Hydrodynamic cavitation kills prostate cells and ablates benign prostatic hyperplasia tissue

Hydrodynamic Cavitation on a Chip: A Tool to Detect Circulating Tumor Cells

Circulating tumor cells (CTCs) are essential biomarkers for cancer diagnosis. Although various devices have been designed to detect, enumerate, and isolate CTCs from blood, some of these devices could have some drawbacks, such as the requirement of labeling, long process time, and high cost. Here, we present a microfluidic device based on the concept of "hydrodynamic cavitation-on-chip (HCOC)", which can detect CTCs in the order of minutes. The working principle relies on the difference of the required inlet pressure for cavitation inception of working fluids when they pass through the microfluidic device. The interface among the solid/floating particles, liquid, and vapor phases plays an important role in the strength of the fluid to withstand the rupture and cavitation formation. To this end, four experimental groups, including the "cell culture medium", "medium + Jurkat cells", "medium + Jurkat cells + CTCs", and "medium + CTCs", were tested as a proof of concept with two sets of fabricated microfluidic chips with the same geometrical dimensions, in which one set contained structural sidewall roughness elements. Jurkat cells were used to mimic white blood cells, and MDA-MB-231 cells were spiked into the medium as CTCs. Accordingly, the group with CTCs led to detectable earlier cavitation inception. Additionally, the effect of the CTC concentration on cavitation inception and the effect of the presence of sidewall roughness elements on the earlier inception were evaluated. Furthermore, CTC detection tests were performed with cancer cell lines spiked in blood samples from healthy donors. The results showed that this approach, HCOC, could be a potential approach to detect the presence of CTCs based on cavitation phenomenon and offer a cheap, user-friendly, and rapid tool with no requirement for any biomarker or extensive films acting as a biosensor. This approach also possesses straightforward application procedures to be employed for detection of CTCs.

Fundamentals, biomedical applications and future potential of micro-scale cavitation-a review

Thanks to the developments in the area of microfluidics, the cavitation-on-a-chip concept enabled researchers to control and closely monitor the cavitation phenomenon in micro-scale. In contrast to conventional scale, where cavitation bubbles are hard to be steered and manipulated, lab-on-a-chip devices provide suitable platforms to conduct smart experiments and design reliable devices to carefully harness the collapse energy of cavitation bubbles in different bio-related and industrial applications. However, bubble behavior deviates to some extent when confined to micro-scale geometries in comparison to macro-scale. Therefore, fundamentals of micro-scale cavitation deserve in-depth investigations. In this review, first we discussed the physics and fundamentals of cavitation induced by tension-based as well as energy deposition-based methods within microfluidic devices and discussed the similarities and differences in micro and macro-scale cavitation. We then covered and discussed recent developments in bio-related applications of micro-scale cavitation chips. Lastly, current challenges and future research directions towards the implementation of micro-scale cavitation phenomenon to emerging applications are presented.

A Flexible Cystoscope Based on Hydrodynamic Cavitation for Tumor Tissue Ablation

OBJECTIVE

Hydrodynamic cavitation is characterized by the formation of bubbles inside a flow due to local reduction of pressure below the saturation vapor pressure. The resulting growth and violent collapse of bubbles lead to a huge amount of released energy. This energy can be implemented in different fields such as heat transfer enhancement, wastewater treatment and chemical reactions. In this study, a cystoscope based on small scale hydrodynamic cavitation was designed and fabricated to exploit the destructive energy of cavitation bubbles for treatment of tumor tissues. The developed device is equipped with a control system, which regulates the movement of the cystoscope in different directions. According to our experiments, the fabricated cystoscope was able to locate the target and expose cavitating flow to the target continuously and accurately. The designed cavitation probe embedded into the cystoscope caused a significant damage to prostate cancer and bladder cancer tissues within less than 15 minutes. The results of our experiments showed that the cavitation probe could be easily coupled with endoscopic devices because of its small diameter. We successfully integrated a biomedical camera, a suction tube, tendon cables, and the cavitation probe into a 6.7 mm diameter cystoscope, which could be controlled smoothly and accurately via a control system. The developed device is considered as a mechanical ablation therapy, can be a solid alternative for minimally invasive tissue ablation methods such as radiofrequency (RF) and laser ablation, and could have lower side effects compared to ultrasound therapy and cryoablation.

Stimuli-responsive nanobubbles for biomedical applications

Stimuli-responsive nanobubbles have received increased attention for their application in spatial and temporal resolution of diagnostic techniques and therapies, particularly in multiple imaging methods, and they thus have significant potential for applications in the field of biomedicine. This review presents an overview of the recent advances in the development of stimuli-responsive nanobubbles and their novel applications. Properties of both internal- and external-stimuli responsive nanobubbles are highlighted and discussed considering the potential features required for biomedical applications. Furthermore, the methods used for synthesis and characterization of nanobubbles are outlined. Finally, novel biomedical applications are proposed alongside the advantages and shortcomings inherent to stimuli-responsive nanobubbles.

Clinical and Microbiological Effects of Weekly Supragingival Irrigation with Aerosolized 0.5% Hydrogen Peroxide and Formation of Cavitation Bubbles in Gingival Tissues after This Irrigation: A Six-Month Randomized Clinical Trial

Introduction

The study investigated the effect of weekly supragingival irrigation with aerosolized 0.5% hydrogen peroxide (H₂O₂) solution as a maintenance periodontal therapy on clinical and microbiological parameters in patients with chronic periodontitis. The other purpose was to investigate whether cavitation bubbles can penetrate not only into periodontitis-damaged tissues but also into ex vivo porcine healthy periodontal tissues.

Materials and Methods

The study included 35 systemically healthy patients with chronic periodontitis (CP). After nonsurgical periodontal debridement (NSPD), all patients were randomized into two groups: the Control group (NSDP alone, n = 18) and the Test group (NSDP plus supragingival irrigation, n = 17). Clinical (Approximal Plaque Index (API), Bleeding Index (BI), and Modified Gingival Index (MGI)) and microbiological (Polymerase Chain Reaction technology (using a micro-IDent® kit)) measurements were performed at the initial time point, 3 months, and 6 months after NSPD. The impact of supragingival irrigation on diseased gingival tissues of CP patients (n = 5) and on ex vivo porcine healthy gingival tissue samples (n = 3) was evaluated to estimate morphological changes in healthy and diseased gingival tissues.

Results

Morphological data revealed that supragingival irrigation caused the formation of cavitation bubbles in diseased gingival tissue of CP patients and in healthy porcine gingival tissues. The decrease in API, BI, and MGI scores after 6 months in the Test group significantly (p ≤ 0.01, p ≤ 0.05, and p ≤ 0.01, respectively) exceeded that in the Control group. Test group patients demonstrated a decrease in periodontal sites showing Pocket Probing Depth > 4 mm and, after 6 months, a statistically significant decrease in the proportion of periopathogenic bacteria.

Conclusion

The effectiveness of mechanical periodontal treatment combined with weekly supragingival irrigation with aerosolized 0.5% H₂O₂ solution on clinical and microbiological parameters of periodontal tissues of periodontitis patients is reliably higher than that of mechanical periodontal debridement alone. It has been found that cavitation bubbles as a result of irrigation with the aerosolized 0.5% hydrogen peroxide solution can form not only in periodontal tissues of periodontitis patients but also in ex vivo porcine healthy gingival tissues.

Study of Protein-protein Interactions in Autophagy Research

Protein-protein interactions are important for understanding cellular signaling cascades and identifying novel pathway components and protein dynamics. The majority of cellular activities require physical interactions between proteins. To analyze and map these interactions, various experimental techniques as well as bioinformatics tools were developed. Autophagy is a cellular recycling mechanism that allows the cells to cope with different stressors, including nutrient deprivation, chemicals, and hypoxia. In order to better understand autophagy-related signaling events and to discover novel factors that regulate protein complexes in autophagy, we performed protein-protein interaction screens. Validation of these screening results requires the use of immunofluorescence and immunoprecipitation techniques. In this system, specific autophagy-related protein-protein interactions that we discovered were tested in Neuro2A (N2A) and HEK293T cell lines. Details of the technical procedures used are explained in this visualized experiment paper.

A Microfluidic System with Surface Patterning for Investigating Cavitation Bubble(s)-Cell Interaction and the Resultant Bioeffects at the Single-cell Level

In this manuscript, we first describe the fabrication protocol of a microfluidic chip, with gold dots and fibronectin-coated regions on the same glass substrate, that precisely controls the generation of tandem bubbles and individual cells patterned nearby with well-defined locations and shapes. We then demonstrate the generation of tandem bubbles by using two pulsed lasers illuminating a pair of gold dots with a few-microsecond time delay. We visualize the bubble-bubble interaction and jet formation by high-speed imaging and characterize the resultant flow field using particle image velocimetry (PIV). Finally, we present some applications of this technique for single cell analysis, including cell membrane poration with macromolecule uptake, localized membrane deformation determined by the displacements of attached integrin-binding beads, and intracellular calcium response from ratiometric imaging. Our results show that a fast and directional jetting flow is produced by the tandem bubble interaction, which can impose a highly localized shear stress on the surface of a cell grown in close proximity. Furthermore, different bioeffects can be induced by altering the strength of the jetting flow by adjusting the standoff distance from the cell to the tandem bubbles.

Ablative Focused Ultrasound Synergistically Enhances Thermally Triggered Chemotherapy for Prostate Cancer in Vitro

High-intensity focused ultrasound (HIFU) can locally ablate biological tissues such as tumors, i.e., induce their rapid heating and coagulative necrosis without causing damage to surrounding healthy structures. It is widely used in clinical practice for minimally invasive treatment of prostate cancer. Nonablative, low-power HIFU was established as a promising tool for triggering the release of chemotherapeutic drugs from temperature-sensitive liposomes (TSLs). In this study, we combine ablative HIFU and thermally triggered chemotherapy to address the lack of safe and effective treatment options for elderly patients with high-risk localized prostate cancer. DU145 prostate cancer cells were exposed to chemotherapy (free and liposomal Sorafenib) and ablative HIFU, alone or in combination. Prior to cell viability assessment by trypan blue exclusion and flow cytometry, the uptake of TSLs by DU145 cells was verified by confocal microscopy and cryogenic scanning electron microscopy (cryo-SEM). The combination of TSLs encapsulating 10 μM Sorafenib and 8.7W HIFU resulted in a viability of less than 10% at 72 h post-treatment, which was significant less than the viability of the cells treated with free Sorafenib (76%), Sorafenib-loaded TSLs (63%), or HIFU alone (44%). This synergy was not observed on cells treated with Sorafenib-loaded nontemperature sensitive liposomes and HIFU. According to cryo-SEM analysis, cells exposed to ablative HIFU exhibited significant mechanical disruption. Water bath immersion experiments also showed an important role of mechanical effects in the synergistic enhancement of TSL-mediated chemotherapy by ablative HIFU. This combination therapy can be an effective strategy for treatment of geriatric prostate cancer patients.

RACK1 Is an Interaction Partner of ATG5 and a Novel Regulator of Autophagy

Autophagy is biological mechanism allowing recycling of long-lived proteins, abnormal protein aggregates, and damaged organelles under cellular stress conditions. Following sequestration in double- or multimembrane autophagic vesicles, the cargo is delivered to lysosomes for degradation. ATG5 is a key component of an E3-like ATG12-ATG5-ATG16 protein complex that catalyzes conjugation of the MAP1LC3 protein to lipids, thus controlling autophagic vesicle formation and expansion. Accumulating data indicate that ATG5 is a convergence point for autophagy regulation. Here, we describe the scaffold protein RACK1 (receptor activated C-kinase 1, GNB2L1) as a novel ATG5 interactor and an autophagy protein. Using several independent techniques, we showed that RACK1 interacted with ATG5. Importantly, classical autophagy inducers (starvation or mammalian target of rapamycin blockage) stimulated RACK1-ATG5 interaction. Knockdown of RACK1 or prevention of its binding to ATG5 using mutagenesis blocked autophagy activation. Therefore, the scaffold protein RACK1 is a new ATG5-interacting protein and an important and novel component of the autophagy pathways.

Review on Lithotripsy and Cavitation in Urinary Stone Therapy

Cavitation is the sudden formation of vapor bubbles or voids in liquid media and occurs after rapid changes in pressure as a consequence of mechanical forces. It is mostly an undesirable phenomenon. Although the elimination of cavitation is a major topic in the study of fluid dynamics, its destructive nature could be exploited for therapeutic applications. Ultrasonic and hydrodynamic sources are two main origins for generating cavitation. The purpose of this review is to give the reader a general idea about the formation of cavitation phenomenon and existing biomedical applications of ultrasonic and hydrodynamic cavitation. Because of the high number of the studies on ultrasound cavitation in the literature, the main focus of this review is placed on the lithotripsy techniques, which have been widely used for the treatment of urinary stones. Accordingly, cavitation phenomenon and its basic concepts are presented in Section II. The significance of the ultrasound cavitation in the urinary stone treatment is discussed in Section III in detail and hydrodynamic cavitation as an important alternative for the ultrasound cavitation is included in Section IV. Finally, side effects of using both ultrasound and hydrodynamic cavitation in biomedical applications are presented in Section V.

Assessment of Probe-to-Specimen Distance Effect in Kidney Stone Treatment With Hydrodynamic Cavitation

The aim of this study is to focus on the effect of probe-to-specimen distance in kidney stone treatment with hydrodynamic bubbly cavitation. Cavitating bubbles were generated by running phosphate buffered saline (PBS) through stainless steel tubing of inner diameter of 1.56 mm at an inlet pressure of ∼10,000 kPa, which was connected to a 0.75 mm long probe with an inner diameter of 147 μm at the exit providing a sudden contraction and thus low local pressures. The bubbles were targeted on the surface of nine calcium oxalate kidney stones (submerged in a water pool at room temperature and atmospheric pressure) from three different distances, namely, 0.5 mm, 2.75 mm, and 7.75 mm. The experiments were repeated for three different time durations (5 min, 10 min, and 20 min). The experimental data show that amongst the three distances considered, the distance of 2.75 mm results in the highest erosion amount and highest erosion rate (up to 0.94 mg/min), which suggests that a closer distance does not necessarily lead to a higher erosion rate and that the probe-to-specimen distance is a factor of great importance, which needs to be optimized. In order to be able to explain the experimental results, a visualization study was also conducted with a high speed CMOS camera. A new correlation was developed to predict the erosion rates on kidney stones exposed to hydrodynamic cavitation as a function of material properties, time, and distance.