Combretastatin A4 Nanoparticles Combined with Hypoxia-Sensitive Imiquimod: A New Paradigm for the Modulation of Host Immunological Responses during Cancer Treatment

Medicinal chemistry perspective on the structure-activity relationship of stilbene derivatives

Stilbenes are a small family of polyphenolic secondary metabolites produced in a variety of closely related plant species. These compounds function as phytoalexins, aiding plant defense against phytopathogens and plants' adaptation to abiotic environmental factors. Structurally, some important phenolic compounds have a 14-carbon skeleton and usually have two isomeric forms, Z and E. Stilbenes contain two benzene rings linked by a molecule of ethanol or ethylene. Some derivatives of natural (poly)phenolic stilbenes such as resveratrol, pterostilbene, and combretastatin A-4 have shown various biological activities, such as anti-microbial, anti-cancer, and anti-inflammatory properties as well as protection against heart disease, Alzheimer's disease, and diabetes. Among stilbenes, resveratrol is certainly the most popular and extensively studied for its health properties. In recent years, an increasing number of stilbene compounds have been investigated for their bioactivity. This review focuses on the assessment of synthetic stilbene derivatives in terms of their biological activities and structure-activity relationship. The goal of this study is to consider the structural changes and different substitutions on phenyl rings that can improve the desired medicinal effects of stilbene-based compounds beyond the usual standards and subsequently discover biological activities by identifying effective alternatives of the evaluated compounds.

Self-Assembled Nanoparticles from the Amphiphilic Prodrug of Resiquimod for Improved Cancer Immunotherapy

Tumor-associated macrophages (TAMs) usually adopt a tumor-promoting M2-like phenotype, which largely impedes the immune response and therapeutic efficacy of solid tumors. Repolarizing TAMs from M2 to the antitumor M1 phenotype is crucial for reshaping the tumor immunosuppressive microenvironment (TIME). Herein, we developed self-assembled nanoparticles from the polymeric prodrug of resiquimod (R848) to reprogram the TIME for robust cancer immunotherapy. The polymeric prodrug was constructed by conjugating the R848 derivative to terminal amino groups of the linear dendritic polymer composed of linear poly(ethylene glycol) and lysine dendrimer. The amphiphilic prodrug self-assembled into nanoparticles (PLRS) of around 35 nm with a spherical morphology. PLRS nanoparticles could be internalized by antigen-presenting cells (APCs) in vitro and thus efficiently repolarized macrophages from M2 to M1 and facilitated the maturation of APCs. In addition, PLRS significantly inhibited tumor growth in the 4T1 orthotopic breast cancer model with much lower systemic side effects. Mechanistic studies suggested that PLRS significantly stimulated the TIME by repolarizing TAMs into the M1 phenotype and increased the infiltration of cytotoxic T cells into the tumor. This study provides an effective polymeric prodrug-based strategy to improve the therapeutic efficacy of R848 in cancer immunotherapy.

Molecule engineering strategy of toll-like receptor 7/8 agonists designed for potentiating immune stimuli activation

Toll-like receptor 7/8 (TLR-7/8) agonists serve as a promising class of pattern recognition receptors that effectively evoke the innate immune response, making them promising immunomodulatory agents for tumor immunotherapy. However, the uncontrollable administration of TLR-7/8 agonists frequently leads to the occurrence of severe immune-related adverse events (irAEs). Thus, it is imperative to strategically design tumor-microenvironment-associated biomarkers or exogenous stimuli responsive TLR-7/8 agonists in order to accurately evaluate and activate innate immune responses. No comprehensive elucidation has been documented thus far regarding TLR-7/8 immune agonists that are specifically engineered to enhance immune activation. In this feature article, we provide an overview of the advancements in TLR-7/8 agonists, aiming to enhance the comprehension of their mechanisms and promote the clinical progression through nanomedicine strategies. The current challenges and future directions of cancer immunotherapy are also discussed, with the hope that this work will inspire researchers to explore innovative applications for triggering immune responses through TLR-7/8 agonists.

Tumor Microenvironment Remodeling-Mediated Sequential Drug Delivery Potentiates Treatment Efficacy

Toll-like receptor 7/8 agonists, such as imidazoquinolines (IMDQs), are promising for the de novo priming of antitumor immunity. However, their systemic administration is severely limited due to the off-target toxicity. Here, this work describes a sequential drug delivery strategy. The formulation is composed of two sequential modules: a tumor microenvironment remodeling nanocarrier (poly(l-glutamic acid)-graft-methoxy poly(ethylene glycol)/combretastatin A4, termed CA4-NPs) and an immunotherapy nanocarrier (apcitide peptide-decorated poly(l-glutamic acid)-graft-IMDQ-N3 conjugate, termed apcitide-PLG-IMDQ-N3 ). CA4-NPs, as a vascular disrupting agent, are utilized to remodel the tumor microenvironment for enhancing tumor coagulation and hypoxia. Subsequently, the apcitide-PLG-IMDQ-N3 could identify and target tumor coagulation through the binding of surface apcitide peptide to the GPIIb-IIIa on activated platelets. Afterward, IMDQ is activated selectively through the conversion of "-N3 " to "-NH2 " in the presence of hypoxia. The biodistribution results confirm their high tumor uptake of activated IMDQ (22.66%ID/g). By augmenting the priming and immunologic memory of tumor-specific CD8+ T cells, 4T1 and CT26 tumors with a size of ≈500 mm3 are eradicated without recurrence in mouse models.

Adjuvant Novel Nanocarrier-Based Targeted Therapy for Lung Cancer

Lung cancer has the lowest survival rate due to its late-stage diagnosis, poor prognosis, and intra-tumoral heterogeneity. These factors decrease the effectiveness of treatment. They release chemokines and cytokines from the tumor microenvironment (TME). To improve the effectiveness of treatment, researchers emphasize personalized adjuvant therapies along with conventional ones. Targeted chemotherapeutic drug delivery systems and specific pathway-blocking agents using nanocarriers are a few of them. This study explored the nanocarrier roles and strategies to improve the treatment profile's effectiveness by striving for TME. A biofunctionalized nanocarrier stimulates biosystem interaction, cellular uptake, immune system escape, and vascular changes for penetration into the TME. Inorganic metal compounds scavenge reactive oxygen species (ROS) through their photothermal effect. Stroma, hypoxia, pH, and immunity-modulating agents conjugated or modified nanocarriers co-administered with pathway-blocking or condition-modulating agents can regulate extracellular matrix (ECM), Cancer-associated fibroblasts (CAF),Tyro3, Axl, and Mertk receptors (TAM) regulation, regulatory T-cell (Treg) inhibition, and myeloid-derived suppressor cells (MDSC) inhibition. Again, biomimetic conjugation or the surface modification of nanocarriers using ligands can enhance active targeting efficacy by bypassing the TME. A carrier system with biofunctionalized inorganic metal compounds and organic compound complex-loaded drugs is convenient for NSCLC-targeted therapy.

Bioorthogonal-Activated In Situ Vaccine Mediated by a COF-Based Catalytic Platform for Potent Cancer Immunotherapy

Personalized tumor vaccines have become a promising modality for cancer immunotherapy. However, in situ personalized tumor vaccines generated from immunogenic cancer cell death (ICD) and adjuvants are mired by toxic side effects and unsatisfactory efficiency. Herein, by functionalizing the reticular structure to optimize the catalytic activity of the materials, a series of biocompatible covalent organic framework (COF)-based catalysts have been designed and screened for establishing a bioorthogonal-activated in situ cancer vaccine in an efficient and safe way. Especially, pro-doxorubicin (pro-DOX) could be bioorthogonally activated in situ by the COF-based Fe(II) catalysts, which elicited ICD and released tumor-associated antigens (TAAs). This in situ prodrug activation strategy could minimize drug side effects and maximize treatment effects. More importantly, the system could also catalytically activate pro-imiquimod (pro-IMQ, a TLR7/8 immune agonist), which served as an adjuvant to amplify the antitumor immunity. Notably, this bioorthogonal-activated in situ cancer vaccine not only facilitated a strong antitumor immune response but also prevented the dose-dependent side effects of chemotherapeutic drugs, including systemic inflammation caused by the random distribution of adjuvants. To the best of our knowledge, it is the first time to devise an efficient catalytic platform for generating an in situ bioorthogonal-activated cancer vaccine, which would provide a paradigm for achieving secure and robust immunotherapy.

Surgically Derived Cancer Cell Membrane-Coated R837-Loaded Poly(2-Oxazoline) Nanoparticles for Prostate Cancer Immunotherapy

Cancer cell membranes (CCMs) are widely used as sources of tumor-associated antigens (TAAs) for the development of cancer vaccines. To improve the CCM-associated cancer vaccine efficiency, personalized cancer vaccines and effective delivery systems are required. In this study, we employed surgically harvested cancer tissues to prepare personalized CCMs for use as TAAs. Thioglycolic-acid-grafted poly(2-methyl-2-oxazoline)-block-poly(2-butyl-2-oxazoline-co-2-butenyl-2-oxazoline) (PMBEOx-COOH) was synthesized to load imiquimod (R837) efficiently. The personalized CCMs were then coated onto R837-loaded PMBEOx-COOH nanoparticles (POxTA NPs/R837) to obtain surgically derived CCM-coated POxTA NPs (SCNPs/R837). SCNPs/R837 efficiently travelled to the draining lymph nodes and were taken up and presented by plasmacytoid dendritic cells to elicit enhanced antitumor immune responses. When combined with programmed cell death-1 antibodies, SCNPs/R837 exhibited high efficiency corresponding to antitumor progression. Therefore, SCNP/R837 might represent a promising personalized cancer vaccine with significant potential for cancer immunotherapy.

Prospects for hypoxia-based drug delivery platforms for the elimination of advanced metastatic tumors: From 3D modeling to clinical concepts

Hypoxia is a unique characteristic of the solid tumor microenvironment. Hypoxia contributes to multi-drug resistance, metastasis and cancer relapse through numerous molecular pathways, but at the same time provides an opportunity for the development of novel drugs or modalities specifically targeting hypoxic tumor regions. Given the high significance of tumor hypoxia in therapeutic results, we here discuss a variety of hypoxia-adopted strategies, and their potential and utility in the treatment of deep-seated hypoxic tumor cells. We discuss the merits and demerits of these approaches, as well as their combination with other approaches such as photodynamic therapy. We also survey the currently available 3D hypoxia modeling systems, in particular organoid-based microfluidics. Finally, we discuss the potential and the current status of preclinical tumor hypoxia approaches in clinical trials for advanced cancer. We believe that multi-modal imaging and therapeutic hypoxia adopted drug delivery platforms could provide better efficacy and safety profiles, and more importantly personalized therapy. Determining the hypoxia status of tumors could offer a second chance for the clinical translation of hypoxia-based agents, such as hypoxia activated prodrugs (HAPs) from bench to bedside.

Tumor-Selective Activation of Toll-Like Receptor 7/8 Agonist Nano-Immunomodulator Generates Safe Anti-Tumor Immune Responses upon Systemic Administration

Agonists of innate pattern recognition receptors such as toll-like receptors (TLRs) prime adaptive anti-tumor immunity and hold promise for cancer immunotherapy. However, small-molecule TLR agonists cause immune-related adverse effects (irAEs) after systemic administration. Herein, we report a polymeric nano-immunomodulator (cN@SS-IMQ) that is inactive until it is selectively metabolized to an active immunostimulant within the tumor. cN@SS-IMQ was obtained via self-assembly of a cyclo(Arg-Gly-Asp-D-Phe-Lys)-modified amphiphilic copolymeric prodrug. Upon systemic administration, cN@SS-IMQ preferentially accumulated at tumor sites and responded to high intracellular glutathione levels to release native imidazoquinolines for dendritic cell maturation, thereby enhancing the infiltration of T lymphocytes. Collectively, cN@SS-IMQ tends to activate the immune system without irAEs, thus suggesting its promising potential for safe systemic targeting delivery.

COF-based nanoreactors for click-activated prodrug delivery and precise anti-vascular therapy

Herein, we report a new click-activated prodrug, CA4V, and a bioorthogonal nanoreactor, CA4V/ZIF-90@TzCOF@Apt, which consists of a ZIF-90 core, tetrazine-based covalent organic framework (COF) shells and an aptamer polymer coating. When targeting a tumor, the acid-causing collapse of ZIF-90 initiates a nanoconfined bioorthogonal reaction in defined COF cages, which boosts the click efficiency of CA4V activation and therapeutic effects in vivo.

A self-activating nanoized vascular disrupting agent for selective anti-tumor therapy

Vascular disrupting agents (VDAs) have great potential in antitumor therapy, while the efficiency is limited by cardiovascular toxicity. In this study, a self-activating nanoized plinabulin (poly (_l-glutamic acid) grafted Azo-Plinabulin, AzoP-NP) was constructed. The AzoP-NPs can selectively be activated to an amino derivative of plinabulin (AmP) by intrinsic tumor hypoxia, disrupting tumor vessels and amplifying hypoxia, whilst be activated by self-amplified tumor hypoxia, then selectively inhibit tumor growth. In 4T1 tumor model, the AzoP-NPs had a selective biodistribution in tumor, as the free AmP in tumors at 24 h after AzoP-NPs treatment was 18.6 fold of that after AmP treatment and significantly higher than that in other tissues. Accordingly, AzoP-NPs resulted in no obvious acute cardiovascular toxicity (plasma von Willebrand factor in PBS, AzoP-NPs and AmP group: 143.1, 184.0 and 477.6 ng/mL) and a significantly stronger tumor inhibition than AmP. And the sustained release of drug in AzoP-NPs led to a higher maximum tolerated dose (MTD) (MTD of AzoP-NPs and AmP: > 80 vs 20 mg/kg). In addition, AzoP-NPs amplified tumor hypoxic, and synergized the anti-tumor effect of Tirapazamine (TPZ), a hypoxia-activated drug in clinical trials, with an inhibition rate of 97.7% and Q value of 1.89. Therefore, our findings provide new insights into next generation VDAs and their application in tumor therapy.

Discovery of a Novel Vascular Disrupting Agent Inhibiting Tubulin Polymerization and HDACs with Potent Antitumor Effects

Most vascular disrupting agents (VDAs) fail to prevent the regrowth of blood vessels at the edge of tumors, causing tumor rebound and relapse. Herein, a series of novel multifunctional vascular disrupting agents (VDAs) capable of inhibiting microtubule polymerization and histone deacetylases (HDACs) were designed and synthesized using the tubulin polymerization inhibitor TH-0 as the lead compound. Among them, compound TH-6 exhibited the most potent antiproliferative activity (IC₅₀ = 18-30 nM) against a panel of cancer cell lines. As expected, TH-6 inhibited tubulin assembly and increased the acetylation level of HDAC substrate proteins in HepG2 cells. Further in vivo antitumor assay displayed that TH-6 effectively inhibited tumor growth with no apparent toxicity. More importantly, TH-6 disrupted both the internal and peripheral tumor vasculatures, which contributed to the persistent tumor inhibitory effects after drug withdrawal. Altogether, TH-6 deserves to be further investigated for the new approach to clinical cancer therapy.

Implantable Sandwich-like Scaffold/Fiber Composite Spatiotemporally Releasing Combretastatin A4 and Doxorubicin for Efficient Inhibition of Postoperative Tumor Recurrence

Tumor recurrence is a critical conundrum in the postoperative therapy, on account of severe bleeding with disseminated tumor cells, residual tumor cells, and the rich nutrient and oxygen supply transported to tumors by the abundant blood vessels. Biodegradable drug-loaded implants, inserted in the resection cavity right away upon the surgery, possess bleeding prevention and efficient chemotherapeutic capabilities, considered to be a promising strategy to efficiently inhibit the recurrence of the solid tumor. Here, we developed a sandwich-like composite consisting of the combretastatin A4 (CA4)-loaded 3D-printed scaffold and doxorubicin (DOX)-loaded electrospun fiber (Scaffold-CA4@Fiber-DOX), presenting hemostatic, chemotherapeutic, and antibacterial potencies. The lyophilized 3D-printed scaffold with a porous structure rapidly absorbed and clotted the blood cells and disseminated tumor cells to prevent bleeding and tumor metastasis. Subsequently, the preferentially released CA4 from the scaffold disrupted the microtubules of the vascular endothelial cell, resulting in vascular deformation and consequent insufficient nutrient supply to the solid tumor. The sustained release of DOX from the sandwiched electrospun fiber dramatically inhibited the peripheral tumor cell proliferation. This all-in-one multifunctional implant system, combining efficient vascular disruption and chemotherapy, provides a promising strategy for postoperative tumor therapy.

The Role of Toll-like Receptor Agonists and Their Nanomedicines for Tumor Immunotherapy

Toll-like receptors (TLRs) are a class of pattern recognition receptors that play a critical role in innate and adaptive immunity. Toll-like receptor agonists (TLRa) as vaccine adjuvant candidates have become one of the recent research hotspots in the cancer immunomodulatory field. Nevertheless, numerous current systemic deliveries of TLRa are inappropriate for clinical adoption due to their low efficiency and systemic adverse reactions. TLRa-loaded nanoparticles are capable of ameliorating the risk of immune-related toxicity and of strengthening tumor suppression and eradication. Herein, we first briefly depict the patterns of TLRa, followed by the mechanism of agonists at those targets. Second, we summarize the emerging applications of TLRa-loaded nanomedicines as state-of-the-art strategies to advance cancer immunotherapy. Additionally, we outline perspectives related to the development of nanomedicine-based TLRa combined with other therapeutic modalities for malignancies immunotherapy.

Glutathione-Bioimprinted Nanoparticles Targeting of N6-methyladenosine FTO Demethylase as a Strategy against Leukemic Stem Cells

The N6-methyladenosine (m⁶ A) demethylase FTO plays an oncogenic role in acute myeloid leukemia (AML). Despite the promising recent progress for developing some small-molecule FTO inhibitors, the clinical potential remains limited due to mild biological function, toxic side effects and low sensitivity and/or specificity to leukemic stem cells (LSCs). Herein, FTO inhibitor-loaded GSH-bioimprinted nanocomposites (GNPIPP12MA) are developed that achieves targeting of the FTO/m⁶ A pathway synergized GSH depletion for enhancing anti-leukemogenesis. GNPIPP12MA can selectively target leukemia blasts, especially LSCs, and induce ferroptosis by disrupting intracellular redox status. In addition, GNPIPP12MA increases global m⁶ A RNA modification and decreases the transcript levels in LSCs. GNPIPP12MA augments the efficacy of the PD-L1 blockade by increasing the infiltration of cytotoxic T cells for enhanced anti-leukemia immunity. This study offers insights for a GSH-bioimprinted nanoplatform targeting m⁶ A RNA methylation as a synergistic treatment strategy against cancer stem cells that may translate to clinical applications.

Destruction of tumor vasculature by vascular disrupting agents in overcoming the limitation of EPR effect

Nanomedicine greatly improves the efficiency in the delivery of antitumor drugs into the tumor, but insufficient tumoral penetration impairs the therapeutic efficacy of most nanomedicines. Vascular disrupting agent (VDA) nanomedicines are distributed around the tumor vessels due to the low tissue penetration in solid tumors, and the released drugs can selectively destroy immature tumor vessels and block the supply of oxygen and nutrients, leading to the internal necrosis of the tumors. VDAs can also improve the vascular permeability of the tumor, further increasing the extravasation of VDA nanomedicines in the tumor site, markedly reducing the dependence of nanomedicines on the enhanced permeability and retention effect (EPR effect). This review highlights the progress of VDA nanomedicines in recent years and their application in cancer therapy. First, the mechanisms of different VDAs are introduced. Subsequently, different strategies of delivering VDAs are described. Finally, multiple combination strategies with VDA nanomedicines in cancer therapy are described in detail.

Advances in FePt-involved nano-system design and application for bioeffect and biosafety

The rapid development and wide application of nanomaterial-involved theranostic agents have drawn surging attention for improving the living standard of humankind and healthcare conditions. In this review, recent developments in the design, synthesis, biocompatibility evaluation and potential nanomedicine applications of FePt-involved nano-systems are summarized, especially for cancer theranostic and biological molecule detection. The in vivo multi-model imaging capability is discussed in detail, including magnetic resonance imaging and computed tomography. Furthermore, we highlight the significant achievements of various FePt-involved nanotherapeutics for cancer treatment, such as drug delivery, chemodynamic therapy, photodynamic therapy, radiotherapy and immunotherapy. In addition, a series of FePt-involved nanocomposites are also applied for biological molecule detection, such as H₂O₂, glucose and naked-eye detection of cancer cells. Ultimately, we also summarize the challenges and prospects of FePt-involved nano-systems in nanocatalytic medicine. This review is expected to give a general pattern for the development of FePt-involved nano-systems in the field of nanocatalytic medicine and analytical determination.

Smart Nano-PROTACs Reprogram Tumor Microenvironment for Activatable Photo-metabolic Cancer Immunotherapy

Protease inhibitors can modulate intratumoral metabolic processes to reprogram the immunosuppressive tumor microenvironment (TME), which however suffer from the limited efficacy and off-targeted side effects. We report smart nano-proteolysis targeting chimeras (nano-PROTACs) with phototherapeutic ablation and cancer-specific protein degradation to reprogram the TME for photo-metabolic cancer immunotherapy. This nano-PROTAC has a semiconducting polymer backbone linked with a cyclooxygenase 1/2 (COX-1/2)-targeting PROTAC peptide (CPP) via a cathepsin B (CatB)-cleavable segment. CPP can be activated by the tumor-overexpressed CatB to induce the degradation of COX-1/2 via the ubiquitin-proteasome system. The persistent degradation of COX-1/2 depletes their metabolite prostaglandin E₂ which is responsible for activation of immune suppressor cells. Such a smart PROTAC strategy synergized with phototherapy specifically reprograms the immunosuppressive TME and reinvigorates antitumor immunity.

Gold Nanorods Exhibit Intrinsic Therapeutic Activity via Controlling N6-Methyladenosine-Based Epitranscriptomics in Acute Myeloid Leukemia

Reprograming the N6-methyladenosine (m⁶A) landscape is a promising therapeutic strategy against recalcitrant leukemia. In this study, we synthesized gold nanorods (GNRs) of different aspect ratios using a binary surfactant mixture of hexadecyltrimethylammonium bromide and sodium oleate. Following surface functionalization with chitosan and a 12-mer peptide, GNRa-CSP12 measuring 130 × 21 nm² was selectively taken up by leukemia cells via targeted endocytosis. Low doses of GNRa-CSP12 inhibited the growth of leukemia cells by disrupting the redox balance and inducing ferroptosis. Mechanistically, GNRa-CSP12 abrogated endogenous Fe²⁺-dependent m⁶A demethylase activity, which led to global m⁶A hypomethylation and post-transcriptional regulation of downstream genes that are involved in glycolysis, hypoxia, and immune checkpoint pathways. In addition, combination treatment with GNRa-CSP12 and tyrosine kinases inhibitors (TKIs) synergistically obviated the m⁶A-mediated TKI resistance phenotype. Finally, GNRa-CSP12 as a potential immunotherapeutic agent could enhance immunotherapy outcome in leukemia. Our preclinical findings provide the proof-of-concept for targeting m⁶A-methylation-based epitranscriptomics using nanoparticle as an "epigenetic drug" for cancer therapy.

Improved Antibacterial Activity of Water-Soluble Nanoformulated Kaempferol and Combretastatin Polyphenolic Compounds

Kaempferol and combretastatin are polyphenolic compounds derived from plant sources which are known for their antibacterial activity. However, owing to their large size and water insolubility, their antibacterial activity is limited. In this context, the present study focused on the nanoformulation of kaempferol (NF-k) and combretastatin (NF-c) and their influence on water solubility and antibacterial properties. The NF-k and NF-c were prepared using the solvent evaporation method and were thoroughly characterized for evaluating the morphology, molecular vibrations, size, etc. Based on the results, it is observed that the pristine forms of kaempferol and combretastatin drugs get nanoformulated and completely soluble in water. Using particle size analyzer, the particle sizes of NF-k and NF-c were estimated as 334 nm and 260 nm, respectively, which are very fine compared to pristine kaempferol and combretastatin (5193 nm and 1217 nm, respectively). The molecular vibrations that exist in NF-k and NF-c were confirmed by the Fourier transform infrared spectra, where the nanoformulated drug showed lower intensities than the pristine form of kaempferol and combretastatin. The drug release kinetics of the nanoformulated drugs were carried out using the dialysis membrane method and were compared with their pristine forms. Owing to the size effect, the NF-k and NF-c release up to 50% of the drug in a sustained manner till 50 h showing twofold higher concentration than the control where it released 25%. The antibacterial activity was assessed by measuring the optical density at 600 nm using UV-vis spectrophotometer and displayed significant activity against gram-positive Staphylococcus aureus strain. The mechanisms behind the antibacterial activity of NF-k and NF-c were discussed in detail. The activation of ATP-dependent efflux pump system and the blockage of porin channels could be the cause for the bactericidal activity. Our understanding of efflux pumps and their role in antibacterial activity is still in its early stages. No studies have been performed to date using nanoformulations of kaempferol and combretastatin to investigate their roles. This complicates the determination of the exact mechanisms acting against bacterial growth when using nanoformulation drugs. Our increasing knowledge of water-soluble nanoformulation drugs and their roles in reduced bacterial activity will pave the way to developing effective treatments in the future.

Tumor vasculature-targeting nanomedicines

Uncontrolled tumor growth and subsequent distant metastasis are highly dependent on an adequate nutrient supply from tumor blood vessels, which have relatively different pathophysiological characteristics from those of normal vasculature. Obviously, strategies targeting tumor vasculature, such as anti-angiogenic drugs and vascular disrupting agents, are attractive methods for cancer therapy. However, the off-target effects and high dose administration of these drug regimens critically restrict their clinical applications. In recent years, nanomedicines focused on tumor vasculature have been shown to be superior to traditional therapeutic methods and do not induce side effects. This review will first highlight the recent development of tumor vasculature-targeting nanomedicines from the following four aspects: 1) angiogenesis-inhibiting nanomedicines (AINs); 2) vasculature-disrupting nanomedicines (VDNs); 3) vasculature infarction nanomedicines (VINs); and 4) vasculature-regulating nanomedicines (VRNs). Furthermore, the design principles, limitations, and future directions are also discussed. STATEMENT OF SIGNIFICANCE: Based on the essential roles of tumor blood vessels, the therapeutic strategies targeting tumor vasculature have exhibited good clinical therapeutic outcomes. However, poor patient adherence to free drug administration limits their clinical usage. Nanomedicines have great potential to overcome the abovementioned obstacle. This review summarizes the tumor-vasculature targeting nanomedicines from four aspects: 1) angiogenesis-inhibiting nanomedicines (AINs); 2) vasculature-disrupting nanomedicines (VDNs); 3) vasculature infarction nanomedicines (VINs); and 4) vasculature regulating nanomedicines (VRNs). In addition, this review provides perspectives on this research field.

Dual-responsive nanohybrid based on degradable silica-coated gold nanorods for triple-combination therapy for breast cancer

Multi-modal combination therapy has attracted great attention, owing to the unsatisfactory therapeutic efficacy of conventional chemotherapy. Mesoporous silica-coated gold nanorods possess great potential in photothermal therapy and drug delivery. In this work, we fabricate a dual-responsive nanohybrid for combination treatment of the malignant tumor. In this system, gold nanorods are coated with the degradable mesoporous silica, and the chemotherapy drug doxorubicin (DOX) and photosensitizer (IR820) are co-loaded inside the pores of the silica. The encapsulation of hyaluronic acid (HA) endow the nanohybrids with mammary carcinoma targeting ability and better biocompatibility, owning to CD44+ receptor overexpressed in some cancer cells. As-prepared nanohybrids exhibit high responsiveness to a high glutathione (GSH) level and degrade rapidly in the presence of hyaluronidase (HAase) and GSH after endocytosis by 4T1 cells, allowing the efficient release of loaded DOX and IR 820 in tumor sites. Interestingly, near-infrared (NIR) laser not only triggers the generation of reactive oxygen species, but also remarkable photothermal efficacy originating from GNRs. Therefore, upon the irradiation of 808 nm NIR light, the combinatorial photodynamic, photothermal and chemotherapy is achieved, accordingly leading to a highly efficient antitumor outcome in vitro and in vivo. This strategy provides an ideal approach to constructing multimodal cancer therapy system. STATEMENT OF SIGNIFICANCE: • Dual-responsive nanohybrids for combinatorial therapy of breast cancer. • The nanohybrids exhibit both HAase and GSH stimuli-responsive behavior. • The nanohybrids exhibit light-activated PDT/PTT/chemotherapy. • The nanohybrids show good biosafety for potential clinical application.

Emerging Biomaterials-Based Strategies for Inhibiting Vasculature Function in Cancer Therapy

The constant feeding of oxygen and nutrients through the blood vasculature has a vital role in maintaining tumor growth. Interestingly, recent endeavors have shown that nanotherapeutics with the strategy to block tumor blood vessels feeding nutrients and oxygen for starvation therapy can be helpful in cancer treatment. However, this field has not been detailed. Hence, this review will present an exhaustive summary of the existing biomaterial based strategies to disrupt tumor vascular function for effective cancer treatment, including hydrogel or nanogel-mediated local arterial embolism, thrombosis activator loaded nano-material-mediated vascular occlusion and anti-vascular drugs that block tumor vascular function, which may be beneficial to the design of anti-cancer nanomedicine by targeting the tumor vascular system.

From Design to Clinic: Engineered Nanobiomaterials for Immune Normalization Therapy of Cancer

The tumor immune microenvironment (TIME) is comprised of a complex milieu that contributes to stunting antitumor immune responses by restricting T cells to accumulate in the vicinity of the tumor. Nanomedicine-based strategies are being proposed as a salvage effort to reinvigorate antitumor immunity. Various strategies, however, often fail to unleash the antitumor immune response because of the paucity of appropriate therapeutic targets in the complex TIME, invigorating a fervor of investigation into mechanisms underlying the TIME to resist nanomedicines. In this review article, effective nano/biomaterial-based delivery and TIME normalization approaches that promote T cell-mediated antitumor immune response will be discussed, with a focus on emerging preclinical and clinical strategies for immune normalization. Based on currently available evidence, it seems as if the ultimate success of cancer immunotherapy and nanomedicine hinges on the capacity to normalize the TIME. Here, how nanomedicines target immunosuppressive cells and signaling pathways to broaden the impact of cancer immunotherapy are explored. Acquisition of the urgently needed knowledge of nanomedicine-mediated immune normalization will guide researchers and scientists towards clinical applications of cancer immunotherapy.

Polypeptides-Drug Conjugates for Anticancer Therapy

Polypeptides are an important class of biodegradable polymers that have been widely used in drug delivery field. Owing to the controllable synthesis and robust side chain-functionalization ability, polypeptides have long been ideal candidates for conjugation with anticancer drugs. The chemical conjugation of anticancer drugs with polypeptides, termed polypeptides-drug conjugates, has demonstrated several advantages in improving pharmacokinetics, enhancing drug targeting, and controlling drug release, thereby leading to enhanced therapeutic outcomes with reduced side toxicities. This review focuses on the recent advances in the design and preparation of polypeptides-drug conjugates for enhanced anticancer therapy. Strategies for conjugation of different types of drugs, including small-molecule chemotherapeutic drugs, proteins, vascular disrupting agents, and gas molecules, onto polypeptides backbone are summarized. Finally, the challenges and future perspectives on the development of innovative polypeptides-drug conjugates for clinical cancer treatment are also presented.

Nanoparticles Composed of PEGylated Alternating Copolymer-Combretastatin A4 Conjugate for Cancer Therapy

Chemotherapy using vascular targeting agents is an emerging new approach for cancer therapy. Combretastatin A4 (CA4) is a leading vascular-disrupting agent that targets the tumor blood vasculature for clinical tumor elimination. However, the extremely poor water solubility of CA4 hinders its biomedical applications. In this study, nanoparticles composed of novel PEGylated alternating copolymer-CA4 conjugates are designed to improve the therapeutic efficiency of CA4. First, an alternating copolymer with an alkene-pendant is synthesized by mPEG-OH-initiated ring-opening copolymerization. Then, side carboxyl groups are introduced by a thio-ene "click" chemical reaction, followed with CA4 conjugation through the Yamaguchi-reaction, resulting in the target copolymer, mPEG-b-P(PA-alt-GCA4). Interestingly, the polymer-drug conjugates can self-assemble into nanoparticles with an average diameter of 55.6 nm. The in vitro drug release and cytotoxicity of the obtained CA4-NPs toward 4T1 cells are investigated. Finally, the antitumor efficiency is evaluated in a 4T1-tumor bearing murine model. The in vivo test results demonstrate that CA4-NPs inhibited tumor growth much more efficiently at doses of 30 and 60 mg kg^-1 , compared with the control group.

Enzyme/GSH dual-responsive biodegradable nanohybrid for spatiotemporally specific photodynamic and hypoxia-augmented therapy against tumors

Photodynamic therapy (PDT) efficacy has been severely limited by the hypoxia in tumor microenvironment. A multitherapy modality was developed, integrating the advantages of each therapy and a nanocarrier: PDT and PDT-induced hypoxia-activated chemotherapy. Following PDT-induced hypoxia augmented in the periphery of the tumors, chemotherapy was locally activated. To this end, new indocyanine green (IR820) and a hypoxia-activated prodrug tirapazamine (TPZ) were loaded in glutathione (GSH) decomposable mesoporous organic silica nanoparticles (GMONs), tethered by hyaluronic acid (HA). This nanohybrid showed a tendency to accumulate and be retained in tumors, due to passive and active targeting. The IR820 produced singlet oxygen (¹O₂) under near-infrared (NIR) laser irradiation and concomitantly tumorous abnormality exacerbated hypoxia. TPZ-mediated hypoxia-activated chemotherapy acted to kill more tumor cells. In vivo results indicated that the tumor inhibition rate of dual-loaded nanohybrids was up to 76% under NIR laser irradiation. The immunofluorescence staining of tumor slices demonstrated that the superficial part of tumors experienced exacerbated hypoxia with laser irradiation, resulting in TPZ exerting powerful chemotherapy effects. This nanohybrid is expected to be valuable as spatiotemporally specific therapy for cancer.

Non-Invasive Evaluation of Acute Effects of Tubulin Binding Agents: A Review of Imaging Vascular Disruption in Tumors

Tumor vasculature proliferates rapidly, generally lacks pericyte coverage, and is uniquely fragile making it an attractive therapeutic target. A subset of small-molecule tubulin binding agents cause disaggregation of the endothelial cytoskeleton leading to enhanced vascular permeability generating increased interstitial pressure. The resulting vascular collapse and ischemia cause downstream hypoxia, ultimately leading to cell death and necrosis. Thus, local damage generates massive amplification and tumor destruction. The tumor vasculature is readily accessed and potentially a common target irrespective of disease site in the body. Development of a therapeutic approach and particularly next generation agents benefits from effective non-invasive assays. Imaging technologies offer varying degrees of sophistication and ease of implementation. This review considers technological strengths and weaknesses with examples from our own laboratory. Methods reveal vascular extent and patency, as well as insights into tissue viability, proliferation and necrosis. Spatiotemporal resolution ranges from cellular microscopy to single slice tomography and full three-dimensional views of whole tumors and measurements can be sufficiently rapid to reveal acute changes or long-term outcomes. Since imaging is non-invasive, each tumor may serve as its own control making investigations particularly efficient and rigorous. The concept of tumor vascular disruption was proposed over 30 years ago and it remains an active area of research.

Enhanced anti-PD-1 therapy in hepatocellular carcinoma by tumor vascular disruption and normalization dependent on combretastatin A4 nanoparticles and DC101

Anti-programmed cell death protein 1 (PD-1) therapy has shown promising efficacy in hepatocellular carcinoma (HCC), but its response rates in advanced HCC are lower than 20%. A critical reason for this is the imbalance between CD8⁺ T cells and tumor burden. Here, a novel concept of vascular disruption and normalization dependent on a polymeric vascular disrupting agent (VDA) poly (_L-glutamic acid)-graft-methoxy poly (ethylene glycol)/combretastatin A4 (CA4-NPs) + a vascular endothelial growth factor (VEGF)/VEGF receptor 2 (VEGFR2) inhibitor DC101 is applied to improve anti-PD-1 therapy, wherein CA4-NPs reduce tumor burden and DC101 simultaneously increases the number of intratumoral CD8⁺ T cells, successfully regulating the abovementioned imbalance in an H22 tumor model.

Methods: Blood vessel density, tumor cell proliferation, and necrosis were evaluated to reveal the effects on reducing tumor burden by CA4-NP treatment. Pericyte coverage of blood vessels, tumor blood vessel perfusion, tumor hypoxia, and intratumoral immune cells were examined to verify their role in vascular normalization and immune cell homing of DC101. Furthermore, the effects of CA4-NPs + DC101 on reducing tumor burden and increasing the number of immune cells were studied. Finally, tumor suppression, intratumoral CD8⁺ T cell activation, and the synergistic effects of anti-PD-1 combined with CA4-NPs + DC101 were verified.

Results: The tumor inhibition rate of anti-PD-1 antibody combined with CA4-NPs + DC101 reached 86.4%, which was significantly higher than that of anti-PD-1 (16.8%) alone. Importantly, the Q value reflecting the synergy between CA4-NPs + DC101 and anti-PD-1 was 1.24, demonstrating a strong synergistic effect. Furthermore, CA4-NPs + DC101 improved anti-PD-1 therapy by increasing the number of intratumoral CD8⁺ T cells (anti-PD-1, 0.31% vs triple drug combination, 1.18%).

Conclusion: These results reveal a novel approach to enhance anti-PD-1 therapy with VDAs + VEGF/VEGFR2 inhibitors in HCC.

Nano-delivery systems focused on tumor microenvironment regulation and biomimetic strategies for treatment of breast cancer metastasis

Breast cancer metastasis and recurrence accounts for vast majority of breast cancer-induced mortality. Tumor microenvironment (TME) plays an important role at each step of metastasis, evasion of immunosurveillance, and therapeutic resistance. Consequently, TME-targeting alternatives to traditional therapies focused on breast cancer cells are gaining increasing attention. These new therapies involve the use of tumor cells, and key TME components or secreted bioactive molecules as therapeutic targets, alone or in combination. Recently, TME-related nanoparticles have been developed to deliver various agents, such as bioactive ingredients extracted from natural sources or chemotherapeutic agents, genes, proteins, small interfering RNAs, and vaccines; they have shown great therapeutic potential against breast cancer metastasis. Among various types of nanoparticles, biomimetic nanovesicles are a promising means of addressing the limitations of conventional nanocarriers. This review highlights various nanoparticles related to or mediated by TME according to the key TME components responsible for metastasis. Furthermore, TME-related biomimetic nanoparticles against breast cancer metastasis have garnered attention owing to their promising efficiency, especially in payload delivery and therapeutic action. Here, we summarize recent representative studies on nanoparticles related to cancer-associated fibroblasts, extracellular matrix, endothelial cells, angiogenesis, and immune cells, as well as advanced biomimetic nanoparticles. Future challenges and opportunities in the field are also discussed.

Platelet-Membrane-Coated Nanoparticles Enable Vascular Disrupting Agent Combining Anti-Angiogenic Drug for Improved Tumor Vessel Impairment

Compared with traditional chemotherapeutics, vascular disruption agents (VDAs) have the advantages of rapidly blocking the supply of nutrients and starving tumors to death. Although the VDAs are effective under certain scenarios, this treatment triggers angiogenesis in the later stage of therapy that frequently leads to tumor recurrence and treatment failure. Additionally, the nonspecific tumor targeting and considerable side effects also impede the clinical applications of VDAs. Here we develop a customized strategy that combines a VDA with an anti-angiogenic drug (AAD) using mesoporous silica nanoparticles (MSNs) coated with platelet membrane for the self-assembled tumor targeting accumulation. The tailor-made nanoparticles accumulate in tumor tissues through the targeted adhesion of platelet membrane surface to damaged vessel sites, resulting in significant vascular disruption and efficient anti-angiogenesis in animal models. This study demonstrates the promising potential of combining VDA and AAD in a single nanoplatform for tumor eradication.

Engineering Nanoscale Artificial Antigen-Presenting Cells by Metabolic Dendritic Cell Labeling to Potentiate Cancer Immunotherapy

Nanoscale artificial antigen-presenting cells (aAPCs) are promising to activate T cells directly for cancer immunotherapy, while feasible and flexible strategy to develop nanoscale aAPCs remains highly desirable. Metabolic glycoengineering is used to decorate chemical tags on cells which enables bioorthogonal chemical conjugation of functional molecules. Herein, we develop a nanoscale aAPC by metabolic dendritic cell (DC) labeling to mobilize T-cell based antitumor immunity. We coat azido-labeled DC membrane on imiquimod-loaded polymeric nanoparticles and sequentially modify anti-CD3ε antibody via click chemistry. The nanoscale aAPCs perform improved distribution in lymph nodes and stimulate T cells and resident APCs. Significant inhibition of tumor inoculation and growth is observed after the vaccination, which can be further improved by combining antiprogrammed cell death receptor 1 (PD1) therapy. Our results demonstrate the promising application of metabolically labeled DCs for designing nanoscale aAPCs, which provide a simple and general strategy to potentiate cancer immunotherapy.

Nanotechnology for Hepatocellular Carcinoma: From Surveillance, Diagnosis to Management

Hepatocellular carcinoma (HCC) remains the fourth leading cause of cancer-related death worldwide. However, the clinical diagnosis and treatment modalities are still relatively limited, which urgently require the development of new effective technologies. Recently, nanotechnology has gained extensive attention in HCC surveillance, imaging and pathological diagnosis, and therapeutic strategies. Typically, nanomedicines have been focused on early HCC diagnosis and precise treatment of advanced HCC, which has developed and improved a variety of new technologies and agents for future clinical practice. Furthermore, strategies of facilitating drug release and delivery in current treatment processes such as ablation, systematic therapy, transcatheter arterial chemoembolization, molecular targeted therapy, and immune-modulating therapy have also been studied widely. This review summarizes the recent advances in this area according to current clinical HCC guidelines: 1) Nanoparticle-based HCC surveillance; 2) Nanotechnology for HCC diagnosis; 3) Therapeutic advances for HCC Management; 4) Limitations of applications in nanotechnology for HCC; 5) Conclusions and perspectives. Although there are still many limitations and difficulties to overcome, the investigations of nanomedicines are believed to show potential applications in clinical practice.

Self-Amplifying Nanotherapeutic Drugs Homing to Tumors in a Manner of Chain Reaction

Active tumor-targeting drug delivery has great potency in cancer therapy. However, the targeting efficiency of traditional active tumor-targeting nanotherapeutic drugs is limited by the scarcity of their accessible targets/receptors in tumors. Here, a novel self-amplifying tumor-targeting strategy with a chain reaction mechanism is developed. A coagulation targeting peptide (GNQEQVSPLTLLKXC, termed A15)-decorated poly(L-glutamic acid)-graft-maleimide poly(ethylene glycol)/combretastatin A4 conjugate (A15-PLG-CA4) is prepared to obtain a self-amplifying nanotherapeutic platform homing to tumors. After administration to tumor-bearing mice, A15-PLG-CA4 starts a chain reaction cycle consisting of intratumoral hemorrhage, target FXIIIa amplification, blood clot binding, and CA4 release in tumors. In this way, A15-PLG-CA4 increases the level of its accessible targets (FXIIIa) in a manner of chain reaction. The FXIIIa activity at 8 h is 4.1-fold more than the one at 0 h in the C26 tumors treated with A15-PLG-CA4. The total CA4 concentration at 24 h is 2.9-fold more than the control. A15-PLG-CA4 shows a significantly higher antitumor effect against large C26 tumors (≈500 mm3 ) thanks to the remarkable tumor-targeting ability compared with the control. Therefore, this report highlights the potential of the self-amplifying tumor-targeting strategy in the development of next generation active tumor-targeting nanotherapeutic drugs for tumor therapy.

Galactose Modified Liposomes for Effective Co-Delivery of Doxorubicin and Combretastatin A4

Background

Tumor angiogenesis plays a crucial role in tumor development, and recent efforts have been focused on combining proapoptotic and antiangiogenic activities to enhance antitumor therapy.

Methods

In this study, galactose-modified liposomes (Gal-LPs) were prepared for co-delivery of doxorubicin (DOX) and combretastatin A4 phosphate (CA4P). The co-cultured system composed of BEL-7402 and human umbilical vein endothelial cells (HUVEC) cells was established to effectively evaluate in vitro anti-tumor activity through cell viability and cell migration assay. Furthermore, both in vivo bio-distribution and anti-hepatoma effect of DOX&CA4P/Gal-LPs were investigated on H22 tumor cell-bearing mice.

Results

The results showed that DOX&CA4P/Gal-LPs were spherical with a mean particle size of 143 nm, and could readily be taken up by BEL-7402 cells. Compared with a mixture of free DOX and CA4P, the DOX&CA4P/Gal-LPs were more effective in inhibiting cell migration and exhibited stronger cytotoxicity against BEL-7402 cells alone or a co-cultured system. The in vitro studies showed that the co-cultured system was a more effective model to evaluate the anti-tumor activity of combination therapy. Moreover, DOX&CA4P/Gal-LPs exhibited a greater anti-hepatoma effect than other drug formulations, indicating that Gal-LPs could promote drug accumulation in the tumor region and improve the anti-tumor activity.

Conclusion

Gal-LPs co-loaded with chemotherapeutic and antiangiogenic drugs are a promising strategy for anti-hepatoma therapy.

Smart strategies to overcome tumor hypoxia toward the enhancement of cancer therapy

Hypoxia, as a typical factor in a tumor microenvironment, plays a vital role in tumor treatment resistance, tumor invasion and migration. Hypoxia inducible factor (HIF), as the vital response element of hypoxia, mediates these untoward effects through a series of downstream reactions. Cancer treatments such as photodynamic therapy (PDT), radiotherapy (RT) and chemotherapy are severely hindered by hypoxia and HIF, back, however, could be intelligently manipulated through nanocomposite materials for their great potentiality to combine different functions. Herein, we reviewed the smart strategies in emerging research studies to overcome hypoxia toward the enhancement of tumor therapy.

Robust and smart polypeptide-based nanomedicines for targeted tumor therapy

Nanomedicines based on synthetic polypeptides are among the most versatile and advanced platforms for tumor therapy. Notably, several polypeptide-based nanodrugs are currently under human clinical assessments. The previous (pre)clinical studies clearly show that dynamic stability (i.e. stable in circulation while destabilized in tumor) of nanomedicines plays a vital role in their anti-tumor performance. Various strategies have recently been developed to design dynamically stabilized polypeptide-based nanomedicines by e.g. crosslinking the nanovehicles with acid, reactive oxygen species (ROS), glutathione (GSH), or photo-sensitive linkers, inter-crosslinking between vehicles and drugs, introducing π-π stacking or lipid-lipid interactions in the nanovehicles, chemically conjugating drugs to vehicles, and forming unimolecular micelles. Interestingly, these robust and smart nanodrugs have demonstrated improved tumor targetability, anti-tumor efficacy, as well as safety profiles in different tumor models. In this review, representative strategies to robust and smart polypeptide-based nanomedicines for targeted treatment of varying malignancies are highlighted. The exciting development of dynamic nanomedicines will foresee further increasing clinical translation in the future.

Vascular disrupting agents in cancer therapy

Tumor blood vessel formation is a key process for tumor expansion. Tumor vessels are abnormal and differ from normal vessels in architecture and components. Besides oxygen and nutrients supply, the tumor vessels system, due to its abnormality, is responsible for: hypoxia formation, and metastatic routes. Tumor blood vessels can be a target of anti-cancer therapies. There are two types of therapies that target tumor vessels. The first one is the inhibition of the angiogenesis process. However, the inhibition is often ineffective because of alternative angiogenesis mechanism activation. The second type is a specific targeting of existing tumor blood vessels by vascular disruptive agents (VDAs). There are three groups of VDAs: microtubule destabilizing drugs, flavonoids with anti-vascular functions, and tumor vascular targeted drugs based on endothelial cell receptors. However, VDAs possess some limitations. They may be cardiotoxic and their application in therapy may leave viable residual, so called, rim cells on the edge of the tumor. However, it seems that a well-designed combination of VDAs with other anti-cancer drugs may bring a significant therapeutic effect. In this article, we describe three groups of vascular disruptive agents with their advantages and disadvantages. We mention VDAs clinical trials. Finally, we present the current possibilities of VDAs combination with other anti-cancer drugs.

Poly(L-Glutamic Acid)-Drug Conjugates for Chemo- and Photodynamic Combination Therapy

Despite the polymeric vascular disrupting agent (poly(_L -glutamic acid)-graft-methoxy poly(ethylene glycol)/combretastatin A4) nanoparticles can efficiently inhibit cancer growth, their further application is still a challenge owing to the tumor recurrence and metastasis after treatment. In this study, two poly(_L -glutamic acid)-drug conjugates for chemo-and photodynamic combination therapy are fabricated. PLG-g-mPEG-CA4 nanoparticles are prepared by combretastatin A4 (CA4) and poly(_L -glutamic acid)-graft-methoxy poly(ethylene glycol) (PLG-g-mPEG) using the Yamaguchi esterification reaction. PLG-g-mPEG-TPP (TPP: 5, 10, 15, 20-tetraphenylporphyrin) nanoparticles are constructed using PLG-g-mPEG and amine porphyrin through condensation reaction between carboxyl group of PLG-g-mPEG and amino group of porphyrin. The results showed that PLG-g-mPEG-CA4 nanoparticles have good antitumor ability. PLG-g-mPEG-TPP nanoparticles can produce singlet oxygen under the laser irradiation. Moreover, the combined therapy of PLG-g-mPEG-CA4 and PLG-g-mPEG-TPP nanoparticles has higher antitumor effect than the single chemotherapy or the single photodynamic therapy in vitro. The combination of CA4 nondrug and photodynamic therapy provides a new insight for enhancing the tumor therapeutic effect with vascular disrupting agents and other therapy.

More Than Resveratrol: New Insights into Stilbene-Based Compounds

The concept of a scaffold concerns many aspects at different steps on the drug development path. In medicinal chemistry, the choice of relevant "drug-likeness" scaffold is a starting point for the design of the structure dedicated to specific molecular targets. For many years, the chemical uniqueness of the stilbene structure has inspired scientists from different fields such as chemistry, biology, pharmacy, and medicine. In this review, we present the outstanding potential of the stilbene-based derivatives. Naturally occurring stilbenes, together with powerful synthetic chemistry possibilities, may offer an excellent approach for discovering new structures and identifying their therapeutic targets. With the development of scientific tools, sophisticated equipment, and a better understanding of the disease pathogenesis at the molecular level, the stilbene scaffold has moved innovation in science. This paper mainly focuses on the stilbene-based compounds beyond resveratrol, which are particularly attractive due to their biological activity. Given the "fresh outlook" about different stilbene-based compounds starting from stilbenoids with particular regard to isorhapontigenin and methoxy- and hydroxyl- analogues, the update about the combretastatins, and the very often overlooked and underestimated benzanilide analogues, we present a new story about this remarkable structure.

More Than Resveratrol: New Insights into Stilbene-Based Compounds

The concept of a scaffold concerns many aspects at different steps on the drug development path. In medicinal chemistry, the choice of relevant "drug-likeness" scaffold is a starting point for the design of the structure dedicated to specific molecular targets. For many years, the chemical uniqueness of the stilbene structure has inspired scientists from different fields such as chemistry, biology, pharmacy, and medicine. In this review, we present the outstanding potential of the stilbene-based derivatives. Naturally occurring stilbenes, together with powerful synthetic chemistry possibilities, may offer an excellent approach for discovering new structures and identifying their therapeutic targets. With the development of scientific tools, sophisticated equipment, and a better understanding of the disease pathogenesis at the molecular level, the stilbene scaffold has moved innovation in science. This paper mainly focuses on the stilbene-based compounds beyond resveratrol, which are particularly attractive due to their biological activity. Given the "fresh outlook" about different stilbene-based compounds starting from stilbenoids with particular regard to isorhapontigenin and methoxy- and hydroxyl- analogues, the update about the combretastatins, and the very often overlooked and underestimated benzanilide analogues, we present a new story about this remarkable structure.

Overcoming the biological barriers in the tumor microenvironment for improving drug delivery and efficacy

The delivery of drugs to tumors by nanoparticles is a rapidly growing field. However, the complex tumor microenvironment (TME) barriers greatly hinder drug delivery to tumors. In this study, we first summarized the barriers in TME, including anomalous vasculature, rigid extracellular matrix, hypoxia, acidic pH, irregular enzyme level, altered metabolism pathway and immunosuppressive conditions. To overcome these barriers, many strategies have been developed, such as modulating TME, active targeting by ligand modification and biomimetic strategies, and TME-responsive drug delivery strategies to improve nanoparticle penetration, cellular uptake and drug release. Although extensive progress has been achieved, there are still many challenges, which are discussed in the last section. Overall, we carefully discuss the landscape of TME, development for improving drug delivery, and challenges that need to be further addressed.