Self-Assembled Redox Dual-Responsive Prodrug-Nanosystem Formed by Single Thioether-Bridged Paclitaxel-Fatty Acid Conjugate for Cancer Chemotherapy

Prodrug-based self-assembled nanoparticles formed by 3′,5′-dioleoyl floxuridine for cancer chemotherapy

Amphiphilic prodrug molecules (3′,5′-dioleoyl floxuridine, DOF) were constructed to form prodrug nanoparticles (DOF NPs) through a self-assembly process in water. The DOF NPs were easily prepared, relatively stable, and displayed improved anti-tumor activity.

A Compressive Review about Taxol®: History and Future Challenges

Taxol^®, which is also known as paclitaxel, is a chemotherapeutic agent widely used to treat different cancers. Since the discovery of its antitumoral activity, Taxol^® has been used to treat over one million patients, making it one of the most widely employed antitumoral drugs. Taxol^® was the first microtubule targeting agent described in the literature, with its main mechanism of action consisting of the disruption of microtubule dynamics, thus inducing mitotic arrest and cell death. However, secondary mechanisms for achieving apoptosis have also been demonstrated. Despite its wide use, Taxol^® has certain disadvantages. The main challenges facing Taxol^® are the need to find an environmentally sustainable production method based on the use of microorganisms, increase its bioavailability without exerting adverse effects on the health of patients and minimize the resistance presented by a high percentage of cells treated with paclitaxel. This review details, in a succinct manner, the main aspects of this important drug, from its discovery to the present day. We highlight the main challenges that must be faced in the coming years, in order to increase the effectiveness of Taxol^® as an anticancer agent.

Regulation of Selenium/Sulfur Interactions to Enhance Chemopreventive Effects: Lessons to Learn from Brassicaceae

Selenium (Se) is an essential trace element, which represents an integral part of glutathione peroxidase and other selenoproteins involved in the protection of cells against oxidative damage. Selenomethionine (SeMet), selenocysteine (SeCys), and methylselenocysteine (MeSeCys) are the forms of Se that occur in living systems. Se-containing compounds have been found to reduce carcinogenesis of animal models, and dietary supplemental Se might decrease cancer risk. Se is mainly taken up by plant roots in the form of selenate via high-affinity sulfate transporters. Consequently, owing to the chemical similarity between Se and sulfur (S), the availability of S plays a key role in Se accumulation owing to competition effects in absorption, translocation, and assimilation. Moreover, naturally occurring S-containing compounds have proven to exhibit anticancer potential, in addition to other bioactivities. Therefore, it is important to understand the interaction between Se and S, which depends on Se/S ratio in the plant or/and in the growth medium. Brassicaceae (also known as cabbage or mustard family) is an important family of flowering plants that are grown worldwide and have a vital role in agriculture and populations’ health. In this review we discuss the distribution and further interactions between S and Se in Brassicaceae and provide several examples of Se or Se/S biofortifications’ experiments in brassica vegetables that induced the chemopreventive effects of these crops by enhancing the production of Se- or/and S-containing natural compounds. Extensive further research is required to understand Se/S uptake, translocation, and assimilation and to investigate their potential role in producing anticancer drugs.

Engineering Prodrug Nanomedicine for Cancer Immunotherapy

Immunotherapy has shifted the clinical paradigm of cancer management. However, despite promising initial progress, immunotherapeutic approaches to cancer still suffer from relatively low response rates and the possibility of severe side effects, likely due to the low inherent immunogenicity of tumor cells, the immunosuppressive tumor microenvironment, and significant inter- and intratumoral heterogeneity. Recently, nanoformulations of prodrugs have been explored as a means to enhance cancer immunotherapy by simultaneously eliciting antitumor immune responses and reversing local immunosuppression. Prodrug nanomedicines, which integrate engineering advances in chemistry, oncoimmunology, and material science, are rationally designed through chemically modifying small molecule drugs, peptides, or antibodies to yield increased bioavailability and spatiotemporal control of drug release and activation at the target sites. Such strategies can help reduce adverse effects and enable codelivery of multiple immune modulators to yield synergistic cancer immunotherapy. In this review article, recent advances and translational challenges facing prodrug nanomedicines for cancer immunotherapy are overviewed. Last, key considerations are outlined for future efforts to advance prodrug nanomedicines aimed to improve antitumor immune responses and combat immune tolerogenic microenvironments.

Endogenous Stimuli-Responsive DNA Nanostructures Toward Cancer Theranostics

Nanostructures specifically responsive to endogenous biomolecules hold great potential in accurate diagnosis and precision therapy of cancers. In the pool of nanostructures with responsiveness to unique triggers, nanomaterials derived from DNA self-assembly have drawn particular attention due to their intrinsic biocompatibility and structural programmability, enabling the selective bioimaging, and site-specific drug delivery in cancer cells and tumor tissues. In this mini review, we summarize the most recent advances in the development of endogenous stimuli-responsive DNA nanostructures featured with precise self-assembly, targeted delivery, and controlled drug release for cancer theranostics. This mini review briefly discusses the diverse dynamic DNA nanostructures aiming at bioimaging and biomedicine, including DNA self-assembling materials, DNA origami structures, DNA hydrogels, etc. We then elaborate the working principles of DNA nanostructures activated by biomarkers (e.g., miRNA, mRNA, and proteins) in tumor cells and microenvironments of tumor tissue (e.g., pH, ATP, and redox gradient). Subsequently, applications of the endogenous stimuli-responsive DNA nanostructures in biological imaging probes for detecting cancer hallmarks as well as intelligent carriers for drug release in vivo are discussed. In the end, we highlight the current challenges of DNA nanotechnology and the further development of this promising research direction.

Microenvironment-Triggered Degradable Hydrogel for Imaging Diagnosis and Combined Treatment of Intraocular Choroidal Melanoma

Human choroidal melanoma (HCM) is one of the most common primary intraocular tumors and easily provokes liver metastases owing to the lack of sensitive and noninvasive therapeutic methods. Concerning the imaging diagnostics and therapeutic predicaments for choroidal melanoma, we designed microenvironment-triggered degradable hydrogels (RENP-ICG@PNIPAM:Dox-FA) based on ultrasmall (<5 nm) rare-earth nanoparticles (RENPs) with enhanced NIR-II luminescence. The ultrasmall diameter can significantly enhance the NIR-II luminescence performance of RENPs. RENPs were encapsulated by a dual-response PNIPAM hydrogel, which could release drug by responding to heat energy and glutathione under the tumor microenvironment. The in vitro/in vivo NIR-II imaging detection and antitumor activity were also compared systematically after different treatment conditions on ocular choroidal melanoma-1 cells and tumor-bearing mice, respectively. Besides, the degradability of the hydrogel composites under physiological conditions could be conducive to enhance the photothermal-chemotherapeutic effect and alleviate long-term biological toxicity. Our work on the microenvironment-triggered hydrogels with enhanced NIR imaging and easy metabolism may provide a promising strategy for sensitive and noninvasive imaging and phototherapy in ocular tumors.

Advances and perspectives in carrier-free nanodrugs for cancer chemo-monotherapy and combination therapy

Nanocarrier-based drug delivery systems hold impressive promise for biomedical application because of their excellent water dispersibility, prolonged blood circulation time, increased drug accumulation in tumors, and potential in combination therapeutics. However, most nanocarriers suffer from low drug-loading efficiency, poor therapeutic effectiveness, potential systematic toxicity, and unstable metabolism. As an alternative, carrier-free nanodrugs, completely formulated with one or more drugs, have attracted increasing attention in cancer therapy due to their advantage of improved pharmacodynamics/pharmacokinetics, reduced toxicity, and high drug-loading. In recent years, carrier-free nanodrugs have contributed to progress in a variety of therapeutic modalities. In this review, different common strategies for carrier-free nanodrugs preparation are first summarized, mainly including nanoprecipitation, template-assisted nanoprecipitation, thin-film hydration, spray-drying technique, supercritical fluid (SCF) technique, and wet media milling. Then we describe the recently reported carrier-free nanodrugs for cancer chemo-monotherapy or combination therapy. The advantages of anti-cancer drugs combined with other chemotherapeutic, photosensitizers, photothermal, immunotherapeutic or gene drugs have been demonstrated. Finally, a future perspective is introduced to highlight the existing challenges and possible solutions toward clinical application of currently developed carrier-free nanodrugs, which may be instructive to the design of effective carrier-free regimens in the future.

Miktoarm Star Polymers with Environment-Selective ROS/GSH Responsive Locations: From Modular Synthesis to Tuned Drug Release through Micellar Partial Corona Shedding and/or Core Disassembly

Branched architectures with asymmetric polymeric arms provide an advantageous platform for the construction of tailored nanocarriers for therapeutic interventions. Simple and adaptable synthetic methodologies to amphiphilic miktoarm star polymers have been developed in which spatial location of reactive oxygen species (ROS) and glutathione (GSH) responsive entities is articulated to be on the corona shell surface or inside the core. The design of such architectures is facilitated through versatile building blocks and selected combinations of ring-opening polymerization, Steglich esterification, and alkyne-azide click reactions. Soft nanoparticles from aqueous self-assembly of these stimuli responsive miktoarm stars have low critical micelle concentrations and high drug loading efficiencies. Partial corona shedding upon response to ROS is accompanied by an increase in drug release, without significant changes to overall micelle morphology. The location of the GSH responsive unit at the core leads to micelle disassembly and complete drug release. Curcumin loaded soft nanoparticles show higher efficiencies in preventing ROS generation in extracellular and cellular environments, and in ROS scavenging in human glioblastoma cells. The ease in synthetic elaboration and an understanding of structure-property relationships in stimuli responsive nanoparticles offer a facile venue for well-controlled drug delivery, based on the extra- and intracellular concentrations of ROS and GSH.

Trisulfide bond-mediated doxorubicin dimeric prodrug nanoassemblies with high drug loading, high self-assembly stability, and high tumor selectivity

Rational design of nanoparticulate drug delivery systems (nano-DDS) for efficient cancer therapy is still a challenge, restricted by poor drug loading, poor stability, and poor tumor selectivity. Here, we report that simple insertion of a trisulfide bond can turn doxorubicin homodimeric prodrugs into self-assembled nanoparticles with three benefits: high drug loading (67.24%, w/w), high self-assembly stability, and high tumor selectivity. Compared with disulfide and thioether bonds, the trisulfide bond effectively promotes the self-assembly ability of doxorubicin homodimeric prodrugs, thereby improving the colloidal stability and in vivo fate of prodrug nanoassemblies. The trisulfide bond also shows higher glutathione sensitivity compared to the conventional disulfide bond, and this sensitivity enables efficient tumor-specific drug release. Therefore, trisulfide bond-bridged prodrug nanoassemblies exhibit high selective cytotoxicity on tumor cells compared with normal cells, notably reducing the systemic toxicity of doxorubicin. Our findings provide new insights into the design of advanced redox-sensitive nano-DDS for cancer therapy.

Redox dual-responsive dendrimeric nanoparticles for mutually synergistic chemo-photodynamic therapy to overcome drug resistance

Combination therapy has exhibited crucial potential in the treatment of cancers, especially in drug-resistant cancers. In this work, a novel tumor-targeted, redox dual-responsive and paclitaxel (PTX) loaded nanoparticle based on multifunctional dendrimer and lentinan was developed for combinational chemo-photodynamic therapy of PTX-resistant cancers. The nanoparticles exhibited enhanced cellular uptake and tumor penetration based on phenylboronic acid-sialic acid interactions, and had the ability to control drug release in response to intracellular high concentration of glutathione and H₂O₂. Specifically, light irradiation not only triggered the photodynamic effect of the nanoparticles for prominent photodynamic cytotoxicity, but also resulted in increased internalization and accelerated release of PTX into cytoplasm through the lysosome disruption, as well as the obvious damage to microtubules and actin microfilaments, for drug resistance reversal of A549/T cells. Meanwhile, PTX treatment would arrest cells in G2/M phase, thereby prolonging the period when nuclear membrane is broken down, which further facilitated photosensitizer accumulation in nuclei and improved DNA damage response. Consequently, the combination of PTX and photodynamic treatment lead to excellent antitumor effects to drug-resistant A549/T cells in vitro and in vivo, which provides a new strategy for the design of co-delivery system to overcome drug resistance.

Probing the Superiority of Diselenium Bond on Docetaxel Dimeric Prodrug Nanoassemblies: Small Roles Taking Big Responsibilities

The current state of chemotherapy is far from satisfaction, restricted by the inefficient drug delivery and the off-target toxicity. Prodrug nanoassemblies are emerging as efficient platforms for chemotherapy. Herein, three docetaxel dimeric prodrugs are designed using diselenide bond, disulfide bond, or dicarbide bond as linkages. Interestingly, diselenide bond-bridged dimeric prodrug can self-assemble into stable nanoparticles with impressive high drug loading (≈70%, w/w). Compared with disulfide bond and dicarbide bond, diselenide bond greatly facilitates the self-assembly of dimeric prodrug, and then improves the colloidal stability, blood circulation time, and antitumor efficacy of prodrug nanoassemblies. Furthermore, the redox-sensitive diselenide bond can specifically respond to the overexpressed reactive oxygen species and glutathione in tumor cells, leading to tumor-specific drug release. Therefore, diselenide bond bridged prodrug nanoassemblies exhibit discriminating cytotoxicity between tumor cells and normal cells, significantly alleviating the systemic toxicity of docetaxel. The present work gains in-depth insight into the impact of diselenide bond on the dimeric prodrug nanoassemblies, and provides promising strategies for the rational design of the high efficiency-low toxicity chemotherapeutical nanomedicines.

Carrier-free nanodrugs for safe and effective cancer treatment

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

Dual-responsive doxorubicin-loaded nanomicelles for enhanced cancer therapy

BACKGROUND

The enhancement of tumor retention and cellular uptake of drugs are important factors in maximizing anticancer therapy and minimizing side effects of encapsulated drugs. Herein, a delivery nanoplatform, armed with a pH-triggered charge-reversal capability and self-amplifiable reactive oxygen species (ROS)-induced drug release, is constructed by encapsulating doxorubicin (DOX) in pH/ROS-responsive polymeric micelle.

RESULTS

The surface charge of this system was converted from negative to positive from pH 7.4 to pH 6.8, which facilitated the cellular uptake. In addition, methionine-based system was dissociated in a ROS-rich and acidic intracellular environment, resulting in the release of DOX and α-tocopheryl succinate (TOS). Then, the exposed TOS segments further induced the generation of ROS, leading to self-amplifiable disassembly of the micelles and drug release.

CONCLUSIONS

We confirms efficient DOX delivery into cancer cells, upregulation of tumoral ROS level and induction of the apoptotic capability in vitro. The system exhibits outstanding tumor inhibition capability in vivo, indicating that dual stimuli nano-system has great potential to function as an anticancer drug delivery platform.

Biomedical Application of Reactive Oxygen Species-Responsive Nanocarriers in Cancer, Inflammation, and Neurodegenerative Diseases

Numerous pathological conditions, including cancer, inflammatory diseases, and neurodegenerative diseases, are accompanied by overproduction of reactive oxygen species (ROS). This makes ROS vital flagging molecules in disease pathology. ROS-responsive drug delivery platforms have been developed. Nanotechnology has been broadly applied in the field of biomedicine leading to the progress of ROS-responsive nanoparticles. In this review, we focused on the production and physiological/pathophysiological impact of ROS. Particular emphasis is put on the mechanisms and effects of abnormal ROS levels on oxidative stress diseases, including cancer, inflammatory disease, and neurodegenerative diseases. Finally, we summarized the potential biomedical applications of ROS-responsive nanocarriers in these oxidative stress diseases. We provide insights that will help in the designing of new ROS-responsive nanocarriers for various applications.

Stimulus-Responsive Nanomedicines for Disease Diagnosis and Treatment

Stimulus-responsive drug delivery systems generally aim to release the active pharmaceutical ingredient (API) in response to specific conditions and have recently been explored for disease treatments. These approaches can also be extended to molecular imaging to report on disease diagnosis and management. The stimuli used for activation are based on differences between the environment of the diseased or targeted sites, and normal tissues. Endogenous stimuli include pH, redox reactions, enzymatic activity, temperature and others. Exogenous site-specific stimuli include the use of magnetic fields, light, ultrasound and others. These endogenous or exogenous stimuli lead to structural changes or cleavage of the cargo carrier, leading to release of the API. A wide variety of stimulus-responsive systems have been developed-responsive to both a single stimulus or multiple stimuli-and represent a theranostic tool for disease treatment. In this review, stimuli commonly used in the development of theranostic nanoplatforms are enumerated. An emphasis on chemical structure and property relationships is provided, aiming to focus on insights for the design of stimulus-responsive delivery systems. Several examples of theranostic applications of these stimulus-responsive nanomedicines are discussed.

Remote loading paclitaxel-doxorubicin prodrug into liposomes for cancer combination therapy

The combination of paclitaxel (PTX) and doxorubicin (DOX) has been widely used in the clinic. However, it remains unsatisfied due to the generation of severe toxicity. Previously, we have successfully synthesized a prodrug PTX-S-DOX (PSD). The prodrug displayed comparable in vitro cytotoxicity compared with the mixture of free PTX and DOX. Thus, we speculated that it could be promising to improve the anti-cancer effect and reduce adverse effects by improving the pharmacokinetics behavior of PSD and enhancing tumor accumulation. Due to the fact that copper ions (Cu²⁺) could coordinate with the anthracene nucleus of DOX, we speculate that the prodrug PSD could be actively loaded into liposomes by Cu²⁺ gradient. Hence, we designed a remote loading liposomal formulation of PSD (PSD LPs) for combination chemotherapy. The prepared PSD LPs displayed extended blood circulation, improved tumor accumulation, and more significant anti-tumor efficacy compared with PSD NPs. Furthermore, PSD LPs exhibited reduced cardiotoxicity and kidney damage compared with the physical mixture of Taxol and Doxil, indicating better safety. Therefore, this novel nano-platform provides a strategy to deliver doxorubicin with other poorly soluble antineoplastic drugs for combination therapy with high efficacy and low toxicity.

Oxidation-strengthened disulfide-bridged prodrug nanoplatforms with cascade facilitated drug release for synergetic photochemotherapy

One of the major barriers in utilizing prodrug nanocarriers for cancer therapy is the slow release of parent drug in tumors. Tumor cells generally display the higher oxidative level than normal cells, and also displayed the heterogeneity in terms of redox homeostasis level. We previously found that the disulfide bond-linkage demonstrates surprising oxidation-sensitivity to form the hydrophilic sulfoxide and sulphone groups. Herein, we develop oxidation-strengthened prodrug nanosystem loaded with pyropheophorbide a (PPa) to achieve light-activatable cascade drug release and enhance therapeutic efficacy. The disulfide bond-driven prodrug nanosystems not only respond to the redox-heterogeneity in tumor, but also respond to the exogenous oxidant (singlet oxygen) elicited by photosensitizers. Once the prodrug nanoparticles (NPs) are activated under irradiation, they would undergo an oxidative self-strengthened process, resulting in a facilitated drug cascade release. The IC50 value of the PPa@PTX-S-S NPs without irradiation was 2-fold higher than those of NPs plus irradiation. In vivo, the PPa@PTX prodrug NPs display prolonged systemic circulation and increased accumulation in tumor site. The PPa@PTX-S-S NPs showed much higher efficiency than free PTX or the PPa@PTX-C-C NPs to suppress the growth of 4T1 tumors. Therefore, this novel oxidation-strengthened disulfide-bridged prodrug-nanosystem has a great potential in the enhanced efficacy of cancer synergetic photochemotherapy.

Miktoarm Star Polymers: Branched Architectures in Drug Delivery

Delivering active pharmaceutical agents to disease sites using soft polymeric nanoparticles continues to be a topical area of research. It is becoming increasingly evident that the composition of amphiphilic macromolecules plays a significant role in developing efficient nanoformulations. Branched architectures with asymmetric polymeric arms emanating from a central core junction have provided a pivotal venue to tailor their key parameters. The build-up of miktoarm stars offers vast polymer arm tunability, aiding in the development of macromolecules with adjustable properties, and allows facile inclusion of endogenous stimulus-responsive entities. Miktoarm star-based micelles have been demonstrated to exhibit denser coronae, very low critical micelle concentrations, high drug loading contents, and sustained drug release profiles. With significant advances in chemical methodologies, synthetic articulation of miktoarm polymer architecture, and determination of their structure-property relationships, are now becoming streamlined. This is helping advance their implementation into formulating efficient therapeutic interventions. This review brings into focus the important discoveries in the syntheses of miktoarm stars of varied compositions, their aqueous self-assembly, and contributions their formulations are making in advancing the field of drug delivery.

Kinetic stability-driven cytotoxicity of small-molecule prodrug nanoassemblies

Nanoassemblies (NAs) of small-molecule lipophilic prodrugs have been widely investigated for efficient drug delivery in cancer therapy, but their kinetic stability has not attracted sufficient attention in the past studies. Herein, we reported that kinetic stability has a great influence on the drug release from the NAs of lipophilic prodrugs in physiologically relevant media. Based on the co-assembled FRET nanosystems of two lipophilic fluorescent prodrugs, we demonstrated that NAs constructed by lipophilic prodrugs containing shorter alkyl chains or those with higher unsaturated degrees displayed poorer kinetic stability, which further resulted in remarkably faster drug release in mouse plasma and various tissue homogenates. More importantly, these kinetically unstable NAs also induced rapid intracellular drug release, resulting in much more potent cytotoxicity. These findings highlight the crucial role of kinetic stability in determining the drug release from the NAs of lipophilic prodrugs, which would effectively guide their rational designs for cancer therapy.

Hierarchical integration of degradable mesoporous silica nanoreservoirs and supramolecular dendrimer complex as a general-purpose tumor-targeted biomimetic nanoplatform for gene/small-molecule anticancer drug co-delivery

Biomacromolecule therapeutic systems are intrinsically susceptible to degradation and denaturation. Nanoformulations are promising delivery vehicles for therapeutic biomacromolecules (antibodies, genes and so on). However, their applications in these areas still face many challenges including in vivo stability, premature leakage and accurate tumor recognition. In this study, a generally applicable new strategy for tumor-targeted delivery of biomacromolecules was developed through the hierarchical integration of degradable large-pore dendritic mesoporous silica nanoparticles (dMSNs) and cyclodextrin-modified polyamidoamine (PAMAM-CD) dendrimers. The orifice rim of the dMSNs was modified with ROS-responsive nitrophenyl-benzyl-carbonate (NBC) groups while disulfide-bonded azido ligands were subsequently grafted onto the inner channel walls via heterogeneous functionalization. The PAMAM-CD was then interred into the dendritic pores via click reactions and supramolecularly loaded with archetypal hydrophobic small-molecule anticancer model drug (SN-38) and therapeutic model gene (Bcl-2 siRNA), after which dMSNs were eventually coated with a 4T1 cancer cell membrane (CCM). Experimental evidence demonstrated that the synthesized nanocarriers could efficiently deliver therapeutic cargos to target cancer cells and release them in the tumor cytosol in a cascade-responsive manner. This biomimetic nanoplatform presents a novel strategy to efficiently deliver biomolecular therapeutics in a tumor-targeted manner.

An ultra-long circulating nanoparticle for reviving a highly selective BCR-ABL inhibitor in long-term effective and safe treatment of chronic myeloid leukemia

Nanotechnology has demonstrated great promise for the development of more effective and safer cancer therapies. We recently developed a highly selective inhibitor of BCR-ABL fusion tyrosine kinase for chronic myeloid leukemia (CML). However, the poor drug-like properties were hurdles to its further clinical development. Herein, we re-investigate it by conjugating an amphiphilic polymer and self-assembling into a nanoparticle (NP) with a high loading (~10.3%). The formulation greatly improved its solubility and drastically extended its circulation half-life from ~5.3 to ~117 h (>20-fold). In the 150 days long-term engraftment model experiment, long intravenous dosing intervals of the NPs (every 4 or 8 days) exhibited much better survival and negligible toxicities as compared to daily oral administration of the inhibitor. Moreover, the NPs showed excellent inhibition of tumor growth in the subcutaneous xenograft model. All results suggest that the ultra-long circulating pro-drug NP may provide an effective and safe therapeutic strategy for BCR-ABL-positive CML.

Emerging insights on drug delivery by fatty acid mediated synthesis of lipophilic prodrugs as novel nanomedicines

Many drug molecules that are currently in the market suffer from short half-life, poor absorption, low specificity, rapid degradation, and resistance development. The design and development of lipophilic prodrugs can provide numerous benefits to overcome these challenges. Fatty acids (FAs), which are lipophilic biomolecules constituted of essential components of the living cells, carry out many necessary functions required for the development of efficient prodrugs. Chemical conjugation of FAs to drug molecules may change their pharmacodynamics/pharmacokinetics in vivo and even their toxicity profile. Well-designed FA-based prodrugs can also present other benefits, such as improved oral bioavailability, promoted tumor targeting efficiency, controlled drug release, and enhanced cellular penetration, leading to improved therapeutic efficacy. In this review, we discuss diverse drug molecules conjugated to various unsaturated FAs. Furthermore, various drug-FA conjugates loaded into various nanostructure delivery systems, including liposomes, solid lipid nanoparticles, emulsions, nano-assemblies, micelles, and polymeric nanoparticles, are reviewed. The present review aims to inspire readers to explore new avenues in prodrug design based on the various FAs with or without nanostructured delivery systems.

Dimeric prodrug-based nanomedicines for cancer therapy

With the rapid development of conjugation chemistry and biomedical nanotechnology, prodrug-based nanosystems (PNS) have emerged as promising drug delivery nanoplatforms. Dimeric prodrug, as an emerging branch of prodrug, has been widely investigated by covalently conjugating two same or different drug molecules. In recent years, great progress has been made in dimeric prodrug-based nanosystems (DPNS) for cancer therapy. Many advantages offered by DPNS have significantly facilitated the delivery efficiency of anticancer drugs, such as high drug loading capacity, favorable pharmacokinetics, tumor stimuli-sensitive drug release and facile combination theranostics. Given the rapid developments in this field, we here outline the latest updates of DPNS in cancer treatment, focusing on dimeric prodrug-encapsulated nanosystems, dimeric prodrug-nanoassemblies and tumor stimuli-responsive DPNS. Moreover, the design principle, advantages and challenges of DPNS for clinical cancer therapy are also highlighted.

Oleic Acid Copolymer as A Novel Upconversion Nanomaterial to Make Doxorubicin-Loaded Nanomicelles with Dual Responsiveness to pH and NIR

Oleic acid (OA) as main component of plant oil is an important solvent but seldom used in the nanocarrier of anticancer drugs because of strong hydrophobicity and little drug release. In order to develop a new type of OA nanomaterial with dual responses to pH and near infrared light (NIR) to achieve the intelligent delivery of anticancer drugs. The novel OA copolymer (mPEG-PEI-(NBS, OA)) was synthesized by grafting OA and o-nitrobenzyl succinate (NBS) onto mPEGylated polyethyleneimine (mPEG-PEI) by amidation reaction. It was further conjugated with NaYF₄:Yb³⁺/Er³⁺ nanoparticles, and encapsulated doxorubicin (DOX) through self-assembly to make upconversion nanomicelles with dual response to pH and NIR. Drug release behavior of DOX, physicochemical characteristics of the nanomicelles were evaluated, along with its cytotoxic profile, as well as the degree of cellular uptake in A549 cells. The encapsulation efficiency and drug loading capacity of DOX in the nanomicelles were 73.84% ± 0.58% and 4.62% ± 0.28%, respectively, and the encapsulated DOX was quickly released in an acidic environment exposed to irradiation at 980 nm. The blank nanomicelles exhibited low cytotoxicity and excellent biocompatibility by MTT assay against A549 cells. The DOX-loaded nanomicelles showed remarkable cytotoxicity to A549 cells under NIR, and promoted the cellular uptake of DOX into the cytoplasm and nucleus of cancer cells. OA copolymer can effectively deliver DOX to cancer cells and achieve tumor targeting through a dual response to pH and NIR.

An exosome-like programmable-bioactivating paclitaxel prodrug nanoplatform for enhanced breast cancer metastasis inhibition

Metastasis is closely associated with high breast cancer mortality. Although nanotechnology-based anti-metastatic treatments have developed rapidly, the anti-metastasis efficiency is still far from satisfactory, mainly due to the poor recognition of circulating tumor cells (CTCs) in blood. Herein, we developed an exosome-like sequential-bioactivating prodrug nanoplatform (EMPCs) to overcome the obstacle. Specifically, the reactive oxygen species (ROS)-responsive thioether-linked paclitaxel-linoleic acid conjugates (PTX-S-LA) and cucurbitacin B (CuB) are co-encapsulated into polymeric micelles, and the nanoparticles are further decorated with exosome membrane (EM). The resulting EMPCs could specifically capture and neutralize CTCs during blood circulation through the high-affinity interaction between cancer cell membrane and homotypic EM. Following cellular uptake, EMPCs first release CuB, remarkably blocking tumor metastasis via downregulation of the FAK/MMP signaling pathway. Moreover, CuB obviously elevates the intracellular oxidative level to induce a sequential bioactivation of ROS-responsive PTX-S-LA. In vitro and in vivo results demonstrate that EMPCs not only exhibit amplified prodrug bioactivation, prolonged blood circulation, selective targeting of homotypic tumor cells, and enhanced tumor penetration, but also suppress tumor metastasis through CTCs clearance and FAK/MMP signaling pathway regulation. This study proposes an integrated approach for mechanism-based inhibition of tumor metastasis and manifests a promising potential of programmable-bioactivating prodrug nanoplatform for cancer metastasis inhibition.

Tumor microenvironment responsive drug delivery systems

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

Emerging nanotherapeutics for antithrombotic treatment

Thrombus causes insufficient blood flow and ischemia damages to brain and heart, leading to life-threatening cardio-cerebrovascular diseases. Development of efficient antithrombotic strategies has long been a high priority, owing to the high morbidity and mortality of thrombotic diseases. With the rapid development of biomedical nanotechnology in diagnosis and treatment of thrombotic disorder, remarkable progresses have been made in antithrombotic nanomedicines in recent years. Herein, we outline the recent advances in this field at the intersection of thrombus theranostics and biomedical nanotechnology. First, thrombus diagnosis techniques based on biomedical nanotechnology are presented. Then, emerging antithrombotic nanotherapeutics are overviewed, including thrombus-targeting strategies, thrombus stimuli-responsive nanosystems and phase transition-driven nanotherapeutics. Furthermore, multifunctional nanosystems for combination theranostics of thrombotic diseases are discussed. Finally, the design considerations, advantages and challenges of these biomedical nanotechnology-driven therapeutics in clinical translation are highlighted.

Nanotherapeutics for Antimetastatic Treatment

Tumor metastases, that is, the development of secondary tumors in organs distant from the primary tumor, and their treatment remain a serious problem in cancer therapy. The unique challenges for tracking and treating tumor metastases lie in the small size, high heterogeneity, and wide dispersion to distant organs of metastases. Recently, nanomedicines, with the capacity to precisely deliver therapeutic agents to both primary and secondary tumors, have demonstrated many potential benefits for metastatic cancer theranostics. Given the remarkable progression in emerging nanotherapeutics for antimetastatic treatment, it is timely to summarize the latest advances in this field. This review highlights the rationale, advantages, and challenges for integrating biomedical nanotechnology with cancer biology to develop antimetastatic nanotherapeutics.

A computer-aided chem-photodynamic drugs self-delivery system for synergistically enhanced cancer therapy

The therapeutic strategy that gives consideration to the combination of photodynamic therapy and chemotherapy, has emerged as a potential development of effective anti-cancer medicine. Nevertheless, co-delivery of photosensitizers (PSs) and chemotherapeutic drugs in traditional carriers still remains great limitations due to low drug loadings and poor biocompatibility. Herein, we have utilized a computer-aided strategy to achieve a desired carrier-free self-delivery of pyropheophorbide a (PPa, a common PS) and podophyllotoxin (PPT, a classical chemotherapeutic drug) for synergistic cancer therapy. First, the computational simulation method identified the similar molecular sizes and rigid molecular structures between two drugs molecules. Based on the molecular docking, the intermolecular interactions were found to include π-π stackings, hydrophobic interactions and hydrogen bonds. Next, both drugs could co-assemble into nanoparticles (NPs) via one-step nanoprecipitation method. The various spectral experiments (UV, IR and FL) were conducted to evaluate the formation mechanism of spherical NPs. Moreover, in vitro and in vivo experiments systematically demonstrated that PPT/PPa NPs not only showed better cellular uptake efficiency, stronger cytotoxicity and higher accumulation in tumor sites, but also exhibited synergistic antitumor effect in female BALB/C bearing-4T1 tumor mice. Such a computer-aided design strategy of chem-photodynamic drugs self-delivery systems pave the way for efficient synergistic cancer therapy.

Self-assembling nanoparticles of dually hydrophobic prodrugs constructed from camptothecin analogue for cancer therapy

Nanomedicines have shown success in cancer therapy in recent years because of their excellent solubility in aqueous solution and drug accumulation through controlled release in tumor tissues, but the preparation of most nanomedicines still requires ionic materials, surfactants or the amphiphilic structure to maintain nanoparticle stability and function. In this study, we developed a couple of novel dually hydrophobic prodrugs (DHPs) by combining two hydrophobic compounds through different linkers and elaborated their self-assembly mechanisms by virtue of computational simulation. Importantly, without using any excipients, FL-2 NPs exhibited significantly prolonged retention in blood circulation and displayed a remarkable anti-tumor effect at very low concentration in vivo. Both DHPs consisted of camptothecin structural analogue(FL118) and a marine natural product (ES-285). Comparative experiments proved that these compounds could quickly form nanoparticles by way of simple preparation and remained relatively stable for long periods in PBS. FL-2 NPs linked with a disulphide bond could rapidly release bioactive FL118 after being triggered by endogenous reductive stimulus to exert anti-cancer effects. Overall, this study provides a new strategy for design of therapeutic nanomedicines consisting of dually hydrophobic molecules for cancer therapy.

In vivo and in vitro evaluation of dihydroartemisinin prodrug nanocomplexes as a nano-drug delivery system: characterization, pharmacokinetics and pharmacodynamics

To develop new, more effective and lower toxicity antitumor dihydroartemisinin (DHA) nanocomplexes, a DHA prodrug synthesized in this study was used to prepare DHA prodrug self-assembled nanocomplexes (DHANPs) by molecular self-assembly technology. The optimization, pharmacokinetics and in vitro and in vivo antitumor efficiency of DHANPs were assessed. The results showed that the entrapment efficiency, drug loading, particle size and zeta potential of the optimized formulation were 92.37 ± 3.68%, 76.98 ± 3.07%, 145.9 ± 2.11 nm and -16.0 ± 0.52 mV, respectively. DHANPs had a uniform size distribution and good stability during storage. The release of DHA prodrugs from DHANPs was slow in a PBS solution (pH 7.4). The pharmacokinetic study indicated that DHANPs could significantly improve the blood concentration of DHA. DHANPs exhibited lower cytotoxicity to 4T1 cells. More importantly, DHANPs could increase the quality life of mice in comparison with that of the DHA solution in 4T1 tumor-bearing mice. In short, the optimized DHA prodrug nanocomplexes show good long-term stability during the experimental time, extend the life-cycle of DHA in rats and can act as a prospective nano-drug delivery system for future artemisinin-based anti-tumor drugs.

Reduction/Oxidation-Responsive Hierarchical Nanoparticles with Self-Driven Degradability for Enhanced Tumor Penetration and Precise Chemotherapy

Deep tumor penetration, long blood circulation, rapid drug release, and sufficient stability are the most concerning dilemmas of nano-drug-delivery systems for efficient chemotherapy. Herein, we develop reduction/oxidation-responsive hierarchical nanoparticles co-encapsulating paclitaxel (PTX) and pH-stimulated hyaluronidase (pSH) to surmount the sequential biological barriers for precise cancer therapy. Poly(ethylene glycol) diamine (PEG-dia) is applied to collaboratively cross-link the shell of nanoparticles self-assembled by a hyaluronic acid-stearic acid conjugate linked via a disulfide bond (HA-SS-SA, HSS) to fabricate the hierarchical nanoparticles (PHSS). The PTX and pSH coloaded hierarchical nanoparticles (PTX/pSH-PHSS) enhance the stability in normal physiological conditions and accelerate drug release at tumorous pH, and highly reductive or oxidative environments. Functionalized with PEG and HA, the hierarchical nanoparticles preferentially prolong the circulation time, accumulate at the tumor site, and enter MDA-MB-231 cells via CD44-mediated endocytosis. Within the acidic tumor micro-environment, pSH would be partially reactivated to decompose the dense tumor extracellular matrix for deep tumor penetration. Interestingly, PTX/pSH-PHSS could be degraded apace by the completely activated pSH within endo/lysosomes and the intracellular redox micro-environment to facilitate drug release to produce the highest tumor inhibition (93.71%) in breast cancer models.

Reduction-sensitive poly(ethylene glycol)-polypeptide conjugate micelles for highly efficient intracellular delivery and enhanced antitumor efficacy of hydroxycamptothecin

The non-specific biodistribution of traditional chemotherapeutic drugs against tumors is the key factor that causes systemic toxicity and hinders their clinical application. In this study, a reduction-sensitive polymer conjugate micelle was manufactured to achieve tumor-specific targeting, reduce toxic side-effects and improve anti-tumor activity of a natural anti-cancer drug, hydroxycamptothecin (HCPT). Therefore, HCPT was conjugated with methoxy-poly(ethylene glycol)-poly(β-benzyl-L-aspartate) (mPEG-PBLA) by a disulfide bond or succinate bond for the first time to obtain the mPEG-PBLA-SS-HCPT (PPSH) and mPEG-PBLA-CC-HCPT (PPCH) that would form micelles after high-speed agitation and dialysis. The PPSH micelles showed an average particle size of 126.3 nm, a low polydispersity index of 0.209, and a negative surface charge of -21.1 mV zeta potential. Transmission electron microscopy showed the PPSH micelles to have spherical morphology. PPSH had a low critical micelle concentration of 1.29 μg ml^-1 with high dilution stability, storage stability and reproducibility. Moreover, the particle size of the PPSH micelles had no significant change after incubation with rat plasma for 72 h, probably resulting in high long circulation in the blood. The PPSH micelles showed significant reduction sensitivity to glutathione. Their sizes increased by 403.2 nm after 24 h post-incubation, and 87.6% drug release was achieved 48 h post-incubation with 40 mM glutathione solutions. The PPSH micelles showed stronger inhibition of HepG2 cells in vitro and growth of H-22 tumor in vivo than the PPCH and HCPT solutions after intravenous injection. The accumulation of PPSH micelles in the tumor tissue contributed to the high anti-tumor effect with little side-effect on the normal tissues. The reduction-sensitive PPSH micelles were a promising carrier of HCPT and other poorly soluble anti-cancer drugs.

Cytochrome P450 enzyme-mediated auto-enhanced photodynamic cancer therapy of co-nanoassembly between clopidogrel and photosensitizer

Reactive oxygen species (ROS)-based photodynamic therapy (PDT) has a widespread application in cancer therapy. Nevertheless, the efficiency of PDT is far from satisfactory. One major impediment is the overexpression of glutathione (GSH) in tumor cells, which could deplete the level of PDT-generated ROS. Herein, we develop a novel type of cytochrome P450 enzyme-mediated auto-enhanced photodynamic co-nanoassembly between clopidogrel (CPG) and photosensitizer pyropheophorbide a (PPa).

Methods: In this work, we prepare the co-assembled nanoparticles of CPG and PPa (CPG/PPa NPs) by using one-step precipitation method. The assembly mechanism, drug release behavior, GSH consumption, ROS generation, cellular uptake, cytotoxicity of CPG/PPa NPs are investigated in vitro. The mice bearing 4T1 tumor are employed to evaluate in vivo biodistribution and anti-tumor effect of CPG/PPa NPs.

Results: Such CPG/PPa NPs could disrupt the intracellular redox homeostasis, resulting from the elimination of GSH by CPG active metabolite mediated by cytochrome P450 enzyme (CYP2C19). The in vivo assays reveal that CPG/PPa NPs not only increase the drug accumulation in tumor sites but also significantly suppress tumor growth in BALB/c mice bearing 4T1 tumor. With CPG-mediated GSH consumption and PPa-triggered ROS generation, CPG/PPa NPs show the enhanced PDT treatment effect by breaking intracellular redox balance.

Conclusion: Our findings provide a valuable knowledge for the rational design of the PDT-based combinational cancer therapy.

Enhanced in vitro antitumor efficacy of a polyunsaturated fatty acid-conjugated pH-responsive self-assembled ion-pairing liposome-encapsulated prodrug

The development of clinical chemotherapeutics is always challenging due to the toxicity and side effects of drugs not only for tumor cells but also for normal cells. Therefore, nano-drug delivery systems and prodrug strategies have been applied to address this challenge. Herein, we report a liposome-encapsulated small-molecule prodrug nanosystem, self-assembled by doxorubicin (DOX) and mixed polyunsaturated fatty acid (MPUFA) ion-pairing (MPUFAs-DOX@Liposomes), which has a high omega-3 PUFA content. The increased lipophilicity of ion-paired MPUFAs-DOX can significantly improve the drug loading efficiency (∼97%). Electrostatic interaction, the hydrophobic effect and hydrogen bonding between the ion-pairing agents led to superior pH-responsive release of DOX from liposomes over DOX-loaded liposomes (DOX@Liposomes), with a more rapid release rate at pH 5.0 than at pH 7.4, which is beneficial for decreasing the toxicity of DOX under physiological conditions. Finally, the in vitro antitumor effects were investigated for two tumor cell types, A549 and MCF-7, and the results demonstrated that MPUFAs-DOX@Liposomes showed the highest cytotoxicity compared with free DOX and DOX@Liposomes because of the ready uptake under the effect of PUFAs. Hence, liposomes loaded with ion-paired MPUFAs-DOX is a promising formulation for combination cancer therapy.

Tailoring nanoparticles based on boron dipyrromethene for cancer imaging and therapy

Boron dipyrromethene (BODIPY), as a traditional fluorescent dye, has drawn increasing attention because of its excellent photophysical properties like adjustable spectra and outstanding photostability. BODIPY dyes could be assembled into nanoparticles for cancer imaging and therapy via rational design. In this review, the bio-applications of BODIPY-containing nanoparticles are introduced in detail, such as cellular imaging, near-infrared fluorescence imaging, computed tomography imaging, photoacoustic imaging, phototherapy, and theranostics. The construction strategies of BODIPY-containing nanoparticles are emphasized so the review has three sections-self-assembly of small molecules, chemical conjugation with hydrophilic compounds, and physical encapsulation. This review not only summarizes various and colorific bio-applications of BODIPY-containing nanoparticles, but also provides reasonable design methods of BODIPY-containing nanoparticles for cancer theranostics. This article is categorized under: Diagnostic Tools > in vivo Nanodiagnostics and Imaging.

Design and Synthesis of Polymer Prodrugs for Improving Water-Solubility, Pharmacokinetic Behavior and Antitumor Efficacy of TXA9

PURPOSE

TXA9, a novel cardiac glycoside, has a potent anti-proliferative effect against A549 human lung cancer cells, however, possesses a poor water-solubility and a rapid metabolic rate in vivo which limited the further development of TXA9. To overcome the shortcomings of TXA9, four polymer prodrugs of TXA9 were designed and synthesized.

METHODS

Poly (ethylene glycol) monomethyl ether (mPEG) and α-tocopherol polyethylene glycol succinate (TPGS) were applied to modify TXA9 via carbonate ester and glycine linkers respectively to obtain four polymer prodrugs. The water-solubility and stability of prodrugs were studied in vitro while their pharmacokinetic behaviors and antitumor activity were investigated in vivo.

RESULTS

The water-solubility of TXA9 was obviously increased and prodrugs with glycine linkers showed a better stability in rat plasma. Their pharmacokinetic investigation found that the t_1/2 and AUC_0-∞ of TPGS-Gly-TXA9 was increased by 80- and 9.6-fold compared with that of TXA9, which was more superior than the other three prodrugs. More importantly, the tumor inhibition rate of TPGS-Gly-TXA9 (43.81%) on A549 xenograft nude mice was significantly increased compared with that of TXA9 (25.26%).

CONCLUSION

The above results suggested that TPGS-Gly-TXA9 possessed better antitumor efficiency than TXA9 and could be further investigated as an anti-cancer agent.

Amino acid transporters: Emerging roles in drug delivery for tumor-targeting therapy

Amino acid transporters, which play a vital role in transporting amino acids for the biosynthesis of mammalian cells, are highly expressed in types of tumors. Increasing studies have shown the feasibility of amino acid transporters as a component of tumor-targeting therapy. In this review, we focus on tumor-related amino acid transporters and their potential use in tumor-targeting therapy. Firstly, the expression characteristics of amino acid transporters in cancer and their relationship with tumor growth are reviewed. Secondly, the recognition requirements are discussed, focusing on the "acid-base" properties, conformational isomerism and structural analogues. Finally, recent developments in amino acid transporter-targeting drug delivery strategies are highlighted, including prodrugs and nanocarriers, with special attention to the latest findings of molecular mechanisms and targeting efficiency of transporter-mediated endocytosis. We aim to offer related clues that might lead to valuable tumor-targeting strategies by the utilization of amino acid transporters.

Self-Delivered and Self-Monitored Chemo-Photodynamic Nanoparticles with Light-Triggered Synergistic Antitumor Therapies by Downregulation of HIF-1α and Depletion of GSH

Photodynamic therapy (PDT), a clinically approved cancer treatment, has faced many drawbacks that restricted its applications. For example, the hypoxia-induced elevated hypoxia-inducible factor-1α (HIF-1α) may desensitize tumors to PDT, and the high concentration of glutathione (GSH) in cancer cells can also neutralize the generated reactive oxygen species (ROS) during PDT, resulting in insufficient therapy. Moreover, extra probes for imaging-guided visualization therapy are always needed to track drug release or distribution, while it may decrease the drug loading of the drug delivery system (DDS). In the present study, we have designed and prepared a novel multifunctional combined therapy nanoparticle (ZnPc@Cur-S-OA NPs), in which curcumin (Cur) was not only used as a chemotherapy drug to achieve a combination therapy with PDT via downregulating HIF-1α and depleting GSH in B16F10 cells but also designed as a small-molecule ROS-triggered release prodrug to deliver the photosensitizer (PS). The red fluorescence of PS in the nanoparticles (NPs) can be used to track the NPs distribution, while the green fluorescence of Cur showed an "OFF-ON" activation, which enables additional imaging and real-time self-monitoring capabilities. These results proved that the prepared combined therapy NPs were more effective to inhibit the growth of B16F10 mouse melanoma tumor than was monotherapy without eliciting systemic toxicity either in vitro or in vivo, which indicated the combined therapy NPs as an effective way to improve the PDT efficacy via downregulation of HIF-1α and depletion of GSH. Thus, the strategy of using a multifunctional natural product as the stimuli-responsive carrier as well as the synergist with PDT for enhancing antitumor efficacy via multiple pathways may open an alternative avenue to fabricate new self-delivery combination therapy nanodrugs. Besides, the fluorescence emitted from the drug can be used for real-time self-monitoring of drug release and distribution, which has great potential in clinic to adjust the administration dose and irradiation time for different tumor types and stages for individual therapy.

Glutathione and Reactive Oxygen Species Dual-Responsive Block Copolymer Prodrugs for Boosting Tumor Site-Specific Drug Release and Enhanced Antitumor Efficacy

A remarkable hallmark of cancer cells is the heterogeneous coexistence of overproduced intracellular glutathione (GSH) and a high level of reactive oxygen species (ROS) compared with those in normal cells, which have been frequently used as the stimuli to trigger drug release from the nanocarriers. Most of the stimuli-responsive delivery vehicles have been designed to respond to only one redox stimulus (e.g., GSH or ROS). Herein, we develop a GSH and ROS dual-responsive amphiphilic diblock copolymer prodrug (BCP) (GR-BCP) consisting of poly(ethylene glycol) (PEG)- and camptothecin (CPT)-conjugated poly(methacrylate) in the side chains via thioether bonds. In comparison, GSH or ROS single-responsive BCPs (G-BCPs or R-BCPs) were prepared, where CPT drugs were linked by disulfide or thioketal bonds, respectively. The three BCPs can form well-defined spherical micellar nanoparticles in an aqueous solution with a diameter of ∼50 nm. Compared with G-BCP and R-BCP, GR-BCP realized the highest cytotoxicity against HeLa cells with the half-inhibitory concentration (IC₅₀) of 6.3 μM, which is much lower than 17.8 μM for G-BCP and 28.9 μM for R-BCP. Moreover, for in vivo antitumor performance, G-BCP, R-BCP, and GR-BCP showed similar efficiencies in blood circulation and tumor accumulation after intravenous injection. However, GR-BCP realized the most efficient tumor suppression with few side effects. Our findings demonstrate that intracellular GSH and ROS dual-responsive BCPs show a more efficient responsive drug release inside tumor cells for boosting the antitumor efficacy as compared with GSH or ROS single-responsive BCPs, which provides novel strategies for designing redox-responsive BCPs.

Distinct Influence of Saturated Fatty Acids on Malignant and Nonmalignant Human Lung Epithelial Cells

The impact of saturated fatty acids (FA) on viability and properties of malignant and nonmalignant cells has not been studied in detail so far. The present study was aimed at evaluation of the influence of saturated FA (10:0-18:0) on malignant (A459) and nonmalignant (BEAS-2B) human lung epithelial cells. FA strongly affected A549 cells, but not BEAS-2B cells. Viability of A549 cells incubated with 14:0-18:0 was decreased by 53-91% as compared to untreated cells. Cell membrane stiffness in those cells as measured by atomic force microscopy was also reduced. Median value of apparent Young's modulus of untreated A549 cell membrane was 16.9 kPa and it decreased to 8.9 kPa for cells incubated with 14:0. Viability and mechanical properties of BEAS-2B cells were not altered by presence of FA. Those surprising discrepancies can be related to the differences in FA uptake rate. A549 cells were found to incorporate higher amount of FA and this corresponded to decrease in cell membrane stiffness and reduced cell viability. The performed studies showed that saturated FA have distinct influence on various types of cells, which may be exploited in development of the advanced lipid drug delivery systems.