ASTM F2450-09
(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 roughness, 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 enable a systematic investigation to be made 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 tissu...
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.
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Designation:F2450–09
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 E1294 Test Method for Pore Size Characteristics of Mem-
3
brane Filters Using Automated Liquid Porosimeter
1.1 This guide covers an overview of test methods that may
F316 Test Methods for Pore Size Characteristics of Mem-
be used to obtain information relating to the dimensions of
brane Filters by Bubble Point and Mean Flow Pore Test
pores, the pore size distribution, the degree of porosity,
F2150 Guide for Characterization and Testing of Biomate-
interconnectivity, and measures of permeability for porous
rial Scaffolds Used inTissue-Engineered Medical Products
materials used as polymeric scaffolds in the development and
manufacture of tissue engineered medical products (TEMPs).
3. Terminology
This information is key to optimizing the structure for a
3.1 Definitions:
particular application, developing robust manufacturing routes,
3.1.1 bioactive agent, n—any molecular component in, on,
and for providing reliable quality control data.
or within the interstices of a device that is intended to elicit a
1.2 The values stated in SI units are to be regarded as
desired tissue or cell response.
standard. No other units of measurement are included in this
3.1.1.1 Discussion—Growthfactorsandantibioticsaretypi-
standard.
cal examples of bioactive agents. Device structural compo-
1.3 This guide does not purport to address all of the safety
nents or degradation byproducts that evoke limited localized
concerns, if any, associated with its use. It is the responsibility
bioactivity are not included.
of the user of this standard to establish appropriate safety and
3.1.2 blind (end)-pore, n—a pore that is in contact with an
health practices and to determine the applicability of regula-
exposed internal or external surface through a single orifice
tory limitations prior to use.
smaller than the pore’s depth.
2. Referenced Documents 3.1.3 closed cell, n—a void isolated within a solid, lacking
2
any connectivity with an external surface. Synonym: closed
2.1 ASTM Standards:
pore
D2873 Test Method for Interior Porosity of Poly(Vinyl
3.1.4 hydrogel, n—a water-based open network of polymer
Chloride) (PVC) Resins by Mercury Intrusion Porosim-
3 chains that are cross-linked either chemically or through
etry
crystalline junctions or by specific ionic interactions.
D4404 Test Method for Determination of Pore Volume and
3.1.5 macropore/macroporosity (life sciences), n—a struc-
Pore Volume Distribution of Soil and Rock by Mercury
ture inclusive of void spaces sized to allow substantially
Intrusion Porosimetry
unrestricted passage of chemicals, biomolecules, viruses, bac-
E128 Test Method for Maximum Pore Diameter and Per-
teria, and mammalian cells. In implants with interconnecting
meability of Rigid Porous Filters for Laboratory Use
pores, provides dimensions that allow for ready tissue penetra-
tion and microvascularization after implantation. Includes
materials that contain voids with potential to be observable to
1
This guide is under the jurisdiction of ASTM Committee F04 on Medical and
the naked eye (>100 µm).
Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.42 on Biomaterials and Biomolecules for TEMPs. 3.1.6 micropore/microporosity (life sciences), n—a struc-
CurrenteditionapprovedJune1,2009.PublishedJuly2009.Originallyapproved
ture inclusive of void spaces sized to allow substantially
in 2004. Last previous edition approved in 2004 as F2450 – 04. DOI: 10.1520/
unrestricted passage of chemicals, biomolecules, and viruses
F2450-09.
2
while sized to control or moderate the passage of bacteria,
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
mammalian cells, and/or tissue. Includes materials with typical
Standards volume information, refer to the standard’s Document Summary page on
pore sizes of greater than 0.1 µm (100 nm) and less than about
the ASTM website.
3
100 µm (100 000 nm), with a common microporous context
Withdrawn. The last approved version of this historical standard is referenced
on www.astm.org. encompassing the range of 20 µm or less for the filtration of
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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F2
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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:F2450–04 Designation:F2450–09
Standard Guide for
Assessing Microstructure of Polymeric Scaffolds for Use in
1
Tissue Engineered Medical Products
This standard is issued under the fixed designation F 2450; 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
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:
D 2873 Test Method for Interior Porosity of Poly(Vinyl Chloride) (PVC) Resins by Mercury Intrusion Porosimetry
D 4404 Test Method for Determination of Pore Volume and Pore Volume Distribution of Soil and Rock by Mercury Intrusion
Porosimetry
E 128 Test Method for Maximum Pore Diameter and Permeability of Rigid Porous Filters for Laboratory Use
E 1294 Test Method for Pore Size Characteristics of Membrane Filters Using Automated Liquid Porosimeter
F 316 Test Methods for Pore Size Characteristics of Membrane Filters by Bubble Point and Mean Flow Pore Test
F 2150 Guide for Characterization and Testing of Biomaterial Scaffolds Used in Tissue-Engineered Medical Products
2.2 ISO Standard:
ISO 845Cellular Plastics and Rubbers—Determination of Apparent (Bulk) Density
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.
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 void spaces sized to allow substantially unrestricted
passage of chemicals, biomolecules, viruses, bacteria, and mammalian cells. In implants with interconnecting pores, provides
dimensions that allow for ready tissue penetration and microvascularization after implantation. Includes materials that contain
voids with 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 Nov. 1, 2004. Published December 2004.
Current edition approved June 1, 2009. Published July 2009. Originally approved in 2004. Last previous edition approved in 2004 as F 2450 – 04.
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
---------------------- Page: 1 ----------------------
F2450–09
3.1.6 micropore/microporosity (life sciences) , n—a structure inclusive of void spaces sized to allow substantially unrestricted
passage of chemicals, biomol
...
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