Small particulate gadolinium oxide and gadolinium oxide albumin microspheres as multimodal contrast and therapeutic agents.
OBJECTIVE
To prepare and characterize new particulate contrast media, small particulate gadolinium oxide (SPGO) and gadolinium oxide albumin microspheres (GOAM), as prototype multimodal imaging and therapeutic agents.


METHODS
SPGO was purchased from Alfa Aesar Inc. (Ward Hill, MA). GOAM were synthesized via ultrasonic irradiation using SPGO and 5% bovine serum albumin in aqueous solution. SPGO and GOAM were characterized by size, concentration, structure, and gadolinium content. Their relaxivity at high magnetic field strength and x-ray attenuating abilities were evaluated in 0.4% agar gel at room temperature.


RESULTS
SPGO were confirmed to be 20-40 nm in diameter. GOAM have an average size of 2 to 5 microm and show a relatively homogeneous distribution of SPGO within the albumin microspheres. T1 and T2 relaxivity of GOAM was 6.7 seconds(-1) mmol/L(-1) and 38.5 seconds(-1) mmol/L(-1), respectively, while that of SPGO was 0.2 seconds(-1) mmol/L(-1) and 6.8 seconds(-1) mmol/L(-1), respectively. At 0, 0.004, 0.16, 4.0, and 16.0 mmol/L SPGO, x-ray attenuation values were measured at 2.11, 3.48, 7.06, 39.83, and 187.33 Hounsfield units, respectively.


CONCLUSIONS
Use of SPGO and SPGO encapsulated in non-heat-hardened albumin microspheres (GOAM) represents a new approach. SPGO and GOAM have suitable physicochemical properties to warrant further biophysical and animal studies and reevaluation of toxicity limitations.
McDonald
Michael A
MA
Medical Imaging Research Laboratory, University of Illinois at Urbana-Champaign, Champaign, IL, USA.
Watkin
Kenneth L
KL
D000818:Animals; D003287:Contrast Media; D005682:Gadolinium; D006801:Humans; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging; D008863:Microspheres; D010316:Particle Size; D012710:Serum Albumin, Bovine; D014057:Tomography, X-Ray Computed
D003287:Contrast Media; C058230:gadolinium-bovine serum albumin complex; D012710:Serum Albumin, Bovine; C030581:gadolinium oxide; D005682:Gadolinium