Synthesis of PdO-USPION via Spark Ablation: For Thermal Ablation and Contrast Enhancement

Abstract

Conventional
early-stage breast cancer treatments such as surgery, chemotherapy and external
radiotherapy despite their proven short-term efficacy tend to have adverse
long-term physiological and psychological implications on the patients. This is
primarily due to their inability to spare healthy tissue surrounding the tumor.
Use of radioactive palladium (103Pd) seeds for producing localized
effect with brachytherapy is already in practice. However, they are known to
result in uneven dose distribution with creation of "hot spots" in
the vicinity of seed implants. Alternatively, conventional thermal ablation or
hyperthermia treatments using mechanical or electromagnetic systems also have
difficulties with localizing the thermal effect to the target region. Composite
and biocompatible palladium- (Ultra-small) superparamagnetic iron oxide
nanoparticles (PdO-USPION) on the other hand have the potential to diffuse
throughout the tumor ensuring relatively more uniform dose distribution and
improve the ease of clearance from the biological system without causing
long-term side effects. Magnetic property of (Ultra small) superparamagnetic
iron oxide nanoparticles can be exploited to induce and deliver heat energy to kill
cancerous cells upon exposure to Alternating magnetic field (AMF) and generate
contrast enhanced magnetic resonance images (MRI) by subjecting them to static
magnetic fields. Heating and contrast enhancement ability depends on the
physical, chemical and magnetic properties of nanoparticles which in turn rely
on the synthesis method. In this research, spark ablation technology is
employed to produce the nanoparticles from metallic electrodes. Although, for
the purpose of the current research, inactive palladium is used to reduce
complexity given that the synthesis of PdO-USPIONs with this synthesis method
is employed for the first time through this research. Inter-metallic Pd-Fe are
generated in the spark discharge system and captured in an aqueous media resulting
in (oxidized intermetallic palladium ultra-small superparamagnetic iron oxide
nanoaparticles) PdO-USPIONs. Since the synthesis method is relatively new,
major component of the research deals with investigating the influence of
system parameters on production of nanoparticles. Characterization results
associated with USPIONs and PdO-USPIONs are thoroughly analyzed to optimize the
setup to generate tunable PdO-USPIONs and to evaluate their performance as
thermal and contrast agents. Use of citric acid as surfactant to lower
agglomeration resulting in improved T1 relaxation behavior is also
studied.