Nondestructive Characterization of Biodegradable Polymer Erosion in Vivo Using Ultrasound Elastography Imaging

Abstract

Significant advancements in biodegradable polymeric materials have been made for numerous biomedical applications including tissue engineering, regenerative medicine, and drug delivery. The functions of these polymers within each application often rely on controllable polymer degradation and erosion, yet the process has proven difficult to measure in vivo. Traditional methods for investigating polymer erosion and degradation are destructive, hampering accurate longitudinal measurement of the samples in the same subject. To overcome this limitation, we have utilized ultrasound elastography imaging as a tool to nondestructively measure strain of poly­(lactic-co-glycolic acid) (PLGA) phase sensitive in situ forming implants (ISFI), which changes with progressive loss of structural integrity resulting from polymer erosion. Using this tool, we investigated erosion kinetics of implants comprised of three different PLGA molecular weights (18, 34, and 52 kDa) in vitro and in vivo. The in vitro environment was created using a novel polyacrylamide based tissue mimicking phantom while the in vivo experiment was performed subcutaneously using a rat abdominal model. A strong linear relationship independent of polymer molecular weight was found between average strain values and erosion values in both the in vitro and in vivo environment. Results support the use of a mechanical stiffness-based predicative model for longitudinal monitoring of material erosion and highlight the use of ultrasound elastography as a nondestructive tool for measuring polymer erosion kinetics.

Self-Enhanced Acoustic Impedance Difference Strategy for Detecting the Acidic Tumor Microenvironment

“…More importantly, with the development of materials science, a plenty of functional nanomaterials can be utilized to specifically respond to the microenvironment in vivo to regulate the characteristics of tissues such as frequency or elasticity. Subsequently, other special ultrasonic technologies, including ultrasonic harmonic imaging − or ultrasound elastography, − are capable of achieving the detection of the microenvironment, which can promote the great development of ultrasound molecular imaging. Although the particular value of the acidity in tumor was not achieved and the kinetic parameters to detect the acidic TME by BPP were not clear in this work, we believe that more accurate and real-time quantitative detection of the TME can be achieved with the rapid development of ultrasonic imaging technique and material science.…”

Optimization of the differentiation and quantification of high‐Z nanoparticles incorporated in medical devices for CT‐guided interventions

“…Imaging modalities such as ultrasound elastography, shear wave imaging, photoacoustic imaging, and near-infrared fluorescence are reported to measure the integrity of biomaterials in vivo. [6][7][8][9] However, in addition to having limited penetration depth, such imaging modalities are not routinely used nor readily available in the clinic. Researchers have investigated magnetic resonance imaging in monitoring the degradation of polyvinylidene fluoride 10 and collagen 11 labeled with ultrasmall superparamagnetic iron oxide, but degradation was not observed in these studies.…”

“…Few preclinical studies focus on visualizing biodegradable medical devices in vivo . Imaging modalities such as ultrasound elastography, shear wave imaging, photoacoustic imaging, and near‐infrared fluorescence are reported to measure the integrity of biomaterials in vivo 6–9 . However, in addition to having limited penetration depth, such imaging modalities are not routinely used nor readily available in the clinic.…”