Photosensitizer-stabilized self-assembling nanoparticles potentiate chemo/photodynamic efficacy of patient-derived melanoma

Tetrasulfide bond boosts the anti-tumor efficacy of dimeric prodrug nanoassemblies

Dimeric prodrug nanoassemblies (DPNAs) stand out as promising strategies for improving the efficiency and safety of chemotherapeutic drugs. The success of trisulfide bonds (-SSS-) in DPNAs makes polysulfide bonds a worthwhile focus. Here, we explore the comprehensive role of tetrasulfide bonds (-SSSS-) in constructing superior DPNAs. Compared to trisulfide and disulfide bonds, tetrasulfide bonds endow DPNAs with superlative self-assembly stability, prolonged blood circulation, and high tumor accumulation. Notably, the ultra-high reduction responsivity of tetrasulfide bonds make DPNAs a highly selective "tumor bomb" that can be ignited by endogenous reducing agents in tumor cells. Furthermore, we present an "add fuel to the flames" strategy to intensify the reductive stress at tumor sites by replenishing exogenous reducing agents, making considerable progress in selective tumor inhibition. This work elucidates the crucial role of tetrasulfide bonds in establishing intelligent DPNAs, alongside the combination methodology, propelling DPNAs to new heights in potent cancer therapy.

The effect of lengths of branched-chain fatty alcohols on the efficacy and safety of docetaxel-prodrug nanoassemblies

The self-assembly prodrugs are usually consisted of drug modules, activation modules, and assembly modules. Keeping the balance between efficacy and safety by selecting suitable modules remains a challenge for developing prodrug nanoassemblies. This study designed four docetaxel (DTX) prodrugs using disulfide bonds as activation modules and different lengths of branched-chain fatty alcohols as assembly modules (C16, C18, C20, and C24). The lengths of the assembly modules determined the self-assembly ability of prodrugs and affected the activation modules' sensitivity. The extension of the carbon chains improved the prodrugs' self-assembly ability and pharmacokinetic behavior while reducing the cytotoxicity and increased cumulative toxicity. The use of C20 can balance efficacy and safety. These results provide a great reference for the rational design of prodrug nanoassemblies.

A Trojan horse approach for efficient drug delivery in photodynamic therapy: focus on taxanes

Photodynamic therapy is an effective method for the treatment of several types of cancerous and noncancerous diseases. The key to the success of this treatment method is effective drug delivery to the site of action, for instance, a tumor. This ensures not only the high effectiveness of the therapy but also the suppression of side effects. But how to achieve effective targeted delivery? Lately, much attention has been paid to systems based on the so-called Trojan horse model, which is gaining increasing popularity. The principle of this model is that the effective drug is hidden in the internal structure of a nanoparticle, liposome, or nanoemulsion and is released only at the site of action. In this review article, we focus on drugs from the group of mitotic poisons, taxanes, and their use with photosensitizers in combined therapy. Here, we discuss the possibilities of how to improve the paclitaxel and docetaxel bioavailability, as well as their specific targeting for use in combined photo- and chemotherapy. Moreover, we also present the state of the art multifunctional drugs based on cabazitaxel which, owing to a suitable combination with photosensitizers, can be used besides photodynamic therapy and also in photoacoustic imaging or sonodynamic therapy.

Dynamic nanoassemblies derived from small-molecule homodimeric prodrugs for in situ drug activation and safe osteosarcoma treatment

Supramolecular prodrug self-assembly is a cost-effective and powerful approach for creating injectable anticancer nanoassemblies. Herein, we describe the self-assembly of small-molecule prodrug nanotherapeutics for tumor-restricted pharmacology that can be self-activated and independent of the exogenous stimuli. Covalent dimerization of the anticancer agent cabazitaxel via reactive oxygen species (ROS)- and esterase-activatable linkages produced the homodimeric prodrug diCTX, which was further coassembled with an ROS generator, dimeric dihydroartemisinin (diDHA). The coassembled nanoparticles were further refined in an amphiphilic matrix, making them suitable for in vivo administration. The ROS obtained from the coassembled diDHA synergized with intracellular esterase to activate the neighboring diCTX, which in turn induced potent cytotoxicity. In a preclinical orthotopic model of human osteosarcomas, nanoparticle administration exhibited durable antitumor efficacy. Furthermore, this smart, dual-responsive nanotherapeutic exhibited lower toxicity in animals than those of free drug combinations. We predict that this platform has great potential for further clinical translation.

Self-delivery biomedicine for enhanced photodynamic therapy by feedback promotion of tumor autophagy

Reactive oxygen species (ROS) generated during photodynamic therapy (PDT) can induce autophagy to protect tumor cell from PDT-induced apoptosis. In this work, a self-delivery autophagy regulator (designated as CeCe) is developed for autophagy promotion sensitized PDT against tumor. Briefly, CeCe is prepared by the assembly of a photosensitizer of chlorin e6 (Ce6) and autophagy promoter of celastrol. By virtue of intermolecular interactions, Ce6 and celastrol are able to self-assemble into nanomedicine with great photodynamic performance and autophagy regulation capacity. Under light irradiation, CeCe would produce ROS in tumor cells to amplify the oxidative stress and promote cell autophagy. As a result, CeCe exhibits an enhanced photo toxicity by inducing autophagic cell death. In vivo experiments indicate that CeCe can predominantly accumulate in tumor tissue for a robust PDT. Moreover, CeCe has a superior therapeutic efficiency compared to monotherapy and combined treatment of Ce6 and celastrol, suggesting a synergistic antitumor effect of PDT and autophagy promotion. This self-delivery nanomedicine may advance the development of the co-delivery nanoplatform to improve the antitumor efficacy of PDT by promoting autophagy. STATEMENT OF SIGNIFICANCE: Autophagy is a "double-edged sword" in cellular homeostasis and metabolism, which can promote tumor progression but also induce an unknown impact on tumor inhibition. In this work, a self-delivery autophagy regulator (designated as CeCe) was developed for autophagy promotion sensitized photodynamic therapy (PDT). By virtue of intermolecular interactions, Ce6 and celastrol were found to self-assemble into stable CeCe without drug excipients, which exhibited great photodynamic performance and autophagy regulation capacity. In vitro and in vivo findings demonstrated a superior tumor suppression ability of CeCe over the monotherapy as well as the combined treatment of Ce6 and celastrol, suggesting a synergistic antitumor efficacy by PDT and autophagy promotion.

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.

Patient-derived xenograft model in colorectal cancer basic and translational research

Colorectal cancer (CRC) is one of the most popular malignancies globally, with 930 000 deaths in 2020. The evaluation of CRC-related pathogenesis and the discovery of potential therapeutic targets will be meaningful and helpful for improving CRC treatment. With huge efforts made in past decades, the systematic treatment regimens have been applied to improve the prognosis of CRC patients. However, the sensitivity of CRC to chemotherapy and targeted therapy is different from person to person, which is an important cause of treatment failure. The emergence of patient-derived xenograft (PDX) models shows great potential to alleviate the straits. PDX models possess similar genetic and pathological characteristics as the features of primary tumors. Moreover, PDX has the ability to mimic the tumor microenvironment of the original tumor. Thus, the PDX model is an important tool to screen precise drugs for individualized treatment, seek predictive biomarkers for prognosis supervision, and evaluate the unknown mechanism in basic research. This paper reviews the recent advances in constructed methods and applications of the CRC PDX model, aiming to provide new knowledge for CRC basic research and therapeutics.

High Drug-Loading Nanomedicines for Tumor Chemo-Photo Combination Therapy: Advances and Perspectives

The combination of phototherapy and chemotherapy (chemo−photo combination therapy) is an excellent attempt for tumor treatment. The key requirement of this technology is the high drug-loading nanomedicines, which can load either chemotherapy drugs or phototherapy agents at the same nanomedicines and simultaneously deliver them to tumors, and play a multimode therapeutic role for tumor treatment. These nanomedicines have high drug-loading efficiency (>30%) and good tumor combination therapeutic effect with important clinical application potential. Although there are many reports of high drug-loading nanomedicines for tumor therapy at present, systematic analyses on those nanomedicines remain lacking and a comprehensive review is urgently needed. In this review, we systematically analyze the current status of developed high drug-loading nanomedicines for tumor chemo−photo combination therapy and summarize their types, methods, drug-loading properties, in vitro and in vivo applications. The shortcomings of the existing high drug-loading nanomedicines for tumor chemo−photo combination therapy and the possible prospective development direction are also discussed. We hope to attract more attention for researchers in different academic fields, provide new insights into the research of tumor therapy and drug delivery system and develop these nanomedicines as the useful tool for tumor chemo−photo combination therapy in the future.

Taxanes prodrug-based nanomedicines for cancer therapy

Malignant tumor remains a huge threat to human health and chemotherapy still occupies an important place in clinical tumor treatment. As a kind of potent antimitotic agent, taxanes act as the first-line broad-spectrum cancer drug in clinical use. However, disadvantages such as prominent hydrophobicity, severe off-target toxicity or multidrug resistance lead to unsatisfactory therapeutic effects, which restricts its wider usage. The efficient delivery of taxanes is still quite a challenge despite the rapid developments in biomaterials and nanotechnology. Great progress has been made in prodrug-based nanomedicines (PNS) for cancer therapy due to their outstanding advantages such as high drug loading efficiency, low carrier induced immunogenicity, tumor stimuli-responsive drug release, combinational therapy and so on. Based on the numerous developments in this filed, this review summarized latest updates of taxanes prodrugs-based nanomedicines (TPNS), focusing on polymer-drug conjugate-based nanoformulations, small molecular prodrug-based self-assembled nanoparticles and prodrug-encapsulated nanosystems. In addition, the new trends of tumor stimuli-responsive TPNS were also discussed. Moreover, the future challenges of TPNS for clinical translation were highlighted. We here expect this review will inspire researchers to explore more practical taxanes prodrug-based nano-delivery systems for clinical use.

Chemodynamic and Photothermal Combination Therapy Based on Dual-Modified Metal-Organic Framework for Inducing Tumor Ferroptosis/Pyroptosis

Single therapy for tumor therapy always exerts limited ability for the constraints on the reaction condition and the unavoidable multidrug resistance, which seriously influences the therapy effect in the clinic. Herein, a combination treatment nanosystem (MP@PI) based on chemodynamic therapy (CDT) and photothermal therapy (PTT) is constructed for triggering ferroptosis/pyroptosis, which is the metal-organic framework (MOF) modified with polydopamine (PDA) and IR820 to loaded with piperlongumine (PL). The MOF and PL respectively served as the iron source and H₂O₂ source, performing chemodynamic therapy (CDT) for eliciting ferroptosis. Meanwhile the iron source induces pyroptosis in tumor cells. PDA is not only pH responsive to release PL but also CDT-assisted which due to PDA consumes the glutathione to decrease the expression of glutathione peroxide 4. The photosensitizer IR820 exerts photothermal effects under near-infrared light and further facilitates the ferroptosis/pyroptosis. In addation, the MP@PI nanoplatform evokes the immune response in vivo and enhances the antitumor effects further. Overall, MP@PI is a kind of promising cancer therapy strategy through CDT and PTT combination, inducing ferroptosis and pyroptosis.

Binary dimeric prodrug nanoparticles for self-boosted drug release and synergistic chemo-photodynamic therapy

Chemotherapy is the major strategy for cancer therapy, but its limited therapeutic efficiency and serious toxicity to normal tissues greatly restrict its clinical performance. Herein, we develop carrier-free self-activated prodrug nanoparticles combining chemotherapy and photodynamic therapy to enhance the antitumor efficiency. Reactive oxygen species (ROS)-responsive paclitaxel and porphyrin prodrugs are synthesized and co-assembled into nanoparticles without the addition of any adjuvants, which improves the drug content and reduces carrier-associated toxicity. After entering cancer cells, the obtained co-assembled nanoparticles can generate sufficient ROS upon light irradiation not only for photodynamic therapy, but also triggering on-demand drug release for chemotherapy, thus realizing self-enhanced prodrug activation and synergistic chemo-photodynamic therapy. This simple and effective carrier-free prodrug nanoplatform unifies the distinct traits of on-demand drug release and combination therapy, thus possessing great potential in advancing cancer treatment.

Smart Nanoparticles as Advanced Anti-Akt Kinase Delivery Systems for Pancreatic Cancer Therapy

Pancreatic cancer is one of the deadliest cancers partly due to late diagnosis, poor drug delivery to the target site, and acquired resistance to therapy. Therefore, more effective therapies are urgently needed to improve the outcome of patients. In this work, we have tested self-assembling genetically engineered polymeric nanoparticles formed by elastin-like recombinamers (ELRs), carrying a small peptide inhibitor of the protein kinase Akt, in both PANC-1 and patient-derived pancreatic cancer cells (PDX models). Nanoparticle cell uptake was measured by flow cytometry, and subcellular localization was determined by confocal microscopy, which showed a lysosomal localization of these nanoparticles. Furthermore, metabolic activity and cell viability were significantly reduced after incubation with nanoparticles carrying the Akt inhibitor in a time- and dose-dependent fashion. Self-assembling 73 ± 3.2 nm size nanoparticles inhibited phosphorylation and consequent activation of Akt protein, blocked the NF-κB signaling pathway, and triggered caspase 3-mediated apoptosis. Furthermore, in vivo assays showed that ELR-based nanoparticles were suitable devices for drug delivery purposes with long circulating time and minimum toxicity. Hence, the use of these smart nanoparticles could lead to the development of more effective treatment options for pancreatic cancer based on the inhibition of Akt.

Small-Molecule Prodrug Nanoassemblies: An Emerging Nanoplatform for Anticancer Drug Delivery

The antitumor efficiency and clinical translation of traditional nanomedicines is mainly restricted by low drug loading, complex preparation technology, and potential toxicity caused by the overused carrier materials. In recent decades, small-molecule prodrug nanoassemblies (SMP-NAs), which are formed by the self-assembly of prodrugs themselves, have been widely investigated with distinct advantages of ultrahigh drug-loading and negligible excipients-trigged adverse reaction. Benefited from the simple preparation process, SMP-NAs are widely used for chemotherapy, phototherapy, immunotherapy, and tumor diagnosis. In addition, combination therapy based on the accurate co-delivery behavior of SMP-NAs can effectively address the challenges of tumor heterogeneity and multidrug resistance. Recent trends in SMP-NAs are outlined, and the corresponding self-assembly mechanisms are discussed in detail. Besides, the smart stimuli-responsive SMP-NAs and the combination therapy based on SMP-NAs are summarized, with special emphasis on the structure-function relationships. Finally, the outlooks and potential challenges of SMP-NAs in cancer therapy are highlighted.

Nanoparticle-Based Drug Delivery Systems for Photodynamic Therapy of Metastatic Melanoma: A Review

Metastatic melanoma (MM) is a skin malignancy arising from melanocytes, the incidence of which has been rising in recent years. It poses therapeutic challenges due to its resistance to chemotherapeutic drugs and radiation therapy. Photodynamic therapy (PDT) is an alternative non-invasive modality that requires a photosensitizer (PS), specific wavelength of light, and molecular oxygen. Several studies using conventional PSs have highlighted the need for improved PSs for PDT applications to achieve desired therapeutic outcomes. The incorporation of nanoparticles (NPs) and targeting moieties in PDT have appeared as a promising strategy to circumvent various drawbacks associated with non-specific toxicity, poor water solubility, and low bioavailability of the PSs at targeted tissues. Currently, most studies investigating new developments rely on two-dimensional (2-D) monocultures, which fail to accurately mimic tissue complexity. Therefore, three-dimensional (3-D) cell cultures are ideal models to resemble tumor tissue in terms of architectural and functional properties. This review examines various PS drugs, as well as passive and active targeted PS nanoparticle-mediated platforms for PDT treatment of MM on 2-D and 3-D models. The overall findings of this review concluded that very few PDT studies have been conducted within 3-D models using active PS nanoparticle-mediated platforms, and so require further investigation.

GSH-Responsive Nanoprodrug to Inhibit Glycolysis and Alleviate Immunosuppression for Cancer Therapy

Blocking energy metabolism of cancer cells and simultaneously stimulating the immune system to perform immune attack are significant for cancer treatment. However, how to potently deliver different drugs with these functions remains a challenge. Herein, we synthesized a nanoprodrug formed by a F127-coated drug dimer to inhibit glycolysis of cancer cells and alleviate the immunosuppressive microenvironment. The dimer was delicately constructed to connect lonidamine (LND) and NLG919 by a disulfide bond which can be cleaved by excess GSH to release two drugs. LND can decrease the expression of hexokinase II and destroy mitochondria to restrain glycolysis for energy supply. NLG919 can reduce the accumulation of kynurenine and the number of regulatory T cells, thus alleviating the immunosuppressive microenvironment. Notably, the consumption of GSH by disulfide bond increased the intracellular oxidative stress and triggered immunogenic cell death of cancer cells. This strategy can offer more possibilities to explore dimeric prodrugs for synergistic cancer therapy.

Nanobody modified high-performance AIE photosensitizer nanoparticles for precise photodynamic oral cancer therapy of patient-derived tumor xenograft

Photodynamic therapy (PDT) is a promising noninvasive treatment option for patients suffering from superficial tumors, such as oral cancer. However, for photosensitizers (PSs), it remains a grand challenge to simultaneously excel in all the key performance indicators including effective singlet oxygen (¹O₂) generation under clinical laser, specific targeting function and stable far-red (FR)/near-infrared (NIR) emission with low dark toxicity. In addition, traditional PS nanoparticles (NPs) for clinical use suffer from quenched fluorescence and reduced ¹O₂ production caused by molecular aggregation. To address these issues, AIEPS5 with aggregation-induced FR/NIR emission and effective ¹O₂ generation under 532 nm laser irradiation is designed by precise optimization of the chemical structure. By attaching a polyethylene glycol (PEG) chain onto AIEPS5, the yielded amphiphilic AIEPS5-PEG2000 can spontaneously self-assemble into water dispersible NPs, which are further endowed with targeted delivery function via the decoration of anti-Her-2 nanobody (NB). The bespoke AIEPS5-NPs-NB exhibit effective ¹O₂ generation capability, bright FR/NIR emission centered at 680 nm, and negligible dark toxicity, which outperform Heimbofen, a clinically approved PS in PDT using a patient-derived tumor xenograft model.

Emerging nanotaxanes for cancer therapy

The clinical application of taxane (including paclitaxel, docetaxel, and cabazitaxel)-based formulations is significantly impeded by their off-target distribution, unsatisfactory release, and acquired resistance/metastasis. Recent decades have witnessed a dramatic progress in the development of high-efficiency, low-toxicity nanotaxanes via the use of novel biomaterials and nanoparticulate drug delivery systems (nano-DDSs). Thus, in this review, the achievements of nanotaxanes-targeted delivery and stimuli-responsive nano-DDSs-in preclinical or clinical trials have been outlined. Then, emerging nanotherapeutics against tumor resistance and metastasis have been overviewed, with a particular emphasis on synergistic therapy strategies (e.g., combination with surgery, chemotherapy, radiotherapy, biotherapy, immunotherapy, gas therapy, phototherapy, and multitherapy). Finally, the latest oral nanotaxanes have been briefly discussed.

Kinetically-stable small-molecule prodrug nanoassemblies for cancer chemotherapy

Self-delivering nanocarrier based on the small-molecule prodrug nanoassemblies (NAs) have been widely used for the efficient delivery of chemotherapeutics, but the effect of kinetic stability of NAs on their delivery performance has not been illuminated. In this study, two camptothecin (CPT)-oleic acid (OA) prodrugs were used to fabricate self-assembling nanorods with similar size distribution, zeta potential and morphology but having sharply different kinetic stability, which provided an ideal platform to investigate the effects of kinetic stability. It is found that the nanorods with high kinetic stability showed a lower in vitro cytotoxicity, but were more effective to inhibit the tumor growth probably by decreasing the premature CPT release and subsequent generation of the inactive carboxylate CPT. However, such kinetically stable nanorods also resulted in the increased toxicity, probably due to the high prodrug accumulation in tissues after multiple injections. These results outlined the pivotal role of kinetic stability in determining antitumor efficacy of prodrug NAs, which provided a new insight into the delivery mechanism for the small-molecule prodrug self-delivering nanosystems.

Supramolecular nanoparticles self-assembled from reduction-responsive cabazitaxel prodrugs for effective cancer therapy

Using hydrophobic cabazitaxel as a target anticancer drug, we show that the conjugation of oligo(ethylene glycol)-oligolactide (OEG-OLA) via a self-immolative linkage induces the self-assembly of the resulting prodrug into injectable nanoparticles. The nanoparticles release chemically unmodified cabazitaxel after endocytosis in cancer cells. With the optimal conjugate, the nanotherapy not only potently induces tumor regression but also has a higher safety margin in animals than the free drug administered in its clinical formulation. Our studies highlight the design rationale that attaching a short amphiphilic oligomer to a toxic drug can convert it to a self-deliverable and safe nanotherapy.

Current Limitations and Recent Progress in Nanomedicine for Clinically Available Photodynamic Therapy

Photodynamic therapy (PDT) using oxygen, light, and photosensitizers has been receiving great attention, because it has potential for making up for the weakness of the existing therapies such as surgery, radiation therapy, and chemotherapy. It has been mainly used to treat cancer, and clinical tests for second-generation photosensitizers with improved physicochemical properties, pharmacokinetic profiles, or singlet oxygen quantum yield have been conducted. Progress is also being made in cancer theranostics by using fluorescent signals generated by photosensitizers. In order to obtain the effective cytotoxic effects on the target cells and prevent off-target side effects, photosensitizers need to be localized to the target tissue. The use of nanocarriers combined with photosensitizers can enhance accumulation of photosensitizers in the tumor site, owing to preferential extravasation of nanoparticles into the tumor vasculature by the enhanced permeability and retention effect. Self-assembly of amphiphilic polymers provide good loading efficiency and sustained release of hydrophobic photosensitizers. In addition, prodrug nanomedicines for PDT can be activated by stimuli in the tumor site. In this review, we introduce current limitations and recent progress in nanomedicine for PDT and discuss the expected future direction of research.

Dual-Responsive Polyprodrug Nanoparticles with Cascade-Enhanced Magnetic Resonance Signals for Deep-Penetration Drug Release in Tumor Therapy

Smart transformable nanocarriers are promising to treat deep-seated diseases but require adaptable diagnostic/imaging potency to reflect the morphology change and therapeutic feedback, yet their design and synthesis remains challenging. Herein, stimuli-responsive polyprodrug nanoparticles (SPNs) are formulated from the co-assembly of negatively charged corona and positively charged polyprodrug cores, exhibiting high loading content of camptothecin (CPT, ∼28.6 wt %) tethered via disulfide linkages in the core. SPNs are sequentially sensitive to tumor acidic condition and elevated reductive milieu in the cytosol for deep-penetration drug delivery. Upon accumulation at acidic tumor sites, SPNs dissociate to release smaller positively charged polyprodrug nanoparticles, which efficiently enter deep-seated tumor cells to trigger high-dosage parent CPT release in the reductive cytosolic milieu. Meanwhile, the polyprodrug cores of SPNs labeled with DTPA(Gd), a magnetic resonance imaging contrast agent, can trace the cascade degradation and biodistribution of SPNs as well as the resulting intracellular CPT release. The longitudinal relaxivity of SPNs increases stepwise in the above two processes. The size-switchable polyprodrug nanoparticles exhibit remarkable tumor penetration and noteworthy tumor inhibition in vitro and in vivo, which are promising for endogenously activated precision diagnostics and therapy.