Tumor redox heterogeneity-responsive prodrug nanocapsules for cancer chemotherapy

Polymer Prodrug-Based Nanoreactors Activated by Tumor Acidity for Orchestrated Oxidation/Chemotherapy

Therapeutic nanoreactors have been proposed to treat cancers through in situ transformation of low-toxicity prodrugs into toxic therapeutics in the body. However, the in vivo applications are limited by low tissue-specificity and different tissue distributions between sequentially injected nanoreactors and prodrugs. Herein, we construct a block copolymer prodrug-based polymersome nanoreactor that can achieve novel orchestrated oxidation/chemotherapy of cancer via specific activation at tumor sites. The block copolymers composed of poly(ethylene glycol) (PEG) and copolymerized monomers of camptothecin (CPT) and piperidine-modified methacrylate [P(CPTMA-co-PEMA)] were optimized to self-assemble into polymersomes in aqueous solution for encapsulation of glucose oxidase (GOD) to obtain GOD-loaded polymersome nanoreactors (GOD@PCPT-NR). GOD@PCPT-NR maintained inactive in normal tissues upon systemic administration. After deposition in tumor tissues, tumor acidity-triggered protonation of PPEMA segments resulted in high permeability of the polymersome membranes and oxidation reaction of diffused glucose and O₂ under the catalysis of GOD. The activation of the reaction generated H₂O₂, improving the oxidative stress in tumors. Simultaneously, a high level of H₂O₂ further activated PCPTMA prodrugs, releasing active CPT drugs. High tumor oxidative stress and released CPT drugs synergistically killed cancer cells and suppressed tumor growth via oxidation/chemotherapy. Our study provides a new strategy for engineering therapeutic nanoreactors in an orchestrated fashion for cancer therapy.

Dual stimuli-responsive Fe3O4 graft poly(acrylic acid)-block-poly(2-methacryloyloxyethyl ferrocenecarboxylate) copolymer micromicelles: surface RAFT synthesis, self-assembly and drug release applications

BACKGROUND

Stimuli-responsive polymer materials are a new kind of intelligent materials based on the concept of bionics, which exhibits more significant changes in physicochemical properties upon triggered by tiny environment stimuli, hence providing a good carrier platform for antitumor drug delivery.

RESULTS

Dual stimuli-responsive Fe3O4 graft poly(acrylic acid)-block-poly(2-methacryloyloxyethyl ferrocenecarboxylate) block copolymers (Fe3O4-g-PAA-b-PMAEFC) were engineered and synthesized through a two-step sequential reversible addition-fragmentation chain transfer polymerization route. The characterization was performed by FTIR, 1H NMR, SEC, XRD and TGA techniques. The self-assembly behavior in aqueous solution upon triggered by pH, magnetic and redox stimuli was investigated via zeta potentials, vibration sample magnetometer, cyclic voltammetry, fluorescent spectrometry, dynamic light scattering, XPS, TEM and SEM measurements. The experimental results indicated that the Fe3O4-g-PAA-b-PMAEFC copolymer materials could spontaneously assemble into hybrid magnetic copolymer micromicelles with core-shell structure, and exhibited superparamagnetism, redox and pH stimuli-responsive features. The hybrid copolymer micromicelles were stable and nontoxic, and could entrap hydrophobic anticancer drug, which was in turn swiftly and effectively delivered from the drug-loaded micromicelles at special microenvironments such as acidic pH and high reactive oxygen species.

CONCLUSION

This class of stimuli-responsive copolymer materials is expected to find wide applications in medical science and biology, etc., especially in drug delivery system.

New Generation Nanomedicines Constructed from Self-Assembling Small-Molecule Prodrugs Alleviate Cancer Drug Toxicity

The therapeutic index for chemotherapeutic drugs is determined in part by systemic toxicity, so strategies for dose intensification to improve efficacy must also address tolerability. In addressing this issue, we have investigated a novel combinatorial strategy of reconstructing a drug molecule and using sequential drug-induced nanoassembly to fabricate supramolecular nanomedicines (SNM). Using cabazitaxel as a target agent, we established that individual synthetic prodrugs tethered with polyunsaturated fatty acids were capable of recapitulating self-assembly behavior independent of exogenous excipients. The resulting SNM could be further refined by PEGylation with amphiphilic copolymers suitable for preclinical studies. Among these cabazitaxel derivatives, docosahexaenoic acid-derived compound 1 retained high antiproliferative activity. SNM assembled with compound 1 displayed an unexpected enhancement of tolerability in animals along with effective therapeutic efficacy in a mouse xenograft model of human cancer, compared with free drug administered in its clinical formulation. Overall, our studies showed how attaching flexible lipid chains to a hydrophobic and highly toxic anticancer drug can convert it to a systemic self-deliverable nanotherapy, preserving its pharmacologic efficacy while improving its safety profile. Cancer Res; 77(24); 6963-74. ©2017 AACR.

CO2-based amphiphilic polycarbonate micelles enable a reliable and efficient platform for tumor imaging

Biodegradable polymeric nanomaterials can be directly broken down by intracellular processes, offering a desirable way to solve toxicity issues for cancer diagnosis and treatment. Among them, aliphatic polycarbonates are approved for application in biological fields by the United States Food and Drug Administration (FDA), however, high hydrophobicity, deficient functionality and improper degradation offer significant room for improvement in these materials.

METHODS

To achieve progress in this direction, herein, we demonstrate that CO2-based amphiphilic polycarbonates (APC) with improved hydrophilicity and processability can be used as a reliable and efficient platform for tumor imaging. To better investigate their potential, we devised a convenient strategy through conjugation of APC with gadolinium (Gd).

RESULTS

The resulting polymeric micelles (APC-DTPA/Gd) exhibit excellent magnetic resonance imaging performance, simultaneously enabling real-time visualization of bioaccumulation and decomposition of polymeric micelles in vivo. Importantly, these micelles can be degraded to renally cleared products within a reasonable timescale without evidence of toxicity.

CONCLUSION

Our findings may help the development of CO2-based amphiphilic polycarbonate for cancer diagnosis and treatment, accompanied by their low-toxicity degradation pathway.

Free-Blockage Mesoporous Anticancer Nanoparticles Based on ROS-Responsive Wetting Behavior of Nanopores

To achieve an excellent delivery effect of drug, stimuli-responsive nano "gate" with physical blockage units is usually constructed on the surface of the mesoporous silica nanocarriers (MSNs). In nature, the aquaporins in cell membrane can control the transport of water molecules by regulating the channel wettability, which is resulted from the conformational change of amino acids in the channel. Inspired by this phonomenon, herein a new concept of free-blockage controlled release system is proposed, which is achieved by controlling the wettability of the internal surface of nanopores on MSNs. Such a new system is different from the physical-blockage controlled release system, which bypasses the use of nano "gate" and overcomes the limitations of traditional physical blockage system. Moreover, further studies have shown that the system can selectively release the entrapped doxorubicin in human breast adenocarcinoma (MCF-7) cells triggered by intracellular reactive oxygen species (ROS) but not in normalhuman umbilical vein endothelial cells (HUVECs) containing ROS with low levels. The wettability-determined free-blockage controlled release system is simple and effective, and it can also be triggered by intracellular biological stimuli, which provides a new approach for the future practical application of drug delivery and cancer therapy.

Biopolymer-Drug Conjugate Nanotheranostics for Multimodal Imaging-Guided Synergistic Cancer Photothermal-Chemotherapy

Some of the biomedical polymer-drug conjugates are being translated into clinical trials; however, they intrinsically lack photothermal and multi-imaging capabilities, hindering them from imaging-guided precision cancer therapy and complete tumor regression. We introduce a new concept of all-in-one biopolymer-drug conjugate nanotheranostics and prepare a kind of intracellular pH-sensitive polydopamine-doxorubicin (DOX) conjugate nanoparticles (PDCNs) under mild conditions. Significantly, this strategy integrates polymeric prodrug-induced chemotherapy (CT), near-infrared (NIR) light-mediated photothermal therapy (PT), and triple modalities including DOX self-fluorescence, photothermal, and photoacoustic (PA) imaging into one conjugate nanoparticle. The PDCNs present excellent photothermal property, dual stimuli-triggered drug release behavior, and about 12.4-fold blood circulation time compared to free DOX. Small animal fluorescent imaging technique confirms that PDCNs have preferential tumor accumulation effect in vivo, giving a 12.8-fold DOX higher than the control at 12 h postinjection. Upon NIR laser irradiation (5 min, 808 nm, and 2 W·cm^-2), the PDCN-mediated photothermal effect can quickly elevate the tumor over 50 °C, exhibiting good photothermal and PA imaging functions, of which the PA amplitude is 3.6-fold greater than the control. In vitro and in vivo assays persuasively verify that intravenous photothermal-CT of PDCNs produces synergistic antitumor activity compared to single PT or CT, achieving complete tumor ablation during the evaluation period.

Construction of a Supramolecular Drug-Drug Delivery System for Non-Small-Cell Lung Cancer Therapy

Nanoscale drug delivery systems (DDSs) are generally considered to be an effective alternative to small molecular chemotherapeutics due to improved accumulation in the tumor site and enhanced retention in blood. Nevertheless, most DDSs have low loading efficiency or even pose a high threat to normal organs from severe side effects. Ideally, a supramolecular drug-drug delivery system (SDDDS) composed of pure drugs via supramolecular interaction provides a hopeful approach for cancer treatment. Herein we propose a facile method to construct SDDDS via coassembly of gefitinib (GEF) and tripeptide tyroservatide (YSV), two kinds of chemotherapeutic pharmaceuticals for non-small-cell lung cancer (NSCLC) via multiple intermolecular interactions, including hydrogen bonding and π-π stacking. As shown through transmission electron microscopy (TEM) and dynamic light scattering (DLS), GEF and YSV self-assemble into nanoparticles with regular morphology and uniform size, which facilitates the delivery of both drugs. In vitro studies demonstrate that the SDDDS is much more efficient in entering cancer cells and inhibiting the proliferation of cancer cells compared with single GEF, YSV, or GEF/YSV drug mixture. In vivo experiments show that the SDDDS can selectively accumulate in tumor tissue, resulting in much better drug efficacy without evident side effects. Considering the advantages of the SDDDS, we believe this strategy provides a promising route for enhanced anticancer therapy in nanomedicine.

Extended release delivery of erlotinib glutathione nanosponge for targeting lung cancer

Systemic and uncontrolled administration of erlotinib hydrochloride (ETB) is associated with severe toxicity. A novel targeted and extended release nanosponge (NS) was synthesized from glutathione (GHS) by a one-step reaction between β-cyclodextrin and pyromellitic dianhydride at room temperature for delivery of ETB in lung cancer. Characterization studies were performed using sophisticated instruments. In-vitro release study was performed in the presence of incremental concentrations of GHS which was analyzed using HPLC. Cell cytotoxicity study was evaluated on human lung cancer (A549) cell lines. In-vivo tumour inhibition and biodistribution of ETB-loaded GHS-NS (ETB-NS) were performed on BALB/c mice. NS obtained was spherical, size 212 ± 2.45 nm and high drug entrapment (92.34 ± 5.31%) (p < .001). In-vitro extended drug release (76.89 ± 0.1% release at 168 h), which was directly proportional to the concentration of GHS, demonstrated tumour targeting. There was enhanced in-vitro cytotoxicity and 97.5% inhibition in tumour growth on administering NS when compared to plain ETB (48% inhibition) indicating targeting of NS to the tumour site. Biodistribution study and in-vivo tumour growth inhibition study revealed drug release to the cancerous cell, thus preventing unnecessary drug exposure. ETB-NS exhibits extended drug release proportional to the external GSH concentration.

Self-Assembled Polyprodrug Amphiphile for Subcutaneous Xenograft Tumor Inhibition with Prolonged Acting Time In Vivo

Polymeric drug delivery system termed as "polyprodrug amphiphile" poly(2-methylacryloyloxyethyl phosphorylcholine)-b-poly(10-hydroxy-camptothecin methacrylate (pMPC-b-pHCPT) is developed for the prolonged-acting cancer therapy. It is obtained by two-step reversible addition-fragmentation chain transfer polymerization of zwitterionic monomer MPC and an esterase-responsive polymerizable prodrug methacrylic anhydride-CPT, respectively. This diblock polymer is composed of both antifouling (pMPC) and bioactive (pHCPT) segments and the drug is designed as a building block to construct the polymer skeleton directly. Due to its distinct amphiphilicity, the polymer can self-assemble into micelles with different dynamic sizes by facilely tuning the ratio of MPC/HCPT under physiological conditions. The outer pMPC shell is superhydrophilic to form dense hydrate layer preventing the nanosystem from unwanted nonspecific protein adsorption, which is the main lead cause of the rapid clearance of nanoparticles in vivo, thus facilitating the accumulation of drugs in tumor sites via enhanced permeability and retention effect. The configuration of the polyprodrug amphiphile is confirmed by several measurements. The resistance to albumin adsorption, prolonged plasma retention time, accumulation in tumor sites, and anticancer activity of the micelles is also investigated in vitro and in vivo. This novel amphiphile can be expected as a promising agent for the passive targeted prolonged-acting cancer therapy.

Leveraging H2 O2 Levels for Biomedical Applications

Hydrogen peroxide (H₂ O₂ )-responsive materials have been employed as drug delivery or diagnostic systems to treat or detect diseases with abnormal oxidative stress. A number of H₂ O₂ -responsive systems have been developed, and they have achieved great progress in controlled drug delivery for disease treatment. However, pathological sites with elevated H₂ O₂ level, such as cancer and inflammation, have their own characteristics; therefore the material structures and the subsequent formulations should be reasonably designed to acquire maximized therapeutic effects. In this progress report, we overview the development of H₂ O₂ -responsive functional groups for constructing H₂ O₂ -responsive formulations, as well as the guidance for designing suitable formulations to treat each specific pathological condition. The challenges and perspectives in this field are also discussed.

A self-immolative prodrug nanosystem capable of releasing a drug and a NIR reporter for in vivo imaging and therapy

In vivo monitoring of the biodistribution and activation of prodrugs is highly attractive, and the self-immolative dendritic architecture is deemed as a promising approach for constructing theranostic prodrug in which the release/activation of different payloads is needed. Herein, A GSH-triggered and self-immolative dendritic platform comprising an anticancer drug camptothecin (CPT), a cleavable linker and a two-photon NIR fluorophore (dicyanomethylene-4H-pyran, DCM) has been developed for in situ tracking of drug release and antitumour therapy. In vitro experiments demonstrate that, the presence of glutathione (GSH) induces the cleavage of the self-immolative linker, resulting in comitant release of the drug and the dye. Upon cell internalization and under one- or two-photon excitation, prominent intracellular fluorescence can be observed, indicating the release of the payloads in live cells. Upon loaded in phospholipid vesicles, the prodrug has also been successfully utilized for in vivo and in situ tracking of drug release and cancer therapy in a mouse model. Several hours post injection, the prodrug generates strong fluorescence on tumour sites, demonstrating the prodrug's capability of monitoring the on-site drug release. Moreover, the prodrug shows considerable high activity and exerts obvious inhibition towards tumour growth. This work suggests that the prodrug with self-immolative dendritic structure can work well in vivo and this strategy may provide an alternative approach for designing theranostic drug delivery systems.

pH/redox dual-sensitive dextran nanogels for enhanced intracellular drug delivery

pH/redox dual-responsive nanogels (DEX-SS) were prepared by precipitation polymerization of methacrylated dextran (DEXMA), 2-aminoethylmethacrylate (AEMA) and N,N'-bis(acryloyl)cystamine (BAC), and then loaded with methotrexate (MTX). Nanogels were spherical and exhibited homogeneous size distribution (460nm, PDI<0.30) as observed using dynamic light scattering (DLS) and scanning electron microscopy (SEM). DEX-SS were sensitive to the variations of pH and redox environment. Nanogels incubated in buffer pH 5.0 containing 10mM glutathione (GSH) synergistically increased the mean diameter and the PDI to 750nm and 0.42, respectively. In vitro release experiments were performed at pH 7.4 and 5.0 with and without GSH. The cumulative release of MTX in pH 5.0 medium with 10mMGSH was 5-fold higher than that recorded at pH 7.4 without GSH. Fibroblasts and tumor cells were used to tests the effects of blank DEX-SS and MTX@DEX-SS nanogels on cell viability. Remarkable influence of pH on nanogels internalization into HeLa cells was evidenced by means of confocal microscopy and flow cytometry.

Dual 7-ethyl-10-hydroxycamptothecin conjugated phospholipid prodrug assembled liposomes with in vitro anticancer effects

7-Ethyl-10-hydroxycamptothecin (SN38), as a highly active topoisomerase I inhibitor, is 200-2000-fold more cytotoxic than irinotecan (CPT-11) commercially available as Camptosar®. However, poor solubility and low stability extensively restricted its clinical utility. In this report, dual SN38 phospholipid conjugate (Di-SN38-PC) prodrug based liposomes were developed in order to compact these drawbacks. Di-SN38-PC prodrug was first synthesized by inhomogeneous conjugation of two SN38-20-O-succinic acid molecules with L-α-glycerophosphorylcholine (GPC). The assembly of the prodrug was carried out without any excipient by using thin film method. Dynamic light scattering (DLS), transmission electron microscope (TEM) and cryogenic transmission electron microscopy (cyro-TEM) characterization indicated that Di-SN38-PC can form spherical liposomes with narrow particle size (<200nm) and negatively charged surface (-21.6±3.5mV). The loading efficiency of SN38 is 65.2 wt.% after a simple calculation. In vitro release test was further performed in detail. The results demonstrated that Di-SN38-PC liposomes were stable in neutral environment but degraded in a weakly acidic condition thereby released parent drug SN38 effectively. Cellular uptake studies reflected that the liposomes could be internalized into cells more significantly than SN38. In vitro antitumor activities were finally evaluated by MTT assay, colony formation assay, flow cytometry, RT-PCR analysis and Western Blot. The results showed that Di-SN38-PC liposomes had a comparable cytotoxicity with SN38 against MCF-7 and HBL-100, and a selective promotion of apoptosis of tumor cells. Furthermore, a pharmacokinetics test showed that Di-SN38-PC liposomes had a longer circulating time in blood compared with the parent drug. All the results indicate that Di-SN38-PC liposomes are an effective delivery system of SN38.

Self-Assembly of Gold Nanoparticles Shows Microenvironment-Mediated Dynamic Switching and Enhanced Brain Tumor Targeting

Inorganic nanoparticles with unique physical properties have been explored as nanomedicines for brain tumor treatment. However, the clinical applications of the inorganic formulations are often hindered by the biological barriers and failure to be bioeliminated. The size of the nanoparticle is an essential design parameter which plays a significant role to affect the tumor targeting and biodistribution. Here, we report a feasible approach for the assembly of gold nanoparticles into ~80 nm nanospheres as a drug delivery platform for enhanced retention in brain tumors with the ability to be dynamically switched into the single formulation for excretion. These nanoassemblies can target epidermal growth factor receptors on cancer cells and are responsive to tumor microenvironmental characteristics, including high vascular permeability and acidic and redox conditions. Anticancer drug release was controlled by a pH-responsive mechanism. Intracellular L-glutathione (GSH) triggered the complete breakdown of nanoassemblies to single gold nanoparticles. Furthermore, in vivo studies have shown that nanospheres display enhanced tumor-targeting efficiency and therapeutic effects relative to single-nanoparticle formulations. Hence, gold nanoassemblies present an effective targeting strategy for brain tumor treatment.

Diverse Applications of Nanomedicine

The design and use of materials in the nanoscale size range for addressing medical and health-related issues continues to receive increasing interest. Research in nanomedicine spans a multitude of areas, including drug delivery, vaccine development, antibacterial, diagnosis and imaging tools, wearable devices, implants, high-throughput screening platforms, etc. using biological, nonbiological, biomimetic, or hybrid materials. Many of these developments are starting to be translated into viable clinical products. Here, we provide an overview of recent developments in nanomedicine and highlight the current challenges and upcoming opportunities for the field and translation to the clinic.

Stimuli-responsive dendrimers in drug delivery

Dendrimers have shown great promise as carriers in drug delivery due to their unique structures and superior properties. However, the precise control of payload release from a dendrimer matrix still presents a great challenge. Stimuli-responsive dendrimers that release payloads in response to a specific trigger could offer distinct clinical advantages over those dendrimers that release payloads passively. These smart polymers are designed to specifically release their payloads at targeted regions or at constant release profiles for specific therapies. They represent an attractive alternative to targeted dendrimers and enable dendrimer-based therapeutics to be more effective, more convenient, and much safer. The wide range of stimuli, either endogenous (acid, enzyme, and redox potentials) or exogenous (light, ultrasound, and temperature change), allows great flexibility in the design of stimuli-responsive dendrimers. In this review article, we will highlight recent advances and opportunities in the development of stimuli-responsive dendrimers for the treatment of various diseases, with emphasis on cancer. Specifically, the applications of stimuli-responsive dendrimers in drug delivery as well as their mechanisms are intensively reviewed.

Branched-chain and dendritic lipids for nanoparticles

Lipid nanoparticles (LNPs) for drug-delivery applications are largely derived from natural lipids. Synthetic lipids, particularly those incorporating branched hydrocarbons and hyper-branched hydrocarbon architectures, may afford enhanced lipophilicity with enhanced fluidity and thereby lead to LNP stabilization. Hydrocarbon anchors based on serinol diesters were prepared from linear Cn (n = 14, 16, 18) and branched (n = 16) acids with Boc-protected serinol. These diesters were further dimerized on an iminodiacetamide backbone to provide eight branched-chain and dendritic lipid anchors. Derivatization of these core structures provided eight PEG-lipids and seven thiopurine linked lipid–drug conjugates. LNPs were prepared by microfluidic mixing from mixed lipids in ethanol diluted into aqueous media. The lipid–drug conjugates incorporated 5 mol% of a phosphocholine and 5 mol% of a commercial PEG-lipid to form LNPs with a thiopurine drug loading of 15 wt%. The PEG–lipids prepared were formulated at 1.5 mol% as a surface stabilizer to LNPs containing dsDNA lipoplexes. The stability of the LNPs was assessed under different storage conditions through monitoring of particle size. For both LNPs from lipid–thiopurine conjugates and the PEG-lipid systems, there is strong preliminary evidence that hydrocarbon branching results in LNP stabilization. Four of the lipid–drug conjugate formulations were stable to cell culture conditions (10% serum, 37 °C) and the toxicity of these LNPs was assessed in two cell lines relative to the free thiopurines in the medium. The observed toxicity is consistent with cellular uptake of the LNPs and reductive release of the cargo thiopurine within the cell.

Anaerobe-Inspired Anticancer Nanovesicles

Anaerobic bacteria, such as Clostridium and Salmonella, can selectively invade and colonize in tumor hypoxic regions (THRs) and deliver therapeutic products to destroy cancer cells. Herein, we present an anaerobe nanovesicle mimic that can not only be activated in THRs but also induce hypoxia in tumors by themselves. Moreover, inspired by the oxygen metabolism of anaerobes, we construct a light-induced hypoxia-responsive modality to promote dissociation of vehicles and activation of bioreductive prodrugs simultaneously. In vitro and in vivo experiments indicate that this anaerobe-inspired nanovesicle can efficiently induce apoptotic cell death and significantly inhibit tumor growth. Our work provides a new strategy for engineering stimuli-responsive drug delivery systems in a bioinspired and synergistic fashion.

A reactive oxygen species (ROS)-responsive low molecular weight gel co-loaded with doxorubicin and Zn(ii) phthalocyanine tetrasulfonic acid for combined chemo-photodynamic therapy

A ROS-responsive low molecular weight hydrogel was fabricated and loaded with an anticancer drug and a photosensitizer for efficient chemo-photodynamic therapy.

Coumarin polycaprolactone polymeric nanoparticles: light and tumor microenvironment activated cocktail drug delivery

Highly sensitive hypoxia (H₂O₂)-activated photoresponsive polymeric nanoparticles for cocktail delivery of anticancer drugs doxorubicin (Dox) and chlorambucil (Cbl) were developed.

A self-immolative and DT-diaphorase-activatable prodrug for drug-release tracking and therapy

A DT-diaphorase-activatable theranostic prodrug has been developed for visualizing the release of active drug and enhancing the therapeutic effect.

A two-photon-activated prodrug for therapy and drug release monitoring

A two-photon-activated prodrug has been developed for drug release monitoring and photo-controllable therapy.

A multi-stimuli responsive nanoparticulate SN38 prodrug for cancer chemotherapy

Modification of drug delivery systems (DDSs) with stimuli-responsive elements could significantly increase the tumor-specific delivery of anticancer drugs.

A ROS-responsive polymeric micelle with a π-conjugated thioketal moiety for enhanced drug loading and efficient drug delivery

As the implications of reactive oxygen species (ROS) are elucidated in many diseases, ROS-responsive nanoparticles are attracting great interest from researchers.

Glutathione-responsive paclitaxel dimer nanovesicles with high drug content

Paclitaxel dimers containing mono thioether linkers can self-assemble into hollow nanovesicles that exhibit comparable cytotoxicity to Taxol.

Leveraging Physiology for Precision Drug Delivery

Physiological characteristics of diseases bring about both challenges and opportunities for targeted drug delivery. Various drug delivery platforms have been devised ranging from macro- to micro- and further into the nanoscopic scale in the past decades. Recently, the favorable physicochemical properties of nanomaterials, including long circulation, robust tissue and cell penetration attract broad interest, leading to extensive studies for therapeutic benefits. Accumulated knowledge about the physiological barriers that affect the in vivo fate of nanomedicine has led to more rational guidelines for tailoring the nanocarriers, such as size, shape, charge, and surface ligands. Meanwhile, progresses in material chemistry and molecular pharmaceutics generate a panel of physiological stimuli-responsive modules that are equipped into the formulations to prepare “smart” drug delivery systems. The capability of harnessing physiological traits of diseased tissues to control the accumulation of or drug release from nanomedicine has further improved the controlled drug release profiles with a precise manner. Successful clinical translation of a few nano-formulations has excited the collaborative efforts from the research community, pharmaceutical industry, and the public towards a promising future of smart drug delivery.

Increased Gold Nanoparticle Retention in Brain Tumors by in Situ Enzyme-Induced Aggregation

The treatment of brain tumors remains a challenge due to the limited accumulation of drugs and nanoparticles. Here, we triggered the aggregation of gold nanoparticles (AuNPs) using legumain to enhance the retention of chemotherapeutics in brain tumors. This nanoplatform, AuNPs-A&C, is comprised of Ala-Ala-Asn-Cys-Lys modified AuNPs (AuNPs-AK) and 2-cyano-6-aminobenzothiazole modified AuNPs (AuNPs-CABT). AuNPs-AK could be hydrolyzed to expose the 1,2-thiolamino groups on AuNPs-AK in the presence of legumain, which occurs by a click cycloaddition with the contiguous cyano group on AuNPs-CABT, resulting in formation of AuNPs aggregates. This strategy led to an enhanced retention of the AuNPs in glioma cells both in vitro and in vivo due to the blocking of nanoparticle exocytosis and minimizing nanoparticle backflow to the bloodstream. After conjugation of doxorubicin (DOX) via a pH-sensitive linker to AuNPs-A&C, the efficiency for treating glioma was improved. The median survival time for the DOX-linked AuNPs-A&C increased to 288% in comparison to the saline group. We further show the use of the AuNPs-A&C for optical imaging applications. In conclusion, we provide a strategy to increase nanoparticle tumor accumulation with the potential to improve therapeutic outcome.

Macrophages as Active Nanocarriers for Targeted Early and Adjuvant Cancer Chemotherapy

Taking advantage of the highly permeable vasculature and lack of lymphatic drainage in solid tumors (EPR effect), nanosized drug delivery systems or nanomedicines have been extensively explored for tumor-targeted drug delivery. However, in most clinical cases tumors such as the early stage tumors and post-surgery microscopic residual tumors have not yet developed such pathological EPR features, i.e., EPR-deficient. Therefore, nanomedicines may not be applicable for such these tumors. Macrophages by nature can actively home and extravasate through the tight vascular wall into tumors and migrate to their hypoxic regions, and possess perfect stealth ability for long blood circulation and impressive phagocytosis for drug loadings. Thus, nanomedicines loaded in macrophages would harness both merits and gain the active tumor homing capability independent of the EPR effect for treatments of the EPR-deficient tumors. Herein, the critical considerations, current progress, challenges and future prospects of macrophages as carriers for nanomedicines are summarized, aiming at rational design of EPR-independent tumor-targeting active nanomedicines for targeted early and adjuvant cancer chemotherapy.

Redox-responsive star-shaped magnetic micelles with active-targeted and magnetic-guided functions for cancer therapy

Highly efficient delivery of therapeutic agents to target sites is of great importance for achieving excellent therapeutic efficacy in cancer treatment. Here, we report a redox-responsive star-shaped magnetic micelle with both active-targeted and magnetic-guided functions. The magnetic star-shaped micelles are formed by self-assembly of four-arm poly(ethylene glycol) (PEG)-poly(ε-caprolactone) (PCL) copolymers with disulfide bonds as intermediate linkers. Anticancer drug doxorubicin (DOX) and magnetic iron oxide nanoparticles (Fe3O4) are simultaneously encapsulated into the hydrophobic cores. PBA ligands are chemically conjugated to the end of the hydrophilic PEG segments, endowing the active targeting of nanocarriers. Both qualitative and quantitative analyses of the intracellular uptake of these micelles with active-targeting and dual-targeting are performed in vitro by cultured with salic acid (SA)-positive tumor cells (human liver carcinoma cell line HepG2, human cervical cancer cell line HeLa) and SA-negative tumor cells (human breast adenocarcinoma cell line MCF-7, human non-small cell lung cancer cell line A549) in the presence or absence of a permanent magnetic field. In vivo biodistribution studies with active-targeting and dual-targeting and in vivo anti-tumor effect are carried out in detail after being applied to the BALB/c mice bearing mouse H22 hepatocarcinoma cells tumor model. These in vivo results demonstrate that a great amount of dual-targeted magnetic micelles accumulate around the tumor tissues by the magnetic-guiding and in turn are taken up by the tumor cells through SA-mediated endocytosis, leading to a high therapeutic efficacy to the artificial solid tumor.

STATEMENT OF SIGNIFICANCE

A redox-responsive star-shaped magnetic micelle with both active-targeted and magnetic-guided functions was developed. Both qualitative and quantitative analysis of the intracellular uptake with dual-targeting of these micelles were performed in vitro by salic acid (SA)-positive tumor cells. The in vivo results demonstrate that a great amount of dual-targeted magnetic micelles accumulated around the tumor tissues, leading to a high therapeutic efficacy to artificial solid tumor.

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

Chemotherapeutic efficacy can be greatly improved by developing nanoparticulate drug delivery systems (nano-DDS) with high drug loading capacity and smart stimulus-triggered drug release in tumor cells. Herein, we report a novel redox dual-responsive prodrug-nanosystem self-assembled by hydrophobic small-molecule conjugates of paclitaxel (PTX) and oleic acid (OA). Thioether linked conjugates (PTX-S-OA) and dithioether inserted conjugates (PTX-2S-OA) are designed to respond to the redox-heterogeneity in tumor. Dithioether has been reported to show redox dual-responsiveness, but we find that PTX-S-OA exhibits superior redox sensitivity over PTX-2S-OA, achieving more rapid and selective release of free PTX from the prodrug nanoassemblies triggered by redox stimuli. PEGylated PTX-S-OA nanoassemblies, with impressively high drug loading (57.4%), exhibit potent antitumor activity in a human epidermoid carcinoma xenograft. This novel prodrug-nanosystem addresses concerns related to the low drug loading and inefficient drug release from hydrophobic prodrugs of PTX, and provides possibilities for the development of redox dual-sensitive conjugates or polymers for efficient anticancer drug delivery.

ROS-responsive drug delivery systems

Reactive oxygen species (ROS) play an important role in signal transduction and metabolism. Over-produced ROS in cells or tissues, however, often leads to oxidation stress that has implications in a series of diseases including cancer, aging, atherosclerosis and inflammation. Driven by the need for on-demand drug delivery and fuelled by recent development of ROS-responsive materials and nanomedicine, responsive drug delivery systems (DDSs) have gained increasing research interest. ROS-responsive DDS is designed to release therapeutic agents only in targets of interest that produce excessive ROS, which may lead to both enhanced therapeutic efficiency and reduced side effects. Multiple-stimuli responsive DDSs that are also sensitive to other stimuli can further enhance controlled drug release in sites where multiple stimuli coexist. Beyond drug delivery, multifunctional DDSs have great potential in achieving simultaneous imaging, combinatorial therapy and targeting ability by introducing multifunctional elements such as signal reporter, targeting elements and photosensitizer. This review will summarize the latest development of ROS-responsive DDSs and discuss their design principle and biomedical applications.

GSH Induced Controlled Release of Levofloxacin from a Purpose-Built Prodrug: Luminescence Response for Probing the Drug Release in Escherichia coli and Staphylococcus aureus

Fluoroquinolones are third-generation broad spectrum bactericidal antibiotics and work against both Gram-positive and Gram-negative bacteria. Levofloxacin (L), a fluoroquinolone, is widely used in anti-infective chemotherapy and treatment of urinary tract infection and pneumonia. The main pathogen for urinary tract infections is Escherichia coli, and Streptococcus pneumoniae is responsible for pneumonia, predominantly a lower respiratory tract infection. Poor permeability of L leads to the use of higher dose of this drug and excess drug in the outer cellular fluid leads to central nervous system (CNS) abnormality. One way to counter this is to improve the lipophilicity of the drug molecule, and accordingly, we have synthesized two new Levofloxacin derivatives, which participated in the spatiotemporal release of drug via disulfide bond cleavage induced by glutathione (GSH). Recent studies with Streptococcus mutants suggest that it is localized in epithelial lining fluid (ELF) of the normal lower respiratory tract and the effective [GSH] in ELF is ∼430 μM. E. coli typically cause urinary tract infections and the concentration of GSH in porcine bladder epithelium is reported as 0.6 mM for a healthy human. Thus, for the present study we have chosen two important bacteria (Gram + ve and Gram - ve), which are operational in regions having high extracellular GSH concentration. Interestingly, this supports our design of new lipophilic Levofloxacin based prodrugs, which released effective drug on reaction with GSH. Higher lipophilicity favored improved uptake of the prodrugs. Site specific release of the drug (L) could be achieved following a glutathione mediated biochemical transformation process through cleavage of a disulfide bond of these purpose-built prodrugs. Further, appropriate design helped us to demonstrate that it is possible also to control the kinetics of the drug release from respective prodrugs. Associated luminescence enhancement helps in probing the release of the drug from the prodrug in bacteria and helps in elucidating the mechanistic pathway of the transformation. Such an example is scarce in the contemporary literature.

Biodegradable brush-type copolymer modified with targeting peptide as a nanoscopic platform for targeting drug delivery to treat castration-resistant prostate cancer

Well-defined amphiphilic tumor-targeting brush-type copolymers, poly(oligo(ethylene glycol) monomethyl ether methacrylate-co-G3-C12)-g-poly(ε-caprolactone) (P(OEGMA-co-G3-C12)-g- PCL), were synthesized by the combination of ring-opening polymerization (ROP), reversible addition-fragmentation transfer (RAFT) polymerization and polymer post-functionalization, in which G3-C12 was castration-resistant prostate cancer (CRPC) targeting peptide. The obtained polymers were then employed for the targeted treatment of CRPC by delivering a hydrophobic anticancer drug (bufalin, BUF). Polymerizable monomer, 3-((2-(methacryloyloxy)ethyl)thio)propanoic acid (BSMA) and PCL-based macromolecular monomer (PCLMA) were synthesized at first. RAFT polymerization of OEGMA, BSMA, and PCLMA afforded amphiphilic brush-type copolymers, P(OEGMA-co-BSMA)-g-PCL. Post-functionalization of the obtained polymers with G3-C12 led to the formation of the final amphiphilic targeting brush-type copolymers, P(OEGMA-co-G3-C12)-g- PCL. In aqueous media, P(OEGMA-co-G3-C12)-g-PCL self-assembles into micelles with a hydrodynamic diameter (Dh) of ∼66.1±0.44nm. It was demonstrated that the obtained micellar nanoparticles exhibited good biocompatibility and biodegradability. Besides, BUF-loaded micellar nanoparticles assembled from P(OEGMA-co-G3-C12)-g-PCL, BUF-NP-(G3-C12), showed a controlled drug release in vitro and improved anticancer efficacy both in vitro and in vivo.

Dual-channel NIR activatable theranostic prodrug for in vivo spatiotemporal tracking thiol-triggered chemotherapy

Real-time tracking for where (W), when (W), and how (H) prodrugs are delivered and activated in vivo is a great challenge for prodrug development. Disulfide linkage-based prodrugs as well as their delivery systems have been studied extensively, but the WWH question in spatial and temporal (spatiotemporal) precision remains unanswered. Herein, we present a novel prodrug of camptothecin (CPT) linked to a near-infrared (NIR) cyanine dye via a disulfide linkage (Cy-S-CPT). The cleavage of the disulfide bond in Cy-S-CPT by endogenous glutathione (GSH) can activate the anti-cancer drug CPT and induce a remarkable fluorescence shift from 825 to 650 nm, thereby providing dual fluorescent channels to real-time track the prodrug biodistribution and activation in vivo. Impressively, the dual-channel NIR fluorescence bioimaging exhibits the pervasive drug distribution, i.e., the biodistribution of the intact prodrug was traced at the 825 nm-NIR fluorescence channel, whereas the activated drug was tracked at the 650 nm red fluorescence channel. In this way, we can overcome the blind spot in the metabolism kinetics of prodrugs in a certain organ or tissue. As demonstrated, the prodrug prompts activation in all the organs, particularly in the liver after an intravenous injection, and achieves predominant accumulation and activation in tumors at 24 h post injection. Cy-S-CPT loaded in PEG-PLA nanoparticles display significantly improved therapeutic efficacy and low side effects with respect to the clinical used drug CPT-11. As a consequence, the NIR spatiotemporal bioimaging in vivo with dual fluorescence channels allows the prodrug release profile to be extracted precisely, particularly in visualizing drug-released information from complex biological systems such as mice, thereby providing a unique opportunity to take insight into the relationship between theranosis and pharmacokinetics.