Table 2 summarizes the results of these kinetic analyses performed with uncoated and lipid-coated SPIONs that were suspended at 0.02 to 1.0 mg/mL in different buffer systems. For uncoated SPIONs dispersed in citrate buffer, initial heating rates were slightly greater for dilute suspensions that were found to exhibit the smallest particle size (see Table 1). The apparently more effective conversion of magnetically induced particle relaxation into thermal energy that was measured in the MFG-1000 may be associated with the small void space around the sample in this device resulting in improved heat transfer. Thermal properties

of lipid-coated SPIONs at 0.02 mg/mL in different click here buffer systems were comparable suggesting limited surface adsorption of buffer components onto lipid-coated nanoparticles which is consistent with the earlier size analysis (see Table 1). Interestingly, initial heating CYT387 rates of lipid-coated SPIONs significantly increased at greater particle concentration. DLS data revealed a significantly increased hydrodynamic size of lipid-coated particles at greater particle density, which is anticipated to negatively affect the heating properties. Ultrastructural

analysis of these nanoassemblies using HRTEM may provide insights into why these larger superparamagnetic particles convert magnetically induced oscillation and relaxation more efficiently into heat. It may be possible that the apparent larger particle size may correspond to encapsulation of several superparamagnetic Fe3O4 nanoparticles within a semisolid lipid particle that can experience enhanced relaxation loss during temperature-induced sol-gel transition of the lipid phase. Table 2 Initial heating rates of uncoated and lipid-coated Sitaxentan SPIONs following exposure to an alternating magnetic field Particle concentration/suspension vehicle Initial heating rate (°C/min) MFG-1000

at 7.0 mT (1 MHz) MHS at 16.6 mT (13.6 MHz) Uncoated SPIONs Lipid-coated SPIONs Uncoated SPIONs Lipid-coated SPIONs 1 mg/mL (Citrate buffer) 0.88 ± 0.02 1.26 ± 0.03** 0.35 ± 0.01 0.61 ± 0.02** 0.24 mg/mL (Citrate buffer) 0.90 ± 0.02 1.05 ± 0.04 0.36 ± 0.02 0.56 ± 0.01 0.02 mg/mL (Citrate buffer) 0.95 ± 0.03* 0.94 ± 0.02 0.47 ± 0.01* 0.46 ± 0.01 0.02 mg/mL (HBSS) 0.66 ± 0.02 0.94 ± 0.01 0.33 ± 0.01 0.44 ± 0.02 0.02 mg/mL (PBS) 0.55 ± 0.02 0.92 ± 0.02 0.20 ± 0.01 0.43 ± 0.01 Data are shown as mean ± SD (n = 3). *Significantly different from uncoated control SPIONs at 0.02 mg/mL (p < 0.05). **Significantly different from lipid-coated SPIONs at 0.02 mg/mL in citrate buffer (p < 0.05). Conclusion The results from this study demonstrate that surface immobilization of an equimolar DPPC/DPPG mixture on SPIONs via high-affinity avidin-biotin interactions increases colloidal stability in the presence of different buffer ions. Citrate buffer, pH 7.4, provides a significant advantage during avidin coating due to efficient colloid dispersion as a consequence of negative surface charge.