ASTM F3274-21

Standard Guide for Testing and Characterization of Alginate Foam Scaffolds Used in Tissue-Engineered Medical Products (TEMPs)

SIGNIFICANCE AND USE
5.1 This guide is a guideline for the characterizing and testing of alginate foam scaffolds used in tissue-engineered medical products. Alginate foam scaffolds can be used in a number of tissue engineering and regenerative medicine applications such as anti-adhesion, internal wound healing, and guided tissue regeneration. In addition, alginate foam can be used as a matrix for cell-based cell therapies and for the release of bioactive agents.
SCOPE
1.1 Consistent functionality of scaffolds used in TEMPs can be made more predictable by monitoring relevant characteristics related to physical and biological properties. This guide may be used in the selection of suitable test methods of dried ionically gelled alginate foam scaffolds that may be a component of a medical device or considered a medical device itself.  
1.2 This guide provides information relevant for the physical testing of alginate foam scaffolds such as mechanical properties, hydration properties, pore structure, and scaffold degradation. In addition, issues related to biological properties such as elemental impurities, bacterial bioburden, bacterial endotoxins, sterility, and biocompatibility are outlined.  
1.3 This guide is intended to be used in conjunction with appropriate characterization and evaluation of any raw or starting materials utilized for fabrication of the alginate foam, such as described in Guides F2027 and F2064.  
1.4 This guide addresses alginate foam scaffolds with and without bioactive agents or biological activity. This guide does not address the characterization or release profiles of any biomolecules, cells, drugs, or bioactive agents that are used in combination with the scaffold.  
1.5 Only SI units are used in this standard.  
1.6 This standard 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 14-May-2021
• ICS: 11.040.30 - Surgical instruments and materials
• Technical Committee: F04 - Medical and Surgical Materials and Devices
• Drafting Committee: F04.42 - Biomaterials and Biomolecules for TEMPs

Relations

• Refers: ASTM F2312-11(2020) - Standard Terminology Relating to Tissue Engineered Medical Products
• Effective Date: 01-Feb-2020
• Refers: ASTM F2150-19 - Standard Guide for Characterization and Testing of Biomaterial Scaffolds Used in Regenerative Medicine and Tissue-Engineered Medical Products
• Effective Date: 01-Oct-2019
• Refers: ASTM F2739-19 - Standard Guide for Quantifying Cell Viability and Related Attributes within Biomaterial Scaffolds
• Effective Date: 01-Sep-2019
• Refers: ASTM F2450-18 - Standard Guide for Assessing Microstructure of Polymeric Scaffolds for Use in Tissue-Engineered Medical Products
• Effective Date: 15-Nov-2018
• Refers: ASTM F2025-06(2018) - Standard Practice for Gravimetric Measurement of Polymeric Components for Wear Assessment
• Effective Date: 01-Apr-2018
• Refers: ASTM F2064-17 - Standard Guide for Characterization and Testing of Alginates as Starting Materials Intended for Use in Biomedical and Tissue Engineered Medical Product Applications
• Effective Date: 01-Mar-2017
• Refers: ASTM F1635-16 - Standard Test Method for <emph type="bdit">in vitro</emph> Degradation Testing of Hydrolytically Degradable Polymer Resins and Fabricated Forms for Surgical Implants
• Effective Date: 01-Dec-2016
• Refers: ASTM F2027-16 - Standard Guide for Characterization and Testing of Raw or Starting Materials for Tissue-Engineered Medical Products
• Effective Date: 01-Oct-2016
• Refers: ASTM F2739-16 - Standard Guide for Quantifying Cell Viability within Biomaterial Scaffolds
• Effective Date: 01-Oct-2016
• Refers: ASTM F748-16 - Standard Practice for Selecting Generic Biological Test Methods for Materials and Devices
• Effective Date: 01-Apr-2016
• Refers: ASTM F2064-14 - Standard Guide for Characterization and Testing of Alginates as Starting Materials Intended for Use in Biomedical and Tissue Engineered Medical Product Applications
• Effective Date: 01-Oct-2014
• Refers: ASTM F2150-13 - Standard Guide for Characterization and Testing of Biomaterial Scaffolds Used in Tissue-Engineered Medical Products
• Effective Date: 01-Oct-2013
• Refers: ASTM F2025-06(2012) - Standard Practice for Gravimetric Measurement of Polymeric Components for Wear Assessment
• Effective Date: 15-Aug-2012
• Refers: ASTM F2312-11 - Standard Terminology Relating to Tissue Engineered Medical Products
• Effective Date: 01-Apr-2011
• Refers: ASTM F1635-11 - Standard Test Method for <i>in vitro</i> Degradation Testing of Hydrolytically Degradable Polymer Resins and Fabricated Forms for Surgical Implants
• Effective Date: 01-Mar-2011

Overview

ASTM F3274-21: Standard Guide for Testing and Characterization of Alginate Foam Scaffolds Used in Tissue-Engineered Medical Products (TEMPs) provides comprehensive guidelines for the selection, characterization, and testing of alginate foam scaffolds. These scaffolds are widely used in tissue engineering and regenerative medicine, serving critical functions such as anti-adhesion, internal wound healing, guided tissue regeneration, and as matrices for cell-based therapies. The guide addresses key methods for assessing both the physical and biological properties of alginate foam scaffolds to ensure consistent performance and suitability within medical products.

Key Topics

• Physical Characterization: The standard outlines methods for evaluating the mechanical properties (tensile and compressive strength), hydration rate, absorption capacity, dimensional stability, pore structure, and degradation characteristics of alginate foam scaffolds.
  • Mechanical properties can be tailored to meet specific surgical requirements.
  • Hydration and absorption are critical for scaffolds intended to retain body fluids or release bioactive agents.
  • Pore size and structure directly influence cell infiltration and tissue integration.
• Biological Assessment: The guide specifies evaluation processes for elemental impurities, bacterial bioburden, endotoxins, sterility, and biocompatibility.
  • Addressing elemental impurities and bacterial contamination is vital for patient safety.
  • Sterilization methods (gamma irradiation, ethylene oxide, aseptic processing) are discussed, along with effects on scaffold properties.
  • Biocompatibility testing aligns with current international standards for medical devices.
• Material and Process Considerations: Quality of raw materials, including alginate source and purity, as well as formulation and processing parameters, impact scaffold performance.
  • Manufacturing choices, such as freeze-drying or mechanical aeration, affect porosity and mechanical strength.
  • Post-processing factors, including sterilization and storage conditions, can influence the final performance of the scaffold.

Applications

Alginate foam scaffolds produced and tested under ASTM F3274-21 are instrumental in advancing tissue-engineered medical products:

• Anti-Adhesion Barriers: Used in surgical sites to prevent unwanted tissue adherence.
• Internal Wound Healing: Serve as temporary frameworks facilitating regenerative processes.
• Guided Tissue Regeneration: Provide structure for cell growth and new tissue formation.
• Drug and Cell Delivery Matrices: Act as vehicles for the controlled release of drugs or support for cell-based therapies.
• Implantable Medical Devices: Integrated either as components or as standalone biocompatible devices for medical and dental applications.

The standard ensures that the physical, mechanical, and biological properties of these scaffolds are controlled and reliable, supporting safer and more effective medical treatments.

Related Standards

ASTM F3274-21 is harmonized with and references several key international and ASTM standards, deepening its applicability for manufacturers and researchers:

• ASTM F2027: Guide for Characterization and Testing of Raw or Starting Materials for Tissue-Engineered Medical Products.
• ASTM F2064: Guide for Characterization and Testing of Alginates as Starting Materials Intended for Use in Biomedical Applications.
• ASTM F2150: Guide for Characterization and Testing of Biomaterial Scaffolds in Regenerative Medicine.
• ASTM F2450: Guide for Assessing Microstructure of Polymeric Scaffolds.
• ASTM F748: Practice for Selecting Biological Test Methods for Materials and Devices.
• ASTM F1635: Test Method for in vitro Degradation Testing of Hydrolytically Degradable Polymers.
• ISO 10993: Biological Evaluation of Medical Devices.
• ISO 11135: Requirements for Sterilization Using Ethylene Oxide.
• AAMI ST72: Bacterial Endotoxins - Test Methods.

By following ASTM F3274-21, manufacturers and researchers can ensure compatibility and regulatory compliance in the field of tissue engineering and medical device development, promoting high-quality, safe, and effective alginate foam scaffolds.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F3274 − 21
Standard Guide for
Testing and Characterization of Alginate Foam Scaffolds
Used in Tissue-Engineered Medical Products (TEMPs)
This standard is issued under the fixed designation F3274; 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 2. Referenced Documents
2.1 ASTM Standards:
1.1 Consistent functionality of scaffolds used inTEMPs can
D638 Test Method for Tensile Properties of Plastics
be made more predictable by monitoring relevant characteris-
D1621 Test Method for Compressive Properties of Rigid
tics related to physical and biological properties. This guide
Cellular Plastics
may be used in the selection of suitable test methods of dried
F748 PracticeforSelectingGenericBiologicalTestMethods
ionically gelled alginate foam scaffolds that may be a compo-
nent of a medical device or considered a medical device itself. for Materials and Devices
F1635 Test Method for in vitro Degradation Testing of
1.2 This guide provides information relevant for the physi-
HydrolyticallyDegradablePolymerResinsandFabricated
cal testing of alginate foam scaffolds such as mechanical
Forms for Surgical Implants
properties, hydration properties, pore structure, and scaffold
F2025 Practice for Gravimetric Measurement of Polymeric
degradation. In addition, issues related to biological properties
Components for Wear Assessment
such as elemental impurities, bacterial bioburden, bacterial
F2027 Guide for Characterization and Testing of Raw or
endotoxins, sterility, and biocompatibility are outlined.
Starting Materials for Tissue-Engineered Medical Prod-
1.3 This guide is intended to be used in conjunction with
ucts
appropriate characterization and evaluation of any raw or
F2064 Guide for Characterization and Testing of Alginates
starting materials utilized for fabrication of the alginate foam,
as Starting Materials Intended for Use in Biomedical and
such as described in Guides F2027 and F2064.
Tissue Engineered Medical Product Applications
F2150 Guide for Characterization and Testing of Biomate-
1.4 This guide addresses alginate foam scaffolds with and
rial Scaffolds Used in Regenerative Medicine and Tissue-
without bioactive agents or biological activity. This guide does
Engineered Medical Products
not address the characterization or release profiles of any
F2312 Terminology Relating to Tissue Engineered Medical
biomolecules, cells, drugs, or bioactive agents that are used in
Products
combination with the scaffold.
F2450 Guide for Assessing Microstructure of Polymeric
1.5 Only SI units are used in this standard.
Scaffolds for Use in Tissue-Engineered Medical Products
1.6 This standard does not purport to address all of the F2739 Guide for Quantifying Cell Viability and Related
safety concerns, if any, associated with its use. It is the Attributes within Biomaterial Scaffolds
responsibility of the user of this standard to establish appro-
2.2 ISO Standards:
priate safety, health, and environmental practices and deter-
ISO 527 Plastics—Determination of tensile properties—Part
mine the applicability of regulatory limitations prior to use.
1: General principles
1.7 This international standard was developed in accor-
ISO 10993 Biological evaluation of medical devices
dance with internationally recognized principles on standard-
ISO 11135 Sterilization of health-care products—Ethylene
ization established in the Decision on Principles for the
oxide—Requirements for the development, validation and
Development of International Standards, Guides and Recom-
routine control of a sterilization process for medical
mendations issued by the World Trade Organization Technical
devices
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This guide is under the jurisdiction of ASTM Committee F04 on Medical and contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Surgical Materials and Devices and is the direct responsibility of Subcommittee Standards volume information, refer to the standard’s Document Summary page on
F04.42 on Biomaterials and Biomolecules for TEMPs. the ASTM website.
Current edition approved May 15, 2021. Published May 2021. DOI: 10.1520/ Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
F3274-21. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3274 − 21
2.3 Other Referenced Document: 6.2.1 Controlled mechanical properties of a foam scaffold
AAMI ST72 Bacterial endotoxins—Test methods, routine are crucial for most applications. The foam must withstand
monitoring, and alternatives to batch testing forces exerted during insertion related to the selected method
without rupture. When using a trochar, the foams typically
3. Terminology
musttoleratehighertensilestressandstraincomparedtofoams
implanted during open surgery.
3.1 Definitions:
3.1.1 foam, n—asolidstructurethatcontainsalargenumber 6.2.2 Tensile Properties—Tensile properties of dry foams
ofinherentorinducedchannelsandopenspaces(thatis,pores; and rehydrated foams can be characterized as specified in Test
see Terminology F2312). Method D638 and ISO 527. The dumbbell-shaped test speci-
mens are recommended to reduce the likelihood of rupture at
4. Summary of Guide
the grips/clamps. Determination of tensile force at break (N),
stress at break (Pa), strain at break (% elongation), and
4.1 Alginate foam scaffolds are being used in the formula-
elasticity (Pa) will be relevant measures for these foams. If the
tion of tissue-engineered medical products. Such scaffolds are
intended use of the implanted foam is to provide mechanical
often intended to be implanted in animals and humans. Factors
support of a tissue or device, the foam must be hydrated before
such as foam integrity, strength, adhesion, biocompatibility,
characterization in a model physiological solution. The me-
pore structure, and degradation will be critical for scaffold
chanical properties of ionically gelled alginate structures are
performance.
influenced by ions in the surrounding solution. To ensure
4.2 Several methods are available to produce alginate foam
relevant measures, it is important that the solution contains the
scaffolds, including porogen leaching, gas-foaming, freeze-
biologically relevant concentration of non-gelling monovalent
drying,andphase-separationtechniques.Forexample,poresin
+ 2+
ions such as sodium ions (Na ), gelling calcium ions (Ca ),
alginate foam may be introduced by the incorporation of air
3–
and calcium-chelating phosphate ions (PO ) of approxi-
into a liquid alginate solution (wet foam) that is subsequently
mately 154 mM, 1.3 mM, and 0.8 mM, respectively. Beware
dried (dry foam), or pores in alginate foam may be introduced
thatsimulatedbodyfluids(SBF),cellculturemedia,phosphate
bytheremovaloficecrystalsfromafrozensolutionofalginate
buffered salt solutions (PBS), and water vary considerably in
through the use of freeze-drying techniques.
composition. During a defined time period the foam shall be
4.3 This guide summarizes physical, mechanical, and bio-
addedtoaknownamountofliquidversusvolumeorweight,or
logical properties that are important for use of alginate foam
alternativelysoakedinexcessamounts.Theselectedstrainrate
scaffolds in TEMPs.
may influence the results when characterizing these viscoelas-
tic materials.Also monitor the temperature of the solution and
5. Significance and Use
environment.
5.1 This guide is a guideline for the characterizing and
6.2.3 Compressive Properties—The bulk elasticity of dry
testing of alginate foam scaffolds used in tissue-engineered
and rehydrated foams can be determined as specified in Test
medical products. Alginate foam scaffolds can be used in a
Method D1621. This may be relevant when aiming to match
number of tissue engineering and regenerative medicine appli-
the compliance of the tissue at the implantation site. This
cations such as anti-adhesion, internal wound healing, and
elasticity will, however, not be comparable with, for example,
guided tissue regeneration. In addition, alginate foam can be
local elasticities sensed by infiltrating cells.
usedasamatrixforcell-basedcelltherapiesandfortherelease
6.2.4 Suture Pull-Out Strength—There are currently no
of bioactive agents.
recognized standard methods for determination of suture pull-
out strength. Development of a method is recommended based
6. Physical Properties
on the specific application related to suture pattern, type, and
6.1 Physical properties of TEMPs in the format of an
depth, and expected forces exerted at the implantation site.
ionically gelled alginate foam can be tuned and optimized to
6.3 Hydration Properties:
meet the requirements for its intended use. The major control-
6.3.1 Different aspects of the hydration properties of alg-
lable characteristics are related to mechanical properties, hy-
inate foams can be considered and are presented below. The
dration properties, pore structure, and degradation and will be
hydration properties depend on the swelling properties of the
presented in this section together with suggestions for test
alginate in the pore wall and capillary bound liquid filling the
methods. The foam can be manufactured to be cut to size or in
pores of the foam. The swelling properties of alginate are
a size appropriate for surgical implantation. The dimensions
dependent on the concentration of ions (as discussed in 6.2.2),
and mechanical properties should allow for easy implantation
in addition to pH, time, and temperature which should be
and positioning and have an appropriate degradation profile.
monitored.
There may be additional relevant characterization procedures
6.3.2 Hydration Rate—The interconnectivity of the pores of
notcoveredbythisguidethatarespecifictothedesignatedend
the foam is the most important characteristic that controls the
use of the foam.
hydration rate of the foam. Fast hydration rates are typically
6.2 Mechanical Properties:
required for foams used when the aim is to absorb and retain
body fluids such as blood during surgery. Slower hydration
rates may, for example, be preferred for foams used as delivery
AAMI ST72 available at https://standards.aami.org/higherlogic/ws/public/
download/12530/AAMI%20CDV1%20ST72%20public%20review%20draft.pdf. vehicles for sustained release of bioactive agents. Different
F3274 − 21
visual methods can be considered for evaluation of this 6.5 Degradation:
property. Examples include placing a foam with a defined area
6.5.1 Altering the chemical makeup of the alginate foam
onto a liquid surface and determining the time needed for the
scaffold through oxidation, amidiation, sulfation, or esterifica-
foam to be fully hydrated, or by placing a known volume of tion will affect degradation once implanted and should be
liquid onto a foam and determining the time for it to be fully
considered when determining the kinetics of scaffold degrada-
absorbed.Amorequantitativemethodwouldbetomeasurethe tion. Many of these modifications facilitate degradation via
weight of a foam in excess liquid at different time points as
hydrolysis. Guide F2150 and Test Method F1635 provide
described in 6.2.2. factorstoconsiderwhenevaluatingthe in vivodegradationrate
6.3.3 Absorption Capacity—A measure of the amount of of alginate foams when modified with these groups. In vivo
liquid that can be retained by the foam.Absorption capacity is degradation of unmodified alginate foams occurs via release of
often expressed as mass uptake of liquid per mass of dry divalent ions into surrounding tissues due to exchange reac-
material, area, volume, or combinations thereof. After the dry tions with monovalent cations that leads to alginate gel
material is weighed, it shall be placed in a relevant model dissolution. The presence of cells during formation of alginate
solution of greater volume than the dry material at a relevant gels may also increase stability via receptor-ligand interac-
temperature and kept therein for a defined time to allow for tions.
absorption.Activ
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