title: Balancing stealth and echogenic properties in an ultrasound contrast agent with drug delivery potential.
abstract: Contrast agents are currently being modified to combine diagnostic and therapeutic capabilities. For ultrasound (US) imaging with polymeric contrast agents, it is necessary to modify the shell to create "stealth" microbubbles but without these modifications sacrificing the agent's ability to interact with the focused US beam. We hypothesize that addition of the classic immune shielding molecule polyethylene glycol (PEG) to a polylactide (PLA) microbubble shell will affect the acoustic and physical properties of the resulting agents. In an effort to determine the best formulation to achieve a balance between stealth and acoustic activity, we compared two PEGylation techniques; addition of increasing amounts of PEG-PLA copolymer and employing incorporation of a PEG lipid (LipidPEG) into the shell. Loss of acoustic enhancement occurred in a dose-dependent manner for both types of PEGylated agents (loss of signal occurred at >5 wt% PEG-PLA and >1 wt% LipidPEG), while immune activation was also reduced in a dose-dependent manner for the PEG-PLA agents. This study shows that the balance between acoustic behavior and improved immune avoidance was scalable and successful to different degrees with both PEGylation methods, and was best achieved using for PEG-PLA at 5 wt% and for LipidPEG at 1 wt%. Studies are ongoing to evaluate the best method for the targeting and drug delivery capabilities of these agents for applications in cancer treatment. This study represents the basis for understanding the consequences of making modifications to the native polymeric shell.
authors.affiliation: Drexel University School of Biomedical Engineering, Science & Health Systems, 3141 Chestnut Street, Philadelphia, PA 19104, USA.
authors.forename: Lauren J
authors.initials: LJ
authors.lastname: Jablonowski
authors.affiliation: Drexel University School of Biomedical Engineering, Science & Health Systems, 3141 Chestnut Street, Philadelphia, PA 19104, USA.
authors.forename: David
authors.initials: D
authors.lastname: Alfego
authors.affiliation: Drexel University School of Biomedical Engineering, Science & Health Systems, 3141 Chestnut Street, Philadelphia, PA 19104, USA.
authors.forename: James I
authors.initials: JI
authors.lastname: Andorko
authors.affiliation: Thomas Jefferson University, Department of Radiology, 132 South 10th Street, Philadelphia, PA 19107, USA.
authors.forename: John R
authors.initials: JR
authors.lastname: Eisenbrey
authors.affiliation: Drexel University School of Biomedical Engineering, Science & Health Systems, 3141 Chestnut Street, Philadelphia, PA 19104, USA.
authors.forename: Nutte
authors.initials: N
authors.lastname: Teraphongphom
authors.affiliation: Drexel University School of Biomedical Engineering, Science & Health Systems, 3141 Chestnut Street, Philadelphia, PA 19104, USA. Electronic address: wheatley@coe.drexel.edu.
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Wheatley
mesh_terms: D003287:Contrast Media / Q000737:chemistry* / Q000528:radiation effects / Q000627:therapeutic use*; D019220:High-Energy Shock Waves; D008422:Materials Testing; D045423:Microbubbles; D011108:Polymers / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013010:Sonication / Q000379:methods*; D000068936:Theranostic Nanomedicine / Q000379:methods; D014463:Ultrasonography / Q000379:methods*
chemical_list: D003287:Contrast Media; D011108:Polymers
keywords: Cavitation; Echogenicity; PEGylation; Shell properties; Stealth; Ultrasound contrast agents