Microbubbles applications

The most common application of carbon adsorption in municipal water treatment is in the removal of taste and odor compounds. Figure 12 provides an example of a process flow diagram for a municipal water treatment plant. In this example water is pumped from the river into a flotation unit, which is used for the removal of suspended solids such as algae and particulate matter. Dissolved air is the injected under pressure into the basin. This action creates microbubbles which become attached to the suspended solids, causing them to float. This results in a layer of suspended solids on the surface of the water, which is removed using a mechanical skimming technique. Go back to Chapter 8 if you need to refresh your memory on air flotation systems. 

The interaction of ultrasound waves with microbubbles allows a drug (including genetic material for gene therapy [10]) to be released from the particles selectively at the desired insonified areas of the body, thus allowing targeted delivery of therapeutic agents. Currently, this approach is still far from clinical application. 

Known or perceived disadvantages of ultrasound contrast agents are as follows. Microbubble agents with their size of several microns cannot escape from the bloodstream under normal conditions. Thus, the imaging cannot be performed in the areas outside the normal bloodstream. Essentially, microbubbles can only go where red blood cells do. Microbubble agents last only several minutes in the bloodstream. This makes their application less convenient for lengthy multi-plane examinations, and requires multiple boluses of contrast administration or a continuous infusion. 

In a similar approach, entrance of plasmid DNA into the cells for transfection was improved by ultrasound [10,80,81]. The term sonoporation was suggested to describe this application in general. In order to bind plasmid DNA, microbubbles have to carry a net positive charge. Microbubble-DNA constructs... 

The third chapter is dedicated to contrast agents for ultrasound imaging starting with the design, preparation and application of microbubbles. Additionally, the different presently available generations of contrast agents are... 

C.E. Lundgren, G.W. Bergoe, I.Tyssebotn, The theory and application of intravascular microbubbles as an ultra-effective means of transporting oxygen and other gases. Undersea Hyperb. Med. 31 (2004) 105-106. 

A.L. Klibanov, Microbubble contrast agents Targeted ultrasound imaging and ultra-sound-assisted drug-delivery applications. Invest. Radiol. 41 (2005) 354-362. 

E.C. Unger, T. Porter, W. Culp, R. Labell, T. Matsunaga, R. Zutshi, Therapeutic applications of lipid-coated microbubbles, Adv. Drug Deliv. Rev. 56 (2004) 1291-1314. 

K. Ferrara, R. Pollard, M. Borden, Ultrasound microbubble contrast agents fundamentals and application to gene and drug delivery, Ann. Rev. Biomed. Engineer. 9 (2007) 415-447. 

This last-mentioned successful series of control experiments, involving addition of cavitation nuclei to the cardiovascular system, brings to mind at least one feasible medical application for injected (synthetic) surfactant-stabilized microbubbles (cf. Chapters 9 and 10) as concerns evaluation of cardiovascular function. Various types of size-controlled, nontoxic, synthetic micro-... 

Apart from echocardiography, another promising clinical application of synthetic microbubbles is the ultrasonic monitoring of local blood flow in the abdomen (analogous to the earlier use of gas microbubbles to monitor myocardial perfusion (ref. 443)). Such refined ultrasonic blood flow measurements, utilizing injected... 

R.H. Simon, S.Y. Ho, D.F. Uphoff, S.C. Lange and J.S. D Arrigo, Applications of lipid-coated microbubble ultrasonic contrast to tumor therapy, Ultrasound Med. Biol. 19 (1993) 123-125. 

A detailed knowledge of the predominant physicochemical/biochemical mechanism by which gas microbubbles are stabilized in aqueous media is of practical importance to numerous and varied fields acoustic and hydrodynamic cavitation, commercial oil recovery, hydraulic and ocean engineering, waste-water treatment, chemical oceanography, meteorology, marine biology, food technology, echocardiography, and the continual medical problem of decompression sickness. Many of these applications... 

Lindner JR (2004) Microbubbles in medical imaging current applications and future directions. Nat Rev Drug Discov 3 527-532... 

The application of ultrasound has also been investigated in an attempt to improve in vivo transgene expression, and this facilitated nonendocytotic uptake of plasmid DNA into cells.101 Recently, the combined use of microbubbles was found to be effective in increasing ultrasound-mediated gene transfer. So far, ultrasound-mediated gene transfer has been carried out in vascular cells102 103 and heart muscle.104... 

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