ASTM F2450-10
(Guide)Standard Guide for Assessing Microstructure of Polymeric Scaffolds for Use in Tissue Engineered Medical Products
Standard Guide for Assessing Microstructure of Polymeric Scaffolds for Use in Tissue Engineered Medical Products
SIGNIFICANCE AND USE
The ability to culture functional tissue to repair damaged or diseased tissues within the body offers a viable alternative to xenografts or heterografts. Using the patient’s own cells to produce the new tissue offers significant benefits by limiting rejection by the immune system. Typically, cells harvested from the intended recipient are cultured in vitro using a temporary housing or scaffold. The microstructure of the scaffold, that is, its porosity, the mean size, and size distribution of pores and their interconnectivity is critical for cell migration, growth and proliferation (Appendix X1). Optimizing the design of tissue scaffolds is a complex task, given the range of available materials, different manufacturing routes, and processing conditions. All of these factors can, and will, affect the surface texture, surface chemistry, and microstructure of the resultant scaffolds. Factors that may or may not be significant variables depend on the characteristics of a given cell type at any given time (that is, changes in cell behavior due to the number of passages, mechanical stimulation, and culture conditions).
Tissue scaffolds are typically assessed using an overall value for scaffold porosity and a range of pore sizes, though the distribution of sizes is rarely quantified. Published mean pore sizes and distributions are usually obtained from electron microscopy images and quoted in the micrometer range. Tissue scaffolds are generally complex structures that are not easily interpreted in terms of pore shape and size, especially in three dimensions. Therefore, it is difficult to quantifiably assess the batch-to-batch variance in microstructure or to make a systematic investigation of the role that the mean pore size and pore size distribution has on influencing cell behavior based solely on electron micrographs (Tomlins et al, (1)).
Fig. 1 gives an indication of potential techniques that can be used to characterize the structure of porous tissue scaffolds and...
SCOPE
1.1 This guide covers an overview of test methods that may be used to obtain information relating to the dimensions of pores, the pore size distribution, the degree of porosity, interconnectivity, and measures of permeability for porous materials used as polymeric scaffolds in the development and manufacture of tissue-engineered medical products (TEMPs). This information is key to optimizing the structure for a particular application, developing robust manufacturing routes, and providing reliable quality control data.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This guide does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to use.
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Designation: F2450 − 10
Standard Guide for
Assessing Microstructure of Polymeric Scaffolds for Use in
1
Tissue-Engineered Medical Products
This standard is issued under the fixed designation F2450; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope brane Filters UsingAutomated Liquid Porosimeter (With-
3
drawn 2008)
1.1 This guide covers an overview of test methods that may
E1441 Guide for Computed Tomography (CT) Imaging
be used to obtain information relating to the dimensions of
F316 Test Methods for Pore Size Characteristics of Mem-
pores, the pore size distribution, the degree of porosity,
brane Filters by Bubble Point and Mean Flow Pore Test
interconnectivity, and measures of permeability for porous
F2150 Guide for Characterization and Testing of Biomate-
materials used as polymeric scaffolds in the development and
rial Scaffolds Used in Tissue-Engineered Medical Prod-
manufacture of tissue-engineered medical products (TEMPs).
ucts
This information is key to optimizing the structure for a
F2603 Guide for Interpreting Images of Polymeric Tissue
particular application, developing robust manufacturing routes,
Scaffolds
and providing reliable quality control data.
3. Terminology
1.2 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
3.1 Definitions:
standard.
3.1.1 bioactive agent, n—any molecular component in, on,
or within the interstices of a device that is intended to elicit a
1.3 This guide does not purport to address all of the safety
desired tissue or cell response.
concerns, if any, associated with its use. It is the responsibility
3.1.1.1 Discussion—Growth factors and antibiotics are typi-
of the user of this standard to establish appropriate safety and
cal examples of bioactive agents. Device structural compo-
health practices and to determine the applicability of regula-
nents or degradation byproducts that evoke limited localized
tory limitations prior to use.
bioactivity are not bioactive agents.
2. Referenced Documents
3.1.2 blind (end)-pore, n—a pore that is in contact with an
2
exposed internal or external surface through a single orifice
2.1 ASTM Standards:
smaller than the pore’s depth.
D2873 Test Method for Interior Porosity of Poly(Vinyl
Chloride) (PVC) Resins by Mercury Intrusion Porosim- 3.1.3 closed cell, n—a void isolated within a solid, lacking
3
etry (Withdrawn 2003)
any connectivity with an external surface. Synonym: closed
D4404 Test Method for Determination of Pore Volume and pore
Pore Volume Distribution of Soil and Rock by Mercury
3.1.4 hydrogel, n—a water-based open network of polymer
Intrusion Porosimetry
chains that are cross-linked either chemically or through
E128 Test Method for Maximum Pore Diameter and Perme-
crystalline junctions or by specific ionic interactions.
ability of Rigid Porous Filters for Laboratory Use
3.1.5 macropore/macroporosity (life sciences),n—a struc-
E1294 Test Method for Pore Size Characteristics of Mem-
ture (including void spaces) sized to allow substantially unre-
stricted passage of chemicals, biomolecules, viruses, bacteria,
and mammalian cells. In implants with interconnecting pores,
1
This guide is under the jurisdiction of ASTM Committee F04 on Medical and
macroporosity provides dimensions that allow for ready tissue
Surgical Materials and Devices and is the direct responsibility of Subcommittee
penetration and microvascularization after implantation. In-
F04.42 on Biomaterials and Biomolecules for TEMPs.
Current edition approved March 1, 2010. Published April 2010. Originally
cludes materials that contain voids with the potential to be
approved in 2004. Last previous edition approved in 2009 as F2450 – 09. DOI:
observable to the naked eye (>100 µm).
10.1520/F2450-10.
2
3.1.6 micropore/microporosity (life sciences),n—a struc-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ture (including void spaces) sized to allow substantially unre-
Standards volume information, refer to the standard’s Document Summary page on
stricted passage of chemicals, biomolecules, and viruses while
the ASTM website.
3
sized to control or moderate the passage of bacteria, mamma-
The last approved version of this historical standard is referenced on
www.astm.org. lian cells, and/or tissue. Includes materials with typical pore
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:F2450–09 Designation: F2450 – 10
Standard Guide for
Assessing Microstructure of Polymeric Scaffolds for Use in
1
Tissue-Engineered Medical Products
This standard is issued under the fixed designation F2450; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This guide covers an overview of test methods that may be used to obtain information relating to the dimensions of pores,
the pore size distribution, the degree of porosity, interconnectivity, and measures of permeability for porous materials used as
polymeric scaffolds in the development and manufacture of tissue-engineered medical products (TEMPs). This information is key
to optimizing the structure for a particular application, developing robust manufacturing routes, and for providing reliable quality
control data.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This guide does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of
the user of this standard to establish appropriate safety and health practices and to determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
D2873 Test Method for Interior Porosity of Poly(Vinyl Chloride) (PVC) Resins by Mercury Intrusion Porosimetry
D4404 Test Method for Determination of Pore Volume and Pore Volume Distribution of Soil and Rock by Mercury Intrusion
Porosimetry
E128 Test Method for Maximum Pore Diameter and Permeability of Rigid Porous Filters for Laboratory Use
E1294 Test Method for Pore Size Characteristics of Membrane Filters Using Automated Liquid Porosimeter
E1441 Guide for Computed Tomography (CT) Imaging
F316 Test Methods for Pore Size Characteristics of Membrane Filters by Bubble Point and Mean Flow Pore Test
F2150 Guide for Characterization andTesting of Biomaterial Scaffolds Used inTissue-Engineered Medical Products Guide for
Characterization and Testing of Biomaterial Scaffolds Used in Tissue-Engineered Medical Products
F2603 Guide for Interpreting Images of Polymeric Tissue Scaffolds
3. Terminology
3.1 Definitions:
3.1.1 bioactive agent, n—anymolecularcomponentin,on,orwithintheintersticesofadevicethatisintendedtoelicitadesired
tissue or cell response.
3.1.1.1 Discussion—Growth factors and antibiotics are typical examples of bioactive agents. Device structural components or
degradation byproducts that evoke limited localized bioactivity are not included. bioactive agents.
3.1.2 blind (end)-pore, n—a pore that is in contact with an exposed internal or external surface through a single orifice smaller
than the pore’s depth.
3.1.3 closed cell, n—a void isolated within a solid, lacking any connectivity with an external surface. Synonym: closed pore
3.1.4 hydrogel, n—a water-based open network of polymer chains that are cross-linked either chemically or through crystalline
junctions or by specific ionic interactions.
3.1.5 macropore/macroporosity (life sciences) , n—a structure inclusive of (including void spaces) sized to allow substantially
unrestricted passage of chemicals, biomolecules, viruses, bacteria, and mammalian cells. In implants with interconnecting pores,
macroporosity provides dimensions that allow for ready tissue penetration and microvascularization after implantation. Includes
materials that contain voids with the potential to be observable to the naked eye (>100 µm).
1
This guide is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and is the direct responsibility of Subcommittee F04.42
on Biomaterials and Biomolecules for TEMPs.
Current edition approved JuneMarch 1, 2009.2010. Published July 2009.April 2010. Originally approved in 2004. Last previous edition approved in 20042009 as
F2450 – 049. DOI: 10.1520/F2450-109.
2
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1
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F2450 – 10
3.1.6
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