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We report a facile approach for fabrication of Fe3O4@Au nanocomposite particles (NCPs) as a dual mode contrast agent for both magnetic resonance (MR) and computed tomography (CT) imaging applications. In this study, Fe3O4 nanoparticles (NPs) prepared by a controlled coprecipitation approach were used as core particles for subsequent electrostatic layer-by-layer (LbL) assembly of poly(γ-glutamic acid) (PGA) and poly(L-lysine) (PLL) to form PGA/PLL/PGA multilayers, followed by assembly with dendrimer-entrapped gold NPs (Au DENPs) formed using amine-terminated generation 5 poly(amidoamine) dendrimers as templates. After crosslinking the multilayered shell of PGA/PLL/PGA/Au DENPs via EDC chemistry, the remaining amine groups of the outermost layer of Au DENPs were acetylated to neutralize the surface charge of the particles. The formed Fe3O4@Au NCPs were well characterized via different techniques. We show that the formed Fe3O4@Au NCPs are colloidally stable, hemocompatible, and biocompatible in the given concentration range (0–100 μg mL−1). The relatively high r2 relaxivity (71.55 mM−1 s−1) and enhanced X-ray attenuation property when compared with either the uncoated Fe3O4 NPs or the Au DENPs afford the developed Fe3O4@Au NCPs with a capacity not only for dual mode CT and MR imaging of cells in vitro, but also for MR imaging of liver and CT imaging of subcutaneous tissue in vivo. With the facile integration of both Fe3O4 NPs and Au DENPs within one particle system via the LbL assembly technique and dendrimer chemistry, it is expected that the fabricated Fe3O4@Au NCPs may be further modified with multifunctionalities for multi-mode imaging of various biological systems.

We report the fabrication of uniform electrospun poly(lactic-co-glycolic acid) (PLGA) nanofibers incorporated with laponite (LAP) nanodisks, a synthetic clay material for osteogenic differentiation of human mesenchymal stem cells (hMSCs). In this study, a solution mixture of LAP suspension and PLGA was electrospun to form composite PLGA–LAP nanofibers with different LAP doping levels. The PLGA–LAP composite nanofibers formed were systematically characterized via different techniques. We show that the incorporation of LAP nanodisks does not significantly change the uniform PLGA fiber morphology, instead significantly improves the mechanical durability of the nanofibers. Compared to LAP-free PLGA nanofibers, the surface hydrophilicity and protein adsorption capacity of the composite nanofibers slightly increase after doping with LAP, while the hemocompatibility of the fibers does not appreciably change. The cytocompatibility of the PLGA–LAP composite nanofibers was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay of L929 mouse fibroblasts and porcine iliac artery endothelial cells cultured onto the surface of the nanofibers. The results reveal that the incorporated LAP is beneficial to promote the cell adhesion and proliferation to some extent likely due to the improved surface hydrophilicity and protein adsorption capability of the fibers. Finally, the PLGA–LAP composite nanofibers were used as scaffolds for osteogenic differentiation of hMSCs. We show that both PLGA and PLGA–LAP composite nanofibers are able to support the osteoblast differentiation of hMSCs in osteogenic medium. Most strikingly, the doped LAP within the PLGA nanofibers is able to induce the osteoblast differentiation of hMSCs in growth medium without any inducing factors. The fabricated smooth and uniform organic–inorganic hybrid LAP-doped PLGA nanofibers may find many applications in the field of tissue engineering.

We report a facile approach to immobilizing gold nanoparticles (AuNPs) into electrospun polyethyleneimine (PEI)/polyvinyl alcohol (PVA) nanofibers for catalytic applications. In this study, electrospun PEI/PVA nanofibers with a mean diameter of 490 nm were first crosslinked with glutaraldehyde vapor to render them water stable. Then, the water-insoluble nanofibrous mats were used as nanoreactors to complex AuCl4− anions via binding with the free amine groups of PEI for subsequent formation and immobilization of AuNPs. The formed AuNPs with a diameter of 11.8 nm within the nanofibers do not significantly change the morphology of the nanofibers; while importantly the mechanical property of the fibers was greatly improved compared to the crosslinked fibers without AuNPs. Scanning electron microscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, energy dispersive spectroscopy, and thermogravimetric analysis were used to characterize these hybrid nanofibers. Furthermore, we show that the AuNP-containing nanofibers display an excellent catalytic activity and reusability for the transformation of 4-nitrophenol to 4-aminophenol. The present approach to fabricating AuNP-containing nanofibers may be extended for producing other nanoparticle-containing composite nanofibrous materials for various applications in catalysis, sensing, and biomedical sciences.

We describe a unique approach to combining two kinds of radiodense elements, gold and iodine, within one single dendrimer-based nanodevice with an enhanced X-ray attenuation property for potential computed tomography (CT) imaging applications. In this approach, amine-terminated generation 5 poly(amidoamine) dendrimers were used as templates for the entrapped synthesis of gold nanoparticles (AuNPs). The dendrimer-entrapped AuNPs (Au DENPs) were then conjugated with diatrizoic acid (DTA) via an EDC coupling reaction, resulting in the loading of 59 DTA molecules on average within each Au DENP nanodevice, where only 13 DTA molecules were covalently attached onto the surface of each dendrimer. The formed Au DENP–DTA nanocomplexes possessed a good stability in aqueous solution. X-ray absorption coefficient measurements reveal that the attenuation effect of Au DENP–DTA is much higher than that of both the commercial iodine-based contrast agent at the same iodine concentration and pure Au DENPs at the same gold concentration. With the prolonged circulation time of NPs, the Au DENP–DTA nanocomplex is expected to have a high efficacy as a contrast agent in dynamic CT imaging and angiography. This work demonstrates for the first time the enhancing effect of two different radiodense elements within the architecture of one contrast agent, presenting a novel concept for designing high-performance contrast agents for biomedical CT imaging applications.

A new approach to immobilizing zero-valent iron nanoparticles (ZVI NPs) into electrospun polymer nanofibers with enhanced mechanical properties for environmental applications is presented. In this approach, multiwalled carbon nanotubes (MWCNTs) are mixed with polyacrylic acid (PAA)/polyvinyl alcohol (PVA) mixture polymer solution for subsequent electrospinning to form uniform nanofibers. The MWCNT-incorporated PAA/PVA nanofibers are crosslinked and then used as a nanoreactor to complex Fe(III) ions through binding with the PAA carboxyl groups for the reductive formation of ZVI NPs. The MWCNT-incorporated PAA/PVA nanofibers before and after immobilization with ZVI NPs are characterized using scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and mechanical property measurements. We show that the mechanical properties of uniform nanofibrous mats with and without ZVI NPs are significantly enhanced even with only 1.0 wt% MWCNTs incorporated. The MWCNT-reinforced PAA/PVA nanofibrous mats containing ZVI NPs (1.6 nm) display excellent capability to decolorize model dyes such as methyl blue, acridine orange, and acid fuchsine with a decoloration percentage of more than 90%. Likewise, the same nanofibrous mats are found to be able to effectively degrade trichloroethylene, a model chlorinated hydrocarbon contaminant, with a degradation efficiency approaching 93%. The MWCNT-reinforced PAA/PVA nanofibrous mats may be used for generating other functionalized nanofiber-based complex materials with enhanced mechanical properties for applications in environmental remediation, catalysis, sensing, and biomedical sciences.

We report a novel electrospun composite nanofiber-based drug delivery system. In this study, halloysite nanotubes (HNTs) were first used to encapsulate a model drug, tetracycline hydrochloride. Then, the drug-loaded HNTs with an optimized encapsulation efficiency were mixed with poly(lactic-co-glycolic acid) (PLGA) polymer for subsequent electrospinning to form drug-loaded composite nanofibrous mats. The structure, morphology, and mechanical properties of the formed electrospun composite nanofibrous mats were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and tensile testing. In vitro drug release behavior was examined using UV-vis spectroscopy. The biocompatibility of HNT-containing PLGA fibers was evaluated through cell culture and MTT assay. We show that the incorporation of HNTs within the nanofibrous mats does not significantly change the morphology of the mats. In addition, our results indicate that this double-container drug delivery system (both PLGA polymer and HNTs are drug carriers) is beneficial to reduce the burst release of the drug and the introduction of HNTs can significantly improve the tensile strength of the polymer nanofibrous mats. Given the proved biocompatibility of the HNT-containing PLGA nanofibers via MTT assay of cell viability and SEM observation of cell morphology, the drug loaded electrospun composite nanofibrous mats developed in this study may find various applications in tissue engineering and pharmaceutical sciences.