Tandem Shock Waves Research Articles

Underwater Shock Wave-Enhanced Cavitation to Induce Morphological Changes and Cell Permeabilization in Microscopic Fungi

Since the discovery of extracorporeal lithotripsy, there has been an increased interest in studying shock wave-induced cavitation, both to improve this technique and to explore novel biotechnological applications. As shock waves propagate through fluids, pre-existing microbubbles undergo expansion and collapse, emitting high-speed microjets. These microjets play a crucial role in the pulverization of urinary stones during lithotripsy and have been utilized in the delivery of drugs and genetic materials into cells. Their intensity can be amplified using tandem shock waves, generated so that the second wave reaches the bubbles, expanded by the first wave, during their collapse. Nevertheless, there is little information regarding the control of microjet emissions. This study aimed to demonstrate that specific effects can be obtained by tuning the delay between the first and second shock waves. Suspensions containing Aspergillus niger, a microscopic fungus that produces metabolites with high commercial value, were exposed to single-pulse and tandem shock waves. Morphological changes were analyzed by scanning and transmission electron microscopy. Proteins released into the medium after shock wave exposure were also studied. Our findings suggest that, with enhanced control over cavitation, the detachment of proteins using conventional methods could be significantly optimized in future studies.

Weak shock wave-mediated fucoxanthin extraction from Sargassum spp. and its electrochemical quantification

Fucoxanthin, a carotenoid found in Sargassum spp., possesses essential applications in the food and pharmaceutical industries. However, conventional methods for extracting fucoxanthin suffer from substantial limitations. This study demonstrates that shock wave-induced cavitation can be an efficient and selective extraction method. Suspensions of 100 mg of dried powdered algae with 4 mL of solvent (80 % ethanol) were exposed to four extraction methods at 25 and 50 °C. Four thousand single-pulse shock waves (SP-SWs) and two thousand dual-pulse shock waves, i.e., tandem shock waves (T-SWs), with a positive peak pressure of approximately 70 MPa, were compared with exposure for 30 min to a 40 kHz, 160 W-ultrasound bath (USE-B) and 5 min sonotrode extraction (USE-S) at maximum energy. A differential pulse voltammetry method for quantifying fucoxanthin was used for the first time, demonstrating that it is as fast and precise as other highly sensitive techniques. Independent of the extraction method, higher fucoxanthin content was obtained at 50 °C. At both temperatures, the total phenolic and flavonoid content values recorded after USE-S and T-SWs (delay ~220 μs) extraction were significantly smaller than those achieved for USE-B and SP-SWs. At 50 °C, the fucoxanthin content obtained was lower for the USE-S and T-SWs, opening the possibility of selective extraction. Moreover, this is the first time that the fucoxanthin content of Sargassum spp. from the Mexican Caribbean coast has been reported.

Effect of Shock Waves on the Growth of Aspergillus niger Conidia: Evaluation of Germination and Preliminary Study on Gene Expression.

Shock waves, as used in medicine, can induce cell permeabilization, genetically transforming filamentous fungi; however, little is known on the interaction of shock waves with the cell wall. Because of this, the selection of parameters has been empirical. We studied the influence of shock waves on the germination of Aspergillus niger, to understand their effect on the modulation of four genes related to the growth of conidia. Parameters were varied in the range reported in protocols for genetic transformation. Vials containing conidia in suspension were exposed to either 50, 100 or 200 single-pulse or tandem shock waves, with different peak pressures (approximately 42, 66 and 83 MPa). In the tandem mode, three delays were tested. To equalize the total energy, the number of tandem "events" was halved compared to the number of single-pulse shock waves. Our results demonstrate that shock waves do not generate severe cellular effects on the viability and germination of A. niger conidia. Nevertheless, increase in the aggressiveness of the treatment induced a modification in four tested genes. Scanning electron microscopy revealed significant changes to the cell wall of the conidia. Under optimized conditions, shock waves could be used for several biotechnological applications, surpassing conventional techniques.

Kriging model to study the dynamics of a bubble subjected to tandem shock waves as used in biomedical applications

The purpose of this work was to develop a metamodel (Kriging model) to identify the most important input parameters of shock wave pressure profiles as used in biomedical applications without solving a large number of differential equations. Shock wave-induced cavitation is involved in several biological effects. During bubble collapse, secondary shock waves and microjets are formed. For some applications, it is desirable to enhance this phenomenon by applying a second shock wave before bubble collapse; however, the delay between the leading shock wave and the second pressure pulse has yet to be optimized. This optimization can be done using numerical analysis. A metamodel that predicts the most convenient ranges for the input variables and provides information on the joint effects between the input variables was tested. Because the metamodel is an analytical expression, running it fifty thousand times and analyzing variables, such as the pressure amplitude, delay between pulses, and pressure rise time, was fast and easy. Furthermore, this method can be a helpful tool to study the joint effect between the input variables and reduce the computation time. The metamodel can also be adapted to analyze simulations based on equations different from the Gilmore-Akulichev formulation, which was used in this study.

Tandem shock waves in medicine and biology: a review of potential applications and successes

Shock waves have been established as a safe and effective treatment for a wide range of diseases. Research groups worldwide are working on improving shock wave technology and developing new applications of shock waves to medicine and biology. The passage of a shock wave through soft tissue, fluids, and suspensions containing cells may result in acoustic cavitation i.e., the expansion and violent collapse of microbubbles, which generates secondary shock waves and the emission of microjets of fluid. Cavitation has been recognized as a significant phenomenon that produces both desirable and undesirable biomedical effects. Several studies have shown that cavitation can be controlled by emitting two shock waves that can be delayed by tenths or hundreds of microseconds. These dual-pulse pressure pulses, which are known as tandem shock waves, have been shown to enhance in vitro and in vivo urinary stone fragmentation, cause significant cytotoxic effects in tumor cells, delay tumor growth, enhance the bactericidal effect of shock waves and significantly increase the efficiency of genetic transformations in bacteria and fungi. This article provides an overview of the basic physical principles, methodologies, achievements and potential uses of tandem shock waves to improve biomedical applications.

Combined short and long-delay tandem shock waves to improve shock wave lithotripsy according to the Gilmore–Akulichev theory

Extracorporeal shock wave lithotripsy is a common non-invasive treatment for urinary stones whose fragmentation is achieved mainly by acoustic cavitation and mechanical stress. A few years ago, in vitro and in vivo experimentation demonstrated that such fragmentation can be improved, without increasing tissue damage, by sending a second shock wave hundreds of microseconds after the previous wave. Later, numerical simulations revealed that if the second pulse had a longer full width at half maximum than a standard shock wave, cavitation could be enhanced significantly. On the other side, a theoretical study showed that stress inside the stone can be increased if two lithotripter shock waves hit the stone with a delay of only 20μs. We used the Gilmore–Akulichev formulation to show that, in principle, both effects can be combined, that is, stress and cavitation could be increased using a pressure pulse with long full width at half maximum, which reaches the stone within hundreds of microseconds after two 20μs-delayed initial shock waves. Implementing the suggested pressure profile into clinical devices could be feasible, especially with piezoelectric shock wave sources.

Tandem shock waves to enhance genetic transformation of Aspergillus niger

Filamentous fungi are used in several industries and in academia to produce antibiotics, metabolites, proteins and pharmaceutical compounds. The development of valuable strains usually requires the insertion of recombinant deoxyribonucleic acid; however, the protocols to transfer DNA to fungal cells are highly inefficient. Recently, underwater shock waves were successfully used to genetically transform filamentous fungi. The purpose of this research was to demonstrate that the efficiency of transformation can be improved significantly by enhancing acoustic cavitation using tandem (dual-pulse) shock waves. Results revealed that tandem pressure pulses, generated at a delay of 300μs, increased the transformation efficiency of Aspergillus niger up to 84% in comparison with conventional (single-pulse) shock waves. This methodology may also be useful to obtain new strains required in basic research and biotechnology.

Focused tandem shock waves in water and their potential application in cancer treatment

Extracorporeal shock wave lithotripsy (ESWL) has been successful for more than 30 years in non-invasive treating patients with stone deceases (mostly kidney stones). ESWL devices (lithotripters) generate shock waves outside the patient’s body and concentrate them on the kidney stone. Over 40 models of lithotripter (electrohydraulic, piezoelectric and electromagnetic) are commercially available worldwide [1],[2]. At the end of 1980’s one of modified versions of electrohydraulic type of lithotriptor was developed also in the Institute of Plasma Physics AS CR [3]-[5]. Such generators serve up to now as a therapeutic unit in the lithotripters Medilit (produced by the company MEDIPO, Brno, Czech Republic) at about 20 hospitals in the Czech and Slovak Republic [6]. So far more than 120 thousands patients have been successfully treated by these devices.

Biological effects of tandem shock waves demonstrated on magnetic resonance

The shock wave is used for the treatment of kidney stones, eventually of gall stones, for more than 20 years. It is a pressure wave, which breaks through soft tissues easily and it is possible to focus it into a small volume. The excellent results of the treatment of concrements led to considerations about another usage of the shock wave. The research is now concentrated on the possibility of the damage to tumour tissues. In contrast to concrements tumour tissues are not different from healthy tissues as for their acoustic attributes. That is why a new source of shock waves was used in this work. The source allows generating two successive shock waves focused into a common focus, so-called tandem shock waves. The biological effects of the tandem shock waves generated by the new source on rats hepatic tissue and rabbit femoral muscle in vivo were studied in this work. The damage is demonstrated by magnetic resonance imaging. MR images showed tissue damage in focus. There was damage of the liver tissue, muscle and also stomach wall. We found that the tandem shock waves are able to damage the acoustically homogeneous soft tissue in the focus, i.e. in the depth. In tissues in front of the focus, there is, however, no damage (Fig. 10, Ref. 15).

Modified shock waves for extracorporeal shock wave lithotripsy: A simulation based on the Gilmore formulation

Extracorporeal shock wave lithotripsy (SWL) is a reliable therapy for the treatment of urolithiasis. Nevertheless, improvements to enhance stone fragmentation and reduce tissue damage are still needed. During SWL, cavitation is one of the most important stone fragmentation mechanisms. Bubbles with a diameter between about 7 and 55 μm have been reported to expand and collapse after shock wave passage, forming liquid microjets at velocities of up to 400 m/s that contribute to the pulverization of renal calculi. Several authors have reported that the fragmentation efficiency may be improved by using tandem shock waves. Tandem SWL is based on the fact that the collapse of a bubble can be intensified if a second shock wave arrives tenths or even a few hundredths of microseconds before its collapse. The object of this study is to determine if tandem pulses consisting of a conventional shock wave (estimated rise time between 1 and 20 ns), followed by a slower second pressure profile (0.8 μs rise time), have advantages over conventional tandem SWL. The Gilmore equation was used to simulate the influence of the modified pressure field on the dynamics of a single bubble immersed in water and compare the results with the behavior of the same bubble subjected to tandem shock waves. The influence of the delay between pulses on the dynamics of the collapsing bubble was also studied for both conventional and modified tandem waves. For a bubble of 0.07 mm, our results indicate that the modified pressure profile enhances cavitation compared to conventional tandem waves at a wide range of delays (10–280 μs). According to this, the proposed pressure profile could be more efficient for SWL than conventional tandem shock waves. Similar results were obtained for a ten times smaller bubble.

Enhanced Shock Wave-Assisted Transformation of Escherichia coli

The objective of the study was to demonstrate that shock wave-induced transfer of DNA into bacteria can be increased by enhancing cavitation using dual-pulse (tandem) shock waves. Escherichia coli and plasmid were transferred to test vials. Competent cells were prepared at different concentrations of CaCl 2. Single pulses and tandem shock waves were compared as were three treatment temperatures: 0, 10 and 25°C. Three delays (250, 500, 750 μs) between double pulses were tested. Characterization was achieved by using a plasmid that provided green fluorescent protein expression. At 0°C double pulses generated at a delay of 750 μs significantly increased the number of fluorescent colonies compared with single pulses. In general, the lowest temperature enhanced the mean number of transformants compared with the two higher temperatures. A strong influence of the CaCl 2 concentration on the transformation efficiency was also found. The main conclusion is that gene transfer to target cells may be increased up to 50 times at 0°C by enhancing cavitation using pairs of shock waves. (E-mail: loske@fata.unam.mx)

Treatment Time Reduction Using Tandem Shockwaves for Lithotripsy: AnIn VivoStudy

Reducing extracorporeal shockwave lithotripsy (SWL) time by increasing the shockwave rate of the lithotripter has been tested in the past; however, basic research and treatment outcomes revealed that this is not convenient. The purpose of this study was to use an animal model to demonstrate that SWL treatment time can be reduced significantly without sacrificing stone fragmentation efficiency using tandem shockwaves. A tandem research lithotripter was used to treat 50 artificial kidney stones implanted into the kidneys of 50 rabbits. Standard single-pulse and tandem shockwaves were compared in two different scenarios: Without a fluid-filled expansion chamber and with a fluid-filled expansion chamber surrounding the stone. The presence of fluid surrounding the stone enhances fragmentation in both the standard and tandem modes. No significant difference in fragmentation efficiency was recorded between the standard and tandem SWL with stones surrounded by fluid; however, the treatment time with tandem shockwaves was reduced by 50%. Significantly shorter SWL treatments may be possible in the future using tandem shockwaves on urinary stones that are surrounded by fluid.

The Importance of an Expansion Chamber During Standard and Tandem Extracorporeal Shock Wave Lithotripsy

It is known that extracorporeal shock wave lithotripsy (SWL) may be improved by increasing cavitation using tandem shock waves. However, fluid is needed for the cavitation to work. The purpose of this research was to evaluate the importance of a fluid-filled expansion chamber in enhancing stone fragmentation during standard and tandem SWL. A piezoelectric lithotripter was modified to generate tandem shock waves. Artificial kidney stones inserted in vitro into the parenchyma of a pig kidney were exposed to either standard or tandem shock waves. Stones in one group were placed inside a small finger cot filled with water before they were introduced into the kidney. Stone fragments were strained through a mesh, dried, and weighed. Water surrounding the stones always improved stone fragmentation. The best results were achieved using tandem shock waves at a delay of 250 micros. A fluid-filled chamber surrounding the stone is essential for good SWL outcome. Tandem shock waves are more efficient than standard shock waves only if the stone is surrounded by fluid.

Short‐ and long‐delay tandem shock waves for application in medicine

Long‐delay tandem shock waves with an inter‐pulse delay between about 200 and 500 microseconds have shown to enhance fragmentation of artificial kidney stones during in vitro and in vivo extracorporeal shock wave lithotripsy (SWL) in the past. Cell‐permeabilization and inactivation of bacteria using tandem shock waves have also been proposed. The purpose of this research was to study the influence of short‐delay (less than 50 microseconds) tandem shock waves on cavitation induced damage to kidney stones during SWL. A multipurpose piezoelectric shock wave generator was designed to generate shock waves at variable delays. The effect of short‐ and long‐delay dual‐pulse shock waves on the surface of artificial kidney stones was evaluated by microscopy. An adequate selection of delays was possible by means of a numerical model and high speed photography. Stone fragmentation was compared to that of standard (single‐pulse) shock waves. Our results indicate that specific combinations of short‐ and long‐delay tand...

The influence of single-pulse and tandem shock waves on bacteria

Tandem shock waves have shown to enhance kidney stone fragmentation during in vitro and in vivo extracorporeal shock wave lithotripsy (SWL). The purpose of this research was to study the influence of shock waves on the viability of two strains of bacteria in solution, and to verify if tandem shock waves increase microorganism death. A piezoelectric shock wave generator was modified to generate either standard (single-pulse) or tandem (dual-pulse) shock waves. E. coli and Listeria monocytogenes were exposed in vitro to thousands of standard shock waves. Another group was subjected to the same number of tandem shock waves with a delay of 450 μs. A third group was exposed to tandem shock waves having a 900-μs delay. No inactivation was observed for both microorganisms at up to 8,000 standard shock waves. About 40% of L. monocytogenes and 50% of E. coli were inactivated after treatment with tandem waves at a delay of 900 μs. Inactivation was less efficient for a delay of 400 μs. Our results could be useful in medicine, because infection stones are still a significant cause of morbidity and mortality after SWL. The use of tandem shock waves to treat persistent localized infections or as a novel non-thermal food-preservation method also might be possible.

Enhanced Kidney Stone Fragmentation by Short Delay Tandem Conventional and Modified Lithotriptor Shock Waves: A Numerical Analysis

We evaluated the effectiveness of modified lithotriptor shock waves using computer models. Finite element models were used to simulate the propagation of lithotriptor shock waves in human renal calculi in vivo. Kidney stones were assumed to be spherical, homogeneous, isotropic and linearly elastic, and immersed in a continuum fluid. Single and tandem shock wave pulses modified to intensify the collapse of cavitation bubbles near the stone surface to increase fragmentation efficiency and suppress the expansion of intraluminal bubbles for decreased vascular injury were analyzed. The effectiveness of the modified shock waves was assessed by comparing the states of loading in the renal calculi induced by these shock waves to those produced by conventional shock waves. Our numerical simulations revealed that modified shock waves produced marginally lower stresses in spherical renal calculi than those produced by conventional shock waves. Tandem pulses of conventional or modified shock waves produced peak stresses in the front and back halves of the renal calculi. However, the single shock wave pulses generated significant peak stresses in only the back halves of the renal calculi. Our numerical simulations suggest that for direct stress wave induced fragmentation modified shock waves should be as effective as conventional shock waves for fragmenting kidney stones. Also, with a small interval of 20 microseconds between the pulses tandem pulse lithotripsy using modified or conventional shock waves could be considerably more effective than single pulse lithotripsy for fragmenting kidney stones.

Steigerung der Fragmentationseffizienz durch Verstärkung von Kavitation zur berührungsfreien Nierensteinzertrümmerung

The non-invasive disintegration of kidney stones using shock waves, referred to as extracorporal shock wave lithotripsy, has been successful for more than twenty years in treating patients having renal and ureteral stones. Two modified shock wave generators are described in this article. The novel systems produce two similar shock waves (tandem shock waves) generated with a short time delay. The second shock wave arrives during collapse of the bubbles generated in the neighborhood of the stone due to the first shock wave. This may increase cavitation bubble collapse and could enhance cavitation-induced damage to kidney stones during shock wave lithotripsy. In vitro comparison of standard systems with the new designs showed that fragmentation efficiency of artificial kidney stones was significantly enhanced using tandem shock waves.

CONTROLLED, FORCED COLLAPSE OF CAVITATION BUBBLES FOR IMPROVED STONE FRAGMENTATION DURING SHOCK WAVE LITHOTRIPSY

The feasibility of using controlled, forced collapse of cavitation bubbles for improved stone fragmentation during shock wave lithotripsy was demonstrated using microsecond tandem shockwave pulses. High-speed photography revealed that a secondary shock wave, released in less than 500 microseconds (micro sec.) following a lithotripter-generated shock wave, can be used to control and force the collapse of cavitation bubbles toward target concretions. This timely enforced shockwave-bubble interaction was found to greatly enhance the cavitational activity near the stone surface, with a resultant up to 43% increment in stone fragmentation. Since most of the cavitation energy is directed and concentrated toward the target stones and fewer shock waves are needed for successful stone comminution, tissue injury associated with this new lithotripsy procedure may also be reduced. This novel concept of shock wave lithotripsy may be used to improve the treatment efficiency and safely of existing clinical lithotripters, as well as in the design of new shock wave lithotripters.

Environmental fatigue of an AlLiCu alloy. II. Microscopic cracking processes: Piascik, R.S. and Gangloff, R.P. Metal. Trans. A (Dec. 1993)24A (12), 2751–2762

Filamentous fungi are used in several industries and in academia to produce antibiotics, metabolites, proteins and pharmaceutical compounds. The development of valuable strains usually requires the insertion of recombinant deoxyribonucleic acid; however, the protocols to transfer DNA to fungal cells are highly inefficient. Recently, underwater shock waves were successfully used to genetically transform filamentous fungi. The purpose of this research was to demonstrate that the efficiency of transformation can be improved significantly by enhancing acoustic cavitation using tandem (dual-pulse) shock waves. Results revealed that tandem pressure pulses, generated at a delay of 300 μs, increased the transformation efficiency of Aspergillus niger up to 84% in comparison with conventional (single-pulse) shock waves. This methodology may also be useful to obtain new strains required in basic research and biotechnology.