Wen-Hsuan Chiang

Functionalized polymersomes with outlayered polyelectrolyte gels for potential tumor-targeted delivery of multimodal therapies and MR imaging

A novel tumor-targeting polymersome carrier system capable of delivering magnetic resonance imaging (MRI) and chemotherapy is presented in this study. The doxorubicin (DOX)-loaded magnetic polymersomes were first attained by the self-assembly of lipid-containing copolymer, poly(acrylic acid-co-distearin acrylate), in aqueous solution containing citric acid-coated superparamagnetic iron oxide nanoparticles (SPIONs), and followed by DOX loading via electrostatic attraction. To further functionalize these artificial vesicles with superior in vivo colloidal stability, pH-tunable drug release and active tumor-targeting, chitosan and poly(γ-glutamic acid-co-γ-glutamyl oxysuccinimide)-g-poly(ethyleneglycol)-folate (FA) were deposited in sequence onto the assembly outer surfaces. The interfacial nanogel layers via complementary electrostatic interactions and in-situ covalent cross-linking were thus produced. These nanogel-caged polymersomes (NCPs) show excellent anti-dilution and serum proteins-repellent behaviors. Triggerable release of the encapsulated DOX was governed by dual external stimuli, pH and temperature. When these theranostic NCPs were effectively internalized by HeLa cells via FA receptor-mediated endocytosis and then exposed to high frequency magnetic fields (HFMF), the combined effects of both pH and magnetic hyperthermia-triggered drug release and thermo-therapy resulted in greater cytotoxicity than the treatment by DOX alone. By virtue of the SPION clustering effect in the assembly inner aqueous compartments, the SPION/DOX-loaded NCPs displayed an r₂ relaxivity value (255.2 F emM⁻¹ S⁻¹) higher than Resovist (183.4 F emM⁻¹ S⁻¹), a commercial SPION-based T₂ contrast agent. The high magnetic relaxivity of the tumor-targeting NCPs coupled with their enhanced cellular uptake considerably promoted the MRI contrast of targeted cancer cells. These results demonstrate the great potential of the FA-decorated SPION/DOX-loaded NCPs as an advanced cancer theranostic nanodevice.

Dual stimuli-responsive polymeric hollow nanogels designed as carriers for intracellular triggered drug release.

Dual stimuli-responsive hollow nanogel spheres serving as an efficient intracellular drug delivery platform were obtained from the spontaneous coassociation of two graft copolymers into the vesicle architecture in aqueous phase. Both copolymers comprise acrylic acid (AAc) and 2-methacryloylethyl acrylate (MEA) units as the backbone and either poly(N-isopropylacrylamide) (PNIPAAm) alone or both PNIPAAm and monomethoxypoly(ethylene glycol) (mPEG) chain segments as the grafts. The assemblies were then subjected to covalent stabilization within vesicle walls with ester-containing cross-links by radical polymerization of MEA moieties, thereby leading to hollow nanogel particles. Taking the advantage of retaining a low quantity of payload within polymer layer-enclosed aqueous chambers through the entire loading process, doxorubicin (DOX) in the external bulk phase can be effectively transported into the gel membrane and bound therein via electrostatic interactions with ionized AAc residues and hydrogen-bond pairings with PNIPAAm grafts at pH 7.4. With the environmental pH being reduced (e.g., from 7.4 to 5.0) at 37 °C, the extensive disruption of AAc/DOX complexes due to the reduced ionization of AAc residues within the gel layer and the pronounced shrinkage of nanogels enable the rapid release of DOX species from drug-loaded hollow nanogels. By contrast, the drug liberation at 4 °C was severally restricted, particularly at pH 7.4 at which the DOX molecules remain strongly bound with ionized AAc residues and PNIPAAm grafts. The in vitro characterizations suggest that the DOX-loaded hollow nanogel particles after being internalized by HeLa cells via endocytosis can rapidly release the payload within acidic endosomes or lysosomes. This will then lead to significant drug accumulation in nuclei (within 1 h) and a cytotoxic effect comparable to free drug. This work demonstrates that the novel DOX-loaded hollow nanogel particles show great promise of therapeutic efficacy for potential anticancer treatment.

Superparamagnetic Hollow Hybrid Nanogels as a Potential Guidable Vehicle System of Stimuli-Mediated MR Imaging and Multiple Cancer Therapeutics

Hollow hybrid nanogels were prepared first by the coassembly of the citric acid-coated superparamagnetic iron oxide nanoparticles (SPIONs, 44 wt %) with the graft copolymer (56 wt %) comprising acrylic acid and 2-methacryloylethyl acrylate units as the backbone and poly(ethylene glycol) and poly(N-isopropylacrylamide) as the grafts in the aqueous phase of pH 3.0 in the hybrid vesicle structure, followed by in situ covalent stabilization via the photoinitiated polymerization of MEA residues within vesicles. The resultant hollow nanogels, though slightly swollen, satisfactorily retain their structural integrity while the medium pH is adjusted to 7.4. Confining SPION clusters to such a high level (44 wt %) within the pH-responsive thin gel layer remarkably enhances the transverse relaxivity (r2) and renders the MR imaging highly pH-tunable. For example, with the pH being adjusted from 4.0 to 7.4, the r2 value can be dramatically increased from 138.5 to 265.5 mM(-1) s(-1). The DOX-loaded hybrid nanogels also exhibit accelerated drug release in response to both pH reduction and temperature increase as a result of the substantial disruption of the interactions between drug molecules and copolymer components. With magnetic transport guidance toward the target and subsequent exposure to an alternating magnetic field, this DOX-loaded nanogel system possessing combined capabilities of hyperthermia and stimuli-triggered drug release showed superior in vitro cytotoxicity against HeLa cells as compared to the case with only free drug or hyperthermia alone. This work demonstrates that the hollow inorganic/organic hybrid nanogels hold great potential to serve as a multimodal theranostic vehicle functionalized with such desirable features as the guidable delivery of stimuli-mediated diagnostic imaging and hyperthermia/chemotherapies.

Active Tumor Permeation and Uptake of Surface Charge-Switchable Theranostic Nanoparticles for Imaging-Guided Photothermal/Chemo Combinatorial Therapy

To significantly promote tumor uptake and penetration of therapeutics, a nanovehicle system comprising poly(lactic-co-glycolic acid) (PLGA) as the hydrophobic cores coated with pH-responsive N-acetyl histidine modified D-α-tocopheryl polyethylene glycol succinate (NAcHis-TPGS) is developed in this work. The nanocarriers with switchable surface charges in response to tumor extracellular acidity (pHe) were capable of selectively co-delivering indocyanine green (ICG), a photothermal agent, and doxorubicin (DOX), a chemotherapy drug, to tumor sites. The in vitro cellular uptake of ICG/DOX-loaded nanoparticles by cancer cells and macrophages was significantly promoted in weak acidic environments due to the increased protonation of the NAcHis moieties. The results of in vivo and ex vivo biodistribution studies demonstrated that upon intravenous injection the theranostic nanoparticles were substantially accumulated in TRAMP-C1 solid tumor of tumor-bearing mice. Immunohistochemical examination of tumor sections confirmed the active permeation of the nanoparticles into deep tumor hypoxia due to their small size, pHe-induced near neutral surface, and the additional hitchhiking transport via tumor-associated macrophages. The prominent imaging-guided photothermal therapy of ICG/DOX-loaded nanoparticles after tumor accumulation induced extensive tumor tissue/vessel ablation, which further promoted their extravasation and DOX tumor permeation, thus effectively suppressing tumor growth.

Indocyanine Green-Encapsulated Hybrid Polymeric Nanomicelles for Photothermal Cancer Therapy

Indocyanine green (ICG), an FDA approved medical near-infrared (NIR) imaging agent, has been extensively used in cancer theranosis. However, the limited aqueous photostability, rapid body clearance, and poor cellular uptake severely restrict its practical applications. For these problems to be overcome, ICG-encapsulated hybrid polymeric nanomicelles (PNMs) were developed in this work through coassociation of the amphiphilic diblock copolymer poly(lactic-co-glycolic acid)-b-poly(ethylene glycol) (PLGA-b-PEG) and hydrophobic electrostatic complexes composed of ICG molecules and branched poly(ethylenimine) (PEI). The ICG-encapsulated hybrid PNMs featured a hydrophobic PLGA/ICG/PEI core stabilized by hydrophilic PEG shells. The encapsulation of electrostatic ICG/PEI complexes into the compact PLGA-rich core not only facilitated the ICG loading but also promoted its aqueous optical stability. The effects of the chain length of PEI in combination with ICG on the physiochemical properties of PNMs and their drug leakage were also investigated. PEI(10k) (10 kDa) could form highly robust and dense complexes with ICG, and thus prominently reduced ICG outflow from the PNMs. The results of in vitro cellular uptake and cytotoxicity studies revealed that the ICG/PEI(10k)-loaded PNMs significantly promoted cellular uptake of ICG by HeLa cells due to their near-neutral surface, and thereby augmented the NIR-triggered hyperthermia effect in destroying cancer cells. These findings strongly indicate that the ICG/PEI10k-loaded PNMs have significant potential for attaining effective cancer imaging and photothermal therapy.

Nano-scaled pH-responsive polymeric vesicles for intracellular release of doxorubicin

Polymeric vesicles produced by spontaneous self-association of poly(acrylic acid-co-distearin acrylate) (poly(AAc-co-DSA)) with varying ratios of AAc and DSA units in aqueous solution of pH 5.0 exhibit the pH-regulated drug release behavior. Through the electrostatic interaction with ionized AAc residues, doxorubicin (DOX) molecules can be highly accommodated onto either the inner or outer surfaces of vesicles when the pH is adjusted from 5.0 to 7.4. The extent of DOX encapsulation is dependent largely on the structural transition of vesicles in response to the pH change. While the pH-evolved drug release profile varies to some extent with the distribution of DOX molecules within vesicles, the drug release from vesicles is accelerated significantly via the disruption of the electrostatic interaction of DOX species with ionized AAc moieties at pH 5.0. The DOX-loaded polymeric vesicles show promoted cellular uptake and cytotoxicity comparable to free DOX for HeLa cells. This indicates that they are probably taken up by the cells via the lipid raft-mediated endocytosis.

Monocytic delivery of therapeutic oxygen bubbles for dual-modality treatment of tumor hypoxia

Photodynamic therapy (PDT) is a powerful technique photochemically tailored for activating apoptosis of malignant cells. Although PDT has shown promise in several clinical applications, malignant cells in hypoxic regions are often resistant to PDT due to the transport limitation of therapeutics and the oxygen-dependent nature of PDT. Herein, we present an innovative strategy for overcoming the limits of PDT in tumor hypoxia using bone marrow-derived monocytes as cellular vehicles for co-transport of oxygen and red light activatable photosensitizer, chlorin e6 (Ce6). Superparamagnetic iron oxide nanoparticle/Ce6/oxygen-loaded polymer bubbles were prepared and internalized into tumortropic monocytes. These functional bubbles were found harmless to cellular hosts without external triggers. Nevertheless, the therapeutic monocytes exhibited a superior performance in inhibiting tumor growth on Tramp-C1 tumor-bearing mice (C57BL/6J) upon the treatments of tumors with high frequency magnetic field and red light laser (660 nm). Histological examinations of the tumor sections confirmed the successful cellular transport of therapeutic payloads to tumor hypoxia and the pronounced antitumor effect elicited by combined hyperthermia/photodynamic therapy along with the additional oxygen supply. This work demonstrates that this oxygen/therapeutic co-delivery via tumortropic monocytes toward tumor hypoxia is promising for improving PDT efficacy.

pH-Responsive therapeutic solid lipid nanoparticles for reducing P-glycoprotein-mediated drug efflux of multidrug resistant cancer cells.

In this study, a novel pH-responsive cholesterol-PEG adduct-coated solid lipid nanoparticles (C-PEG-SLNs) carrying doxorubicin (DOX) capable of overcoming multidrug resistance (MDR) breast cancer cells is presented. The DOX-loaded SLNs have a mean hydrodynamic diameter of ~100 nm and a low polydispersity index (under 0.20) with a high drug-loading efficiency ranging from 80.8% to 90.6%. The in vitro drug release profiles show that the DOX-loaded SLNs exhibit a pH-controlled drug release behavior with the maximum and minimum unloading percentages of 63.4% at pH 4.7 and 25.2% at pH 7.4, respectively. The DOX-loaded C-PEG-SLNs displayed a superior ability in inhibiting the proliferation of MCF-7/MDR cells. At a DOX concentration of 80 μM, the cell viabilities treated with C-PEG-SLNs were approximately one-third of the group treated with free DOX. The inhibition activity of C-PEG-SLNs could be attributed to the transport of C-PEG to cell membrane, leading to the change of the composition of the cell membrane and thus the inhibition of permeability glycoprotein activity. This hypothesis is supported by the confocal images showing the accumulation of DOX in the nuclei of cancer cells and the localization of C-PEG on the cell membranes. The results of in vivo study further demonstrated that the DOX delivered by the SLNs accumulates predominantly in tumor via enhanced permeability and retention effect, the enhanced passive tumor accumulation due to the loose intercellular junctions of endothelial cells lining inside blood vessels at tumor site, and the lack of lymphatic drainage. The growth of MCF-7/MDR xenografted tumor on Balb/c nude mice was inhibited to ~400 mm3 in volume as compared with the free DOX treatment group, 1,140 mm3, and the group treated with 1,2 distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)] solid lipid nanoparticles, 820 mm3. Analysis of the body weight of nude mice and the histology of organs and tumor after the administration of DOX-loaded SLNs show that the SLNs have no observable side effects. These results indicate that the C-PEG-SLN is a promising platform for the delivery of therapeutic agents for MDR cancer chemotherapy.

Dual-layered nanogel-coated hollow lipid/polypeptide conjugate assemblies for potential pH-triggered intracellular drug release.

To achieve effective intracellular anticancer drug delivery, the polymeric vesicles supplemented with the pH-responsive outlayered gels as a delivery system of doxorubicin (DOX) were developed from self-assembly of the lipid/polypeptide adduct, distearin grafted poly(γ-glutamic acid) (poly(γ-GA)), followed by sequential deposition of chitosan and poly(γ-GA-co-γ-glutamyl oxysuccinimide)-g-monomethoxy poly(ethylene glycol) in combination with in situ covalent cross-linking on assembly surfaces. The resultant gel-caged polymeric vesicles (GCPVs) showed superior performance in regulating drug release in response to the external pH change. Under typical physiological conditions (pH 7.4 and 37°C) at which the γ-GA/DOX ionic pairings remained mostly undisturbed, the dense outlayered gels of GCPVs significantly reduced the premature leakage of the uncomplexed payload. With the environmental pH being reduced from pH 7.4 to 4.7, the drug liberation was appreciably promoted by the massive disruption of the ionic γ-GA/DOX complexes along with the significant swelling of nanogel layers upon the increased protonation of chitosan chain segments. After being internalized by HeLa cells via endocytosis, GCPVs exhibited cytotoxic effect comparable to free DOX achieved by rapidly releasing the payload in intracellular acidic endosomes and lysosomes. This strongly implies the great promise of such unique GCPVs as an intracellular drug delivery carrier for potential anticancer treatment.

Tumortropic adipose-derived stem cells carrying smart nanotherapeutics for targeted delivery and dual-modality therapy of orthotopic glioblastoma

&NA; Chemotherapy is typically used to treat malignant brain tumors, especially for the tumors in surgically inaccessible areas. However, owing to the existence of blood‐brain barrier (BBB), the tumor accumulation and therapeutic efficacy of clinical therapeutics is still of great concerns. To this end, we present herein a prominent therapeutic strategy adopting adipose‐derived stem cells (ADSCs) capable of carrying nanotherapeutic payloads selectively toward brain tumors for thermo/chemotherapy. The nanoparticle (NP) payload was obtained from co‐assembly of poly(&ggr;‐glutamic acid‐co‐distearyl &ggr;‐glutamate) with poly(lactic‐co‐glycolic acid), paclitaxel (PTX), and oleic acid‐coated superparamagnetic iron oxide NPs in aqueous solution. The particle size and drug loading content were ca 110 nm and 8.4 wt%, respectively. After being engulfed by ADSCs, the nanotherapeutics was found rather harmless to cellular hosts at a PTX concentration of 30 &mgr;M over 48 h in the absence of pertinent stimulus. Nevertheless, the ADSC‐based approach combined with high frequency magnetic field exhibits a sound therapeutic performance with a 4‐fold increase in therapeutic index on brain astrocytoma (ALTS1C1)‐bearing mice (C57BL/6 J) as compared to the typical chemotherapy using a current first‐line chemodrug, temozolomide. Immunohistochemical examination of brain tumor sections confirms the successful cellular transport and pronounced cytotoxic action of therapeutics against tumor cells in vivo. This work demonstrates the promise of ADSC‐mediated chemo/thermal therapy against brain tumors. Graphical abstract Figure. No caption available.