Effects of sterilization methods on the physical, chemical, and biological properties of silk fibroin membranes

Abstract

Silk fibroin has been widely explored for many biomedical applications, due to its biocompatibility and biodegradability. Sterilization is a fundamental step in biomaterials processing and it must not jeopardize the functionality of medical devices. The aim of this study was to analyze the influence of different sterilization methods in the physical, chemical, and biological characteristics of dense and porous silk fibroin membranes. Silk fibroin membranes were treated by several procedures: immersion in 70% ethanol solution, ultraviolet radiation, autoclave, ethylene oxide, and gamma radiation, and were analyzed by scanning electron microscopy, Fourier-transformed infrared spectroscopy (FTIR), X-ray diffraction, tensile strength and in vitro cytotoxicity to Chinese hamster ovary cells. The results indicated that the sterilization methods did not cause perceivable morphological changes in the membranes and the membranes were not toxic to cells. The sterilization methods that used organic solvent or an increased humidity and/or temperature (70% ethanol, autoclave, and ethylene oxide) increased the silk II content in the membranes: the dense membranes became more brittle, while the porous membranes showed increased strength at break. Membranes that underwent sterilization by UV and gamma radiation presented properties similar to the nonsterilized membranes, mainly for tensile strength and FTIR results.

On the Routines of Wild-Type Silk Fibroin Processing Toward Silk-Inspired Materials: A Review

“…Methods like immersion in 70% ethanol solution, autoclaving (steam), ethylene oxide (EO), ultraviolet (UV) or γ radiation application, dry heat and antibiotics mix wash were investigated. Studies agree that autoclaving considerably affects mechanical properties of silk, whilst EO has very little influence . Eventual darkening of steam‐sterilized silk was observed .…”

“…Ethanol had adverse mechanical effects on differently formulated materials, but is not considered as appropriate sterilization agent, but rather a disinfection mean . Both UV and γ irradiations retained the original conformational structure of elaborated devices, whereas γ radiation caused silk degradation in a dose‐dependent manner . Similarly to ethanol, UV was considered a way of disinfection .…”

Rapid prototyped sutureless anastomosis device from self‐curing silk bio‐ink

“…This is the basis for the self‐curing RP strategy, which does not require additional deleterious processing to aid curing. The silk material can also be sterilized using several methods without loss of mechanical integrity …”

Sterilization of PMMA microfluidic chips by various techniques and investigation of material characteristics

“…Moreover, it can be completely removed from the material that is processed with SC-CO 2 [11][12][13]. Steam sterilization is the most common technique because of its low cost, effectiveness, easiness to process and not producing toxic compounds [14]. However, steam sterilization operates at 121 • C so heat-sensitive materials will be damaged or destroyed.…”

“…This technique is safe for the human body and harmless to the environment [8]. UV radiation has the DNA as main target for microorganisms elimination [14].…”