Dual-step irradiation strategy to sequentially destroy singlet oxygen-responsive polymeric micelles and boost photodynamic cancer therapy

Wireless sequential dual light delivery for programmed PDT in vivo

Using photodynamic therapy (PDT) to treat deep-seated cancers is limited due to inefficient delivery of photosensitizers and low tissue penetration of light. Polymeric nanocarriers are widely used for photosensitizer delivery, while the self-quenching of the encapsulated photosensitizers would impair the PDT efficacy. Furthermore, the generated short-lived reactive oxygen spieces (ROS) can hardly diffuse out of nanocarriers, resulting in low PDT efficacy. Therefore, a smart nanocarrier system which can be degraded by light, followed by photosensitizer activation can potentially overcome these limitations and enhance the PDT efficacy. A light-sensitive polymer nanocarrier encapsulating photosensitizer (RB-M) was synthesized. An implantable wireless dual wavelength microLED device which delivers the two light wavelengths sequentially was developed to programmatically control the release and activation of the loaded photosensitizer. Two transmitter coils with matching resonant frequencies allow activation of the connected LEDs to emit different wavelengths independently. Optimal irradiation time, dose, and RB-M concentration were determined using an agent-based digital simulation method. In vitro and in vivo validation experiments in an orthotopic rat liver hepatocellular carcinoma disease model confirmed that the nanocarrier rupture and sequential low dose light irradiation strategy resulted in successful PDT at reduced photosensitizer and irradiation dose, which is a clinically significant event that enhances treatment safety.

Hypoxia-Responsive Tetrameric Supramolecular Polypeptide Nanoprodrugs for Combination Therapy

Despite the intense progress of photodynamic and chemotherapy, however, they cannot prevent solid tumor invasion, metastasis, and relapse, along with inferior efficacy and severe side effects. The hypoxia-responsive nanoprodrugs integrating photodynamic functions are highly sought to address the above-mentioned problems and overcome the tumor hypoxia-reduced efficacy. Herein, a hypoxia-responsive tetrameric supramolecular polypeptide nanoprodrug (SPN-TAPP-PCB4) is constructed from the self-assembly of tetrameric porphyrin-central poly(l-lysine-azobenzene-chlorambucil) (TAPP-(PLL-Azo-CB)4) and an anionic water-soluble [2]biphenyl-extended-pillar[6]arene (AWBpP6) via the synergy of hydrophobic, π-π stacking, and host-guest interactions. Upon laser irradiation, the central TAPP can convert oxygen to generate single oxygen (1 O2 ) to kill tumor cells. Furthermore, under the acidic and PDT-aggravated hypoxia tumor cell microenvironment, SPN-TAPP-PCB4 is rapidly disassembled, and then efficiently releases activated CB through the hypoxic-responsive cleavage of azobenzene linkages. Both in vitro and in vivo biological studies showcase synergistic cancer-killing actions between photodynamic therapy (PDT) and chemotherapy (CT) with negligible toxicity. Consequently, this supramolecular polypeptide nanoprodrug offers an effective strategy to design a hypoxia-responsive nanoprodrug for a potential combo PDT-CT transition.

Dextran-based micelles for combinational chemo-photodynamic therapy of tumors via in vivo chemiluminescence

Natural polysaccharides, represented by dextran, chitosan, and hyaluronic acid, are widely approved for use as pharmaceutical excipients and are important carrier materials for the design of advanced drug delivery systems, particularly in the field of anticancer drug delivery. The combination of stimuli-activable prodrug based chemotherapy and photodynamic therapy (PDT) has attracted increasing attention. Recent studies have verified the effectiveness of this strategy in the treatment of multiple aggressive cancers. However, in such combination, the stimuli-responsive chemotherapy and PDT have their own problems that need to be overcome. The uneven distribution of endogenous stimuli within tumor tissues makes it difficult for prodrug to be completely activated. And the inadequate tissue penetration depth of external light results in low efficiency of PDT. Aiming at these two bottlenecks, we designed a biocompatible dextran based - multi-component nanomedicine (PCL-NPs) that integrate a chemiluminescence agent luminol, a photosensitizer chlorine e6 (Ce6), and a reactive oxygen species (ROS)-activable thioketal-based paclitaxel (PTX) prodrug. The presence of overexpressed hydrogen peroxide (H2O2) inside tumor oxidizes the luminol moiety to generate in-situ light for PDT through chemiluminescence resonance energy transfer (CRET). The singlet oxygen (1O2) produced in this process not only directly kills tumor cells but also amplifies oxidative stress to accelerate the activation of PTX prodrug. We propose that the PCL-NPs have great therapeutic potential by simultaneously enhancing chemotherapy and PDT in a combination therapy.

Anatase TiO2-x and zwitterionic porphyrin polymer-based nanocomposite for enhanced cancer photodynamic therapy

Photodynamic therapy has been used as a treatment option for cancer; however, the existing TiO2 photosensitizer does not have the ability to specifically target cancer cells. This lack of selectivity reduces its effectiveness in overcoming cancer resistance. To improve photodynamic therapy outcomes, an innovative solution is proposed. In this study, we report on the compounding of a zwitterionic covalent organic polymer (COP) with a TiO2 photosensitizer for the first time. The aim is to overcome cancer cellular resistance. A one-pot synthetic strategy, which includes the construction of a porphyrin-based COP has been employed. This strategy has also been applied to the rapid preparation of anatase defective TiO2 (TiO2-x). To improve the hydrophilic and antifouling properties of the polymer, zwitterion L-cysteine has been conjugated with a porphyrin-based COP using a thiol-ene "click chemistry" reaction. The novel zwitterionic porphyrin-based COP has the ability to trigger biodegradation under the acid microenvironment due to the presence of acid-sensitive β-thioether esters. When combined with TiO2-x, the resultant nanocomposite produces an enhanced photodynamic therapy effect for drug-resistant cancer cells under NIR laser irradiation. This is due to the strong mutual sensitization of zwitterionic porphyrin-based COP and TiO2-x. Importantly, the nanocomposite delivery system exhibits excellent cytocompatibility in the dark and has the potential to improve the accuracy of cancer diagnosis through fluorescence imaging. The results of this study demonstrate the potential application of this alternative nanocomposite delivery system for remote-controllable photodynamic therapy of tumors.

Dual-Ligand Synergistic Targeting Anti-Tumor Nanoplatforms with Cascade-Responsive Drug Release

Dual-ligand targeting drug delivery nanoplatforms are considered a promising tool for enhancing the specificity of chemotherapy. However, serious off-target delivery has been observed in current dual-ligand targeting nanoplatforms, as each ligand can independently recognize receptors on the cell membrane surface and guide drug nanocarriers to different cells. To overcome this barrier, a dual-ligand synergistic targeting (DLST) nanoplatform is developed, which can guide chemotherapy treatment specifically to cancer cells simultaneously overexpressing two receptors. This nanoplatform consists of a singlet oxygen (¹O₂) photosensitizer-loaded nanocarrier and a drug-loaded nanocarrier with ¹O₂ responsiveness, which were, respectively, decorated with a pair of complementary DNA sequences and two different ligands. For cancer cells overexpressing both receptors, two nanocarriers can be internalized in larger quantities to cause DNA hybridization-induced nanocarrier aggregation, which further activates ¹O₂-triggered drug release under light irradiation. For cells overexpressing a single receptor, only one type of nanocarrier can be internalized in a large quantity, leading to blocked drug release due to the ultrashort action radius of ¹O₂. In vivo evaluation showed this DLST nanoplatform displayed highly specific tumor treatment with minimized long-term toxicity. This is a highly efficient drug delivery system for DLST chemotherapy, holding great potential for clinical applications.

Nanoparticle-mediated synergistic anticancer effect of ferroptosis and photodynamic therapy: Novel insights and perspectives

Current antitumor monotherapy has many limitations, highlighting the need for novel synergistic anticancer strategies. Ferroptosis is an iron-dependent form of nonapoptotic cell death that plays a pivotal regulatory role in tumorigenesis and treatment. Photodynamic therapy (PDT) causes irreversible chemical damage to target lesions and is widely used in antitumor therapy. However, PDT's effectiveness is usually hindered by several obstacles, such as hypoxia, excess glutathione (GSH), and tumor resistance. Ferroptosis improves the anticancer efficacy of PDT by increasing oxygen and reactive oxygen species (ROS) or reducing GSH levels, and PDT also enhances ferroptosis induction due to the ROS effect in the tumor microenvironment (TME). Strategies based on nanoparticles (NPs) can subtly exploit the potential synergy of ferroptosis and PDT. This review explores recent advances and current challenges in the landscape of the underlying mechanisms regulating ferroptosis and PDT, as well as nano delivery system-mediated synergistic anticancer activity. These include polymers, biomimetic materials, metal organic frameworks (MOFs), inorganics, and carrier-free NPs. Finally, we highlight future perspectives of this novel emerging paradigm in targeted cancer therapies.

Dual gatekeepers-modified mesoporous organic silica nanoparticles for synergistic photothermal-chemotherapy of breast cancer

HYPOTHESIS

Construction of dual gatekeepers-functionalized mesoporous organic silica nanoparticles (MONs) with both physical and chemical mechanisms for modulated drug delivery properties provides one solution to the extracellular stability vs. intracellular high therapeutic efficiency of MONs that hold great potential for clinical translations.

EXPERIMENTS

We reported herein facile construction of diselenium-bridged MONs decorated with dual gatekeepers, i.e., azobenzene (Azo)/polydopamine (PDA) for both physical and chemical modulated drug delivery properties. Specifically, Azo can act as a physical barrier to block DOX in the mesoporous structure of MONs for extracellular safe encapsulation. The PDA outer corona serves not only as a chemical barrier with acidic pH-modulated permeability for double insurance of minimized DOX leakage in the extracellular blood circulation but also for inducing a PTT effect for synergistic PTT and chemotherapy of breast cancer.

FINDINGS

An optimized formulation, DOX@(MONs-Azo3)@PDA resulted in approximately 1.5 and 2.4 fold lower IC50 values than DOX@(MONs-Azo3) and (MONs-Azo3)@PDA controls in MCF-7 cells, respectively, and further mediated complete tumor eradication in 4T1 tumor-bearing BALB/c mice with insignificant systematic toxicity due to the synergistic PTT and chemotherapy with enhanced therapeutic efficiency.

ROS-Responsive Self-activatable Photosensitizing Agent for Photodynamic-Immunotherapy of cancer

Photodynamic therapy (PDT), as a non-invasive and spatiotemporally controllable modality, exhibits great potential in cancer treatment. However, the efficiency of reactive oxygen species (ROS) production was restricted to the hydrophobic characteristics and aggregation-caused quenching (ACQ) of photosensitizers. Herein, we designed a ROS self-activatable nano system (denoted as PTKPa) based on poly(thioketal) conjugated with photosensitizers (PSs) pheophorbide A (Ppa) on the polymer side chains for suppressing ACQ and enhancing PDT. The process of self-activation is that ROS, which is derived from laser irradiated PTKPa, as an activating agent accelerates poly(thioketal) cleavage with the release of Ppa from PTKPa. This in turn generates abundant ROS, accelerates degradation of the remaining PTKPa and amplifies the efficacy of PDT with more tremendous ROS generated. Moreover, these abundant ROS can amplify PDT-induced oxidative stress, cause irreversible damage to tumor cells and achieve immunogenic cell death (ICD), thereby boosting the efficacy of photodynamic-immunotherapy. These findings provide new insights into ROS self-activatable strategy for enhancing cancer photodynamic- immunotherapy. STATEMENT OF SIGNIFICANCE: This work described an approach to utilize ROS-responsive self-activatable poly(thioketal) conjugated with pheophorbide A (Ppa) for suppressing aggregation-caused quenching (ACQ) and enhancing photodynamic-immunotherapy. The ROS, generated from the conjugated Ppa upon 660nm laser irradiation, as a triggering agent which initiates the release of Ppa with poly(thioketal) degradation. That in turn generates abundant ROS and facilitates degradation of the remaining PTKPa, resulting in oxidative stress to tumor cells and achieving immunogenic cell death (ICD). This work provides a promising solution to improve tumor photodynamic therapeutic effects.

Low-intensity focused ultrasound targeted microbubble destruction reduces tumor blood supply and sensitizes anti-PD-L1 immunotherapy

Immune checkpoint blockade (ICB) typified by anti-PD-1/PD-L1 antibodies as a revolutionary treatment for solid malignancies has been limited to a subset of patients due to poor immunogenicity and inadequate T cell infiltration. Unfortunately, no effective strategies combined with ICB therapy are available to overcome low therapeutic efficiency and severe side effects. Ultrasound-targeted microbubble destruction (UTMD) is an effective and safe technique holding the promise to decrease tumor blood perfusion and activate anti-tumor immune response based on the cavitation effect. Herein, we demonstrated a novel combinatorial therapeutic modality combining low-intensity focused ultrasound-targeted microbubble destruction (LIFU-TMD) with PD-L1 blockade. LIFU-TMD caused the rupture of abnormal blood vessels to deplete tumor blood perfusion and induced the tumor microenvironment (TME) transformation to sensitize anti-PD-L1 immunotherapy, which markedly inhibited 4T1 breast cancer's growth in mice. We discovered immunogenic cell death (ICD) in a portion of cells induced by the cavitation effect from LIFU-TMD, characterized by the increased expression of calreticulin (CRT) on the tumor cell surface. Additionally, flow cytometry revealed substantially higher levels of dendritic cells (DCs) and CD8⁺ T cells in draining lymph nodes and tumor tissue, as induced by pro-inflammatory molecules like IL-12 and TNF-α. These suggest that LIFU-TMD as a simple, effective, and safe treatment option provides a clinically translatable strategy for enhancing ICB therapy.

Ferrocene-Based Polymeric Nanoparticles Carrying Doxorubicin for Oncotherapeutic Combination of Chemotherapy and Ferroptosis

Mono-chemotherapy has significant side effects and unsatisfactory efficacy, limiting its clinical application. Therefore, a combination of multiple treatments is becoming more common in oncotherapy. Chemotherapy combined with the induction of ferroptosis is a potential new oncotherapy. Furthermore, polymeric nanoparticles (NPs) can improve the antitumor efficacy and decrease the toxicity of drugs. Herein, a polymeric NP, mPEG-b-PPLGFc@Dox, is synthesized to decrease the toxicity of doxorubicin (Dox) and enhance the efficacy of chemotherapy by combining it with the induction of ferroptosis. First, mPEG-b-PPLGFc@Dox is oxidized by endogenous H₂ O₂ and releases Dox, which leads to an increase of H₂ O₂ by breaking the redox balance. The Fe(II) group of ferrocene converts H₂ O₂ into ·OH, inducing subsequent ferroptosis. Furthermore, glutathione peroxidase 4, a biomarker of ferroptosis, is suppressed and the lipid peroxidation level is elevated in cells incubated with mPEG-b-PPLGFc@Dox compared to those treated with Dox alone, indicating ferroptosis induction by mPEG-b-PPLGFc@Dox. In vivo, the antitumor efficacy of mPEG-b-PPLGFc@Dox is higher than that of free Dox. Moreover, the loss of body weight in mice treated mPEG-b-PPLGFc@Dox is lower than in those treated with free Dox, indicating that mPEG-b-PPLGFc@Dox is less toxic than free Dox. In conclusion, mPEG-b-PPLGFc@Dox not only has higher antitumor efficacy but it reduces the damage to normal tissue.

Progress of Nanomaterials in Photodynamic Therapy Against Tumor

Photodynamic therapy (PDT) is an advanced therapeutic strategy with light-triggered, minimally invasive, high spatiotemporal selective and low systemic toxicity properties, which has been widely used in the clinical treatment of many solid tumors in recent years. Any strategies that improve the three elements of PDT (light, oxygen, and photosensitizers) can improve the efficacy of PDT. However, traditional PDT is confronted some challenges of poor solubility of photosensitizers and tumor suppressive microenvironment. To overcome the related obstacles of PDT, various strategies have been investigated in terms of improving photosensitizers (PSs) delivery, penetration of excitation light sources, and hypoxic tumor microenvironment. In addition, compared with a single treatment mode, the synergistic treatment of multiple treatment modalities such as photothermal therapy, chemotherapy, and radiation therapy can improve the efficacy of PDT. This review summarizes recent advances in nanomaterials, including metal nanoparticles, liposomes, hydrogels and polymers, to enhance the efficiency of PDT against malignant tumor.

A Co-delivery System Based on a Dimeric Prodrug and Star-Shaped Polymeric Prodrug Micelles for Drug Delivery

Chemotherapy is one of the commonly used therapies for the treatment of malignant tumors. Insufficient drug-loading capacity is the major challenge for polymeric micelle-based drug delivery systems of chemotherapy. Here, the redox-responsive star-shaped polymeric prodrug (PSSP) and the dimeric prodrug of paclitaxel (PTX) were prepared. Then the dimeric prodrug of PTX (diPTX, diP) was loaded into the core of the star-shaped polymeric prodrug micelles of PSSP by hydrophobic interaction forming the redox-responsive prodrug micelles of diPTX@PSSP for intracellular drug release in tumor cells. The hydrodynamic diameter of diPTX@PSSP nanoparticles was 114.3 nm ± 2.1 (PDI = 0.219 ± 0.016), and the micelles had long-term colloidal stability and the drug-loading content (DLC) of diPTX and PTX is 16.7 and 46.9%, respectively. The prepared micelles could broke under the reductive microenvironment within tumor cells, as a result, the dimeric prodrug of diP and polymeric prodrug micelles of PSSP were rapidly disassembled, leading to the rapid release of intracellular drugs. In vitro release studies showed that under the condition of reduced glutathione (GSH) (10 mM), the release of PTX was significantly accelerated with approximately 86.6% released within 21 h, and the released PTX in cytoplasm could promote the disintegration of microtubules and induce cell apoptosis. These results indicated that the new type of this reduction-sensitive nanodrug delivery system based on dimeric prodrug@polymeric prodrug micelles would be a promising technology in chemotherapy.

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.