Application note | Elastosens™ Bio
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Viscoelasticity of Extracellular Matrices (ECM)
- Hydrogels derived from decellularized extracellular matrices provide the complex and unique natural microenvironment for cell culture in the context of regenerative medicine and tissue engineering.
- The viscoelastic properties of TissueLabs MatriXpec™ hydrogels derived from different porcine organs were successfully measured in real time using the ElastoSens™ Bio.
- The viscoelastic properties of MatriXpec™ products depend on the tissue type that they were derived from.
The field of regenerative medicine comprises different strategies to replace or restore diseased and damaged tissues and organs. It includes tissue-engineered products that rely on the combination of biomaterials, cells and inductive biomolecules to promote tissue and organ regeneration. Natural biomaterials such as collagen, laminin, fibrin and other extracellular matrix (ECM) proteins have been used in regenerative medicine and tissue engineering applications. However, the extracellular microenvironment of the cells is exceptionally more complex, containing hundreds to thousands of unique proteins. The presence and concentration of such proteins are different for each distinct tissue .
Replicating the ECM is essential to mimic the composition and the architecture of native tissues or organs. One way to specifically replicate the cellular microenvironment is to use biomaterials derived from the decellularized extracellular matrix (dECM). Decellularization is defined as the chemical or physical removal of all the cellular components of living tissues, creating an acellular ECM-based scaffold. dECM-based hydrogels preserve the biochemical cues from the original native ECM and the right proportions of ECM proteins [1, 2]. Moreover, these hydrogels provide tissue-specific biomechanical signaling that plays a definitive role in regulation of cellular behaviors, such as adhesion, migration, proliferation and differentiation . Thus, dECM hydrogels are highly specialized biomaterials that can be applied as substrates for 2D or 3D cell culture or can also be combined with biofabrication techniques like 3D bioprinting to generate complex biological constructs .
TissueLabs MatriXpec™ hydrogels are obtained from the decellularization of more than 10 types of porcine organs and tissues and are developed to offer tissue-specific microenvironments for 3D cell culture, containing hundreds of tissue-specific extracellular matrix proteins derived from the native tissue. In this application note, ElastoSens™ Bio was used to assess the viscoelastic properties and gelation kinetics of MatriXpec™ hydrogels obtained from adipose, bone, liver, lung, myocardial, skin, spleen and vascular tissues.
MATERIALS AND METHODS
MatriXpec™ products from porcine bone, skin, myocardium, kidney, vascular, lung, adipose, liver, spleen and muscle were prepared separately in 50 mL tubes. 18 mL of the liquid matrices were gently mixed with 2 mL of buffer by turning the tube upside down for a minute. 6 mL of the solution were poured in each sample holder of the ElastoSens™ Bio and the test was immediately started. The measurements were taken at a temporal step of 20 s and at a temperature of 37 °C. The test duration ranged from 35 minutes to 5 hours depending on the product.
Average results are expressed as mean ± standard deviation. Number of samples was equal to 3 (n = 3). Statistical analyses were performed using GraphPad Prism version 9 (GraphPad Prism software, La Jolla, CA, USA). Comparisons among groups were evaluated by one-way ANOVA with post-hoc Tukey test to correct for multiple comparisons. Significance was retained when p < 0.05.
RESULTS AND DISCUSSION
MatriXpec™ products started to gel as soon as they were neutralized and placed at 37 °C, and therefore G’ was slightly increasing since the beginning of the test, as shown in the example below (Fig. 1). For all the products, the gelation can be seen through the increase in G’ followed by a stabilization. One hour was needed to approach a stable G’ for most products, except MatriXpec™ adipose which took one hour longer.
Figure 1: Shear storage modulus (G’) as a function of time for MatriXpec™ Lung.
The final viscoelastic properties obtained in the stable portion of the curves are represented in Fig. 2 and Table 1 for all products. It is possible to note some statistical differences among them (Table 2) reinforcing the fact that they have different proportions among the many types of proteins.
Figure 2: Final average shear storage modulus (G’) of MatriXpec™ products.
Table 1: Final average shear storage modulus (G’) of MatriXpec™ products.
Table 2: G’ – p-value obtained from one-way ANOVA with post-hoc Tukey test to correct for multiple comparisons. In green, p-values lower than 0.05 are highlighted.
Figure 2: Final average shear storage modulus (G’) of MatriXpec™ products.
The ratio between G’’ and G’ (damping factor or tan(δ)) shows which attribute (viscous or elastic, respectively) is predominant in the mechanical behavior of the material. The final tan(δ) varied from ~0.1 to ~0.4 which also reinforced the different composition of extracellular matrices depending on the tissue of origin. Since the ratio was always below 0.5, the elastic behavior is predominant over the viscous behavior for all products. Bone showed to have the most predominant elastic behavior while liver has the least predominant elastic behavior among them. The balance between the elastic (G’) and viscous (G’’) behaviors of hydrogels can affect cell behavior (migration, differentiation, proliferation) when in culture. In the native tissue, this balance determines their proper function in response to physiological stimuli.
The viscoelastic properties of MatriXpec™ products from TissueLabs were successfully measured in real time using ElastoSens™ Bio. Final G’ and tan(δ) varied according to the tissue type reflected by the different proportion of their many proteins. The viscoelastic properties are therefore unique to each tissue type and it is strictly related to its function.
- MatriXpec™ products provide the natural components, in their natural proportions, of 10 types of tissues for developing tissue engineered products.
- ElastoSens™ Bio is able to detect slight differences in the viscoelastic properties of decellularized extracellular matrices hydrogels.
- Determining the gelation kinetics of hydrogels is valuable to better design experiments.
- Determining the soft nature of decellularized extracellular matrices helps researchers to better understand native tissues and the needs of each cell type and application.
 Dzobo, K., Motaung, K. S. C. M., & Adesida, A. (2019). Recent Trends in Decellularized Extracellular Matrix Bioinks for 3D Printing: An Updated Review. International Journal of Molecular Sciences, 20(18). https://doi.org/10.3390/ijms20184628
 Liao, J., Xu, B., Zhang, R., Fan, Y., Xie, H., & Li, X. (2020). Applications of decellularized materials in tissue engineering: advantages, drawbacks and current improvements, and future perspectives. Journal of Materials Chemistry. B, Materials for Biology and Medicine, 8(44), 10023–10049.
 Kim, B. S., Das, S., Jang, J., & Cho, D.-W. (2020). Decellularized Extracellular Matrix-based Bioinks for Engineering Tissue- and Organ-specific Microenvironments. Chemical Reviews, 120(19), 10608–10661.
 Sakina, R., Llucià-Valldeperas, A., Henriques Lourenço, A., Harichandan, A., Gelsomino, S., Wieringa, P., Mota, C., & Moroni, L. (2020). Decellularization of porcine heart tissue to obtain extracellular matrix based hydrogels. Methods in Cell Biology, 157, 3–21.
Alginate is a polysaccharide present as a structural component of algae and a capsular component of soil bacteria. The polysaccharide is typically obtained from brown seaweed and used in many industries such as medical, pharmaceutical, food, textile due to its viscosifying, gelling and stabilizing properties.
Dr. Daniel J. Kelly and his team at Trinity College Dublin researched how changing the formulation of an alginate bioink can alter the mechanical properties of a 3D printed scaffold. Like preparing a sauce, the consistency of a bioink can be adjusted by changing the concentration of its ingredients. However, it's more complex in biomedical research and requires analytical tools for quantification. Alginate, a natural biomaterial from algae, can quickly crosslink in the presence of ions (like Ca2+), forming a cohesive hydrogel with tunable properties. This makes it an ideal bioink for 3D bioprinting in tissue engineering and drug delivery.
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During this last month, we explored the use of decellularized extracellular matrices (dECM) in tissue engineering and cell culture. dECM provides a natural scaffold for cells, containing the necessary biochemical cues and structural support to mimic native tissues. In one study, researchers from Trinity College Dublin investigated how the formulation of an alginate bioink can modulate the mechanical properties of 3D printed scaffolds. Alginate, a natural biomaterial derived from algae, is commonly used as a bioink due to its viscosifying, gelling, and biocompatible properties. The researchers examined different formulations of the bioink, varying the degree of polymerization and the type of divalent cations used for crosslinking. They evaluated the mechanical properties of the resulting scaffolds and assessed their suitability for tissue engineering applications. This work highlights the importance of optimizing bioink formulations to achieve desired mechanical properties in 3D printed constructs.
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 a recent study, researchers from the University of California at Davis investigated the impact of the viscoelasticity of the cell's environment on bone formation by mesenchymal stromal cells (MSCs). They prepared alginate hydrogels with different mechanical properties and loaded them with MSC aggregates. The results showed that while both hydrogels supported high cell viability, the viscoelastic hydrogel promoted significantly higher calcium production by the cells compared to the elastic hydrogel. Calcium is an essential component for bone regeneration. These findings emphasize the importance of the cell's external environment, specifically its viscoelastic properties, in influencing cellular behavior and tissue regeneration.