Preparation and characterization of citric acid-modified superparamagnetic iron oxide nanoparticles / 北京大学学报(医学版)

OBJECTIVE@#To prepare and characterize citric acid (CA)-modified super paramagnetic iron oxide nanoparticles (SPIONs) for magnetic targeting, hyperthermia and magnetic resonance imaging (MRI).@*METHODS@#CA-modified SPIONs (CA-SPIONs) were prepared by co-precipitation method and then the magnetic responsiveness, morphology, particle size, infrared feature, weight percentage of CA, magnetic property and X-ray diffraction pattern of CA-SPIONs were respectively characterized by magnet, transmission electron microscope, laser particle size analyzer, Fourier transform infrared (FT-IR) spectroscopy, thermogravimetry-differential thermal analyzer, vibrating sample magnetometer and X-ray diffractometer (XRD). The heating efficiency of the CA-SPIONs was investigated by a high frequency induction heater. The transverse relaxivity (r2) of the CA-SPIONs was evaluated by a 3.0 T MRI scanner.@*RESULTS@#The CA-SPIONs prepared were dispersed well in water with a dark black color and had good magnetic responsiveness. The CA-SPIONs were spherical in shape and uniform in size with an average size around 12 nm. The hydrodynamic average size of the CA-SPIONs was (72.35±4.47) nm with a polydispersity index of 0.231 ± 0.029. The result of infrared spectrum indicated that CA was successfully modified to the surface of SPIONs. The result of thermogravimetric analysis showed that the weight percentage of CA modified on the CA-SPIONs was 9.0%. The result of magnetic property evaluation demonstrated that the CA-SPIONs exhibited excellent superparamagetism with a saturation magnetism of 63.58 emu/g. The XRD result indicated that the CA-SPIONs were in inverse spinel structure. The crystallite size of the CA-SPIONs was calculated to be 12.4 nm by Debye-Scherrer equation. Under the high frequency alternating electromagnetic field with electric current of 9 A and frequency ranging from 45 to 50 kHz, the CA-SPIONs exhibited excellent heating efficiency and the specific absorption rate (SAR) value was calculated to be 26 W/g. The r2 of the CA-SPIONs was assessed to be 338 (mmol/L)-1×s-1 by a 3.0 T MRI scanner, which suggested the excellent negative contrast enhancement effect of the CA-SPIONs.@*CONCLUSION@#The CA-SPIONs are expected to be used as a promising agent for magnetic targeting, hyperthermia and MRI detection.

Preparation and evaluation of blank and doxorubicin loaded poly (acrylic acid) microspheres for embolization / 北京大学学报(医学版)

OBJECTIVE@#To prepare ion exchange doxorubicin-loaded poly (acrylic acid) microspheres (DPMs) and evaluate the properties of these chemoembolic agents.@*METHODS@#Poly (acrylic acid) microspheres (PMs) without drug were prepared by inverse suspension polymerization method and then doxorubicin was loaded by ion exchange mechanism to prepare DPMs. Optical microscope was used to investigate the morphology and particle size distribution of PMs and DPMs; fluorescence microscope and confocal microscope were used to observe the distribution of doxorubicin after drug loading. Elasticities of both the microspheres were evaluated by texture analyzer. High performance liquid chromatography (HPLC) method was established to determine the drug loading behavior of PMs and releasing behavior of DPMs. The in vivo embolic property was evaluated by embolizing the hepatic artery of a rabbit with 0.1 mL of DPMs.@*RESULTS@#PMs and DPMs were both spherical in shape, smooth in surface and dispersed well. Doxorubicin was mainly in the outer area inside of DPMs and distributed evenly. The average particle size of PMs and DPMs were (283±136) μm and (248±149) μm, respectively. PMs and DPMs both had good compression ability with the Young's modulus of (62.63±1.65) kPa and (93.94±1.10) kPa separately. PMs reached the drug loading balance at 12 h, and the entrapment efficiency was greater than 99%. Drug loading of PMs in doxorubicin solution at the concentration of 5.0 g/L and 12.5 g/L was (19.78±0.27) g/L and (49.45±0.37) g/L, respectively. Doxorubicin released slowly from DPMs in PBS and the accumulative release percentages of DPMs with corresponding drug loading were 6.82%±0.02% and 2.83%±0.10% after 24 h, respectively. Arterial angiograms showed that the hepatic artery of the rabbit was successfully embolized with DPMs.@*CONCLUSION@#DPMs with good performance of loading doxorubicin could be a potential embolic agent for transcatheter arterial chemoembolization.