Ultrasound Stimuli Research Articles

A review of the bioeffects of low-intensity focused ultrasound and the benefits of a cellular approach.

This review article highlights the historical developments and current state of knowledge of an important neuromodulation technology: low-intensity focused ultrasound. Because compelling studies have shown that focused ultrasound can modulate neuronal activity non-invasively, especially in deep brain structures with high spatial specificity, there has been a renewed interest in attempting to understand the specific bioeffects of focused ultrasound at the cellular level. Such information is needed to facilitate the safe and effective use of focused ultrasound to treat a number of brain and nervous system disorders in humans. Unfortunately, to date, there appears to be no singular biological mechanism to account for the actions of focused ultrasound, and it is becoming increasingly clear that different types of nerve cells will respond to focused ultrasound differentially based on the complement of their ion channels, other membrane biophysical properties, and arrangement of synaptic connections. Furthermore, neurons are apparently not equally susceptible to the mechanical, thermal and cavitation-related consequences of focused ultrasound application-to complicate matters further, many studies often use distinctly different focused ultrasound stimulus parameters to achieve a reliable response in neural activity. In this review, we consider the benefits of studying more experimentally tractable invertebrate preparations, with an emphasis on the medicinal leech, where neurons can be studied as unique individual cells and be synaptically isolated from the indirect effects of focused ultrasound stimulation on mechanosensitive afferents. In the leech, we have concluded that heat is the primary effector of focused ultrasound neuromodulation, especially on motoneurons in which we observed a focused ultrasound-mediated blockade of action potentials. We discuss that the mechanical bioeffects of focused ultrasound, which are frequently described in the literature, are less reliably achieved as compared to thermal ones, and that observations ascribed to mechanical responses may be confounded by activation of synaptically-coupled sensory structures or artifacts associated with electrode resonance. Ultimately, both the mechanical and thermal components of focused ultrasound have significant potential to contribute to the sculpting of specific neural outcomes. Because focused ultrasound can generate significant modulation at a temperature <5°C, which is believed to be safe for moderate durations, we support the idea that focused ultrasound should be considered as a thermal neuromodulation technology for clinical use, especially targeting neural pathways in the peripheral nervous system.

C. elegans: Sensing the low-frequency profile of amplitude-modulated ultrasound

Several research groups have demonstrated that C. elegans can respond to pulsed ultrasound stimuli, and elucidating the underlying mechanisms is necessary to develop ultrasound neuromodulation. Here, amplitude-modulated (AM) ultrasound is applied to C. elegans, and its behavioral responses are investigated in detail. By loading surface acoustic waves (SAWs) onto free-moving worms on an agar surface, a carrier wave with a frequency of 8.80 MHz is selected. The signal is modulated by a rectangular or sinusoidal profile. It is demonstrated that sinusoidal modulation can produce similar responses in worms to rectangular modulation, with the strongest responses occurring at modulation frequencies of around 1.00 kHz. Meanwhile, the behavioral response is relatively weak when the ultrasonic signal is unmodulated, that is, when only the carrier wave is applied. At modulation frequencies other than 100.00 Hz to 10.00 kHz, the worms respond weakly, but when a second modulation frequency of 1.00 kHz is introduced, an improvement in response can be observed. These results suggest that C. elegans may sense the low-frequency envelope and respond to amplitude-modulated ultrasonic stimuli like an amplitude demodulator. MEC-4, an ion channel for touch sensing, is involved in the behavioral response of C. elegans to ultrasound in the present setup.

Manganese-enhanced magnetic resonance imaging detects activation of limbic structures in response to auditory stimuli of different frequencies

PurposeAs we are exposed to stress on a daily basis, it is important to detect and treat stress during the subclinical period. However, methods to quantify and confirm stress are currently unavailable, and the detection of subclinical stressors is difficult. This study aimed to determine whether manganese-enhanced magnetic resonance imaging (MEMRI) could be used to assess stress in rat brains. MethodsWe exposed male Wistar/ST rats bred in a specific pathogen-free environment to ultrasound stimuli (22 kHz and 55 kHz) for 10 days and then assessed brain activities using MEMRI, the light/dark box test, and ΔFosB immunohistochemical staining. ResultsIn the MEMRI assessments, exposure at 22 kHz activated the periaqueductal gray, while exposure at 55 kHz specifically enhanced activity in the nucleus accumbens core and the orbitofrontal cortex. The exploratory behavior of the 55-kHz group increased sharply, while that of the 22-kHz group showed a lower exploratory value. ΔFosB expression increased in the orbitofrontal cortex, nucleus accumbens, periaqueductal gray, and amygdaloid nucleus in the 22-kHz group. ConclusionUltrasound stimuli at 22 kHz suppressed weight gain in rats and excessive ΔFosB induction in the nucleus accumbens caused excessive sensitization of the neural circuit, thereby contributing to pathological behavior. We thus demonstrated that MEMRI can be useful to objectively assess the pathophysiology of stress-related disorders.

Investigation of Inertial Cavitation Induced by Modulated Focused Ultrasound Stimuli

Abstract A passive cavitation detection setup is used to assess and verify the capability of frequency- and amplitudemodulated ultrasound burst signals on the generation of inertial cavitation. The measurements were conducted with a flowthrough tissue-mimicking phantom with a canal of dc = 1mm in diameter simulating a fine blood vessel. By means of a flow velocity of vf= 50mm/s circulating blood in the cardiovascular system is imitated. Applying signal frequencies from f = 550 − 950 kHz and peak rarefaction pressures in a range from ˆpPRFP ≈ 0.17 − 1.81 MPa, various ultrasound stimuli with alternating signal parameters were investigated in the absence and presence of a talcum-water mixture acting as cavitation nuclei. By evaluating the broadband emissions in the frequency domain and calculating the voltage spectral density Srm, the results can be compared. The findings of the present study demonstrate that each ultrasound stimulus triggers a similar strength of cavitation noise at the same Mechanical Index, representing a certain pressure. Over the whole frequency and Mechanical Index (pressure) range, each ultrasound signal type generates a voltage spectral density from Srm= 0.25 − 2.25 V/ √ Hz.

GHz Ultrasound and Electrode Chip-Scale Arrays Stimulate and Influence Morphology of Human Neural Cells.

This study describes the effects of chip-scale gigahertz (GHz) ultrasound (US) and electrical stimulus on the morphology, functionality, and viability of neural cells in vitro. The GHz frequency stimulation is achieved using aluminum nitride piezoelectric transducers fabricated on a silicon wafer, operating at 1.47 GHz, corresponding to the film's thickness mode resonance. These devices are used to stimulate SH-SY5Y neural cells in vitro and observe effects on the morphology and viability of the stimulated cells. It is possible to use these devices to deliver either ultrasonic stimulus alone or US stimulus in conjunction with electrical stimulus. Viability tests demonstrated that the neurons retained structural integrity and viability across a wide range of GHz US stimulus intensities (0-1.2 W/cm2), validating that measurements occur at nontoxic doses of US. Neural stimulation is validated with these devices following the outputs of a previous study, with the normalized fluorescence intensity of activated cells between 1.9 and 2.4. The 300-s ultrasonic stimulation at 1.47 GHz and 0.05 W/cm2 peak intensity led to a decrease in nuclear elongation by 17.5% and a cross-sectional area decrease by 17.8% across three independent trials of over 150 cells per category ( ). The F-actin governed cellular elongation increased in length by up to 16.3% in cells exposed to an ultrasonic stimulus or costimulus ( ). Neurite length increased following ultrasonic stimulation compared with control by 75.8% ( ). This article demonstrates new GHz US and electrical chip-scale arrays with apparent effects in both neural excitation and cell morphology.

Two pathways are required for ultrasound-evoked behavioral changes in Caenorhabditis elegans.

Ultrasound has been shown to affect the function of both neurons and non-neuronal cells, but, the underlying molecular machinery has been poorly understood. Here, we show that at least two mechanosensitive proteins act together to generate C. elegans behavioral responses to ultrasound stimuli. We first show that these animals generate reversals in response to a single 10 msec pulse from a 2.25 MHz ultrasound transducer. Next, we show that the pore-forming subunit of the mechanosensitive channel TRP-4, and a DEG/ENaC/ASIC ion channel MEC-4, are both required for this ultrasound-evoked reversal response. Further, the trp-4;mec-4 double mutant shows a stronger behavioral deficit compared to either single mutant. Finally, overexpressing TRP-4 in specific chemosensory neurons can rescue the ultrasound-triggered behavioral deficit in the mec-4 null mutant, suggesting that both TRP-4 and MEC-4 act together in affecting behavior. Together, we demonstrate that multiple mechanosensitive proteins likely cooperate to transform ultrasound stimuli into behavioral changes.

Mitochondria-Targeted Mesoporous Titanium Dioxide Nanoplatform for Synergistic Nitric Oxide Gas-Sonodynamic Therapy of Breast Cancer.

BackgroundSonodynamic therapy (SDT) has rapidly advanced as a promising alternative to conventional photodynamic therapy owing to its preferable therapeutic depth. However, single-modal SDT exhibits limited efficacy due to the long-term hypoxia in tumors.Method and ResultsTo address these issues, we proposed a synergistic SDT strategy that integrates mitochondrial targeting with nitric oxide (NO) gas therapy by using multifunctional nanoplatforms. The nanoplatform, which was named as T-mTNPs@L-Arg, was composed of mesoporous titanium dioxide loaded with the NO donor precursor L-arginine (L-Arg) and modified with triphenyl phosphonium (TPP), a mitochondria-targeting ligand. Therefore, T-mTNPs@L-Arg could efficiently concentrate into mitochondria and release NO gas as well as generate reactive oxygen species (ROS) with ultrasound stimulus. Importantly, the released NO gas exerted multiple synergies with SDT, including inducing NO poisoning, generating more lethal reactive nitrogen species (RNS) by reaction with ROS, and alleviating hypoxia through NO-mediated mitochondrial respiration inhibition. On account of the synergistic effects, T-mTNPs@L-Arg showed an outstanding SDT efficacy and a reduced side effect.ConclusionThis work designed a nanoplatform to integrate mitochondria targeting, SDT and NO gas therapy, providing a new strategy for highly efficient breast cancer therapy.

A mechanoresponsive nano-sized carrier achieves intracellular release of drug on external ultrasound stimulus.

Control over intracellular release of therapeutic compounds incorporated into nano-carriers will open new possibilities for targeted treatments of various diseases including cancer, and viral and bacterial infections. Here we report our study on mechanoresponsive nano-sized liposomes which, following internalization by cells, achieve intracellular delivery of encapsulated cargo on application of external ultrasound stimulus. This is demonstrated in a bespoke cell reporter system designed to assess free drug in cytoplasm. Biophysical analyses show that drug release is attributable to the action of a mechanoresponsive spiropyran-based compound embedded in the liposomal lipid membrane. Exposure to external ultrasound stimulus results in opening of the molecular structure of the embedded spiropyran, a consequent increase in liposomal lipid membrane fluidity, and size-dependent release of encapsulated model drugs, all pointing to lipid bilayer perturbation. The study hence illustrates feasibility of the proposed concept where intracellular drug release from mechanoresponsive liposomes can be triggered on demand by external ultrasound stimulus.

Hybrid Carbon Dot Assembly as a Reactive Oxygen Species Nanogenerator for Ultrasound-Assisted Tumor Ablation.

The efficacy of reactive oxygen species (ROS)-based therapy is substantially constrained by the limited ROS generation, stern activation conditions, and lack of a straightforward reaction paradigm. Carbon dots (CDs) have been highly sought after for therapeutic applications for their biocompatibility and intrinsic fluorescence imaging capabilities, making them suitable for ROS generation. Herein, we synthesized a CD-based ultrasmall hybrid nanostructure possessing active sites of Mo, Cu, and IR-780 dye. After cooperative self-assembly with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-poly(ethylene glycol), the obtained assembly (CMIR-CDa) exhibits near-infrared fluorescence imaging and photoacoustic tomography. Interestingly, CMIR-CDa can generate singlet oxygen (1O2), hydroxyl radical (·OH), and superoxide radical anion (O2• –) upon ultrasound stimulus owing to its sonosensitizing and enzyme-mimicking properties, showing an enhanced efficacy for tumor ablation in vivo. The collective in vitro and in vivo results indicate that CMIR-CDa has a high potency as an ROS nanogenerator under US irradiation, even at a low concentration. The present study offers an approach for engineering hybrid CDs in a bioinspired way for intratumoral ROS augmentation in response to deep tissue penetrable external stimuli.

Precise Ultrasound Neuromodulation in a Deep Brain Region Using Nano Gas Vesicles as Actuators.

Ultrasound is a promising new modality for non‐invasive neuromodulation. Applied transcranially, it can be focused down to the millimeter or centimeter range. The ability to improve the treatment's spatial resolution to a targeted brain region could help to improve its effectiveness, depending upon the application. The present paper details a neurostimulation scheme using gas‐filled nanostructures, gas vesicles (GVs), as actuators for improving the efficacy and precision of ultrasound stimuli. Sonicated primary neurons display dose‐dependent, repeatable Ca2+ responses, closely synced to stimuli, and increased nuclear expression of the activation marker c‐Fos in the presence of GVs. GV‐mediated ultrasound triggered rapid and reversible Ca2+ responses in vivo and could selectively evoke neuronal activation in a deep‐seated brain region. Further investigation indicate that mechanosensitive ion channels are important mediators of this effect. GVs themselves and the treatment scheme are also found not to induce significant cytotoxicity, apoptosis, or membrane poration in treated cells. Altogether, this study demonstrates a simple and effective method to achieve enhanced and better‐targeted neurostimulation with non‐invasive low‐intensity ultrasound.

Ultrasound Molecular Imaging for the Guidance of Ultrasound-Triggered Release of Liposomal Doxorubicin and Its Treatment Monitoring in an Orthotopic Prostatic Tumor Model in Rat

Liposome encapsulation of drugs is an interesting approach in cancer therapy to specifically release the encapsulated drug at the desired treatment site. In addition to thermo-, pH-, light-, enzyme- or redox-responsive liposomes, which have had promising results in (pre-) clinical studies, ultrasound-triggered sonosensitive liposomes represent an exciting alternative to locally trigger the release from these cargos. Localized drug release requires precise tumor visualization to produce a targeted and ultrasound stimulus. We used ultrasound molecular imaging (USMI) with BR55, a vascular endothelial growth factor receptor 2 (VEGFR2)-targeted ultrasound contrast agent, to guide ultrasound-triggered release of sonosensitive liposomes encapsulating doxorubicin (L-DXR) in an orthotopic prostatic rodent tumor model. Forty-eight hours after L-DXR injection, local release of doxorubicin was triggered with a confocal ultrasound device with two focused transducers, 1.1-MHz center frequency, and peak positive and negative pressures of 20.5 and 13 MPa at focus. Tumor size decreased by 20% in 2 wk with L-DXR alone (n = 9) and by 70% after treatment with L-DXR and confocal ultrasound (n = 7) (p < 0.01). The effect of doxorubicin on perfusion/vascularity and VEGFR2 expression was evaluated by USMI and immunohistochemistry of CD31 and VEGFR2 and did not reveal differences in perfusion or VEGFR2 expression in the absence or after the triggered release of liposomes. USMI can provide precise guidance for ultrasound-triggered release of liposomal doxorubicin mediated by a confocal ultrasound device; moreover, the combination of B-mode imaging and USMI can help to follow the response of the tumor to the therapy.

Unaltered IL-2 encapsulated in acoustically active lipid microspheres for systemic but targeted microdose delivery to tumor microenvironment.

e14535 Background: In order to take local advantage of exogenous interleukin-2 (IL-2) on effector T-cells within the tumor microenvironment while simultaneously avoiding systemic Treg immunosuppressive effects, microdoses of recombinant human IL-2 (rhIL-2) were encapsulated in gas-filled lipid microspheres (eIL-2), then activated with ultrasound. This novel therapeutic agent (eIL-2) was selectively delivered to the tumor via sonoporation and its anti-tumor effects were determined alone and in combination with PD-1 blockade. Methods: In an MC38 colon cancer model, jugular button catheters (Instech) were surgically implanted in a total of 56 animals (8 animals per arm) prior to tumor inoculation to facilitate repeatable IV injection of both anti-PD-1 (RMP1-14; BioXCell) and microspheres. Imagent perflexane lipid microspheres were incubated with rhIL-2 and the high concentration infranatant was separated, discarded, and replaced with sterile saline to resuspend microspheres to formulate eIL-2 on-site. Tumor-bearing mice were dosed on Days 1, 4, 8, and 12. Ultrasound (US) settings used were 2.2 MHz frequency, and 0.339 mechanical index (MI) during insonation. Once every 10 seconds a microbubble destruct pulse of 1.304 MI lasting 1,100 milliseconds was applied. Total insonation time was 5 minutes using a commercial ultrasound scanner (Mindray TE7) operating within diagnostically safe exposure limits. Study groups included Group 1: no treatment; Group 2: aPD-1, 3 mg/kg; Group 3: aPD-1, 3 mg/kg, Imagent + US; Group 4: Free rhIL-2, 10,000 IU (0.61μg)/animal; Group 5: eIL-2, approximately 0.2 μg encapsulated/animal; Group 6: Free rhIL-2, 10,000 IU (0.61μg)/animal, aPD-1, 3 mg/kg; Group 7: eIL-2, approximately 0.1 μg encapsulated/animal, aPD-1, 3 mg/kg. Results: The anti-PD-1 dose of 3 mg/kg demonstrated an expected tumor growth inhibition over control of -38.2% on Day 6, -35.6% on Day 8 and -30.3% on Day 12. Adding eIL-2 + ultrasound external stimuli approximately doubled the tumor inhibition effect of RMP1-14 to -68.1% on Day 6, -69.2% on Day 8 and -62.0% on Day 12. We also analyzed cytokine levels in the peripheral blood (Day 12) using a multiplex ELISA and observed elevated levels of pro-inflammatory cytokines including IFN-g, IL-12, and IL-1a, which likely serve to enhance anti-tumor immunity. IL-15 was also increased following treatment, which supports effector T cell survival. Conclusions: Using a novel form of recombinant human interleukin-2 encapsulated within a gas-filled lipid microsphere, we demonstrated that ultrasound-activated local delivery via sonoporation plus systemic PD-1 blockade led to improved tumor control and increased expression of pro-inflammatory cytokines. This novel approach enhances the efficacy of checkpoint blockade for the treatment of solid tumors. Further experiments are underway to interrogate mechanisms of action.

Development of local anesthetic drug delivery system by administration of organo-silica nanoformulations under ultrasound stimuli: in vitro and in vivo investigations

The development of local anesthetic (LA) system is the application of commercial drug for the pain management that indorses the reversible obstructive mechanism of neural transmission through preventing the innervation process in human peripheral nerves. Ropivacaine (RV) is one of the greatest frequently used LA s with the actions of long-lasting and low-toxicity for the post-operative pain management. In this work, we have approached novel design and development of glycosylated chitosan (GCS) encapsulated mesoporous silica nanoparticles (GCS-MONPs)-based nano-scaffold for sustainable distributions and controlled/supported arrival of stacked RV for targeting sites, which can be activated by either outer ultrasound activating to discharge the payload, foundation on-request and dependable analgesia. The structural and morphology analyses result established that prepared nano-formulations have successful molecular interactions and RV loaded spherical morphological structures. The drug release profile of developed nanostructure with ultrasound-activation has been achieved 50% of drug release in 2 h and 90% of drug release was achieved in 12 h, which displays more controlled release when compared to free RV solution. The in vitro cell compatibility analysis exhibited GCS-MONPs with RV has improved neuron cell survival rates when compared to other samples due to its porous surface and suitable biopolymer proportions. The analysis of ex vitro and in vivo pain relief analysis demonstrated treated animal models have high compatibility with GCS-MONPs@RV, which was confirmed by histomorphology. This developed MONPs based formulations with ultrasound-irradiation gives a prospective technique to clinical agony the board through on-request and dependable help with discomfort.

Low-intensity ultrasound combined with allogenic adipose-derived mesenchymal stem cells (AdMSCs) in radiation-induced skin injury treatment

Mesenchymal stem cells are mechano-sensitive cells with the potential to restore the function of damaged tissues. Low-intensity ultrasound has been increasingly considered as a bioactive therapeutic apparatus. Optimizing transplantation conditions is a critical aim for radiation-induced skin tissue injury. Therefore, the therapeutic function of adipose-derived mesenchymal stem cells to ultrasound stimulus was examined based on the mechanical index (MI). Mesenchymal stem cells were isolated from the adipose tissues of mature guinea pigs. An ultrasound system (US) was constructed with a 40 kHz frequency. The radiation-induced skin injury model was produced on the abdominal skin of guinea pigs by 60 Gy of radiation. Then, they were divided to 7 groups (n = 42): control, sham, US (MI = 0.7), AdMSCs injection, US AdMSCs (AdMSCs, under US with MI = 0.2), AdMSCs + US (AdMSCs transplantation and US with MI = 0.7) and US AdMSCs + US (combining the last two groups). The homing of stem cells was verified with fluorescence imaging. The groups were followed with serial photography, ultrasound imaging, tensiometry, and histology. The thickness of the skin was analyzed. Functional changes in skin tissue were evaluated with Young’s modulus (kPa). One-way ANOVA tests were performed to analyze differences between treatment protocols (p < 0.05). The results of Kumar’s score showed that radiation injury was significantly lower in the treatment groups of US AdMSCs and US AdMSCs + US than other groups after 14 days (p < 0.05). There was a significant difference in skin thickness between treatment groups with control, sham, and US groups after 60 Gy radiation and were closer to the thickness of healthy skin. Young’s modulus in US AdMSCs + US, US AdMSCs, and AdMSCs + US groups demonstrated a significant difference with the other groups (p < 0.05). Young’s modulus in US AdMSCs + US and US AdMSCs treatment groups were closer to Young’s modulus of the healthy skin. The histological results confirmed the improvement of acute radiation damage in the combined treatment method, especially in US AdMSCs + US and US AdMSCs groups with increasing the epithelialization and formation of collagen. An ultrasonic treatment plan based on a mechanical index of the target medium could be used to enhance stem cell therapy.

Dandelion‐Like Microswarms: Ultrafast Growth and Locomotion of Dandelion‐Like Microswarms with Tubular Micromotors (Small 38/2020)

In article number 2003678, Xiaolong Lu, Wenjuan Liu, and co‐workers report dandelion‐like microswarms assembled from tubular micromotors, which are capable of performing ultrafast growth and locomotion. With the ultrasound oscillation of self‐generated bubbles, such microswarms could move at an average speed of up to 50 mm s−1 and exhibit an instant and wireless response to ultrasound stimuli.

Ultrasound-Responsive Carriers for Therapeutic Applications.

Ultrasound (US)-responsive carriers have emerged as promising theranostic candidates because of their ability to enhance US-contrast, promote image-guided drug delivery, cause on-demand pulsatile release of drugs in response to ultrasound stimuli, as well as to enhance the permeability of physiological barriers such as the stratum corneum, the vascular endothelium, and the blood-brain barrier (BBB). US-responsive carriers include microbubbles MBs, liposomes, droplets, hydrogels, and nanobubble-nanoparticle complexes and have been explored for cavitation-mediated US-responsive drug delivery. Recently, a transient increase in the permeability of the BBB by microbubble (MB)-assisted low-frequency US has shown promise in enhancing the delivery of therapeutic agents in the case of neurological disorders. Further, the periodic mechanical stimulus generated by US-responsive MBs have also been explored in tissue engineering and has directly influenced the differentiation of mesenchymal stem cells into cartilage. This Review discusses the various types of US-responsive carriers and explores their emerging roles in therapeutics ranging from drug delivery to tissue engineering.

Ultrasound-induced deformation of PLGA-microPlates for on-command drug release

Transdermal drug delivery offers several advantages over other conventional modalities for drug administration, such as injections and oral administrations. It can be activated by exogenous energy sources, including electric and magnetic fields, or by light and ultrasound (US). Ultrasound can induce the degradation and deformation of a polymeric matrix, thus promoting the release of entrapped drugs and the topical administration through the skin. Our aim is to create a wearable patch composed of an ultrasound-responsive polymeric system encapsulating specific drugs, which are released on demand by the application of ultrasound. In this work, we investigate the effect of ultrasound on square poly(lactic-co-glycolic acid) (PLGA) microparticles loaded with curcumin (CURC), called curcumin-microplates (CURC-μPLs), realized using a top-down fabrication process. Using Finite Element Method (FEM) simulations, we identified the resonant frequencies and the mode shape of the μPLs. Guided by this simulation, we applied ultrasound stimulus at frequency of 1 MHz, close to the first mechanical resonance frequency of the microplates, leading to a 200% increase in CURC release rate after 30 min of ultrasonic treatment. This approach can be generalized to any ultrasound-sensitive matrix filled with specific drugs and with piezoelectric compliant transducers embedded in the smart patch for generating ultrasonic waves.

Double security drug delivery system DDS constructed by multi-responsive (pH/redox/US) microgel

In this paper, the multi-responsive core-shell microgels were prepared for constructing a double-locked drug delivery system. The pH- sensitive poly(2-(diisopropylamino ethylmethacry-late)-block-poly(ethyleneimine) diblock copolymers (PDPA-b-PEI) were synthesized and used to prepare micelles through their self-assembly in neutral solution. Redox-responsive gel shells were formed by Michael addition of primary amine group of branched PEI using disulfide as a cross-linker, which was specifically cleaved by glutathione (GSH). Anticancer drug doxorubicin DOX and perfluorohexane (PFH) could be encapsulated in the core of microgel. The DOX was released sustainably only under the condition of pH and GSH were both right. For example, under neutral condition with GSH, DOX could not release swimmingly due to the core of microgels was in hydrophobic state and wrapped the DOX firmly, although the gel shells were collapsed by GSH. When exposed to ultrasound, the drug released abruptly and achieved a complete release instantly. Moreover, it was found that the structure of the microgels was not destroyed after the ultrasound stimulus but had undergone an expansion-recovery process. Finally, it was demonstrated that the microgel had a “double security” effect, ensuring the low drug leakage during the normal blood circulation and efficient drug release under the pH/redox/ultrasound stimulus. The multi-responsive microgels designed here, which combines the usage of both endogenous and exogenous stimuli, has the advantages of low side-effect, high spatiotemporal controllability and complete release.

Non‐invasive Neuromodulation Using Ultrasound

The discovery of light sensitive proteins led to the development of optogenetics and allowed the precise manipulation of neuronal and non‐neuronal cells. This technique uses particular wavelengths of light to manipulate both neuronal and non‐neuronal cells [2, 5]. It has enabled the study of information processing in the brain and recent studies are looking into clinical translational applications of the technique [1]. Despite the advantages offered by optegenetics, it has the drawback of being invasive as light does not penetrate skin past a few millimeters. It is not possible to target deep tissue within the body using this technique and this limits the application in the context of diseases such as Parkinson’s [3] or heart malfunction [4].We are developing devices that can non‐invasively manipulate cells using a technique termed “sonogenetics”. This technique uses a combination of engineering cells to be more sensitive to mechanical stimuli as well as developing ultrasound transducers capable of stimulating cells in freely moving, awake mice. We demonstrate the development of miniature transducers made from non‐hysteretic single crystal lithium niobate to be used for the development of sonogenetics. In addition, we o er mathematical insights to the mechanism of action of ultrasound on neurons. Our analysis of membrane deflection enables us to predict cellular activity based on the applied ultrasound stimulus. By extension, we use this analytical framework to inform the development of transducers and stimulation parameters for achieving non‐invasive stimulation of cells.Support or Funding InformationWM Keck FoundationNational Institute of HealthMembrane Deflection and Capacitance Change due to Ultrasounda–d) Membrane deflection due to an ultrasound stimulus, with parameters 7 MHz and 1 MPa pressure. The stimulus is provided for 10 ms, the resulting area change(e) and the capacitance (f) are then calculated from the input parameters. The value of capacitance generated in this model is then used in a Hodgkin‐Huxley neuron model to determine action potential generation.Figure 1a) LN transducer housed in a MMCX coaxial connector designed for long term behavioral studies in awake, freely‐moving mice. b) Device mounted on a mouse skull to be used for characterization using an automated hydrophone setup (c). d)Pressure profile over the transducer face with a 450 mV input results in up to 2 MPa pressures. e) Transducer attached to mouse skull for long term behavioral studies.Figure 2

An Li+-enriched Co2+-induced metallogel: a study on thixotropic rheological behaviour and conductance.

An alkali base and counterion-selective red metallogel (1% w/v) has been synthesized by mixing the adipic acid-derived ligand H2AL with LiOH, followed by the addition of 1 equivalent of Co(OAc)2 in DMF. The addition of Co(OAc)2 not only resulted in the formation of a 2 : 2 (M : L) complex, but also led to the consecutive steps of aggregation, fiber creation, entrapment of the solvent and eventually gelation. The metallogel formation and the mechanism behind gelation have been well characterized and established using various instrumental techniques such as FTIR spectroscopy, UV-vis spectroscopy, FE-SEM, TEM, PXRD, ESI-mass spectrometry, Job's plot and rheology analysis. Nyquist plots suggested a large decrease in the resistance value from 11.3 kΩ to 4.2 kΩ for the solution obtained from the ligand deprotonated by LiOH (AL2-) and Co(OAc)2 containing the metallogel. The Nyquist plot and resistance of the metallogel have also been studied under the influence of temperature and ultrasound stimuli. The extensive rheological measurements provide information about the strength of the gel network and the highly reversible nature and thixotropic behaviour of the metallogel.