Plasma polymerised nanoscale coatings of controlled thickness for efficient solid-phase presentation of growth factors.

Andres Alba-Perez,Matthew J Dalby,Manuel Salmeron-Sanchez,Vineetha Jayawarna,Peter G Childs

doi:10.1016/j.msec.2020.110966

Andres Alba-Perez, Matthew J Dalby + Show 3 more

Open Access

https://doi.org/10.1016/j.msec.2020.110966

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Abstract

The engineering of biomaterial surfaces and scaffolds for specific biomedical and clinical application is of growing interest. Certain functionalised surfaces can capture and deliver bioactive molecules, such as growth factors (GF), enhancing the clinical efficacy of such systems. With a custom-made plasma polymerisation reactor described here we have developed bioactive polymer coatings based on poly(ethyl acrylate) (PEA). This remarkable polymer unfolds fibronectin (FN) upon adsorption to allow the GF binding region of FN to sequester and present GFs with high efficiency. We systematically evaluate process conditions and their impact on plasma polymerised PEA coatings and characterise the effect of plasma power and deposition time on thickness, wettability and chemical composition of the coatings. We demonstrate that functional substrate roughness can be maintained after deposition of the polymer coatings. Importantly, we show that coatings deposited at different conditions all maintain a similar or better bioactivity than spin coated PEA references. We show that in PEA plasma polymerised coatings FN assembles into nanonetworks with high availability of integrin and GF binding regions that sequester bone morphogenetic protein-2 (BMP-2). We also report similar mesenchymal stem cell adhesion behaviour, as characterised by focal adhesions, and differentiation potential on BMP-2 coated surfaces, regardless of plasma deposition conditions. This is a potent and versatile technology that can help facilitate the use of GFs in clinical applications.

Highlights

Surface modification is a versatile and potent tool in the development of new biomaterials for tissue engineering
In our previous studies we have shown that plasma-polymerised poly(ethyl acrylate) (PEA) coatings are able to promote FN assembly and effective presentation of ultra-low doses of bone morphogenetic protein-2 (BMP-2) growth factors (GF)
Further control of substrate roughness, with smaller features preserved, could be achieved using shorter and lower power plasma depositions, as the experiments reported here were performed with our highest deposition energy and we have shown that much thinner coatings can be produced with lower energies

Summary

Introduction

Surface modification is a versatile and potent tool in the development of new biomaterials for tissue engineering. Surface treatment technologies can critically improve cell-material interactions and specific functional properties of the material in a biological environment. With a proper modification strategy, a material's surface can be tailored to improve cellular biocompatibility, improving cell adhesion [7], proliferation [8] and differentiation [9], amongst other functional changes. Plasma polymerisation has received increased attention in biomaterials engineering due to its ability to deposit a highly crosslinked, nanometric, thin film of polymer at the cell-material interface [15]. Reactive species (e.g. ions, radicals) are able to interact with the substrate material and undergo polymerisation at this interface creating a film that adheres firmly to the substrate. The process can be carried out with a variety of electrode configurations that typically involve low pressure and low temperatures

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