Perflutren lipid microsphere injectable suspension for cardiac ultrasound

Engineering Lipid Spherulites for the Sustained Release of Highly Dosed Small Hydrophilic Compounds

Currently, there is a lack of parenteral sustained release formulations for the delivery of highly dosed small hydrophilic drugs. Therefore, parenteral lipid spherulites are engineered capable of entrapping large amounts of such compounds and spontaneously releasing them in a sustained fashion. A library of spherulites is prepared with a simple green process, using phosphatidylcholine (PC) and/or phosphatidylethanolamine (PE), nonionic surfactants and water. The vesicle formulations exhibiting appropriate size distribution and morphology are selected and loaded with 4,6-di-O-(methoxy-diethyleneglycol)-myo-inositol-1,2,3,5-tetrakis(phosphate), ((OEG₂ )₂ -IP4), an inositol phosphate derivative currently under clinical evaluation for the treatment of aortic valve stenosis. The loading efficiency of spherulites is up to 12.5-fold higher than that of liposomes produced with the same materials. While the PC-containing vesicles showed high stability, the PE spherulites gradually lost their multilayer organization upon dilution, triggering the active pharmaceutical ingredient (API) release over time. In vitro experiments and pharmacokinetic studies in rats demonstrated the ability of PE spherulites to increase the systemic exposure of (OEG₂ )₂ -IP4 up to 3.1-fold after subcutaneous injection, and to completely release their payload within 3-4 d. In conclusion, PE spherulites represent a promising lipid platform for the extravascular parenteral administration of highly dosed small hydrophilic drugs.

Ultrasound and Microbubbles for the Treatment of Ocular Diseases: From Preclinical Research towards Clinical Application

The unique anatomy of the eye and the presence of various biological barriers make efficacious ocular drug delivery challenging, particularly in the treatment of posterior eye diseases. This review focuses on the combination of ultrasound and microbubbles (USMB) as a minimally invasive method to improve the efficacy and targeting of ocular drug delivery. An extensive overview is given of the in vitro and in vivo studies investigating the mechanical effects of ultrasound-driven microbubbles aiming to: (i) temporarily disrupt the blood–retina barrier in order to enhance the delivery of systemically administered drugs into the eye, (ii) induce intracellular uptake of anticancer drugs and macromolecules and (iii) achieve targeted delivery of genes, for the treatment of ocular malignancies and degenerative diseases. Finally, the safety and tolerability aspects of USMB, essential for the translation of USMB to the clinic, are discussed.

Definity, an affinity for painful crisis: a case series describing vaso-occlusive pain crises in sickle cell patients undergoing echocardiogram with Definity contrast

Background 

Individuals with sickle cell disease (SCD) are at risk for painful crises and long-term cardiopulmonary morbidity. Echocardiogram is recommended if signs or symptoms of cardiopulmonary disease develop in previously asymptomatic patients, or worsen in those with known disease. Second-generation echocardiogram contrast agents (ECAs) improve the diagnostic capacity of echocardiogram; however, these agents have risks in SCD populations that have yet to be investigated.

Case summary 

We report a case series of two patients who experienced vaso-occlusive crises following administration of the ECA, Definity. Both patients were referred for echocardiogram from our institution's sickle cell clinic because of concern for SCD-related cardiopulmonary complications. Both patients were in their usual state of health at the time of their exams. The first patient experienced acute back and hip pain minutes after receiving Definity and was diagnosed with acute vaso-occlusive crisis requiring admission for 6 days for pain management. The second patient developed dyspnoea and chest pain within 90 min of her echocardiogram. She was diagnosed with acute chest syndrome and admitted for further management. Her hospitalization was complicated by hyper-haemolysis and multiple organ failure syndrome. After 13 days, she was discharged home.

Discussion 

The safety profile of ECAs has not been fully evaluated and warrants further study in individuals with SCD. Proposed mechanisms for our observations include the release of pro-inflammatory metabolites from Definity contrast agent's shell and ultrasound-induced haemolysis secondary to ECA administration. Alternative imaging modalities and proper precautions should be considered when evaluating cardiopulmonary function in this patient population.

Three Decades of Ultrasound Contrast Agents: A Review of the Past, Present and Future Improvements

Initial reports from the 1960s describing the observations of ultrasound contrast enhancement by tiny gaseous bubbles during echocardiographic examinations prompted the development of the first ultrasound contrast agent in the 1980s. Current commercial contrast agents for echography, such as Definity, Optison, Sonazoid and SonoVue, have proven to be successful in a variety of on- and off-label clinical indications. Whereas contrast-specific technology has seen dramatic progress after the introduction of the first approved agents in the 1990s, successful clinical translation of new developments has been limited during the same period, while understanding of microbubble physical, chemical and biologic behavior has improved substantially. It is expected that for a successful development of future opportunities, such as ultrasound molecular imaging and therapeutic applications using microbubbles, new creative developments in microbubble engineering and production dedicated to further optimizing microbubble performance are required, and that they cannot rely on bubble technology developed more than 3 decades ago.