Strategies to Improve Photodynamic Therapy Efficacy of Metal-Free Semiconducting Conjugated Polymers

Radionuclide-labelled nanoparticles for cancer combination therapy: a review

Radionuclide therapy (RT) is widely used to advanced local cancers. However, its therapeutic efficacy is limited to the radiation resistance of cancer cells. Combination therapy aims to circumvent tumor resistance, and the combination of RT with photothermal therapy (PTT), photodynamic therapy (PDT), chemotherapy (CMT), and immunotherapy has shown promising treatment outcomes. Nanotechnology holds promise in advancing combination therapy by integrating multiple therapies on a nanostructure platform. This is due to the increased surface area, passive/active targeting capabilities, high payload capacity, and enriched surface of nanomedicines, offering significant advantages in treatment sensitivity and specificity. In the first part of this review, we categorize radionuclide therapy. The second part summarizes the latest developments in combination therapies, specifically focusing on the integration of RT with PTT, PDT, CMT and immunotherapy. The last part provides an overview of the challenges and potential opportunities related to radionuclide-labelled nanoparticles for cancer combination therapy.

Fe-HCOF-PEG2000 as a Hypoxia-Tolerant Photosensitizer to Trigger Ferroptosis and Enhance ROS-Based Cancer Therapy

Background

The hypoxic tumor microenvironment and single mechanisms severely limit the photodynamic therapy (PDT) efficiency of covalent organic framework (COF) nanoparticles in cancer treatment.

Purpose

Here, we propose an iron-loaded, hydrophilic 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DSPE-PEG2000)-modified hollow covalent organic framework (HCOF), Fe-HCOF-PEG2000, for use in hypoxic PDT and ferroptosis therapy owing to its type I and II photodynamic ability and iron nanoparticle loading property.

Results

Fe-HCOF-PEG2000 nanoparticles (Fe-HCOFs-PEG2000) with semiconducting polymers and microporous skeletons allow efficient photophysical properties. Moreover, the iron nanoparticles on Fe-HCOF-PEG2000 caused ferroptosis and further enhanced tumor elimination under normoxic and hypoxic conditions. DSPE-PEG2000 endowed Fe-HCOF-PEG2000 with hydrophilicity, allowing it to circulate and accumulate in organs rich in blood supply, especially tumors. 808 nm NIR activated Fe-HCOF-PEG2000 aggregated in tumors and significantly inhibited tumor growth under hypoxia.

Conclusion

To our knowledge, Fe-HCOF-PEG2000 is the leading combination of type I/II PDT and ferroptosis. The strong antitumor effects of this nanomaterial suggest prospects for clinical translation as a tumor nanotherapy drug.

Enhancing tumor immunotherapy via photodynamic therapy with a cascade reaction of reactive oxygen species and sustaining nutrient supply

Photo-immunotherapy is a promising strategy for the treatment of malignancies; however, its efficacy is often limited by the low tumor immunogenicity and immunosuppressive tumor microenvironment (TME). TME is typically deficient in L-arginine (L-Arg), which negatively impacts T cell survival and function. To address this issue, we developed a novel drug delivery system based on the multi-vesicular liposomes (MVLs) loaded with photosensitizer indocyanine green (ICG) and L-Arg (R), named R-ICG@MVLs. Under near-infrared (NIR) light irradiation, the PDT-mediated cascade reaction of reactive oxygen species (ROS) could oxidize a portion of L-Arg to generate NO, thereby inducing immunogenic tumor cell death (ITCD) and stimulating anti-tumor immune responses, including antigen-presenting cells (APCs) recruitment and T cells activation. Subsequently, R-ICG@MVLs continued to release L-Arg, which improved the immunosuppressive TME, providing nutritional support for the tumor-infiltrating T cells and thus enhancing their anti-tumor efficacy. Additionally, the photo-thermal effect of ICG could accelerate the membrane rearrangement of R-ICG@MVLs and produce multiple drug-loaded nanovesicles, thus enabling the NIR-controlled accelerated drug release. The formation of drug-loaded nanovesicles led to deeper penetration and widened the range of ICD and TME improvement, achieving a "shrapnel effect". In conclusion, our strategy realized the dual effects of immune activation and nutrition support, which might provide a clinically applicable reference for tumor immunotherapy.

Recent Strategies to Develop Conjugated Polymers for Detection and Therapeutics

The infectious diseases resulting from pathogenic microbes are highly contagious and the source of infection is difficult to control, which seriously endangers life and public health safety. Although the emergence of antibiotics has a good therapeutic effect in the early stage, the massive abuse of antibiotics has brought about the evolution of pathogens with drug resistance, which has gradually weakened the lethality and availability of antibiotics. Cancer is a more serious disease than pathogenic bacteria infection, which also threatens human life and health. Traditional treatment methods have limitations such as easy recurrence, poor prognosis, many side effects, and high toxicity. These two issues have led to the exploration and development of novel therapeutic agents (such as conjugated polymers) and therapeutic strategies (such as phototherapy) to avoid the increase of drug resistance and toxic side effects. As a class of organic polymer biological functional materials with excellent photoelectric properties, Conjugated polymers (CPs) have been extensively investigated in biomedical fields, such as the detection and treatment of pathogens and tumors due to their advantages of easy modification and functionalization, good biocompatibility and low cost. A rare comprehensive overview of CPs-based detection and treatment applications has been reported. This paper reviews the design strategies and research status of CPs used in biomedicine in recent years, introduces and discusses the latest progress of their application in the detection and treatment of pathogenic microorganisms and tumors according to different detection or treatment methods, as well as the limitations and potential challenges in prospective exploration.

Periodic Mesoporous Ionosilica Nanoparticles for Dual Cancer Therapy: Two-Photon Excitation siRNA Gene Silencing in Cells and Photodynamic Therapy in Zebrafish Embryos

Photodynamic therapy (PDT) and photochemical internalization (PCI) are two methods that use light to provoke cell death or disturbance of cellular membranes, respectively, via excitation of a photosensitizer and the formation of reactive oxygen species (ROS). In this context, two-photon excitation (TPE) is of high interest for PCI and/or PDT due to spatiotemporal resolution of two-photon light and deeper penetration of near-infrared light in biological tissues. Here, we report that Periodic Mesoporous Ionosilica Nanoparticles (PMINPs) containing porphyrin groups allow the complexation of pro-apoptotic siRNA. These nano-objects were incubated with MDA-MB-231 breast cancer cells, and TPE-PDT led to significant cell death. Finally, MDA-MB-231 breast cancer cells were pre-incubated with the nanoparticles and then injected in the pericardial cavity of zebrafish embryos. After 24 hours, the xenografts were irradiated with femtosecond pulsed laser and the size monitoring by imaging showed a decrease 24 h after irradiation. Pro-apoptotic siRNA was complexed with the nanoparticles and incubation with MDA-MB-231 cells did not lead to cancer cell death in dark conditions, but with two-photon irradiation, TPE-PCI was observed and a synergic effect between pro-apoptotic siRNA and TPE-PDT was noticed, leading to 90% of cancer cell death. Therefore, PMINPs represent an interesting system for nanomedicine applications.

Self-Immolative Photosensitizers for Self-Reported Cancer Phototheranostics

Photosensitizers to precise target and change fluorescence upon light illumination could accurately self-report where and when the photosensitizers work, enabling us to visualize the therapeutic process and precisely regulate treatment outcomes, which is the unremitting pursuit of precision and personalized medicine. Here, we report self-immolative photosensitizers by adopting a strategy of light-manipulated oxidative cleavage of C═C bonds that can generate a burst of reactive oxygen species, to cleave to release self-reported red-emitting products and trigger nonapoptotic cell oncosis. Strong electron-withdrawing groups are found to effectively suppress the C═C bond cleavage and phototoxicity via studying the structure-activity relationship, allowing us to elaborate NG1-NG5 that could temporarily inactivate the photosensitizer and quench the fluorescence by different glutathione (GSH)-responsive groups. Thereinto, NG2 with 2-cyano-4-nitrobenzene-1-sulfonyl group displays excellent GSH responsiveness than the other four. Surprisingly, NG2 shows better reactivity with GSH in weakly acidic condition, which inspires the application in weakly acidic tumor microenvironment where GSH elevates. To this end, we further synthesize NG-cRGD by anchoring integrin α_vβ₃ binding cyclic pentapeptide (cRGD) for tumor targeting. In A549 xenografted tumor mice, NG-cRGD successfully deprotects to restore near-infrared fluorescence because of elevated GSH in tumor site, which is subsequently cleaved upon light irradiation releasing red-emitting products to report photosensitizer working, while effectively ablating tumors via triggered oncosis. The advanced self-immolative organic photosensitizer may accelerate the development of self-reported phototheranostics in future precision oncology.

Photodynamic Antimicrobial Therapy Based on Conjugated Polymers

Pathogenic microorganisms have been a serious threat to human life and have become a public health problem of global concern. However, in the actual treatment there is a lack of efficient antimicrobial strategies which do not easily develop drug resistance; this can lead to inaccurate drug treatment that worsens the infection and even threatens life. With the emergence of a variety of drug-resistant bacteria and fungi, photodynamic therapy has gradually become one of the most promising treatment methods for drug-resistant bacteria infection; this is because it is controllable, non-invasive, and not prone to cause the development of drug resistance. Organic conjugated polymers that possess high fluorescence intensity, a large molar extinction coefficient, excellent light stability, an adjustable energy band, easy modification, good biocompatibility, and the ability to photosensitize oxygen to produce reactive oxygen species have been widely used in the fields of solar cells, highly sensitive detection systems, biological imaging, and anti-cancer and anti-microbial treatment. Photodynamic therapy is non-invasive and has high temporal and spatial resolution and is a highly effective antimicrobial treatment that does not easily induce drug resistance; it has also stimulated the scientific research enthusiasm of researchers and has become a research hotspot in the antimicrobial field. In this review, the photodynamic antibacterial applications of conjugated polymers with different structure types are summarized, and their development directions are considered.

One-Step Fabrication of Multifunctional PLGA-HMME-DTX@MnO2 Nanoparticles for Enhanced Chemo-Sonodynamic Antitumor Treatment

Background

Sonodynamic therapy (SDT) and its synergistic cancer therapy derivatives, such as combined chemotherapy-SDT (chemo-SDT), are promising approaches for tumor treatment. However, the main drawbacks restricting their applications are hypoxia in tumors and the reducing microenvironment or high glutathione (GSH) levels.

Methods

In this study, a hybrid metal MnO₂ was deposited onto nanoparticles fabricated using poly(lactic-co-glycolic acid) (PLGA), carrying docetaxel (DTX) and the sonosensitizer hematoporphyrin monomethyl ether (HMME) (PHD@MnO₂) via a one-step flash nanoprecipitation (FNP) method. Characterization and in vitro and in vivo experiments were conducted to explore the chemo-SDT effect of PHD@MnO₂ and evaluate the synergetic antitumor treatment of this nanosystem.

Results

When low-power ultrasound is applied, the acquired PHD@MnO₂, whether in solution or in MCF-7 cells, generated ROS more efficiently than other groups without MnO₂ or those treated via monotherapy. Specifically, GSH-depletion was observed when MnO₂ was introduced into the system. PHD@MnO₂ presented good biocompatibility and biosafety in vitro and in vivo. These results indicated that the PHD@MnO₂ nanoparticles overcame hypoxia in tumor tissue and suppressed the expression of hypoxia-inducible factor 1 alpha (HIF-1α), achieving enhanced chemo-SDT.

Conclusion

This study provides a paradigm that rationally engineered multifunctional metal-hybrid nanoparticles can serve as an effective platform for augmenting the antitumor therapeutic efficiency of chemo-SDT.

Recent Advances in Chitosan and its Derivatives in Cancer Treatment

Cancer has become a main public health issue globally. The conventional treatment measures for cancer include surgery, radiotherapy and chemotherapy. Among the various available treatment measures, chemotherapy is still one of the most important treatments for most cancer patients. However, chemotherapy for most cancers still faces many problems associated with a lot of adverse effects, which limit its therapeutic potency, low survival quality and discount cancer prognosis. In order to decrease these side effects and improve treatment effectiveness and patient’s compliance, more targeted treatments are needed. Sustainable and controlled deliveries of drugs with controllable toxicities are expected to address these hurdles. Chitosan is the second most abundant natural polysaccharide, which has excellent biocompatibility and notable antitumor activity. Its biodegradability, biocompatibility, biodistribution, nontoxicity and immunogenicity free have made chitosan become a widely used polymer in the pharmacology, especially in oncotherapy. Here, we make a brief review of the main achievements in chitosan and its derivatives in pharmacology with a special focus on their agents delivery applications, immunomodulation, signal pathway modulation and antitumor activity to highlight their role in cancer treatment. Despite a large number of successful studies, the commercialization of chitosan copolymers is still a big challenge. The further development of polymerization technology may satisfy the unmet medical needs.