Development of magnetic encapsulated microbubble agents that can integrate multiple diagnostic and therapeutic functions is a key focus in both biomedical engineering and nanotechnology and one which will have far-reaching impact on medical diagnosis and therapies. However, properly designing multifunctional agents that can satisfy particular diagnostic/therapeutic requirements has been recognized as rather challenging, because there is a lack of comprehensive understanding of how the integration of magnetic nanoparticles to microbubble encapsulating shells affects their mechanical properties and dynamic performance in ultrasound imaging and drug delivery. Here, a multifunctional imaging contrast and in-situ gene/drug delivery agent was synthesized by coupling super paramagnetic iron oxide nanoparticles (SPIOs) into albumin-shelled microbubbles. Systematical studies were performed to investigate the SPIO-concentration-dependence of microbubble mechanical properties, acoustic scattering response, inertial cavitation activity and ultrasound-facilitated gene transfection effect. These demonstrated that, with the increasing SPIO concentration, the microbubble mean diameter and shell stiffness increased and ultrasound scattering response and inertial cavitation activity could be significantly enhanced. However, an optimized ultrasound-facilitated vascular endothelial growth factor transfection outcome would be achieved by adopting magnetic albumin-shelled microbubbles with an appropriate SPIO concentration of 114.7?µg?ml(-1). The current results would provide helpful guidance for future development of multifunctional agents and further optimization of their diagnostic/therapeutic performance in clinic.
In the present study, power ultrasound is applied to improve the permeability of the solid-state fabricated PLA foams with different cell sizes. It is experimentally proved that cell interconnection and the permeability is improved with the increasing of power ultrasound radiation intensity. Furthermore, an insert-substitution testing approach is put forward to perform acoustic measurement and property characterization for the PLA foams before and after ultrasound radiation. The experimental results indicate that the attenuation coefficient of the close-celled PLA foams decreases exponentially with respect to the saturation pressure and it shows linear behavior with respect to the ultrasound radiation intensity. The favorable results suggest the feasibility of the proposed technologies of ultrasound-assisted permeability improvement and acoustic characterization for the application of the solid-state foamed PLA foams in tissue engineering.
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