Thursday, December 21, 2017

mPEG-PLA from PolySciTech investigated for use as an ultrasound contrast-agent

Ultrasound imaging is widely used as a diagnostic tool in medicine, but suffers from the drawback of relatively poor contrast. For this reason, this technique is often used after injection of a specific contrast agent, such as microbubbles or liposomes containing mannitol, to provide for improved imaging of features within the tissue. Recently, researchers from The George Washington University and North Dakota State University utilized mPEG-PLLA (Polyvivo AK004) from PolySciTech (www.polyscitech.com) to generate acoustic polymersomes as a contrast agent and investigated their acoustic properties. This research holds promise for improving the diagnostic capabilities of ultrasound. Read more: Xia, Lang, Fataneh Karandish, Krishna Nandan Kumar, James Froberg, Prajakta Kulkarni, Kara N. Gange, Yongki Choi, Sanku Mallik, and Kausik Sarkar. "Acoustic Characterization of Echogenic Polymersomes Prepared From Amphiphilic Block Copolymers." Ultrasound in medicine & biology (2017). https://www.sciencedirect.com/science/article/pii/S0301562917324092

“Abstract: Polymersomes are a class of artificial vesicles prepared from amphiphilic polymers. Like lipid vesicles (liposomes), they too can encapsulate hydrophilic and hydrophobic drug molecules in the aqueous core and the hydrophobic bilayer respectively, but are more stable than liposomes. Although echogenic liposomes have been widely investigated for simultaneous ultrasound imaging and controlled drug delivery, the potential of the polymersomes remains unexplored. We prepared two different echogenic polymersomes from the amphiphilic copolymers polyethylene glycol–poly-DL-lactic acid (PEG-PLA) and polyethylene glycol–poly-L-lactic acid (PEG-PLLA), incorporating multiple freeze-dry cycles in the synthesis protocol to ensure their echogenicity. We investigated acoustic behavior with potential applications in biomedical imaging. We characterized the polymeric vesicles acoustically with three different excitation frequencies of 2.25, 5 and 10 MHz at 500 kPa. The polymersomes exhibited strong echogenicity at all three excitation frequencies (about 50- and 25-dB enhancements in fundamental and subharmonic, respectively, at 5-MHz excitation from 20 µg/mL polymers in solution). Unlike echogenic liposomes, they emitted strong subharmonic responses. The scattering results indicated their potential as contrast agents, which was also confirmed by clinical ultrasound imaging. Key Words: Ultrasound imaging; Contrast agent; Microbubble; Polymersomes; Echogenic; Drug delivery”
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