Acoustically-active microbubbles conjugated to liposomes: characterization of a proposed drug delivery vehicle.

A new acoustically-active delivery vehicle was developed by conjugating liposomes and microbubbles, using the high affinity interaction between avidin and biotin. Binding between microbubbles and liposomes, each containing 5% DSPE-PEG2kBiotin, was highly dependent on avidin concentration and observed above an avidin concentration of 10 nM. With an optimized avidin and liposome concentration, we measured and calculated as high as 1000 to 10,000 liposomes with average diameters of 200 and 100 nm, respectively, attached to each microbubble.

Therapeutic effects of paclitaxel-containing ultrasound contrast agents.

Drug delivery vehicles that combine ultrasonic and molecular targeting are shown to locally concentrate a drug in a region-of-interest. The drug delivery vehicles, referred to as acoustically active lipospheres (AALs), are microbubbles surrounded by a shell of oil and lipid. In a region limited to the focal area of ultrasound application, circulating AALs are deflected by radiation force to a vessel wall and can subsequently be fragmented.

Ultrasound radiation force enables targeted deposition of model drug carriers loaded on microbubbles.

A novel drug delivery vehicle that specifically targets using ultrasound radiation force (USRF) and biotin-avidin interactions is presented. Model vehicles consist of avidinated fluorescent nanobeads bound directly to the biotinylated lipid shells of preformed microbubbles. USRF was used to deflect the vehicle from the center of flow to a tube surface in order to facilitate receptor-ligand mediated adhesion.

Dynamic shifts in LFA-1 affinity regulate neutrophil rolling, arrest, and transmigration on inflamed endothelium.

Polymorphonuclear leukocyte (PMN) recruitment to vascular endothelium during acute inflammation involves cooperation between selectins, G-proteins, and beta2-integrins. LFA-1 (CD11a/CD18) affinity correlates with specific adhesion functions because a shift from low to intermediate affinity supports rolling on ICAM-1, whereas high affinity is associated with shear-resistant leukocyte arrest. We imaged PMN adhesion on cytokine-inflamed endothelium in a parallel-plate flow chamber to define the dynamics of beta2-integrin function during recruitment and transmigration.

Leukocyte function-associated antigen 1-mediated adhesion stability is dynamically regulated through affinity and valency during bond formation with intercellular adhesion molecule-1.

Neutrophil rolling and transition to arrest on inflamed endothelium are dynamically regulated by the affinity of the beta(2) integrin CD11a/CD18 (leukocyte function associated antigen 1 (LFA-1)) for binding intercellular adhesion molecule (ICAM)-1. Conformational shifts are thought to regulate molecular affinity and adhesion stability. Also critical to adhesion efficiency is membrane redistribution of active LFA-1 into dense submicron clusters where multimeric interactions occur.

Inflammatory potential of neutrophils detected in sickle cell disease.

An early event in the inflammatory response is neutrophil recruitment to endothelium in response to chemotactic stimulation, which in turn activates CD18-integrin, which anchors neutrophils to the vessel wall under the shear force of blood flow. Activated neutrophils circulating in sickle cell disease (SCD) patients may significantly contribute to vascular occlusions (VOC) as neutrophils adherent to inflamed endothelium recruit sickle red blood cells inducing VOC. To elucidate the mechanisms by which neutrophils may participate in VOC in SCD, CD18-integrin expression and function in fresh blood samples of non-crisis patients were measured by flow cytometry.

Dynamic regulation of LFA-1 activation and neutrophil arrest on intercellular adhesion molecule 1 (ICAM-1) in shear flow.

Neutrophil recruitment during acute inflammation is triggered by G-protein-linked chemotactic receptors that in turn activate beta(2) integrin (CD18), deemed a critical step in facilitating cell capture and arrest under the shear force of blood flow. A conformational switch in the I domain allosteric site (IDAS) and in CD18 regulates LFA-1 affinity for endothelial ligands including intercellular adhesion molecule 1 (ICAM-1). We examined the dynamics of CD18 activation in terms of the efficiency of neutrophil capture of ICAM-1, and we correlated this with the membrane topography of 327C, an antibody that recognizes the active conformation of CD18 I-like domain.