Acoustic-holography-patterned primary hepatocytes possess liver functions.

Acoustic holography (AH), a promising approach for cell patterning, emerges as a powerful tool for constructing novel invitro 3D models that mimic organs and cancers features. However, understanding changes in cell function post-AH remains limited. Furthermore, replicating complex physiological and pathological processes solely with cell lines proves challenging. Here, we employed acoustical holographic lattice to assemble primary hepatocytes directly isolated from mice into a cell cluster matrix to construct a liver-shaped tissue sample. For the first time, we evaluated the liver functions of AH-patterned primary hepatocytes. The patterned model exhibited large numbers of self-assembled spheroids and superior multifarious core hepatocyte functions compared to cells in 2D and traditional 3D culture models. AH offers a robust protocol for long-term in vitro culture of primary cells, underscoring its potential for future applications in disease pathogenesis research, drug testing, and organ replacement therapy.

Acoustothermal transfection for cell therapy.

Transfected stem cells and T cells are promising in personalized cell therapy and immunotherapy against various diseases. However, existing transfection techniques face a fundamental trade-off between transfection efficiency and cell viability; achieving both simultaneously remains a substantial challenge. This study presents an acoustothermal transfection method that leverages acoustic and thermal effects on cells to enhance the permeability of both the cell membrane and nuclear envelope to achieve safe, efficient, and high-throughput transfection of primary T cells and stem cells. With this method, two types of plasmids were simultaneously delivered into the nuclei of mesenchymal stem cells (MSCs) with efficiencies of 89.6 ± 1.2%. CXCR4-transfected MSCs could efficiently target cerebral ischemia sites in vivo and reduce the infarct volume in mice. Our acoustothermal transfection method addresses a key bottleneck in balancing the transfection efficiency and cell viability, which can become a powerful tool in the future for cellular and gene therapies.

Portal Vein Pressure Estimation and Portal Hypertension Discrimination Based on Subharmonic Scattering of Ultrasound Contrast Agent Microbubbles.

OBJECTIVE: The acquisition of real-time portal vein pressure (PVP) is important for portal hypertension (PH) discrimination to monitor disease progress and select treatment options. To date, the PVP evaluation approaches are either invasive or noninvasive but with less stability and sensitivity. METHODS: We customized an open ultrasound scanner to explore in vitro and in vivo the ultrasound contrast agent SonoVue microbubbles' subharmonic characteristics with acoustic pressure and local ambient pressure, and obtained promising results of PVP measurements in canine models with induced PH by ligation or embolization of portal vein. RESULTS: In in vitro experiments, the highest correlations between the subharmonic amplitude of SonoVue microbubbles and ambient pressure were observed at acoustic pressures of 523 kPa and 563 kPa (r = -0.993, -0.993, P<0.05, respectively). The correlation coefficients between absolute subharmonic amplitudes and PVP (10.7-35.4 mmHg) were the highest among existing studies using microbubbles as pressure sensors (r values ranged from -0.819 to -0.918). The PH (>16 mmHg) diagnostic capacity also achieved a high level (563 kPa, sensitivity = 93.3%, specificity = 91.7%, accuracy = 92.6%). CONCLUSION: This study proposes a promising measurement for PVP with the highest accuracy, sensitivity, and specificity in an in vivo model compared to existing studies. Future investigations are planned to assess the feasibility of this technique in clinical practice. SIGNIFICANCE: This is the first study that comprehensively investigates the role of the subharmonic scattering signals from SonoVue microbubbles in evaluating PVP in vivo. It represents a promising alternative to invasive measurements for portal pressure.

[Experimental study on high-frequency subharmonic scattering characteristics of ultrasound contrast agent microbubbles under low ambient pressure].

Correlation between nonlinear subharmonic scattering of ultrasound contrast agent microbubbles and ambient pressure is expected to be used for local brain tissue pressure monitoring. Although high-frequency ultrasound has achieved high-resolution imaging of intracranial microvessels, the research on high-frequency subharmonic scattering characteristics of microbubbles is insufficient at present, which restricts the research progress of estimating local brain tissue pressure based on high-frequency subharmonic scattering of microbubbles. Therefore, under the excitation of 10 MHz high-frequency ultrasound, the effects of different acoustic pressures and ambient pressures on the high-frequency subharmonic scattering characteristics of three different ultrasound contrast agents including SonoVue, Sonazoid and Huashengxian were investigated in this in vitro study. Results showed that the subharmonic scattering amplitudes of the three microbubbles increased with the increase of ambient pressure at the peak negative acoustic pressures of 696, 766 and 817 kPa, and there was a favorable linear correlation between subharmonic amplitude and ambient pressure. Under the above three acoustic pressures, the highest correlation coefficient of SonoVue was 0.948 ( P = 0.03), the highest sensitivity of pressure measurement was 0.248 dB/mm Hg and the minimum root mean square error (RMSE) was 2.64 mm Hg. Sonazoid's highest correlation coefficient was 0.982 ( P < 0.01), the highest sensitivity of pressure measurement was 0.052 dB/mm Hg and the minimum RMSE was 1.51 mm Hg. The highest correlation coefficient of Huashengxian was 0.969 ( P = 0.02), the highest sensitivity of pressure measurement was 0.098 dB/mm Hg and the minimum RMSE was 2.00 mm Hg. The above in vitro experimental results indicate that by selecting ultrasound contrast agent microbubbles and optimizing acoustic pressure, the correlation between high-frequency subharmonic scattering of microbubbles and ambient pressure can be improved, the sensitivity of pressure measurement can be upgraded, and the measurement error can be reduced to meet the clinical demand for local brain tissue pressure measurement, which provided an important experimental basis for subsequent research in vivo.

Decorated bacteria-cellulose ultrasonic metasurface.

Cellulose, as a component of green plants, becomes attractive for fabricating biocompatible flexible functional devices but is plagued by hydrophilic properties, which make it easily break down in water by poor mechanical stability. Here we report a class of SiO2-nanoparticle-decorated bacteria-cellulose meta-skin with superior stability in water, excellent machining property, ultrathin thickness, and active bacteria-repairing capacity. We further develop functional ultrasonic metasurfaces based on meta-skin paper-cutting that can generate intricate patterns of ~10 µm precision. Benefited from the perfect ultrasound insulation of surface Cassie-Baxter states, we utilize meta-skin paper-cutting to design and fabricate ultrathin (~20 µm) and super-light (<20 mg) chip-scale devices, such as nonlocal holographic meta-lens and the 3D imaging meta-lens, realizing complicated acoustic holograms and high-resolution 3D ultrasound imaging in far fields. The decorated bacteria-cellulose ultrasonic metasurface opens the way for exploiting flexible and biologically degradable metamaterial devices with functionality customization and key applications in advanced biomedical engineering technologies.

Noninvasive Estimation of Tumor Interstitial Fluid Pressure from Subharmonic Scattering of Ultrasound Contrast Microbubbles.

The noninvasive estimation of interstitial fluid pressure (IFP) using ultrasound contrast agent (UCA) microbubbles as pressure sensors will provide tumor treatments and efficacy assessments with a promising tool. This study aimed to verify the efficacy of the optimal acoustic pressure in vitro in the prediction of tumor IFPs based on UCA microbubbles' subharmonic scattering. A customized ultrasound scanner was used to generate subharmonic signals from microbubbles' nonlinear oscillations, and the optimal acoustic pressure was determined in vitro when the subharmonic amplitude reached the most sensitive to hydrostatic pressure changes. This optimal acoustic pressure was then applied to predict IFPs in tumor-bearing mouse models, which were further compared with the reference IFPs measured using a standard tissue fluid pressure monitor. An inverse linear relationship and good correlation (r = -0.853, p < 0.001) existed between the subharmonic amplitude and tumor IFPs at the optimal acoustic pressure of 555 kPa, and pressure sensitivity was 1.019 dB/mmHg. No statistical differences were found between the pressures measured by the standard device and those estimated via the subharmonic amplitude, as confirmed by cross-validation (mean absolute errors from 2.00 to 3.09 mmHg, p > 0.05). Our findings demonstrated that in vitro optimized acoustic parameters for UCA microbubbles' subharmonic scattering can be applied for the noninvasive estimation of tumor IFPs.

Correlation Between Portal Vein Pressure and Subharmonic Scattering Signals From SonoVue Microbubbles in Canines.

The current gold standard for the clinical diagnosis of portal hypertension (PH) is an invasive and indirect estimation of portal vein pressure (PVP). Therefore, the need for a non-invasive PVP measurement method is urgent. Subharmonic scattering of ultrasound contrast agent (UCA) microbubbles is under investigation in clinical research as a pressure indicator. However, the driving acoustic pressure must be optimized to improve the ambient pressure sensitivity of the subharmonic amplitude for different UCAs. In this study, for the first time, we obtained the relationship between the PVP and the amplitude of the subharmonic signal scattered from SonoVue microbubbles by using two canines to build the PH model. The results revealed a desirable linear correlation between the subharmonic amplitude and PVP (<20 mmHg) at the incident acoustic pressure of 453 kPa (r = -0.910, p < 0.005; sensitivity: -2.003 dB/mmHg); this was one order of magnitude higher in sensitivity than that of the in vitro case with a detectable pressure variation of approximately 1 mmHg. This indicates the feasibility of using UCA microbubbles to accurately measure low ambient pressures in vivo and further exhibits the potential of the method for non-invasive pressure estimation in clinical applications.

Phononic-Crystal-Based Particle Sieving in Continuous Flow: Numerical Simulations.

Sieving specific particles from mixed samples is of great value in fields such as biochemistry and additive manufacturing. In this study, a particle sieving method for microfluidics was proposed based on a phononic crystal plate (PCP), the mechanism of which originates from the competition between the trapping effect of the resonant PCP-induced acoustic radiation force (ARF), disturbance effect of acoustic streaming (AS), and flushing effect of the continuous inlet flow on particles suspended in microfluidic channels. Specifically, particles with different sizes could be separated under inlet flow conditions owing to ARF and AS drag forces as functions of the particle diameter, incident acoustic pressure, and driving frequency. Furthermore, a comprehensive numerical analysis was performed to investigate the impacts of ARF, AS, and inlet flow conditions on the particle motion and sieving efficiency, and to explore proper operating parameters, including the acoustic pressure and inlet flow velocity. It was found that, for each inlet flow velocity, there was an optimal acoustic pressure allowing us to achieve the maximum sieving efficiency, but the sieving efficiency at a low flow velocity was not as good as that at a high flow velocity. Although a PCP with a high resonant frequency could weaken the AS, thereby suiting the sieving of small particles (<5 µm), a low channel height corresponding to a high frequency limits the throughput. Therefore, it is necessary to design a PCP with a suitable resonant frequency based on the size of the particles to be sieved. This investigation can provide guidance for the design of massive acoustic sorting mi-crofluidic devices based on phononic crystals or acoustic metamaterials under continuous flow.

Inverse solution of corneal material parameters based on non-contact tonometry: A comparative study of different constitutive models.

Assessing the biomechanical properties of the cornea in vivo is important for predicting the outcome of refractive surgery, and for controlling the risk of postoperative complications. In this study, we examined the impact of corneal mechanical properties (nonlinearity and anisotropy) on the inverse solution of corneal material parameters based on the non-contact tonometry ("air puff") test. Finite element models with different constitutive models (linear-elastic, isotropic hyperelastic, and fiber-dependent) were established to simulate the non-contact tonometry test. The results showed that the corneal nonlinear mechanical property and fiber distribution had significant effects on the corneal deflection profile. These findings may help in constructing an appropriate inverse solution strategy when using the inverse finite element method and in identifying individual differences in the corneal matrix shear modulus and fiber stiffness.

Characterization of hyperelastic mechanical properties for youth corneal anterior central stroma based on collagen fibril crimping constitutive model.

To relate the crimping morphology of collagen fibrils to macroscopic hyperelastic responses, a four-parameter collagen fibril crimping constitutive model was developed that characterizes the hyperelastic mechanical properties of ex vivo corneal anterior central stroma from youth patients. The collagen fibril crimping degrees of the corneal stroma follow a Gaussian distribution as observed by transmission electron microscopy of the lenticules extracted from human corneas by small incision lenticule extraction (SMILE) refractive surgery. The hyperelastic parameters of pairs of corneal lenticules from 60 youth myopic patients were determined by tensile stress-stretch curves combined with individual surgical geometric features. The model, whose parameters reflect the corresponding mechanical responses, effectively describes each mechanical deformation process especially the physiological corneal deformation range. The constitutive model was embedded into a UMAT subroutine of the finite element software ABAQUS to simulate the tensile behavior of the corneal stroma, and the differences between individuals was excluded in the statistical analysis. The stromal hyperelastic properties in the two fibril preferential directions were shown to be the same. Although there was no correlation with the degree of corneal myopia, the hyperelastic mechanical properties of both the matrix and collagen fibrils decreased with increasing corneal stromal depth. The results not only have significance for SMILE refractive surgery by elucidating the biomechanical properties of a stromal surgical region but are also conducive to the future biomechanical exploration of the whole human cornea.