A dynamical model of oncotripsy by mechanical cell fatigue: selective cancer cell ablation by low-intensity pulsed ultrasound

A review on L-methioninase in cancer therapy: Precision targeting, advancements and diverse applications for a promising future

Cancer remains a global health challenge, demanding novel therapeutic options due to the debilitating side effects of conventional treatments on healthy tissues. The review highlights the potential of L-methioninase, a pyridoxal-5-phosphate (PLP)-dependent enzyme, as a promising avenue in alternative cancer therapy. L-methioninase offers a unique advantage, its ability to selectively target and inhibit the growth of cancer cells without harming healthy cells. This selectivity arises because tumor cells lack an essential enzyme called methionine synthase, which healthy cells use to make the vital amino acid L-methionine. Several sources harbor L-methioninase, including bacteria, fungi, plants, and protozoa. Future research efforts can explore and exploit this diverse range of sources to improve the therapeutic potential of L-methioninase in the fight against cancer. Despite challenges, research actively explores microbial L-methioninase for its anticancer potential. This review examines the enzyme's side effects, advancements in combination therapies, recombinant technologies, polymer conjugation and novel delivery methods like nanoparticles, while highlighting the success of oral administration in preclinical trials. Beyond its promising role in cancer therapy, L-methioninase holds potential applications in food science, antioxidants, and various health concerns like diabetes, cardiovascular issues, and neurodegenerative diseases. This review provides a piece of current knowledge and future prospects of L-methioninase, exploring its diverse therapeutic potential.

Focused Ultrasound for Dermal Applications

Focused ultrasound (FUS) is emerging as one of the most promising, non-invasive treatment techniques. The advancement of transducer technology has paved the way for dermatological applications. A comprehensive review is presented for healthcare practitioners and researchers, summarizing the effect of various operational parameters on the injury zone produced by ultrasound beams for various dermatological applications, which include skin tightening, fat reduction, hyperpigmentation and cancer treatment. In this article, we aim to highlight the efficient operational parameters of FUS to enhance pain relief during surgery and its affordability for skin treatment. Finally, a prospective future technique for efficient FUS is discussed.

Ultrasound-mediated nano-sized drug delivery systems for cancer treatment: Multi-scale and multi-physics computational modeling

Computational modeling enables researchers to study and understand various complex biological phenomena in anticancer drug delivery systems (DDSs), especially nano-sized DDSs (NSDDSs). The combination of NSDDSs and therapeutic ultrasound (TUS), that is, focused ultrasound and low-intensity pulsed ultrasound, has made significant progress in recent years, opening many opportunities for cancer treatment. Multiple parameters require tuning and optimization to develop effective DDSs, such as NSDDSs, in which mathematical modeling can prove advantageous. In silico computational modeling of ultrasound-responsive DDS typically involves a complex framework of acoustic interactions, heat transfer, drug release from nanoparticles, fluid flow, mass transport, and pharmacodynamic governing equations. Owing to the rapid development of computational tools, modeling the different phenomena in multi-scale complex problems involved in drug delivery to tumors has become possible. In the present study, we present an in-depth review of recent advances in the mathematical modeling of TUS-mediated DDSs for cancer treatment. A detailed discussion is also provided on applying these computational models to improve the clinical translation for applications in cancer treatment. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Molecular insights into the effects of focused ultrasound mechanotherapy on lipid bilayers: Unlocking the keys to design effective treatments

Administration of focused ultrasounds (US) represents an attractive complement to classical therapies for a wide range of maladies, from cancer to neurological pathologies, as they are non-invasive, easily targeted, their dosage is easy to control, and they involve low risks. Different mechanisms have been proposed for their activity but the direct effect of their interaction with cell membranes is not well understood at the molecular level. This is in part due to the difficulty of designing experiments able to probe the required spatio-temporal resolutions. Here we use Molecular Dynamics (MD) simulations at two resolution levels and machine learning (ML) classification tools to shed light on the effects that focused US mechanotherapy methods have over a range of lipid bilayers. Our results indicate that the dynamic-structural response of the membrane models to the mechanical perturbations caused by the sound waves strongly depends on the lipid composition. The analyses performed on the MD trajectories contribute to a better understanding of the behavior of lipid membranes, and to open up a path for the rational design of new therapies for the long list of diseases characterized by specific lipid profiles of pathological membrane cells.

Selective Cell-Cell Adhesion Regulation via Cyclic Mechanical Deformation Induced by Ultrafast Nanovibrations

The adoption of dynamic mechanomodulation to regulate cellular behavior is an alternative to the use of chemical drugs, allowing spatiotemporal control. However, cell-selective targeting of mechanical stimuli is challenging due to the lack of strategies with which to convert macroscopic mechanical movements to different cellular responses. Here, we designed a nanoscale vibrating surface that controls cell behavior via selective repetitive cell deformation based on a poroelastic cell model. The vibrating indentations induce repetitive water redistribution in the cells with water redistribution rates faster than the vibrating rate; however, in the opposite case, cells perceive the vibrations as a one-time stimulus. The selective regulation of cell-cell adhesion through adjusting the frequency of nanovibration was demonstrated by suppression of cadherin expression in smooth muscle cells (fast water redistribution rate) with no change in vascular endothelial cells (slow water redistribution rate). This technique may provide a new strategy for cell-type-specific mechanical stimulation.

Mechanobiology of cancer cell responsiveness to chemotherapy and immunotherapy: Mechanistic insights and biomaterial platforms

Mechanical forces are central to how cancer treatments such as chemotherapeutics and immunotherapies interact with cells and tissues. At the simplest level, electrostatic forces underlie the binding events that are critical to therapeutic function. However, a growing body of literature points to mechanical factors that also affect whether a drug or an immune cell can reach a target, and to interactions between a cell and its environment affecting therapeutic efficacy. These factors affect cell processes ranging from cytoskeletal and extracellular matrix remodeling to transduction of signals by the nucleus to metastasis of cells. This review presents and critiques the state of the art of our understanding of how mechanobiology impacts drug and immunotherapy resistance and responsiveness, and of the in vitro systems that have been of value in the discovery of these effects.

A Quantitative Study of Thermal and Non-thermal Mechanisms in Ultrasound-Induced Nano-drug Delivery

OBJECTIVE

The primary objective of this study was to quantify the contributions to drug release for thermal and non-thermal mechanisms in ultrasound-induced release from gold nanoparticles (GNPs) for the first time.

METHODS

We studied doxorubicin (DOX) and curcumin release from the surface of GNPs using two different methods to induce drug release in an ex vivo tissue model: (i) localized tissue heating with a water bath and (ii) low-intensity pulsed ultrasound (LIPUS) exposure. Both methods have similar temperature profiles and can induce the release of both hydrophobic (curcumin) and hydrophilic (DOX) drugs from the surface of GNPs. Quantitative drug release in both cases was compared via fluorescence measurements.

DISCUSSION

The water bath heating method induced drug release using thermal effects only, whereas LIPUS exposure induced drug release used a combination of thermal and non-thermal mechanisms. It was found that there were increases of 70 ± 16% (curcumin) and 127 ± 20% (DOX) in drug release when LIPUS was used to induce drug release (both thermal and non-thermal mechanisms) as compared with the water bath (thermal mechanisms only) mediated release.

CONCLUSION

We determined that non-thermal mechanisms account for 41 ± 3% of curcumin release and 56 ± 4% of DOX release. It was concluded that in our ex vivo tissue model, the non-thermal mechanisms play a significant role in LIPUS-induced drug release from GNP drug carriers and that the contributions of non-thermal mechanisms to drug release depend on the type of anticancer drug loaded on the GNP surface.

Suppressing cancer by damaging cancer cell DNA using LED irradiation

BACKGROUND

High-energy irradiation eliminates cancer cells by destroying their genetic components. However, there are several side effects from doing this, such as fatigue, dermatitis, and hair loss, which remain obstacles to this treatment. Here, we propose a moderate method that uses low-energy white light from a light-emitting diode (LED) to selectively inhibit cancer cell proliferation without affecting normal cells.

METHODS

The association between LED irradiation and cancer cell growth arrest was evaluated based on cell proliferation, viability, and apoptotic activity. Immunofluorescence, polymerase chain reaction, and western blotting were performed in vitro and in vivo to identify the metabolism related to the inhibition of HeLa cell proliferation.

RESULTS

LED irradiation aggravated the defective p53 signaling pathway and induced cell growth arrest in cancer cells. Consequently, cancer cell apoptosis was induced by the increased DNA damage. Additionally, LED irradiation inhibited the proliferation of cancer cells by suppressing the MAPK pathway. Furthermore, the suppression of cancer growth by the regulation of p53 and MAPK was observed in cancer-bearing mice irradiated with LED.

CONCLUSIONS

Our findings suggest that LED irradiation can suppress cancer cell activity and may contribute to preventing the proliferation of cancer cells after medical surgery without causing side effects.

Mechanotherapy in oncology: Targeting nuclear mechanics and mechanotransduction

Mechanotherapy is proposed as a new option for cancer treatment. Increasing evidence suggests that characteristic differences are present in the nuclear mechanics and mechanotransduction of cancer cells compared with those of normal cells. Recent advances in understanding nuclear mechanics and mechanotransduction provide not only further insights into the process of malignant transformation but also useful references for developing new therapeutic approaches. Herein, we present an overview of the alterations of nuclear mechanics and mechanotransduction in cancer cells and highlight their implications in cancer mechanotherapy.

Mechanotransduction in tumor dynamics modeling

Mechanotherapy is a groundbreaking approach to impact carcinogenesis. Cells sense and respond to mechanical stimuli, translating them into biochemical signals in a process known as mechanotransduction. The impact of stress on tumor growth has been studied in the last three decades, and many papers highlight the role of mechanics as a critical self-inducer of tumor fate at the in vitro and in vivo biological levels. Meanwhile, mathematical models attempt to determine laws to reproduce tumor dynamics. This review discusses biological mechanotransduction mechanisms and mathematical-biomechanical models together. The aim is to provide a common framework for the different approaches that have emerged in the literature from the perspective of tumor avascularity and to provide insight into emerging mechanotherapies that have attracted interest in recent years.

On the potential biological impact of radiation-induced acoustic emissions during ultra-high dose rate electron radiotherapy: a preliminary study

Ionizing radiation pulses delivered at ultra-high dose rates in emerging FLASH radiotherapy can result in high-intensity low-frequency thermoacoustic emissions that may have a biological impact. This study aims at providing insights into the thermoacoustic emissions expected during FLASH radiotherapy and their likelihood of inducing acoustic cavitation. The characteristics of acoustic waves induced by the energy deposition of a pulsed electron beam similar to previous pre-clinical FLASH radiotherapy studies and their propagation in murine head-like phantoms are investigated in-silico. The results show that the generated pressures are sufficient to produce acoustic cavitation due to resonance in the irradiated object. It suggests that thermoacoustics may, in some irradiation scenarios, contribute to the widely misunderstood FLASH effect or cause adverse effects if not taken into account at the treatment planning stage.

Fabrication, control, and modeling of robots inspired by flagella and cilia

Flagella and cilia are slender structures that serve important functionalities in the microscopic world through their locomotion induced by fluid and structure interaction. With recent developments in microscopy, fabrication, biology, and modeling capability, robots inspired by the locomotion of these organelles in low Reynolds number flow have been manufactured and tested on the micro-and macro-scale, ranging from medicalin vivomicrobots, microfluidics to macro prototypes. We present a collection of modeling theories, control principles, and fabrication methods for flagellated and ciliary robots.

Ultrasound and Nanomedicine for Cancer-Targeted Drug Delivery: Screening, Cellular Mechanisms and Therapeutic Opportunities

Cancer is a disease characterized by abnormal cell growth. According to a report published by the World Health Organization (WHO), cancer is the second leading cause of death globally, responsible for an estimated 9.6 million deaths in 2018. It should be noted that ultrasound is already widely used as a diagnostic procedure for detecting tumorigenesis. In addition, ultrasound energy can also be utilized effectively for treating cancer. By filling the interior of lipospheres with gas molecules, these particles can serve both as contrast agents for ultrasonic imaging and as delivery systems for drugs such as microbubbles and nanobubbles. Therefore, this review aims to describe the nanoparticle-assisted drug delivery system and how it can enhance image analysis and biomedicine. The formation characteristics of nanoparticles indicate that they will accumulate at the tumor site upon ultrasonic imaging, in accordance with their modification characteristics. As a result of changing the accumulation of materials, it is possible to examine the results by comparing images of other tumor cell lines. It is also possible to investigate ultrasound images for evidence of cellular effects. In combination with a precision ultrasound imaging system, drug-carrying lipospheres can precisely track tumor tissue and deliver drugs to tumor cells to enhance the ability of this nanocomposite to treat cancer.

Finite element modeling of alpha-helices and tropocollagen molecules with reference to the spike of SARS-CoV-2

The newly developed finite element modeling at the atomic scale was used to predict the static and dynamic response of the alpha-helix (AH) and tropocollagen (TC) protein fragments, the main building blocks of the spike of the SARS-CoV-2. The geometry and morphology of the spike's stalk and its connection to the viral envelope were determined from the combination of most recent Molecular Dynamics simulation and images of Cryo-Electron microscope. The stiffness parameters of the covalent bonds in the main chain of the helix were taken from the literature. The AH and TC were modeled using both beam elements (wire model) and shell elements (ribbon model) in finite element analysis to predict their mechanical properties under tension. The asymptotic stiffening features of AH and TC under tensile loading were revealed and compared with a new analytical solution. The mechanical stiffnesses under other loading conditions, including compression, torsion and bending were also predicted numerically and correlated with the results of the existing MD simulations and tests. The mode shapes and natural frequencies of the spike were predicted using the built FE model. The frequencies were shown to be within the safe range of 1-20 MHz routinely used for medical imaging and diagnosis by means of ultrasound. These results provide a solid theoretical basis for using ultrasound to study damaging coronavirus through transient and resonant vibration at large deformations.

Focused Ultrasound Treatment of a Spheroid In Vitro Tumour Model

Simple Summary

Ultrasound waves can be applied for diagnostic and therapeutic purposes. Focused ultrasound is approved for tissue ablation, e.g., in the treatment of uterine fibroids or essential tremors. Besides the non-invasive image-guided surgical intervention at temperatures above 55 °C, FUS is investigated in other fields like blood-brain barrier opening, hyperthermia, and neuromodulation. FUS offers potential as an adjuvant therapy in cancer treatment. Therefore, analysis of FUS effects on cancer cells is necessary. We performed studies on two human cancer cell line spheroids using a newly developed high-throughput in vitro FUS applicator with 32 individual transducers. This study aimed to perform basic experiments with a new in vitro FUS device on a 3D tumour model to acquire insight into the effects of FUS at the cellular level. These experiments may contribute to a better understanding and predictions of cancer treatment efficacy.

Abstract

Focused ultrasound (FUS) is a non-invasive technique producing a variety of biological effects by either thermal or mechanical mechanisms of ultrasound interaction with the targeted tissue. FUS could bring benefits, e.g., tumour sensitisation, immune stimulation, and targeted drug delivery, but investigation of FUS effects at the cellular level is still missing. New techniques are commonly tested in vitro on two-dimensional (2D) monolayer cancer cell culture models. The 3D tumour model—spheroid—is mainly utilised to mimic solid tumours from an architectural standpoint. It is a promising method to simulate the characteristics of tumours in vitro and their various responses to therapeutic alternatives. This study aimed to evaluate the effects of FUS on human prostate and glioblastoma cancer tumour spheroids in vitro. The experimental follow-up enclosed the measurements of spheroid integrity and growth kinetics, DNA damage, and cellular metabolic activity by measuring intracellular ATP content in the spheroids. Our results showed that pulsed FUS treatment induced molecular effects in 3D tumour models. With the disruption of the spheroid integrity, we observed an increase in DNA double-strand breaks, leading to damage in the cancer cells depending on the cancer cell type.

Ultrasound waves in tumors via needle irradiation for precise medicine

Grounded in the interdisciplinary crosstalk among physics and biological sciences, precision medicine-based diagnosis and treatment strategies have recently gained great attention for the actual applicability of new engineered approaches in many medical fields, particularly in oncology. Within this framework, the use of ultrasounds employed to attack cancer cells in tumors to induce possible mechanical damage at different scales has received growing attention from scholars and scientists worldwide. With these considerations in mind, on the basis of ad hoc elastodynamic solutions and numerical simulations, we propose a pilot study for in silico modeling of the propagation of ultrasound waves inside tissues, with the aim of selecting proper frequencies and powers to be irradiated locally through a new teragnostic platform based on Lab-on-Fiber technology, baptized as a hospital in the needle and already the object of a patent. It is felt that the outcomes and the related biophysical insights gained from the analyses could pave the way for envisaging new integrated diagnostic and therapeutic approaches that might play a central role in future applications of precise medicine, starting from the growing synergy among physics, engineering and biology.

Surf Therapy-Qualitative Analysis: Organization and Structure of Surf Programs and Requirements, Demands and Expectations of Personal Staff

Surf therapy is an increasingly popular method of mental health intervention. Although previous research documents the benefits of surf therapy for mental health, it is unclear how to navigate the organization structure of said program. This research project is a case study, where the case is an organization of our choice, in which we selected several respondents for each position. The primary study objective was to identify the principles of the surf therapy structure and describe its personnel make-up. The aim was to identify the processes in the organization, to establish their interconnectedness and outline the positives and negatives of their functioning. The respondent sample (n = 11) was composed of participants of a surf therapy program held in Great Britain, including staff (coordinator, surf instructor), volunteers, and clients. Data were collected through a semi-structured interview and analyzed using interpretative phenomenological analysis. Four main thematic clusters were identified (organization of surf therapy, surf therapy staff, surf session, and situations that may arise in surf therapy), as well as several other categories based on participants' experiences. The information obtained provides a new, as yet unexplored view of surf therapy, and can be used particularly in the development of new surf therapy programs.

Sonodynamic Effects of a Novel Ether-Group Modified Porphyrin Derivative Combined With Pulsed Low-Intensity Ultrasound on PC-9 Cells

Sonodynamic therapy (SDT) is a developing modality for cancer treatment based on the synergistic effect of ultrasound and chemical compounds which are known as sonosensitizers. The development of more efficient sonosensitizers has become an urgent issue in this field. In this study, a novel porphyrin derivative (BBTPP) mediated SDT was evaluated on PC-9 cells. Pulsed low-intensity ultrasound (PLIU) was used for its little thermal and mechanical damage. The accumulation of drugs in cells was evaluated through porphyrin fluorescence, and the cytotoxicity of BBTPP was evaluated using a cell counting kit-8 assay. The sonodynamic effect was investigated by Hoechst 33342/PI and Annexin V-FITC/PI double staining, which showed an apoptotic rate of 18.87% in the BBTPP-SDT group, as compared with 1.71%, 1.4%, 1.57%, 3.61%, 11.18% in the control, BBTPP, hematoporphyrin monomethyl ether (HMME), ultrasound, and HMME-SDT groups, respectively. The sono-toxic effect of BBTPP was significantly superior to HMME. Our results showed that BBTPP-SDT resulted in much higher intracellular reactive oxygen species (ROS) and lipid peroxidation levels which were evaluated by 2′,7′-dichlorodihydrofluorescein diacetate (H₂DCFDA) and Liperfluo assay, respectively. The expressions of Bax, Bcl-2, caspase-9, caspase-8, and cleaved caspase-3 proteins were evaluated to investigate the apoptotic mechanism of BBTPP-SDT. The results of this study showed that the combination of BBTPP and PLIU induced the generation of ROS, resulting in lipid peroxidation, and activated both the extrinsic and intrinsic apoptotic pathways of PC-9 cells. Our results also suggested that the ether group introduced in the side chain of porphyrin could enhance the sono-toxicity of porphyrin-based sensitizers under the sonication of PLIU. These results supported the possibility of BBTPP as a promising sonosensitizer, and an appropriate side chain could enhance the sono-sensitivity of porphyrins.

Ultrasound-Mediated Cancer Therapeutics Delivery using Micelles and Liposomes: A Review

BACKGROUND

Existing cancer treatment methods have many undesirable side effects that greatly reduce the quality of life of cancer patients.

OBJECTIVE

This review will focus on the use of ultrasound-responsive liposomes and polymeric micelles in cancer therapy.

METHODS

This review presents a survey of the literature regarding ultrasound-triggered micelles and liposomes using articles recently published in various journals, as well as some new patents in this field.

RESULTS

Nanoparticles have proven promising as cancer theranostic tools. Nanoparticles are selective in nature, have reduced toxicity, and controllable drug release patterns making them ideal carriers for anticancer drugs. Numerous nanocarriers have been designed to combat malignancies, including liposomes, micelles, dendrimers, solid nanoparticles, quantum dots, gold nanoparticles, and, more recently, metal-organic frameworks. The temporal and spatial release of therapeutic agents from these nanostructures can be controlled using internal and external triggers, including pH, enzymes, redox, temperature, magnetic and electromagnetic waves, and ultrasound. Ultrasound is an attractive modality because it is non-invasive, can be focused on the diseased site, and has a synergistic effect with anticancer drugs.

CONCLUSION

The functionalization of micellar and liposomal surfaces with targeting moieties and the use of ultrasound as a triggering mechanism can help improve the selectivity and enable the spatiotemporal control of drug release from nanocarriers.

Enhanced tumor cell killing by ultrasound after microtubule depolymerization

Recent studies show that tumor cells are vulnerable to mechanical stresses and undergo calcium-dependent apoptosis (mechanoptosis) with mechanical perturbation by low-frequency ultrasound alone. To determine if tumor cells are particularly sensitive to mechanical stress in certain phases of the cell cycle, inhibitors of the cell-cycle phases are tested for effects on mechanoptosis. Most inhibitors show no significant effect, but inhibitors of mitosis that cause microtubule depolymerization increase the mechanoptosis. Surprisingly, ultrasound treatment also disrupts microtubules independent of inhibitors in tumor cells but not in normal cells. Ultrasound causes calcium entry through mechanosensitive Piezo1 channels that disrupts microtubules via calpain protease activation. Myosin IIA contractility is required for ultrasound-mediated mechanoptosis and microtubule disruption enhances myosin IIA contractility through activation of GEF-H1 and RhoA pathway. Further, ultrasound promotes contractility-dependent Piezo1 expression and localization to the peripheral adhesions where activated Piezo1 allows calcium entry to continue feedback loop. Thus, the synergistic action of ultrasound and nanomolar concentrations of microtubule depolymerizing agents can enhance tumor therapies.

Cell stiffness predicts cancer cell sensitivity to ultrasound as a selective superficial cancer therapy

We hypothesize that the biomechanical properties of cells can predict their viability, with Young's modulus representing the former and cell sensitivity to ultrasound representing the latter. Using atomic force microscopy, we show that the Young's modulus stiffness measure is significantly lower for superficial cancer cells (squamous cell carcinomas and melanoma) compared with noncancerous keratinocyte cells. In vitro findings reveal a significant difference between cancerous and noncancerous cell viability at the four ultrasound energy levels evaluated, with different cell lines exhibiting different sensitivities to the same ultrasound intensity. Young's modulus correlates with cell viability (R 2 = 0.93), indicating that this single biomechanical property can predict cell sensitivity to ultrasound treatment. In mice, repeated ultrasound treatment inhibits tumor growth without damaging healthy skin tissue. Histopathological tumor analysis indicates ultrasound-induced focal necrosis at the treatment site. Our findings provide a strong rationale for developing ultrasound as a noninvasive selective treatment for superficial cancers.

Hydraulic and electric control of cell spheroids

We use a theoretical approach to examine the effect of a radial fluid flow or electric current on the growth and homeostasis of a cell spheroid. Such conditions may be generated by a drain of micrometric diameter. To perform this analysis, we describe the tissue as a continuum. We include active mechanical, electric, and hydraulic components in the tissue material properties. We consider a spherical geometry and study the effect of the drain on the dynamics of the cell aggregate. We show that a steady fluid flow or electric current imposed by the drain could be able to significantly change the spheroid long-time state. In particular, our work suggests that a growing spheroid can systematically be driven to a shrinking state if an appropriate external field is applied. Order-of-magnitude estimates suggest that such fields are of the order of the indigenous ones. Similarities and differences with the case of tumors and embryo development are briefly discussed.

Dosage-controlled intracellular delivery mediated by acoustofluidics for lab on a chip applications

Biological research and many cell-based therapies rely on the successful delivery of cargo materials into cells. Intracellular delivery in an in vitro setting refers to a variety of physical and biochemical techniques developed for conducting rapid and efficient transport of materials across the plasma membrane. Generally, the techniques that are time-efficient (e.g., electroporation) suffer from heterogeneity and low cellular viability, and those that are precise (e.g., microinjection) suffer from low-throughput and are labor-intensive. Here, we present a novel in vitro microfluidic strategy for intracellular delivery, which is based on the acoustic excitation of adherent cells. Strong mechanical oscillations, mediated by Lamb waves, inside a microfluidic channel facilitate the cellular uptake of different size (e.g., 3-500 kDa, plasmid encoding EGFP) cargo materials through endocytic pathways. We demonstrate successful delivery of 500 kDa dextran to various adherent cell lines with unprecedented efficiency in the range of 65-85% above control. We also show that actuation voltage and treatment duration can be tuned to control the dosage of delivered substances. High viability (≥91%), versatility across different cargo materials and various adherent cell lines, scalability to hundreds of thousands of cells per treatment, portability, and ease-of-operation are among the unique features of this acoustofluidic strategy. Potential applications include targeting through endocytosis-dependant pathways in cellular disorders, such as lysosomal storage diseases, which other physical methods are unable to address. This novel acoustofluidic method achieves rapid, uniform, and scalable delivery of material into cells, and may find utility in lab-on-a-chip applications.

Effect of receptors on the resonant and transient harmonic vibrations of Coronavirus

The paper is concerned with the vibration characteristics of the Coronavirus family. There are some 25-100 receptors, commonly called spikes protruding from the envelope shell of the virus. Spikes, resembling the shape of a hot air balloon, may have a total mass similar to the mass of the lipid bi-layer shell. The lipid proteins of the virus are treated as homogeneous elastic material and the problem is formulated as the interaction of thin elastic shell with discrete masses, modeled as short conical cross-sectional beams. The system is subjected to ultrasonic excitation. Using the methods of structural acoustics, it is shown that the scattered pressure is very small and the pressure on the viral shell is simply the incident pressure. The modal analysis is performed for a bare shell, a single spike, and the spike-decorated shell. The predicted vibration frequencies and modes are shown to compare well with the newly derived closed-form solutions for a single spike and existing analytical solutions for thin shells. The fully nonlinear dynamic simulation of the transient response revealed the true character of the complex interaction between local vibration of spikes and global vibration of the multi-degree-of-freedom system. It was shown that harmonic vibration at or below the lowest resonant modes can excite large amplitude vibration of spikes. The associated maximum principal strain in a spike can reach large values in a fraction of a millisecond. Implications for possible tearing off spikes from the shell are discussed. Another important result is that after a finite number of cycles, the shell buckles and collapses, developing internal contacts and folds with large curvatures and strains exceeding 10%. For the geometry and elastic properties of the SARS-CoV-2 virus, these effects are present in the range of frequencies close to the ones used for medical ultrasound diagnostics.

A lesson from earthquake engineering for selectively damaging cancer cell structures

The progressive falling of barriers among disciplines is opening unforeseen scenarios in diagnosis and treatment of cancer diseases. By sharing models and mature knowledge in physics, engineering, computer sciences and molecular biology, synergistic efforts have in fact contributed in the last years to re-think still unsolved problems, shedding light on key roles of mechanobiology in tumors and envisaging new effective strategies for a precise medicine. The use of ultrasounds for altering cancer cells' program is one of the most attracting grounds to be explored in oncophysics, although how to administer mechanical energy to impair selected cell structures and functions simultaneously overcoming the critical trade-off between the impact of the cure and the patient risk still remains an open issue. Within this framework, by starting from the theoretical possibility of selectively attacking malignant cells by exploiting the stiffness discrepancies between tumor and healthy single cells, first proposed by Fraldi et al. (2015), we here investigate the in-frequency response of an overall spherical close-packing of geometrically equal polyhedral cells to gain insights into how mechanical resonance and vibration-induced failure phenomena can be oriented to destroy specific target units when both the cell populations coexist, as it happens for in vivo cases. Inspired by the dynamic action of earthquakes - which fracture only selected elements among adjacent ones in the same structure or damage individual constructions in contiguous buildings - we study the harmonic response of hierarchically architectured cell agglomerates, inhabited by both tumor and healthy cells that interact mutually throughout the extra-cellular matrix and whose cytoskeleton is modeled as a nonlinear soft-tensegrity structure. Numerical Finite Element results show that, at frequencies compatible with low intensity therapeutic ultrasounds, mechanical resonance and possible fatigue cycles of the pre-stressed actin filaments and microtubules can be selectively induced in cancer cells as a function of the global volume fraction of the cell species, paving the way for future engineered treatment protocols.

Implant resonance and the mechanostat theory: Applications of therapeutic ultrasound for porous metallic scaffolds

The development of treatment strategies for improving secondary stability at the bone-implant interface is a challenge. Porous implants are one solution for improving long-term implant stability, but the osteoconduction process of implants into the bone can be slow. Strain-driven osteogenesis from the mechanostat theory offers insight into pathways for post-operative treatment but mechanisms to deliver strain to the bone-implant interface need refinement. In this work, the use of therapeutic ultrasound is simulated to induce resonance into a porous implant structure. Local strains through the scaffold are measured by varying systemic variables such as damping ratio, applied vibrational force, primary bone-implant stability, and input frequency. At the natural frequency of the system with applied forces of 0.5 N and a damping ratio of 0.5%, roughly half of the nodes in the simulated environment exceed the microstrain threshold of 1000 με required for new bone formation. A high degree of sensitivity was noted upon changing input frequency, with minor sensitivities arising from damping ratio and applied vibrational force. These findings suggest that the application of therapeutic resonance to improve osseointegration of the bone-implant interface may be viable for applications including dental implants or segmental bone defects.

In Vivo Non-Thermal, Selective Cancer Treatment With High-Frequency Medium-Intensity Focused Ultrasound

Focused ultrasound (FUS) has proven its efficacy in non-invasive, radiation-free cancer treatment. However, the commonly used low-frequency high-intensity focused ultrasound (HIFU) destroys both cancerous and healthy tissues non-specifically through extreme heat and inertial cavitation with low spatial resolution. To address this issue, we evaluate the therapeutic effects of pulsed (60 Hz pulse repetition frequency, 1.45 ms pulse width) high-frequency (20.7 MHz) medium-intensity (spatial-peak pulse-average intensity I_SPPA < 279.1 W/cm², spatial-peak temporal-average intensity I_SPTA < 24.3 W/cm²) focused ultrasound (pHFMIFU) for selective cancer treatment without thermal damage and with low risk of inertial cavitation (mechanical index < 0.66), in an in vivo subcutaneous B16F10 melanoma tumor growth model in mice. The pHFMIFU with 104 μm focal diameter is generated by a microfabricated self-focusing acoustic transducer (SFAT) with a Fresnel acoustic lens. A three-axis positioning system has been developed for automatic scanning of the transducer to cover a larger treatment volume, while a water-cooling system is custom-built for dissipating non-acoustic heat from the transducer surface. Initial testing revealed that pHFMIFU treatment can be applied to a living animal while maintaining skin temperature under 35.6 °C without damaging normal skin and tissue. After eleven days of treatment with pHFMIFU, the treated tumors were significantly smaller with large areas of necrosis and apoptosis in the treatment field compared to untreated controls. Potential mechanisms of this selective, non-thermal killing effect, as well as possible causes of and solutions to the variation in treatment results, have been analyzed and proposed. The pHFMIFU could potentially be used as a new therapeutic modality for safer cancer treatment especially in critical body regions, due to its cancer-specific effects and high spatial resolution.

Sonodelivery in Skeletal Muscle: Current Approaches and Future Potential

There are currently multiple approaches to facilitate gene therapy via intramuscular gene delivery, such as electroporation, viral delivery, or direct DNA injection with or without polymeric carriers. Each of these methods has benefits, but each method also has shortcomings preventing it from being established as the ideal technique. A promising method, ultrasound-mediated gene delivery (or sonodelivery) is inexpensive, widely available, reusable, minimally invasive, and safe. Hurdles to utilizing sonodelivery include choosing from a large variety of conditions, which are often dependent on the equipment and/or research group, and moderate transfection efficiencies when compared to some other gene delivery methods. In this review, we provide a comprehensive look at the breadth of sonodelivery techniques for intramuscular gene delivery and suggest future directions for this continuously evolving field.

Focused Ultrasound Stimulates ER Localized Mechanosensitive PANNEXIN-1 to Mediate Intracellular Calcium Release in Invasive Cancer Cells

Focused ultrasound (FUS) is a rapidly developing stimulus technology with the potential to uncover novel mechanosensory dependent cellular processes. Since it is non-invasive, it holds great promise for future therapeutic applications in patients used either alone or as a complement to boost existing treatments. For example, FUS stimulation causes invasive but not non-invasive cancer cell lines to exhibit marked activation of calcium signaling pathways. Here, we identify the membrane channel PANNEXIN1 (PANX1) as a mediator for activation of calcium signaling in invasive cancer cells. Knockdown of PANX1 decreases calcium signaling in invasive cells, while PANX1 overexpression enhances calcium elevations in non-invasive cancer cells. We demonstrate that FUS may directly stimulate mechanosensory PANX1 localized in endoplasmic reticulum to evoke calcium release from internal stores. This process does not depend on mechanosensory stimulus transduction through an intact cytoskeleton and does not depend on plasma membrane localized PANX1. Plasma membrane localized PANX1, however, plays a different role in mediating the spread of intercellular calcium waves via ATP release. Additionally, we show that FUS stimulation evokes cytokine/chemokine release from invasive cancer cells, suggesting that FUS could be an important new adjuvant treatment to improve cancer immunotherapy.

A dynamical model of oncotripsy by mechanical cell fatigue: selective cancer cell ablation by low-intensity pulsed ultrasound

The method of oncotripsy, first proposed in Heyden & Ortiz (Heyden & Ortiz 2016 J. Mech. Phys. Solids 92, 164-175 (doi:10.1016/j.jmps.2016.04.016)), exploits aberrations in the material properties and morphology of cancerous cells in order to ablate them selectively by means of tuned low-intensity pulsed ultrasound. We propose the dynamical model of oncotripsy that follows as an application of cell dynamics, statistical mechanical theory of network elasticity and 'birth-death' kinetics to describe the processes of damage and repair of the cytoskeleton. We also develop a reduced dynamical model that approximates the three-dimensional dynamics of the cell and facilitates parametric studies, including sensitivity analysis and process optimization. We show that the dynamical model predicts-and provides a conceptual basis for understanding-the oncotripsy effect and other trends in the data of Mittelstein et al. (Mittelstein et al. 2019 Appl. Phys. Lett. 116, 013701 (doi:10.1063/1.5128627)), for cells in suspension, including the dependence of cell-death curves on cell and process parameters.

A dynamical model of oncotripsy by mechanical cell fatigue: selective cancer cell ablation by low-intensity pulsed ultrasound

The method of oncotripsy, first proposed in Heyden & Ortiz (Heyden & Ortiz 2016 J. Mech. Phys. Solids 92, 164-175 (doi:10.1016/j.jmps.2016.04.016)), exploits aberrations in the material properties and morphology of cancerous cells in order to ablate them selectively by means of tuned low-intensity pulsed ultrasound. We propose the dynamical model of oncotripsy that follows as an application of cell dynamics, statistical mechanical theory of network elasticity and 'birth-death' kinetics to describe the processes of damage and repair of the cytoskeleton. We also develop a reduced dynamical model that approximates the three-dimensional dynamics of the cell and facilitates parametric studies, including sensitivity analysis and process optimization. We show that the dynamical model predicts-and provides a conceptual basis for understanding-the oncotripsy effect and other trends in the data of Mittelstein et al. (Mittelstein et al. 2019 Appl. Phys. Lett. 116, 013701 (doi:10.1063/1.5128627)), for cells in suspension, including the dependence of cell-death curves on cell and process parameters.