt-loaded Au/GQDs through the formation of Au-S bond, which was further encapsulated by polyethyleneimine (PEI) via charge-dipole interactions. The delivery of Cyt from the quaternary complex (Au/GQDs/MPA/PEI) is pH-sensitive and can be modulated by near-infrared (NIR) irradiation. The results of cell viability test indicate that the developed nanoplatform can be used for chemo-photothermal combination therapy of cancer cells, and the efficacy of chemo-photothermal combination therapy is significantly higher than that of the single mode of photothermal therapy (PTT) or chemotherapy.

High-Efficiency Synergistic Effect of Supramolecular Nanoparticles Based on Cyclodextrin Prodrug on Cancer Therapy

Novel cyclodextrin-prodrug supramolecular nanoparticles (NPs) with cooperative-enhancing cancer therapy were constructed from a reduction-sensitive disulfide bond-linked permethyl-β-cyclodextrin-camptothecin prodrug, water-soluble adamantane-porphyrin photosensitizer, and hyaluronic acid grafted by triphenylphosphine and β-cyclodextrin through an orthogonal host-guest recognition strategy, displaying uniform nanoparticles with a diameter around 100 nm as revealed by dynamic light scattering, transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. Compared with 293T normal cells, the supramolecular NPs could be easily taken up by mitochondria of A549 cancer cells, then release the active anticancer drug camptothecin (CPT) in situ via the cleavage of the disulfide bond by the overexpressed glutathione, and could initiate the effective singlet oxygen (¹O₂) generation by porphyrin under light irradiation, ultimately resulting in severe mitochondrial dysfunction and a rising cell death rate with increasing micromolar concentration of NPs. These multicomponent supramolecular nanoassemblies effectively combined the two-step synergistic chemo-photodynamic therapy of reduction-release of CPT and light-triggered ¹O₂ generation within cancer cells presenting the synergistic effect of supramolecular nanoparticles on cancer therapy, which provide a new approach for efficient step-by-step cancer therapy.

Selection of Affinity Reagents to Neutralize the Hemolytic Toxicity of Melittin Based on a Self-Assembled Nanoparticle Library

Antibodies are the most common affinity reagents for specific target recognition. However, their applications are limited by high cost and low stability. Thus, seeking substitutes for antibodies is of great significance. In this work, we designed a library containing 82 self-assembled nanoparticles (SNPs) based on the self-assembly of β-cyclodextrin polymers and adamantane derivatives, and then screened out eight types of SNPs capable of suppressing the toxicity of melittin using a hemolytic activity neutralization assay. The affinities of the SNPs to melittin were demonstrated using surface plasmon resonance (SPR). As evidenced by cytotoxicity experiments, SNPs could also suppress the toxicity of melittin to other cells. In addition, to verify the universality of our method, 11 types of SNPs capable of neutralizing another toxic peptide, phenolic soluble polypeptide (PSMα3) secreted by Staphylococcus aureus, were selected from the same SNP library. Our self-assembly-based method for the library preparation has the advantages of flexible design, mild experimental condition, and simple operation, which is expected to seek artificial affinity reagents for more species.

A promising anticancer drug: a photosensitizer based on the porphyrin skeleton

Photodynamic therapy (PDT) is a minimally invasive combination of treatments that treat tumors and other diseases by using photosensitizers, light and oxygen to produce cytotoxic reactive oxygen species (ROS) inducing tumor cell apoptosis. Photosensitizers are the key part of PDT for clinical application and experimental research, and most of them are porphyrin compounds at present. Due to their unique affinity for tumor tissues, porphyrins are not only excellent photosensitizers, but also good carriers to transport other active drugs into tumor tissues, which can exert synergistic anticancer effects of PDT and chemotherapy. This article reviews the clinical development of porphyrin photosensitizers and the research status of porphyrin containing bioactive groups. Finally, future perspectives and the current challenges of photosensitizers based on the porphyrin skeleton are discussed.

Novel photosensitizing properties of porphyrin–chrysin derivatives with antitumor activity in vitro

Photodynamic therapy is a promising cancer treatment with the advantages of low toxicity, high efficiency, and noninvasiveness. In this study, 23 novel porphyrin–chrysin derivatives are synthesized using alkyl carbon chains as bridges. We use human gastric cancer cells (MGC-803) and human cervical cancer cells to evaluate the in vitro antitumor activity of all the porphyrin–chrysin derivatives, with 5-fluorouracil (5-Fu) as a positive control. Several of the prepared compounds showed effective photodynamic killing effects, among which 5-hydroxy-2-phenyl-7-(2-(4-(10,15,20-tris(4-hydroxyphenyl)porphyrin-5-yl)phenoxy)ethoxy)-4 H-chromen-4-one shows the highest antiproliferation activity on human cervical cancer cells, with a half maximal inhibitory concentration of 26.51 ± 1.15 µM. Flow cytometry analysis showed that human cervical cancer cell apoptosis might be induced by G1 phase arrest.

Self-Delivered and Self-Monitored Chemo-Photodynamic Nanoparticles with Light-Triggered Synergistic Antitumor Therapies by Downregulation of HIF-1α and Depletion of GSH

Photodynamic therapy (PDT), a clinically approved cancer treatment, has faced many drawbacks that restricted its applications. For example, the hypoxia-induced elevated hypoxia-inducible factor-1α (HIF-1α) may desensitize tumors to PDT, and the high concentration of glutathione (GSH) in cancer cells can also neutralize the generated reactive oxygen species (ROS) during PDT, resulting in insufficient therapy. Moreover, extra probes for imaging-guided visualization therapy are always needed to track drug release or distribution, while it may decrease the drug loading of the drug delivery system (DDS). In the present study, we have designed and prepared a novel multifunctional combined therapy nanoparticle (ZnPc@Cur-S-OA NPs), in which curcumin (Cur) was not only used as a chemotherapy drug to achieve a combination therapy with PDT via downregulating HIF-1α and depleting GSH in B16F10 cells but also designed as a small-molecule ROS-triggered release prodrug to deliver the photosensitizer (PS). The red fluorescence of PS in the nanoparticles (NPs) can be used to track the NPs distribution, while the green fluorescence of Cur showed an "OFF-ON" activation, which enables additional imaging and real-time self-monitoring capabilities. These results proved that the prepared combined therapy NPs were more effective to inhibit the growth of B16F10 mouse melanoma tumor than was monotherapy without eliciting systemic toxicity either in vitro or in vivo, which indicated the combined therapy NPs as an effective way to improve the PDT efficacy via downregulation of HIF-1α and depletion of GSH. Thus, the strategy of using a multifunctional natural product as the stimuli-responsive carrier as well as the synergist with PDT for enhancing antitumor efficacy via multiple pathways may open an alternative avenue to fabricate new self-delivery combination therapy nanodrugs. Besides, the fluorescence emitted from the drug can be used for real-time self-monitoring of drug release and distribution, which has great potential in clinic to adjust the administration dose and irradiation time for different tumor types and stages for individual therapy.

Glycosylated porphyrin-cucurbituril conjugate for photodynamic inactivation of bacteria and doxorubicin carriage for anticancer drug delivery

Porphyrin derivatives are highly attractive in the construction of multifunctional molecular platforms with interesting properties and applications. In this regard, we report here the use of a multifunctional porphyrin-based molecular platform as a photosensitizer for photodynamic therapy and as a drug carrier. This molecular platform was constructed by conjugating a host molecule, cucurbit[7]uril to a triglycosylated tetraphenyl porphyrin and serves very efficiently as a photosensitizer in the inactivation of both gram-negative (Escherichia coli, E. coli) and gram-positive bacteria (Bacillus subtilis, B. subtilis) and growth inhibition of cancer cells as well as a doxorubicin (DOX) carrier for chemo-photodynamic dual cancer therapy. Another remarkable feature of this photosensitizer is that it shows negligible cytotoxicity in the dark.

pH and singlet oxygen dual-responsive GEM prodrug micelles for efficient combination therapy of chemotherapy and photodynamic therapy

Nanocarriers have been an important strategy for enhancing the combination therapy of chemotherapy and photodynamic therapy (PDT) (Chem-PDT).

Supramolecular nanomaterials based on hollow mesoporous drug carriers and macrocycle-capped CuS nanogates for synergistic chemo-photothermal therapy

Multifunctional supramolecular nanoplatforms that integrate the advantages of different therapeutic techniques can trigger multimodal synergistic treatment of tumors, thus representing an emerging powerful tool for cancer therapeutics. Methods: In this work, we design and fabricate a multifunctional supramolecular drug delivery platform, namely Fa-mPEG@CP5-CuS@HMSN-Py nanoparticles (FaPCH NPs), consisting of a pyridinium (Py)-modified hollow mesoporous silica nanoparticles-based drug reservoir (HMSN-Py) with high loading capacity, a layer of NIR-operable carboxylatopillar[5]arene (CP5)-functionalized CuS nanoparticles (CP5-CuS) on the surface of HMSN-Py connected through supramolecular host-guest interactions between CP5 rings and Py stalks, and another layer of folic acid (Fa)-conjugated polyethylene glycol (Fa-PEG) antennas by electrostatic interactions capable of active targeting at tumor lesions, in a controlled, highly integrated fashion for synergistic chemo-photothermal therapy. Results: Fa-mPEG antennas endowed the enhanced active targeting effect toward cancer cells, and CP5-CuS served as not only a quadruple-stimuli responsive nanogate for controllable drug release but also a special agent for NIR-guided photothermal therapy. Meanwhile, anticancer drug doxorubicin (DOX) could be released from the HMSN-Py reservoirs under tumor microenvironments for chemotherapy, thus realizing multimodal synergistic therapeutics. Such a supramolecular drug delivery platform showed effective synergistic chemo-photothermal therapy both in vitro and in vivo. Conclusion: This novel supramolecular nanoplatform possesses great potential in controlled drug delivery and tumor cellular internalization for synergistic chemo-photothermal therapy, providing a promising approach for multimodal synergistic cancer treatment.

A Luminescent Amine-Functionalized Metal-Organic Framework Conjugated with Folic Acid as a Targeted Biocompatible pH-Responsive Nanocarrier for Apoptosis Induction in Breast Cancer Cells

Folic acid amine-functionalized metal-organic framework (FOLA@NH₂-Eu:TMU-62) with luminescent properties loaded with 5-fluorouracil (5-Fu), as an anticancer medication, was used to construct a new cancer targeted drug delivery system in the present study. The 5-Fu release from this targeted carrier along with MTT assay and trypan blue dye exclusion test results also exhibited pH-controlled characteristics of the given carrier in acidic environments, which is very suitable for targeting solid tumors. Then, the inhibitory action of 5-Fu-loaded FOLA@NH₂-Eu:TMU-62 for Michigan Cancer Foundation-7 (MCF7) cell migration was explored according to scratch wound healing assays. Based on the results, the FOLA@NH₂-Eu:TMU-62 carrier was not toxic for MCF-10A normal cells, but it was significantly toxic for MCF-7 breast cancer ones, revealing that the FOLA@NH₂-Eu:TMU-62 carrier could be utilized in accurate cancer treatments through apoptotic pathways with higher reactive oxygen species compared with 5-Fu alone. This cancer-targeted design of FOLA@NH₂-Eu:TMU-62 could thus pave the way for synergistic effects of targeting as well as organized release capabilities.

Multistep Consolidated Phototherapy Mediated by a NIR-Activated Photosensitizer

The multifunctional effect of a single molecule for therapeutic functionalities on a single theranostic nanosystem has a great significance to enhance the accuracy of diagnosis and improve the efficacy of therapy. Herein, a biocompatible multistep phototherapeutic system (Ppa-Cy7-PEG-biotin) that contains a photosensitizer pyropheophorbide A (Ppa) with the covalent conjunction of a near-infrared (NIR) cyanine dye (Cy7) was successfully fabricated and functionalized with biotin for flexible specific tumor-targeting phototherapy. These theranostic micelles will disaggregate after NIR irradiation via the photodegradation of cyanine accompanied by the photothermal conversion and the optically controlled release for the restoration of photodynamic function of quenched Ppa. Consecutively, promoted treatments of photosensitive molecules greatly prolonged the tumor retention time and treatment efficiency, having a multistep antitumor effect both in vitro and in vivo. Different from the simple phototherapeutic configurations that only act on the superficial areas of tumors at mild doses, the multistep therapy can be competent for broadly damaging the superficial and deeper regions of tumors at the same dose. Therefore, as opposed to the general combination phototherapeutic approach, this strategy presents a photoactivation-based multistep phototheranostic platform with an enormous potential in enhanced combined phototherapy for cancer.

Acid-Triggered Nanoexpansion Polymeric Micelles for Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) as a noninvasive and selective treatment technology has presented great potential in cancer prevention and precision medicine, but its therapeutic efficacy is still greatly inhibited by the limitations of photosensitizers (PSs) in the microenvironment such as the aggregation caused quenching (ACQ) of PSs. Herein, we proposed an "acid-triggered nanoexpansion" method to further reduce the aggregation of photosensitizers by constructing acetal-based polymeric micelles. A pH-responsive amphiphilic block copolymer, POEGMA-b-[PTTMA-co-PTPPC6MA] was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and self-assembled into spherical micelles. In the normal physiological environment, the micelles were stable and had good biocompatibility. Upon entry into the acidic microenvironment of the tumor, the acid-responsive hydrophobic 2, 4, 6-trimethoxybenzaldehyde in the micelles hydrolyzed and generated a hydrophilic diol moiety. Although the hydrophility of the micellar core was increased, the assembled structure of block copolymers was not dissociated but expanded. The responsive expansion of the micelles could allow the photosensitizers to well-disperse in the core, whereas more tumor-dissolved oxygen entered the micelles. This phenomenon could provide a better nanoenvironment for photosensitizers to reduce the ACQ of the photosensitizers, leading to more singlet oxygen (¹O₂) produced under the laser irradiation (650 nm). Both in vitro and in vivo studies have demonstrated that the remarkable photodynamic therapeutic efficacy of acid-responsive micelles could be realized. Thus, the acid-triggered nanoexpansion method might provide more possibilities to develop efficient platforms for treating cancers.