Plasma Ion Implantation of Silk Biomaterials Enabling Direct Covalent Immobilization of Bioactive Agents for Enhanced Cellular Responses

Abstract

Silk fibroin isolated from Bombyx mori cocoons is a promising material for a range of biomedical applications, but it has no inherent cell-interactive domains, necessitating functionalization with bioactive molecules. Here we demonstrate significantly enhanced cell interactions with silk fibroin biomaterials in the absence of biofunctionalization following surface modification using plasma immersion ion implantation (PIII). Further, PIII treated silk fibroin biomaterials supported direct covalent immobilization of proteins on the material surface in the absence of chemical cross-linkers. Surface analysis after nitrogen plasma and PIII treatment at 20 kV revealed that the silk macromolecules are significantly fragmented, and at the higher fluences of implanted ions, surface carbonization was observed to depths corresponding to that of the ion penetration. Consistent with the activity of radicals created in the treated surface layer, oxidation was observed on contact with atmospheric oxygen and the PIII treated surfaces were capable of direct covalent immobilization of bioactive macromolecules. Changes in thickness, amide and nitrile groups, refractive index, and extinction coefficient in the wavelength range 400-1000 nm as a function of ion fluence are presented. Reactions responsible for the restructuring of the silk surface under ion beam treatment that facilitate covalent binding of proteins and a significant improvement in cell interactions on the modified surface are proposed.

Effects of carbon and nitrogen plasma immersion ion implantation on bioactivity of zirconia

“…This may be due to the fact that when the nitrogen-containing functional groups were implanted on the surface of the materials aer plasma treatment, a suitable microenvironment was created which promoted cell adhesion and proliferation, C60N6 group of high relative potential was more suitable for the biological behavior of cells. Previous studies 17,34,40,41 have also shown that positively charged nitrogen functionalities could promote cell expression thus improving biological activity, which was consistent with our ndings.…”

The Materiobiology of Silk: Exploring the Biophysical Influence of Silk Biomaterials on Directing Cellular Behaviors

“…SF has reactive carboxyl and amino groups in its side chains that can be conjugated to different functional groups. For example, plasma immersion ion implantation (PIII) treatments have been used to covalently bind proteins to the SF surface and improve cellular interactions ( Kondyurin et al, 2018 ). Another simple surface modification technique involves plasma etching for grafting poly acrylic acid (pAAc) and poly hydroxyethylmethacrylate on regenerated SF films.…”

Hydrogel−Solid Hybrid Materials for Biomedical Applications Enabled by Surface‐Embedded Radicals

“…[ 47–51 ] Over the last decade, we have used PIII for reagent‐free, covalent attachment of biomolecules, such as proteins, peptides, and DNA on surfaces. [ 12,52–56 ] The covalent attachment occurs when molecules in physical contact with the surface react with surface‐embedded radicals generated by the implanted ions. Such a chemical linker‐free, radial‐based mechanism for biomolecule immobilization makes it possible to tune the surface density and orientation of molecules by simply tuning the solution pH or applying external electric fields during the immobilization.…”