Hybrid Biodegradable Nanomotors through Compartmentalized Synthesis.

Designer particles that are embued with nanomachinery for autonomous motion have great potential for biomedical applications; however, their development is highly demanding with respect to biodegradability/compatibility. Previously, biodegradable propulsive machinery based on enzymes has been presented. However, enzymes are highly susceptible to proteolysis and deactivation in biological milieu. Biodegradable hybrid nanomotors powered by catalytic inorganic nanoparticles provide a proteolytically stable alternative to those based upon enzymes. Herein we describe the assembly of hybrid biodegradable nanomotors capable of transducing chemical energy into motion. Such nanomotors are constructed through a process of compartmentalized synthesis of inorganic MnO2 nanoparticles (MnPs) within the cavity of organic stomatocytes. We show that the nanomotors remain active in cellular environments and do not compromise cell viability. Effective tumor penetration of hybrid nanomotors is also demonstrated in proof-of-principle experiments. Overall, this work represents a new prospect for engineering of nanomotors that can retain their functionality within biological contexts.

ATP-Mediated Transient Behavior of Stomatocyte Nanosystems.

In nature, dynamic processes are ubiquitous and often characterized by adaptive, transient behavior. Herein, we present the development of a transient bowl-shaped nanoreactor system, or stomatocyte, the properties of which are mediated by molecular interactions. In a stepwise fashion, we couple motility to a dynamic process, which is maintained by transient events; namely, binding and unbinding of adenosine triphosphate (ATP). The surface of the nanosystem is decorated with polylysine (PLL), and regulation is achieved by addition of ATP. The dynamic interaction between PLL and ATP leads to an increase in the hydrophobicity of the PLL-ATP complex and subsequently to a collapse of the polymer; this causes a narrowing of the opening of the stomatocytes. The presence of the apyrase, which hydrolyzes ATP, leads to a decrease of the ATP concentration, decomplexation of PLL, and reopening of the stomatocyte. The competition between ATP input and consumption gives rise to a transient state that is controlled by the out-of-equilibrium process.

Facile Formation of Gold-Nanoparticle-Loaded γ-Polyglutamic Acid Nanogels for Tumor Computed Tomography Imaging.

The formation of gold nanoparticle (Au NP)-loaded γ-polyglutamic acid (γ-PGA) nanogels (NGs) for computed tomography (CT) imaging of tumors is reported. γ-PGA with carboxyl groups activated by 1-ethyl-3-[3-(dimethylamino)propyl] carbodiimide hydrochloride is first emulsified to form NGs and then in situ chemically cross-linked with polyethylenimine (PEI)-entrapped Au NPs with partial polyethylene glycol (PEG) modification ([(Au0)200-PEI·NH2-mPEG]). The formed γ-PGA-[(Au0)200-PEI·NH2-mPEG] NGs with a size of 108.6 ± 19.1 nm display an X-ray attenuation property better than commercial iodinated small-molecular-contrast agents and can be uptaken by cancer cells more significantly than γ-PGA-stabilized single Au NPs at the same Au concentrations. These properties render the formed NGs with an ability to be used as an effective contrast agent for the CT imaging of cancer cells in vitro and a tumor model in vivo. The developed hybrid NGs may be promising for the CT imaging or theranostics of different biosystems.

Injectable alginate hydrogels for synergistic tumor combination therapy through repolarization of tumor-associated macrophages.

Locally administered drug delivery systems are promising as they allow to circumvent the side effects associated with systematic administration. In this study, we constructed multifunctional hydrogels by simply mixing commercial alginate (ALG) sols with glucose oxidase (GOx)-conjugated polyacrylic acid-stabilized iron oxide nanoparticles (GPI NPs) and Toll-like receptor 7/8 agonist resiquimod (R848). The injectable sols were able to transform into hydrogels (GPI/R848@ALG) by the ionic cross-linking between ALG and physiological Ca2+ to trap the therapeutic components within the hydrogel framework. Upon intratumoral injection, the hydrogels were employed for starvation therapy, promoted chemodynamic therapy and tumor-associated macrophages (TAMs) repolarization. The energy supply was blocked by consuming the intratumoral glucose via the GOx-catalyzed conversion of glucose into gluconic acid and hydrogen peroxide (H2O2).In vitro results showed that the generated H2O2 could be further converted into highly cytotoxic hydroxyl radicals (·HO) by the Fenton reaction to induce enhanced chemodynamic therapy. The TAMs repolarization studies in vitro exhibited that the GPI/R848@ALG hydrogels up-regulated the expression of CD86 by 63% and down-regulated the proportion of CD206 by 14% with a synergistic effect of the presence of Fe3O4 and R848, suggesting that the multifunctional hydrogels exert functions to direct the remodeling of TAMs from the tumor supportive M2-like phenotype to the tumor destructive M1-like phenotype to further contribute to the antitumor effect. Moreover, both in vitro and in vivo experiments demonstrate that the multifunctional hydrogels exhibit admirable antitumor performance towards 4T1 tumors. This work thereby provides a promising multifunctional nanoplatform for synergistic cancer starvation therapy, chemodynamic therapy and TAMs repolarization.

Surface-Charge-Switchable Nanoclusters for Magnetic Resonance Imaging-Guided and Glutathione Depletion-Enhanced Photodynamic Therapy.

Photodynamic therapy (PDT) is an effective noninvasive therapeutic method that employs photosensitizers (PSs) converting oxygen to highly cytotoxic singlet oxygen (1O2) under light irradiation. The conventional PDT efficacy is, however, compromised by the nonspecific delivery of PSs to tumor tissue, the hypoxic tumor microenvironment, and the reduction of generated 1O2 by the intracellular antioxidant glutathione (GSH). Herein, an intelligent multifunctional synergistic nanoplatform (CMGCC) for T1-weighted magnetic resonance (MR) imaging-guided enhanced PDT is presented, which consists of nanoparticles composed of catalase (CAT) and manganese dioxide (MnO2) that are integrated within chlorin-e6-modified glycol chitosan (GC) polymeric micelles. In this system, (1) GC polymers with pH-sensitive surface charge switchability from neutral to positive could improve the PS accumulation within the tumor region, (2) CAT could effectively reoxygenate the hypoxic tumor via catalyzing endogenous hydrogen peroxide to O2, and (3) MnO2 could consume the intracellular GSH while simultaneously producing Mn2+ as a contrast agent for T1-weighted MR imaging. The CMGCC particles possess uniform size distribution, well-defined structure, favorable enzyme activity, and superior 1O2 generation ability. Both in vitro and in vivo experiments demonstrate that the CMGCC exhibit significantly enhanced PDT efficacy toward HeLa cells and subcutaneous HeLa tumors. Our study thereby demonstrates this to be a promising synergistic theranostic nanoplatform with highly efficient PDT performance for cancer therapy.

Multifunctional PVCL nanogels with redox-responsiveness enable enhanced MR imaging and ultrasound-promoted tumor chemotherapy.

Development of versatile nanoplatforms that simultaneously integrate therapeutic and diagnostic features for stimuli-responsive delivery to tumors remains a great challenge. In this work, we report a novel intelligent redox-responsive hybrid nanosystem composed of MnO2 nanoparticles (NPs) and doxorubicin (DOX) co-loaded within poly(N-vinylcaprolactam) nanogels (PVCL NGs) for magnetic resonance (MR) imaging-guided and ultrasound-targeted microbubble destruction (UTMD)-promoted tumor chemotherapy. Methods: PVCL NGs were first synthesized via a precipitation polymerization method, decorated with amines using ethylenediamine, and loaded with MnO2 NPs through oxidation with permanganate and DOX via physical encapsulation and Mn-N coordination bonding. The as-prepared DOX/MnO2@PVCL NGs were well characterized. UTMD-promoted cellular uptake and therapeutic efficacy of the hybrid NGs were assessed in vitro, and a xenografted tumor model was used to test the NGs for MR imaging and UTMD-promoted tumor therapy in vivo.Results: The as-prepared DOX/MnO2@PVCL NGs with a size of 106.8 nm display excellent colloidal stability, favorable biocompatibility, and redox-responsiveness to the reductive intracellular environment and tumor tissues having a relatively high glutathione (GSH) concentration that can trigger the synchronous release of Mn2+ for enhanced T1-weighted MR imaging and DOX for enhanced cancer chemotherapy. Moreover, the DOX/MnO2@PVCL NGs upon the UTMD-promotion exhibit a significantly enhanced tumor growth inhibition effect toward subcutaneous B16 melanoma owing to the UTMD-improved cellular internalization and tumor penetration. Conclusion: Our work thereby proposes a promising theranostic nanoplatform for stimuli-responsive T1-weighted MR imaging-guided tumor chemotherapy.

Pathway dependent shape-transformation of azide-decorated polymersomes.

Here we report the shape transformation of poly(ethylene glycol)-polystyrene (PEG-PS) polymersomes into ordered inverse morphologies, directed by the salt concentration of the medium and the presence of azide groups on the polymersome surface. The azide moieties introduced at the chain ends of the PEG blocks induce a difference in hydrodynamic volume of the hydrophilic domains at the inner and outer side of the vesicular membrane, allowing control over its spontaneous curvature and hence the pathway of shape deformation. This simple modification enables access to intricate morphologies which are traditionally only accessible via the application of complex polymer building blocks.

Influence of size, crosslinking degree and surface structure of poly(N-vinylcaprolactam)-based microgels on their penetration into multicellular tumor spheroids.

Current nanomedicine suffers from a big challenge due to the fact that most of the nanocarrier systems lack the desired tumor penetration depth, thereby limiting their clinical translation. Unlike the nanomaterials with a similar size or shape, microgels display excellent softness, fluidity and deformability, as well as stimuli-responsiveness in the tumor microenvironment. Herein, we report the synthesis of temperature-responsive poly(N-vinylcaprolactam)/oligo (ethylene glycol) acrylate/glycidyl methacrylate (PVCL/OEGA/GMA) microgels with different hydrodynamic radii (100-500 nm), crosslinking densities, 2-methoxyethyl acrylate (MEA) contents and OEGA chain lengths using a precipitation polymerization method and the investigation of the microgels in terms of their tumor penetration capability using a multicellular tumor spheroid (MCTS) model. The prepared microgels were well characterized with different techniques. We show that regardless of the size, crosslinking density, MEA content and OEGA chain length, all microgels display the desired cytocompatibility in the given concentration range. In vitro cellular uptake data reveal that similar to 2-dimensional (2-D) adherent cells, microgels with a smaller size display more enhanced cellular uptake than those having a larger size in the 3-D MCTS model. Likewise, 3-D MCTS penetration results indicate that the PVCL/OEGA/GMA microgels with the smallest radius of 100 nm exhibit the deepest penetration length. We then selected the microgels with a radius of 200 nm but with different physicochemical parameters to investigate their cellular uptake and tumor penetration behavior. Our data show that microgels with varying crosslinking densities, MEA contents and OEGA chain lengths do not have any appreciable changes in terms of their cellular uptake and penetration in the 3-D MCTS model. Our study provides new insights for the design of different microgel-based systems for further cancer theranostic applications.

Single enzyme loaded nanoparticles for combinational ultrasound-guided focused ultrasound ablation and hypoxia-relieved chemotherapy.

Constructing nanosystems that synergistically combine therapeutic and diagnostic features is of great interest to the nanomedicine community but also remains a tremendous challenge. Methods: In this work, we report novel catalytic nanoparticles composed of the enzyme catalase, encapsulated in a polymer shell and surface decorated with pH-sensitive poly(ethylene glycol) (PEGylated nCAT). These nanoparticles were used as a promoter for ultrasound (US)-guided focused ultrasound (FUS) ablation and hypoxia alleviation for application in Doxorubicin-based chemotherapy. Results: The PEGylated nCAT produced highly effectively O2 from endogenous H2O2 to ameliorate the hypoxic and therefore poor-acoustic tumor environment. The generated O2 was utilized as 1) a contrast agent for US imaging; 2) strengthening agent for FUS ablation and 3) normoxia inducer to enhance chemotherapeutic efficacy. The PEGylated nCAT exhibited favorable enzyme activity after long-term storage, and after exposure to proteolytic conditions and elevated temperatures. The pH-responsive PEGylation contributed on the one hand to an extended in vivo circulation time over 48 h and on the other hand enabled PEG cleavage in the vicinity of cancer cells to facilitate cellular uptake. Conclusion: The developed PEGylated nCAT can therefore effectively combine US-guided FUS and chemotherapy and can be regarded as a highly promising theranostic platform.

A unique nanogel-based platform for enhanced dual mode tumor MR/CT imaging.

We develop a convenient approach to loading both gold nanoparticles (AuNPs) and gadolinium (Gd) within alginate nanogels (AG NGs) for enhanced tumor dual-modal MR/CT imaging applications. In this study, polyethyleneimine (PEI) partially modified with polyethylene glycol (PEG) was used to entrap AuNPs and load gadolinium via chelation. The formed PEI-Au-Gd NPs were used as a crosslinker to crosslink AG NGs with activated carboxyl groups obtained through a double emulsion process. The formed hybrid NGs (AG/PEI-Au-Gd NGs) having a size of 83 ± 21 nm exhibit excellent colloidal stability in aqueous solution and good cytocompatibility in the studied concentration range. In particular, the AG/PEI-Au-Gd NGs exhibit a higher r1 relaxivity (9.16 mM-1 s-1) than acetylated PEI-Au-Gd NPs (PEI.Ac-Au-Gd NPs) and a clinical MR contrast agent and a greater X-ray attenuation performance than conventional iodinated CT contrast agents (e.g., Omnipaque), and they can be more significantly taken up by cancer cells than PEI.Ac-Au-Gd NPs. Furthermore, the AG/PEI-Au-Gd NGs enable effective dual mode MR/CT imaging of cancer cells in vitro as well as a subcutaneous tumor model in vivo. Strikingly, the AG/PEI-Au-Gd NGs exhibit a much better dual-modal MR/CT imaging performance than PEI.Ac-Au-Gd NPs and clinical CT or MR agents in in vivo tumor imaging. The developed AG/PEI-Au-Gd NGs with good biosafety confirmed by histological examinations may be potentially employed as an efficient contrast agent for enhanced dual-modal MR/CT imaging applications.

Polyaniline-loaded γ-polyglutamic acid nanogels as a platform for photoacoustic imaging-guided tumor photothermal therapy.

We report the facile synthesis of polyaniline (PANI)-loaded γ-polyglutamic acid (γ-PGA) nanogels (NGs) for photoacoustic (PA) imaging-guided photothermal therapy (PTT) of tumors. In this work, γ-PGA NGs were first formed via a double emulsion approach, followed by crosslinking with cystamine dihydrochloride (Cys) via 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride coupling chemistry. The formed γ-PGA/Cys NGs were employed as a nanoreactor to load aniline monomers via an electrostatic interaction for subsequent in situ polymerization in the presence of ammonium persulfate. The resulting γ-PGA/Cys@PANI NGs were thoroughly characterized. It is shown that the γ-PGA/Cys@PANI NGs with an average size of 71.9 nm are dispersible in water, colloidally stable, and cytocompatible and hemocompatible in the concentration range studied. The strong near-infrared (NIR) absorbance renders the NGs with good PA imaging contrast enhancement and photothermal conversion properties. With these excellent properties and biocompatibility, the developed γ-PGA/Cys@PANI NGs are able to be used for PA imaging-guided PTT of cancer cells in vitro and a xenografted tumor model in vivo. This unique theranostic nanoplatform may be further loaded with other imaging or therapeutic elements, or modified with targeting ligands, thereby providing a ubiquitous platform for multimode imaging and combinational therapy of different biosystems.

PEGylated polyethylenimine-entrapped gold nanoparticles loaded with gadolinium for dual-mode CT/MR imaging applications.

AIM: To synthesize and characterize cost-efficient polyethylenimine-entrapped gold nanoparticles loaded with gadolinium (Gd@Au PENPs) for dual-mode computed tomography (CT)/magnetic resonance (MR) imaging applications. MATERIALS & METHODS: PEGylated PEI modified with gadolinium (Gd) chelator (DOTA) was used as a template to synthesize the Gd@Au PENPs and the particles were well characterized in terms of their physicochemical properties, cytotoxicity and performances in CT and MR imaging in vitro and in vivo. RESULTS: The formed Gd@Au PENPs with low cytotoxicity can be used as a highly efficient contrast agent for dual-mode CT/MR imaging of blood pool and major organs of animals. CONCLUSION: The designed Gd@Au PENPs may be used as a versatile nanoplatform for dual-mode CT/MR imaging of different biological systems.

PEGylated polyethylenimine-entrapped gold nanoparticles modified with folic acid for targeted tumor CT imaging.

Development of various cost-effective contrast agents for targeted tumor computed tomography (CT) imaging still remains a great challenge. Herein, we present a facile approach to forming folic acid (FA)-targeted multifunctional gold nanoparticles (AuNPs) using cost-effective branched polyethylenimine (PEI) modified with polyethylene glycol (PEG) as a template for tumor CT imaging applications. In this work, PEI sequentially modified with PEG monomethyl ether, FA-linked PEG, and fluorescein isothiocyanate was used as a template to synthesize AuNPs, followed by transformation of the remaining PEI surface amines to acetamides. The formed FA-targeted PEI-entrapped AuNPs (FA-Au PENPs) were fully characterized. We show that the formed FA-Au PENPs with an Au core size of 2.1 nm are water soluble, colloidally stable, and non-cytotoxic in a given concentration range. Flow cytometry and confocal microscopy data reveal that the FA-Au PENPs are able to target cancer cells overexpressing FA receptors (FAR). Importantly, the developed FA-Au PENPs can be used as a nanoprobe for targeted CT imaging of FAR-expressing cancer cells in vitro and the xenografted tumor model in vivo. With the demonstrated biocompatibility by organ biodistribution and histological studies, the designed FA-Au PENPs may hold great promise to be used as a nanoprobe for CT imaging of different FAR-overexpressing tumors.

LAPONITE®-stabilized iron oxide nanoparticles for in vivo MR imaging of tumors.

We report the synthesis, characterization and utilization of LAPONITE®-stabilized magnetic iron oxide nanoparticles (LAP-Fe3O4 NPs) as a high performance contrast agent for in vivo magnetic resonance (MR) detection of tumors. In this study, Fe3O4 NPs were synthesized by a facile controlled coprecipitation route in LAP solution, and the formed LAP-Fe3O4 NPs have great colloidal stability and about 2-fold increase of T2 relaxivity than Fe3O4 NPs (from 247.6 mM(-1) s(-1) to 475.9 mM(-1) s(-1)). Moreover, cytotoxicity assay and cell morphology observation demonstrate that LAP-Fe3O4 NPs display good biocompatibility in the given Fe concentration range, and in vivo biodistribution results prove that NPs can be metabolized and cleared out of the body. Most importantly, LAP-Fe3O4 NPs can not only be used as a contrast agent for MR imaging of cancer cells in vitro due to the effective uptake by tumor cells, but also significantly enhance the contrast of a xenografted tumor model. Therefore, the developed LAP-based Fe3O4 NPs with good colloidal stability and exceptionally high transverse relaxivity may have tremendous potential in MR imaging applications.

Immobilization of iron oxide nanoparticles within alginate nanogels for enhanced MR imaging applications.

We report the design of iron oxide (Fe3O4) nanoparticle (NP)-immobilized alginate (AG) nanogels (NGs) as a novel contrast agent for enhanced magnetic resonance (MR) imaging applications. In this study, an aqueous solution of AG activated by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride was double emulsified to form NGs, followed by in situ cross-linking with polyethyleneimine (PEI)-coated Fe3O4 NPs (PEI-Fe3O4 NPs). The resultant Fe3O4 NP-immobilized AG NGs (AG/PEI-Fe3O4 NGs) were characterized via different techniques. Our results reveal that the hybrid NGs with a size of 186.1 ± 33.1 nm are water dispersible, colloidally stable, and cytocompatible in the given concentration range. Importantly, these NGs have a high r2 relaxivity (170.87 mM(-1) s(-1)) due to the high loading of Fe3O4 NPs within the NGs, and can be more significantly uptaken by cancer cells when compared with carboxylated Fe3O4 NPs. The formed AG/PEI-Fe3O4 NGs are able to be used as an effective contrast agent for the MR imaging of cancer cells in vitro and the xenografted tumor model in vivo after intravenous injection. The developed AG/PEI-Fe3O4 NGs may hold great promise for use as a novel contrast agent for the enhanced MR imaging of different biological systems.

Formation of iron oxide nanoparticle-loaded γ-polyglutamic acid nanogels for MR imaging of tumors.

We report a facile approach to form iron oxide nanoparticle (NP)-loaded γ-polyglutamic acid (γ-PGA) nanogels (NGs) for MR imaging of tumors. In this study, γ-PGA with carboxyl groups activated by 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC) in aqueous solution was firstly emulsified, followed by in situ chemical crosslinking with polyethyleneimine (PEI)-coated iron oxide NPs (PEI-Fe3O4 NPs) with a core size of 8.9 ± 2.1 nm synthesized via a mild reduction route. The formed γ-PGA NGs containing iron oxide NPs (γ-PGA/PEI-Fe3O4 NGs) with a size of 152.3 ± 13.1 nm are water-dispersible, colloidally stable, noncytotoxic in a given concentration range, and display a r2 relaxivity of 171.1 mM-1 s-1. Likewise, the hybrid NGs can be taken up by cancer cells with the uptake of Fe significantly higher than single Fe3O4 NPs. These properties render the formed γ-PGA/PEI-Fe3O4 NGs with an ability to be used as an effective contrast agent for MR imaging of cancer cells in vitro and the xenografted tumor model in vivo via the passive enhanced permeability and retention effect after intravenous injection. The developed γ-PGA/PEI-Fe3O4 hybrid NGs may hold great promise to be used as a novel contrast agent for MR imaging or other theranostic applications.