Fabrication of Nanoscale Patternable Films of Silk Fibroin Using Benign Solvents

Abstract

The silk protein fibroin is a wondrous biopolymer widely used to form structures that interface with biological entities. In addition to tissue scaffolds, sponges, and films, biochemically modified fibroins can be used in conjunction with techniques such as photolithography and soft lithography to expand their repertoire for micro‐ and nanofabricated systems. To date, the use of hexafluoro‐2‐isopropanol (HFIP) has been prevalent as a solvent for fibroin and fibroin “resists.” However, high volatility, toxicity, cost, and need for specialized disposal render the necessity for alternative solvents. Additionally, for applications such as in optics and bioelectronics, smooth, thin (≈100 nm and below) fibroin films are a prerequisite, which are not easily achieved using HFIP. Here, the use of formic acid (FA) as a sustainable solvent is presented for silk fibroin and fibroin “resist” materials, specifically for micro‐ and nanoscale applications. The reproducible formation and characterization of stable thin films of high homogeneity, smoothness, and optical transparency are demonstrated. Critically, these films can be used for high‐resolution photopatterning of proteins using benchtop lithographic techniques. The study indicates that FA is a relatively benign and optimal solvent for forming smooth, thin films, and microscale architectures for the fabrication of next generation silk‐based optical devices.

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

“…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).…”

“…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, 2018Bucciarelli et al, , 2017Bucciarelli, Muthukumar et al, 2019;Yang et al, 2019).…”

A Thermal‐Reflow‐Based Low‐Temperature, High‐Pressure Sintering of Lyophilized Silk Fibroin for the Fast Fabrication of Biosubstrates

“…Due to the unique combination of properties, such as mechanical strength and toughness, biocompatibility, biodegradability, thermal stability, and easy processability, regenerated silk fibroin has been used as a functional biomaterial, when a positive interaction with living tissue is required. This has ranged from tissue engineering and regenerative medicine to biosensing . While a plethora of micro and nanoscale architectures of silk fibroin have been explored in the literature, films, fibers, microparticles, and gels, building larger, macroscale objects of fibroin has been challenging.…”

Patterning of protein‐based materials

“…Thereby, light was diffracted when passing radially transparent zones, whereas arrangement of the zones was designed to create constructive interference amplifying the radiation. [ 57 ] Upon further optimization of processing parameters during the micropatterning processes such as solvents [ 58 ] as well as quality and molecular weight of the precursor protein, [ 59 ] materials tuning could be driven by the application. Additionally, the introduction of metals, biodopants, drugs, functional molecules, or polymers without activity‐loss was possible due to potential implementation of negative‐tone lithography.…”