Surface grafting of electrospun fibers using ATRP and RAFT for the control of biointerfacial interactions

Abstract

Background The ability to present signalling molecules within a low fouling 3D environment that mimics the extracellular matrix is an important goal for a range of biomedical applications, both in vitro and in vivo. Cell responses can be triggered by non-specific protein interactions occurring on the surface of a biomaterial, which is an undesirable process when studying specific receptor-ligand interactions. It is therefore useful to present specific ligands of interest to cell surface receptors in a 3D environment that minimizes non-specific interactions with biomolecules, such as proteins. Method In this study, surface-initiated atom transfer radical polymerization (SI-ATRP) of poly(ethylene glycol)-based monomers was carried out from the surface of electrospun fibers composed of a styrene/vinylbenzyl chloride copolymer. Surface initiated radical addition-fragmentation chain transfer (SI-RAFT) polymerisation was also carried out to generate bottle brush copolymer coatings consisting of poly(acrylic acid) and poly(acrylamide). These were grown from surface trithiocarbonate groups generated from the chloromethyl styrene moieties existing in the original synthesised polymer. XPS was used to characterise the surface composition of the fibers after grafting and after coupling with fluorine functional XPS labels. Results Bottle brush type coatings were able to be produced by ATRP which consisted of poly(ethylene glycol) methacrylate and a terminal alkyne-functionalised monomer. The ATRP coatings showed reduced non-specific protein adsorption, as a result of effective PEG incorporation and pendant alkynes groups existing as part of the brushes allowed for further conjugation of via azide-alkyne Huisgen 1,3-dipolar cycloaddition. In the case of RAFT, carboxylic acid moieties were effectively coupled to an amine label via amide bond formation. In each case XPS analysis demonstrated that covalent immobilisation had effectively taken place. Conclusion Overall, the studies presented an effective platform for the preparation of 3D scaffolds which contain effective conjugation sites for attachment of specific bioactive signals of interest, as well as actively reducing non-specific protein interactions.

Modular and Versatile Spatial Functionalization of Tissue Engineering Scaffolds through Fiber‐Initiated Controlled Radical Polymerization

“…These have not been fully exploited in scaffold functionalization and yet are extremely powerful methods for preparing antifouling surfaces. Atom transfer radical polymerization (ATRP) and reversible addition‐fragmentation chain transfer (RAFT) have been used to attach polymers to a variety of surfaces to generate surface‐derived functionality 10, 11, 12, 13. These polymerization methods are versatile and offer excellent control of chain length, architecture, reaction kinetics, and they can add a vast array of functionality as a large number of monomers may be incorporated, which dictates the final material properties 10, 14.…”

Optimization of Aqueous SI‐ATRP Grafting of Poly(Oligo(Ethylene Glycol) Methacrylate) Brushes from Benzyl Chloride Macroinitiator Surfaces

“…The absence of hydrolysable ester groups in the initiator offers extra stability that may be vital in certain applications. These initiators may also be advantageous due to ease‐of‐incorporation of the initiator moiety via (co)polymerization or covalent attachment of commercially available vinylbenzyl chloride (VBC) or other derivatives. This avoids a further functionalization step e.g.…”

RAFT Polymerization – Then and Now

“…These will not be recounted in detail here. Significant developments have been made in electroactive and optoelectronic polymers (101) (organic semiconductors (202)(203)(204)(205), materials for organic light emitting diodes (204), photochromics (206)), the biomedical field (therapeutic delivery (184,(187)(188)(189)(207)(208)(209), surfaces (210,211) personal care (212)), and industrial applications (rheology control agents (213), surface functionalized membranes (214)) and many other areas.…”