Decades of research focused on size and shape control of iron oxide nanoparticles have led to methods of synthesis that afford excellent control over physical size and shape, but comparatively poor control over magnetic properties. Popular synthesis methods based on thermal decomposition of organometallic precursors in the absence of oxygen have yielded particles with mixed iron oxide phases, crystal defects and poorer than expected magnetic properties, including the existence of a thick “magnetically dead layer” experimentally evidenced by a magnetic diameter significantly smaller than the physical diameter. Here, we show how single crystalline iron oxide nanoparticles with few defects and similar physical and magetic diameter distributions can be obtained by introducing molecular oxygen as one of the reactive species in the thermal decomposition synthesis. This is achieved without the need for any post-synthesis oxidation or thermal annealing. These results address a significant challenge in the synthesis of nanoparticles with predictable magnetic properties and pave way to advances in applications of magnetic nanoparticles.

Polyvinylidene difluoride (PVDF) fibers were prepared by electrospinning from dimethyl formamide (DMF) solutions. The effects of the electrospinning processing conditions on the formation of the alpha and beta phases of PVDF were studied using infrared spectroscopy and differential scanning calorimetry. We have shown that beta-phase PVDF fibers can be electrospun directly from a dimethyl formamide (DMF) solution with a maximum fraction of beta phase, F(beta)max, of 0.75. The fraction of beta phase is found to be greater for smaller-diameter fibers and those spun at an increased voltage.

A controlled and observable drug delivery system that enables long-term local drug administration is reported. Biodegradable and biocompatible drug-loaded porous Si microparticles were prepared from silicon wafers, resulting in a porous 1-dimensional photonic crystal (rugate filter) approx. 12 micrometers thick and 35 micrometers across. An organic linker, 1-undecylenic acid, was attached to the Si-H terminated inner surface of the particles by hydrosilylation and the anthracycline drug daunorubicin was bound to the carboxy terminus of the linker. Degradation of the porous Si matrix in vitro was found to release the drug in a linear and sustained fashion for 30 d. The bioactivity of the released daunorubicin was verified on retinal pigment epithelial (RPE) cells. The degradation/drug delivery process was monitored in situ by digital imaging or spectroscopic measurement of the photonic resonance reflected from the nanostructured particles, and a simple linear correlation between observed wavelength and drug release was observed. Changes in the optical reflectance spectrum were sufficiently large to be visible as a distinctive red to green color change.

Polyvinylidene difluoride (PVDF) fibers with continuously dispersed ferrite (Ni 0.5Zn 0.5Fe 2O 4) nanoparticles were prepared by electrospinning from dimethyl formamide (DMF) solutions. The effects of the electrospinning processing conditions and nanoparticle loading on the formation of the alpha, beta, and gamma phases of PVDF were studied using infrared spectroscopy and differential scanning calorimetry. The amount of the ferroelectric beta and gamma phases present in the fibers was found to increase with increased nanoparticle loading. We have shown that the formation of PVDF phases with extended chain conformations can be enhanced by the addition of a well-dispersed nanoparticle phase. At increased nanoparticle loadings, the alpha phase is completely converted to the more extended beta and gamma phases.

Poly(ethylene glycol) based hydrogel microparticles were developed for pulmonary drug delivery. Hydrogels are particularly attractive for pulmonary delivery because they can be size engineered for delivery into the bronchi, yet also swell upon reaching their destination to avoid uptake and clearance by alveolar macrophages. To develop enzyme-responsive hydrogel microparticles for pulmonary delivery a new synthesis method based on a solution polymerization was developed. This method produces spherical poly(ethylene glycol) (PEG) microparticles from high molecular weight poly(ethylene glycol) diacrylate (PEGDA)-based precursors that incorporate peptides in the polymer chain. Specifically, we have synthesized hydrogel microparticles that degrade in response to matrix metalloproteinases that are overexpressed in pulmonary diseases. Small hydrogel microparticles with sizes suitable for lung delivery by inhalation were obtained from solid precursors when PEGDA was dissolved in water at a high concentration. The average diameter of the particles was between 2.8 and 4 μm, depending on the molecular weight of the precursor polymer used and its concentration in water. The relation between the physical properties of the particles and their enzymatic degradation is also reported, where an increased mesh size corresponds to increased degradation.

Nanostructured mesoporous silica (SiO 2 ) films are used to load and release the monoclonal antibody bevacizumab (Avastin) in vitro. A biocompatible and biodegradable form of mesoporous SiO 2 is prepared by electrochemical etching of single crystalline Si, followed by thermal oxidation in air at 800 °C. Porous SiO 2 exhibits a negative surface charge at physiological pH (7.4), allowing it to spontaneously adsorb the positively charged antibody from an aqueous phosphate buffered saline solution. This electrostatic adsorption allows bevacizumab to be concentrated by >100× (300 mg bevacziumab per gram of porous SiO 2 when loaded from a 1 mg mL −1 solution of bevacziumab). Drug loading is monitored by optical interferometric measurements of the thin porous film. A two-component Bruggeman effective medium model is employed to calculate percent porosity and film thickness, and is further used to determine the extent of drug loading into the porous SiO 2 film. In vitro drug release profiles are characterized by an enzyme-linked immunosorbent assay (ELISA), which confirms that the antibody is released in its active, VEGFbinding form. The nanostructured delivery system described here provides a sustained release of the monoclonal antibody where approximately 98% of drug is released over a period of one month.

Thermal oxidation of porous Si microparticles provides an inert carrier for the long-term release of the anthracycline drug daunorubicin. Without prior oxidation, porous Si undergoes an undesirable side reaction with this redox active drug.

A composite material consisting of Fe3O4 nanoparticles embedded in a 200 nm‐diameter porous Si (pSi) nanoparticle “superstructure” is prepared as a potential magnetic resonance imaging contrast agent. Dipolar magnetic coupling between Fe3O4 nanoparticles is enhanced due to their proximity in the pSi host matrix, resulting in an increase in the saturation magnetization and coercivity of the composite.