title: Binding and detachment dynamics of microbubbles targeted to P-selectin under controlled shear flow.
abstract: This study was performed to assess the binding kinetics of a targeted microbubble contrast agent exposed to shear stress. An ultrasound contrast targeted to P-selectin was designed by conjugating monoclonal antibodies against murine P-selectin (RB40.34) to the lipid monolayer shell of the microbubble using poly(ethylene glycol)-biotin-streptavidin. The attachment and detachment of targeted microbubbles to P-selectin immobilized on a culture dish were assessed in a parallel-plate flow chamber. Targeted microbubbles (5 x 10(6) particles/ml) drawn through the flow chamber coated with P-selectin (109 sites/microm(2)) at a shear stress of 0.3 dyn/cm(2) accumulated at a rate of 565 mm(-2) min(-1). Attachment rates increased at higher plate surface densities of P-selectin, and microbubble detachment was reduced. Accumulation rate first increased with shear stress, reached a maximum at approximately 0.6 dyn/cm(2) and then decreased. Control experiments on a plate that lacked P-selectin, or was blocked with mAb RB40.34, resulted in minimal bubble attachment. Microbubble detachment was tested by ramping up shear stress at 30-s intervals. Half-maximal detachment was reached at 34 dyn/cm(2). Overall, accumulation and retention of targeted ultrasound contrast agents is possible under physiologic flow conditions and is strongly influenced by shear stress and surface density of the target receptor.
authors.affiliation: Cardiovascular Research Center and Department of Biomedical Engineering, University of Virginia Health System, Charlottesville, VA 22908-1394, USA.
authors.forename: Amol M
authors.initials: AM
authors.lastname: Takalkar
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Klibanov
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Rychak
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Lindner
authors.forename: Klaus
authors.initials: K
authors.lastname: Ley
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry; D001710:Biotin; D002214:Capsules; D003692:Delayed-Action Preparations; D004339:Drug Compounding; D005079:Excipients; D018715:Microscopy, Video; D019007:P-Selectin / Q000008:administration & dosage / Q000737:chemistry*; D012212:Rheology; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D000911:Antibodies, Monoclonal; D002214:Capsules; D003692:Delayed-Action Preparations; D005079:Excipients; D019007:P-Selectin; D001710:Biotin