A comparative study on generating hydroxyl radicals by single and two-frequency ultrasound with gold nanoparticles and protoporphyrin IX

Study on the mechanism of ultrasonic cavitation effect on the surface properties enhancement of TC17 titanium alloy

In industrial production and scientific research, ultrasonic cavitation technology, with its outstanding physical and chemical processing capabilities, has been widely applied in fields such as material surface modification, chemical synthesis, and biotechnology, becoming a focal point of research and application. This article delves into the effects of different ultrasonic frequencies on cavitation outcomes through the combined use of numerical simulation, fluorescence analysis, and high-speed photography, specifically analyzing the quantitative improvement in the mechanical properties of TC17 titanium alloy under ultrasonic cavitation at frequencies of 20 kHz, 30 kHz, and 40 kHz. The study found that at an ultrasonic frequency of 20 kHz, the maximum expansion radius of cavitation bubbles can reach 51.4 μm, 8.6 times their initial radius. Correspondingly, fluorescence intensity and peak area also increased to 402.8 and 28104, significantly above the baseline level. Moreover, after modification by ultrasonic cavitation, the original machining marks on the surface of TC17 titanium alloy became fainter, with the emergence of new, uniformly distributed microfeatures. The microhardness of the material increased from 373.7 Hv to 383.84 Hv, 396.62 Hv, and 414.06 Hv, with a maximum improvement of 10.8 %. At the same time, surface height difference and roughness significantly decreased (to 3.168 μm and 0.61 μm respectively), with reductions reaching 45.1 % and 42.4 %, indicating a significant improvement in material surface quality. Notably, there is a negative correlation between the improvement of mechanical properties and ultrasonic frequency, suggesting that the improvement effects decrease as ultrasonic frequency increases. This research not only reveals the quantitative relationship between ultrasonic cavitation frequency and material surface modification effects but also provides a solid scientific basis and practical guidance for the application of ultrasonic cavitation technology in surface engineering, signifying the technology's potential for broad application in the future.

Gold-Nanoparticle-Enhanced Radio-Fluorogenic Hydrogel Sensor for Low Radiation Doses in Clinical Radiotherapy

Radio-fluorogenic hydrogel dosimeters are urgently needed in radiotherapy for 3D dose verification. However, few hydrogel sensors have been reported at low absorbed doses under 2 Gy which meets the requirements of clinical practice. Here, we report a new type of gold-nanoparticle-enhanced radio-fluorogenic agarose hydrogel with coumarin as the dose-responsive material. An optimal composition of 3 wt% of agarose, 0.1 mM of gold nanoparticles, and 0.5 mM coumarin was selected. The addition of gold nanoparticles enhanced the hydroxyl radicals generated from the radiolysis of water, which can react with coumarin and generate fluorescent 7-hydroxy-coumarin and, eventually, achieve low-dose verification of 0-2.4 Gy with a high linear correlation coefficient. These findings provide an effective method for 3D dose verification, and will inspire the development of other radio-fluorogenic sensing hydrogels as well.

Sonodynamic therapy for breast cancer: A literature review

Breast cancer (BC) is a malignant tumor with the highest incidence among women. Surgery, radiotherapy, and chemotherapy are currently used as the first-line methods for treating BC. Sonodynamic therapy (SDT) in combination with sonosensitizers exerts a synergistic effect. The therapeutic effects of SDT depend on factors, such as the intensity, frequency, and duration of ultrasound, and the type and the biological model of sonosensitizer. Current reviews have focused on the possibility of using tumor-seeking sonosensitizers, sometimes in combination with different therapies, such as immunotherapy. This study elucidates the therapeutic mechanism of interaction between SDT and tissue as well as the current progress in medical applications of SDT to BC.

Competition between Photoinduced Electron Transfer and Resonance Energy Transfer in an Example of Substituted Cytochrome c-Quantum Dot Systems

Colloidal quantum dots (QDs) are nanoparticles that are able to photoreduce redox proteins by electron transfer (ET). QDs are also able to transfer energy by resonance energy transfer (RET). Here, we address the question of the competition between these two routes of QDs’ excitation quenching, using cadmium telluride QDs and cytochrome c (CytC) or its metal-substituted derivatives. We used both oxidized and reduced versions of native CytC, as well as fluorescent, nonreducible Zn(II)CytC, Sn(II)CytC, and metal-free porphyrin CytC. We found that all of the CytC versions quench QD fluorescence, although the interaction may be described differently in terms of static and dynamic quenching. QDs may be quenchers of fluorescent CytC derivatives, with significant differences in effectiveness depending on QD size. SnCytC and porphyrin CytC increased the rate of Fe(III)CytC photoreduction, and Fe(II)CytC slightly decreased the rate and ZnCytC presence significantly decreased the rate and final level of reduced FeCytC. These might be partially explained by the tendency to form a stable complex between protein and QDs, which promoted RET and collisional quenching. Our findings show that there is a net preference for photoinduced ET over other ways of energy transfer, at least partially, due to a lack of donors, regenerating a hole at QDs and leading to irreversibility of ET events. There may also be a common part of pathways leading to photoinduced ET and RET. The nature of synergistic action observed in some cases allows the hypothesis that RET may be an additional way to power up the ET.

Dual-frequency ultrasound: Strengths and shortcomings to water treatment and disinfection

Since the early 2000s, dual-frequency ultrasound (DFUS) has received much attention for synergistically enhanced elimination of organic pollutants and pathogenic microorganisms from water. In the present review, we have surveyed recent developments in acoustic physics to elucidate the mechanism of synergistic effect under exposure of aqueous media to DFUS. Briefly, the nonlinear dynamics of microbubbles upon DFUS exposure produces additional frequencies, such as harmonics, subharmonics, ultraharmonics and combination frequencies. These increase the probability of bubbles collapse, thereby enhancing cavitation and generating more reactive oxygen species (ROS) for advanced oxidation processes (AOPs). Further, literature data on ROS generation, chemical degradation and microbial inactivation in aqueous media through DFUS alone and DFUS-based AOPs (involving oxidants or catalysts) have been discussed. In this regard, optimal frequency combination, sonoreactor type and transducer arrangement appear to be key parameters for achieving a high synergistic effect. Strengths and shortcomings of DFUS to water treatment and disinfection have been identified and future research directions have been proposed. Though most studies were conducted on pure (matrix-free) aqueous solutions, these AOPs could be applicable for treating real waters.