Application Note | ElastoSens™ Bio
PGA Polymers: Properties, Applications & Mechanical Behavior
by Maya Salame and Dimitria Camasao
Application Scientists
What is PGA Polymer?
Poly(glycolic acid) (PGA) is a synthetic aliphatic polyester belonging to the poly(α-hydroxy acid) family. It is produced entirely through industrial chemical synthesis and is characterized by a simple repeating glycolic acid unit linked by ester bonds. PGA is highly crystalline and hydrophilic, features that distinguish it from closely related biodegradable polyesters such as PLA and PLGA. Its degradation product, glycolic acid, is a naturally occurring metabolite that can be processed by normal physiological pathways.
PGA is synthesized from glycolic acid or its cyclic dimer, glycolide. Because of its tendency to degrade and its limited solubility, the production of high–molecular weight PGA is technically demanding and has driven the development of multiple polymerization strategies tailored to achieve sufficient mechanical performance for biomedical use.
Key Properties of PGA Polymers
Physicochemical Characteristics
PGA formation relies on step-growth or ring-opening polymerization mechanisms, with final properties strongly dependent on molecular weight and crystallinity.
Polymerization and synthesis pathways include:
- Ring-opening polymerization of glycolide.
- Direct polycondensation of glycolic acid.
- Azeotropic polycondensation to remove water during synthesis.
- Solid-state polycondensation of halogenoacetates.
- Acid- or enzyme-catalyzed polymerization routes.
PGA exhibits high crystallinity (typically 45–55%), a glass transition temperature close to physiological temperature, and a high melting point. Its dense molecular packing limits solubility in most common organic solvents, influencing both processing and characterization.
Mechanical Properties
PGA is one of the stiffest biodegradable polyesters used in biomedical applications. Its mechanical behavior is dominated by its crystallinity and molecular weight.
- High tensile modulus and tensile strength compared to other resorbable polymers.
- Low elongation at break due to its crystalline structure.
- Mechanical stability increases with molecular weight and crystallinity.
- Rapid loss of mechanical integrity during hydrolytic degradation.
As degradation proceeds, PGA undergoes bulk erosion, leading to a rapid decline in stiffness and strength, often within weeks under physiological conditions.
Biological Interactions
PGA is generally regarded as biocompatible and bioresorbable.
- Degrades primarily by hydrolytic cleavage of ester bonds.
- Can also undergo enzymatic degradation in the presence of esterases.
- Degradation produces glycolic acid, which enters metabolic pathways.
- Rapid degradation may locally decrease pH and trigger inflammatory responses.
Cell adhesion to PGA is typically limited without surface modification, and biological responses are strongly influenced by scaffold architecture, degradation rate, and by-products.
Applications of PGA Polymers
Tissue Engineering
PGA has been extensively used as a temporary scaffold material in tissue engineering due to its high initial mechanical strength and predictable biodegradation. It has been applied in bone, cartilage, tendon, ligament, vascular, and soft-tissue scaffolds, often in fibrous or nonwoven mesh formats. PGA scaffolds are commonly combined with other polymers or coatings to slow degradation and improve cell attachment while maintaining structural integrity during early tissue regeneration.
3D Cell Culture & Disease Models
In three-dimensional culture systems, PGA fiber meshes and porous scaffolds have been used to support cell organization and tissue-like construct formation. Its rapid degradation makes PGA particularly suited for short-term culture models where scaffold replacement by newly synthesized extracellular matrix is desired. PGA-based constructs have been explored for studying tissue development and remodeling under dynamic mechanical environments.
Drug, Gene & Cell Delivery
PGA has been used in controlled delivery systems, most notably as absorbable sutures and temporary carriers for bioactive agents. Drug release from PGA matrices is governed by polymer degradation, crystallinity, and molecular weight distribution. While its rapid hydrolysis limits long-term release applications, PGA remains valuable for short-duration delivery and as a component in composite delivery systems.
Why the Viscoelasticity of PGA Polymers Matters
Although PGA is often perceived as a stiff polymer, its viscoelastic behavior evolves significantly over time due to degradation. Changes in stiffness, damping, and mechanical relaxation directly affect load transfer, scaffold stability, and tissue response. Monitoring viscoelastic properties is essential to understand how PGA-based structures perform during implantation, tissue regeneration, or in vitro culture, particularly as mechanical integrity declines rapidly with hydrolysis.
Methods to Characterize the Viscoelasticity of PGA Polymers
Mechanical characterization of PGA typically relies on destructive or contact-based techniques such as:
- Tensile testing
- Compression testing
- Dynamic mechanical analysis
- Conventional rheometry for molten or processed forms
These methods often require sample destruction, provide limited temporal resolution, and are poorly suited for monitoring degradation or mechanical evolution in hydrated or sterile environments. As a result, they offer only snapshot measurements rather than continuous insight into time-dependent behavior.
ElastoSens™ Bio: A Non-Destructive Tool to Measure Soft PGA Polymers
ElastoSens™ Bio is a resonance-based instrument designed for non-destructive viscoelastic characterization of soft and evolving polymer systems.
- Measures shear modulus in real time without contacting or damaging the sample.
- Highly sensitive and repeatable, suitable for detecting early-stage mechanical changes.
- Enables continuous monitoring of PGA mechanical evolution during degradation.
- Allows repeated measurements on the same sample under hydrated or sterile conditions.
- Compatible with dynamic processes such as polymerization or structural relaxation.
For soft PGA-based systems, ElastoSens™ Bio provides a powerful means to capture the time-dependent loss of stiffness and viscoelastic transitions that govern functional performance in biomedical and research applications.
Conclusions and perspectives
The mechanical performance of PGA—driven by its crystallinity, molecular weight, and rapid degradation—is critical for its function in biomedical and soft polymer systems. When processed into hydrated, porous, or composite structures, PGA exhibits time-dependent viscoelastic evolution that must be monitored without altering the material or environment. Non-destructive viscoelastic characterization with the ElastoSens™ Bio enables:
- High-sensitivity, repeatable measurements tailored to soft and evolving PGA-based systems.
- Real-time tracking of polymer formation or early structural stabilization.
- Identification of transitions from liquid-like to solid-like behavior when applicable.
- Quantification of end stiffness and mechanical decay during degradation.
- Longitudinal testing of the same sample over time, including under sterile conditions.
Together, these capabilities support deeper understanding of PGA structure–property relationships and improved control of its mechanical performance in research and biomedical applications.
References
Budak, K., Sogut, O., & Aydemir Sezer, U. (2020). A review on synthesis and biomedical applications of polyglycolic acid. Journal of polymer research, 27(8), 208.
Low, Y. J., Andriyana, A., Ang, B. C., & Zainal Abidin, N. I. (2020). Bioresorbable and degradable behaviors of PGA: Current state and future prospects. Polymer Engineering & Science, 60(11), 2657-2675.
Cai, M., Han, Y., Zheng, X., Xue, B., Zhang, X., Mahmut, Z., … & Sun, J. (2023). Synthesis of poly-γ-glutamic acid and its application in biomedical materials. Materials, 17(1), 15.
Discover how our technology non-destructively measures the viscoelastic properties of soft biomaterials and tissues using micro-volumes of samples
Related Posts
Extracellular matrix (ECM) hydrogels are biomaterials derived from native tissues after removal of cellular components through decellularization. The remaining matrix preserves key structural proteins (such as collagens, elastin, fibronectin, and laminin), proteoglycans, and glycosaminoglycans that define the biochemical and architectural identity of the source tissue. ECM is naturally produced by cells in all tissues and provides both mechanical support and biochemical signaling cues.
Superabsorbent polymer (SAP) hydrogels are three-dimensional, crosslinked polymer networks capable of absorbing and retaining extremely large amounts of water—often hundreds to thousands of times their own weight—while remaining insoluble. Their structure is based on hydrophilic polymer chains containing functional groups such as carboxylate, hydroxyl, or amide moieties, which generate strong osmotic driving forces for water uptake.
Polyacrylamide (PAM) hydrogels are synthetic, water-swollen polymer networks formed from acrylamide monomers chemically or physically crosslinked into a three-dimensional structure. Polyacrylamide itself is an organic polymer composed of repeating acrylamide subunits, and when crosslinked in aqueous environments, it forms soft, highly hydrated gels with tissue-like mechanical behavior. PAM hydrogels are entirely synthetic and industrially produced, offering high batch-to-batch reproducibility and tunable properties.
Polymethyl methacrylate (PMMA) is a synthetic, thermoplastic polymer belonging to the acrylic resin family. It is formed by the free-radical polymerization of methyl methacrylate (MMA) monomers, resulting in a linear, amorphous polymer with high optical clarity and structural rigidity. PMMA is entirely industrially produced, with MMA synthesized from petrochemical feedstocks and polymerized using controlled thermal, chemical, or photochemical initiation.