Tiny bubbles, sound waves clean produce safely and effectively

Good news! Don't we like bubble bath? Would you like to be a bubble bath scientist? 😊

"... new research finds that a bubble bath with a constant acoustic sound in the water may be the best chemical-free, gentle method for cleaning agricultural produce and possibly medical instruments and semiconductors. ...

Agricultural produce is currently cleaned by washing with bubblers for greens or soft brushes for root crops to clean off sediments. Chorine, ozone and peroxyacetic acid are often added to the water as sanitizers. ..."

From the abstract:

"Traditional surface cleaning methods often suffer from drawbacks such as chemical harshness, potential for surface damage, and high-energy consumption. This study investigates an alternative approach: acoustic-driven surface cleaning using millimeter-sized bubbles excited at low, sub-cavitation frequencies.
We identify and characterize a distinct translational resonance of these bubbles, occurring at significantly lower frequencies (e.g., 50 Hz for 1.3 mm diameter bubbles) than the Minnaert resonance for a bubble of the same size. At this translational resonance, stationary bubbles exhibit amplified lateral swaying, while bubbles sliding on an inclined surface display pronounced “stop-and-go” dynamics.
The theoretical model treats the bubble as a forced, damped harmonic oscillator. In this framework, surface tension supplies the restoring force, while the inertia is governed primarily by the hydrodynamic added mass of the surrounding fluid. It accurately predicts the observed resonant frequency scaling with bubble equilibrium radius R0 (∝R0−3/2).
Cleaning efficacy, assessed using protein-based artificial soil on glass slides, was significantly improved when bubbles were driven at their translational resonant frequency compared to off-resonant frequencies or nonacoustic conditions. These findings demonstrate that leveraging translational resonance enhances bubble-induced shear and agitation, offering an effective and sustainable mechanism for surface cleaning."

Tiny bubbles, sound waves clean produce safely and effectively | Cornell Chronicle

Acoustic-driven surface cleaning with millimeter-sized bubbles at translational resonance

Fig. 1 Translational resonance of an acoustically driven bubble (1.3 mm diameter).

Fig. 5 Cleaning performance and mechanism under resonant excitation.

Ultrasound activated microbubbles enhance the activity of standard of care therapeutics in pancreatic cancer | AZBio

Good news! Cancer is history (soon)! Notice, the new therapy is already a registered trademark.

"Scientists ... report that the ultrasound based Acoustic Cluster Therapy ... significantly enhanced the antitumor efficacy of standard care therapies in a preclinical model for pancreatic cancer. ...
The ACT® technology is based on microclusters of microbubble-microdroplets and when sonicated, vaporization of the microdroplets lead to the formation of larger ACT® bubbles. The formation and subsequent oscillation of the ACT® bubbles in the microvasculature produces mechanical bioeffects that enhance drug delivery and efficacy. TGen has evaluated the effectiveness of the technology in a preclinical pancreatic cancer model, and the results demonstrated that ACT® significantly improved the therapeutic efficacy of two cornerstone treatment regimens in the management of pancreatic cancer. ..."

From the abstract:

"Pancreatic ductal adenocarcinomas respond poorly to chemotherapy, in part due to the dense tumor stroma that hinders drug delivery. Ultrasound (US) in combination with microbubbles has previously shown promise as a means to improve drug delivery, and the therapeutic efficacy of ultrasound-mediated drug delivery is currently being evaluated in multiple clinical trials. However, most of these utilize echogenic contrast agents engineered for imaging, which might not be optimal compared to specialized formulations tailored for drug delivery. In this study, we evaluated the in vivo efficacy of phase-shifting microbubble-microdroplet clusters that, upon insonation, form bubbles in the size range of 20–30 μm. We developed a patient-derived xenograft model of pancreatic cancer implanted in mice that largely retained the stromal content of the originating tumor and compared tumor growth in mice given chemotherapeutics (nab-paclitaxel plus gemcitabine or liposomal irinotecan) with mice given the same chemotherapeutics in addition to ultrasound and acoustic cluster therapy. We found that acoustic cluster therapy significantly improved the effect of both chemotherapeutic regimens and resulted in 7.2 times higher odds of complete remission of the tumor compared to the chemotherapeutics alone."

Ultrasound activated microbubbles enhance the activity of standard of care therapeutics in pancreatic cancer | AZBio

Effect of acoustic cluster therapy (ACT®) combined with chemotherapy in a patient-derived xenograft mouse model of pancreatic cancer

Graphical abstract:

Nanobubble Injections Can Explode Tumors, Say Researchers

This seems to be an interesting approach to treat cancer!

"... Researchers say they can destroy cancerous tumors by injecting nanobubbles into the patient’s bloodstream – then exploding them.

The tiny bubbles – 2,500 times smaller than a single grain of salt – gather around the tumor and are then detonated by low frequency ultrasound waves. ...
They now hope it could become an effective alternative to surgical removal of tumors in humans. ...
The treatment can be used to effectively treat solid tumors deep within the body and is suitable for patients who are unfit for tumor resection surgery. The drawback, however, is that the heat and high intensity of the ultrasound waves may damage the tissues near the tumor. ..."

From the abstract:

"Scaling down the size of microbubble contrast agents to the nanometer level holds the promise for noninvasive cancer therapy. However, the small size of nanobubbles limits the obtained bioeffects as a result of ultrasound cavitation, when operating near the nanobubble resonance frequency. Here we show that coupled with low energy insonation at a frequency of 80 kHz, well below the resonance frequency of these agents, nanobubbles serve as noninvasive therapeutic warheads that trigger potent mechanical effects in tumors following a systemic injection. ... Complete nanobubble destruction was achieved at a mechanical index of 2.6 for the 250 kHz insonation vs. 1.2 for the 80 kHz frequency. ... In vitro in breast cancer tumor cells, the cell viability was reduced to 17.3 ± 1.7% of live cells. In vivo, in a breast cancer tumor mouse model, nanobubble tumor distribution and accumulation were evaluated by high frequency ultrasound imaging. Finally, nanobubble-mediated low frequency insonation of breast cancer tumors resulted in effective mechanical tumor ablation and tumor tissue fractionation. This approach provides a unique theranostic platform for safe, noninvasive and low energy tumor mechanotherapy."

Nanobubble Injections Can Explode Tumors, Say Researchers

Low frequency nanobubble-enhanced ultrasound mechanotherapy for noninvasive cancer surgery (no public access)

Acoustical tweezers trap microbubbles

Amazing stuff! This is admittedly an older science related article from July 2020!

"... that the acoustic version [as opposed to optical tweezers] employs a helicoidal or “vortex” beam of ultrasound. This, he says, has several benefits for medical applications. ... Ultrasound can also penetrate deeper into opaque media such as biological tissue than optical waves ..."

"Remote positioning and activation of drug-loaded microparticles in vivo are a central pursuit of nanomedicine. Optical, magnetic, and acoustic fields have been used to position and sort microparticles in vitro, but the translation in vivo remains challenging. ... acoustical tweezers are considered an ideal candidate for in vivo contactless manipulation. ...Here we use a single-beam acoustical trap to manipulate microbubbles in three dimensions through materials that mimic biological tissues. We establish the trapping mechanism, which is strikingly different from conventional acoustic trapping of bubbles. We also demonstrate controlled release from nanoparticle-loaded microbubbles with an independent acoustic trigger. ..."

Acoustical tweezers trap microbubbles – Physics World Researchers at Imperial College London, UK have demonstrated for the first time that microscopic bubbles of gas can be manipulated using sound waves. The new “acoustical tweezers” overcome certain limitations of their optical cousins (such as not propagating well through opaque tissues), and could therefore enable a host of biomedical applications.

Here is the link to the underlying research paper:

Acoustic trapping of microbubbles in complex environments and controlled payload release