Hongchen Gu

Fluorescent, Superparamagnetic Nanospheres for Drug Storage, Targeting, and Imaging: A Multifunctional Nanocarrier System for Cancer Diagnosis and Treatment

For early cancer diagnosis and treatment, a nanocarrier system is designed and developed with key components uniquely structured at nanoscale according to medical requirements. For imaging, quantum dots with emissions in the near-infrared range (∼800 nm) are conjugated onto the surface of a nanocomposite consisting of a spherical polystyrene matrix (∼150 nm) and the internally embedded, high fraction of superparamagnetic Fe(3)O(4) nanoparticles (∼10 nm). For drug storage, the chemotherapeutic agent paclitaxel (PTX) is loaded onto the surfaces of these composite multifunctional nanocarriers by using a layer of biodegradable poly(lactic-co-glycolic acid) (PLGA). A cell-based cytotoxicity assay is employed to verify successful loading of pharmacologically active drug. Cell viability of human, metastatic PC3mm2 prostate cancer cells is assessed in the presence and absence of various multifunctional nanocarrier populations using the MTT assay. PTX-loaded composite nanocarriers are synthesized by conjugating anti-prostate specific membrane antigen (anti-PSMA) for targeting. Specific detection studies of anti-PSMA-conjugated nanocarrier binding activity in LNCaP prostate cancer cells are carried out. LNCaP cells are targeted successfully in vitro by the conjugation of anti-PSMA on the nanocarrier surfaces. To further explore targeting, the nanocarriers conjugated with anti-PSMA are intravenously injected into tumor-bearing nude mice. Substantial differences in fluorescent signals are observed ex vivo between tumor regions treated with the targeted nanocarrier system and the nontargeted nanocarrier system, indicating considerable targeting effects due to anti-PSMA functionalization of the nanocarriers.

Core–Shell‐Type Magnetic Mesoporous Silica Nanocomposites for Bioimaging and Therapeutic Agent Delivery

Advances in nanotechnology and nanomedicine offer great opportunities for the development of nanoscaled theranostic platforms. Among various multifunctional nanocarriers, magnetic mesoporous silica nanocomposites (M-MSNs) attract prominent research interest for their outstanding properties and potential biomedical applications. This Research News article highlights recent progress in the design of core-shell-type M-MSNs for both diagnostic and therapeutic applications. First, an overview of synthetic strategies for three representative core-shell-type M-MSNs with different morphologies and structures is presented. Then, the diagnostic functions of M-MSNs is illustrated for magnetic resonance imaging (MRI) applications. Next, magnetic targeted delivery and stimuli-responsive release of drugs, and effective package of DNA/siRNA inside mesopores using M-MSNs as therapeutic agent carriers are discussed. The article concludes with some important challenges that need to be overcome for further practical applications of M-MSNs in nanomedicine.

A facile, water-based synthesis of highly branched nanostructures of silver.

We report a facile and environmentally friendly method of preparing highly branched silver nanostructures. By reducing AgNO 3 with l-ascorbic acid in an aqueous solution, silver particles having a coral-like morphology were formed in a few minutes. A mechanistic study of the growth process revealed that the silver branches grew from a bulbous seed formed through aggregation, and that by changing the concentrations of the reagents, the degree of particle branching could be altered. With their potentially high surface areas, these branched structures could find use as catalysts or as substrates for surface-enhanced Raman scattering applications.

Synthesis of Asymmetric Inorganic/Polymer Nanocomposite Particles via Localized Substrate Surface Modification and Miniemulsion Polymerization

Asymmetric nanocomposite particle pairs of polystyrene and silica were prepared via one-step miniemulsion polymerization for the first time. The transmission electron microscopy images showed that these nanocomposite particle pairs were monodisperse and highly asymmetric in morphology. The key to obtaining the asymmetric nanocomposite particle pairs was the combination of miniemulsion polymerization and the local surface modification of silica substrates. Because of localized surface modification on the silica surface, the nucleation and formation of the polymer nodule in miniemulsion polymerization took place only in the modified area on the silica surface, thus ensuring the asymmetric morphology. The asymmetrical materials obtained by the facile and effective method will have significant potential applications in some areas including biomedical fields.

Size determination of superparamagnetic nanoparticles from magnetization curve

The size distribution of superparamagnetic iron oxide nanoparticles in two powder samples is determined from the measured magnetization curve fitted by a core-shell model and a uniform model, both based on the Langevin function with a log-normal particle volume distribution. Different average sizes are evaluated from the fitting parameters and compared to those determined by other techniques. Conceptual discussions are presented on different models and approaches, from which the core-shell model fitting is recommended for the magnetic size determination of superparamagnetic nanoparticles.

Asymmetric Composite Nanoparticles with Anisotropic Surface Functionalities

Asymmetric inorganic/organic composite nanoparticles with anisotropic surface functionalities represent a new approach for creating smart materials, requiring the selective introduction of chemical groups to dual components of composite, respectively. Here, we report the synthesis of snowman-like asymmetric silica/polystyrene heterostructure with anisotropic functionalities via a chemical method, creating nanostructure possibly offering two-sided biologic accessibility through the chemical groups. Carboxyl group was introduced to polystyrene component of the snowman-like composites by miniemulsion polymerization of monomer on local surface of silica particles. Moreover, amino group was then grafted to remained silica surface through facile surface modification of the composite nanoparticles. The asymmetric shape of these composites was confirmed by TEM characterization. Moreover, characteristics of anisotropic surface functionalities were indicated by Zeta potential measurement and confocal laser microscopy after being labeled with fluorescent dyes. This structure could find potential use as carriers for biological applications.

Size-independent residual magnetic moments of colloidal Fe3O4-polystyrene nanospheres detected by ac susceptibility measurements

Complex ac susceptibility of magnetic colloids of nanospheres, each consisting of Fe3O4 nanoparticles densely and uniformly embedded in a polystyrene matrix, is measured as a function of frequency. A data analysis based on a model and the directly measured size distribution shows that each spherical aggregate of nanoparticles carries a small residual magnetic moment, whose average is basically independent of the sphere size. The mentioned model assumes that magnetic spheres undergo rotational Brownian motions obeying Debye’s theory and nanoparticles undergo Neel magnetization rotations. A discussion is made on the superparamagnetism and the nanoparticle interactions in the present case, in order to justify the applicability of the model and to look for the mechanism of the detected sphere-size independent magnetic moment.

Waiting time dependence of T2 of protons in water suspensions of iron-oxide nanoparticles: Measurements and simulations

The transverse relaxation time T2 of protons in water suspensions of iron-oxide particles increases with the waiting time tw after the sample is inserted in the gap of the spectrometer magnet. Such a T2 increase becomes significant if the particles are aggregated into large clusters, for which field-induced formation of cluster-chains will occur and T2 should increase with increasing the length of chains. T2 increases with tw even for small particles, for which no chain formation may be induced, and for large clusters when tw is too small to form long enough chains. The T2 increase is accompanied by a significant echo-time dependence. All this is experimentally and theoretically studied.The transverse relaxation time T2 of protons in water suspensions of iron-oxide particles increases with the waiting time tw after the sample is inserted in the gap of the spectrometer magnet. Such a T2 increase becomes significant if the particles are aggregated into large clusters, for which field-induced formation of cluster-chains will occur and T2 should increase with increasing the length of chains. T2 increases with tw even for small particles, for which no chain formation may be induced, and for large clusters when tw is too small to form long enough chains. The T2 increase is accompanied by a significant echo-time dependence. All this is experimentally and theoretically studied.

Fluorescent super paramagnetic nanoparticles for medical diagnosis and treatment

There is an increasing need for early detection and treatment of cancer before a tumor mass becomes evident as anatomical anomaly. Highly fluorescent nanoparticles suitable for in vivo detection of tumor cells represent a promising strategy to surpass current limitations in cancer diagnostic and tumor therapy. However, an optimum nanostructure that simultaneously offers multiple functionalities, including intensive fluorescence and therapeutic efficacy, has yet to be developed. In this study, we report the design of a new nanostructure that ideally satisfies important requirements. Quantum dots (QDs) were immobilized on the surfaces of Fe3O4-composite nanospheres (MNS). The QDs on these MNS exhibited intense visible emission by fluorescent spectroscopy and successfully facilitated, for the first time, in vivo soft tissue imaging in live mice.