FORMAT
BOOKS
PACKAGES
EDITION
PUBLISHER
CONTENT TYPE
Act
Admin Code
Announcements
Bill
Book
CADD File
CAN
CEU
Charter
Checklist
City Code
Code
Commentary
Comprehensive Plan
Conference Paper
County Code
Course
DHS Documents
Document
Errata
Executive Regulation
Federal Guideline
Firm Content
Guideline
Handbook
Interpretation
Journal
Land Use and Development
Law
Legislative Rule
Local Amendment
Local Code
Local Document
Local Regulation
Local Standards
Manual
Model Code
Model Standard
Notice
Ordinance
Other
Paperback
PASS
Periodicals
PIN
Plan
Policy
Product
Product - Data Sheet
Program
Provisions
Requirements
Revisions
Rules & Regulations
Standards
State Amendment
State Code
State Manual
State Plan
State Standards
Statute
Study Guide
Supplement
Sustainability
Technical Bulletin
All
|
Description of ASTM-F2450 2010ASTM F2450 - 10Standard Guide for Assessing Microstructure of Polymeric Scaffolds for Use in Tissue Engineered Medical ProductsActive Standard ASTM F2450 | Developed by Subcommittee: F04.42 Book of Standards Volume: 13.01 ASTM F2450Significance 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 the length scale that they can measure. Clearly a range of techniques must be utilized if the scaffold is to be characterized in detail. The classification and terminology of pore sizes, such as those given in Table 2, has yet to be standardized, with definitions of terms varying widely (as much as three orders of magnitude) between differing applications and industries. Both Table 2 and the supporting detailed discussion included within Appendix X2 describe differences that exist between IUPAC (International Union of Pure and Applied Chemistry) definitions and the common terminology currently utilized within most life science applications, which include both implant and tissue engineering applications. Since the literature contains many other terms for defining pores (Perret et al (3) ), it is recommended that the terms used by authors to describe pores be defined in order to avoid potential confusion. Additionally, since any of the definitions in Table 2 can shift, dependending on the pore size determination method (see Table 1 and Fig. 1), an accompanying statement describing the utilized assessment technique is essential. All the techniques listed in Table 1 have limitations for assessing complex porous structures. Fig. 2a and Fig. 2b show a through- and a blind-end pore respectively. Porometry measurements (see 7.4) are only sensitive to the narrowest point along a variable diameter through-pore and therefore can give a lower measure of the pore diameter than other investigative techniques, such as scanning electron microscope (SEM), which may sample at a different point along the pore. The physical basis of porometry depends on the passage of gas through the material. Therefore, the technique is not sensitive to blind-end or closed pores. Therefore, estimates of porosity based on porometry data will be different from those obtained from, for example, porosimetry (see 7.3), which is sensitive to both through- and blind-pores or density determinations that can also account for through-, blind-end, and closed pores. The significance of these differences will depend on factors such as the percentage of the different pore types and their dimensions. Further research will enable improved guidance to be developed. Polymer scaffolds range from mechanically rigid structures to soft hydrogels. The methods currently used to manufacture these structures include, but are not limited to: Casting a polymer, dissolved in an organic solvent, over a water-soluble particulate porogen, followed by leaching. Melt mixing of immiscible polymers followed by leaching of the water-soluble component. Dissolution of supercritical carbon dioxide under pressure into an effectively molten polymer, a phenomenon attributed to the dramatic reduction in the glass transition temperature which occurs, followed by a reduction in pressure that leads to the formation of gas bubbles and solidification. Controlled deposition of molten polymer to produce a well-defined three-dimensional lattice. The manufacture of three-dimensional fibrous weaves, knits, or non-woven structures. Chemical or ionic cross-linking of a polymeric matrix. 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 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.
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 and Testing of Biomaterial Scaffolds Used in Tissue-Engineered Medical Products F2603 Guide for Interpreting Images of Polymeric Tissue Scaffolds Keywords microstructure; pore size; pore volume; porosity; porous materials; tissue scaffolds; Polymeric scaffolds; Tissue engineered medical products (TEMPs) ; ICS Code ICS Number Code 11.100 (Laboratory medicine) DOI: 10.1520/F2450-10 ASTM International is a member of CrossRef. ASTM F2450The following editions for this book are also available...This book also exists in the following packages...Subscription InformationMADCAD.com ASTM Standards subscriptions are annual and access is unlimited concurrency based (number of people that can access the subscription at any given time) from single office location. For pricing on multiple office location ASTM Standards Subscriptions, please contact us at info@madcad.com or +1 800.798.9296.
Some features of MADCAD.com ASTM Standards Subscriptions are: - Immediate Access: As soon as the transaction is completed, your ASTM Standards Subscription will be ready for access.
For any further information on MADCAD.com ASTM Standards Subscriptions, please contact us at info@madcad.com or +1 800.798.9296.
About ASTMASTM International, formerly known as the American Society for Testing and Materials (ASTM), is a globally recognized leader in the development and delivery of international voluntary consensus standards. Today, some 12,000 ASTM standards are used around the world to improve product quality, enhance safety, facilitate market access and trade, and build consumer confidence. ASTM’s leadership in international standards development is driven by the contributions of its members: more than 30,000 of the world’s top technical experts and business professionals representing 150 countries. Working in an open and transparent process and using ASTM’s advanced electronic infrastructure, ASTM members deliver the test methods, specifications, guides, and practices that support industries and governments worldwide. |
GROUPS
|