Developing facile synthetic routes to multifunctional nanoparticles combining the magnetic properties of iron oxides with the optical and catalytic utility of noble metal particles remains an important goal in realizing the potential of hybrid nanomaterials. To this end, we have developed a single route to noble metal-decorated magnetic nanoparticles (Fe3O4@SiO2-M; M = Au, Pd, Ag, and PtAg) and characterized them by HRTEM and STEM/EDX imaging to reveal their nanometer size (16 nm Fe3O4 and 1-5 nm M seeds) and uniformity. This represents one of the few examples of genuine multifunctional particles on the nanoscale. We show that these hybrid structures have excellent catalytic activity for the reduction of 4-nitrophenol (knorm = 2 × 10(7) s(-1) mol(Pd)(-1); 5 × 10(6) s(-1) mol(Au)(-1); 5 × 10(5) s(-1) mol(PtAg)(-1); 7 × 10(5) s(-1) mol(Ag)(-1)). These rates are the highest reported for nano-sized comparables, and are competitive with mesoparticles of similar composition. Due to their magnetic response, the particles are also suitable for magnetic recovery and maintain >99% conversion for at least four cycles. Using this synthetic route, Fe3O4@SiO2-M particles show great promise for further development as a precursor to complicated anisotropic materials or for applications ranging from nanocatalysis to biomedical sensing.

Gold nanoparticle theranostic agents have dramatic potential in the fight against disease, particularly cancer, as multifunctional platforms combining biocompatibility, unique optical properties for detection/activation, and heat generation. In this vein, a new thiol-functionalized enediyne surfactant ligand was synthesized and coordinated to gold nanoparticles, as confirmed by the red-shift in the optical spectrum from λ = 520 to 529 nm upon ligand exchange. Raman spectra of the nanoparticle conjugate material show characteristic vibrations at 2192 (alkyne), 1582 (alkene), and 670 cm −1 (C−S). The photoreactivity of the material is explored under two sets of photolysis conditions: solution, λ exc = 514 nm, RT, t = 8 h; solid aggregate, λ exc = 785 nm, T = −190 °C, t = 4 h. Under these conditions, exciting into the surface plasmon of the Au nanoparticle substrate transfers heat to the organic ligand layer, initiating enediyne cyclization and generating surface radicals that lead to subsequent polymerization. New vibrational signatures arise in the alkyne (2170−1900 cm −1 ) and aromatic (1520−1200 cm −1 ) spectral regions, indicating the formation of highly conjugated species in the initial stages of the photoreaction. Prolonged irradiation results in the observation of a dense polymer coating in the TEM images, complete loss of observable molecular vibrations in the Raman spectra as a result of strong fluorescence, and a red-shift and broadening of the surface plasmon band in the electronic spectrum. Translation of this approach to nanorods and other architectures is also possible with carbon coatings clearly visible by TEM. The reported nanomaterial design represents a new approach to developing reactive biomedical agents for phototherapy applications, as well as a novel method toward carbonaceous coatings of nanoarchitectures.

Thrombosis is a hallmark of several chronic diseases leading to potentially fatal heart attacks and strokes. Frontline interventions include intravenous delivery of potent, enzymatic fibrinolytics that possess a high risk for inducing systemic bleeding. As a conceptual countermeasure, we have developed a water-soluble PEGylated gold nanoparticle appended with the enediyne diamine (Z)-octa-4-en-2,6-diyne-1,8-diamine that is capable of photothermally generating 1,4-diradical species under visible excitation (λ = 514 nm, 100 mW, 2−6 h). In the absence of biopolymer substrate, photothermal excitation of these particles leads to self-quenching polymer coating formation in water. When these radical-generating nanoparticles are intrinsically applied toward the blood clot structural protein assembly fibrin, as well as its nonpolymerized precursor protein fibrinogen, scanning electron microscopy images reveal significantly modified fibrin clot morphology, as evidenced by larger void spaces and collapsed fiber regions. Quantitatively, laser confocal microscopy images of Alexa Fluor 488-labeled fibrin clots extrinsically treated with nanoparticles at the clot/solution interface show that photothermal radical formation by these particles leads to marked increase in the number of larger pore sizes (>2.0 μm) within the fibrin matrix, which derive from a corresponding decrease in the histogram of smaller pore sizes (1.5−2.0 μm). These larger pore sizes ultimately result in total perfusion of solution through the entire clot volume. The chemical manifestation of this is that radical-induced modifications occur mainly at the protein level but lead to morphological changes at the micron scale. Overall, this technology could have significant impact for disease states such as deep vein thrombosis via a localized, catheter-delivered approach.

Halting cancer progression by altering the tumor microenvironment is an exciting new frontier in oncology. One target for new therapies is the structural support provided by the extracellular matrix, which for cancer cells is often abnormal and undergoes drastic modification during angiogenesis, tumor proliferation, and metastasis. We have developed a new magnetic nanoparticle-based agent, Fe 3 O 4 −PEG−EDDA (EDDA: (Z)-octa-4-en-2,6-diyne-1,8-diamine), that is capable of generating radicals via Bergman cyclization of the pendant enediyne during mild hyperthermia treatment using an alternating magnetic field. We observe formation of a cyclized aromatic product in the Raman spectra of the thermally excited material and can detect polymeric product after periods of induction. When mixed with the basement membrane extract Matrigel, the nanoparticles do not interfere with normal biopolymer network formation. Applying the same hyperthermia conditions as in solution samples, Fe 3 O 4 −PEG−EDDA causes structural collapse of the matrix, visible by electron microscopy, in contrast to the nonradical-forming thermal control Fe 3 O 4 −PEG−BD (BD: o-xylylenediamine). Localized damage to the extracellular matrix by nanoparticle-induced molecular transformations represent a conceptual new tool in tumor microenvironment modification.