Preparation and Statistical Characterization of Tunable Porous Sponge Scaffolds using UV Cross-linking of Methacrylate-Modified Silk Fibroin

Abstract

Silk fibroin sponges have been widely studied and reported in literature for tissue engineering applications. Several fabrication methods have been proposed during the years to cover most of the demands in terms of properties, which should be adapted to the considered tissue. Most of these procedures are based on the secondary structure transition of the protein to the stable β crystalline form. This transition, known as physical cross-linking, makes the sponge resistant to dissolution in water, and, in general, increases the sponge stiffness. In our work, we propose an alternative method to ensure the stability of the sponge based on chemical crosslinking of a methacrylated version of silk fibroin (Sil-MA) obtained via chemical modification. The Sil-MA water solution with the addition of a photoinitiator (LAP) allows the opening, under UV radiation, of a double carbon−carbon bond and radical polymerization. The incorporation of air bubbles (that serves as a template for the pores) was accomplished by a mixer; then, the foam was stabilized under UV light and the excess water was removed by freeze-drying. Because of the cytotoxicity of the photoinitiator (found when used at a high concentration), an additional washing step in water has been introduced to eliminate the residues and improve the cells' viability. Fourier transform infrared (FTIR) analysis confirmed the functionalization of the protein. To evaluate the effect of the composition on the sponge properties, a 2 3 full factorial design of the experiment has been adopted. FTIR analysis revealed that the sponge composition did not affect the protein's secondary structure. The analysis of images obtained by SEM allowed some statistical measures of the porosity curves to be studied and modeled. The same modeling procedure was applied to the dissolution test in a simulated body fluid, to the water absorption, and to the cell viability (tested by the MTT and LDH assays). An empirical model for each property was built, showing how by changing the composition it is possible to tune the sponge properties.

Preparation and characterization of a soluble eggshell membrane/agarose composite scaffold with possible applications in cartilage regeneration

“…To avoid the modification of the morphology the hydrogels were rapidly frozen using liquid nitrogen to reduce the ice crystal dimension and not compromise the structure formed by the gels, then a freeze‐drying procedure was conducted for 2 days at 35°C. The pore size was then evaluated by image analysis conducted using the ImageJ (Schneider et al., 2012) following a previous developed methodology (Bucciarelli, Adami et al., 2020; Bucciarelli, Muthukumar et al., 2019; Bucciarelli, Reddy Chandraiahgari et al., 2020) and shown in Figure 1. Briefly, three images for each scaffold were collected by SEM, a color threshold was then applied to isolate the pores from the scaffold walls, subsequently the pores perimeter and the inner area were calculated.…”

“…They must also have adequate mechanical properties, decompose in response to the formation of new tissues, promote the spread of nutrients and metabolites, adhere and integrate with surrounding native tissues, and be able to adequately fill damaged areas (Freyman et al., 2001; M. Liu et al., 2017). Several natural matrices have been adopted in tissue engineering (silk fibroin, keratin, collagen, alginate and several polysaccharides) among them collagen is a versatile material that can be used to produce hydrogels, membranes, and porous scaffolds (Bucciarelli, Chiera et al., 2019; Bucciarelli et al., 2018, 2017; Bucciarelli, Muthukumar et al., 2019; Yang et al., 2019). Collagen has been successfully used in a wide range of tissue engineering applications as a base material for scaffolding and has been proved to be biocompatible, biodegradable, permeable, and with a low immunogenicity, it can also be formed in a way to tune the construct porosity (Dong & Lv, 2016).…”

Photo-Crosslinked Silk Fibroin for 3D Printing

“…The degree of methacryloyl substitution is associated with the concentration of GMA; 424 mM showed the highest degree of crosslinking density at 42%. GMA is proposed to react with the primary amines of lysine residues, around 0.2% of all amino acids of silk fibroin, and was confirmed by proton nuclear magnetic resonance ( 1 H NMR) [ 49 , 103 ] ( Figure 5 a). However, GMA is reported to react with other groups, such as hydroxyl and carboxyl, via both the transesterification and the epoxide ring-opening mechanisms [ 102 , 104 ] ( Figure 5 b).…”

Optimization of a Low-Power Chemoresistive Gas Sensor: Predictive Thermal Modelling and Mechanical Failure Analysis

“…A statistical method was used to cross-correlate the results obtained from the thermal predictive model and the mechanical failure analysis and to define a comprehensive model for tuning future sensor layouts to the required performance. The entire statistical analysis was done using the programming language R [ 57 ] following the statistical strategy described in previous works [ 58 , 59 , 60 , 61 ]. An initial comparison by verifying the presence of a significant difference among the various groups was performed by using the analysis of variance (ANOVA) and was followed by a Tukey multi-comparison test.…”