Sonochemical Mechanism Research Articles

Simultaneous H/D and 13C/12C Anomalous Kinetic Isotope Effects during the Sonolysis of Water in the Presence of Carbon Monoxide.

Splitting of water molecules driven by ultrasound plays a central role in sonochemistry. While studies of sonoluminescence revealed the formation of a plasma inside the cavitation bubble, much less is known about the contribution of plasma chemical processes to the sonochemical mechanisms. Herein, we report for the first time sonochemical processes in water saturated with pure CO. The presence of CO causes a large increase in the H/D kinetic isotope effect (KIE) to αH = 14.6 ± 1.8 in a 10% H2O/D2O mixture under 20 kHz ultrasound. The anomalous H/D KIE is attributed to electron quantum tunneling in the plasma produced by cavitation. In addition, CO2 formed simultaneously with hydrogen during the sonochemical process is enriched with the 13C isotope, which indicates a V-V pumping mechanism typical for non-equilibrium plasma. Both observed KIEs unambiguously point to the contribution of quantum effects in sonochemical mechanisms.

Sonoluminescence in solutions of organic aromatic luminophores: Monomer and excimer luminescence of benzene, toluene and p-xylene

This paper considers the spectra of glow that emerges during the sonolysis of benzene, toluene and p-xylene solutions in ethylene glycol under the action of a translationally motionless bubble levitating in the ultrasonic standing wave with a frequency of ~27 kHz or a moving bubble (single-bubble, or moving single-bubble sonoluminescence, SBSL, or m-SBSL, respectively). The m-SBSL spectra against the background of the broadband solvent continuum demonstrate the presence of characteristic luminescence bands of luminophores in the range of 270–305 nm (singlet excited monomers) and a band of singlet excited dimers (excimers) of these molecules with a maximum of 320 nm at a luminophores concentration in solution being 10−3-10−2 M. For 1.25∙10−3 M benzene solution, there were also recorded the bands of СН and С2 radicals occurred as a result of decomposing this luminophore. At concentrations higher than 10−2 M, luminophores luminescence is quenched and the m-SBSL spectra reveal only the continuum, the intensity of which also decreases with an increase in the luminophores concentration. This continuum is recorded without any significant change in its shape and intensity, with no bands of luminophores and radicals for the luminophores concentrations specified, and during SBSL. The obtained data are indicative of the penetration of luminophores molecules, in the m-SBSL regime, from the solution into the moving and deformed bubble according to the known sonochemical mechanism to inject solution nanodroplets and also their further collisional excitation in the nonequilibrium intrabubble plasma which repeatedly formed during oscillations of bubble in the acoustic field. The nonequilibrium plasma state determines the presence of luminescence both luminophore molecules (gas temperature about 103 K or less) and radical products of their decomposition (gas temperature is thousands K).

Graphene Quantum Dots with Pyrrole N and Pyridine N: Superior Reactive Oxygen Species Generation Efficiency for Metal-Free Sonodynamic Tumor Therapy.

Those responsible for the development of sonosensitizers are faced with a dilemma between high sonosensitization efficacy and good biosecurity that limited the development of sonodynamic therapy (SDT). Herein, inspired by the intriguing therapeutic features of SDT and the potential catalytic activity of graphene quantum dots, the potential of N-doped graphene quantum dots (N-GQDs) to act as a sonosensitizer is demonstrated. The superior sonosensitization effect of N-GQDs is believed to be three to five times higher than that of traditional sonosensitizers (such as porphyrin, porphyrin Mn, porphyrin Zn, TiO2 , etc.). More importantly, the sonochemical mechanism of N-GQDs is revealed. Pyrrole N and pyridine N are believed to form catalytic centers in sonochemical processing of N-GQDs. This knowledge is important from the perspective of understanding the structure-dependent SDT enhancement of carbon nanostructure. Moreover, N-GQDs modified by folic acid (FA-N-GQDs) show a high marker rate for tumor cells (greater than 96%). Both in vitro and in vivo therapeutic results have exhibited high tumor inhibition efficiency (greater than 90%) of FA-N-GQDs as sonosensitizers while the oxidative stress response of tumor cells is activated through the PEX pathway and induced apoptosis via the p53 pathway.

Ultrasonic Formation of Copper/Iron Graphene Oxide for Ketorolac Delivery

New accessible sonochemical methods were developed for the functionalization of synthesized graphene oxide (GO) with copper/iron compounds and drug intercalation into their structure in aqueous solution at ambient conditions by using ultrasound (20[Formula: see text]kHz) treatment. The sonochemical formation mechanism of a new nanomaterial was revealed through the structural analysis of three types of nanocomposites: (i) copper@graphene oxide, (ii) copper/iron@graphene oxide and (iii) iron@graphene oxide. Unique copper/iron-modified graphene oxide nanocomposites can be used as nanocarriers for the anti-inflammatory drug (ketorolac) delivery in aqueous solution due to the reduced submicron size and enlarged surface area. Disintegration of the ultrasonically intercalated ketorolac followed the exponential decay curve fit at higher pH values of the aqueous solution with a higher decay constant observed in copper/iron-modified graphene oxide nanocomposites.

Sonodynamic antitumor effect of a novel sonosensitizer on S180 solid tumor

The purpose of this study was to evaluate the sonodynamically induced antitumor effect of a novel sonosensitizer (DVDMS) in mice bearing sarcoma 180 solid tumors. In order to determine the optimum timing of ultrasound exposure after administration of DVDMS, a three-dimensional optical imaging system (IVIS spectrum) was used to observe the biodistribution of DVDMS in S180 tumor. The antitumor effects were estimated by the tumor inhibition ratio (volume and weight) after sonodynamic therapy. The experiments suggested that DVDMS has a preferential localization in tumors, but a low accumulation in most normal tissues. A significant synergistic effect of ultrasound combined with DVDMS was obtained when the load power indicated 4 W and DVDMS dose was above 2 mg/kg. At day 14 after DVDMS-SDT, the tumor volume inhibition ratio was 56.27%. In addition, the tumor weight inhibition ratio after the synergistic treatment was 55.37%, which was obviously stronger than ultrasound treatment alone (23.85%) and DVDMS alone (23.15%). Moreover, no metastasis occurred to the tumors in the SDT-treated mice compared with the control group. DVDMS is a potential sensitizer for sonodynamic cancer therapy. The antitumor effect of ultrasound could be enhanced in the presence of DVDMS, which might be involved in a sonochemical mechanism.

ChemInform Abstract: Harnessing Mechanochemical Effects with Ultrasound‐Induced Reactions

AbstractReview: 90 refs.

Harnessing mechanochemical effects with ultrasound-induced reactions

Chemical reactions may experience numerous and varied effects under the influence of ultrasound. This soft radiation, often viewed as a lab trick, induces and improves both physical and chemical transformations by means of efficient agitation, dissolution, mass and heat transfers, and reagents sonolysis, which all arise from the cavitational collapse. An empirical rationale that distinguishes between true chemical effects and mechanical ones, especially in heterogeneous reactions, was introduced more than two decades ago and has been a useful guidance on reporting sonochemical mechanisms. Recent studies have witnessed a truly remarkable data set that boosts sonochemistry over the wall of applied science. This perspective highlights the importance of the so-called false sonochemistry-closely related to mechanochemistry-in modern synthesis, thus illustrating the advantages of using pressure waves in chemistry. Emphasis is put on green transformations, mild polymerization reactions and the selective cleavage of functionalized polymers, which may have an effective impact in process chemistry and represent a realistic option in industry.

Pharmacokinetic study of a novel sonosensitizer chlorin‐e6 and its sonodynamic anti‐cancer activity in hepatoma‐22 tumor‐bearing mice

The sonodynamically induced anti-tumor effect of chlorin-e6 (Ce6) was studied in mice bearing hepatoma-22 solid tumors. In order to determine the optimum timing of ultrasound exposure after administration of Ce6, the Ce6 concentrations in plasma, skin, muscle and tumor were estimated by measuring the fluorescence intensity of tissue extractions with a fluorescence photometer based on the standard curve. A three-dimensional optical imaging system (IVIS spectrum) was used further to characterize the distribution of Ce6 in H-22 tumor. The anti-tumor effects were estimated by measuring tumor size after sonodynamic therapy. Similar pharmacokinetic trends of Ce6 in mice were observed either by fluorescence spectrophotometry or by bio-optical imaging. The results also demonstrated that Ce6 has a preferential localization in tumors, but low accumulation and rapid clearance in normal tissues. The results of anti-tumor effects revealed that at an ultrasound intensity of 4 W/cm(2) and a Ce6 dose of ≥10 mg/kg, a significant synergistic effect of ultrasound combined with Ce6 was observed, reducing the tumor volume significantly. Chlorin-e6 is a potential sonosensitizer for fluorescence imaging as well as for sonodynamic therapy for cancer. The anti-tumor effect of ultrasound could be enhanced in the presence of Ce6, which might be involved in a sonochemical mechanism.

Acceleration of ultrasonic tissue heating by microbubble agent

Ultrasound in the existence of microbubbles, whether they have been generated by acoustic cavitation or administered into the body, is known to induce bioeffects normally through mechanical or sonochemical mechanisms. Recently, it is reported that ultrasonic tissue heating can be accelerated several times by an administered microbubble agent. A microbubble, subjected to ultrasonic pressurein the frequency range of its resonanance converts the acoustic energy to heat through its volume oscillation. The acoustic power converted to heat by a microbubble through viscous heating was numerically calculated, and it was predicted that tissue ultrasonic absorption would be doubled if a microbubble agent is delivered to the tissue at a concentration in the order of 100 microbubbles /mg. Exteriorized murine kidneys were exposed to focused ultrasound at 3.2 MHz in degassed saline and the tissue temperature change was measured. Optison at a dose of 0.2 ml /kg multiplied the temperature elevation induced by ultrasonic exposure by several times. In order to use this effect to treat a deep-seated tumor, microbubbles should be somehow delivered to the tumor selectively. A novel method of selective delivery, in which nano liquid particles are administered and converted into microbubbles by ultrasonic stimulation, will also be discussed.

Sonodynamic Antitumor Effect of Protoporphyrin IX Disodium Salt on S180 Solid Tumor

Background: The sonodynamically induced antitumor effect of protoporphyrin IX (PPIX) disodium salt was studied in mice bearing sarcoma 180 solid tumors. Methods: In order to determine the optimum timing of ultrasound exposure after administration of PPIX, the PPIX concentrations in plasma, skin, muscle and tumor were estimated by measuring the fluorescence intensity of tissue extractions with a fluorescence photometer based on the standard curve. Antitumor effects were estimated by measuring tumor size and calculating the average survival time of tumor-bearing mice after sonodynamic therapy; additionally, the morphological changes of sarcoma 180 cells were evaluated by transmission electron microscope observation in vivo. Results: Our experiments suggested a time of 24 h after the administration of PPIX to be best for ultrasound exposure. At an ultrasound intensity ≧5 W/cm² and a PPIX dose ≧5 mg/kg, a significant synergistic effect of ultrasound combined with PPIX was observed, reducing tumor volume and increasing average animal survival time; this synergistic effect was obviously stronger than ultrasound treatment alone, while PPIX alone showed no significant effect. Transmission electron microscope observation indicated that changes in cell ultrastructure, such as cell membrane destruction, mitochondria swelling and chromatin condensation, were important factors that inhibited tumor growth and even induced cell death. Conclusion: The results implied that the antitumor effect of ultrasound could be enhanced in the presence of PPIX which might be involved in a sonochemical mechanism.

Sonodynamic effects of protoporphyrin IX disodium salt on isolated sarcoma 180 cells

The cytotoxic effect of PPIX on isolated sarcoma 180 cells induced by ultrasound was investigated. Tumor cells suspended in air-saturated PBS (pH 7.2) were exposed to ultrasound at 2.2MHz for up to 60s in the presence and absence of protoporphyrin IX disodium salt (PPIX). The viability of cells was determined by a trypan blue exclusion test. The rate of ultrasonically induced cell damage was increased with 40–160μM PPIX, while no cell damage was observed with 160μM PPIX alone. This enhancement of cell damage with PPIX was inhibited by histidine. The participation of lipid peroxidation products in the cell damage process was also investigated. Scanning electron microscope (SEM) observation of the surface of cells was performed to evaluate the morphological changes induced by ultrasonic irradiation. The results indicate the involvement of a sonochemical mechanism.

Comparison between sonodynamic effect and photodynamic effect with photosensitizers on free radical formation and cell killing

Although enhancement of ultrasound-induced cell killing by photodynamic reagents has been shown, the sonochemical mechanism in detail is still not clear. Here, comparison between sonodynamic effect and photodynamic effect with photosensitizers at a concentration of 10 μM on free radical formation and cell killing was made. When electron paramagnetic-resonance spectroscopy (EPR) was used to detect 2,2,6,6-tetramethyl-4-piperidone- N-oxyl (TAN) after photo-irradiation or sonication with 2,2,6,6-tetramethyl-4-piperidone (TMPD), the order of TAN formation in the photo-irradiated samples was as follows: rhodamine 6G (R6) > sulforhodamine B (SR) > hematoporphyrin (Hp) > rhodamine 123 (R123) > rose bengal (RB) > erythrosine B (Er) = 0; although there was time-dependent TAN formation when the samples were sonicated, no significant difference among these agents were observed. All these agents suppressed ultrasound-induced OH radical formation detected by EPR-spin trapping. Sensitizer-derived free radicals were markedly observed in SR, RB and Er, while trace level of radicals derived from R6 and R123 were observed. Enhancement of ultrasound-induced decrease of survival in human lymphoma U937 cells was observed at 1.5 W/cm 2 (less than inertial cavitation threshold) for R6, R123, SR and Er, and at 2.3 W/cm 2 for R6, R123, Er, RB and SR. On the other hand, photo-induced decrease of survival was observed for R6, Hp and RB at the same concentration (10 μM). These comparative results suggest that (1) 1O 2 is not involved in the enhancement of ultrasound-induced loss of cell survival, (2) OH radicals and sensitizer-derived free radicals do not take part in the enhancement, and (3) the mechanism is mainly due to certain mechanical stress such as augmentation of physical disruption of cellular membrane by sensitizers in the close vicinity of cells and/or cavitation bubbles.

Coating Noble Metal Nanocrystals (Ag, Au, Pd, and Pt) on Polystyrene Spheres via Ultrasound Irradiation

The method of ultrasound irradiation is used for anchoring metallic nanocrystals (Ag, Au, Pd, and Pt) onto the surface of polystyrene spheres. In former studies, almost all the sonochemically prepared, coated metallic nanomaterials were formed as amorphous nanoparticles (Pol, V. G.; et al. Langmuir 2002, 18, 3352; Pol, V. G.; et al. Chem. Mater. 2003, 15, 1111; Zhong, Z. Y.; et al. Chem. Mater. 1999, 11 (9), 2350; Pol, V. G.; et al. Chem. Mater. 2003, 15, 1378), which were coated on various substrates (silica spheres, carbon spherules, titania, and alumina). On the other hand, the noble metal nanoparticles deposited on polystyrene spheres via ultrasound irradiation yielded nanocrystalline Ag, Au, Pd, and Pt particles on the surface of polystyrene as as-synthesized materials. The sonochemical mechanism is proposed based on chemical interactions between the particles.

Pyridine intercalative sonochemical synthesis and characterization of α-Bi 2Mo 3O 12 phase nanorods

Bismuth molybdate (α-Bi 2Mo 3O 12 phase) nanorods (av. diameter =10 nm) are synthesized for the first time, by pyridine intercalative sonochemical route and characterized for phase purity, composition, and morphology by Raman spectroscopy, thermal analysis, NMR, time of flight secondary ionization mass spectrometer, X-ray diffraction, transmission electron microscopy, and energy-dispersive X-ray analysis. A possible sonochemical mechanism for formation of the α-Bi 2Mo 3O 12 phase nanorods is discussed.

Correlation between sonochemistry of surfactant solutions and human leukemia cell killing by ultrasound and porphyrins.

The synergistic effect of ultrasound and drugs on cells is known as sonodynamic therapy. The use of sonodynamic therapy for the potential clinical treatment of certain tumors is promising, however, the mechanism of sonodynamic therapy could be due to either sonomechanical and/or sonochemical effects on the cells. The aim of the current study is to determine the importance of the sonochemical mechanism for sonodynamic therapy. Sonochemical effects arise from the formation of radical species following collapse of cavitation bubbles. The synergistic effect of ultrasound (47 kHz) and analogues of a gallium-porphyrin derivative (ATX-70) on cytolysis of Human leukemia cells (HL-525 and HL-60) suspended in a cell culture medium were studied. Organic surfactants preferentially accumulate and subsequently decompose at the gas/solution interface of cavitation bubbles, producing secondary radicals that can diffuse to the bulk solution. The gallium porphyrin analogues used in the current study possess two n-alkyl side chains (ATX-C(x), where x = number of carbon atoms, ranging from x = 2 to x = 12). By varying the n-alkyl chain length, thereby modifying the surfactant properties of the ATX-C(x) derivatives, cell killing in relation to the accumulation of ATX-C(x) derivatives at the gas/solution interface of cavitation bubbles was determined. Following sonolysis in the presence of ATX-C(x), a strong correlation for the yield of carbon-centered radicals and cell killing was observed. These results support the hypothesis that a sonochemical mechanism is responsible for the synergistic effect of ultrasound and ATX-C(x) on HL-525 and HL-60 cells.

Synthesis of Europium Oxide Nanorods by Ultrasound Irradiation.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of Europium Oxide Nanorods by Ultrasound Irradiation

Europium oxide nanorods have been prepared by the sonication of an aqueous solution of europium nitrate in the presence of ammonia. The properties of the Eu2O3 nanorods were characterized by X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, Mossbauer spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, high-resolution scanning electron microscopy, and X-ray photoelectron spectroscopy. The particle sizes measured from transmission electron micrographs and HRSEM are about 50 × 500 nm (W × L). A possible sonochemical mechanism for formation of the europium oxide nanorods is discussed.

Sonodynamic effect of erythrosin B on sarcoma 180 cells in vitro

The ultrasonically induced cytotoxic effect of erythrosin B (EB) on isolated sarcoma 180 cells was investigated. The tumor cells were suspended in an air-saturated phosphate buffered saline and exposed to ultrasound at 1.93 MHz in a standing-wave mode for up to 60 s in the presence and absence of EB. The rate of cell damage induction by ultrasound was enhanced by 4–5 times with 160-μM EB, while no cell damage was observed with EB alone. This enhancement was significantly inhibited by histidine. Sonochemical generation of active oxygen species in the presence of EB, measured by ESR spectroscopy, was also inhibited by histidine. These results indicate the involvement of a sonochemical mechanism.

Preliminary results on the effect of power ultrasound on nitrogen oxide and dioxide atmosphere in nitric acid solutions

The effect of ultrasound (20 kHz, 3 W cm −2) on the kinetics of HNO 2 and H 2O 2 formation was investigated in a 1 M HNO 3 medium for NO 2–Ar and NO–Ar gas mixtures in various volume fractions ( f(NO 2)<1.7 vol% and f(NO)<1.1 vol%, respectively). The H 2O 2 formation rate measured in 1 M HNO 3 in the presence of N 2H 5NO 3 was observed to be much lower than that of HNO 2 without N 2H 5NO 3, and was relatively independent of the NO 2 or NO gas volume fractions in the argon atmosphere. The HNO 2 formation rate increased under ultrasound, and was higher with NO than with NO 2. The induction period observed without ultrasound disappeared when ultrasound was applied. The first step in the sonochemical mechanism of HNO 2 formation in the presence of NO 2 involves thermal decomposition of NO 2 into NO within the cavitation bubble. In the second step of HNO 2 formation, NO reacts either with HNO 3 in the cavitation bubble, or with NO 2 in the cavitation bubble or at the bubble/solution interface.

Sonodynamically induced effect of rose bengal on isolated sarcoma 180 cells.

The ultrasonically induced effect of rose bengal (RB) on isolated tumor cells was investigated. Sarcoma 180 cells were suspended in air-saturated phosphate-buffered saline and exposed to ultrasound in standing wave mode for up to 60 s in the presence and absence of RB. Cell viability was determined by the ability to exclude trypan blue. The rate of inducing cell damage by ultrasound was enhanced two to three times with 160 microM RB. while no cell damage was observed with RB alone. This enhancement was significantly inhibited by histidine. Ultrasonically induced in vitro cell damage was significantly enhanced by RB. A sonochemical mechanism may be suggested since the enhancement was significantly inhibited by an active oxygen scavenger.