Design of Tumor Microenvironment-Responsive Drug-Drug Micelle for Cancer Radiochemotherapy

Carrageenan-ferrocene-eicosapentaenoic acid composite hydrogel induce ferroptosis and apoptosis for anti-tumor recurrence and metastasis

The immune-suppressive microenvironment of solid tumors is a key factor limiting the effectiveness of immunotherapy, which seriously threatens human life and health. Ferroptosis and apoptosis are key cell-death pathways implicated in cancers, which can synergistically activate tumor immune responses. Here, we developed a multifunctional composite hydrogel (CE-Fc-Gel) based on the self-assembly of poloxamer 407, cystamine-linked ιota-carrageenan (CA)-eicosapentaenoic acid (EPA), and ferrocene (Fc). CE-Fc-Gel improved targeting in tumor microenvironment due to its disulfide bonds. Moreover, CE-Fc-Gel promoted lipid peroxidation, enhanced reactive oxygen species (ROS) production, and decreased glutathione peroxidase 4 (GPX4), inducing ferroptosis by the synergistic effect of Fc and EPA. CE-Fc-Gel induced apoptosis and immunogenic cell death (ICD), thereby promoting dendritic cells (DCs) maturation and T cell infiltration. As a result, CE-Fc-Gel significantly inhibited primary and metastatic tumors in vivo. Our findings provide a novel strategy for enhancing tumor immunotherapy by combining apoptosis, ferroptosis, and ICD.

Smart Nanoplatforms Responding to the Tumor Microenvironment for Precise Drug Delivery in Cancer Therapy

The tumor microenvironment (TME) is a complex and dynamic entity, comprising stromal cells, immune cells, blood vessels and extracellular matrix, which is intimately associated with the occurrence and development of cancers, as well as their therapy. Utilizing the shared characteristics of tumors, such as an acidic environment, enzymes and hypoxia, researchers have developed a promising cancer therapy strategy known as responsive release of nano-loaded drugs, specifically targeted at tumor tissues or cells. In this comprehensive review, we provide an in-depth overview of the current fundamentals and state-of-the-art intelligent strategies of TME-responsive nanoplatforms, which include acidic pH, high GSH levels, high-level adenosine triphosphate, overexpressed enzymes, hypoxia and reductive environment. Additionally, we showcase the latest advancements in TME-responsive nanoparticles. In conclusion, we thoroughly examine the immediate challenges and prospects of TME-responsive nanopharmaceuticals, with the expectation that the progress of these targeted nanoformulations will enable the exploitation, overcoming or modulation of the TME, ultimately leading to significantly more effective cancer therapy.

Polysaccharide-based nanocarriers for efficient transvascular drug delivery

Polysaccharide-based nanocarriers (PBNs) are the focus of extensive investigation because of their biocompatibility, low cost, wide availability, and chemical versatility, which allow a wide range of anticancer agents to be loaded within the nanocarriers. Similar to other nanocarriers, most PBNs are designed to extravasate out of tumor vessels, depending on the enhanced permeability and retention (EPR) effect. However, the EPR effect is compromised in some tumors due to the heterogeneity of tumor structures. Transvascular transport efficacy is decreased by complex blood vessels and condensed tumor stroma. The limited extravasation impedes efficient drug delivery into tumor parenchyma, and thus affects the subsequent tumor accumulation, which hinders the therapeutic effect of PBNs. Therefore, overcoming the biological barriers that restrict extravasation from tumor vessels is of great importance in PBN design. Many strategies have been developed to enhance the EPR effect that involve nanocarrier property regulation and tumor structure remodeling. Moreover, some researchers have proposed active transcytosis pathways that are complementary to the paracellular EPR effect to increase the transvascular extravasation efficiency of PBNs. In this review, we summarize the recent advances in the design of PBNs with enhanced transvascular transport to enable optimization of PBNs in the extravasation of the drug delivery process. We also discuss the obstacles and challenges that need to be addressed to clarify the transendothemial mechanism of PBNs and the potential interactions between extravasation and other drug delivery steps.

Prodrug Nanosensitizer Overcomes the Radiation Resistance of Hypoxic Tumor

Clinical radiation therapy (RT) is often hindered by the low radiation energy absorption coefficient and the hypoxic features of tumor tissues. Among the tremendous efforts devoted to overcoming the barriers to efficient RT, the application of hypoxic radiosensitizers and cell-cycle-specific chemotherapeutics has shown great potential. However, their effectiveness is often compromised by their limited bioavailability, especially in the hypoxic region, which plays a major role in radioresistance. Herein, to simultaneously improve the delivery efficacy of both hypoxic radiosensitizer and cell-cycle-specific drug, a gambogic acid (GA) metronidazole (MN) prodrug (GM) was designed and synthesized based on GA, a naturally occurring chemotherapeutic and multiple pathway inhibitor, and MN, a typical hypoxic radiosensitizer. In combination with MN-containing block copolymers, the prodrug nanosensitizer (NS) of GM was obtained. Owing to the bioreduction of MN, the as-designed prodrug could be efficiently delivered to hypoxic cells and act on mitochondria to cause the accumulation of reactive oxygen species. The strong G₂/M phase arrest caused by the prodrug NS could further sensitize treated cells to external radiation under hypoxic conditions by increasing DNA damage and delaying DNA repair. After coadministration of the NS with a well-established tissue-penetrating peptide, efficient tumor accumulation, deep tumor penetration, and highly potent chemoradiotherapy could be achieved.

Hypoxia-responsive nanomaterials for tumor imaging and therapy

Hypoxia is an important component of tumor microenvironment and plays a pivotal role in cancer progression. With the distinctive physiochemical properties and biological effects, various nanoparticles targeting hypoxia had raised great interest in cancer imaging, drug delivery, and gene therapy during the last decade. In the current review, we provided a comprehensive view on the latest progress of novel stimuli-responsive nanomaterials targeting hypoxia-tumor microenvironment (TME), and their applications in cancer diagnosis and therapy. Future prospect and challenges of nanomaterials are also discussed.

A hypoxia-dissociable siRNA nanoplatform for synergistically enhanced chemo-radiotherapy of glioblastoma

Glioblastoma (GBM), as the most aggressive adult brain tumor, seriously threatened people's lives with a low survival time. Standard postoperative treatment, chemotherapy combined with radiotherapy (RT), was the major therapeutic strategy for GBM. However, this therapeutic efficacy was hindered by chemoradiotherapy resistance of GBM. Herein, to sensitize temozolomide (TMZ)-based chemotherapy and RT, a hypoxia-radiosensitive nanoparticle for co-delivering TMZ and siMGMT (RDPP(Met)/TMZ/siMGMT) was synthesized in this study. Our nanoparticle could effectively release the encapsulated alkylating agent (TMZ) and small interfering O6-methylguanine-DNA-methyltransferase RNA (siMGMT) in the hypoxic GBM. DNA-damage repair was effectively inhibited by down-regulating MGMT expression and activating cell apoptosis, which obviously enhanced the sensitivity of TMZ as well as RT. In vitro and in vivo experiments showed that RDPP(Met)/TMZ/siMGMT could efficiently penetrate the blood-brain barrier (BBB), accurately target GBM cells and effectively inhibit GBM proliferation. Compared with traditional TMZ combined with RT, RDPP(Met)/TMZ/siMGMT remarkably improved the survival time of orthotopic GBM-bearing mice, which demonstrated that our nanoplatform was an efficient combinatorial GBM therapy.

Peptides to Overcome the Limitations of Current Anticancer and Antimicrobial Nanotherapies

Biomedical research devotes a huge effort to the development of efficient non-viral nanovectors (NV) to improve the effectiveness of standard therapies. NVs should be stable, sustainable and biocompatible and enable controlled and targeted delivery of drugs. With the aim to foster the advancements of such devices, this review reports some recent results applicable to treat two types of pathologies, cancer and microbial infections, aiming to provide guidance in the overall design of personalized nanomedicines and highlight the key role played by peptides in this field. Additionally, future challenges and potential perspectives are illustrated, in the hope of accelerating the translational advances of nanomedicine.

Nanomaterials Based on Functional Polymers for Sensitizing Cancer Radiotherapy

Despite being the mainstay treatment for many types of cancer in clinic, radiotherapy is undertaking great challenges in overcoming a series of limitations. Radiosensitizers are promising agents capable of depositing irradiation energy and generating free radicals to enhance the radiosensitivity of tumor cells. Combining radiosensitizers with functional polymer-based nanomaterials holds great potential to improve biodistribution, circulation time, and stability in vivo. The derived polymeric nano-radiosensitizers can significantly improve the efficiency of tumor targeting and radiotherapy, and reduce the side effect to healthy tissues. In this review, we provide an overview of functional polymer-based nanomaterials for radiosensitization in recent years. Particular emphases are given to the action mechanisms, drug loading methods, targeting efficiencies, the impact on therapeutic effects and biocompatibility of various radiosensitizing polymers, which are classified as polymeric micelles, dendrimers, polymeric nanospheres, nanoscale coordination polymers, polymersomes, and nanogels. The challenges and outlooks of polymeric nano-radiosensitizers are also discussed. This article is protected by copyright. All rights reserved.

Development of nanotechnology-mediated precision radiotherapy for anti-metastasis and radioprotection

Radiotherapy (RT), including external beam RT and internal radiation therapy, uses high-energy ionizing radiation to kill tumor cells.

Multi-functional polymeric micelles for chemotherapy-based combined cancer therapy

Currently, the therapeutic performance of traditional mono-chemotherapy on cancers remains unsatisfactory because of the tumor heterogeneity and multidrug resistance. In light of intricate tumor structures and distinct tumor microenvironments (TMEs), combinational therapeutic strategies with multiple anticancer drugs from different mechanisms can synergistically optimize the outcomes and concomitantly minimize the adverse effects during the therapy process. Extensive research on polymeric micelles (PMs) for biomedical applications has revealed the growing importance of nanomedicines for cancer therapy in the recent decade. Starting from traditional simple delivery systems, PMs have been extended to multi-faceted therapeutic strategies. Here we review and summarize the most recent advances in combinational therapy based on multifunctional PMs including a combination of multiple anticancer drugs, chemo-gene therapy, chemo-phototherapy and chemo-immunotherapy. The design approaches, action mechanisms and therapeutic applications of these nanodrugs are summarized. In addition, we highlight the opportunities and potential challenges associated with this promising field, which will provide new guidelines for advanced combinational cancer chemotherapy.

In Vivo Delivery of siRNAs Targeting EGFR and BRD4 Expression by Peptide-Modified Redox Responsive PEG-PEI Nanoparticles for the Treatment of Triple-Negative Breast Cancer

The study aims to investigate the in vivo distribution, antitumor effect, and safety of cell membrane-penetrating peptide-modified disulfide bond copolymer nanoparticles loaded with small-interfering RNA (siRNA) targeting epidermal growth factor receptor (EGFR) and bromodomain-containing protein 4 (BRD4) in triple-negative breast cancer (TNBC). Polyethylene glycol disulfide bond-linked polyethylenimine (PEG-SS-PEI) was modified with peptides GALA and CREKA and used as vectors to prepare siRNA nanoparticles. The GALA- and CREKA-modified PEG-SS-PEI nanoparticles (GC-NPs) were prepared by mixing siEGFR and siBRD4 (1:1) with GALA-PEG-SS-PEI and CREKA-PEG-SS-PEI (1:1) in an aqueous solution at an N/P ratio of 30:1. Nanoparticles loaded with scrambled siRNA were prepared with the same method. The gene silencing effect on EGFR and BRD4 in vitro was evaluated by Western blotting analysis. TNBC xenograft models were established by subcutaneous injection of MDA-MB-231 cells into female nude mice. At 1, 3, 6, 12, and 24 h after administration of five formulations of Cy5-siRNA (133 μg/10 g) via the tail vein, the mice were observed and imaged for a biodistribution study using an in vivo imaging system. In the pharmacodynamics experiment, tumor-bearing mice were treated with respective siRNA preparations at a dose of 133 μg/10 g for 18 days, and the body weight and tumor size were recorded every other day. The protein expression levels of EGFR, p-EGFR, PI3K, p-PI3K, Akt, p-Akt, BRD4, and c-Myc were determined using Western blotting analysis. Hematological and serum biochemical parameters, organ indices, and HE staining results for the heart, liver, spleen, lung, and kidney were analyzed to evaluate the safety of the nanoparticles. GC-NPs loaded with siEGFR and siBRD4 significantly inhibited the expression of EGFR and BRD4 in vitro. The strongest fluorescence signals were observed in the GC-NP group, especially in tumors, indicating the excellent tumor-targeted delivery of GC-NPs we constructed. Tumor growth was significantly inhibited in the GC-NP-treated group, and the expression of EGFR, p-EGFR, PI3K, p-PI3K, Akt, p-Akt, BRD4, and c-Myc in the tumors decreased by 71%, 68%, 61%, 68%, 48%, 58%, 59%, and 74% compared to the control group, respectively. There was no significant change in hematological parameters, biochemical indices, or tissue morphology in GC-NP-treated mice. SiRNA cotargeting EGFR and BRD4 delivered by GALA- and CREKA-modified PEG-SS-PEI had favorable antitumor effects in vivo toward TNBC with tumor-targeting efficacy and good biocompatibility.

Advances of Nanomedicine in Radiotherapy

Radiotherapy (RT) remains one of the current main treatment strategies for many types of cancer. However, how to improve RT efficiency while reducing its side effects is still a large challenge to be overcome. Advancements in nanomedicine have provided many effective approaches for radiosensitization. Metal nanoparticles (NPs) such as platinum-based or hafnium-based NPs are proved to be ideal radiosensitizers because of their unique physicochemical properties and high X-ray absorption efficiency. With nanoparticles, such as liposomes, bovine serum albumin, and polymers, the radiosensitizing drugs can be promoted to reach the tumor sites, thereby enhancing anti-tumor responses. Nowadays, the combination of some NPs and RT have been applied to clinical treatment for many types of cancer, including breast cancer. Here, as well as reviewing recent studies on radiotherapy combined with inorganic, organic, and biomimetic nanomaterials for oncology, we analyzed the underlying mechanisms of NPs radiosensitization, which may contribute to exploring new directions for the clinical translation of nanoparticle-based radiosensitizers.

Emerging strategies based on nanomaterials for ionizing radiation-optimized drug treatment of cancer

Drug-radiotherapy is a common and effective combinational treatment for cancer. This study aimed to explore the ionizing radiation-optimized drug treatment based on nanomaterials so as to improve the synergistic efficacy of drug-radiotherapy against cancer and limit the adverse effect on healthy organs. In this review, these emerging strategies were divided into four parts. First, the delivery of the drug-loaded nanoparticles was optimized owing to the strengthened passive targeting process, active targeting process, and cell targeting process of nanoparticles after ionizing radiation exposure. Second, nanomaterials were designed to respond to the ionizing radiation, thus leading to the release of the loading drugs controllably. Third, radiation-activated pro-drugs were loaded onto nanoparticles for radiation-triggered drug therapy. In particular, nontoxic nanoparticles with radiosensitization capability and innocuous radio-dynamic contrast agents can be considered as radiation-activated drugs, which were discussed in this review. Fourth, according to the various synergetic mechanisms, radiotherapy could improve the drug response of cancer, obtaining optimized drug-radiotherapy. Finally, relative suggestions were provided to further optimize these aforementioned strategies. Therefore, a novel topic was selected and the emerging strategies in this region were discussed, aiming to stimulate the inspiration for the development of ionizing radiation-optimized drug treatment based on nanomaterials.

Is hyaluronic acid the perfect excipient for the pharmaceutical need?

Hyaluronic acid has become an interesting and important polymer as an excipient for pharmaceutical products due to its beneficial properties, like solubility, biocompatibility and biodegradation. To improve the properties of hyaluronic acid, different possibilities for chemical modifications are presented, and the opportunities as novel systems for drug delivery are discussed. This review gives an overview over the production of hyaluronic acid, the possibilities of its chemical modification and the current state of in vitro and in vivo research. Furthermore, market approved and commercially available products are reviewed and derivatives undergoing clinical trials and applying for market approval are shown. In particular, hyaluronic acid has been studied for different administrations in rheumatology, ophthalmology, local anesthetics, cancer treatment and bioengineering of tissues. The present work concludes with perspectives for future administration of pharmaceuticals based on hyaluronic acid.

Tumor Microenvironment Sensitive Nanocarriers for Bioimaging and Therapeutics

The tumor microenvironment (TME), which is composed of cancer cells, stromal cells, immune cells, and extracellular matrices, plays an important role in tumor growth and progression. Thus, targeting the TME using a well-designed nano-drug delivery system is emerging as a promising strategy for the treatment of solid tumors. Compared to normal tissues, the TME presents several distinguishable physiological features such as mildly acidic pH, hypoxia, high level of reactive oxygen species, and overexpression of specific enzymes, that are exploited as stimuli to induce specific changes in the nanocarrier structures, and thereby facilitates target-specific delivery of imaging or chemotherapeutic agents for the early diagnosis or effective treatment, respectively. Recently, smart nanocarriers that respond to more than one stimulus in the TME have also been designed to elicit a more desirable spatiotemporally controlled drug release. This review highlights the recent progress in TME-sensitive nanocarriers designed for more efficient tumor therapy and imaging. In particular, the design strategies, challenges, and critical considerations involved in the fabrication of TME-sensitive nanocarriers, along with their in vitro and in vivo evaluations are discussed.

Carrier-free nanodrugs for safe and effective cancer treatment

Clinical applications of many anti-cancer drugs are restricted due to their hydrophobic nature, requiring use of harmful organic solvents for administration, and poor selectivity and pharmacokinetics resulting in off-target toxicity and inefficient therapies. A wide variety of carrier-based nanoparticles have been developed to tackle these issues, but such strategies often fail to encapsulate drug efficiently and require significant amounts of inorganic and/or organic nanocarriers which may cause toxicity problems in the long term. Preparation of nano-formulations for the delivery of water insoluble drugs without using carriers is thus desired, requiring elegantly designed strategies for products with high quality, stability and performance. These strategies include simple self-assembly or involving chemical modifications via coupling drugs together or conjugating them with various functional molecules such as lipids, carbohydrates and photosensitizers. During nanodrugs synthesis, insertion of redox-responsive linkers and tumor targeting ligands endows them with additional characteristics like on-target delivery, and conjugation with immunotherapeutic reagents enhances immune response alongside therapeutic efficacy. This review aims to summarize the methods of making carrier-free nanodrugs from hydrophobic drug molecules, evaluating their performance, and discussing the advantages, challenges, and future development of these strategies.

Tumor microenvironment responsive drug delivery systems

Conventional tumor-targeted drug delivery systems (DDSs) face challenges, such as unsatisfied systemic circulation, low targeting efficiency, poor tumoral penetration, and uncontrolled drug release. Recently, tumor cellular molecules-triggered DDSs have aroused great interests in addressing such dilemmas. With the introduction of several additional functionalities, the properties of these smart DDSs including size, surface charge and ligand exposure can response to different tumor microenvironments for a more efficient tumor targeting, and eventually achieve desired drug release for an optimized therapeutic efficiency. This review highlights the recent research progresses on smart tumor environment responsive drug delivery systems for targeted drug delivery. Dynamic targeting strategies and functional moieties sensitive to a variety of tumor cellular stimuli, including pH, glutathione, adenosine-triphosphate, reactive oxygen species, enzyme and inflammatory factors are summarized. Special emphasis of this review is placed on their responsive mechanisms, drug loading models, drawbacks and merits. Several typical multi-stimuli responsive DDSs are listed. And the main challenges and potential future development are discussed.

Co-delivery of doxorubicin and oleanolic acid by triple-sensitive nanocomposite based on chitosan for effective promoting tumor apoptosis

Nanocomposites as "stevedores" for co-delivery of multidrugs hold great promise in addressing the drawbacks of traditional cancer chemotherapy. In this work, our strategy presents a new avenue for the stepwise release of two co-delivered agents into the tumor cells. The hybrid nanocomposite consists of a pH-responsive chitosan (CS), a thermosensitive poly(N-vinylcaprolactam) (PNVCL) and a functionalized cell-penetrating peptide (H6R6). Doxorubicin (DOX) and oleanolic acid (OA) are loaded into the nanocomposite (H6R6-CS-g-PNVCL). The system displayed a suitable size (∼190 nm), a high DOX loading (13.2 %) and OA loading efficiency (7.3 %). The tumor microenvironment triggered the nanocomposite to be selectively retained in tumor cells, then releasing the drugs. Both in vitro and in vivo studies showed a significant enhancement in antitumor activity of the co-delivered system in comparison to mono-delivery. This approach which relies on redox, pH and temperature effects utilizing co-delivery nanosystems may be beneficial for future applications in cancer chemotherapy.

Hollow Porous Carbon Coated FeS2-Based Nanocatalysts for Multimodal Imaging-Guided Photothermal, Starvation, and Triple-Enhanced Chemodynamic Therapy of Cancer

Specific chemical reactions only happen in the tumor region and produce abundant special chemicals to in situ trigger a train of biological and pathological effects that may enable tumor-specific curative effects to treat cancer without causing serious side effects on normal cells or organs. Chemodynamic therapy (CDT) is a rising tactic for cancer therapy, which induces cancer cell death via a localized Fenton reaction. However, the tumor therapeutic effect is limited by the efficiency of the chemical reaction and relies heavily on the catalyst. Here, we constructed hollow porous carbon coated FeS₂ (HPFeS₂@C)-based nanocatalysts for triple-enhanced CDT. Tannic acid was encapsulated in HPFeS₂@C for reducing Fe³⁺ to Fe²⁺, which had a better catalytic activity to accelerate the Fenton reaction. Afterward, glucose oxidase (GOx) in nanocatalysts could consume glucose in the tumor microenvironment and in situ synchronously produce H₂O₂, which could improve Fenton reaction efficiency. Meanwhile, the consumption of glucose could lead to the starvation effect for cancer starvation therapy. The photothermal effects of HPFeS₂@C could generate heat, which further sped up the Fenton process and implemented synergetic photothermal therapy/starvation therapy/CDT. The biodistribution of nanoparticles was investigated by multimodal magnetic resonance, ultrasound, and photoacoustic imaging. These nanocatalysts could trigger the catalytic Fenton reaction at a high degree, which might provide a good paradigm for nanocatalytic tumor therapy.