title: Characterization of mechanical properties of hybrid contrast agents by combining atomic force microscopy with acoustic/optic assessments.
abstract: Multi-parameter fitting algorithms, which are currently used for the characterization of coated-bubbles, inevitably introduce uncertainty into the results. Therefore, a better technique that can accurately determine the microbubbles' mechanical properties is urgently needed. A comprehensive technology combining atomic force microscopy, optical, and acoustic measurements with simulations of coated-bubble dynamics was developed. Using this technique, the mechanical parameters (size distribution, shell thickness, elasticity, and viscosity) of hybrid (ultrasound/magnetic-resonance-imaging) contrast microbubbles and their structure-property relationship were determined. The measurements indicate that when more superparamagnetic iron oxide nanoparticles are embedded in the microbubbles' shells, their mean diameter and effective viscosity increase, and their elastic modulus decreases. This reduces the microbubbles' resonance frequency and thus enhances acoustic scattering and attenuation effects.
authors.affiliation: Key Laboratory of Modern Acoustics (MOE), Department of Physics, Collaborative Innovation Center of Advanced Microstructure, Nanjing University, Nanjing 210093, China; Key Laboratory of Optoelectronics of Jiangsu Province, School of Physics and Technology, Nanjing Normal University, Nanjing 210046, China.
authors.forename: Gepu
authors.initials: G
authors.lastname: Guo
authors.affiliation: Key Laboratory of Modern Acoustics (MOE), Department of Physics, Collaborative Innovation Center of Advanced Microstructure, Nanjing University, Nanjing 210093, China. Electronic address: juantu@nju.edu.cn.
authors.forename: Juan
authors.initials: J
authors.lastname: Tu
authors.affiliation: Key Laboratory of Modern Acoustics (MOE), Department of Physics, Collaborative Innovation Center of Advanced Microstructure, Nanjing University, Nanjing 210093, China.
authors.forename: Xiasheng
authors.initials: X
authors.lastname: Guo
authors.affiliation: Department of Ultrasound, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou 310009, China.
authors.forename: Pintong
authors.initials: P
authors.lastname: Huang
authors.affiliation: Department of Physics, University of Vermont, Burlington, VT 05405, USA.
authors.forename: Junru
authors.initials: J
authors.lastname: Wu
authors.affiliation: Key Laboratory of Modern Acoustics (MOE), Department of Physics, Collaborative Innovation Center of Advanced Microstructure, Nanjing University, Nanjing 210093, China; The State Key Laboratory of Acoustics, Chinese Academy of Science, Beijing 10080, China. Electronic address: dzhang@nju.edu.cn.
authors.forename: Dong
authors.initials: D
authors.lastname: Zhang
mesh_terms: D000465:Algorithms; D003287:Contrast Media / Q000737:chemistry*; D055119:Elastic Modulus; D008279:Magnetic Resonance Imaging; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D045423:Microbubbles; D018625:Microscopy, Atomic Force; D014463:Ultrasonography; D014783:Viscosity
chemical_list: D003287:Contrast Media; D058185:Magnetite Nanoparticles
keywords: Albumin-shell microbubbles; Hybrid US/MR imaging contrast agents; Mechanical property characterization; Structure–property relationship; Superparamagnetic iron oxide nanoparticles