Ultrasound synergistic effects

The study of electrosynthetic reactions is not a new phenomenon. Such reactions have been the study of investigation for more than a century and a half since Faraday first noted the evolution of ethane from the electrolysis of aqueous acetate solutions. This reaction is more well known as the Kolbe electrolysis [51]. Since the report of Kolbe, chemists have had to wait nearly a century until the development, in the 1960 s, of organic solvents with high-dielectric which have been able to vastly increase the scope of systems that could be studied [52]. Added to this more recently is the synergistic effect that ultrasound should be able to offer in the improvement of the expected reactions by virtue of its ability to clean of surfaces, form fresh surfaces and improve mass transport (which may involve different kinetic and thermodynamic requirements)... 

The use of skin permeation enhancers in combination for synergistic effects has been studied in the transdermal literature (70). Such synergistic methods can be grouped in three categories (i) combination of two physical methods, e.g., ultrasound and iontophoresis (71-75) (ii) combination of a physical method with a chemical enhancer, e.g., use of ultrasound with sodium lauryl sulfate or isopropyl myristate (76-80) and (iii) combination of two chemicals, e.g., terpenes and propylene glycol (46,81-88). Numerous studies have been published on using combination of two physical methods or use of a physical method in conjunction with a chemical enhancer. Use of a physical method, by itself or in combination with another physical method, increases application cost for delivery purposes as mentioned before. In addition, there are unexplored safety and membrane recovery issues associated with these methods. A few reports have also been published on the use of a mixture of chemical enhancers for enhancing transdermal delivery. Typically, such studies use... 

Tezel A, Sens A, Tuchscherer J, Mitragotri S. Synergistic effect of low-frequency ultrasound and surfactants on skin permeability. J Pharm Sci 2002 91 91-100. 

A recent work by Lavon et al. [74] suggests that the synergistic effect of SLS and ultrasound when applied simultaneously can also be attributed to the modification of the stratum corneum pH profile when exposed to ultrasound. The altered pH profile that results in improved SLS lipophylic solubility, together with improved SLS penetration and dispersion, can explain the synergistic enhancing effect on transdermal transport (see Figure 16.4). 

Ultrasound also exhibited a synergistic effect with electroporation [72], Ultrasound reduced the threshold voltage for electroporation as well as increased transdermal transport at a given electroporation voltage. The enhancement of transdermal transport induced by the combination of ultrasound and electroporation was higher than the sum of the enhancement induced by each enhancer alone. 

FIGURE 16.4 Schematic presentation of ultrasound/SLS synergistic effect on skin permeability. (From Lavon, I., Grossman, N., and Kost, J., J. Control. Release, 107, 484, 2005. With permission.)... 

Johnson, M.E., et al. 1996. Synergistic effects of chemical enhancers and therapeutic ultrasound on transdermal drug delivery. J Pharm Sci 85 670. 

In connection with the antioxidant properties of L-ascorbic acid and its stability, many kinetic and mechanistic studies have been performed. For instance, it has been shown a role as a radical scavenger in the autooxidation of methyl linoleate, and its synergistic effect when used with vitamin E.362 The photooxidation,363 superoxide-mediated oxidations,364 reactions with radicals,365 and the influence of other agents, including ultrasound and y-rays,366 have been reported. 

Synergistic effects of ultrasound and other auxiliary energies on strong digestion... 

Ultrasound may enhance transdermal transport by inducing skin alteration and active transport (forced convention) in the skin. Various other means of transport enhancement, including chemicals, iontophoresis and electroporation, may enhance transport synergis-tically with US. Thus, the evaluation of the synergistic effect of low-frequency US with chemical enhancers and surfactants for permeation of mannitol revealed that application of US or sodium lauryl sulfate (SLS) alone, both for 90 min, increased skin permeability about 8 and 3 times, respectively. However, the combined use of US and a 1% SLS solution increased the skin permeability 200 times to mannitol [129]. 

Lopez et al. [120] stndied the inactivation of three food quality enzymes—peroxidase, PPO, and lipoxygenase— by MTS. They revealed that a synergistic effect of temperatnre, pressure, and ultrasound results in rednced enzyme resistance and heat treatment for inactivation. Ultrasonic wave amplitude was found to be more effective on enzyme destruction than static pressure at constant temperature. This combined treatment was reported to be very useful in solving problems caused by thermostable enzymes. 

Kost, J., Pliquett, U., Mitragotri, S., Yamamoto, A., Langer, R., and Weaver, J. 1996. Synergistic effect of electric field and ultrasound on transdermal transport. Pharmaceutical Research, 13, 633-638. 

I. Rosenthal, J.Z. Sostaric, P. Riesz, Sonodynamic therapy—a review of the synergistic effects of drugs and ultrasound. Ultrson. Sonochem. 11, 349-363 (2004)... 

Yamaguchi Sh., Kobayashi, FI., Narita, T., Kanehira, K., Sonezaki Sh., Kudo, N., Kubota Yo., Terasaka Sh., Houkin, K. Sonodynamic therapy using water-dispersed TiOj polyethylene glycol compound on glioma cells Comparison of cytotoxic mechanism with photodynamic therapy. Ultrasonics Sonochemistry, 2011,18,1197-1204. Rosenthal, I., Sostaric, J.Z., Riesz, P. Sonodynamic therapya review of the synergistic effects of drugs and ultrasound. Ultrasonics Sonochemistry, 2004,11(6), 349-363. 

Well-defined flower-like CdS nanostructures have been synthesized by Tai and Guo (2008) under ultrasound and microwave irradiations, simultaneously. Hexagonal nanopyramids and/or nanoplates were obtained depending on different sulfur sources. The synergistic effect of microwave and sonochemistiy has been proposed for the formation of these nanoflowers. They show a large bine-shift npto 100 nm as compared to simple low-dimensional CdS nanostmctnres. This stmctnre induced shift in optical properties, which may find some potential applications in optoelectronics devices, catalysis, and solar cells. 

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