Mechanical analysis of UV crosslinked hydrogels using ElastoSens™ Bio
- The evaluation of the mechanical properties of UV-crosslinked hydrogels is conventionally performed with destructive techniques.
- ElastoSens™ Bio allowed multiple tests on the same UV-crosslinked hydrogels under progressive exposure to UV light and controlled temperature.
- Longer exposure time to UV light increased the stiffness of methacrylated hyaluronic acid and gelatin but no influence was observed for methacrylated collagen.
Hydrogels have been widely used in biomedical research for developing engineered tissues and novel treatments such as wound dressings and drug delivery systems. Photo-crosslinkable polymers are an interesting option in the field due to the possibility of tuning its microstructure by regulating the wavelength, intensity and duration of the applied light [1, 2, 3]. The modulation of the hydrogel microstructure is important for tailoring the mechanical properties of 3D matrices or for the release of drugs from hydrogels. The evaluation of the hydrogel mechanical properties during or after exposure to UV light is usually performed with destructive testing techniques such as rheometry and compression testing. However, this prevents the re-use of the gel for further characterization. Furthermore, destructive techniques require multiple samples to test the mechanical stability of UV crosslinked gels over long periods of time. In this short application note, the ElastoSens™ Bio was used to measure the viscoelastic properties of different hydrogels from Advanced BioMatrix (CA, USA), a leading provider of biologically derived hydrogels, after different exposure times to UV light.
MATERIALS AND METHODS
Methacrylated collagen 0.6 % (PhotoCol®, 6 mg/mL), methacrylated hyaluronic acid 1 (PhotoHA®, 1 mg/mL) and methacrylated gelatin (PhotoGel®, 100 mg/mL) were pipetted in the ElastoSens™ Bio sample holders with the photoinitiator Irgacure 2959 and transferred to an UV (365 nm) chamber for irradiation for 5 or 10 minutes at 37 °C or room temperature. The same PhotoCol® samples were tested on the ElastoSens™ Bio before and right after exposure to UV light.
RESULTS AND DISCUSSION
Fig. 2: Shear storage modulus (G’) of PhotoHA® – UV methacrylated hyaluronic acid and PhotoGel® – UV methacrylated gelatin after exposure to UV light for 5 or 10 minutes at room temperature
- ElastoSens™ Bio is an easy-to-use, non-destructive and contact free instrument that measures the viscoelasticity of hydrogels.
- Testing the same sample over short or long periods of time is now possible due to the non destructive nature of the technology.
- ElastoSens™ Bio allows testing the viscoelasticity of biomaterials under different physical (e.g. photo or thermo stimulation), chemical (e.g. crosslinking solution) and physiological (e.g. enzymatic solution) conditions to simulate in vivo behaviors.
- ElastoSens™ Bio can be used for R&D, quality control of production and pre-clinical studies. Combined with Soft Matter Analytics™ capabilities, it offers a unique testing platform.
 Choi, J. R., Yong, K. W., Choi, J. Y., & Cowie, A. C. (2019). Recent advances in photo-crosslinkable hydrogels for biomedical applications. BioTechniques, 66(1), 40-53.
 Nichol, J. W., Koshy, S. T., Bae, H., Hwang, C. M., Yamanlar, S., & Khademhosseini, A. (2010). Cell-laden microengineered gelatin methacrylate hydrogels. Biomaterials, 31(21), 5536-5544.
 Eke, G., Mangir, N., Hasirci, N., MacNeil, S., & Hasirci, V. (2017). Development of a UV crosslinked biodegradable hydrogel containing adipose derived stem cells to promote vascularization for skin wounds and tissue engineering. Biomaterials, 129, 188-198.
All cells in the human body are exposed to mechanical forces which regulate cell function and tissue development, and each cell type is specifically adapted to the mechanical properties of the tissue it resides in. The matrix properties of human tissues can also change with disease and in turn facilitate its progression.
In September, we explored the applications of photostimulation in hydrogels. Light-induced reactions are commonly used in various fields, including dentistry, coatings, and beauty salons. In biomedical research, natural components like collagen and hyaluronic acid have been modified to react to light exposure. These modifications, along with the use of photoinitiators, allow for better control over the processability and viscoelastic properties of hydrogels. This control is essential for applications such as in vivo injection, 3D bioprinting, and matching the mechanical behavior of implantation sites.
Gelatin and hyaluronic acid (HA) are biomaterials widely used in the biomedical research field. HA is the most abundant glycosaminoglycan in the body and is an important component of several tissues. HA contributes to tissue hydrodynamics, movement and proliferation of cells, and participates in a number of cell surface receptor interactions.
In the context of dental treatments and other applications like surface coatings and 3D printing, the use of light to transform deformable resins into rigid materials is well-known. Similarly, in biomedical applications, photostimulation is used to modify the mechanical properties of hydrogels. Natural hydrogels have been chemically modified to allow precise control over their viscoelastic properties through light exposure. These photosensitive hydrogels can transition from a liquid to a gel state with varying levels of firmness based on formulation, light intensity, and exposure time. Matching the viscoelasticity of the hydrogel to the target organ is crucial in tissue engineering and regenerative medicine.