Folic acid conjugated Fe3O4 magnetic nanoparticles for targeted delivery of doxorubicin.

The interfacial engineering of magnetic nanoparticles (MNPs) with specific functional groups or targeting ligands is important for their in vivo applications. We report here the preparation and characterization of bifunctional magnetic nanoparticles (BMNPs) which contain a carboxylic moiety for drug binding and an amine moiety for folate mediated drug targeting. BMNPs were prepared by introducing bioactive cysteine molecules onto the surface of undecenoic acid coated Fe3O4 magnetic nanoparticles (UMNPs) via a thiol-ene click reaction and then, folic acid was conjugated with these BMNPs through an EDC-NHS coupling reaction. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis indicate the formation of highly crystalline single-phase Fe3O4 nanostructures. The changes in the interfacial characteristics of the nanoparticles and the presence of an organic coating are evident from Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), zeta-potential measurement, and thermogravimetric analysis (TGA). These nanocarriers have an average size of 10 nm, and have a pH dependent charge conversional feature and protein resistance characteristic in physiological medium. These nanoparticles also show high loading affinity for an anticancer drug, doxorubicin hydrochloride (DOX) and its pH dependent release. This is highly beneficial for cancer therapy as the relatively low pH in tumors will specifically stimulate the drug release at the site of interest. Furthermore, our fluorescence microscopy and flow cytometry studies confirmed the higher cellular internalization capability of these folic acid conjugated nanoparticles in cancer cells over-expressing folate receptors.

Magnetic properties of 2D nickel nanostrips: structure dependent magnetism and Stoner criterion.

We have investigated different geometries of two-dimensional (2D) infinite length Ni nanowires of increasing width using spin density functional theory calculations. Our simulations demonstrate that the parallelogram motif is the most stable and structures that incorporate the parallelogram motif are more stable as compared to rectangular structures. The wires are conducting and the conductance channels increase with increasing width. The wires have a non-linear behavior in the ballistic anisotropic magnetoresistance ratios (BAMR) with respect to the magnetization directions. All 2D nanowires as well as Ni (1 1 1) and Ni (1 0 0) monolayer investigated are ferromagnetic under the Stoner criterion and exhibit enhanced magnetic moments as compared to bulk Ni and the respective Ni monolayers. The easy axis for all nickel nanowires under investigation is observed to be along the wire axis. The double rectangular nanowire exhibits a magnetic anomaly with a smaller magnetic moment when compared to Ni (1 0 0) monolayer and is the only structure with an easy axis perpendicular to the wire axis. The Stoner parameter which has been known to be structure independent in bulk and surfaces is found to vary with the structure and the width of the nanowires. The less stable rectangular and rhombus shaped nanowires have a higher ferromagnetic strength than parallelogram shaped nanowires.

Experimental and theoretical investigations on magnetic behavior of (Al,Co) co-doped ZnO nanoparticles.

We present the structural and magnetic properties of Zn(0.95-x)Co(0.05)Al(x)O (x = 0.0 to 0.1) nanoparticles, synthesized by a novel sol-gel route followed by pyrolysis. Powder X-ray diffraction data confirms the formation of a single phase wurtzite type ZnO structure for all the compositions. The Zn(0.95)Co(0.05)O nanoparticles show diamagnetic behavior at room temperature. However, when Al is co-doped with Co with x = 0.0 to 0.10 in Zn(0.95-x)Co(0.05)Al(x)O, a systematic increase in ferromagnetic moment is observed up to x = 0.07 at 300 K. Above x = 0.07 (e.g. for x = 0.10) a drastic decrease in ferromagnetic nature is observed which is concomitant with the segregation of poorly crystalline Al rich ZnO phase as evidenced from TEM studies. Theoretical studies using density functional calculations on Zn(0.95-x)Co(0.05)Al(x)O suggest that the partial occupancy of S2 states leads to an increased double exchange interaction favoring the ferromagnetic ground states. Such ferromagnetic interactions are favorable beyond a threshold limit. At a high level doping of Al, the exchange splitting is reduced, which suppresses the ferromagnetic ordering.

Preparation and characterization of ultrafine co and ni particles in a polymer matrix.

A facile route for in situ synthesis of Co and Ni nanoparticles in a preorganized polyacrylamide gel is reported. Metal-polymer composites were prepared by gamma-irradiation at room temperature. The Co nanoparticles were roughly 3-5 nm in size and were stable in the polymer matrix in the presence of air. The presence of Co and Ni nanoparticles was established by their ability to transfer an electron to methyl viologen {paraquat: 1,1'-dimethyl 4,4'-dipyridinium dichloride; MV(2+) (Cl(-))(2)}. The Co and Ni nanoparticles were probed for their magnetic characteristics by a superconducting quantum interferometer device (SQUID) magnetometer and display a low superparamagnetic blocking temperature T(B) of about 13 and 10 K, respectively. The field-dependent magnetic behavior below T(B) displays the standard features corresponding to superparamagnetism, as expected for very small Co and Ni crystallites. This also suggests that particles are polycrystalline in nature.