Redox-Responsive Porphyrin-Based Polysilsesquioxane Nanoparticles for Photodynamic Therapy of Cancer Cells

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.

Autophagy Regulation Using Multimodal Chlorin e6-Loaded Polysilsesquioxane Nanoparticles to Improve Photodynamic Therapy

Photodynamic therapy (PDT) is a promising anticancer noninvasive technique that relies on the generation of reactive oxygen species (ROS). Unfortunately, PDT still has many limitations, including the resistance developed by cancer cells to the cytotoxic effect of ROS. Autophagy, which is a stress response mechanism, has been reported as a cellular pathway that reduces cell death following PDT. Recent studies have demonstrated that PDT in combination with other therapies can eliminate anticancer resistance. However, combination therapy is usually challenged by the differences in the pharmacokinetics of the drugs. Nanomaterials are excellent delivery systems for the efficient codelivery of two or more therapeutic agents. In this work, we report on the use of polysilsesquioxane (PSilQ) nanoparticles for the codelivery of chlorin-e6 (Ce6) and an autophagy inhibitor for early- or late-stage autophagy. Our results, obtained from a reactive oxygen species (ROS) generation assay and apoptosis and autophagy flux analyses, demonstrate that the reduced autophagy flux mediated by the combination approach afforded an increase in the phototherapeutic efficacy of Ce6-PSilQ nanoparticles. We envision that the promising results in the use of multimodal Ce6-PSilQ material as a codelivery system against cancer pave the way for its future application with other clinically relevant combinations.

Hematoporphyrin Is a Promising Sensitizer for Dual-Frequency Sono-photodynamic Therapy in Mice Breast Cancer

Background: The combination of sonodynamic and photodynamic therapy (SPDT) may be a new hopeful non-invasive method for cancer treatment, which incorporates a combination of low-intensity ultrasound, laser radiation, and a sensitizer agent. Objectives: This study aimed at evaluating the effects of hematoporphyrin (HP)-mediated SPDT (dual-frequency ultrasound and laser radiation) in the management of mice breast adenocarcinoma. Methods: One hundred and thirty-two female mice with implanted tumors were divided into 22 groups, including sham, laser, 4 groups of dual-frequency ultrasound/laser radiation, 8 groups of HP-mediated SPDT (2.5 and 5 mg/kg), and 8 groups of HP encapsulated in mesoporous silica nanoparticles (HP-MSNs)-mediated SPDT. The sensitizer was administered by intraperitoneal injection and after a 24-hour delay, tumor grafted mice were treated with a combination of dual-frequency ultrasound and laser light. The tumor growth factors were used to assess the treatment outcome. Results: The results indicated that HP or HP-MSNs-mediated SPDT had a delaying tumor growth effect. In the groups treated with dual-frequency ultrasound and laser radiation, the maximum tumor growth inhibition (TGI) ratio was 47.5%, while the maximum TGI ratio in the SPDT groups was 61.6%. The time of T2 and T5 in the case of HP-MSNs-mediated SPDT groups was increased compared with sham and that of HP-mediated SPDT groups (P < 0.05). The inhibition ratio on tumor growth increased in all SPDT groups at 12 days after the treatment. Analysis of experimental data demonstrates that this increase was not declined and persisted over 30 days of treatment. The results indicated that SPDT is effective in relative tumor volume when compared with the sham group (339.1 ± 161 and 1510.8 ± 160, respectively). HP or HP-MSNs-mediated SPDT groups had Grade I (low), while others had Grade III (high) malignancy in the histological study of mice breast adenocarcinoma. Conclusions: The results revealed that when sensitized by dual-frequency SPDT, hematoporphyrin (with and without MSNs), has a promising effect at delaying tumor growth on mice breast cancer. Therefore, it can be appreciated that careful selection of the sensitizer with SPDT will play an eminent role in the success of cancer therapies.

Use of Polyhedral Oligomeric Silsesquioxane (POSS) in Drug Delivery, Photodynamic Therapy and Bioimaging

Polyhedral oligomeric silsesquioxanes (POSS) have attracted considerable attention in the design of novel organic-inorganic hybrid materials with high performance capabilities. Features such as their well-defined nanoscale structure, chemical tunability, and biocompatibility make POSS an ideal building block to fabricate hybrid materials for biomedical applications. This review highlights recent advances in the application of POSS-based hybrid materials, with particular emphasis on drug delivery, photodynamic therapy and bioimaging. The design and synthesis of POSS-based materials is described, along with the current methods for controlling their chemical functionalization for biomedical applications. We summarize the advantages of using POSS for several drug delivery applications. We also describe the current progress on using POSS-based materials to improve photodynamic therapies. The use of POSS for delivery of contrast agents or as a passivating agent for nanoprobes is also summarized. We envision that POSS-based hybrid materials have great potential for a variety of biomedical applications including drug delivery, photodynamic therapy and bioimaging.

Light-Activated Protoporphyrin IX-Based Polysilsesquioxane Nanoparticles Induce Ferroptosis in Melanoma Cells

The use of nanoparticle-based materials to improve the efficacy of photodynamic therapy (PDT) to treat cancer has been a burgeoning field of research in recent years. Polysilsesquioxane (PSilQ) nanoparticles with remarkable features, such as high loading of photosensitizers, biodegradability, surface tunability, and biocompatibility, have been used for the treatment of cancer in vitro and in vivo using PDT. The PSilQ platform typically shows an enhanced PDT performance following a cell death mechanism similar to the parent photosensitizer. Ferroptosis is a new cell death mechanism recently associated with PDT that has not been investigated using PSilQ nanoparticles. Herein, we synthesized a protoporphyrin IX (PpIX)-based PSilQ platform (PpIX-PSilQ NPs) to study the cell death pathways, with special focus on ferroptosis, during PDT in vitro. Our data obtained from different assays that analyzed Annexin V binding, glutathione peroxidase activity, and lipid peroxidation demonstrate that the cell death in PDT using PpIX-PSilQ NPs is regulated by apoptosis and ferroptosis. These results can provide alternative approaches in designing PDT strategies to enhance therapeutic response in conditions stymied by apoptosis resistance.

Redox dual-stimuli responsive drug delivery systems for improving tumor-targeting ability and reducing adverse side effects

Cancer is a big challenge that has plagued the human beings for ages and one of the most effective treatments is chemotherapy. However, the low tumor-targeting ability limits the wide clinical application of chemotherapy. The microenvironment plays a critical role in many aspects of tumor genesis. It generates the tumor vasculature and it is highly implicated in the progression to metastasis. To maintain a suitable environment for tumor progression, there are special microenvironment in tumor cell, such as low pH, high level of glutathione (GSH) and reactive oxygen species (ROS), and more special enzymes, which is different to normal cell. Microenvironment-targeted therapy strategy could create new opportunities for therapeutic targeting. Compared to other targeting strategies, microenvironment-targeted therapy strategy will control the drug release into tumor cells more accurately. Redox responsive drug delivery systems (DDSs) are developed based on the high level of GSH in tumor cells. However, there are also GSH in normal cell though its level is lower. In order to control the release of drugs more accurately and reduce side effects, other drug release stimuli have been introduced to redox responsive DDSs. Under the synergistic reaction of two stimuli, redox dual-stimuli responsive DDSs will control the release of drugs more accurately and quickly and even increase the accumulation. This review summarizes strategies of redox dual-stimuli responsive DDSs such as pH, light, enzyme, ROS, and magnetic guide to delivery chemotherapeutic agents more accurately, aiming at providing new ideas for further promoting the drug release, enhancing tumor-targeting and improving anticancer effects. To better illustrate the redox dual-stimuli responsive DDS, preparations of carriers are also briefly described in the review.

Multimodal Polysilsesquioxane Nanoparticles for Combinatorial Therapy and Gene Delivery in Triple-Negative Breast Cancer

Multifunctional hybrid nanoparticles are being developed to carry a wide variety of therapeutic and imaging agents for multiple biomedical applications. Polysilsesquioxane (PSilQ) nanoparticles are a promising hybrid platform with numerous advantages to be used as a delivery system. In this report, we demonstrate the ability of a stimuli-responsive PSilQ-based platform to transport and deliver simultaneously protoporphyrin IX, curcumin, and RNA interference inducers inside human cells. This multimodal delivery system shows a synergistic performance for the combined phototherapy and chemotherapy of triple-negative breast cancer and can be used for efficient transfection of therapeutic nucleic acids. The current work represents the first report of using the PSilQ platform for the combined phototherapy and chemotherapy and gene delivery.

Degradability and Clearance of Silicon, Organosilica, Silsesquioxane, Silica Mixed Oxide, and Mesoporous Silica Nanoparticles

The biorelated degradability and clearance of siliceous nanomaterials have been questioned worldwide, since they are crucial prerequisites for the successful translation in clinics. Typically, the degradability and biocompatibility of mesoporous silica nanoparticles (MSNs) have been an ongoing discussion in research circles. The reason for such a concern is that approved pharmaceutical products must not accumulate in the human body, to prevent severe and unpredictable side-effects. Here, the biorelated degradability and clearance of silicon and silica nanoparticles (NPs) are comprehensively summarized. The influence of the size, morphology, surface area, pore size, and surface functional groups, to name a few, on the degradability of silicon and silica NPs is described. The noncovalent organic doping of silica and the covalent incorporation of either hydrolytically stable or redox- and enzymatically cleavable silsesquioxanes is then described for organosilica, bridged silsesquioxane (BS), and periodic mesoporous organosilica (PMO) NPs. Inorganically doped silica particles such as calcium-, iron-, manganese-, and zirconium-doped NPs, also have radically different hydrolytic stabilities. To conclude, the degradability and clearance timelines of various siliceous nanomaterials are compared and it is highlighted that researchers can select a specific nanomaterial in this large family according to the targeted applications and the required clearance kinetics.

Organosilica hybrid nanomaterials with a high organic content: syntheses and applications of silsesquioxanes

Organic-inorganic hybrid materials garner properties from their organic and inorganic matrices as well as synergistic features, and therefore have recently attracted much attention at the nanoscale. Non-porous organosilica hybrid nanomaterials with a high organic content such as silsesquioxanes (R-SiO_1.5, with R organic groups) and bridged silsesquioxanes (O_1.5Si-R-SiO_1.5) are especially attractive hybrids since they provide 20 to 80 weight percent of organic functional groups in addition to the known chemistry and stability of silica. In the organosilica family, silsesquioxanes (R-SiO_1.5) stand between silicas (SiO₂) and silicones (R₂SiO), and are variously called organosilicas, ormosil (organically-modified silica), polysilsesquioxanes and silica hybrids. Herein, we comprehensively review non-porous silsesquioxane and bridged silsesquioxane nanomaterials and their applications in nanomedicine, electro-optics, and catalysis.