Mechanical properties of silk plain‐weft knitted scaffolds for bladder tissue engineering applications

Abstract

Appropriate mechanical properties in both longitudinal and circumferential directions are an important requirement for the scaffold aimed at tissue engineering of the human urinary bladder. In this research, three weft-knitted silk fibroin scaffolds with stitch densities of 138, 182, and 245 loops/cm 2 were fabricated and studied for potential use in bladder regeneration applications. It was shown that the porosity and surface porosity of the scaffolds increased as stitch density decreased. Moreover, increasing the stitch density assisted with decreasing the very big pore size of the weft-knitted scaffolds. The uniaxial mechanical properties of the degummed scaffolds (namely strength and loading-unloading behavior), as well as multiaxial mechanical properties (providing the clinically relevant assessment conditions), were studied. We further studied the effect of cell culturing on the uniaxial mechanical properties of the scaffolds. It was observed that the cell-cultured scaffold represented more strength and strain than the control scaffold after 6 weeks in culture. This study demonstrated that all three studied scaffolds demonstrate low stiffness (high compliance) along with high strength and high strains. Furthermore, comparing the uniaxial properties of weft-knitted scaffolds with those of porcine bladder confirms that all three types of silk fibroin weft-knitted scaffolds resemble bladder. However, the scaffold with a stitch density of 182 loops/cm 2 more closely simulated the porcine bladder, which is believed to be similar to the human bladder. Therefore, this scaffold can be a potential candidate for bladder tissue engineering studies.

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“…Biomechanically, polyglactin mesh was also superior to the other biomaterials in both strain and stress tolerance, and was the closest overall mimic of native porcine tissues. Knitted constructs are known as proper scaffolds for regeneration of load-baring tissues [ 27 , 28 ], and within this field of mechanobiology, it has been shown that stiffness of a biomaterial is known to give cellular state feedback, which can determine the fate of mesenchymal cell differentiation and is required to produce gene expression signatures that mimic the target tissues [ 29 , 30 ]. However, the force exerted on an organ and the required physiological functions can vary over time.…”

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“…Among them, silk is a natural protein fiber, and its superior mechanical properties, biocompatibility, as well as degradability make it very suitable for bladder reconstruction (Bhattacharjee et al, 2017;Nguyen et al, 2019;Li and Sun, 2022). Tavanai and others produced weft-knitted silk fibroin (SF) scaffolds (138, 182, and 245 loops/cm 2 of stitch density respectively), and evaluated their suitability for bladder regeneration (Figure 3) (Khademolqorani et al, 2021). Weft-knitted scaffolds have the following structure characteristics: perpendicular connecting wale and course loops (Eltahan et al, 2016;Cai et al, 2020;Meng et al, 2020).…”

Research progress of biomaterials and innovative technologies in urinary tissue engineering

“…Among them, silk is a natural protein fiber, and its superior mechanical properties, biocompatibility, as well as degradability make it very suitable for bladder reconstruction ( Bhattacharjee et al, 2017 ; Nguyen et al, 2019 ; Li and Sun, 2022 ). Tavanai and others produced weft-knitted silk fibroin (SF) scaffolds (138, 182, and 245 loops/cm 2 of stitch density respectively), and evaluated their suitability for bladder regeneration ( Figure 3 ) ( Khademolqorani et al, 2021 ). Weft-knitted scaffolds have the following structure characteristics: perpendicular connecting wale and course loops ( Eltahan et al, 2016 ; Cai et al, 2020 ; Meng et al, 2020 ).…”