OBJECTIVE: Noninvasive neuromodulation, particularly through low-intensity ultrasound, holds promise in the fields of neuroscience and neuro-engineering. Ultrasound can stimulate the central nervous system to treat neurologic disorders of the brain and activate peripheral nerve activity. The aim of this study is to investigate the inhibitory effect of low-intensity ultrasonic tibial nerve stimulation on both the physiological state and the overactive bladder (OAB) model in rats.
METHODS: A total of 28 female Sprague-Dawley rats were used in this study. Continuous transurethral instillation of 0.9% normal saline into the bladder was initially performed to stimulate physiological bladder activity. Subsequently, a solution containing 0.3% acetic acid dissolved in saline was instilled to induce rat models of OAB. The study comprised two phases: initial observation of bladder response to low-intensity ultrasound (1 MHz, 1 W/cm2, 50% duty cycle) in seven rats; subsequent exploration of ultrasound frequency (3 MHz) and intensity (2 W/cm2 and 3 W/cm2) effects in 21 rats. The intercontraction intervals (ICIs) were the primary outcome measure. Histologic analysis of tibial nerves and surrounding muscle tissues determined safe ultrasound parameters.
RESULTS: Low-intensity ultrasound tibial nerve stimulation significantly inhibited normal and OAB activity. Ultrasound stimulation at 1 MHz, 1 W/cm2, with a 50% duty cycle significantly prolonged the ICI in both normal (p < 0.0001) and OAB rats (p < 0.01), as did transitioning to a 3 MHz frequency (p = 0.001 for normal rats; p < 0.01 for OAB rats). Similarly, at an intensity of 2 W/cm2 and 1 MHz frequency with a 50% duty cycle, ultrasound stimulation significantly prolonged the ICI in both normal (p < 0.01) and OAB rats (p < 0.005). Furthermore, switching to a 3 W/cm2 ultrasound intensity also significantly extended the ICI in both normal (p < 0.05) and OAB rats (p = 0.01). However, after different ultrasound intensities and frequencies, there was no statistical difference in ICI ratios (preultrasound stimulation vs postultrasound stimulation/preultrasound stimulation ∗ 100%) in all rats (p > 0.05). Low-intensity ultrasound tibial nerve stimulation did not influence baseline pressure, threshold pressure, or maximum pressure. In addition, a latency period in bladder reflex inhibition was induced by low-intensity ultrasound tibial nerve stimulation in some rats. Histologic analysis indicated no evident nerve or muscle tissue damage or abnormalities.
CONCLUSIONS: This study confirmed the potential of transcutaneous ultrasound tibial nerve stimulation to improve bladder function. According to the findings, the ultrasonic intensities ranging from 1 to 3 W/cm2 and frequencies of 1 MHz and 3 MHz are both feasible and safe treatment parameters. This study portended the promise of low-intensity ultrasound tibial nerve stimulation as a treatment for OAB and provides a basis and reference for future clinical applications.

Low-intensity ultrasound, as a form of biological enhancement technology, holds significant importance in the field of biological nitrogen removal. This study utilized low-intensity ultrasound (200 W, 6 min) to enhance partial nitrification and investigated its impact on sludge structure, as well as the internal relationship between structure and properties. The results demonstrated that ultrasound induced a higher concentration of nitrite in the effluent (40.16 > 24.48 mg/L), accompanied by a 67.76% increase in the activity of ammonia monooxygenase (AMO) and a 41.12% increase in the activity of hydroxylamine oxidoreductase (HAO), benefiting the partial nitrification. Based on the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theoretical analysis, ultrasonic treatment enhanced the electrostatic interaction energy (WR) between sludge flocs, raising the total interaction energy from 46.26 kT to 185.54 kT, thereby causing sludge dispersion. This structural alteration was primarily attributed to the fact that the tightly bonded extracellular polymer (TB-EPS) after ultrasound was found to increase hydrophilicity and negative charge, weakening the adsorption between sludge cells. In summary, this study elucidated that the change in sludge structure caused by ultrasonic treatment has the potential to enhance the nitrogen removal performance by partial nitrification.

Cancer development is related to genetic mutations in primary cells, where 5-10% of all cancers are derived from acquired genetic defects, most of which are a consequence of the environment and lifestyle. As it turns out, over half of cancer deaths are due to the generation of drug resistance. The local delivery of chemotherapeutic drugs may reduce their toxicity by increasing their therapeutic dose at targeted sites and by decreasing the plasma levels of circulating drugs. Nanobubbles have attracted much attention as an effective drug distribution system due to their non-invasiveness and targetability. This review aims to present the characteristics of nanobubble systems and their efficacy within the biomedical field with special emphasis on cancer treatment. In vivo and in vitro studies on cancer confirm nanobubbles\' ability and good blood capillary perfusion; however, there is a need to define their safety and side effects in clinical trials.

The study optimized the parameters of low-intensity ultrasound (LIUS), including ultrasound density (0.25 W·mL-1), duration (12 min), and interval time (48 h), through a combination of uniform experiments and response surface prediction. The optimized parameters were aimed at enhancing the removal efficiency of phenolic wastewater to approximately 80%. Furthermore, they facilitate the production of hydrolytic gases in anaerobic digestion, resulting in methane accumulation of up to 237.3 mL·(g VS)-1. Following the long-term experiment, LIUS has been demonstrated to effectively enhance the enzyme activity of anaerobic organisms while also damaging the bacterial structure of microorganisms. However, microbiological analysis indicates that the ultrasound-induced screening mechanism effectively increases the relative abundance of dominant bacterial communities. This facilitated the removal of persistent phenolic contaminants and stabilized the balanced development of the overall anaerobic environment. These findings suggest that LIUS can enhance biological activity and improve the anaerobic treatment of phenolic wastewater.

Cellular reprogramming technologies have been developed with different physicochemical factors to improve the reprogramming efficiencies of induced pluripotent stem cells (iPSCs). Ultrasound is a clinically applied noncontact biophysical factor known for regulating various cellular behaviors but remains uninvestigated for cellular reprogramming. Here, we present a new reprogramming strategy using low-intensity ultrasound (LIUS) to improve cellular reprogramming of iPSCs in vitro and in vivo. Under 3D microenvironment conditions, increased LIUS stimulation shows enhanced cellular reprogramming of the iPSCs. The cellular reprogramming process facilitated by LIUS is accompanied by increased mesenchymal to epithelial transition and histone modification. LIUS stimulation transiently modulates the cytoskeletal rearrangement, along with increased membrane fluidity and mobility to increase HA/CD44 interactions. Furthermore, LIUS stimulation with HA hydrogel can be utilized in application of both human cells and in vivo environment, for enhanced reprogrammed cells into iPSCs. Thus, LIUS stimulation with a combinatorial 3D microenvironment system can improve cellular reprogramming in vitro and in vivo environments, which can be applied in various biomedical fields.

Human brain organoids represent a remarkable platform for modeling neurological disorders and a promising brain repair approach. However, the effects of physical stimulation on their development and integration remain unclear. Here, we report that low-intensity ultrasound significantly increases neural progenitor cell proliferation and neuronal maturation in cortical organoids. Histological assays and single-cell gene expression analyses reveal that low-intensity ultrasound improves the neural development in cortical organoids. Following organoid grafts transplantation into the injured somatosensory cortices of adult mice, longitudinal electrophysiological recordings and histological assays reveal that ultrasound-treated organoid grafts undergo advanced maturation. They also exhibit enhanced pain-related gamma-band activity and more disseminated projections into the host brain than the untreated groups. Finally, low-intensity ultrasound ameliorates neuropathological deficits in a microcephaly brain organoid model. Hence, low-intensity ultrasound stimulation advances the development and integration of brain organoids, providing a strategy for treating neurodevelopmental disorders and repairing cortical damage.

BACKGROUND: Current noninvasive brain stimulation methods are incapable of directly modulating subcortical brain regions critically involved in psychiatric disorders. Transcranial Focused Ultrasound (tFUS) is a newer form of noninvasive stimulation that could modulate the amygdala, a subcortical region implicated in fear.
OBJECTIVE: We investigated the effects of active and sham tFUS of the amygdala on fear circuit activation, skin conductance responses (SCR), and self-reported anxiety during a fear-inducing task. We also investigated amygdala tFUS\' effects on amygdala-fear circuit resting-state functional connectivity.
METHODS: Thirty healthy individuals were randomized in this double-blinded study to active or sham tFUS of the left amygdala. We collected fMRI scans, SCR, and self-reported anxiety during a fear-inducing task (participants viewed red or green circles which indicated the risk of receiving an aversive stimulus), as well as resting-state scans, before and after tFUS.
RESULTS: Compared to sham tFUS, active tFUS was associated with decreased (pre to post tFUS) blood-oxygen-level-dependent fMRI activation in the amygdala (F(1,25) = 4.86, p = 0.04, η2 = 0.16) during the fear task, and lower hippocampal (F(1,27) = 4.41, p = 0.05, η2 = 0.14), and dorsal anterior cingulate cortex (F(1,27) = 6.26, p = 0.02; η2 = 0.19) activation during the post tFUS fear task. The decrease in amygdala activation was correlated with decreased subjective anxiety (r = 0.62, p = 0.03). There was no group effect in SCR changes from pre to post tFUS (F(1,23) = 0.85, p = 0.37). The active tFUS group also showed decreased amygdala-insula (F(1,28) = 4.98, p = 0.03) and amygdala-hippocampal (F(1,28) = 7.14, p = 0.01) rsFC, and increased amygdala-ventromedial prefrontal cortex (F(1,28) = 3.52, p = 0.05) resting-state functional connectivity.
CONCLUSIONS: tFUS can change functional connectivity and brain region activation associated with decreased anxiety. Future studies should investigate tFUS\' therapeutic potential for individuals with clinical levels of anxiety.

Therapeutic ultrasound remains a highly discussed topic in physical therapy due to uncertainty between treatment regimens and biological benefits. Its impact on aged populations, who are vulnerable to insufficient healing after muscle injury because of sarcopenia, is understudied. Despite the coupling between muscle inflammation and regeneration, research on the immune response after therapeutic ultrasound is limited. The objective of this study was to evaluate structure, inflammatory cytokine signaling and immune cell infiltration after therapeutic ultrasound in young and aging murine muscle.
Young (6-week-old) and Adult (52-week-old) male and female mouse non-injured gastrocnemii were treated with either low-intensity pulsed ultrasound at 2 W/cm2 (∼0.243 MPa) or high-intensity pulsed focused ultrasound at 554 W/cm2 (∼5.96 MPa). Cytokine expression was evaluated at 1, 8 and 24 hours, cell infiltration was measured via flow cytometry at 1 and 24 hours and immunofluorescence assessed muscle fiber area, fibrosis and satellite cells at 24 hours after sonication.
Low-intensity pulsed ultrasound induced an early, transient inflammatory response where interleukin (IL)-15 and macrophages (M2 > M1) were increased 1 hour post-sonication. High-intensity pulsed focused ultrasound caused a late, extended immune response where monocyte chemoattractant protein 1 (MCP-1), neutrophils, monocytes and macrophages (M1 > M2) were increased 24 hours post-sonication. Notably, these changes manifested solely in Young gastrocnemius. The Adult gastrocnemius exhibited decreased cytokine expression (IL-1α, IL-6, IL-15, macrophage colony-stimulating factor [M-CSF]) and no alteration in immune cell recruitment post-sonication. There was no damage to muscle structure.
Therapeutic ultrasound induced a pressure-dependent inflammatory response that can augment or mitigate intrinsic muscle cytokine signaling and cell recruitment in adolescent or aged muscle, respectively.

Partial nitrification is a key aspect of efficient nitrogen removal, although practically it suffers from long start-up cycles and unstable long-term operational performance. To address these drawbacks, this study investigated the effect of low intensity ultrasound treatment combined with hydroxylamine (NH2OH) on the performance of partial nitrification. Results show that compared with the control group, low-intensity ultrasound treatment (0.10 W/mL, 15 min) combined with NH2OH (5 mg/L) reduced the time required for partial nitrification initiation by 6 days, increasing the nitrite accumulation rate (NAR) and ammonia nitrogen removal rate (NRR) by 20.4% and 6.7%, respectively, achieving 96.48% NRR. Mechanistic analysis showed that NH2OH enhanced ammonia oxidation, inhibited nitrite-oxidizing bacteria (NOB) activity and shortened the time required for partial nitrification initiation. Furthermore, ultrasonication combined with NH2OH dosing stimulated EPS (extracellular polymeric substances) secretion, increased carbonyl, hydroxyl and amine functional group abundances and enhanced mass transfer. In addition, 16S rRNA gene sequencing results showed that ultrasonication-sensitive Nitrospira disappeared from the ultrasound + NH2OH system, while Nitrosomonas gradually became the dominant group. Collectively, the results of this study provide valuable insight into the enhancement of partial nitrification start-up during the process of wastewater nitrogen removal.

Due to the complex pathological mechanisms of Alzheimer\'s disease (AD), its treatment remains a challenge. One of the major difficulties in treating AD is the difficulty for drugs to cross the blood-brain barrier (BBB). Low-intensity ultrasound (LIUS) is a novel type of ultrasound with neuromodulation function. It has been widely reported that LIUS combined with intravenous injection of microbubbles (MB) can effectively, safely, and reversibly open the BBB to achieve non-invasive targeted drug delivery. However, many studies have reported that LIUS combined with MB-mediated BBB opening (LIUS + MB-BBBO) can improve pathological deposition and cognitive impairment in AD patients and mice without delivering additional drugs. This article reviews the relevant research studies on LIUS + MB-BBBO in the treatment of AD, analyzes its potential mechanisms, and summarizes relevant ultrasound parameters.