Optical and Structural Properties of Insoluble and Flexible Biodegradable Regenerated Silk Films for Optically Transparent Hydrophilic Coating of Medical Devices

Abstract

materials have been identified as one of the promising materials for use in transparent devices such as optoelectronic devices, photovoltaic cells, and medical devices. [2] Numerous medical devices, such as tubes, catheter, mechanical heart valves, lenses, and disposable plastic slides, require enhanced wettability in order to function properly with physiological fluids and tissues. [3] For the fabrication of medical devices that come into contact with blood and tissue, it is usually desirable to utilize materials with high degree of hydrophilicity. [4] For instance, diagnostic devices, such as glucose meters, typically require a coated film component that allows a blood sample to spread uniformly throughout the film before inserting the tab into a reader. Hydrophilic surface coatings are a wettable, lowfriction biological and mechanical design that makes such medical devices sensitive to fluids by grafting polymers that aid in the binding of water onto the materials. Hydrophilic surface coatings, on the other hand, must fulfill FDA biocompatibility regulations before they may be used on patients. As a result, modified regenerated SF is considered as one of the promising materials for hydrophilic coating application due to its exceptional mechanical characteristics, high biocompatibility, superior biodegradability, and absence of immunogenicity and allergenicity. [5] For in vivo medical devices that employ optically clear surfaces as lenses or windows, the transparent hydrophilic coatings allow ambient microscopic droplets of water to spread over the surface evenly, forming a monolayer of water that is optically clear like the lens material.Remarkably, we established in prior work [2] that SF films produced by solvent casting had outstanding transmission with the UV-shield property and preserved the underlying optical quality of the substrate onto which it could be deposited. When such an SF film is excited at 256 nm, it fluoresces with two wavelength maxima of fluorescence intensity at 320 and 450 nm. Lee et al. [6] verified the luminous nature of silk cocoons due to the presence of flavonoids such as quercetin derivatives and carotenoid molecules. They also reported that comparable to silk cocoons, SF-derivatives such as films, gels, and fibers displayed fluorescence in UV, green, and blue lights, implying potential in biological, electrical, and photonics. Georgakoudi Many medical equipment, such as tubes, lenses, and disposable plastic slides, require improved wettability to perform properly with physiological fluids and tissues. The authors proposes the regeneration of silk cocoons into insoluble and flexible regenerated silk fibroin (SF) films allowed for the development of novel materials with distinct and convincing characteristics. The SF films with glycerol modifications are created using a casting/solvent evaporation technique to provide a flexible and optically transparent hydrophilic coating. Fourier-transformed infrared spectroscopy and wide-angle X-ray diffraction reveal a structural shift in glyce...

Tailoring silk fibroin hydrophilicity and physicochemical properties using sugar alcohols for medical device coatings

“…As of our current knowledge, there is a notable absence of dedicated studies examining the impact of different sugar alcohol plasticizers on the properties of silk fibroin coatings. Previous research has well established that β-sheet crystallites significantly influence the properties of silk fibroin materials 12 Numerous researchers have employed FTIR to investigate the conformation transition kinetics from random coil and/or helix to β-sheet in silk proteins when exposed to various solvents, including methanol, ethanol, propanol, and isopropanol 1 , 12 – 14 In our previous study 15 , it was demonstrated that alcohol treatment reduced the β-sheet content in silk fibroin films. However, in this current study, it is expected that treatment with sugar alcohols will enhance the crystallization of the films, thereby increasing the β-sheet content.…”

“…Hydrophilic coatings are acknowledged for their ability to render medical devices wettable while minimizing surface friction. Amongst these materials, our prior study has demonstrated that modified regenerated silk fibroin (SF) stands out as a promising choice for hydrophilic coating applications 1 . This is attributed to its remarkable characteristics, including high biocompatibility, excellent biodegradability, and its absence of immunogenicity and allergenicity.…”

“…According to Kweon et al 2 , the primary conformation of silk fibroin is characterized by a random α-helix coil, which exhibits instability in water. When subjected to treatment with aqueous methanol 1 , 3 , a transition occurs, leading to a more stable secondary structure identified as the β-sheet. This transition contributes to heightened modulus and tensile strength; nevertheless, this enhanced strength is accompanied by increased brittleness.…”

“…To address this limitation, certain plasticizers, exemplified by glycerol, have been utilized to augment the stretchability and toughness of silk films 1 , 4 . Through this approach, it becomes feasible to regulating the molecular assembly of the silk proteins by incorporating glycerol.…”

“…While the fabrication of silk fibroin/glycerol composites has been previously reported by our group 1 and others 6 , 11 , the incorporation of silk fibroin with various sugar alcohols to alter SF film properties is not widely documented. Therefore, we aim to demonstrate the potential application of SF films as hydrophilic coatings for medical devices to enhance their functionality.…”