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Now showing items 1 - 16 of 21

  • Nano-tribological properties and mechanisms of the liquid crystal as an additive

    Mingwu Shen   Jianbin Luo   Shizhu Wen   Junbin Yao  

    Under conditions of low speed, small viscosity and molecularly smooth tribo-surfaces, the behavior of lubricant film in the nanoscale is different from that in elastohydrodynamic lubrication (EHL) and boundary lubrication (BL). Due to the size effect, the long-range ordered structure of liquid crystal (LC) has great effects on the tribological properties and film-forming mechanism of thin film in the nanoscale. The technique of relative optical interference intensity (ROII) was used to investigate nanotribological properties when cholesteryl LCs are added to hexadecane. The results indicate that the practical film thickness of hexadecane with liquid crystal is 3-5 times as large as that expected from EHL theory in the low speed region. The film thickness increases with the enhancement in polarity and concentration of LC in hexadecane, and external DC voltage. The effective viscosity of lubricant is related to the film thickness and the voltage and it varies from bulk viscosity by up to several times or tens of times bulk viscosity with reducing film thickness, and slowly rises with increasing external DC voltage and then tends to a constant. The higher ordered degree of molecules close to solid surfaces gives rise to a thicker film
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  • Magnetic resonance imaging of glioma with novel APTS-coated superparamagnetic iron oxide nanoparticles

    Kangan Li   Mingwu Shen   Linfeng Zheng   Jinglong Zhao…  

    We report in vitro and in vivo magnetic resonance (MR) imaging of C6 glioma cells with a novel acetylated 3-aminopropyltrimethoxysilane (APTS)-coated iron oxide nanoparticles (Fe3O4 NPs). In the present study, APTS-coated Fe3O4 NPs were formed via a one-step hydrothermal approach and then chemically modified with acetic anhydride to generate surface charge-neutralized NPs. Prussian blue staining and transmission electron microscopy (TEM) data showed that acetylated APTS-coated Fe3O4 NPs can be taken up by cells. Combined morphological observation, cell viability, and flow cytometric analysis of the cell cycle indicated that the acetylated APTS-coated Fe3O4 NPs did not significantly affect cell morphology, viability, or cell cycle, indicating their good biocompatibility. Finally, the acetylated APTS-coated Fe3O4 nanoparticles were used in magnetic resonance imaging of C6 glioma. Our results showed that the developed acetylated APTS-coated Fe3O4 NPs can be used as an effective labeling agent to detect C6 glioma cells in vitro and in vivo for MR imaging. The results from the present study indicate that the developed acetylated APTS-coated Fe3O4 NPs have a potential application in MR imaging.
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  • Neighborhood health-promoting resources and obesity risk (the multi-ethnic study of atherosclerosis)

    Amy H. Auchincloss   Mahasin S. Mujahid   Mingwu Shen   Erin D. Michos   Melicia C. Whitt-Glover and Ana V. Diez Roux  

    While behavioral change is necessary to reverse the obesity epidemic, it can be difficult to achieve and sustain in unsupportive residential environments. This study hypothesized that environmental resources supporting walking and a healthy diet are associated with reduced obesity incidence.
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  • Effect of the surface functional groups of dendrimer-entrapped gold nanoparticles on the improvement of PCR

    Xueyan Cao   Mingwu Shen   Xiaodong Zhang   Jun Hu   Jianhua Wang and Xiangyang Shi  

    PCR has been identified as one of the most important tools in molecular biology and clinical medicine. Improvement of the specificity and efficiency of PCR is often required, and it still remains a great challenge. Here, we introduce the use of dendrimer-entrapped gold nanoparticles (Au DENPs) with different terminal groups prepared using poly(amidoamine) (PAMAM) dendrimers of generation 5 (G5) as a novel class of enhancers to improve the specificity and efficiency of PCR amplification. We show that the optimum concentrations of all the tested Au DENPs are lower than those of the corresponding PAMAM dendrimers without gold nanoparticles (AuNPs). For amine-terminated [(Au0)51.2-G5.NH2] DENPs, the optimum required concentration is slightly lower than that of G5.NH2 dendrimers, whereas for glycidol-modified [(Au0)51.2-G5.NGlyOH] and acetylated [(Au0)51.2-G5.NHAc] DENPs, the optimum required concentrations are one and three magnitude lower than the corresponding dendrimers, respectively. Our results suggest that the entrapment of AuNPs within the dendrimer interior helps to reserve the 3D spherical morphology of dendrimers, allowing for enhanced interaction with the PCR components. Simultaneously, because of the existence of thermal conductive AuNPs, the enhanced local heat transfer rate may afford decreased chances of mispairing between primers and templates, which is beneficial for enhancing the PCR specificity and efficiency. Therefore, the use of Au DENPs as a novel class of PCR enhancers may enable both improved interaction with the PCR components and the thermal conductivity, which allow them to be used for enhancing different error-prone PCR systems.
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  • Facile one-pot preparation, surface functionalization, and toxicity assay of APTS-coated iron oxide nanoparticles

    Mingwu Shen   Hongdong Cai   Xifu Wang   Xueyan Cao   Kangan Li   Su He Wang   Rui Guo   Linfeng Zheng   Guixiang Zhang   Xiangyang Shi  

    We report a facile approach to synthesizing 3-aminopropyltrimethoxysilane (APTS)-coated magnetic iron oxide (Fe3O4@APTS) nanoparticles (NPs) with tunable surface functional groups for potential biomedical applications. The Fe3O4 NPs with a mean diameter of 6.5聽nm were synthesized by a hydrothermal route in the presence of APTS. The formed amine-surfaced Fe3O4@APTS NPs were further chemically modified with acetic anhydride and succinic anhydride to generate neutral (Fe3O4@APTS鈰匒c) and negatively charged (Fe3O4@APTS鈰匰AH) NPs. These differently functionalized NPs were extensively characterized by x-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetry analysis, zeta potential measurements, and T2 relaxometry. The cytotoxicity of the particles was evaluated by in vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric viability assay of cells along with microscopic observation of cell morphology. The hemocompatibility of the particles was assessed by in vitro hemolysis assay. We show that the hydrothermal approach enables an efficient modification of APTS onto the Fe3O4 NP surfaces and the formed NPs with different surface charge polarities are water-dispersible and colloidally stable. The acetylated Fe3O4@APTS鈰匒c NPs displayed good biocompatibility and hemocompatibility in the concentration range of 0鈥?00聽碌g聽ml鈭?, while the pristine Fe3O4@APTS and Fe3O4@APTS鈰匰AH particles started to display slight cytotoxicity at a concentration of 10聽碌g聽ml鈭?. The findings from this study suggest that the Fe3O4@APTS NPs synthesized by the one-pot hydrothermal route can be surface modified for various potential biomedical applications.
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  • Effects of surface physicochemical properties on the tribological properties of liquid paraffin film in the nanoscale

    Mingwu Shen   Jianbin Luo   Shizhu Wen  

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  • Targeted tumor dual mode CT/MR imaging using multifunctional polyethylenimine-entrapped gold nanoparticles loaded with gadolinium

    Benqing Zhou   Zuogang Xiong   Peng Wang   Chen Peng   Mingwu Shen   Serge Mignani   Jean-Pierre Majoral   Xiangyang Shi  

    We report the construction and characterization of polyethylenimine (PEI)-entrapped gold nanoparticles (AuNPs) chelated with gadolinium (Gd) ions for targeted dual mode tumor CT/MR imaging in vivo. In this work, polyethylene glycol (PEG) monomethyl ether-modified PEI was sequentially modified with Gd chelator and folic acid (FA)-linked PEG (FA-PEG) was used as a template to synthesize AuNPs, followed by Gd(III) chelation and acetylation of the remaining PEI surface amines. The formed FA-targeted PEI-entrapped AuNPs loaded with Gd (FA-Gd-Au PENPs) were well characterized in terms of structure, composition, morphology, and size distribution. We show that the FA-Gd-Au PENPs with an Au core size of 3.0 nm are water dispersible, colloidally stable, and noncytotoxic in a given concentration range. Thanks to the coexistence of Au and Gd elements within one nanoparticulate system, the FA-Gd-Au PENPs display a better X-ray attenuation property than clinical iodinated contrast agent (e.g. Omnipaque) and reasonable r1 relaxivity (1.1 mM−1s−1). These properties allow the FA-targeted particles to be used as an efficient nanoprobe for dual mode CT/MR imaging of tumors with excellent FA-mediated targeting specificity. With the demonstrated organ biocompatibility, the designed FA-Gd-Au PENPs may hold a great promise to be used as a nanoprobe for CT/MR dual mode imaging of different FA receptor-overexpressing tumors.
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  • Electrospun laponite-doped poly(lactic-co-glycolic acid) nanofibers for osteogenic differentiation of human mesenchymal stem cells

    Shige Wang   Castro, R.   Xiao An   Chenlei Song   Yu Luo   Mingwu Shen   Tomas, H.   Meifang Zhu   Xiangyang Shi  

    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.
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  • Magnetic resonance imaging of glioma with novel APTS-coated superparamagnetic iron oxide nanoparticles

    Kangan Li   Mingwu Shen   Lin-feng Zheng   Jinglong Zhao   Qimeng Quan   Xiangyang Shi   Gui-xiang Zhang  

    We report in vitro and in vivo magnetic resonance (MR) imaging of C6 glioma cells with a novel acetylated 3-aminopropyltrimethoxysilane (APTS)-coated iron oxide nanoparticles (Fe3O4 NPs). In the present study; APTS-coated Fe3O4 NPs were formed via a one-step hydrothermal approach and then chemically modified with acetic anhydride to generate surface charge-neutralized NPs. Prussian blue staining and transmission electron microscopy (TEM) data showed that acetylated APTS-coated Fe3O4 NPs can be taken up by cells. Combined morphological observation; cell viability; and flow cytometric analysis of the cell cycle indicated that the acetylated APTS-coated Fe3O4 NPs did not significantly affect cell morphology; viability; or cell cycle; indicating their good biocompatibility. Finally; the acetylated APTS-coated Fe3O4 nanoparticles were used in magnetic resonance imaging of C6 glioma. Our results showed that the developed acetylated APTS-coated Fe3O4 NPs can be used as an effective labeling agent to detect C6 glioma cells in vitro and in vivo for MR imaging. The results from the present study indicate that the developed acetylated APTS-coated Fe3O4 NPs have a potential application in MR imaging.
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  • An RGD-modified hollow silica@Au core/shell nanoplatform for tumor combination therapy

    Xin Li   Lingxi Xing   Yong Hu   Zhijuan Xiong   Ruizhi Wang   Xiaoying Xu   Lianfang Du   Mingwu Shen   Xiangyang Shi  

    Graphical abstract Abstract The combination of chemotherapy and photothermal therapy (PTT) in multifunctional nanoplatforms to improve cancer therapeutic efficacy is of great significance while it still remains to be a challenging task. Herein, we report Au nanostar (NS)-coated hollow mesoporous silica nanocapsules (HMSs) with surface modified by arginine-glycine-aspartic acid (RGD) peptide as a drug delivery system to encapsulate doxorubicin (DOX) for targeted chemotherapy and PTT of tumors. Au NSs-coated HMSs core/shell nanocapsules (HMSs@Au NSs) synthesized previously were conjugated with RGD peptide via a spacer of polyethylene glycol (PEG). We show that the prepared HMSs@Au-PEG-RGD NSs are non-cytotxic in the given concentration range, and have a DOX encapsulation efficiency of 98.6 ± 0.7%. The designed HMSs@Au-PEG-RGD NSs/DOX system can release DOX in a pH/NIR laser dual-responsive manner. Importantly, the formed HMSs@Au-PEG-RGD NSs/DOX nanoplatform can specifically target cancer cells overexpressing α v β 3 intergrin and exert combination chemotherapy and PTT efficacy to the cells in vitro and a xenografted tumor model in vivo . Our results suggest that the designed HMSs@Au-PEG-RGD NSs/DOX nanoplatform may be used for combination chemotherapy and PTT of tumors. Statement of Significance We demonstrate a convenient approach to preparing a novel RGD-targeted drug delivery system of HMSs@Au-PEG-RGD NSs/DOX that possesses pH/NIR laser dual-responsive drug delivery performance for combinational chemotherapy and PTT of tumors. The developed Au NS-coated HMS capsules have both merits of HMS capsules that can be used for high payload drug loading and Au NSs that have NIR laser-induced photothermal conversion efficiency (70.8%) and can be used for PTT of tumors.
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  • Antitumor efficacy of doxorubicin-loaded electrospun nano-hydroxyapatite-poly(lactic-co-glycolic acid) composite nanofibers

    Fuyin Zheng   Shige Wang   Mingwu Shen   Meifang Zhu   Xiangyang Shi  

    Electrospun composite nanofibrous scaffolds have attracted much interest for use as drug delivery vehicles in recent years. Herein, we attempted to first encapsulate the anticancer drug doxorubicin (DOX) using inorganic rod-like nano-hydroxyapatite (n-HA) as a carrier. Then, the DOX-loaded n-HA particles were mixed with poly(lactic-co-glycolic acid) (PLGA) solution to fabricate electrospun hybrid nanofibers. The formation of drug-n-HA complexes and the drug-loaded composite nanofibers were characterized using different techniques. In vitro DOX release behavior was examined using UV-vis spectroscopy under both neutral and acidic conditions. The anticancer activity of the drug-loaded composite nanofibers was evaluated via the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) viability assay and phase contrast microscopic morphology observation of a model KB cancer cell line (a human epithelial carcinoma cell line). We show that DOX can be successfully loaded onto the surface of the n-HA and the formed composite fibers have a uniform and continuous fibrous morphology. Importantly, the loaded DOX shows a sustained release profile, and the released DOX from the nanofibers displays noncompromised antitumor activity towards the growth inhibition of KB cells. With the significantly reduced burst release profile and the improved mechanical durability of the composite nanofiber system compared with n-HA-free PLGA nanofibers, the designed organic-inorganic hybrid nanofibers could be used as a versatile drug delivery system for encapsulation and sustained release of different drugs with prolonged therapeutic efficacy for different biomedical applications.
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  • Loading of Au/Ag bimetallic nanoparticles within electrospun PVA/PEI nanofibers for catalytic applications

    Dengmai Hu   Yunchao Xiao   Hui Liu   Hong Wang   Jingchao Li   Benqing Zhou   Pengchao Liu   Mingwu Shen   Xiangyang Shi  

    Graphical abstract Abstract We present a convenient method to immobilize Au/Ag nanoparticles (NPs) within electrospun polyvinyl alcohol (PVA)/polyethylenimine (PEI) nanofibers by in-situ reduction for catalytic applications. Water-stable electrospun PVA/PEI nanofibers were initially fabricated by crosslinking with glutaraldehyde (GA) vapor. Then, the nanofibers were used as a nanoreactor to bind Au salt via electrostatic interaction with the free PEI amines, followed by NaBH 4 reduction to form Au NPs. The formed Au NP-containing nanofibers were then used to bind Ag + ions via chelation with the free PEI amines, followed by reduction with ascorbic acid to form the Au/Ag NP-loaded PVA/PEI nanofibers. The small size (4.9 ± 1.8 nm) and narrow size distribution of the immobilized Au/Ag NPs reveal that the nanofibrous structure is able to efficiently prevent the aggregation of the NPs. We then evaluated the catalytic activity and reusability of Au/Ag NP-immobilized PVA/PEI nanofiers by catalytic transformation of 4-nitrophenol to 4-aminophenol in aqueous solution. The material exhibited excellent catalytic efficiency and reusability. The developed approach could be applied to create other bimetallic NP-incorporated nanofibers for catalysis, tissue engineering, and environmental remediation applications.
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  • Design of electrospun nanofibrous mats for osteogenic differentiation of mesenchymal stem cells

    Shige Wang   Fei Hu   Jingchao Li   Shuping Zhang   Mingwu Shen   Mingxian Huang   Xiangyang Shi  

    Abstract The clinical translation potential of mesenchymal stem cells (MSCs) in regenerative medicine has been greatly exploited. With the merits of high surface area to volume ratio, facile control of components, well retained topography, and the capacity to mimic the native extracellular matrix (ECM), nanofibers have received a great deal of attention as bone tissue engineering scaffolds. Electrospinning has been considered as an efficient approach for scale-up fabrication of nanofibrous materials. Electrospun nanofibers are capable of stimulating cell–matrix interaction to form a cell niche, directing cellular behavior, and promoting the MSCs adhesion and proliferation. In this review, we give a comprehensive literature survey on the mechanisms of electrospun nanofibers in supporting the MSCs differentiation. Specifically, the influences of biological and physical osteogenic inductive cues on the MSCs osteogenic differentiation are reviewed. Along with the significant advances in the field, current research challenges and future perspectives are also discussed. Graphical Abstract This review gives a comprehensive literature survey on the mechanisms of electrospun nanofibers in supporting the MSCs differentiation. The influences of chemical or physical osteogenic inductive cues on the MSCs osteogenic differentiation are reviewed. Along with the significant advances in the field, current research challenges and future perspectives are also discussed. Image 1 Highlights • The application potentials of various kinds of electrospun nanofibers used for MSCs-based bone tissue engineering were summarized. • Inorganic inductive materials with osteoinductive and osteoconductive properties could alter the mechanical property of electrospun nanofibers, which could be then converted to biochemical signals that are able to active the osteogenic differentiation. • Organic cues could be encapsulated by electrospun nanofibers and their release from the nanofiber matrix could be controlled to a sustained release manner so as to realize a better osteogenic differentiation outcome. • Topological cues included fiber diameter, pores, orientation, patterns and other stimuli such as the mechanical property and surface conductivity could direct the cell growth along the aligned nanofiber orientation or micropattern direction to present different cell shapes, which were conductive for specific differentiation of MSCs.
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  • Multifunctional dendrimer-based nanoparticles for in vivo MR/CT dual-modal molecular imaging of breast cancer

    Kangan Li   Shihui Wen   Andrew C. Larson   Mingwu Shen   Zhuoli Zhang   Qian Chen   Xiangyang Shi   Gui-xiang Zhang  

    Development of dual-mode or multi-mode imaging contrast agents is important for accurate and self-confirmatory diagnosis of cancer. We report a new multifunctional, dendrimer-based gold nanoparticle (AuNP) as a dual-modality contrast agent for magnetic resonance (MR)/computed tomography (CT) imaging of breast cancer cells in vitro and in vivo. In this study, amine-terminated generation 5 poly(amidoamine) dendrimers modified with gadolinium chelate (DOTA-NHS) and polyethylene glycol monomethyl ether were used as templates to synthesize AuNPs, followed by Gd(III) chelation and acetylation of the remaining dendrimer terminal amine groups; multifunctional dendrimer-entrapped AuNPs (Gd-Au DENPs) were formed. The formed Gd-Au DENPs were used for both in vitro and in vivo MR/CT imaging of human MCF-7 cancer cells. Both MR and CT images demonstrate that MCF-7 cells and the xenograft tumor model can be effectively imaged. The Gd-Au DENPs uptake, mainly in the cell cytoplasm, was confirmed by transmission electron microscopy. The cell cytotoxicity assay, cell morphology observation, and flow cytometry show that the developed Gd-Au DENPs have good biocompatibility in the given concentration range. Our results clearly suggest that the synthetic Gd-Au DENPs are amenable for dual-modality MR/CT imaging of breast cancer cells.
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  • Relation between neighborhood environments and obesity in the Multi-Ethnic Study of Atherosclerosis.

    Mahasin S . Mujahid   Ana Victoria Diez Roux   Mingwu Shen   Deepthiman K. Gowda   Brisa N Sánchez   Steven Shea   David R. Jacobs   Sharon A. Jackson  

    This study investigated associations between neighborhood physical and social environments and body mass index in 2,865 participants of the Multi-Ethnic Study of Atherosclerosis (MESA) aged 45-84 years and residing in Maryland, New York, and North Carolina. Neighborhood (census tract) environments were measured in non-MESA participants residing in MESA neighborhoods (2000-2002). The neighborhood physical environment score combined measures of a better walking environment and greater availability of healthy foods. The neighborhood social environment score combined measures of greater aesthetic quality, safety, and social cohesion and less violent crime. Marginal maximum likelihood was used to estimate associations between neighborhood environments and body mass index (kg/m(2)) before and after adjustment for individual-level covariates. MESA residents of neighborhoods with better physical environments had lower body mass index (mean difference per standard deviation higher neighborhood measure = -2.38 (95% confidence interval (CI): -3.38, -1.38) kg/m(2) for women and -1.20 (95% CI: -1.84, -0.57) kg/m(2) for men), independent of age, race/ethnicity, education, and income. Attenuation of these associations after adjustment for diet and physical activity suggests a mediating role of these behaviors. In men, the mean body mass index was higher in areas with better social environments (mean difference = 0.52 (95% CI: 0.07, 0.97) kg/m(2)). Improvement in the neighborhood physical environment should be considered for its contribution to reducing obesity.
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  • Dendrimer-based magnetic iron oxide nanoparticles: their synthesis and biomedical applications

    Wenjie Sun   Serge Mignani   Mingwu Shen   Xiangyang Shi  

    Highlights • Dendrimers with unique properties can used to form multifunctional MIO NPs. • Various synthetic strategies used to form dendrimer-based MIO NPs are summarized. • Dendrimer-based MIO NPs can be used for different biomedical applications. • Outlooks of dendrimer-based MIO NPs for biomedical applications are discussed. Magnetic iron oxide nanoparticles (MIO NPs) bearing different appropriate surface modifications can be prepared using diverse physical and chemical methods. As an ideal macromolecule, dendrimers have attracted considerable attention because of their unique properties, including their three 3D architecture, monodispersity, highly branched macromolecular characteristics, and tunable terminal functionalities. These properties make dendrimers a powerful nanoplatform for the creation of functional organic and/or inorganic hybrid NPs, in particular dendrimer-based MIO NPs. Here, we report on recent advances in the preparation of dendrimer-based MIO NPs for different biomedical applications, such as magnetic resonance (MR) imaging, drug and gene delivery, and protein immobilization. Teaser The development and synthesis of dendrimer-based magnetic iron oxide nanoparticles formed through different synthetic strategies for various biomedical applications are discussed.
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