Giuseppe Maria Ferro, Andrea Somazzi, Didier Sornette
To ensure optimal survival of the neonate, the biological timing of parturition must be tightly controlled. Medical studies show that a variety of endocrine systems play the role of a control system, establishing a dynamic balance between the forces that cause uterine quiescence during pregnancy and the forces that produce coordinated uterine contractility at parturition. These control mechanism, and the factors that affect their performance, are still poorly understood. To help fill this gap, we propose a model of the pregnant uterus as a network of FitzHugh-Nagumo oscillators, with each cell symbolizing the electrical activity of a myocyte. The model is augmented with sparse adaptive control mechanisms representing the regulating endocrine functions. The control system is characterized by the fraction of controlled sites, and strength of control. We quantitatively find the conditions for which the control system exhibit a balance between robustness (resilience against perturbations) and flexibility (ability to switch function with minimal cost) crucial for optimal neonatal survival. Specifically, we show that Braxton-Hicks and Alvarez contractions, which are observed sporadic contractions of the uterine muscle, serve as a safety valve against over-controlling, strategically suppressed yet retained to optimize the control system's efficiency. Preterm birth is suggested to be understood as a mis-identification of the control boundaries. These insights contribute to advancing our understanding of maternal-fetal health.
{"title":"In-silico model of the pregnant uterus as a network of oscillators under sparse adaptive control","authors":"Giuseppe Maria Ferro, Andrea Somazzi, Didier Sornette","doi":"arxiv-2408.00956","DOIUrl":"https://doi.org/arxiv-2408.00956","url":null,"abstract":"To ensure optimal survival of the neonate, the biological timing of\u0000parturition must be tightly controlled. Medical studies show that a variety of\u0000endocrine systems play the role of a control system, establishing a dynamic\u0000balance between the forces that cause uterine quiescence during pregnancy and\u0000the forces that produce coordinated uterine contractility at parturition. These\u0000control mechanism, and the factors that affect their performance, are still\u0000poorly understood. To help fill this gap, we propose a model of the pregnant\u0000uterus as a network of FitzHugh-Nagumo oscillators, with each cell symbolizing\u0000the electrical activity of a myocyte. The model is augmented with sparse\u0000adaptive control mechanisms representing the regulating endocrine functions.\u0000The control system is characterized by the fraction of controlled sites, and\u0000strength of control. We quantitatively find the conditions for which the\u0000control system exhibit a balance between robustness (resilience against\u0000perturbations) and flexibility (ability to switch function with minimal cost)\u0000crucial for optimal neonatal survival. Specifically, we show that Braxton-Hicks\u0000and Alvarez contractions, which are observed sporadic contractions of the\u0000uterine muscle, serve as a safety valve against over-controlling, strategically\u0000suppressed yet retained to optimize the control system's efficiency. Preterm\u0000birth is suggested to be understood as a mis-identification of the control\u0000boundaries. These insights contribute to advancing our understanding of\u0000maternal-fetal health.","PeriodicalId":501040,"journal":{"name":"arXiv - PHYS - Biological Physics","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141939928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Biomolecular condensates are membraneless compartments in the cell that are involved in a wide diversity of biological processes. These phase-separated droplets usually exhibit a viscoelastic mechanical response. A behavior rationalized by modeling the complex molecules that make up a condensate as stickers and spacers, which assemble into a network-like structure. The proper functioning of biocondensates requires precise control over their composition, size, and mechanical response. For example, several neurodegenerative diseases are associated with dysfunctional condensates that solidify over a long period of time (days) until they become solid. A phenomenon usually described as aging. The emergence of such a long timescale of evolution from microscopic events, as well as the associated microscopic reorganization leading to aging, remains mostly an open question. In this article, we explore the connection between the mechanical properties of the condensates and their microscopic structure. We propose a minimal model for the dynamic of stickers and spacers, and show that entropy minimization of spacers leads to an attractive force between stickers. Our system displays a surprisingly slow relaxation toward equilibrium, reminiscent of glassy systems and consistent with the liquid-to-solid transition observed. To explain this behavior, we study the clustering dynamic of stickers and successfully explain the origin of glassy relaxation.
{"title":"Microscopic model for aging of biocondensates","authors":"Hugo Le Roy, Paolo De Los Rios","doi":"arxiv-2407.21710","DOIUrl":"https://doi.org/arxiv-2407.21710","url":null,"abstract":"Biomolecular condensates are membraneless compartments in the cell that are\u0000involved in a wide diversity of biological processes. These phase-separated\u0000droplets usually exhibit a viscoelastic mechanical response. A behavior\u0000rationalized by modeling the complex molecules that make up a condensate as\u0000stickers and spacers, which assemble into a network-like structure. The proper\u0000functioning of biocondensates requires precise control over their composition,\u0000size, and mechanical response. For example, several neurodegenerative diseases\u0000are associated with dysfunctional condensates that solidify over a long period\u0000of time (days) until they become solid. A phenomenon usually described as\u0000aging. The emergence of such a long timescale of evolution from microscopic\u0000events, as well as the associated microscopic reorganization leading to aging,\u0000remains mostly an open question. In this article, we explore the connection\u0000between the mechanical properties of the condensates and their microscopic\u0000structure. We propose a minimal model for the dynamic of stickers and spacers,\u0000and show that entropy minimization of spacers leads to an attractive force\u0000between stickers. Our system displays a surprisingly slow relaxation toward\u0000equilibrium, reminiscent of glassy systems and consistent with the\u0000liquid-to-solid transition observed. To explain this behavior, we study the\u0000clustering dynamic of stickers and successfully explain the origin of glassy\u0000relaxation.","PeriodicalId":501040,"journal":{"name":"arXiv - PHYS - Biological Physics","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867117","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A Lokaveer, Thomas Anjana, Maliyekkal Yasir, S Yogahariharan, Akash Dewangan, Saurabh Kishor Mahajan, Sakshi Aravind Tembhurne, Gunja Subhash Gupta, Devashish Bhalla, Anantha Datta Dhruva, Aloke Kumar, Koushik Viswanathan, Vikram Khaire, Anand Narayanan, Priyadarshnam Hari
The SSPACE Astrobiology Payload (SAP) series, starting with the SAP-1 project is designed to conduct in-situ microbiology experiments in low earth orbit. This payload series aims to understand the behaviour of microbial organisms in space, particularly those critical for human health, and the corresponding effects due to microgravity and solar/galactic radiation. SAP-1 focuses on studying Bacillus clausii and Bacillus coagulans, bacteria beneficial to humans. It aims to provide a space laboratory for astrobiology experiments under microgravity conditions. The hardware developed for these experiments is indigenous and tailored to meet the unique requirements of autonomous microbiology experiments by controlling pressure, temperature, and nutrition flow to bacteria. A rotating platform, which forms the core design, is innovatively utilised to regulate the flow and mixing of nutrients with dormant bacteria. The technology demonstration models developed at SSPACE have yielded promising results, with ongoing efforts to refine, adapt for space conditions, and prepare for integration with nanosatellites or space modules. The anticipated payload will be compact, approximately 1U in size (10cm x 10cm x 10cm), consume less than 5W power, and offer flexibility for various microbiological studies.
SSPACE 天体生物学有效载荷（SAP）系列，从 SAP-1 项目开始，旨在低地球轨道上进行原位微生物学实验。该有效载荷系列旨在了解空间微生物有机体的行为，特别是那些对人类健康至关重要的微生物有机体的行为，以及微重力和太阳/银河辐射造成的相应影响。SAP-1的重点是研究对人类有益的细菌Bacillus clausii和Bacillus coagulans。其目的是为微重力条件下的天体生物学实验提供一个空间实验室。为这些实验开发的硬件是本土的，通过控制压力、温度和细菌的营养流来满足自主微生物学实验的独特要求。构成核心设计的旋转平台被创新性地用于调节营养物质与休眠细菌的流动和混合。在 SSPACE 开发的技术示范模型已经取得了可喜的成果，目前正在努力进行改进，以适应太空条件，并为与纳米卫星或太空舱集成做好准备。预期的有效载荷将非常紧凑，大小约为 1U （10 厘米 x 10 厘米 x 10 厘米），功耗小于 5 瓦，并为各种微生物研究提供灵活性。
{"title":"SSPACE Astrobiology Payload-1 (SAP-1)","authors":"A Lokaveer, Thomas Anjana, Maliyekkal Yasir, S Yogahariharan, Akash Dewangan, Saurabh Kishor Mahajan, Sakshi Aravind Tembhurne, Gunja Subhash Gupta, Devashish Bhalla, Anantha Datta Dhruva, Aloke Kumar, Koushik Viswanathan, Vikram Khaire, Anand Narayanan, Priyadarshnam Hari","doi":"arxiv-2407.21183","DOIUrl":"https://doi.org/arxiv-2407.21183","url":null,"abstract":"The SSPACE Astrobiology Payload (SAP) series, starting with the SAP-1 project\u0000is designed to conduct in-situ microbiology experiments in low earth orbit.\u0000This payload series aims to understand the behaviour of microbial organisms in\u0000space, particularly those critical for human health, and the corresponding\u0000effects due to microgravity and solar/galactic radiation. SAP-1 focuses on\u0000studying Bacillus clausii and Bacillus coagulans, bacteria beneficial to\u0000humans. It aims to provide a space laboratory for astrobiology experiments\u0000under microgravity conditions. The hardware developed for these experiments is\u0000indigenous and tailored to meet the unique requirements of autonomous\u0000microbiology experiments by controlling pressure, temperature, and nutrition\u0000flow to bacteria. A rotating platform, which forms the core design, is\u0000innovatively utilised to regulate the flow and mixing of nutrients with dormant\u0000bacteria. The technology demonstration models developed at SSPACE have yielded\u0000promising results, with ongoing efforts to refine, adapt for space conditions,\u0000and prepare for integration with nanosatellites or space modules. The\u0000anticipated payload will be compact, approximately 1U in size (10cm x 10cm x\u000010cm), consume less than 5W power, and offer flexibility for various\u0000microbiological studies.","PeriodicalId":501040,"journal":{"name":"arXiv - PHYS - Biological Physics","volume":"46 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yuri Z. Sinzato, Robert Uittenbogaard, Petra M. Visser, Jef Huisman, Maziyar Jalaal
Fluid flow has a major effect on the aggregation and fragmentation of bacterial colonies. Yet, a generic framework to understand and predict how hydrodynamics affects colony size remains elusive. This study investigates how fluid flow affects the formation and maintenance of large colonial structures in cyanobacteria. We performed experiments on laboratory cultures and lake samples of the cyanobacterium Microcystis, while their colony size distribution was measured simultaneously by direct microscopic imaging. We demonstrate that EPS-embedded cells formed by cell division exhibit significant mechanical resistance to shear forces. However, at elevated hydrodynamic stress levels (exceeding those typically generated by surface wind mixing) these colonies experience fragmentation through an erosion process. We also show that single cells can aggregate into small colonies due to fluid flow. However, the structural integrity of these flow-induced colonies is weaker than that of colonies formed by cell division. We provide a mathematical analysis to support the experiments and demonstrate that a population model with two categories of colonies describes the measured size distributions. Our results shed light on the specific conditions wherein flow-induced fragmentation and aggregation of cyanobacteria are decisive and indicate that colony formation under natural conditions is mainly driven by cell division, although flow-induced aggregation could play a role in dense bloom events. These findings can be used to improve prediction models and mitigation strategies for toxic cyanobacterial blooms and also offer potential applications in other areas such as algal biotechnology or medical settings where the dynamics of biological aggregates play a significant role.
{"title":"Fragmentation and aggregation of cyanobacterial colonies","authors":"Yuri Z. Sinzato, Robert Uittenbogaard, Petra M. Visser, Jef Huisman, Maziyar Jalaal","doi":"arxiv-2407.21115","DOIUrl":"https://doi.org/arxiv-2407.21115","url":null,"abstract":"Fluid flow has a major effect on the aggregation and fragmentation of\u0000bacterial colonies. Yet, a generic framework to understand and predict how\u0000hydrodynamics affects colony size remains elusive. This study investigates how\u0000fluid flow affects the formation and maintenance of large colonial structures\u0000in cyanobacteria. We performed experiments on laboratory cultures and lake\u0000samples of the cyanobacterium Microcystis, while their colony size distribution\u0000was measured simultaneously by direct microscopic imaging. We demonstrate that\u0000EPS-embedded cells formed by cell division exhibit significant mechanical\u0000resistance to shear forces. However, at elevated hydrodynamic stress levels\u0000(exceeding those typically generated by surface wind mixing) these colonies\u0000experience fragmentation through an erosion process. We also show that single\u0000cells can aggregate into small colonies due to fluid flow. However, the\u0000structural integrity of these flow-induced colonies is weaker than that of\u0000colonies formed by cell division. We provide a mathematical analysis to support\u0000the experiments and demonstrate that a population model with two categories of\u0000colonies describes the measured size distributions. Our results shed light on\u0000the specific conditions wherein flow-induced fragmentation and aggregation of\u0000cyanobacteria are decisive and indicate that colony formation under natural\u0000conditions is mainly driven by cell division, although flow-induced aggregation\u0000could play a role in dense bloom events. These findings can be used to improve\u0000prediction models and mitigation strategies for toxic cyanobacterial blooms and\u0000also offer potential applications in other areas such as algal biotechnology or\u0000medical settings where the dynamics of biological aggregates play a significant\u0000role.","PeriodicalId":501040,"journal":{"name":"arXiv - PHYS - Biological Physics","volume":"148 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
David March-Pons, Romualdo Pastor-Satorras, M. Carmen Miguel
The precise modulation of activity through inhibitory signals ensures that both insect colonies and neural circuits operate efficiently and adaptively, highlighting the fundamental importance of inhibition in biological systems. Modulatory signals are produced in various contexts and are known for subtly shifting the probability of receiver behaviors based on response thresholds. Here we propose a non-linear function to introduce inhibitory responsiveness in collective decision-making inspired by honeybee house-hunting. We show that, compared with usual linear functions, non-linear responses enhance final consensus and reduce deliberation time. This improvement comes at the cost of reduced accuracy in identifying the best option. Nonetheless, for value-based tasks, the benefits of faster consensus and enhanced decision-making might outweigh this drawback.
{"title":"Non-linear inhibitory responses enhance performance in collective decision-making","authors":"David March-Pons, Romualdo Pastor-Satorras, M. Carmen Miguel","doi":"arxiv-2407.20927","DOIUrl":"https://doi.org/arxiv-2407.20927","url":null,"abstract":"The precise modulation of activity through inhibitory signals ensures that\u0000both insect colonies and neural circuits operate efficiently and adaptively,\u0000highlighting the fundamental importance of inhibition in biological systems.\u0000Modulatory signals are produced in various contexts and are known for subtly\u0000shifting the probability of receiver behaviors based on response thresholds.\u0000Here we propose a non-linear function to introduce inhibitory responsiveness in\u0000collective decision-making inspired by honeybee house-hunting. We show that,\u0000compared with usual linear functions, non-linear responses enhance final\u0000consensus and reduce deliberation time. This improvement comes at the cost of\u0000reduced accuracy in identifying the best option. Nonetheless, for value-based\u0000tasks, the benefits of faster consensus and enhanced decision-making might\u0000outweigh this drawback.","PeriodicalId":501040,"journal":{"name":"arXiv - PHYS - Biological Physics","volume":"150 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tian-liang Xu, Chao-ran Qin, Bin Tang, Jin-cheng Gao, Jiankang Zhou, Kang Chen, Tian Hui Zhang, Wen-de Tian
It has been supposed that the interplay of elasticity and activity plays a key role in triggering the non-equilibrium behaviors in biological systems. However, the experimental model system is missing to investigate the spatiotemporally dynamical phenomena. Here, a model system of an active chain, where active eccentric-disks are linked by a spring, is designed to study the interplay of activity, elasticity, and friction. Individual active chain exhibits longitudinal and transverse motion, however, it starts to self-rotate when pinning one end, and self-beats when clamping one end. Additionally, our eccentric-disk model can qualitatively reproduce such behaviors and explain the unusual self-rotation of the first disk around its geometric center. Further, the structure and dynamics of long chains were studied via simulations without steric interactions. It was found that hairpin conformation emerges in free motion, while in the constrained motions, the rotational and beating frequencies scale with the flexure number (the ratio of self-propelling force to bending rigidity), ~4/3. Scaling analysis suggests that it results from the balance between activity and energy dissipation. Our findings show that topological constraints play a vital role in non-equilibrium synergy behavior.
{"title":"Constrained motion of self-propelling eccentric disks linked by a spring","authors":"Tian-liang Xu, Chao-ran Qin, Bin Tang, Jin-cheng Gao, Jiankang Zhou, Kang Chen, Tian Hui Zhang, Wen-de Tian","doi":"arxiv-2407.20610","DOIUrl":"https://doi.org/arxiv-2407.20610","url":null,"abstract":"It has been supposed that the interplay of elasticity and activity plays a\u0000key role in triggering the non-equilibrium behaviors in biological systems.\u0000However, the experimental model system is missing to investigate the\u0000spatiotemporally dynamical phenomena. Here, a model system of an active chain,\u0000where active eccentric-disks are linked by a spring, is designed to study the\u0000interplay of activity, elasticity, and friction. Individual active chain\u0000exhibits longitudinal and transverse motion, however, it starts to self-rotate\u0000when pinning one end, and self-beats when clamping one end. Additionally, our\u0000eccentric-disk model can qualitatively reproduce such behaviors and explain the\u0000unusual self-rotation of the first disk around its geometric center. Further,\u0000the structure and dynamics of long chains were studied via simulations without\u0000steric interactions. It was found that hairpin conformation emerges in free\u0000motion, while in the constrained motions, the rotational and beating\u0000frequencies scale with the flexure number (the ratio of self-propelling force\u0000to bending rigidity), ~4/3. Scaling analysis suggests that it results from the\u0000balance between activity and energy dissipation. Our findings show that\u0000topological constraints play a vital role in non-equilibrium synergy behavior.","PeriodicalId":501040,"journal":{"name":"arXiv - PHYS - Biological Physics","volume":"50 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hasan Berkay Abdioglu, Yagmur Isik, Merve Sevgi, Ufuk Gorkem Kirabali, Yunus Emre Mert, Gulnihal Guldogan, Selin Serdarli, Tarik Taha Gulen, Huseyin Uvet
Accurately measuring cell stiffness is challenging due to the invasiveness of traditional methods like atomic force microscopy (AFM) and optical stretching. We introduce a non-invasive off-axis system using holographic imaging and acoustic stimulation. This system features an off-axis Mach-Zehnder interferometer and bulk acoustic waves to capture cell mechanics. It employs high-resolution components to create detailed interferograms and allows continuous imaging of cell deformation. Unlike conventional techniques, our method provides high-throughput, label-free measurements while preserving cell integrity. Polyacrylamide beads are tested for high precision, highlighting the potential of the system in early cancer detection, disease monitoring, and mechanobiological research.
{"title":"Design of a System for Analyzing Cell Mechanics","authors":"Hasan Berkay Abdioglu, Yagmur Isik, Merve Sevgi, Ufuk Gorkem Kirabali, Yunus Emre Mert, Gulnihal Guldogan, Selin Serdarli, Tarik Taha Gulen, Huseyin Uvet","doi":"arxiv-2407.21182","DOIUrl":"https://doi.org/arxiv-2407.21182","url":null,"abstract":"Accurately measuring cell stiffness is challenging due to the invasiveness of\u0000traditional methods like atomic force microscopy (AFM) and optical stretching.\u0000We introduce a non-invasive off-axis system using holographic imaging and\u0000acoustic stimulation. This system features an off-axis Mach-Zehnder\u0000interferometer and bulk acoustic waves to capture cell mechanics. It employs\u0000high-resolution components to create detailed interferograms and allows\u0000continuous imaging of cell deformation. Unlike conventional techniques, our\u0000method provides high-throughput, label-free measurements while preserving cell\u0000integrity. Polyacrylamide beads are tested for high precision, highlighting the\u0000potential of the system in early cancer detection, disease monitoring, and\u0000mechanobiological research.","PeriodicalId":501040,"journal":{"name":"arXiv - PHYS - Biological Physics","volume":"104 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hassan N. Al Hashem, Amanda N. Abraham, Deepak Sharma, Andre Chambers, Mehrnoosh Moghaddar, Chayla L. Reeves, Sanjay K. Srivastava, Amy Gelmi, Arman Ahnood
The ability to form diamond electrodes on insulating polycrystalline diamond substrates using single-step laser patterning, and the use of the electrodes as a substrate that supports the adhesion and proliferation of human mesenchymal stem cells (hMSCs) is demonstrated. Laser induced graphitisation results in a conductive amorphous carbon surface, rich in oxygen and nitrogen terminations. This results in an electrode with a high specific capacitance of 182 uF/cm2, a wide water window of 3.25 V, and a low electrochemical impedance of 129 Ohms/cm2 at 1 kHz. The electrodes surface exhibited a good level of biocompatibility with hMSCs, supporting cell adhesion and proliferation. The cells cultured on the electrode displayed significant elongation and alignment along the direction of the laser patterned microgrooves. Because of its favourable electrochemical performance and biocompatibility, the laser-patterned diamond electrodes create a potential for a versatile platform in stem cell therapeutics.
{"title":"Laser patterned diamond electrodes for adhesion and proliferation of human mesenchymal stem cells","authors":"Hassan N. Al Hashem, Amanda N. Abraham, Deepak Sharma, Andre Chambers, Mehrnoosh Moghaddar, Chayla L. Reeves, Sanjay K. Srivastava, Amy Gelmi, Arman Ahnood","doi":"arxiv-2407.19582","DOIUrl":"https://doi.org/arxiv-2407.19582","url":null,"abstract":"The ability to form diamond electrodes on insulating polycrystalline diamond\u0000substrates using single-step laser patterning, and the use of the electrodes as\u0000a substrate that supports the adhesion and proliferation of human mesenchymal\u0000stem cells (hMSCs) is demonstrated. Laser induced graphitisation results in a\u0000conductive amorphous carbon surface, rich in oxygen and nitrogen terminations.\u0000This results in an electrode with a high specific capacitance of 182 uF/cm2, a\u0000wide water window of 3.25 V, and a low electrochemical impedance of 129\u0000Ohms/cm2 at 1 kHz. The electrodes surface exhibited a good level of\u0000biocompatibility with hMSCs, supporting cell adhesion and proliferation. The\u0000cells cultured on the electrode displayed significant elongation and alignment\u0000along the direction of the laser patterned microgrooves. Because of its\u0000favourable electrochemical performance and biocompatibility, the\u0000laser-patterned diamond electrodes create a potential for a versatile platform\u0000in stem cell therapeutics.","PeriodicalId":501040,"journal":{"name":"arXiv - PHYS - Biological Physics","volume":"170 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We study a mixture of extensile and contractile cells using a vertex model extended to include active nematic stresses. The two cell populations phase separate over time. While phase separation strengthens monotonically with an increasing magnitude of contractile activity, the dependence on extensile activity is non-monotonic, so that sufficiently high values reduce the extent of sorting. We interpret this by showing that extensile activity renders the system motile, enabling cells to undergo neighbour exchanges. Contractile cells that come into contact as a result are then more likely to stay connected due to an effective attraction arising from contractile activity.
{"title":"Cell Sorting in an Active Nematic Vertex Model","authors":"Jan Rozman, Julia M. Yeomans","doi":"arxiv-2407.19591","DOIUrl":"https://doi.org/arxiv-2407.19591","url":null,"abstract":"We study a mixture of extensile and contractile cells using a vertex model\u0000extended to include active nematic stresses. The two cell populations phase\u0000separate over time. While phase separation strengthens monotonically with an\u0000increasing magnitude of contractile activity, the dependence on extensile\u0000activity is non-monotonic, so that sufficiently high values reduce the extent\u0000of sorting. We interpret this by showing that extensile activity renders the\u0000system motile, enabling cells to undergo neighbour exchanges. Contractile cells\u0000that come into contact as a result are then more likely to stay connected due\u0000to an effective attraction arising from contractile activity.","PeriodicalId":501040,"journal":{"name":"arXiv - PHYS - Biological Physics","volume":"150 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jordan L. Shivers, Jingchen Feng, Fred C. MacKintosh
The mechanical properties of biological materials are spatially heterogeneous. Typical tissues are made up of a spanning fibrous extracellular matrix in which various inclusions, such as living cells, are embedded. While the influence of inclusions on the stiffness of common elastic materials such as rubber has been studied for decades and can be understood in terms of the volume fraction and shape of inclusions, the same is not true for disordered filamentous and fibrous networks. Recent work has shown that, in isolation, such networks exhibit unusual viscoelastic behavior indicative of an underlying mechanical phase transition controlled by network connectivity and strain. How this behavior is modified when inclusions are present is unclear. Here, we present a theoretical and computational study of the influence of rigid inclusions on the mechanics of disordered elastic networks near the connectivity-controlled central force rigidity transition. Combining scaling theory and coarse-grained simulations, we predict and confirm an anomalously strong dependence of the composite stiffness on inclusion volume fraction, beyond that seen in ordinary composites. This stiffening exceeds the well-established volume fraction-dependent stiffening expected in conventional composites, e.g., as an elastic analogue of the classic volume fraction dependent increase in the viscosity of liquids first identified by Einstein. We show that this enhancement is a consequence of the interplay between inter-particle spacing and an emergent correlation length, leading to an effective finite-size scaling imposed by the presence of inclusions. We outline the expected scaling of the shear modulus and strain fluctuations with the inclusion volume fraction and network connectivity, confirm these predictions in simulations, and discuss potential experimental tests and implications for our predictions in real systems.
{"title":"Criticality enhances the reinforcement of disordered networks by rigid inclusions","authors":"Jordan L. Shivers, Jingchen Feng, Fred C. MacKintosh","doi":"arxiv-2407.19563","DOIUrl":"https://doi.org/arxiv-2407.19563","url":null,"abstract":"The mechanical properties of biological materials are spatially\u0000heterogeneous. Typical tissues are made up of a spanning fibrous extracellular\u0000matrix in which various inclusions, such as living cells, are embedded. While\u0000the influence of inclusions on the stiffness of common elastic materials such\u0000as rubber has been studied for decades and can be understood in terms of the\u0000volume fraction and shape of inclusions, the same is not true for disordered\u0000filamentous and fibrous networks. Recent work has shown that, in isolation,\u0000such networks exhibit unusual viscoelastic behavior indicative of an underlying\u0000mechanical phase transition controlled by network connectivity and strain. How\u0000this behavior is modified when inclusions are present is unclear. Here, we\u0000present a theoretical and computational study of the influence of rigid\u0000inclusions on the mechanics of disordered elastic networks near the\u0000connectivity-controlled central force rigidity transition. Combining scaling\u0000theory and coarse-grained simulations, we predict and confirm an anomalously\u0000strong dependence of the composite stiffness on inclusion volume fraction,\u0000beyond that seen in ordinary composites. This stiffening exceeds the\u0000well-established volume fraction-dependent stiffening expected in conventional\u0000composites, e.g., as an elastic analogue of the classic volume fraction\u0000dependent increase in the viscosity of liquids first identified by Einstein. We\u0000show that this enhancement is a consequence of the interplay between\u0000inter-particle spacing and an emergent correlation length, leading to an\u0000effective finite-size scaling imposed by the presence of inclusions. We outline\u0000the expected scaling of the shear modulus and strain fluctuations with the\u0000inclusion volume fraction and network connectivity, confirm these predictions\u0000in simulations, and discuss potential experimental tests and implications for\u0000our predictions in real systems.","PeriodicalId":501040,"journal":{"name":"arXiv - PHYS - Biological Physics","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867143","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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