A low-fouling, self-assembled, graft co-polymer and covalent surface coating for controlled immobilization of biologically active moieties

Anne-Sophie Mertgen,Anne Géraldine Guex,Samuele Tosatti,Giuseppino Fortunato,René M Rossi,Markus Rottmar,Katharina Maniura-Weber,Stefan Zürcher

doi:10.1016/j.apsusc.2022.152525

Abstract

Current biointerfaces aiming to steer specific biological responses frequently lack either stability due to purely electrostatic interactions, bioactivity due to unspecific conjugation chemistries, specificity due to uncontrolled biological interactions such as fouling, or cytocompatibility due to harsh and toxic coating procedures. Here, we report a versatile surface modification platform for covalent tethering of selected biomolecules. New in this approach is the particular combination of modular binding blocks as graft co-polymer. Grafted to the backbone of PAcrAmTM multiple functionalities are strategically combined: covalent (silane) and non-covalent (lysine) surface binding groups for stability and self-assembly in mild buffered solution, PEG-azide chains for low fouling properties, and specific, controlled, covalent, linking of biologically active molecules. This modular strategy overcomes the previously mentioned limitations, for instance regarding bioactivity of the biological moiety due to highly specific strain-promoted azide-alkyne cycloaddition. The successful grafting of the copolymer was confirmed by 1H NMR. The immobilization of RGD peptides was characterized by combining surface analytical techniques, such as ToF-SIMS and ellipsometry, allowing quantification of immobilized molecules over an extensive range of concentrations (0.008–1.95 pmol·cm−2). The bioactivity over this range of concentrations was confirmed by in vitro cell studies, presenting a differential endothelial cell attachment and spreading. The modified substrates enabled the formation of an interconnected monolayer of endothelial cells. Furthermore, the modular platform allowed the co-immobilization of two bioactive functional groups, RGD and biotin, on the same surface, which could be exploited for the further development of controlled multi-functional biointerfaces for diverse biological applications in the future.

Highlights

Biointerfaces that enable controlled and specific interaction with the biological environment that they are exposed to are very critical to overcome current limitations such as in the successful integration of medical implants in the body or biosensing applications [1,2,3]
The modular platform allowed the co-immobilization of two bioactive functional groups, arginine-glycine-aspartic acid (RGD) and biotin, on the same surface, which could be exploited for the further development of controlled multi-functional biointerfaces for diverse biological applications in the future
For the synthesis of PAcrAmTM-g-(PEG-N3,NH2,Si) and reference polymer PAcrAmTM-g-(PEG,NH2,Si), the different amine-functional sidechains were attached by sequential stoichiometric grafting to the amine- reactive pPFPAc backbone (Fig. 1A) as described in previous publications [36,56]

Summary

Introduction

Biointerfaces that enable controlled and specific interaction with the biological environment that they are exposed to are very critical to overcome current limitations such as in the successful integration of medical implants in the body or biosensing applications [1,2,3]. For implant integration creating interfaces that allow steered adhesion of specific cells, which can perform natural biological functions are desired [4,5,6,7,8] To this end, adhesion peptides that mediate cell attachment [9] can be immobilized on a synthetic surface [9,10]. Adhesion peptides that mediate cell attachment [9] can be immobilized on a synthetic surface [9,10] Such adhesive peptides are derived from extracellular matrix proteins as for example RGD derived from fibronectin. For bio sensing applications, in order to obtain high sensitivity, sensor coatings

Results

Discussion

Conclusion