Tumor-Targeted Magnetic Micelles for Magnetic Resonance Imaging, Drug Delivery, and Overcoming Multidrug Resistance

Nasopharyngeal carcinoma (NPC) is prevalent in Southern China. Unfortunately, current treatments encounter multidrug resistance (MDR). Overexpression of P-glycoprotein (P-gp), resulting in the efflux of chemotherapy drugs, is one of the significant mechanisms causing MDR. d-α-Tocopheryl poly(ethylene glycol) 1000 succinate (TPGS) has been demonstrated to effectively inhibit P-gp expression. The objectives of this study are to improve tumor MRI imaging, optimize docetaxel (DOC) administration, and target P-gp to overcome NPC resistance. Multifunctional micelles of TPGS (MM@DOC), loaded with magnetic nanoparticles, were synthesized for the targeted delivery of the first-line anticancer drug. MM@DOC exhibited greater toxicity and induced higher levels of apoptosis in DOC-resistant NPC cells (C666-1/DOC) compared to DOC. MM@DOC loaded with magnetic nanoparticles improved the quality of tumor MRI imaging. MM@DOC also demonstrated significant antitumor effects in nude mice with C666-1/DOC NPC. In conclusion, MM@DOC exhibited promising inhibitory effects on resistant tumors both in vitro and in vivo, optimized tumor MRI imaging, and showed great potential in drug delivery and overcoming resistance.

Charge reversible hyaluronic acid-based drug delivery system with pH-responsive dissociation for enhanced drug delivery

Improving the efficiency of drug delivery is one of the most important goals in the field of drug delivery. One strategy for drug delivery efficiency is to make the drug delivery system capable of charge reversal. In this study, we used hyaluronic acid (HA) as the skeleton to anchor dimethylmaleic anhydride-modified polylysine (PLL-DMMA) and N-(3-Aminopropyl)-imidazole (IMI) to construct a pH-sensitive (IMI/Zn2+)-HA-PLL-DMMA system via Zn coordination. The (IMI/Zn2+)-HA-PLL-DMMA system can detach DMMA moieties and expose PLL with a positive charge in the acidic tumor microenvironment (TME), which enhances cellular uptake in cancer cells through charge reversal. Once the drug-loaded (IMI/Zn2+)-HA-PLL-DMMA enters cancer cells, it specifically responds and disassembles in the acidic TME, resulting in drug release and inhibition of cancer cell viability. The (IMI/Zn2+)-HA-PLL-DMMA system is designed to regulate drug release behavior with Zn2+ and IMI groups as control units. The HA-based system shows synergistic selective drug delivery in suppressing tumor cells and has potential in cancer therapy.

Tumor microenvironment-responsive cell-penetrating peptides: Design principle and precision delivery

Cell-penetrating peptides (CPPs) are promising vehicles for intracellular delivery of different cargoes. Although various CPPs are designed for targeted delivery of nanomedicines and anticancer drugs, their clinical approval is hampered by a lack of selectivity. In recent years, new approaches have been explored to address this drawback, and distinct strategies for tumor microenvironment (TME)-responsive activation have been developed. In this review, we first introduce the cellular uptake mechanisms of CPPs. We next extensively discuss the design principles and precision delivery of TME-responsive CPPs. Nine kinds of single stimulus-responsive CPPs, five kinds of multiple stimuli-responsive CPPs, three kinds of TME-responsive targeting CPPs, and two kinds of reversibly activatable CPPs (RACPPs) are systemically summarized. Then, TME-responsive CPPs for nanomedical applications are further discussed. Finally, we describe the translational applications of TME-responsive CPPs for anticancer drug delivery. These commentaries provide an insight into the design of next-generation activatable CPPs (ACPPs) for selective delivery of nanomedicines and anticancer drugs.

Artesunate carriers induced ferroptosis to overcome biological barriers for anti-cancer

Artesunate (ART) has potent anticancer activity but it suffers from poor stability and low bioavailability in vivo due to the special endoperoxide moiety in the molecules. In this work, we fabricated programmable enzyme/reactive oxygen species (ROS) responsive ART complex carriers with size and charge adaptive regulation in order to improve stability and overcome biochemical hurdles of solid tumor. The complex carries (ART/AA-PAMAM@HA) were created by electrostatic interaction between dendrimer-ART/arachidonic acid (AA) (ART/AA-PAMAM) and hyaluronic acid (HA), which can proactively penetrate deeply into tumors and selective drug release. Specifically, ART induced Fenton reaction and produced a mass of ROS and lipid peroxides (LPO), leading to the depressing of GSH level and glutathione peroxidase 4 (GPX4) activity. Meanwhile, exogenous AA further promoted the accumulation of LPO by cascade regulating ferroptosis pathway. In the anti-tumor efficacy in vivo, the tumor inhibition ratio was achieved to 46.92%. This work shows a new anti-tumor strategy triggering ferroptosis via regulating redox homeostasis.

Emerging nanotechnology-based therapeutics to combat multidrug-resistant cancer

Cancer often develops multidrug resistance (MDR) when cancer cells become resistant to numerous structurally and functionally different chemotherapeutic agents. MDR is considered one of the principal reasons for the failure of many forms of clinical chemotherapy. Several factors are involved in the development of MDR including increased expression of efflux transporters, the tumor microenvironment, changes in molecular targets and the activity of cancer stem cells. Recently, researchers have designed and developed a number of small molecule inhibitors and derivatives of natural compounds to overcome various mechanisms of clinical MDR. Unfortunately, most of the chemosensitizing approaches have failed in clinical trials due to non-specific interactions and adverse side effects at pharmacologically effective concentrations. Nanomedicine approaches provide an efficient drug delivery platform to overcome the limitations of conventional chemotherapy and improve therapeutic effectiveness. Multifunctional nanomaterials have been found to facilitate drug delivery by improving bioavailability and pharmacokinetics, enhancing the therapeutic efficacy of chemotherapeutic drugs to overcome MDR. In this review article, we discuss the major factors contributing to MDR and the limitations of existing chemotherapy- and nanocarrier-based drug delivery systems to overcome clinical MDR mechanisms. We critically review recent nanotechnology-based approaches to combat tumor heterogeneity, drug efflux mechanisms, DNA repair and apoptotic machineries to overcome clinical MDR. Recent successful therapies of this nature include liposomal nanoformulations, cRGDY-PEG-Cy5.5-Carbon dots and Cds/ZnS core–shell quantum dots that have been employed for the effective treatment of various cancer sub-types including small cell lung, head and neck and breast cancers.

Chitosan derivatives functionalized dual ROS-responsive nanocarriers to enhance synergistic oxidation-chemotherapy

The efficient triggering of prodrug release has become a challengeable task for stimuli-responsive nanomedicine utilized in cancer therapy due to the subtle differences between normal and tumor tissues and heterogeneity. In this work, a dual ROS-responsive nanocarriers with the ability to self-regulate the ROS level was constructed, which could gradually respond to the endogenous ROS to achieve effective, hierarchical and specific drug release in cancer cells. In brief, DOX was conjugated with MSNs via thioketal bonds and loaded with β-Lapachone. TPP modified chitosan was then coated to fabricate nanocarriers for mitochondria-specific delivery. The resultant nanocarriers respond to the endogenous ROS and release Lap specifically in cancer cells. Subsequently, the released Lap self-regulated the ROS level, resulting in the specific DOX release and mitochondrial damage in situ, enhancing synergistic oxidation-chemotherapy. The tumor inhibition Ratio was achieved to 78.49%. The multi-functional platform provides a novel remote drug delivery system in vivo.

Cell-penetrating peptides in protein mimicry and cancer therapeutics

Extensive research has been undertaken in the pursuit of anticancer therapeutics. Many anticancer drugs require specificity of delivery to cancer cells, whilst sparing healthy tissue. Cell-penetrating peptides (CPPs), now well established as facilitators of intracellular delivery, have in recent years advanced to incorporate target specificity and thus possess great potential for the targeted delivery of anticancer cargoes. Though none have yet been approved for clinical use, this novel technology has already entered clinical trials. In this review we present CPPs, discuss their classification, mechanisms of cargo internalization and highlight strategies for conjugation to anticancer moieties including their incorporation into therapeutic proteins. As the mainstay of this review, strategies to build specificity into tumor targeting CPP constructs through exploitation of the tumor microenvironment and the use of tumor homing peptides are discussed, whilst acknowledging the extensive contribution made by CPP constructs to target specific protein-protein interactions integral to intracellular signaling pathways associated with tumor cell survival and progression. Finally, antibody/antigen CPP conjugates and their potential roles in cancer immunotherapy and diagnostics are considered. In summary, this review aims to harness the potential of CPP-aided drug delivery for future cancer therapies and diagnostics whilst highlighting some of the most recent achievements in selective delivery of anticancer drugs, including cytostatic drugs, to a range of tumor cells both in vitro and in vivo.

Nanotherapeutics approaches to overcome P-glycoprotein-mediated multi-drug resistance in cancer

Multidrug resistance (MDR) in cancer chemotherapy is a growing concern for medical practitioners. P-glycoprotein (P-gp) overexpression is one of the major reasons for multidrug resistance in cancer chemotherapy. The P-gp overexpression in cancer cells depends on several factors like adenosine triphosphate (ATP) hydrolysis, hypoxia-inducible factor 1 alpha (HIF-1α), and drug physicochemical properties such as lipophilicity, molecular weight, and molecular size. Further multiple exposures of anticancer drugs to the P-gp efflux protein cause acquired P-gp overexpression. Unique structural and functional characteristics of nanotechnology-based drug delivery systems provide opportunities to circumvent P-gp mediated MDR. The primary mechanism behind the nanocarrier systems in P-gp inhibition includes: bypassing or inhibiting the P-gp efflux pump to combat MDR. In this review, we discuss the role of P-gp in MDR and highlight the recent progress in different nanocarriers to overcome P-gp mediated MDR in terms of their limitations and potentials.

Brefeldin A delivery nanomicelles in hepatocellular carcinoma therapy: Characterization, cytotoxic evaluation in vitro, and antitumor efficiency in vivo

Hepatocellular carcinoma (HCC) is one of the major cancers with high mortality rate. Traditional drugs used in clinic are usually limited by the drug resistance and side effect and novel agents are still needed. Macrolide brefeldin A (BFA) is a well-known lead compound in cancer chemotherapy, however, with poor solubility and instability. In this study, to overcome these disadvantages, BFA was encapsulated in mixed nanomicelles based on TPGS and F127 copolymers (M-BFA). M-BFA was conferred high solubility, colloidal stability, and capability of sustained release of intact BFA. In vitro, M-BFA markedly inhibited the proliferation, induced G0/G1 phase arrest, and caspase-dependent apoptosis in human liver carcinoma HepG2 cells. Moreover, M-BFA also induced autophagic cell death via Akt/mTOR and ERK pathways. In HepG2 tumor-bearing xenograft mice, indocyanine green (ICG) as a fluorescent probe loaded in M-BFA distributed to the tumor tissue rapidly, prolonged the blood circulation, and improved the tumor accumulation capacity. More importantly, M-BFA (10 mg/kg) dramatically delayed the tumor progression and induced extensive necrosis of the tumor tissues. Taken together, the present work suggests that M-BFA has promising potential in HCC therapy.

Nanoplatform-based natural products co-delivery system to surmount cancer multidrug-resistant

The emergence of multidrug resistance (MDR) in malignant tumors is the primary reason for invalid chemotherapy. Antitumor drugs are often adversely affected by the MDR of tumor cells. Treatments using conventional drugs, which have specific drug targets, hardly regulate the complex signaling pathway of MDR cells because of the complex formation mechanism of MDR. However, natural products have positive advantages, such as high efficiency, low toxicity, and ability to target multiple mechanism pathways associated with MDR. Natural products, as MDR reversal agents, synergize with chemotherapeutics and enhance the sensitivity of tumor cells to chemotherapeutics, and the co-delivery of natural products and antitumor drugs with nanocarriers maximizes the synergistic effects against MDR in tumor cells. This review summarizes the molecular mechanisms of MDR, the advantages of natural products combined with chemotherapeutics in offsetting complicated MDR mechanisms, and the types and mechanisms of natural products that are potential MDR reversal modulators. Meanwhile, aiming at the low bioavailability of cocktail combined natural products and chemotherapeutic in vivo, the advantages of nanoplatform-based co-delivery system and recent research developments are illustrated on the basis of our previous research. Finally, prospective horizons are analyzed, which are expected to considerably improve the nano-co-delivery of natural products and chemotherapeutic systems for MDR reversal in cancer.