Application Note | ElastoSens™ Bio
Hyaluronic Acid Hydrogels: Properties, Applications & Mechanical Behavior
by Maya Salame and Dimitria Camasao
Application Scientists
What is a Hyaluronic Acid Hydrogel?
Hyaluronic acid (HA) is a naturally occurring, linear polysaccharide belonging to the family of non-sulfated glycosaminoglycans. It is composed of repeating disaccharide units of D-glucuronic acid and N-acetyl-D-glucosamine linked through alternating β-1,3 and β-1,4 glycosidic bonds. HA is a major component of the extracellular matrix in vertebrate tissues, where it contributes to hydration, space filling, and viscoelasticity.
Hyaluronic acid is found in high concentrations in connective tissues such as skin, synovial fluid, vitreous humor, and cartilage. Industrially, it is produced either by extraction from animal tissues or, more commonly, by microbial fermentation using non-pathogenic bacterial strains. Native HA is water-soluble and does not form stable hydrogels on its own; hydrogel formation therefore requires physical associations or chemical modification to generate a three-dimensional network.
Key Properties of Hyaluronic Acid Hydrogels
Physicochemical Characteristics
Hyaluronic acid hydrogels are formed by introducing intermolecular interactions that transform soluble HA chains into a crosslinked network capable of retaining large amounts of water. Gelation mechanisms vary depending on the modification strategy.
Common gelation and crosslinking approaches include:
- Covalent crosslinking through hydroxyl or carboxyl functional groups.
- Photo-crosslinking of methacrylated HA derivatives.
- Enzymatic crosslinking under mild physiological conditions.
- Physical associations based on hydrogen bonding or ionic interactions.
The physicochemical behavior of HA hydrogels is strongly influenced by molecular weight, degree of modification, crosslink density, and environmental parameters such as pH and ionic strength. These factors govern swelling behavior, permeability, and network stability.
Mechanical Properties
Hyaluronic acid hydrogels exhibit soft, viscoelastic mechanical behavior that closely resembles native extracellular matrices. Their stiffness can be precisely tuned across several orders of magnitude by adjusting HA concentration, molecular weight, and crosslinking chemistry.
Key mechanical features include:
- Low elastic moduli compatible with soft tissues.
- Strong dependence of stiffness on crosslink density and network architecture.
- Time-dependent mechanical relaxation and stress dissipation.
As HA hydrogels degrade through hydrolysis or enzymatic activity, their mechanical properties evolve dynamically, making longitudinal monitoring essential for understanding structure–function relationships.
Biological Interactions
Hyaluronic acid plays an active biological role through interactions with cell surface receptors such as CD44 and RHAMM. These interactions regulate cell migration, proliferation, inflammation, and tissue remodeling.
Notable biological characteristics include:
- Excellent biocompatibility and low immunogenicity.
- Size-dependent biological signaling effects.
- Enzymatic degradation by hyaluronidases.
Because HA is a native component of the extracellular matrix, its hydrogels are widely used to create biologically relevant microenvironments.
Applications of Hyaluronic Acid Hydrogels
Tissue Engineering
Hyaluronic acid hydrogels are extensively used in tissue engineering to mimic native extracellular matrices and support tissue regeneration. Their tunable mechanics and bioactivity make them suitable for skin, cartilage, neural, and vascular tissue constructs.
3D Cell Culture & Disease Models
In 3D cell culture, HA hydrogels provide physiologically relevant environments that regulate cell behavior through both mechanical and biochemical cues. They are widely employed in cancer models, fibrosis studies, and stem cell research to investigate matrix-driven cell responses.
Drug, Gene & Cell Delivery
Hyaluronic acid hydrogels serve as versatile platforms for localized delivery of therapeutic agents and cells. Their degradability and receptor-mediated interactions enable controlled release, targeted delivery, and enhanced therapeutic efficacy.
Why the Viscoelasticity of Hyaluronic Acid Hydrogels Matters
The viscoelastic properties of hyaluronic acid hydrogels are central to their biological and functional performance. Viscoelasticity governs how cells perceive mechanical cues, migrate through the matrix, and remodel their surroundings. In dynamic biological environments, the ability of HA hydrogels to dissipate stress and evolve mechanically over time is critical for accurately replicating native tissue behavior and achieving predictable outcomes in regenerative and disease-modeling applications.
Methods to Characterize the Viscoelasticity of Hyaluronic Acid Hydrogels
Hyaluronic acid hydrogel mechanics are commonly evaluated using rheometry, compression testing, and indentation-based methods. While these approaches provide valuable bulk measurements, they often require destructive sample handling, large deformations, or endpoint testing. Traditional techniques may also struggle to capture gelation kinetics, subtle mechanical transitions, or long-term mechanical evolution under sterile conditions.
Case study: Mechanical Characterization of Hyaluronic Acid Hydrogel Using ElastoSens™ Bio
ElastoSens™ Bio: A Non-Destructive Tool to Measure Soft Hyaluronic Acid Hydrogels
The ElastoSens™ Bio non-destructive mechanical characterization platform specifically designed for soft, hydrated biomaterials such as hyaluronic acid hydrogels. The instrument applies low-amplitude oscillatory excitation and measures the resonance response of the sample to extract viscoelastic properties with high sensitivity.
Its contactless measurement approach preserves network integrity, making it particularly well suited for fragile HA hydrogels. Key advantages include real-time monitoring of gelation kinetics, precise identification of the liquid–gel transition point, accurate determination of final stiffness, and exceptional repeatability. Because the same sample can be measured repeatedly, the ElastoSens™ Bio enables longitudinal mechanical studies under controlled and sterile conditions when required.
To demonstrate the capabilities of the ElastoSens™ Bio, a series of measurements were performed on hyaluronic acid–based hydrogels. The following section describes the materials and methods employed, followed by the results, providing a practical example of the instrument’s ability to non-destructively monitor viscoelastic properties over time.
Material and methods
Methacrylated hyaluronic acid (PhotoHA®, Advanced BioMatrix, #5274) was prepared according to the manufacturer’s instructions. Lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) was dissolved in PBS to obtain a 17 mg/mL stock solution, which was used to reconstitute PhotoHA® vials. PhotoHA® was prepared at final concentrations of 1% and 2% (w/v) and stored at 4 °C until fully dissolved.
For each measurement, 3 mL of PhotoHA® solution was loaded into the ElastoSens™ Bio macro sample holder and the test was initiated immediately. Samples were equilibrated at 20 °C for 10 min (no light). Photocrosslinking was then performed under 405 nm light at an intensity of 8 mW/cm² for 20 min, while viscoelastic measurements were recorded every 5 s throughout the run.
Results and discussion
Increasing PhotoHA® concentration from 1% to 2% (w/v) resulted in a significant increase in final shear storage modulus (G′), rising from 3307 ± 134 Pa to 12 227 ± 350 Pa (***p < 0.001). In parallel, the maximum gelation speed was significantly higher for 2% PhotoHA® compared to 1% (30.9 ± 3.6 Pa/s vs. 15.2 ± 3.0 Pa/s, **p < 0.01), indicating faster network development under identical photocuring conditions. The initiation time showed a small decrease with increasing concentration (12.32 ± 0.04 min at 1% vs. 11.45 ± 0.09 min at 2%), but this difference was not significant (ns, p > 0.05).
The increase in G′ at higher PhotoHA® concentration is consistent with greater polymer content and availability of methacrylate groups, leading to higher crosslink density and a stiffer hydrogel network. The higher gelation speed at 2% further supports more rapid network formation once polymerization proceeds, whereas the similar initiation times suggest that the onset of gelation is not strongly shifted across this concentration range under the same light and photoinitiator conditions. Overall, these results show that PhotoHA® concentration provides effective control over both the final mechanical properties and gelation kinetics of photocrosslinked hyaluronic acid hydrogels.
Figure 1. Final shear storage modulus (G′, left), initiation time (middle, min), and maximum gelation speed (right; Pa/s) comparing 1% and 2% (w/v) PhotoHA® with 405 nm curing. Mean ± SD (n = 3). ns p > 0.05, **p < 0.01, ***p < 0.001.
Conclusions and perspectives
The mechanical behavior of hyaluronic acid hydrogels—governed by their viscoelasticity, crosslinking strategy, and time-dependent evolution—is critical to their biological performance and functionality in engineered systems. Because HA hydrogels are soft, highly hydrated, and often dynamically remodeled or degradable, their mechanics must be characterized without altering network integrity or experimental conditions.
Non-destructive viscoelastic characterization with the ElastoSens™ Bio enables:
- High-sensitivity and repeatable measurements tailored to soft materials.
- Real-time monitoring of gelation kinetics and identification of the liquid–gel transition point.
- Accurate determination of final hydrogel stiffness.
- Longitudinal testing of the same sample over time, under sterile conditions if required.
This approach supports deeper insight into HA structure–property relationships, improved reproducibility, and more robust translation of hyaluronic acid hydrogel systems across research and biomedical applications.
References
Di Mola, A., Landi, M. R., Massa, A., D’Amora, U., & Guarino, V. (2022). Hyaluronic acid in biomedical fields: new trends from chemistry to biomaterial applications. International journal of molecular sciences, 23(22), 14372.
Sekar, M. P., Suresh, S., Zennifer, A., Sethuraman, S., & Sundaramurthi, D. (2023). Hyaluronic acid as bioink and hydrogel scaffolds for tissue engineering applications. ACS Biomaterials Science & Engineering, 9(6), 3134-3159.
Hussain, Z., Thu, H. E., Katas, H., & Bukhari, S. N. A. (2017). Hyaluronic acid-based biomaterials: a versatile and smart approach to tissue regeneration and treating traumatic, surgical, and chronic wounds. Polymer Reviews, 57(4), 594-630.
Abatangelo, G., Vindigni, V., Avruscio, G., Pandis, L., & Brun, P. (2020). Hyaluronic acid: redefining its role. Cells, 9(7), 1743.
Burdick, J. A., & Prestwich, G. D. (2011). Hyaluronic acid hydrogels for biomedical applications. Advanced materials, 23(12), H41-H56.
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