Stabilization of Gas Bubbles Released from Water-Soluble Carbohydrates Using Amphiphilic Compounds: Preparation of Formulations and Acoustic Monitoring of Bubble Lifetime
The ultrasound contrast agents Echovist® and Levovist® (Bayer AG, Schering AG, Germany) are based on the release of gas bubbles from milled α-d-galactose. In diagnostic ultrasound, for this class of contrast agents, there is a need for prolonged contrast duration. To investigate if new carbohydrate compositions could prolong the lifetime of the gas bubbles, α-d-galactose was mixed with other carbohydrates or amphiphiles with varying log P. Acoustic attenuation vs. time (390 s) area under the curve (A390) and bubble half-time (t½) were used as measures of prolonged lifetime of gas bubbles. The products, to which 0.1% of a lipophilic carboxylic acid (5β-cholanic acid, behenic acid, and melissic acid) has been added, showed more than 5, 7 and 11 times enhancement of A390, respectively, compared with the reference compound 2 (RC2) corresponding to the commercial product Levovist®. The half-time t ½ of the same compounds was prolonged more than 6 times compared with RC2. A partial least square (PLS) statistical analysis confirmed that, for additives, high log P carboxylic acids lead to the highest A390. The present results bear a promise of products with a more persistent in vivo ultrasound contrast effect than the commercially available agents.
Preclinical and Clinical Results with an Ultrasonic Contrast Agent
Fritzsch Th, Schartl M, Siegert J. Preclinical and clinical results with an ultrasonic contrast agent. Invest Radiol 1988;23(Suppl 1):S302‐S305. In comparison to diagnostic radiology, ultrasound diagnostics has had no real contrast media. Theoretical considerations indicate that gas liquid systems seem to be favorable. The echocontrast agent SH U 454 is a system that releases minute gas bubbles that provide the contrast properties. Preclinical and clinical trials in more than 500 patients with right‐heart lesions proved the efficacy and tolerance of the agent. Initial investigations showed that SH U 454 also may be useful in fields (eg, urology, gynecology) other than cardiology.
Catalytic removal of tert-butyldimethylsilyl (TBS) ether by PVP-I
Abstract A mild, efficient and rapid protocol the deprotection of alcoholic TBDMS ethers using PVP-1 as catalyst in methanol, the procedure of deprotection of various TBDMS ethers were found to be very convenient, easy work-up, high yielding.