This paper reports the creation of Au nanoparticles (AuNP) that are soluble in aqueous solution over a broad range of pH and ionic strength values and that are capable of selective uptake by folate receptor positive (FR+) cancer cells. A novel poly(ethylene glycol) (PEG) construct with thioctic acid and folic acid coupled on opposite ends of the polymer chain was synthesized for targeting the AuNP to FR+ tumor cells via receptor-mediated endocytosis. These folic acid-PEG-thioctic acid conjugates were grafted onto 10-nm-diameter Au particles in aqueous solution. The resulting folate-PEG-coated nanoparticles do not aggregate over a pH range of from 2 to 12 and at electrolyte concentrations of up to 0.5 M NaCl with particle concentrations as high as 1.5 x 10(13) particles/mL. Transmission electron microscopy was used to document the performance of these coated nanoparticles in cell culture. Selective uptake of folate-PEG grafted AuNPs by KB cells, a FR+ cell line that overexpress the folate receptor, was observed. AuNP uptake was minimal in cells that (1) do not overexpress the folate receptor, (2) were exposed to AuNP lacking the folate-PEG conjugate, or (3) were co-incubated with free folic acid in large excess relative to the folate-PEG grafted AuNP. Understanding this process is an important step in the development of methods that use targeted metal nanoparticles for tumor imaging and ablation.

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We use first-principles total-energy calculations based on density functional theory to study the site occupancy and magnetic properties of Al-substituted M -type strontium hexaferrite SrFe12−xAlxO19 with x = 0.5 and x = 1.0. We find that the non-magnetic Al 3+ ions preferentially replace Fe 3+ ions at two of the majority spin sites, 2a and 12k, eliminating their positive contribution to the total magnetization causing the saturation magnetization Ms to be reduced as Al concentration x is increased. Our formation probability analysis further provides the explanation for increased magnetic anisotropy field when the fraction of Al is increased. Although Al 3+ ions preferentially occupy the 2a sites at a low temperature, the occupation probability of the 12k site increases with the rise of the temperature. At a typical annealing temperature (> 700 • C) Al 3+ ions are much more likely to occupy the 12k site than the 2a site. Although this causes the magnetocrystalline anisotropy K1 to be reduced slightly, the reduction in Ms is much more significant. Their combined effect causes the anisotropy field Ha to increase as the fraction of Al is increased, consistent with recent experimental measurements.[4] decreased coercivity. However, the coercivity of the M-type hexaferrites is not increased significantly by these cation substitutions, and is still much smaller than that of Nd-Fe-B magnet [15].Al substitution in the M-type hexaferrite has been more effective in enhancing coercivity [16][17][18][19][20]. Particularly, Wang et al synthesized Al-doped SFO SrFe 12−x Al x O 19 (SFAO) with Al content of x = 0 − 4 using glycinnitrate method and subsequent annealing in a temperature over 700 • C obtaining the largest coercivity of 17.570 kOe, which is much larger than that of SFO (5.356 kOe) and exceeds even the coercivity of the Nd 2 Fe 17 B (15.072 kOe) [1]. Wang and co-workers also observed that the coercivity of the SFAO increases with increasing Al concentration at a fixed annealing temperature. These results call for a systematic understanding, from first principles, of why certain combinations of dopants lead to particular results. This theoretical understanding will be essential in systematically tailoring the properties of SFO.