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Empowering engineered muscle in biohybrid pump by extending connexin 43 duration with reduced graphene oxides. Biomaterials 2022; 287:121643. [PMID: 35772349 DOI: 10.1016/j.biomaterials.2022.121643] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 06/08/2022] [Accepted: 06/17/2022] [Indexed: 11/20/2022]
Abstract
Engineered skeletal muscle act as therapeutics invaluable to treat injured or diseased muscle and a "living" material essential to assemble biological machinery. For normal development, skeletal myoblasts should express connexin 43, one of the gap junction proteins that promote myoblast fusion and myogenesis, during the early differentiation stage. However, myoblasts cultured in vitro often down-regulate connexin 43 before differentiation, limiting myogenesis and muscle contraction. This study demonstrates that tethering myoblasts with reduced graphene oxide (rGO) slows connexin 43 regression during early differentiation and increases myogenic mRNA synthesis. The whole RNA sequencing also confirms that the rGO on cells increases regulator genes for myogenesis, including troponin, while decreasing negative regulator genes. The resulting myotubes generated a three-fold larger contraction force than the rGO-free myotubes. Accordingly, a valveless biohybrid pump assembled with the rGO-tethered muscle increased the fluid velocity and flow rate considerably. The results of this study would provide an important foundation for developing physiologically relevant muscle and powering up biomachines that will be used for various bioscience studies and unexplored applications.
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Impact of treated sewage on meiobenthic nematodes: a case study from the Tunisian Refining Industries Company. BRAZ J BIOL 2022; 82:e246116. [DOI: 10.1590/1519-6984.246116] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 01/05/2021] [Indexed: 01/04/2023] Open
Abstract
Abstract The main objective of the current study was to assess the impact of the water taken from the ‘Tunisian Refining Industries Company’ on meiobenthic nematodes, before and after a series of treatments in decantation basins followed by its discharge in Bizerte bay, Tunisia. The comparison of environmental parameters of the two types of water was clearly indicative of an improvement in the quality of treated waters after a significant reduction in their loads in hydrocarbons. Overall, the water retained a good quality after being treated by ‘Tunisian Refining Industries Company’ before discharge in the sea. At the end of the experiment, differential responses were observed according to the richness of sediment in organic matter and hydrocarbons. Thus, it was apparent that the nematode assemblage exposed to the treated waters was closer to controls and associated to higher values of abundance, than that under untreated ones. It was also assumed that the species Microlaimus honestus De Man, 1922, Paramonohystera proteus Wieser, 1956 and Cyartonema germanicum Juario, 1972 are sensitive bioindicators of bad environmental statues and of hydrocarbon presence in the environment. On the other hand, Metoncholaimus pristiurus (Zur Strassen, 1894) Filipjev, 1918 would rather be classified as a positive bioindicative species of this type of pollutants.
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Potential Hepatoprotective Effect of Cheatomorpha gracilis extract against High Fat Diet (HFD)-Induced Liver Damage, and its characterization by HPLC. BRAZ J BIOL 2021; 82:e247102. [PMID: 34161431 DOI: 10.1590/1519-6984.247102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Accepted: 02/17/2021] [Indexed: 11/22/2022] Open
Abstract
The current investigation was carried out to estimate the protective effect of aqueous extract of Cheatomorpha gracilis (AEC) against High fat Diet (HFD) induced liver damage in mice. The results of the in vitro study showed that AEC have higher antioxidant capacities in the DPPH and hydroxyl radical-scavenging assays. Indeed, many phenolic compounds (gallic acid, quercetin, naringenin, apigenin, kaempferol and rutin) were identified in the AEC. In the animal studies, during 6 weeks, HFD promoted oxidative stress with a rise level of malonaldehyde (MDA), protein carbonyls (PCOs) levels and a significant decrease of the antioxidant enzyme activities such as superoxide dismutase, catalase and glutathione peroxidase. Interestingly, the treatment with AEC (250 mg/kg body weight) significantly reduced the effects of HFD disorders on some plasmatic liver biomarkers (AST, ALT and ALP) in addition to, plasmatic proteins inflammatory biomarkers (α2 and β1 decreases / β2 and γ globulins increases). It can be suggest that supplementation of MECG displays high potential to quench free radicals and attenuates high fat diet promoted liver oxidative stress and related disturbances.
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Spatio-temporal distribution patterns of Chironomidae communities in the wadis of Northern Tunisia. BRAZ J BIOL 2021; 82:e247073. [PMID: 33978088 DOI: 10.1590/1519-6984.247073] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Accepted: 02/06/2021] [Indexed: 11/21/2022] Open
Abstract
In Northern Tunisia, seasonal streams, called wadi, are characterized by extreme hydrological and thermal conditions. These freshwater systems have very particular features as a result of their strong irregularity of flow due to limited precipitation runoff regime, leading to strong seasonal hydrologic fluctuations. The current study focused on the spatio-temporal distribution of chironomids in 28 sampling sites spread across the Northern Tunisia. By emplying PERMANOVA, the results indicated a significant spatio-temporal variation along various environmental gradients. The main abiotic factors responsible for noted differences in the spatial distribution of chironomids in wadi were the conductivity and temperature, closely followed by altitude, pH, salinity, talweg slope and dissolved oxygen, identified as such by employing distance-based linear models' procedure. The Distance-based redundancy analysis ordination showed two main groups: the first clustered the Bizerte sites, which were characterized by high water conductivity, sodium concentration and salinity. The second main group comprised sites from the Tell zone and was characterized by low temperatures, neutral pH, low conductivity and nutrients content. The subfamily TANYPODIINAE (e.g., Prochladius sp., Prochladius choerus (Meigen, 1804) and Macropelopia sp.) was the dominant group at Tell zone, whereas species such as Diamesa starmachi (Kownacki et Kownacha, 1970) and Potthastia gaedii (Meigen, 1838) were found only in Tell Wadis. In contrast, chironomid species such as Diamesa starmachi (Kownacki et Kownacha, 1970), Potthastia gaedii (Meigen, 1838), Procladius choreus (Meigen, 1804) were specific for Tell Mountain. Cap Bon wadis region was dominated by genus Cladotanytarsus sp. The results of this survey liked the taxonomic composition of chironomid assemblages to the variation of hydromorphological and physic-chemical gradients across the northern Tunisia wadis.
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A connected cytoskeleton network generates axonal tension in embryonic Drosophila. LAB ON A CHIP 2019; 19:3133-3139. [PMID: 31435630 DOI: 10.1039/c9lc00243j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Axons of neurons are contractile, i.e., they actively maintain a rest tension. However, the spatial origin of this contractility along the axon and the role of the cytoskeleton in generating tension and sustaining rigidity are unknown. Here, using a microfluidic platform, we exposed a small segment of the axons of embryonic Drosophila motor neurons to specific cytoskeletal disruption drugs. We observed that a local actomyosin disruption led to a total loss in axonal tension, with the stiffness of the axon remaining unchanged. A local disruption of microtubules led to a local reduction in bending stiffness, while tension remained unchanged. These observations demonstrated that contractile forces are generated and transferred along the entire length of the axon in a serial fashion. Thus, a local force disruption results in a collapse of tension of the entire axon. This mechanism potentially provides a pathway for rapid tension regulation to facilitate physiological processes that are influenced by axonal tension.
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Cancer Cells Invade Confined Microchannels via a Self-Directed Mesenchymal-to-Amoeboid Transition. NANO LETTERS 2019; 19:2280-2290. [PMID: 30775927 PMCID: PMC6463244 DOI: 10.1021/acs.nanolett.8b04720] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 02/11/2019] [Indexed: 05/30/2023]
Abstract
Cancer cell invasion through physical barriers in the extracellular matrix (ECM) requires a complex synergy of traction force against the ECM, mechanosensitive feedback, and subsequent cytoskeletal rearrangement. PDMS microchannels were used to investigate the transition from mesenchymal to amoeboid invasion in cancer cells. Migration was faster in narrow 3 μm-wide channels than in wider 10 μm channels, even in the absence of cell-binding ECM proteins. Cells permeating narrow channels exhibited blebbing and had smooth leading edge profiles, suggesting an ECM-induced transition from mesenchymal invasion to amoeboid invasion. Live cell labeling revealed a mechanosensing period in which the cell attempts mesenchymal-based migration, reorganizes its cytoskeleton, and proceeds using an amoeboid phenotype. Rho/ROCK (amoeboid) and Rac (mesenchymal) pathway inhibition revealed that amoeboid invasion through confined environments relies on both pathways in a time- and ECM-dependent manner. This demonstrates that cancer cells can dynamically modify their invasion programming to navigate physically confining matrix conditions.
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Recent Advances in Micro, Nano, and Cell Mechanics. EXPERIMENTAL MECHANICS 2019; 59:10.1007/s11340-019-00497-0. [PMID: 31579325 PMCID: PMC6774201 DOI: 10.1007/s11340-019-00497-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
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Biophysics of Tumor Microenvironment and Cancer Metastasis - A Mini Review. Comput Struct Biotechnol J 2018; 16:279-287. [PMID: 30128085 PMCID: PMC6097544 DOI: 10.1016/j.csbj.2018.07.003] [Citation(s) in RCA: 157] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2018] [Revised: 07/20/2018] [Accepted: 07/21/2018] [Indexed: 02/07/2023] Open
Abstract
The role of tumor microenvironment in cancer progression is gaining significant attention. It is realized that cancer cells and the corresponding stroma co-evolve with time. Cancer cells recruit and transform the stromal cells, which in turn remodel the extra cellular matrix of the stroma. This complex interaction between the stroma and the cancer cells results in a dynamic feed-forward/feed-back loop with biochemical and biophysical cues that assist metastatic transition of the cancer cells. Although biochemistry has long been studied for the understanding of cancer progression, biophysical signaling is emerging as a critical paradigm determining cancer metastasis. In this mini review, we discuss the role of one of the biophysical cues, mostly the mechanical stiffness of tumor microenvironment, in cancer progression and its clinical implications.
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Key Words
- ADAMs, Adamalysins
- ANGPT2, Angiopoietin 2
- Activin/TGFβ
- CAF, Cancer associated fibroblast
- CSF-1, Colony stimulating factor 1
- CTGF, Connective tissue growth factor
- CYR61/CCN1, Cysteine-rich angiogenic inducer 61/CCN family member 1
- Cancer
- ECM stiffness
- ECM, Extracellular matrix
- EGF, Epidermal growth factor
- EMT, Epithelial to mesenchymal transition
- FGF, Fibroblast growth factor
- Growth factors
- HGF/SF, Hepatocyte growth factor/Scatter factor
- IGFs, Insulin-like growth factors
- IL-13, Interleukin-13
- IL-33, Interleukin-33
- IL-6, Interleukin-6
- KGF, Keratinocyte growth factor, also FGF7
- LOX, Lysyl Oxidase
- MMPs, Matrix metalloproteinases
- Metastasis
- NO, Nitric oxide
- SDF-1/CXCL12, Stromal cell-derived factor 1/C-X-C motif chemokine 12
- TACs, Tumor-associated collagen signatures
- TGFβ, Transforming growth factor β
- TNF-α, Tumor necrosis factor-α
- Tumor biophysics
- VEGF, Vascular endothelial growth factor
- α-SMA, α-Smooth muscle actin
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A simple microfluidic platform for the partial treatment of insuspendable tissue samples with orientation control. LAB ON A CHIP 2018; 18:735-742. [PMID: 29362759 DOI: 10.1039/c7lc00984d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Microfluidic devices have extensively been applied to study biological samples, including single cells. Exploiting laminar flows on a small scale, microfluidics allow for the selective and partial exposure of samples to various chemical treatments. Traditionally, suspendable samples are first flowed into formed microchannels and are allowed to adhere to the channel floor randomly with no control over sample placement or orientation, before being subjected to partial treatment. This severely limits the choice of samples and the extent of sample preparations. Here, we overcame this limit by reversing the sequence. We prepared the samples first on glass substrates. A patterned silicone slab was then placed on the substrate to form channels at an appropriate orientation with respect to the sample. We used liquid silicone rubber (LSR) as the base material. Its compliance (low elastic modulus) and its adhesion to glass offer the necessary seal to form the microchannels naturally. The applicability of the device was demonstrated by testing single axons of embryonic Drosophila motor neurons in vivo. A segment of the axons was subjected to drugs that inhibit myosin activities or block voltage-gated sodium ion channels. In response, the axons reduced the clustering of neuro-transmitter vesicles at the presynaptic terminal of neuromuscular junctions, or increased the calcium intake and underwent membrane hyperpolarization, respectively. Such fundamental studies cannot be carried out using conventional microfluidics.
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Cell-Extracellular Matrix Mechanobiology: Forceful Tools and Emerging Needs for Basic and Translational Research. NANO LETTERS 2018; 18:1-8. [PMID: 29178811 PMCID: PMC5842374 DOI: 10.1021/acs.nanolett.7b04982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Extracellular biophysical cues have a profound influence on a wide range of cell behaviors, including growth, motility, differentiation, apoptosis, gene expression, adhesion, and signal transduction. Cells not only respond to definitively mechanical cues from the extracellular matrix (ECM) but can also sometimes alter the mechanical properties of the matrix and hence influence subsequent matrix-based cues in both physiological and pathological processes. Interactions between cells and materials in vitro can modify cell phenotype and ECM structure, whether intentionally or inadvertently. Interactions between cell and matrix mechanics in vivo are of particular importance in a wide variety of disorders, including cancer, central nervous system injury, fibrotic diseases, and myocardial infarction. Both the in vitro and in vivo effects of this coupling between mechanics and biology hold important implications for clinical applications.
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Modulation of Synaptic Vesicles Clustering by Axonal Tension. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Mechanism of Axonal Contractility in Embryonic Drosophila Motor Neurons in Vivo. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.1719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Stretch induced hyperexcitability of mice callosal pathway. Front Cell Neurosci 2015; 9:292. [PMID: 26300729 PMCID: PMC4525056 DOI: 10.3389/fncel.2015.00292] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 07/15/2015] [Indexed: 01/09/2023] Open
Abstract
Memory and learning are thought to result from changes in synaptic strength. Previous studies on synaptic physiology in brain slices have traditionally been focused on biochemical processes. Here, we demonstrate with experiments on mouse brain slices that central nervous system plasticity is also sensitive to mechanical stretch. This is important, given the host of clinical conditions involving changes in mechanical tension on the brain, and the normal role that mechanical tension plays in brain development. A novel platform is developed to investigate neural responses to mechanical stretching. Flavoprotein autofluoresence (FA) imaging was employed for measuring neural activity. We observed that synaptic excitability substantially increases after a small (2.5%) stretch was held for 10 min and released. The increase is accumulative, i.e., multiple stretch cycles further increase the excitability. We also developed analytical tools to quantify the spatial spread and response strength. Results show that the spatial spread is less stable in slices undergoing the stretch-unstretch cycle. FA amplitude and activation rate decrease as excitability increases in stretch cases but not in electrically enhanced cases. These results collectively demonstrate that a small stretch in physiological range can modulate neural activities significantly, suggesting that mechanical events can be employed as a novel tool for the modulation of neural plasticity.
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The effects of weight loss after bariatric surgery on health-related quality of life and depression. Nutr Diabetes 2014; 4:e132. [PMID: 25177912 PMCID: PMC4183970 DOI: 10.1038/nutd.2014.29] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 07/02/2014] [Accepted: 07/20/2014] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND In severe obesity, impairments in health-related quality of life (HRQoL) and dysphoric mood are reported. This is a post-surgery analysis of the relationship between HRQoL and depressive symptoms, and weight change after four different types of bariatric procedures. METHODS A total of 105 consented patients completed the Short-Form-36 Health Survey (SF-36), the Impact of Weight on Quality of Life-Lite (IWQOL-Lite) and the Beck Depression Inventory (BDI) before and 25 months after surgery. Analysis of variance or Kruskal-Wallis test evaluated changes. RESULTS Patients with Roux-en Y gastric bypass (46 patients), decreased body mass indexes (BMIs; kg m(-)(2)) 47-31 kg m(-)(2) (P<0.0001); biliopancreatic diversion with duodenal switch (18 patients), decreased BMIs 57-30 kg m(-)(2) (P<0.0001); adjustable gastric banding (18 patients), decreased BMIs 45-38 kg m(-)(2) (P<0.0001); and sleeve gastrectomies (23 patients), decreased BMIs 58 42 kg m(-)(2) (P<0.0001). The excess percentage BMI loss was 69, 89, 36 and 53 kg m(-)(2), respectively (P<0.0001). Before surgery, the SF-36 differences were significant regarding bodily pain (P=0.008) and social functioning (P=0.01). After surgery, physical function (P=0.03), general health (P=0.05) and physical component (P=0.03) were different. IWQOL-Lite recorded no differences until after surgery: physical function (P=0.003), sexual life (P=0.04) and public distress (P=0.003). BDI scores were not different for the four groups at baseline. All improved with surgery, 10.6-4.4 (P=0.0001). CONCLUSIONS HRQoL and depressive symptoms significantly improvement after surgery. These improvements do not have a differential effect over the wide range of weight change.Nutrition & Diabetes (2014) 4, e132; doi:10.1038/nutd.2014.29; published online 1 September 2014.
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Cardiac myocytes' dynamic contractile behavior differs depending on heart segment. Biotechnol Bioeng 2012; 110:628-36. [PMID: 22952006 DOI: 10.1002/bit.24725] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Revised: 08/28/2012] [Accepted: 08/30/2012] [Indexed: 11/11/2022]
Abstract
Cardiac myocytes originating from different parts of the heart exhibit varying morphology and ultrastructure. However, the difference in their dynamic behavior is unclear. We examined the contraction of cardiac myocytes originating from the apex, ventricle, and atrium, and found that their dynamic behavior, such as amplitude and frequency of contraction, differs depending on the heart segment of origin. Using video microscopy and high-precision image correlation, we found that: (1) apex myocytes exhibited the highest contraction rate (∼17 beats/min); (2) ventricular myocytes exhibited the highest contraction amplitude (∼5.2 micron); and (3) as myocyte contraction synchronized, their frequency did not change significantly, but the amplitude of contraction increased in apex and ventricular myocytes. In addition, as myocyte cultures mature they formed contractile filaments, further emphasizing the difference in myocyte dynamics is persistent. These results suggest that the dynamic behavior (in addition to static properties) of myocytes is dependent on their segment of origin.
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Multi-material bio-fabrication of hydrogel cantilevers and actuators with stereolithography. LAB ON A CHIP 2012; 12:88-98. [PMID: 22124724 DOI: 10.1039/c1lc20688e] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Cell-based biohybrid actuators are integrated systems that use biological components including proteins and cells to power material components by converting chemical energy to mechanical energy. The latest progress in cell-based biohybrid actuators has been limited to rigid materials, such as silicon and PDMS, ranging in elastic moduli on the order of mega (10(6)) to giga (10(9)) Pascals. Recent reports in the literature have established a correlation between substrate rigidity and its influence on the contractile behavior of cardiomyocytes (A. J. Engler, C. Carag-Krieger, C. P. Johnson, M. Raab, H. Y. Tang and D. W. Speicher, et al., J. Cell Sci., 2008, 121(Pt 22), 3794-3802, P. Bajaj, X. Tang, T. A. Saif and R. Bashir, J. Biomed. Mater. Res., Part A, 2010, 95(4), 1261-1269). This study explores the fabrication of a more compliant cantilever, similar to that of the native myocardium, with elasticity on the order of kilo (10(3)) Pascals. 3D stereolithographic technology, a layer-by-layer UV polymerizable rapid prototyping system, was used to rapidly fabricate multi-material cantilevers composed of poly(ethylene glycol) diacrylate (PEGDA) and acrylic-PEG-collagen (PC) mixtures. The incorporation of acrylic-PEG-collagen into PEGDA-based materials enhanced cell adhesion, spreading, and organization without altering the ability to vary the elastic modulus through the molecular weight of PEGDA. Cardiomyocytes derived from neonatal rats were seeded on the cantilevers, and the resulting stresses and contractile forces were calculated using finite element simulations validated with classical beam equations. These cantilevers can be used as a mechanical sensor to measure the contractile forces of cardiomyocyte cell sheets, and as an early prototype for the design of optimal cell-based biohybrid actuators.
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In-Situ Mechanical Characterization of a Freestanding 100 Nanometer Thick Aluminum Film in SEM Using MEMS Sensors. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-695-l8.7.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTWe present the uniaxial stress-strain response of a freestanding 100 nanometer thick 99.99% pure sputtered Aluminum film with grain size about 60 nanometers, tested in-situ inside a SEM chamber. The specimen is cofabricated with MEMS force and displacement sensors to minimize the experimental setup size, allowing both quantitative and in-situ tests to be performed in SEM and TEM chambers. The experimental results strongly suggest that at this size scale, a) Elastic modulus remains same as the bulk Aluminum, b) Yielding starts at about 625 MPa, and c) Strain hardening effect is absent, which indirectly suggests the deformation at this size scale is not dislocation mechanism based.
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Reversible and repeatable linear local cell force response under large stretches. Exp Cell Res 2005; 305:42-50. [PMID: 15777786 DOI: 10.1016/j.yexcr.2004.12.026] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2004] [Revised: 12/16/2004] [Accepted: 12/16/2004] [Indexed: 11/29/2022]
Abstract
Large stretching and un-stretching force response of adherent fibroblasts is measured by micromachined mechanical force sensors. The force sensors are composed of a probe and flexible beams. The probe, functionalized by fibronectin, is used to contact the cells. The flexible beams are the sensing element. The sensors are made of single crystal silicon and fabricated by the SCREAM process. The maximum cell stretch reached is approximately 50 microm, which is about twice of the cell initial size, and the time delay between two consecutive stretching/un-stretching steps is 75 s unless otherwise stated. We find that the force response of the cells is strongly linear, reversible, and repeatable, with a small stiffening at the initial deformation stage. Force response of single cells measured before and after cytochalasin D treatment suggests that actin filaments take almost all the cell internal forces due to stretch. These findings may shed light on the increasing understanding on the mechanical behavior of cells and provide clues for making new classes of biological materials having uncommon properties.
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