Multiscale analysis of mechanical and structural properties of agarose-silk fibroin hydrogels

This study provides a comprehensive characterization of the agarose-silk fibroin hydrogels, using atomic force microscopy and scanning transmission electron microscopy to analyse their structure and assess the effect of composition on mechanical properties via nanoindentation and rheological analysis. These measurements enabled determination of mechanical properties, including the elastic and viscoelastic moduli at both the micro- and macroscale. The hydrogels exhibited a wide range of moduli depending on different degrees of network crosslinking, influenced by varying concentrations of agarose (1 or 2 wt%) and the percentage of fibroin fibres (0-4.5 wt%) as an interpenetrating component. The viscoelastic modulus (G') and the elastic modulus determined using a relaxation model (E), were 5-57 kPa and 1.2-110 kPa, respectively. The adhesion energy of these hydrogels was determined from nanoindentation curves and analysed using the JKR model, with values ranging from 0.031 to 0.066 J m^-2. These results provide insight into how the hydrogels' microstructure influences their mechanical and transport properties. Incorporating fibroin into these gels modifies biological and biochemical characteristics of the gels, suggesting that such composite hydrogels could be further explored for potential applications in controlled release systems, extracellular matrix models, or tissue engineering scaffolds.