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Buckhurst HD, Gilmartin B, Lam A, Cubbidge RP, Logan NS. In vivo measures of anterior scleral resistance in humans with rebound tonometry. Ophthalmic Physiol Opt 2020; 40:472-481. [PMID: 32495401 DOI: 10.1111/opo.12695] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 04/10/2020] [Accepted: 04/14/2020] [Indexed: 11/30/2022]
Abstract
PURPOSE To measure regional variations in anterior scleral resistance (ASR) using a ballistic rebound tonometer (RBT) and examine whether the variations are significantly affected by ethnicity and refractive error (RE). METHODS ASR was measured using a RBT (iCare TA01) following calibration against the biomechanical properties of agarose biogels. Eight scleral regions (nasal, temporal, superior, inferior, inferior-nasal, inferior-temporal, superior-nasal and superior-temporal) were measured at locations 4mm from the limbus. Subjects were 130 young adults comprising three ethnic groups whose RE distributions [MSE (D) ± S.D.] incorporated individuals categorised as without-myopia (NM; MSE ≥ -0.50) and with-myopia (WM; MSE < -0.50); British-White (BW): 26 NM + 0.52 ± 1.15D; 22 WM -3.83 ± 2.89D]; British-South-Asian (BSA): [9 NM + 0.49 ± 1.06D; 11 WM -5.07 ± 3.76D; Hong-Kong-Chinese (HKC): [11 NM + 0.39 ± 0.66D; 49 WM -4.46 ± 2.70D]. Biometric data were compiled using cycloplegic open-field autorefraction and the Zeiss IOLMaster. Two- and three-way repeated measures analysis of variances (anovas) tested regional differences for RBT values across both refractive status and ethnicity whilst stepwise forward multiple linear regression was used as an exploratory test. RESULTS Significant regional variations in ASR were identified for the BW, BSA and HKC (p < 0.001) individuals; superior-temporal region showed the lowest levels of resistance whilst the inferior-nasal region the highest. Compared to the BW and BSA groups, the HKC subjects displayed a significant increase in mean resistance for each respective region (p < 0.001). With the exception of the inferior region, ethnicity was found to be the chief predictor for variation in the scleral RBT values for all other regions. Mean RE group differences were insignificant. CONCLUSIONS The novel application of RBT to the anterior sclera confirm regional variation in ASR. Greater ASR amongst the HKC group than the BW and BSA individuals suggests that ethnic differences in anterior scleral biomechanics may exist.
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Affiliation(s)
- Hetal D Buckhurst
- Eye and Vision Research Group, School of Health Professions, Faculty of Health, Plymouth University, Plymouth, UK
| | | | - Andrew Lam
- School of Optometry, The Hong Kong Polytechnic University, Kowloon, Hong Kong
| | | | - Nicola S Logan
- School of Life & Health Sciences, Aston University, Birmingham, UK
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2
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Alsaykhan H, Paxton JZ. Investigating materials and orientation parameters for the creation of a 3D musculoskeletal interface co-culture model. Regen Biomater 2020; 7:413-425. [PMID: 32793386 PMCID: PMC7415002 DOI: 10.1093/rb/rbaa018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 03/11/2020] [Accepted: 03/29/2020] [Indexed: 12/15/2022] Open
Abstract
Musculoskeletal tissue interfaces are a common site of injury in the young, active populations. In particular, the interface between the musculoskeletal tissues of tendon and bone is often injured and to date, no single treatment has been able to restore the form and function of damaged tissue at the bone–tendon interface. Tissue engineering and regeneration hold great promise for the manufacture of bespoke in vitro models or implants to be used to advance repair and so this study investigated the material, orientation and culture choices for manufacturing a reproducible 3D model of a musculoskeletal interface between tendon and bone cell populations. Such models are essential for future studies focussing on the regeneration of musculoskeletal interfaces in vitro. Cell-encapsulated fibrin hydrogels, arranged in a horizontal orientation though a simple moulding procedure, were shown to best support cellular growth and migration of cells to form an in vitro tendon–bone interface. This study highlights the importance of acknowledging the material and technical challenges in establishing co-cultures and suggests a reproducible methodology to form 3D co-cultures between tendon and bone, or other musculoskeletal cell types, in vitro.
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Affiliation(s)
- Hamad Alsaykhan
- Anatomy@Edinburgh, Edinburgh Medical School: Biomedical Sciences, The University of Edinburgh, Teviot Place, Edinburgh EH8 9AG, UK.,Department of Basic Medical Sciences, College of Medicine and Health Sciences, Qassim University, PO Box 991, 51911 Unaizah Campus, Al-Qassim 51911, Saudi Arabia
| | - Jennifer Z Paxton
- Anatomy@Edinburgh, Edinburgh Medical School: Biomedical Sciences, The University of Edinburgh, Teviot Place, Edinburgh EH8 9AG, UK
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3
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Focal adhesion signaling affects regeneration by human nucleus pulposus cells in collagen- but not carbohydrate-based hydrogels. Acta Biomater 2018; 66:238-247. [PMID: 29174589 DOI: 10.1016/j.actbio.2017.11.029] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 10/26/2017] [Accepted: 11/17/2017] [Indexed: 01/07/2023]
Abstract
Hydrogel-based 3D cell cultures are an emerging strategy for the regeneration of cartilage. In an attempt to regenerate dysfunctional intervertebral discs, nucleus pulposus (NP) cells can be cultured in hydrogels of various kinds and physical properties. Stiffness sensing through focal adhesions is believed to direct chondrogenesis, but the mechanisms by which this works are largely unknown. In this study we compared focal adhesion formation and glycosaminoglycan (GAG) deposition by NP cells in a range of hydrogels. Using a focal adhesion kinase (FAK) inhibitor, we demonstrated that focal adhesion signaling is involved in the response of NP cells in hydrogels that contain integrin binding sites (i.e. methacrylated gelatin (gelMA) and type II collagen), but not in hydrogels deplete from integrin binding sites such as alginate and agarose, or CD44-binding hydrogels based on hyaluronic acid. As a result of FAK inhibition we observedenhanced proteoglycan production in gelMA, but decreased production in type II collagen hydrogels, which could be explained by alteration in cell fate as supported by the increase in the adipogenic marker peroxisome proliferator-activated receptor gamma (PPARy). Furthermore, GAG deposition was inversely proportional to polymer concentration in integrin-binding gelMA, while no direct relationship was found for the non-integrin binding gels alginate and agarose. This corroborates our finding that focal adhesion formation plays an important role in NP cell response to its surrounding matrix. STATEMENT OF SIGNIFICANCE Biomaterials are increasingly being investigated for regenerative medicine applications, including regeneration of the nucleus pulposus. Cells interact with their environment and are influenced by extracellular matrix or polymer properties. Insight in these interactions can improve regeneration and helps to understand degeneration processes. The role of focal adhesion formation in the regenerative response of nucleus pulposus cells is largely unknown. Therefore, the relation between materials, stiffness and focal adhesion formation is studied here.
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4
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Pollot BE, Rathbone CR, Wenke JC, Guda T. Natural polymeric hydrogel evaluation for skeletal muscle tissue engineering. J Biomed Mater Res B Appl Biomater 2017; 106:672-679. [PMID: 28306190 DOI: 10.1002/jbm.b.33859] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 12/15/2016] [Accepted: 01/26/2017] [Indexed: 11/10/2022]
Abstract
Although skeletal muscle has a remarkable ability to repair/regenerate after most types of injuries, there is limited regeneration after volumetric muscle loss (VML). A number of scaffold materials have been used in the development of grafts to treat VML, however, there is still a need to better understand the most appropriate material with regards to its ability to maintain mechanical integrity while also supporting myogenesis. Five commonly used natural polymeric materials (Collagen I, Agarose, Alginate, Fibrin, and Collagen Chitosan) used in skeletal muscle tissue engineering grafts were evaluated for their mechanical properties and myogenic capacity. Rheological properties, water absorption rates, degradation stability, tensile characteristics, and the ability to support in vitro myogenesis were compared in all five materials. Collagen, Collagen Chitosan, and Fibrin demonstrated high elasticity and 100% stretch without failure, Agarose was the most brittle (20% max stretch), and Alginate demonstrated poor handleabilty. While Collagen was supportive of myogenesis, overall, Fibrin demonstrated the highest myogenic potential as indicated by the earliest and highest increases in myogenin and myosin heavy chain mRNA in satellite cells along with the most extensive myotube development as evaluated with immunohistochemistry. The findings herein support the notion that under the conditions used in this study, Fibrin is the most suitable scaffold for the development of scaffolds for skeletal muscle tissue engineering. Future studies are required to determine whether the differences in mechanical properties and myogenic potential observed in vitro in the current study translate to better skeletal muscle development in a VML injury model. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 672-679, 2018.
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Affiliation(s)
- Beth E Pollot
- Department of Biomedical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas, 78249.,Extremity Trauma & Regenerative Medicine Task Area, United States Army Institute of Surgical Research, Fort Sam Houston, Texas, 78234
| | - Christopher R Rathbone
- Extremity Trauma & Regenerative Medicine Task Area, United States Army Institute of Surgical Research, Fort Sam Houston, Texas, 78234
| | - Joseph C Wenke
- Extremity Trauma & Regenerative Medicine Task Area, United States Army Institute of Surgical Research, Fort Sam Houston, Texas, 78234
| | - Teja Guda
- Department of Biomedical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas, 78249
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5
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Mao B, Bentaleb A, Louerat F, Divoux T, Snabre P. Heat-induced aging of agar solutions: Impact on the structural and mechanical properties of agar gels. Food Hydrocoll 2017. [DOI: 10.1016/j.foodhyd.2016.10.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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6
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Khavari A, Nydén M, Weitz DA, Ehrlicher AJ. Composite alginate gels for tunable cellular microenvironment mechanics. Sci Rep 2016; 6:30854. [PMID: 27484403 PMCID: PMC4971458 DOI: 10.1038/srep30854] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 07/08/2016] [Indexed: 01/06/2023] Open
Abstract
The mechanics of the cellular microenvironment can be as critical as biochemistry in directing cell behavior. Many commonly utilized materials derived from extra-cellular-matrix create excellent scaffolds for cell growth, however, evaluating the relative mechanical and biochemical effects independently in 3D environments has been difficult in frequently used biopolymer matrices. Here we present 3D sodium alginate hydrogel microenvironments over a physiological range of stiffness (E = 1.85 to 5.29 kPa), with and without RGD binding sites or collagen fibers. We use confocal microscopy to measure the growth of multi-cellular aggregates (MCAs), of increasing metastatic potential in different elastic moduli of hydrogels, with and without binding factors. We find that the hydrogel stiffness regulates the growth and morphology of these cell clusters; MCAs grow larger and faster in the more rigid environments similar to cancerous breast tissue (E = 4–12 kPa) as compared to healthy tissue (E = 0.4–2 kpa). Adding binding factors from collagen and RGD peptides increases growth rates, and change maximum MCA sizes. These findings demonstrate the utility of these independently tunable mechanical/biochemistry gels, and that mechanical confinement in stiffer microenvironments may increase cell proliferation.
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Affiliation(s)
- Adele Khavari
- Applied Chemistry, Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.,SUMO Biomaterials VINN Excellence Center, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
| | - Magnus Nydén
- Applied Chemistry, Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.,UCL Australia, 220 Victoria Square, Adelaide, SA 5000 Australia
| | - David A Weitz
- Department of Bioengineering, McGill University, Montreal Canada H3A 0C3
| | - Allen J Ehrlicher
- Department of Bioengineering, McGill University, Montreal Canada H3A 0C3.,School of Engineering and Applied Sciences, Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.,Beth Israel Deaconess Medical Center, Boston, Massachusetts 02115, United States.,Harvard Medical School, Boston, Massachusetts 02115, United States
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7
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Nayar VT, Weiland JD, Hodge AM. Macrocompression and Nanoindentation of Soft Viscoelastic Biological Materials. Tissue Eng Part C Methods 2012; 18:968-75. [DOI: 10.1089/ten.tec.2012.0034] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
Affiliation(s)
- V. Timothy Nayar
- Doheny Eye Institute, University of Southern California, Los Angeles, California
| | - James D. Weiland
- Doheny Eye Institute, University of Southern California, Los Angeles, California
| | - Andrea M. Hodge
- Department of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, California
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Strambini LM, Longo A, Diligenti A, Barillaro G. A minimally invasive microchip for transdermal injection/sampling applications. LAB ON A CHIP 2012; 12:3370-3379. [PMID: 22773092 DOI: 10.1039/c2lc40348j] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The design, fabrication, and characterization of a minimally invasive silicon microchip for transdermal injection/sampling applications are reported and discussed. The microchip exploits an array of silicon-dioxide hollow microneedles with density of one million needles cm(-2) and lateral size of a few micrometers, protruding from the front-side chip surface for one hundred micrometers, to inject/draw fluids into/from the skin. The microneedles are in connection with independent reservoirs grooved on the back-side of the chip. Insertion experiments of the microchip in skin-like polymers (agarose hydrogels with concentrations of 2% and 4% wt) demonstrate that the microneedles successfully withstand penetration without breaking, despite their high density and small size, according to theoretical predictions. Operation of the microchip with different liquids of biomedical interest (deionized water, NaCl solution, and d-glucose solution) at different differential pressures, in the range 10-100 kPa, highlights that the flow-rate through the microneedles is linearly dependent on the pressure-drop, despite the small section area (about 13 μm(2)) of the microneedle bore, and can be finely controlled from a few ml min(-1) up to tens of ml min(-1). Evaporation (at room temperature) and acceleration (up to 80 g) losses through the microneedles are also investigated to quantify the ability of the chip in storing liquids (drug to be delivered or collected fluid) in the reservoir, and result to be of the order of 70 nl min(-1) and 1300 nl min(-1), respectively, at atmospheric pressure and room temperature.
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Affiliation(s)
- Lucanos M Strambini
- Dipartimento di Ingegneria dell'Informazione: Elettronica, Informatica, Telecomunicazioni, Università di Pisa, via G. Caruso 16, 56122, Pisa, Italy
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9
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Puértolas JA, Vadillo JL, Sánchez-Salcedo S, Nieto A, Gómez-Barrena E, Vallet-Regí M. Mullins effect behaviour under compression in micelle-templated silica and micelle-templated silica/agarose systems. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2012; 23:229-238. [PMID: 22076528 DOI: 10.1007/s10856-011-4482-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Accepted: 10/31/2011] [Indexed: 05/31/2023]
Abstract
The mechanical properties of bioceramic conformed pieces based on micelle-templated silica (MTS) such as SBA15, MCM41 and MCM48 as well as MTS/agarose systems have been evaluated under static and cyclic compressive tests. The MTS pieces exhibited a brittle behaviour. Agarose, a biocompatible and biodegradable hydrogel, has been used to shape ceramic-agarose pieces following a low temperature shaping method. Agarose conferred toughness, ductility and a rubbery consistency up to a 60% strain in ceramic MTS/agarose systems leading to a maximum strength of 10-50 MPa, without losing their initial cylindrical structure. This combination of ceramic and organic matrix contributes to avoiding the inherent brittleness of the bioceramic and enhances the compression resistance of hydrogel. The presence of mechanical hysteresis, permanent deformation after the first cycle and recovery of the master monotonous curve of MTS/agarose systems indicate a Mullins-like effect similar to that found in carbon-filled rubber systems. We report this type of mechanical behaviour, the Mullins effect, for the first time in MTS bioceramics and MTS bioceramic/agarose systems.
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Affiliation(s)
- J A Puértolas
- Department of Materials Science and Technology, Instituto de Investigaciones en Ingeniería de Aragón, I3A, Universidad de Zaragoza, Zaragoza, Spain
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10
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Liu Q, Subhash G, Moore DF. Loading velocity dependent permeability in agarose gel under compression. J Mech Behav Biomed Mater 2011; 4:974-82. [DOI: 10.1016/j.jmbbm.2011.02.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 02/11/2011] [Accepted: 02/17/2011] [Indexed: 10/18/2022]
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11
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Roberts JJ, Earnshaw A, Ferguson VL, Bryant SJ. Comparative study of the viscoelastic mechanical behavior of agarose and poly(ethylene glycol) hydrogels. J Biomed Mater Res B Appl Biomater 2011; 99:158-69. [DOI: 10.1002/jbm.b.31883] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Revised: 03/13/2011] [Accepted: 04/10/2011] [Indexed: 11/08/2022]
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12
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Li C, Allen J, Alliston T, Pruitt LA. The use of polyacrylamide gels for mechanical calibration of cartilage--a combined nanoindentation and unconfined compression study. J Mech Behav Biomed Mater 2011; 4:1540-7. [PMID: 21783163 DOI: 10.1016/j.jmbbm.2011.02.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Revised: 02/04/2011] [Accepted: 02/08/2011] [Indexed: 10/18/2022]
Abstract
This study investigates polyacrylamide (PA) gel as a calibration material to measure the nanomechanical compressive modulus of cartilage using nanoindentation. Both nanoindentation and unconfined compression testing were performed on PA gel and porcine rib cartilage. The equilibrium moduli measured by the two methods were discernable. Nanoindentation has the advantage of distinguishing between spatially dependent constituent properties that affect tissue mechanical function in heterogeneous and hierarchically structured tissues such as cartilage. Both sets of measurements exhibited similar positive correlation with increasing gel crosslinker concentration. The compressive modulus measurements from compression in the PA gels ranged from 300 kPa-1.4 MPa, whereas those from nanoindentation ranged from 100 kPa-1.1 MPa. Using this data, a method for relating nanoindentation measurements to conventional mechanical property measurements is presented for porcine rib cartilage. It is shown that based on this relationship, the local tissue modulus as measured from nanoindentation (1.1-1.4 MPa) was able to predict the overall global modulus of the same sample of rib cartilage (2.2 MPa), as confirmed by experimental measurements from unconfined compression. This study supports the use of nanoindentation for the local characterization of cartilage tissues and may be applied to other soft tissues and constructs.
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Affiliation(s)
- Cheng Li
- UCSF and UC Berkeley Joint Graduate Group in Bioengineering, University of California, Berkeley, CA 94720, United States.
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13
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Puértolas J, Vadillo J, Sánchez-Salcedo S, Nieto A, Gómez-Barrena E, Vallet-Regí M. Compression behaviour of biphasic calcium phosphate and biphasic calcium phosphate-agarose scaffolds for bone regeneration. Acta Biomater 2011; 7:841-7. [PMID: 20709633 DOI: 10.1016/j.actbio.2010.07.032] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 07/01/2010] [Accepted: 07/25/2010] [Indexed: 10/19/2022]
Abstract
There is an acknowledged need for shaping 3-D scaffolds with adequate porosity and mechanical properties for biomedical applications. The mechanical properties under static and cyclic compressive testing of dense and designed porous architecture bioceramic scaffolds based on the biphasic calcium phosphate (BCP) systems and BCP-agarose systems have been evaluated. The dense and designed porous architecture scaffolds in BCP systems exhibited a brittle behaviour. Agarose, a biocompatible and biodegradable hydrogel, has been used to shape designed architecture ceramic-agarose scaffolds following a low-temperature shaping method. Agarose conferred toughness, ductility and a rubbery consistency for strains of up to 60% of in ceramic BCP-agarose systems. This combination of ceramic and organic matrix helps to avoid the inherent brittleness of the bioceramic and enhances the compression resistance of hydrogel. The presence of mechanical hysteresis, permanent deformation after the first cycle and recovery of the master monotonous curve indicate a Mullins-like effect such as that observed in carbon-filled rubber systems. We report this type of mechanical behaviour, the Mullins effect, for the first time in bioceramics and bioceramic-agarose systems.
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14
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Buckley CT, Thorpe SD, O’Brien FJ, Robinson AJ, Kelly DJ. The effect of concentration, thermal history and cell seeding density on the initial mechanical properties of agarose hydrogels. J Mech Behav Biomed Mater 2009; 2:512-21. [DOI: 10.1016/j.jmbbm.2008.12.007] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Revised: 12/18/2008] [Accepted: 12/19/2008] [Indexed: 10/21/2022]
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15
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Saxena T, Gilbert JL, Hasenwinkel JM. A versatile mesoindentation system to evaluate the micromechanical properties of soft, hydrated substrates on a cellular scale. J Biomed Mater Res A 2009; 90:1206-17. [DOI: 10.1002/jbm.a.32178] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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16
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Cheng G, Tse J, Jain RK, Munn LL. Micro-environmental mechanical stress controls tumor spheroid size and morphology by suppressing proliferation and inducing apoptosis in cancer cells. PLoS One 2009; 4:e4632. [PMID: 19247489 PMCID: PMC2645686 DOI: 10.1371/journal.pone.0004632] [Citation(s) in RCA: 269] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2008] [Accepted: 01/02/2009] [Indexed: 11/18/2022] Open
Abstract
Background Compressive mechanical stress produced during growth in a confining matrix limits the size of tumor spheroids, but little is known about the dynamics of stress accumulation, how the stress affects cancer cell phenotype, or the molecular pathways involved. Methodology/Principal Findings We co-embedded single cancer cells with fluorescent micro-beads in agarose gels and, using confocal microscopy, recorded the 3D distribution of micro-beads surrounding growing spheroids. The change in micro-bead density was then converted to strain in the gel, from which we estimated the spatial distribution of compressive stress around the spheroids. We found a strong correlation between the peri-spheroid solid stress distribution and spheroid shape, a result of the suppression of cell proliferation and induction of apoptotic cell death in regions of high mechanical stress. By compressing spheroids consisting of cancer cells overexpressing anti-apoptotic genes, we demonstrate that mechanical stress-induced apoptosis occurs via the mitochondrial pathway. Conclusions/Significance Our results provide detailed, quantitative insight into the role of micro-environmental mechanical stress in tumor spheroid growth dynamics, and suggest how tumors grow in confined locations where the level of solid stress becomes high. An important implication is that apoptosis via the mitochondrial pathway, induced by compressive stress, may be involved in tumor dormancy, in which tumor growth is held in check by a balance of apoptosis and proliferation.
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Affiliation(s)
- Gang Cheng
- Edwin L. Steele Laboratory of Tumor Biology, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Janet Tse
- Edwin L. Steele Laboratory of Tumor Biology, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Rakesh K. Jain
- Edwin L. Steele Laboratory of Tumor Biology, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Lance L. Munn
- Edwin L. Steele Laboratory of Tumor Biology, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
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17
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Oxygen consumption of chondrocytes in agarose and collagen gels: a comparative analysis. Biomaterials 2008; 29:1484-93. [PMID: 18191194 DOI: 10.1016/j.biomaterials.2007.12.020] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2007] [Accepted: 12/15/2007] [Indexed: 11/21/2022]
Abstract
The growth of engineered cartilage tissue in vitro is often impaired by the problem of insufficient oxygen and nutrient supply to cells seeded in 3D constructs. Despite its central role in controlling most cell functions, the scaffolding material has generally been thought of only as a transport barrier and its potential active role in controlling oxygen uptake has never been addressed. In this work the role of cell-material interaction on oxygen metabolism in 3D in vitro cultures was surveyed. To this aim bovine chondrocytes, at a cell density of 400,000 and 4,000,000 cells/mL, respectively, were seeded in collagen type I and in agarose, while keeping all other culture conditions constant. A unidirectional oxygen gradient was induced in the culture through the application of a "sandwich" model and the oxygen concentration at the pericellular level was measured by phosphorescence quenching microscopy. Results show that the oxygen consumption rate is two-fold higher in agarose than in collagen, which indicates that the nature of the material strongly influences cell metabolic behaviour. Moreover, since different oxygen consumption rates are linked to different cell biosynthetic activity, our findings will prove beyond any doubt the active role played by materials in tissue regeneration.
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