Plasma‐Assisted Deposition of Silk Fibroin on Different Surfaces

Abstract

The development of simple and versatile methods for the deposition of biocompatible coatings to protect or functionalize a range of materials with different shapes is an important challenge. In this study, a versatile, room‐temperature process is presented for the deposition of silk fibroin on different materials viz., glass, polyethylene terephthalate, Ti alloy, and poly(dimethylsiloxane). Coating with thin fibroin films is achieved using an atmospheric plasma torch, wherein a silk‐fibroin aerosol solution is used as the working gas. The method consists of two sequential processes: plasma modification of the surface, followed by plasma‐assisted deposition. This allows enhanced adhesion of the protein to the underlying surfaces, and the deposition even on non‐planar and flexible substrates. The deposited films are characterized by optical microscopy, atomic force microscopy, and scanning electron microscopy. Primary and secondary structures of the surface‐attached fibroin films are investigated by Fourier transform infrared spectroscopy. The proposed approach offers a tunable and controllable strategy for the controlled deposition of proteins on complex surfaces, for a wide range of biomedical and technological applications, including dentistry and bioelectronics.

Atmospheric Plasma‐Assisted Deposition and Patterning of Natural Polymers

“…In multiple deposition passes, the thickness and roughness depend on the number of runs that follows the same trend observed for silk fibroin plasma deposition (Figure S3, Supporting Information). [ 43 ]…”

“…The increased intensity of the absorption picks might be related to the crosslinked structure induced by the plasma reaction. [ 43, 67 ] The chitosan film deposited using oxygen as the cooling gas has a slightly higher intensity in the areas from 3500 to 2000 cm –1 and from 1630 to 1500 cm –1 in comparison with the chitosan film deposited using nitrogen as the cooling gas. Changes in the range from 1630 to 1500 cm –1 are promoted by using compressed air cooling, with oxygen molecules tending to neutralize free electrons from the plasma.…”

“…In order to assess the quality of adhesion of the deposited chitosan to the underlying substrates, a peel test using adhesive tape ( Figure a) and stability test in PBS buffer (Figure 4b) were performed. In comparison to plasma‐deposited silk fibroin films, [ 43 ] chitosan films show better adhesion to PDMS substrates. It is hypothesized that the outstanding adhesion is owing to chitosan's ability to link directly to the surface via various functional groups such as –COOH or –CHO.…”

“…Plasma deposition is a complex process that affects surfaces in terms of functionalization, sterilization, and etching, as well as the material inside the plasma tube by modification. [43] Plasma polymerization/deposition allows the formation of thin and homogeneous layers of different materials with strong adhesion to underlying surfaces. [51][52][53] Formed covalent bonds between functionalized substrate and deposited material enhance adhesion, preventing delamination.…”

“…To assess this, we showed the deposition of a second biopolymer, silk fibroin, whose plasma deposition was previously reported. [43] Fibroin is one of the most interesting protein-based biomaterials, [44] often investigated as a complementary material for chitosan. [45][46][47] Indeed, fibroin and chitosan share similar deposition pathways (e.g., photolithography [48][49] and inkjet printing [50] ).…”