Using functional nanomaterials to target and regulate the tumor microenvironment: diagnostic and therapeutic applications

Tumor microenvironment ameliorative and adaptive nanoparticles with photothermal-to-photodynamic switch for cancer phototherapy

The notorious tumor microenvironment (TME) usually becomes more deteriorative during phototherapeutic progress that hampers the antitumor efficacy. To overcome this issue, we herein report the ameliorative and adaptive nanoparticles (TPASIC-PFH@PLGA NPs) that simultaneously reverse hypoxia TME and switch photoactivities from photothermal-dominated state to photodynamic-dominated state to maximize phototherapeutic effect. TPASIC-PFH@PLGA NPs are designed by incorporating oxygen-rich liquid perfluorohexane (PFH) into the intraparticle microenvironment to regulate the intramolecular motions of AIE photosensitizer TPASIC. TPASIC exhibits a unique aggregation-enhanced reactive oxygen species (ROS) generation feature. PFH incorporation affords TPASIC the initially dispersed state, thus promoting active intramolecular motions and photothermal conversion efficiency. While PFH volatilization leads to nanoparticle collapse and the formation of tight TPASIC aggregates with largely enhanced ROS generation efficiency. As a consequence, PFH incorporation not only currently promotes both photothermal and photodynamic efficacies of TPASIC and increases the intratumoral oxygen level, but also enables the smart photothermal-to-photodynamic switch to maximize the phototherapeutic performance. The integration of PFH and AIE photosensitizer eventually delivers more excellent antitumor effect over conventional phototherapeutic agents with fixed photothermal and photodynamic efficacies. This study proposes a new nanoengineering strategy to ameliorate TME and adapt the treatment modality to fit the changed TME for advanced antitumor applications.

Innovative optical imaging strategies for monitoring immunotherapy in the tumor microenvironments

BACKGROUND

The tumor microenvironment (TME) plays a critical role in cancer progression and response to immunotherapy. Immunotherapy targeting the immune system has emerged as a promising treatment modality, but challenges in understanding the TME limit its efficacy. Optical imaging strategies offer noninvasive, real-time insights into the interactions between immune cells and the TME.

OBJECTIVE

This review assesses the progress of optical imaging technologies in monitoring immunotherapy within the TME and explores their potential applications in clinical trials and personalized cancer treatment.

METHODS

This is a comprehensive literature review based on the advances in optical imaging modalities including fluorescence imaging (FLI), bioluminescence imaging (BLI), and photoacoustic imaging (PAI). These modalities were analyzed for their capacity to provide high-resolution, real-time imaging of immune cell dynamics, tumor vasculature, and other critical components of the TME.

RESULTS

Optical imaging techniques have shown significant potential in tracking immune cell infiltration, assessing immune checkpoint inhibitors, and visualizing drug delivery within the TME. Technologies like FLI and BLI are pivotal in tracking immune responses in preclinical models, while PAI provides functional imaging with deeper tissue penetration. The integration of these modalities with immunotherapy holds promise for improving treatment monitoring and outcomes.

CONCLUSION

Optical imaging is a powerful tool for understanding the complexities of the TME and optimizing immunotherapy. Further advancements in imaging technologies, combined with nanomaterial-based approaches, could pave the way for enhanced diagnostic accuracy and therapeutic efficacy in cancer treatment.

Tumor Acidity-Triggered Bioorthogonal Reactions for Biomedical Applications

Cancer is one of the most serious threats to human health. Over the past few years, researchers have incrementally uncovered the pivotal role of tumor acidity in tumor formation, development, and treatment. In addition, bioorthogonal reactions have been widely used in tumor diagnosis and therapy, owing to their advantageous characteristics, including small ligand size, biocompatibility, fast reaction kinetics, and high chemospecificity. Consequently, bioorthogonal reactions triggered by tumor acidity have become an emerging strategy in biomedical applications. On this basis, we first elucidate the concept and major strategies of tumor acidity-triggered bioorthogonal reactions. Additionally, we review the progress in biomedical applications, with a particular focus on their importance in disease diagnosis and treatment. Finally, clinical challenges and future trends are also outlooked.

Metal-organic frameworks as candidates for tumor sonodynamic therapy: Designable structures for targeted multifunctional transformation

Sonodynamic therapy (SDT), utilizing ultrasound (US) as the trigger, has gained popularity recently as a therapeutic approach with significant potential for treating various diseases. Metal-organic frameworks (MOFs), characterized by structural flexibility, are prominently emerging in the SDT realm as an innovative type of sonosensitizer, offering functional tunability and biocompatibility. However, due to the inherent limitations of MOFs, such as low reactivity to reactive oxygen species and challenges posed by the complex tumor microenvironment, MOF-based sonosensitizers with singular functions are unable to demonstrate the desired therapeutic efficacy and may pose risks of toxicity, limiting their biological applications to superficial tissues. MOFs generally possess distinctive crystalline structures and properties, and their controlled coordination environments provide a flexible platform for exploring structure-effect relationships and guiding the design and development of MOF-based nanomaterials to unlock their broader potential in biological fields. The primary focus of this paper is to summarize cases involving the modification of different MOF materials and the innovative strategies developed for various complex conditions. The paper outlines the diverse application areas of functionalized MOF-based sonosensitizers in tumor synergistic therapies, highlighting the extensive prospects of SDT. Additionally, challenges confronting SDT are briefly summarized to stimulate increased scientific interest in the practical application of MOFs and the successful clinical translation of SDT. Through these discussions, we strive to foster advancements that lead to early-stage clinical benefits for patients. STATEMENT OF SIGNIFICANCE: 1. An overview for the progresses in SDT explored from a novel and fundamental perspective. 2. Different modification strategies to improve the MOFs-mediated SDT efficacy are provided. 3. Guidelines for the design of multifunctional MOFs-based sonosensitizers are offered. 4. Powerful tumor ablation potential is reflected in SDT-led synergistic therapies. 5. Future challenges in the field of MOFs-based SDT in clinical translation are suggested.

Synergistic Brilliance: Engineered Bacteria and Nanomedicine Unite in Cancer Therapy

Engineered bacteria are widely used in cancer treatment because live facultative/obligate anaerobes can selectively proliferate at tumor sites and reach hypoxic regions, thereby causing nutritional competition, enhancing immune responses, and producing anticancer microbial agents in situ to suppress tumor growth. Despite the unique advantages of bacteria-based cancer biotherapy, the insufficient treatment efficiency limits its application in the complete ablation of malignant tumors. The combination of nanomedicine and engineered bacteria has attracted increasing attention owing to their striking synergistic effects in cancer treatment. Engineered bacteria that function as natural vehicles can effectively deliver nanomedicines to tumor sites. Moreover, bacteria provide an opportunity to enhance nanomedicines by modulating the TME and producing substrates to support nanomedicine-mediated anticancer reactions. Nanomedicine exhibits excellent optical, magnetic, acoustic, and catalytic properties, and plays an important role in promoting bacteria-mediated biotherapies. The synergistic anticancer effects of engineered bacteria and nanomedicines in cancer therapy are comprehensively summarized in this review. Attention is paid not only to the fabrication of nanobiohybrid composites, but also to the interpromotion mechanism between engineered bacteria and nanomedicine in cancer therapy. Additionally, recent advances in engineered bacteria-synergized multimodal cancer therapies are highlighted.

Nanoplatform-based strategies for enhancing the lethality of current antitumor PDT

Photodynamic therapy (PDT) exhibits great application prospects in future clinical oncology due to its spatiotemporal controllability and good biosafety. However, the antitumor efficacy of PDT is seriously hindered by many factors, including tumor hypoxia, limited light penetration ability, and strong defense mechanisms of tumors. Considering that it is difficult to completely solve the first two problems, enhancing the lethality of antitumor PDT has become a good idea to extend its clinical application. Herein, we summarize the nanoplatform-involved strategies to effectively amplify the tumoricidal capability of current PDT and then discuss the present bottlenecks and prospects of the nanoplatform-based PDT sensitization strategies in tumor therapy. We hope this review will provide some references for others to design high-performance PDT nanoplatforms for tumor therapy.

Tumor Microenvironment-Regulating Two-Photon Probe Based on Bimetallic Post-Coordinated MOF Facilitating the Dual-Modal and Deep Imaging-Guided Synergistic Therapies

The intricate tumor microenvironment (TME) always brings about unsatisfactory therapeutic effects for treatments, although nanomedicines have been demonstrated to be highly beneficial for synergistic therapies to avoid the side effects caused by the complexity and heterogeneity of cancer. Developing nanotheranostics with the functionalities of both synergistic therapies and TME regulation is a good strategy but is still in its infancy. Herein, an "all-in-one" nanoplatform for integrated diagnosis and treatment, namely, Carrier@ICG@DOX@FA (CIDF), is constructed. Benefiting from the bimetallic coordination of Eu3+-HTHA (4,4,4-trifluoro-1-(9-hexylcarbazol-3-yl)-1,3-butanedione) and Fe3+ with the ligands in UiO-67, CIDF can simultaneously achieve two-photon fluorescence imaging, fluorescent lifetime imaging in deep tumors, and regulation of TME. Owing to its porosity, CIDF can encapsulate indocyanine green as photosensitizers and doxorubicin as chemotherapeutic agent, further realizing light-controlled drug release. Moreover, CIDF exhibited good biocompatibility and tumor targeting by coating with folic-acid-modified polymers. Both in vitro and in vivo experiments demonstrate the excellent therapeutic efficacy of CIDF through dual-modal-imaging-guided synergistic photothermal-, photodynamic-, and chemotherapy. CIDF provides a new paradigm for the construction of TME-regulated synergistic nanotheranostics and realizes the complete elimination of tumors without recurrence.

A CaCO3-based nanoplatform with sonodynamic and tumor microenvironment activated for combined in vitro cancer therapy

INTRODUCTION

Sonodynamic therapy (SDT) has potential clinical applications for cancer therapy, and is yet restricted by complex tumor microenvironmental (TME) factors. Thus, the research problem of TME modulation as well as efficient tumor treatment still needs to be clarified.

METHOD

In this study, a calcium carbonate (CaCO3) nanoplatform was designed for ultrasound (US) and TME response-triggered, which encapsulated Ag2S and loaded with l-Arg, and further wrapped with RBC/Platelet membrane, named as QD@Ca/ML-Arg.

RESULTS

Non-invasive US-triggered SDT by Ag2S and acidic environment-responsive drug release were achieved. In vitro experiments validated the efficacy of SDT, Ca-ion interference and nitric oxide (NO) gas therapy as combined therapy for cancer treatment. By means of RNA sequencing, the cancer therapeutic mechanism of SDT in redox-related pathways was elucidated. The immunosuppressive TME was simulated with a M2-macrophage/cancer cell co-culture system to confirm the immune activating effect of immunogenic cell death (ICD).

CONCLUSION

Accordingly, the potential of QD@Ca/ML-Arg-was demonstrated for in vitro TME modulation, cancer therapeutic efficacy and clinical translation.

Cancer cell membrane-coated upconversion nanoparticles/ZnxMn1-xS core-shell nanoparticles for targeted photodynamic and chemodynamic therapy of pancreatic cancer

Oxidative stress induced by reactive oxygen species (ROS) is promising treatment approach for pancreatic ductal adenocarcinoma (PDAC), which is typically insensitive to conventional chemotherapy. In this study, BxPC-3 pancreatic cancer cell membrane-coated upconversion nanoparticles/ZnxMn1-xS core-shell nanoparticles (abbreviated as BUC@ZMS) were developed for tumor-targeted cancer therapy via synergistically oxidative stress and overcoming glutathione (GSH) overexpression. Using a combination of photodynamic therapy (PDT) and chemodynamic therapy (CDT), the BUC@ZMS core-shell nanoparticles were able to elicit the death of pancreatic cancer cells through the high production of ROS. Additionally, the BUC@ZMS core-shell nanoparticles could deplete intracellular GSH and increase the sensitivity of tumor cells to oxidative stress. The in vivo results indicated that BUC@ZMS nanoparticles can accumulate specifically in tumor locations and suppress PDAC without generating obvious toxicity. Thus, it was determined that the as-prepared core-shell nanoparticles would be a viable treatment option for solid malignancies.

Nanogel enhances the efficacy of MLN8237 in treating hepatocellular carcinoma

MLN8237, a specific inhibitor of Aurora-A kinase, is proved to be a potential treatment strategy for hepatocellular carcinoma (HCC). Nanogels improve the efficacy of doxorubicin. Therefore, this study aims to investigate the increase in the effect of nanogels on MLN8237 in inhibiting HCC. Doxorubicin or MLN8237 was used as an anti-tumor drug models which were packaged by organic solvent volatilization method to obtain the doxorubicin-loaded nanogel and the MLN8237-loaded nanogel. Subsequently, CCK8 assay, cell cycle assay, apoptosis assay, real-time PCR, western blotting assay and animal experiments were used to detect the effects of MLN8237 nanogel on the proliferation, cell cycle, apoptosis, tumor growth, mRNA and protein levels of aurora-A and PUMA, and AKT phosphorylation levels in HCC cell lines. The results show that the nanogels can realize pH-regulated hydrophobicity reversal, have certain stability, and can realize lysosomal escape. Moreover, the MLN8237-loaded nanogel has a stronger ability to inhibit HCC cell proliferation, block cell cycle, promote apoptosis and inhibit tumor growth than free MLN8237 by suppressing aurora-A and AKT phosphorylation. In short, nanogel can enhance the efficacy of MLN8237.

Recent Advances in Targeted Drug Delivery Strategy for Enhancing Oncotherapy

Targeted drug delivery is a precise and effective strategy in oncotherapy that can accurately deliver drugs to tumor cells or tissues to enhance their therapeutic effect and, meanwhile, weaken their undesirable side effects on normal cells or tissues. In this research field, a large number of researchers have achieved significant breakthroughs and advances in oncotherapy. Typically, nanocarriers as a promising drug delivery strategy can effectively deliver drugs to the tumor site through enhanced permeability and retention (EPR) effect-mediated passive targeting and various types of receptor-mediated active targeting, respectively. Herein, we review recent targeted drug delivery strategies and technologies for enhancing oncotherapy. In addition, we also review two mainstream drug delivery strategies, passive and active targeting, based on various nanocarriers for enhancing tumor therapy. Meanwhile, a comparison and combination of passive and active targeting are also carried out. Furthermore, we discuss the associated challenges of passive and active targeted drug delivery strategies and the prospects for further study.

Advances of nanotechnology applied to cancer stem cells

Cancer stem cells (CSCs) are a small proportion of the cells that exist in cancer tissues. They are considered to be the culprit of tumor genesis, development, drug resistance, metastasis and recurrence because of their self-renewal, proliferation, and differentiation potential. The elimination of CSCs is thus the key to cure cancer, and targeting CSCs provides a new method for tumor treatment. Due to the advantages of controlled sustained release, targeting and high biocompatibility, a variety of nanomaterials are used in the diagnosis and treatments targeting CSCs and promote the recognition and removal of tumor cells and CSCs. This article mainly reviews the research progress of nanotechnology in sorting CSCs and nanodrug delivery systems targeting CSCs. Furthermore, we identify the problems and future research directions of nanotechnology in CSC therapy. We hope that this review will provide guidance for the design of nanotechnology as a drug carrier so that it can be used in clinic for cancer therapy as soon as possible.

Ganoderenic acid D-loaded functionalized graphene oxide-based carrier for active targeting therapy of cervical carcinoma

Ganoderenic acid D (GAD), extracted from the Chinese herb Ganoderma lucidum, was loaded onto a graphene oxide-polyethylene glycol-anti-epidermal growth factor receptor (GO-PEG-EGFR) carrier to develop a targeting antitumor nanocomposite (GO-PEG@GAD). The carrier was fabricated from PEG and anti-EGFR aptamer modified GO. Targeting was mediated by the grafted anti-EGFR aptamer, which targets the membrane of HeLa cells. Physicochemical properties were characterized by transmission electron microscopy, dynamic light scattering, X-ray powder diffraction, and Fourier transform infrared spectroscopy. High loading content (77.3 % ± 1.08 %) and encapsulation efficiency (89.1 % ± 2.11 %) were achieved. Drug release continued for approximately 100 h. The targeting effect both in vitro and in vivo was confirmed by confocal laser scanning microscopy (CLSM) and imaging analysis system. The mass of the subcutaneous implanted tumor was significantly decreased by 27.27 ± 1.23 % after treatment with GO-PEG@GAD compared with the negative control group. Moreover, the in vivo anti-cervical carcinoma activity of this medicine was due to activation of the intrinsic mitochondrial pathway.

Hybrid nanoarchitectonics of molybdenum dioxide (MoO2) and doxorubicin (DOX) for synergistic chemo-photothermal-based breast carcinoma therapy

Cancer has emerged as one of the severe ailments due to the uncontrolled proliferation rate of cells, accounting for millions of deaths annually. Despite the availability of various treatment strategies, including surgical interventions, radiation, and chemotherapy, tremendous advancements in the past two decades of research have evidenced the generation of different nanotherapeutic designs toward providing synergistic therapy. In this study, we demonstrate the assembly of a versatile nanoplatform based on the hyaluronic acid (HA)-coated molybdenum dioxide (MoO₂) assemblies to act against breast carcinoma. The hydrothermal approach-assisted MoO₂ constructs are immobilized with doxorubicin (DOX) molecules on the surface. Further, these MoO₂-DOX hybrids are encapsulated with the HA polymeric framework. Furthermore, the versatile nanocomposites of HA-coated MoO₂-DOX hybrids are systematically characterized using various characterization techniques, and explored biocompatibility in the mouse fibroblasts (L929 cell line), as well as synergistic photothermal (808-nm laser irradiation for 10 min, 1 W/cm²) and chemotherapeutic properties against breast carcinoma (4T1 cells). Finally, the mechanistic views concerning the apoptosis rate are explored using the JC-1 assay to measure the intracellular mitochondrial membrane potential (MMP) levels. In conclusion, these findings indicated excellent photothermal and chemotherapeutic efficacies, exploring the enormous potential of MoO₂ composites against breast cancer.

Nanoparticle-Mediated Radiotherapy Remodels the Tumor Microenvironment to Enhance Antitumor Efficacy

Radiotherapy (RT) uses ionizing radiation to eradicate localized tumors and, in rare cases, control tumors outside of the irradiated fields via stimulating an antitumor immune response (abscopal effect). However, the therapeutic effect of RT is often limited by inherent physiological barriers of the tumor microenvironment (TME), such as hypoxia, abnormal vasculature, dense extracellular matrix (ECM), and an immunosuppressive TME. Thus, it is critical to develop new RT strategies that can remodel the TME to overcome radio-resistance and immune suppression. In the past decade, high-Z-element nanoparticles have been developed to increase radiotherapeutic indices of localized tumors by reducing X-ray doses and side effects to normal tissues and enhance abscopal effects by activating the TME to elicit systemic antitumor immunity. In this review, the principles of RT and radiosensitization, the mechanisms of radio-resistance and immune suppression, and the use of various nanoparticles to sensitize RT and remodel TMEs for enhanced antitumor efficacy are discussed. The challenges in clinical translation of multifunctional TME-remodeling nanoradiosensitizers are also highlighted.

Peptide-functionalized therapeutic nanoplatform for treatment orthotopic triple negative breast cancer and bone metastasis

Epidermal Growth Factor Receptor (EGFR) is a promising therapeutic target for triple-negative breast cancer (TNBC). Recently, specific EGFR-targeting peptide GE11-based delivery nano-system shows excellent potential because of its chemical versatility and good targeting ability. However, no further research focusing on the downstream of EGFR after binding with GE11 was explored. Hence, we tailor-designed a self-assembled nanoplatform named GENP using amphiphilic molecule of stearic acid-modified GE11. After loading doxorubicin (DOX), the resulted nanoplatform GENP@DOX demonstrated high loading efficiency and sustainable drug release. Importantly, our findings proved that GENP alone significantly suppressed the proliferation of MDA-MB-231 cells via EGFR-downstream PI3K/AKT signaling pathways, contributing to the synergistic treatment with its DOX release. Further work illustrated remarkable therapeutic efficacy both in orthotopic TNBC and its bone metastasis models with minimal biotoxicity. Together, the results highlight that our GENP-functionalized nanoplatform is a promising strategy for the synergistic therapeutic efficacy targeting EGFR-overexpressed cancer.

Nucleus-Targeting Manganese Dioxide Nanoparticles Coated with the Human Umbilical Cord Mesenchymal Stem Cell Membrane for Cancer Cell Therapy

Recently, development of drug delivery systems for accurate delivery of antitumor drugs to tumor sites to improve their antitumor efficacy has attracted great interest in the area of cancer immunotherapy. In this report, an intelligent biodegradable hollow manganese dioxide (HMnO₂) nanoparticle (NP) with a human umbilical cord mesenchymal stem cell (hUC-MSC) membrane coating was designed to exert efficient chemo-immunotherapy for cancer treatment. A TAT peptide-modified membrane structure was constructed for nuclear targeting. Our findings showed that this new nanoreactor inherited the active targeting capability of MSCs and exhibited tumoritropic accumulation significantly at the cancerous parts. Compared with other formulations, intravenous injection of the NPs markedly inhibited tumor growth, relapse, and metastasis. Moreover, we found that the NPs effectively boosted dendritic cell maturation and recruited effector T cells into tumors. Overall, this work demonstrates the great potential of applying MSC membrane-coated manganese dioxide NPs as nucleus-targeting nanocarriers in cancer chemo-immunotherapy.

Biodegradable nanomaterials for diagnosis and therapy of tumors

Although degradable nanomaterials have been widely designed and applied for cancer bioimaging and various cancer treatments, few reviews of biodegradable nanomaterials have been reported. Herein, we have summarized the representative research advances of biodegradable nanomaterials with respect to the mechanism of degradation and their application in tumor imaging and therapy. First, four kinds of tumor microenvironment (TME) responsive degradation are presented, including pH, glutathione (GSH), hypoxia and matrix metalloproteinase (MMP) responsive degradation. Second, external stimulation degradation is summarized briefly. Next, we have outlined the applications of nanomaterials in bioimaging. Finally, we have focused on some typical examples of biodegradable nanomaterials in radiotherapy (RT), photothermal therapy (PTT), starvation therapy, photodynamic therapy (PDT), chemotherapy, chemodynamic therapy (CDT), sonodynamic therapy (SDT), gene therapy, immunotherapy and combination therapy.

Design of an Injectable Magnetic Hydrogel Based on the Tumor Microenvironment for Multimodal Synergistic Cancer Therapy

Conventional tumor chemotherapy is limited by its low therapeutic efficacy and side effects, which severely hold back its further application. Drug delivery systems (DDSs) based on nanomaterials have attracted wide interest in cancer treatment; especially, the system can realize efficient synergistic therapies. Here, we designed a smart hydrogel drug delivery system with multiple responses to enhance the tumor treatment effect. By cross-linking oxidized hydroxypropyl cellulose with carboxymethyl chitosan, an injectable hydrogel was obtained, into which artesunate (ART), ferroferric oxide (Fe₃O₄) nanoparticles, and black phosphorus nanosheets (BPs) were preloaded. This DDS has multiple functions including magnetic targeting, pH sensitivity, chemodynamic therapy, and photothermal response. This nanoparticle-composited hydrogel not only preserved excellent rheological properties but also allowed for an accurate stable drug release at tumor sites and synergistic effects of multiple therapies. The in vitro and in vivo experiments revealed that this DDS could efficiently eliminate the HepG2 tumor with good biocompatibility. Taken together, this study clarifies the possible antitumor mechanism of this ART-loaded nanoparticle-composited hydrogel and provides a new strategy for synergistic photothermal-chemo-chemodynamic therapy.

Covalent Organic Frameworks as Nanocarriers for Improved Delivery of Chemotherapeutic Agents

Cancer has become one of the main causes of death worldwide. Chemotherapy as one of the main therapy modalities is very unsatisfactory. The various nanocarriers have brought new opportunities for effective tumor treatment. However, most of the current nanocarriers still suffer from low efficiency and confront significant challenges in overcoming multiple biological barriers. Compared with conventional nanocarriers, covalent organic frameworks (COFs) with unique and attractive features exhibited great potential to serve as a promising platform for anticancer drug delivery. In this review, we first summarize the strategies and challenges of nanocarriers for cancer chemotherapy and then highlight the recent advances in COF-based nanocarriers for improved delivery of chemotherapeutic agents. Finally, the challenges remaining for COF-based nanocarriers for clinical applications are outlined.

pH-Responsive Polymer Nanomaterials for Tumor Therapy

The complexity of the tumor microenvironment presents significant challenges to cancer therapy, while providing opportunities for targeted drug delivery. Using characteristic signals of the tumor microenvironment, various stimuli-responsive drug delivery systems can be constructed for targeted drug delivery to tumor sites. Among these, the pH is frequently utilized, owing to the pH of the tumor microenvironment being lower than that of blood and healthy tissues. pH-responsive polymer carriers can improve the efficiency of drug delivery in vivo, allow targeted drug delivery, and reduce adverse drug reactions, enabling multifunctional and personalized treatment. pH-responsive polymers have gained increasing interest due to their advantageous properties and potential for applicability in tumor therapy. In this review, recent advances in, and common applications of, pH-responsive polymer nanomaterials for drug delivery in cancer therapy are summarized, with a focus on the different types of pH-responsive polymers. Moreover, the challenges and future applications in this field are prospected.

Homotypic Cancer Cell Membranes Camouflaged Nanoparticles for Targeting Drug Delivery and Enhanced Chemo-Photothermal Therapy of Glioma

Glioma is among the deadliest types of brain cancer, for which there currently is no effective treatment. Chemotherapy is mainstay in the treatment of glioma. However, drug tolerance, non-targeting, and poor blood–brain barrier penetrance severely inhibits the efficacy of chemotherapeutics. An improved treatment method is thus urgently needed. Herein, a multifunctional biomimetic nanoplatform was developed by encapsulating graphene quantum dots (GQDs) and doxorubicin (DOX) inside a homotypic cancer cell membrane (CCM) for targeted chemo-photothermal therapy of glioma. The GQDs with stable fluorescence and a superior light-to-heat conversion property were synthesized as photothermal therapeutic agents and co-encapsulated with DOX in CCM. The as-prepared nanoplatform exhibited a high DOX loading efficiency. The cell membrane coating protected drugs from leakage. Upon an external laser stimuli, the membrane could be destroyed, resulting in rapid DOX release. By taking advantage of the homologous targeting of the cancer cell membrane, the GQDs/DOX@CCM were found to actively target tumor cells, resulting in significantly enhanced cellular uptake. Moreover, a superior suppression efficiency of GQDs/DOX@CCM to cancer cells through chemo-photothermal treatment was also observed. The results suggest that this biomimetic nanoplatform holds potential for efficient targeting of drug delivery and synergistic chemo-photothermal therapy of glioma.

Magnetic CuFe2O4 with intrinsic protease-like activity inhibited cancer cell proliferation and migration through mediating intracellular proteins

Protease has been widely used in biological and industrial fields. Developing efficient artificial enzyme mimics remains a major technical challenge due to the high stability of peptide bonds. Nanoenzymes with high stability, high activity and low cost, provided new opportunities to break through natural enzyme inherent limitations. However, compared with many nanomaterials with inherent peroxidase activity, the intrinsic mimic proteases properties of magnetic nanomaterials were seldom explored, let alone the interaction between magnetic nanomaterials and cellular proteins. Herein, we reported for the first time that magnetic CuFe₂O₄ possesses inherent protease activity to hydrolyze bovine serum albumin (BSA) and casein under physiological conditions, and the CuFe₂O₄ is more resistant to high temperature than the natural trypsin. It also exhibited significantly higher catalytic efficiency than other copper nanomaterials and can be recycled for many times. Protease participated in pathophysiological processes and all stages of tumor progression. Interesting, CuFe₂O₄ exhibited anti-proliferative effect on A549, SKOV3, HT-29, BABL-3T3 and HUVEC cells, as well as it was particularly sensitive against SKOV3 cells. CuFe₂O₄ was about 30 times more effective than conventional chemotherapy drugs oxaliplatin and artesunate against SKOV3 cells. In addition, CuFe₂O₄ also mediated the expression of intracellular proteins, such as MMP-2, MMP-9, F-actin, and NF-kB, which may be associated with global protein hydrolysis by CuFe₂O₄, leading to inhibition of cell migration. The merits of the high magnetic properties, good protease-mimic and antitumor activities make CuFe₂O₄ nanoparticles very prospective candidates for many applications such as proteomics and biotechnology.

An autophagy-inhibitory MOF nanoreactor for tumor-targeted synergistic therapy

An autophagy-inhibitory metal-organic framework (MOF) nanoreactor was developed for tumor-targeted synergistic therapy. The nanoreactor could inhibit autophagy to enhance the glucose oxidase (GOx)-mediated starvation therapy. And the H2O2 generated in...

Progress and Principle of Drug Nanocrystals for Tumor Targeted Delivery

Drugs are referred to as drug nanocrystals when they exist as nanoscale crystal structures. This kind of nanocarrier has been widely utilized to increase the solubility and absorption for poorly aqueous soluble drugs after oral administration, or prolong the drug circulation when intravenous administration. The systemic cytotoxicity caused by antitumor drugs usually come from the nonspecific drug distribution. To solve the disadvantage of poor targetability, drug nanocrystals for tumor targeted delivery have been developed in recent years. In this review, the targeting mechanisms of various surface modified drug nanocrystals are introduced with the focus on passive targeting, active targeting and stimuli-responsive targeting in details. Function and application of common surface modified materials are also discussed.

Covalent RGD-graphene-phthalocyanine nanocomposite for fluorescence imaging-guided dual active/passive tumor-targeted combinatorial phototherapy

Poor tumor selectivity, low stability and quenched fluorescence are the main challenges to be overcome for nanomedicine, and are mainly caused by the dissociation of the nanostructure and aggregation of chromophores in the biological environment. Herein, covalently connected nanoparticles RGD-graphene-phthalocyanine (RGD-GO-SiPc) were constructed based on RGD peptide, silicon phthalocyanine (SiPc) and graphene oxide (GO) via a conjugation reaction for fluorescence imaging-guided cancer-targeted combinatorial phototherapy. The prepared RGD-GO-SiPc exhibited supreme biological stability, high-contrast fluorescence imaging, significantly enhanced NIR absorption, high photothermal conversion efficiency (25.6%), greatly improved cancer-targeting capability, and synergistic photodynamic (PDT) and photothermal therapy (PTT) efficacy along with low toxicity. Both in vitro and in vivo biological studies showed that RGD-GO-SiPc is a kind of promising multifunctional nanomedicine for fluorescence imaging-guided combined photothermal and photodynamic therapy with dual active/passive tumor-targeting properties.

Tumor microenvironment and nanotherapeutics: intruding the tumor fort

Over recent years, advancements in nanomedicine have allowed new approaches to diagnose and treat tumors. Nano drug delivery systems exploit the enhanced permeability and retention (EPR) effect and enter the tumor tissue's interstitial space. However, tumor barriers play a crucial role, and cause inefficient EPR or the homing effect. Mounting evidence supports the hypothesis that the components of the tumor microenvironment, such as the extracellular matrix, and cellular and physiological components collectively or cooperatively hinder entry and distribution of drugs, and therefore, limit the theragnostic applications of cancer nanomedicine. This abnormal tumor microenvironment plays a pivotal role in cancer nanomedicine and was recently recognized as a promising target for improving nano-drug delivery and their therapeutic outcomes. Strategies like passive or active targeting, stimuli-triggered nanocarriers, and the modulation of immune components have shown promising results in achieving anticancer efficacy. The present review focuses on the tumor microenvironment and nanoparticle-based strategies (polymeric, inorganic and organic nanoparticles) for intruding the tumor barrier and improving therapeutic effects.

Strategies and applications of covalent organic frameworks as promising nanoplatforms in cancer therapy

Cancer nanomedicine is the best option to face the limits of conventional chemotherapy and phototherapy methods, and thus the intensive quest for new nanomaterials to improve therapeutic efficacy and safety is still underway. Owing to their low density, well-defined structures, large surface area, finely tunable pore size, and metal ion free features, covalent organic frameworks (COFs) have been extensively studied in many research fields. The recent great interest in nanoscale COFs to improve the properties of bulk COFs has led to broadening of their applicability in the biomedical field, such as nanocarriers with an outstanding loading capacity and efficient delivery of therapeutic agents, smart theranostic nanoplatforms with excellent stability, high ROS generation, light-to-heat conversion capabilities, and different response and diagnostic characteristics. The COFs and related nanoplatforms with a wide variety of designability and functionalization have opened up a new avenue for exciting opportunities in cancer therapy. Herein we review the state-of-the-art technical and scientific developments in this emerging field, focusing on the overall progress addressed so far in building versatile COF-based nanoplatforms to enhance chemotherapy, photodynamic/photothermal therapy, and combination. Future perspectives for achieving the synergistic effect of cancer elimination and clinical translation are further discussed to motivate future contributions and explore new possibilities.

Recent Advances in Engineered Materials for Immunotherapy-Involved Combination Cancer Therapy

Immunotherapy that can activate immunity or enhance the immunogenicity of tumors has emerged as one of the most effective methods for cancer therapy. Nevertheless, single-mode immunotherapy is still confronted with several critical challenges, such as the low immune response, the low tumor infiltration, and the complex immunosuppression tumor microenvironment. Recently, the combination of immunotherapy with other therapeutic modalities has emerged as a powerful strategy to augment the therapeutic outcome in fighting against cancer. In this review, recent research advances of the combination of immunotherapy with chemotherapy, phototherapy, radiotherapy, sonodynamic therapy, metabolic therapy, and microwave thermotherapy are summarized. Critical challenges and future research direction of immunotherapy-based cancer therapeutic strategy are also discussed.

Hybrid nanoparticle composites applied to photodynamic therapy: strategies and applications

Photodynamic therapy (PDT), as a robust strategy, has long been applied to cancer treatment owing to the meaningful breakthroughs and unique advantages, including ignorable invasiveness and spatio-temporal selectivity. Numerous PDT agents, especially hybrid nanoparticle composite (hybrid)-based sensitizers consisting of an organic polymer and inorganic nanoparticles (NPs), feature the synergetic pros of the components, which have unlocked the additional potentials of PDT. Although reviews relating to the applications of hybrids to PDT have been previously reported, most of them only focus on the designs of smart hybrids integrating multimodal imaging-guided multiple treatment modalities. Traditional PDT treatment has several limitations, such as inadequate PDT agents accumulating in cancer tissues, inferior PDT effect due to the devastating cancer hypoxia environment, relevant systemic toxicity in non-intelligent stimulation response treatment systems, and serious dependence of PDT on external light sources. Many strategies have been developed for overcoming these limitations, including improvement of cancer-homing ability by introducing active targeting groups, remodeling of the cancer hypoxia environment through oxygen regulators, intratumor release of ROS through activatable molecules, and replacement of laser light by X-rays or self-luminescence. This review aims to summarize the most recent advances in designing hybrids for improving the therapeutic efficacy of PDT.

Towards Microfluidic-Based Exosome Isolation and Detection for Tumor Therapy

Exosomes are a class of cell-secreted, nano-sized extracellular vesicles with a bilayer membrane structure of 30-150 nm in diameter. Their discovery and application have brought breakthroughs in numerous areas, such as liquid biopsies, cancer biology, drug delivery, immunotherapy, tissue repair, and cardiovascular diseases. Isolation of exosomes is the first step in exosome-related research and its applications. Standard benchtop exosome separation and sensing techniques are tedious and challenging, as they require large sample volumes, multi-step operations that are complex and time-consuming, requiring cumbersome and expensive instruments. In contrast, microfluidic platforms have the potential to overcome some of these limitations, owing to their high-precision processing, ability to handle liquids at a microscale, and integrability with various functional units, such as mixers, actuators, reactors, separators, and sensors. These platforms can optimize the detection process on a single device, representing a robust and versatile technique for exosome separation and sensing to attain high purity and high recovery rates with a short processing time. Herein, we overview microfluidic strategies for exosome isolation based on their hydrodynamic properties, size filtration, acoustic fields, immunoaffinity, and dielectrophoretic properties. We focus especially on advances in label-free isolation of exosomes with active biological properties and intact morphological structures. Further, we introduce microfluidic techniques for the detection of exosomal proteins and RNAs with high sensitivity, high specificity, and low detection limits. We summarize the biomedical applications of exosome-mediated therapeutic delivery targeting cancer cells. To highlight the advantages of microfluidic platforms, conventional techniques are included for comparison. Future challenges and prospects of microfluidics towards exosome isolation applications are also discussed. Although the use of exosomes in clinical applications still faces biological, technical, regulatory, and market challenges, in the foreseeable future, recent developments in microfluidic technologies are expected to pave the way for tailoring exosome-related applications in precision medicine.

Tumor-Acidity Responsive Polymeric Nanoparticles for Targeting Delivery of Angiogenesis Inhibitor for Enhanced Antitumor Efficacy With Decreased Toxicity

Various nanocarriers with tumor targeting ability and improved pharmacokinetic property have been extensively utilized to reduce the toxicity of existing clinical chemotherapeutics. Herein, we showed that by encapsulating angiogenesis inhibitor anlotinib into polymeric nanoparticles, we could significantly decrease its in vivo toxicity. The introduction of pH-responsiveness into the nanocarrier further enhanced its anti-tumor activity. Systemic administration of the anlotinib-loaded nanocarrier into mice bearing A549 and 4T1 subcutaneous tumor received a higher tumor growth suppression and metastasis inhibition without detectable side effects. This strategy offers a promising option to improve the patient compliance of anlotinib.

Selective mediation of ovarian cancer SKOV3 cells death by pristine carbon quantum dots/Cu2O composite through targeting matrix metalloproteinases, angiogenic cytokines and cytoskeleton

It was shown that some nanomaterials may have anticancer properties, but lack of selectivity is one of challenges, let alone selective suppression of cancer growth by regulating the cellular microenvironment. Herein, we demonstrated for the first time that carbon quantum dots/Cu2O composite (CQDs/Cu2O) selectively inhibited ovarian cancer SKOV3 cells by targeting cellular microenvironment, such as matrix metalloproteinases, angiogenic cytokines and cytoskeleton. The result was showed CQDs/Cu2O possessed anticancer properties against SKOV3 cells with IC50 = 0.85 μg mL-1, which was approximately threefold lower than other tested cancer cells and approximately 12-fold lower than normal cells. Compared with popular anticancer drugs, the IC50 of CQDs/Cu2O was approximately 114-fold and 75-fold lower than the IC50 of commercial artesunate (ART) and oxaliplatin (OXA). Furthermore, CQDs/Cu2O possessed the ability to decrease the expression of MMP-2/9 and induced alterations in the cytoskeleton of SKOV3 cells by disruption of F-actin. It also exhibited stronger antiangiogenic effects than commercial antiangiogenic inhibitor (SU5416) through down-regulating the expression of VEGFR2. In addition, CQDs/Cu2O has a vital function on transcriptional regulation of multiple genes in SKOV3 cells, where 495 genes were up-regulated and 756 genes were down-regulated. It is worth noting that CQDs/Cu2O also regulated angiogenesis-related genes in SKOV3 cells, such as Maspin and TSP1 gene, to suppress angiogenesis. Therefore, CQDs/Cu2O selectively mediated of ovarian cancer SKOV3 cells death mainly through decreasing the expression of MMP-2, MMP-9, F-actin, and VEGFR2, meanwhile CQDs/Cu2O caused apoptosis of SKOV3 via S phase cell cycle arrest. These findings reveal a new application for the use of CQDs/Cu2O composite as potential therapeutic interventions in ovarian cancer SKOV3 cells.

Harnessing Endogenous Stimuli for Responsive Materials in Theranostics

Materials that respond to endogenous stimuli are being leveraged to enhance spatiotemporal control in a range of biomedical applications from drug delivery to diagnostic tools. The design of materials that undergo morphological or chemical changes in response to specific biological cues or pathologies will be an important area of research for improving efficacies of existing therapies and imaging agents, while also being promising for developing personalized theranostic systems. Internal stimuli-responsive systems can be engineered across length scales from nanometers to macroscopic and can respond to endogenous signals such as enzymes, pH, glucose, ATP, hypoxia, redox signals, and nucleic acids by incorporating synthetic bio-inspired moieties or natural building blocks. This Review will summarize response mechanisms and fabrication strategies used in internal stimuli-responsive materials with a focus on drug delivery and imaging for a broad range of pathologies, including cancer, diabetes, vascular disorders, inflammation, and microbial infections. We will also discuss observed challenges, future research directions, and clinical translation aspects of these responsive materials.

Responsive and activable nanomedicines for remodeling the tumor microenvironment

Here we describe two protocols for the construction of responsive and activable nanomedicines that regulate the tumor microenvironment (TME). The TME is composed of all non-cellular and cellular components surrounding a tumor, including the surrounding blood vessels, immune cells, fibroblasts, signaling molecules, and extracellular matrix and has a crucial role in tumor initiation, growth, and metastasis. Owing to the relatively stable properties of the TME compared to tumor cells, which exhibit frequent genetic mutations and epigenetic changes, therapeutic strategies targeting the TME using multifunctional nanomedicines hold great potential for anti-tumor therapy. By regulating tumor-associated platelets and pancreatic stellate cells (PSCs), the two major players in the TME, we can effectively manipulate the physiological barriers for enhanced drug delivery and significantly improve the tumor penetration and therapeutic efficacy of chemotherapeutics. The preparation and characterization of the multifunctional nanoparticles takes ~10 h for tumor-associated platelet regulation and 16 h for PSC regulation. These nanoformulations can be readily applied to regulate other components in the TME to realize synergistic or additive anti-tumor activity.

Ultrastable AgBiS2 Hollow Nanospheres with Cancer Cell-Specific Cytotoxicity for Multimodal Tumor Therapy

Specific cytotoxicity for catalytic nanomedicine triggered by the tumor microenvironment (TME) has attracted increasing interest. In this work, we prepared AgBiS₂ hollow nanospheres with narrow bandgaps via rapid precipitation in a weakly polar solvent, which lowered the intrinsic energy gap for the active production of highly reactive hydroxyl radicals (^•OH), especially in the TME. The as-prepared AgBiS₂ hollow nanospheres exhibited enhanced optical absorption and high photothermal conversion efficiency (44.2%). In addition, the hollow structured AgBiS₂ nanospheres were found to have a peroxidase-mimicking feature to induce cancer cell-specific cytotoxicity while exhibiting negligible cytotoxicity toward normal cells, which might be attributed to the efficient production of highly reactive ^•OH originating from the overexpression H₂O₂ in the TME caused by surface catalysis. In particular, the cancer cell-specific cytotoxicity of the nanospheres was greatly enhanced both in vitro and in vivo upon irradiation with a near-infrared (NIR) laser (808 nm). The above-mentioned features of the hollow structured AgBiS₂ will make it a promising candidate for tumor therapy.

Multifunctional peptides for tumor therapy

Controlled nano-systems for drug delivery are designed to deliver therapeutical drugs to desirable sites on demand. Due to the diverse physiological functions of peptides, it is reasonable to introduce peptides into anti-tumor nano-system. The integration of peptides into nanomaterials has complementary advantages, which not only avoids the rapid degradation of peptides in vivo, but also improves the intelligence and functionality of the nano-system. We summarized the functional peptides with targeting and stimulus-responsive properties, and the present review outlined the most relevant and recent developed peptide-based multifunctional nanomaterials for tumor therapy.

Stroma-Targeting Therapy in Pancreatic Cancer: One Coin With Two Sides?

Pancreatic ductal adenocarcinoma (PDAC) is a malignancy with one of the worst prognoses worldwide and has an overall 5-year survival rate of only 9%. Although chemotherapy is the recommended treatment for patients with advanced PDAC, its efficacy is not satisfactory. The dense dysplastic stroma of PDAC is a major obstacle to the delivery of chemotherapy drugs and plays an important role in the progression of PDAC. Therefore, stroma-targeting therapy is considered a potential treatment strategy to improve the efficacy of chemotherapy and patient survival. While several preclinical studies have shown encouraging results, the anti-tumor potential of the PDAC stroma has also been revealed, and the extreme depletion might promote tumor progression and undermine patient survival. Therefore, achieving a balance between stromal abundance and depletion might be the further of stroma-targeting therapy. This review summarized the current progress of stroma-targeting therapy in PDAC and discussed the double-edged sword of its therapeutic effects.

Regulating Interactions Between Targeted Nanocarriers and Mononuclear Phagocyte System via an Esomeprazole-Based Preconditioning Strategy

Purpose

The mononuclear phagocyte system (MPS) presents a formidable obstacle that hampers the delivery of various nanopreparations to tumors. Therefore, there is an urgent need to improve the off-MPS targeting ability of nanomedicines. In the present study, we present a novel preconditioning strategy to substantially increase the circulation times and tumor targeting of nanoparticles by regulating nanocarrier-MPS interactions.

Methods

In vitro, the effect of different vacuolar H⁺-ATPase inhibitors on macrophage uptake of targeted or nontargeted lipid vesicles was evaluated. Specifically, the clinically approved proton-pump inhibitor esomeprazole (ESO) was selected as a preconditioning agent. Then, we further investigated the blocking effect of ESO on the macrophage endocytosis of nanocarriers. In vivo, ESO was first intravenously administered into A549-tumor-bearing nude mice, and 24 h later, the c(RGDm7)-modified vesicles co-loaded with doxorubicin and gefitinib were intravenously injected.

Results

In vitro, ESO was found to reduce the interactions between macrophages and c(RGDm7)-modified vesicles by interfering with the latter’s lysosomal trafficking. Studies conducted in vivo confirmed that ESO pretreatment greatly decreased the liver and spleen distribution of the targeted vesicles, enhanced their tumor accumulation, and improved the therapeutic outcome of the drug-loaded nanomedicines.

Conclusion

Our findings indicate that ESO can regulate the nanoparticle-MPS interaction, which provides a feasible option for enhancing the off-MPS targeting of nanomedicines.

Smart stimuli-responsive biopolymeric nanomedicines for targeted therapy of solid tumors

Solid tumors form a permissive microenvironment with irregular features, including high pressured tumor interstitial fluid with acidic pH, co-adaptation of cancer cells with other cells like the immune system cells, abnormal metabolism and anomalous overexpression of various pieces of molecular machinery. The functional expressions of several oncomarkers in different solid tumors have led to the development of targeted drug-delivery systems (DDSs). As a new class of DDSs, stimuli-responsive nanomedicines (SRNMs) have been developed using advanced nanobiomaterials such as biopolymers that show excellent biocompatibility with low inherent immunogenicity. In this review, we aim to overview different types of SRNMs, present deep insights into the stimuli-responsive biopolymers and discuss the most up-to-date progress in the design and development of SRNMs used as advanced DDSs for targeted therapy of cancer.

Advances in engineering local drug delivery systems for cancer immunotherapy

Cancer immunotherapy aims to leverage the immune system to suppress the growth of tumors and to inhibit metastasis. The recent promising clinical outcomes associated with cancer immunotherapy have prompted research and development efforts towards enhancing the efficacy of immune checkpoint blockade, cancer vaccines, cytokine therapy, and adoptive T cell therapy. Advancements in biomaterials, nanomedicine, and micro-/nano-technology have facilitated the development of enhanced local delivery systems for cancer immunotherapy, which can enhance treatment efficacy while minimizing toxicity. Furthermore, locally administered cancer therapies that combine immunotherapy with chemotherapy, radiotherapy, or phototherapy have the potential to achieve synergistic antitumor effects. Herein, the latest studies on local delivery systems for cancer immunotherapy are surveyed, with an emphasis on the therapeutic benefits associated with the design of biomaterials and nanomedicines. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Tumor microenvironment-oriented adaptive nanodrugs based on peptide self-assembly

The aberrant metabolism of tumor cells creates an inimitable microenvironment featuring acidic pH, high glutathione (GSH) levels, and overexpression of certain enzymes, which benefits the overwhelming progress of a tumor. Peptide self-assembly, emerging as a biofriendly and versatile fabrication strategy, harnesses multiple noncovalent interactions to obtain a variety of nanostructures tailored on demand. Orchestrating the reversible nature of noncovalent interactions and abnormal physiological parameters in the tumor microenvironment enables peptide-based nanodrugs to be targetable or switchable, thereby improving the drugs' bioavailability and optimizing the treatment outcome. This review will focus on peptide-modulated self-assembly of photosensitizers, chemotherapeutic drugs, immunoactive agents for tumor microenvironment-oriented adaptive phototherapy, chemotherapy, immunotherapy and combinatorial therapy. We will emphasize the building block design, the intermolecular interaction principle, adaptive structural transformation in the tumor microenvironment and corresponding therapeutic efficacy, and aim to elucidate the critical role of peptide-modulated, tumor microenvironment-oriented adaptive assemblies in improving the therapeutic index. Challenges and opportunities will be covered as well to advance the development and clinical application of tumor therapies based on peptide self-assembly materials and techniques.

Tumor Microenvironment-Responsive Peptide-Based Supramolecular Drug Delivery System

Physical and biochemical differences between tumor tissues and normal tissues provide promising triggering factors that can be utilized to engineer stimuli-responsive drug delivery platforms for cancer treatment. Rationally designed peptide-based supramolecular architectures can perform structural conversion by responding to the tumor microenvironment and achieve the controlled release of antitumor drugs. This mini review summarizes recent approaches for designing internal trigger-responsive drug delivery platforms using peptide-based materials. Peptide assemblies that exhibit a stimuli-responsive structural conversion upon acidic pH, high temperature, high oxidative potential, and the overexpressed proteins in tumor tissues are emphatically introduced. We also discuss the challenges of current peptide-based supramolecular delivery platforms against cancer.

Functional peptide-based drug delivery systems

Peptides are one of the most important functional motifs for constructing smart drug delivery systems (DDSs). Functional peptides can be conjugated with drugs or carriers via covalent bonds, or assembled into DDSs via supramolecular forces, which enables the DDSs to acquire desired functions such as targeting and/or environmental responsiveness. In this mini review, we first introduce the different types of functional peptides that are commonly used for constructing DDSs, and we highlight representative strategies for designing smart DDSs by using functional peptides in the past few years. We also state the challenges of peptide-based DDSs and come up with prospects.

Enzymatic multifunctional biodegradable polymers for pH- and ROS-responsive anticancer drug delivery

A new family of multifunctional biodegradable block copolymers, PEG-poly(ω-pentadecalactone-co-N-methyldiethyleneamine sebacate-co-2,2'-thiodiethylene sebacate) (PEG-PMT), were synthesized via lipase-catalyzed copolymerization procedures. Amphiphilic PEG-PMT copolymers can be readily transformed into stable micellar nanoparticles through self-assembling processes in aqueous medium. The particle sizes increase dramatically after exposure of the particles to the acidic pH and high reactive oxygen species (ROS) conditions in tumor microenvironments, due to protonation of thioether groups and oxidation of amino groups in the PMT micelle cores, respectively. For example, docetaxel (DTX)-loaded PEG-PM-19 % TS micelles were triggered synergistically by acidic pH and ROS stimuli to release over 85 % of the anti-cancer drug. In particular, DTX/PEG-PMT-19 % TS and DTX/PEG-PMT-48 % TS micelles performed better than commercial Duopafei formulation in prohibiting growth of CT-26 tumors xenografed in vivo (70 % of tumor-inhibiting efficiency). Biosafety analysis revealed that DTX-loaded PEG-PMT nanoparticles possessed minimal toxicity towards normal organs, such as liver and kidney. These experimental data demonstrated that the pH- and ROS-responsive PEG-PMT micelles are promising vectors for both delivery of anti-tumor drugs and their controlled release at tumor intracellular sites.

Manganese Oxide Nanomaterials: Synthesis, Properties, and Theranostic Applications

Despite the comprehensive applications in bioimaging, biosensing, drug/gene delivery, and tumor therapy of manganese oxide nanomaterials (MONs including MnO₂ , MnO, Mn₂ O₃ , Mn₃ O₄ , and MnO_x ) and their derivatives, a review article focusing on MON-based nanoplatforms has not been reported yet. Herein, the representative progresses of MONs on synthesis, heterogene, properties, surface modification, toxicity, imaging, biodetection, and therapy are mainly introduced. First, five kinds of primary synthetic methods of MONs are presented, including thermal decomposition method, exfoliation strategy, permanganates reduction method, adsorption-oxidation method, and hydro/solvothermal. Second, the preparations of hollow MONs and MON-based composite materials are summarized specially. Then, the chemical properties, surface modification, and toxicity of MONs are discussed. Next, the diagnostic applications including imaging and sensing are outlined. Finally, some representative rational designs of MONs in photodynamic therapy, photothermal therapy, chemodynamic therapy, sonodynamic therapy, radiotherapy, magnetic hyperthermia, chemotherapy, gene therapy, starvation therapy, ferroptosis, immunotherapy, and various combination therapy are highlighted.