Publications by authors named "Shaobao Liu"

17 Publications

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Effect of gene mutation of plants on their mechano-sensibility: the mutant of influences the buckling of trichomes.

Analyst 2021 Jul 22. Epub 2021 Jul 22.

The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, P.R. China. and Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, P.R. China.

With the development of molecular biology, more and more mutants of plants have been constructed, where gene mutants have been found to influence not only the biological processes but also biophysical behaviors of plant cells. Trichomes are an important appendage, which has been found to act as an active mechanosensory switch transducing mechanical signals into physiology changes, where the mechanical property of trichomes is vital for such functions. Up to now, over 40 different genes have been found with the function of regulating trichome cell morphogenesis; however, the effect of gene mutants on trichome mechanosensory function remains elusive. In this study, we found that EXO70H4, one of the most up-regulated genes in the mature trichome, not only affects the thickness of the trichome cell wall but also the mechanical property (i.e., the Young's modulus) of trichomes. Finite element method simulation results show that the buckling instability and stress concentration (e.g., exerted by insects) cannot occur on the base of the mutant exo70H4 trichome, which might further interrupt the mechanical signal transduction from branches to the base of trichomes. These results indicated that the mutant exo70H4 trichome might lack the ability to act as an active mechanosensory switch against chewing insect herbivores. Our findings provide new information about the effect of gene mutation (like crop mutants) on the mechano-sensibility and capability to resist the agricultural pests or lodging, which could be of great significance to the development of agriculture.
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http://dx.doi.org/10.1039/d1an00682gDOI Listing
July 2021

Characterizing poroelasticity of biological tissues by spherical indentation: an improved theory for large relaxation.

J Mech Phys Solids 2020 May 3;138. Epub 2020 Mar 3.

The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Shaanxi, 710049, P.R. China.

Flow of fluids within biological tissues often meets with resistance that causes a rate- and size-dependent material behavior known as poroelasticity. Characterizing poroelasticity can provide insight into a broad range of physiological functions, and is done qualitatively in the clinic by palpation. Indentation has been widely used for characterizing poroelasticity of soft materials, where quantitative interpretation of indentation requires a model of the underlying physics, and such existing models are well established for cases of small strain and modest force relaxation. We showed here that existing models are inadequate for large relaxation, where the force on the indenter at a prescribed depth at long-time scale drops to below half of the initially peak force (, (0)/() > 2). We developed an indentation theory for such cases of large relaxation, based on Biot theory and a generalized Hertz contact model. We demonstrated that our proposed theory is suitable for biological tissues (, spleen, kidney, skin and human cirrhosis liver) with both small and large relaxations. The proposed method would be a powerful tool to characterize poroelastic properties of biological materials for various applications such as pathological study and disease diagnosis.
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http://dx.doi.org/10.1016/j.jmps.2020.103920DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7595329PMC
May 2020

Vibration of a liquid-filled capillary tube.

J Mech Behav Biomed Mater 2020 06 26;106:103745. Epub 2020 Mar 26.

State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, PR China; State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'an Jiaotong University, Xi'an, 710049, PR China. Electronic address:

Liquid-filled capillary tubes are common structures in nature and engineering fields, which often function via vibration. Although liquid-solid interfacial tension plays important roles in the vibration behavior of the liquid-filled capillary tube, it remains elusive how the interfacial tension influences the natural frequency of capillary tube vibration. To address this, we developed a theory of beam-string structure to analyze the influence of liquid-solid interfacial tension on the vibration of a liquid-filled capillary cantilever. We used glass capillary tubes as a demo and experimentally validated the theory, where the reduced liquid-solid interfacial tension in a capillary tube decreases the natural frequencies of small-order modes. We then performed theoretical analysis and found that the change of elastocapillarity number, slenderness ratio and inner/outer radius ratio of capillary tubes enables: in higher order modes, a nonmonotonic change of natural frequency due to mode transformation between a beam and string; for lower order modes, decrease in the natural frequency to zero (increase from zero) due to mode disappearance (appearance). The developed theory would provide guidelines for high-accuracy design of capillary sensors.
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http://dx.doi.org/10.1016/j.jmbbm.2020.103745DOI Listing
June 2020

Translation of a Coated Rigid Spherical Inclusion in an Elastic Matrix: Exact Solution, and Implications for Mechanobiology.

J Appl Mech 2019 May 5;86(5):0510021-5100210. Epub 2019 Mar 5.

State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi'an Jiaotong University, Xi'an 710049, China.

The displacement of relatively rigid beads within a relatively compliant, elastic matrix can be used to measure the mechanical properties of the matrix. For example, in mechanobiological studies, magnetic or reflective beads can be displaced with a known external force to estimate the matrix modulus. Although such beads are generally rigid compared to the matrix, the material surrounding the beads typically differs from the matrix in one or two ways. The first case, as is common in mechanobiological experimentation, is the situation in which the bead must be coated with materials such as protein ligands that enable adhesion to the matrix. These layers typically differ in stiffness relative to the matrix material. The second case, common for uncoated beads, is the situation in which the beads disrupt the structure of the hydrogel or polymer, leading to a region of enhanced or reduced stiffness in the neighborhood of the bead. To address both cases, we developed the first analytical solution of the problem of translation of a coated, rigid spherical inclusion displaced within an isotropic elastic matrix by a remotely applied force. The solution is applicable to cases of arbitrary coating stiffness and size of the coating. We conclude by discussing applications of the solution to mechanobiology.
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http://dx.doi.org/10.1115/1.4042575DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6871264PMC
May 2019

Regulation of Cell Behavior by Hydrostatic Pressure.

Appl Mech Rev 2019 Jul 23;71(4):0408031-4080313. Epub 2019 Jul 23.

The Key Laboratory of Biomedical InformationEngineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, China.

Hydrostatic pressure (HP) regulates diverse cell behaviors including differentiation, migration, apoptosis, and proliferation. Abnormal HP is associated with pathologies including glaucoma and hypertensive fibrotic remodeling. In this review, recent advances in quantifying and predicting how cells respond to HP across several tissue systems are presented, including tissues of the brain, eye, vasculature and bladder, as well as articular cartilage. Finally, some promising directions on the study of cell behaviors regulated by HP are proposed.
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http://dx.doi.org/10.1115/1.4043947DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6808007PMC
July 2019

Energy Storage and Dissipation of Human Periodontal Ligament during Mastication Movement.

ACS Biomater Sci Eng 2018 Dec 17;4(12):4028-4035. Epub 2018 Oct 17.

As a layer of soft fibrous tissue, the periodontal ligament (PDL) protects against mechanical shock when transmitting mastication force from tooth to its surrounding alveolar bone. Currently, no quantitative method is available to estimate the shock resistance ability of the PDL. To solve this problem, in the present study we developed a finite element (FE) model of the tooth-PDL-bone complex and analyzed the energy storage and dissipation during the mastication movements. Displacement and Mises stress of tooth-PDL-bone complex show that the PDL is able to protect the alveolar bone from mechanical shock by shielding the transfer of deformation and stress. During mastication, the energy of the PDL is stored up to ∼161.5 J/mm at the period of loading and dissipated about one-tenth of the stored energy when unloading. The energy storage is displacement-dependent but time-independent because of the hyperelasticity of PDL. However, the energy dissipation is time- and displacement-dependent because of the viscoelasticity of PDL. The present study helps to understand the periodontal potential and the origin of dental diseases such as tooth concussion and occlusal trauma from the view of energy conversion.
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http://dx.doi.org/10.1021/acsbiomaterials.8b00667DOI Listing
December 2018

The protective effects of acupoint gel embedding on rats with myocardial ischemia-reperfusion injury.

Life Sci 2018 Oct 5;211:51-62. Epub 2018 Sep 5.

MOE Key Laboratory of Biomedical Information Engineering, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China. Electronic address:

Aims: Prevention and treatment of myocardial ischemia-reperfusion (I/R) injury has for many years been a hot topic in treating ischemic heart disease. As one of the most well-known methods of complementary and alternative medicine, acupuncture has attracted increasing interest in preventing myocardial I/R injury due to its remarkable effectiveness and minimal side effect. However, traditional acupuncture approaches are limited by cumbersome execution, high labor costs and inevitable pain caused by frequent stimulation. Therefore, in this work, we aimed to develop a novel acupoint gel embedding approach and investigated its role in protecting against myocardial I/R injury in rats.

Main Methods: Gels were embedded at bilateral Neiguan (PC6) points of rats and their protective effects against myocardial I/R injury evaluated in terms of changes in histomorphology, myocardial enzymology, antioxidant capacity, anti-inflammatory response, and anti-apoptosis of cells.

Key Findings: We found that the approach of acupoint gel embedding could significantly reduce myocardial infarcted size, repair pathological changes, mitigate oxidative stress damage and inflammatory response, as well as inhibit apoptosis of cardiomyocytes. Such cardioprotective effects were found to be associated with Notch-1/Jagged-1 signaling pathway.

Significance: The proposed approach of acupoint gel embedding has advantages in continuous acupoint stimulation, dosing controls, and no side effects in the course of treatment, as well as in reducing the pain caused by frequent acupuncture. It can form an alternative therapy to not only protect against myocardial I/R injury but also hold great potential in treating other diseases in the future.
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http://dx.doi.org/10.1016/j.lfs.2018.09.010DOI Listing
October 2018

Arabidopsis Leaf Trichomes as Acoustic Antennae.

Biophys J 2017 Nov;113(9):2068-2076

Biomedical Engineering and Biomechanics Center (BEBC), School of Life Sciences, Xi'an Jiaotong University, Xi'an, China; Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, Missouri; Gladys Levis Allen Laboratory of Plant Sensory Physiology, Biology Department, Washington University in St. Louis, St. Louis, Missouri; NSF Center for Engineering MechanoBiology, Washington University in St. Louis, St. Louis, Missouri. Electronic address:

The much studied plant Arabidopsis thaliana has been reported recently to react to the sounds of caterpillars of Pieris rapae chewing on its leaves by promoting synthesis of toxins that can deter herbivory. Identifying participating receptor cells-potential "ears"-of Arabidopsis is critical to understanding and harnessing this response. Motivated in part by other recent observations that Arabidopsis trichomes (hair cells) respond to mechanical stimuli such as pressing or brushing by initiating potential signaling factors in themselves and in the neighboring skirt of cells, we analyzed the vibrational responses of Arabidopsis trichomes to test the hypothesis that trichomes can respond acoustically to vibrations associated with feeding caterpillars. We found that these trichomes have vibrational modes in the frequency range of the sounds of feeding caterpillars, encouraging further experimentation to determine whether trichomes serve as mechanical antennae.
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http://dx.doi.org/10.1016/j.bpj.2017.07.035DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5685652PMC
November 2017

Trichomes as a natural biophysical barrier for plants and their bioinspired applications.

Soft Matter 2017 Aug;13(30):5096-5106

The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, P. R. China.

Nature has inspired mankind to create novel inventions with biomimetic structures and materials, where plants provide a significant source of inspiration. Plants have evolved a range of effective appendages, among which trichomes have attracted extensive research interest due to their enormous functions. It is important to understand trichome functions and corresponding mechanisms for their bioinspired applications. In this review, we provide a comprehensive overview of the diverse functions of trichomes, with emphasis placed upon their roles as biophysical barriers that can create a complex three-dimensional (3D) network to help the plant adapt to severe environments. Moreover, we also summarize the bioinspired applications of four typical trichomes, including needle-like, hook-like, foliar-like, and antenna-like trichomes. This review offers a new perspective of interdisciplinary research on both trichome functions and their biomimetic applications.
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http://dx.doi.org/10.1039/c7sm00622eDOI Listing
August 2017

Fountain streaming contributes to fast tip-growth through regulating the gradients of turgor pressure and concentration in pollen tubes.

Soft Matter 2017 Apr;13(16):2919-2927

State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'an Jiaotong University, Xi'an 710049, P. R. China. and Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, P. R. China.

Fountain streaming is a typical microfluidic pattern in plant cells, especially for cells with a high aspect ratio such as pollen tubes. Although it has been found that fountain streaming plays crucial roles in the transport of nutrients and metabolites, the positioning of organelles and the mixing of cytoplasms, its implications for the fast tip growth of pollen tubes remain a mystery. To address this, based on the observations of asiatic lily Lilium Casablanca, we developed physical models for reverse fountain streaming in pollen tubes and solved the hydrodynamics and advection-diffusion dynamics of viscous Stokes flow in the shank and apical region of pollen tubes. Theoretical and numerical results demonstrated that the gradients of turgor pressure and concentration of wall materials along the length of pollen tubes provide undamped driving force and high-efficiency materials supply, which are supposed to contribute to the fast tip-growth of pollen tubes. The sample experimental results show that the tip-growth will be abnormal when the gradients of turgor pressure change under osmotic stress induced by different concentrations of PEG-6000 (a dehydrant).
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http://dx.doi.org/10.1039/c6sm01915cDOI Listing
April 2017

Gradient Mechanical Properties Facilitate Arabidopsis Trichome as Mechanosensor.

ACS Appl Mater Interfaces 2016 Apr 5;8(15):9755-61. Epub 2016 Apr 5.

The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University , Xi'an 710049, P. R. China.

It has been reported that Arabidopsis thaliana leaf trichome can act as a mechanosensory switch, transducing mechanical stimuli into physiological signals, mainly through a buckling instability to focus external force (e.g., exerted by insects) on the base of trichome. The material and structural properties of trichomes remain largely unknown in this buckling instability. In this report, we mainly focused on material standpoint to explore the possible mechanism facilitating the buckling instability. We observed that the Young's modulus of trichome cell wall decreased gradually from branch to the base region of trichome. Interestingly, we also found a corresponding decline of calcium concentration on the trichome cell wall. Results of finite element method (FEM) simulation suggested that such a gradient distribution of Young's modulus significantly promotes force focusing and buckling instability on the base of trichome. It is indicated that Arabidopsis trichome has developed into an active mechanosensor benefiting from gradient cell wall mechanical properties.
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http://dx.doi.org/10.1021/acsami.6b02253DOI Listing
April 2016

Patterning Cellular Alignment through Stretching Hydrogels with Programmable Strain Gradients.

ACS Appl Mater Interfaces 2015 Jul 1;7(27):15088-97. Epub 2015 Jul 1.

§Qian Xuesen Laboratory of Space Technology, China Academy of Space Technology, Beijing 100094, People's Republic of China.

The graded mechanical properties (e.g., stiffness and stress/strain) of excellular matrix play an important role in guiding cellular alignment, as vital in tissue reconstruction with proper functions. Though various methods have been developed to engineer a graded mechanical environment to study its effect on cellular behaviors, most of them failed to distinguish stiffness effect from stress/strain effect during mechanical loading. Here, we construct a mechanical environment with programmable strain gradients by using a hydrogel of a linear elastic property. When seeding cells on such hydrogels, we demonstrate that the pattern of cellular alignment can be rather precisely tailored by substrate strains. The experiment is in consistency with a theoritical prediction when assuming that focal adhesions (FAs) would drive a cell to reorient to the directions where they are most stable. A fundamental theory has also been developed and is excellent in agreement with the complete temporal alignment of cells. This work not only provides important insights into the cellular response to the local mechanical microenvironment but can also be utilized to engineer patterned cellular alignment that can be critical in tissue remodeling and regenerative medicine applications.
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http://dx.doi.org/10.1021/acsami.5b04450DOI Listing
July 2015

Reaction-induced swelling of ionic gels.

Soft Matter 2015 Jan;11(3):449-55

State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'an Jiaotong University, Xi'an 710049, P.R. China.

A chemomechanical theory is proposed to describe the dynamic behavior and response time of ionic gels. The large deformation of these gels accompanied by the migration of mobile ions is driven by a common non-equilibrium chemical reaction. The theoretical model was validated using existing experimental data. Further investigations showed that the dynamic deformation and response time of an ionic gel are dependent on the concentration of reactive and non-reactive ions, the time of exposure to external stimuli, the initial state and the density of ionizable groups on the polymer chains.
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http://dx.doi.org/10.1039/c4sm02252aDOI Listing
January 2015

Noise-induced spatiotemporal patterns in Hodgkin-Huxley neuronal network.

Cogn Neurodyn 2013 Oct 5;7(5):431-40. Epub 2013 Feb 5.

Key Laboratory of Biomedical Information Engineering of Education Ministry, Xi'an Jiaotong University, Xi'an, China.

The effect of noise on the pattern selection in a regular network of Hodgkin-Huxley neurons is investigated, and the transition of pattern in the network is measured from subexcitable to excitable media. Extensive numerical results confirm that kinds of travelling wave such as spiral wave, circle wave and target wave could be developed and kept alive in the subexcitable network due to the noise. In the case of excitable media under noise, the developed spiral wave and target wave could coexist and new target-like wave is induced near to the border of media. The averaged membrane potentials over all neurons in the network are calculated to detect the periodicity of the time series and the generated traveling wave. Furthermore, the firing probabilities of neurons in networks are also calculated to analyze the collective behavior of networks.
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http://dx.doi.org/10.1007/s11571-013-9245-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3773323PMC
October 2013

Kinetic modelling and bifurcation analysis of chemomechanically miniaturized gels under mechanical load.

Eur Phys J E Soft Matter 2013 Sep 26;36(9):108. Epub 2013 Sep 26.

State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'an Jiaotong University, 710049, Xi'an, China,

Chemomechanically responsive gels, with great potential applications in the fields of smart structures and biomedicines, present autonomously oscillatory deformation driven by the Belousov-Zhabotinsky chemical reaction. The dynamic behavior of the responsive gels is obviously affected by the external mechanical load. This approach proposed a kinetic model with an ordinary differential equation to describe the oscillatory deformation of the gels under the mechanical load. Then the periodic solutions and phase diagrams of the oscillation are obtained using the improved Runge-Kutta and shooting methods. The results demonstrated that bifurcations are typically existent in the system and the characters of the oscillatory deformation regularly depend on the mechanical load as well as the concentration of reactants and the stoichiometric coefficient of chemical reaction. This development is supposed to promote the practical applications of the chemomechanically responsive gels.
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http://dx.doi.org/10.1140/epje/i2013-13108-xDOI Listing
September 2013

Directed self-assembly of microscale hydrogels by electrostatic interaction.

Biofabrication 2013 Sep 29;5(3):035004. Epub 2013 May 29.

The Key Laboratory of Biomedical Information Engineering of Ministry of Education, Xi'an Jiaotong University School of Life Science and Technology, Xi'an 710049, People's Republic of China.

The unique benefit of electrostatic self-assembly of microscale components in solution is demonstrated for the first time. In particular, positive and negative treatment of poly(ethylene glycol) (PEG) facilitates a novel bottom-up assembly approach using electrostatic interaction from microgels with opposite charges. Fundamental investigations of electrostatic interaction of microgels reveal that the contact area of microgels determines the total energy of construct and thus the final patterns. The electrostatic self-assembly approach enables the fabrication of large and complex biological related structures (e.g., multi-layer spheroid) with accurate control. By the design of the microgels, the thickness and number of microgels in each layer can be controlled. Biological investigations of positive and negative treatments of PEG further prove the possibility of using this approach in tissue engineering, regenerative medicine and drug delivery.
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http://dx.doi.org/10.1088/1758-5082/5/3/035004DOI Listing
September 2013

Analysis of thermal-induced dentinal fluid flow and its implications in dental thermal pain.

Arch Oral Biol 2011 Sep 15;56(9):846-54. Epub 2011 Mar 15.

Biomedical Engineering and Biomechanics Center, School of Aerospace, Xi'an Jiaotong University, Xi'an 710049, PR China.

Objectives: The initiation of the pain sensation experienced following the thermal stimulation of dentine has been correlated with fluid flow in the dentinal tubules. There may be other mechanisms.

Methods: This study examines this possibility using a mathematical model to simulate the temperature and thermal stress distribution in a tooth undergoing thermal stimulation. The results obtained were then used to predict the fluid flow in a single dentinal tubule by considering the deformation of the dentinal tubules and dentinal fluid.

Results: Deformation of the pulp chamber was observed before a noticeable temperature change was recorded at the dentine-enamel junction. Tubule deformation leads to changes in fluid flow more rapidly than fluid expansion or contraction. This finding agreed with previously reported experimental observations. An initially high rate of outward fluid flow under cooling was found to correspond to short latency neural responses whilst heating was associated with long latency neural responses.

Conclusion: Rapid fluid flow caused by thermal deformation of dentinal tubules may account for the short latency (<1s) activation of mechano-sensitive receptors after of cooling. Long latency (>10s) neural responses could be associated with the activation of thermo-sensitive receptors.
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http://dx.doi.org/10.1016/j.archoralbio.2011.02.011DOI Listing
September 2011
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