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Open AccessArticle

Bifunctional Bioactive Polymer Surfaces with Micrometer and Submicrometer-sized Structure: The Effects of Structure Spacing and Elastic Modulus on Bioactivity

1
Freiburg Center for Interactive Materials and Bioinspired Technologies (FIT) and Department of Microsystems Engineering (IMTEK), Albert-Ludwigs-Universität, Georges-Köhler-Allee 105, 79110 Freiburg, Germany
2
Department of Advanced Technology and New Materials Research Institute, City of Scientific Research and Technology Applications, New Borg El-Arab City, 21934 Alexandria, Egypt
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Academic Editor: Guillaume Delaittre
Molecules 2019, 24(18), 3371; https://doi.org/10.3390/molecules24183371
Received: 1 August 2019 / Revised: 16 August 2019 / Accepted: 27 August 2019 / Published: 16 September 2019
(This article belongs to the Special Issue Chemical Surface Functionalization)
This study presents a comparison of two types of bifunctional structured surface that were made from the same polymer –– an antimicrobial polycation (a synthetic mimic of an antimicrobial peptide, SMAMP) and a protein-repellent polyzwitterion (poly(sulfobetaines), PSB). The first type of bifunctional surface was fabricated by a colloidal lithography (CL) based process where the two polymers were immobilized sequentially onto pre-structured surfaces with a chemical contrast (gold on silicon). This enabled site-selective covalent attachment. The CL materials had a spacing ranging from 200 nm to 2 µm. The second type of structured surface (spacing: 1 – 8.5 µm) was fabricated using a microcontact printing (µCP) process where SMAMP patches were printed onto a PSB network, so that 3D surface features were obtained. The thus obtained materials were studied by quantitative nanomechanical measurements using atomic force microscopy (QNM-AFM). The different architectures led to different local elastic moduli at the polymer-air interface, where the CL surfaces were much stiffer (Derjaguin-Muller-Toporov (DMT) modulus = 20 ± 0.8 GPa) compared to the structured 3D networks obtained by µCP (DMT modulus = 42 ± 1.1 MPa). The effects of the surface topology and stiffness on the antimicrobial activity against Escherichia coli, the protein repellency (using fibrinogen), and the compatibility with human gingival mucosal keratinocytes were investigated. The softer 3D µCP surfaces had simultaneous antimicrobial activity, protein repellency, and cell compatibility at all spacings. For the stiffer CL surfaces, quantitative simultaneous antimicrobial activity and protein repellency was not obtained. However, the cell compatibility could be maintained at all spacings. The optimum spacing for the CL materials was in the range of 500 nm–1 µm, with significantly reduced antimicrobial activity at 2 µm spacing. Thus, the soft polymer network obtained by µCP could be more easily optimized than the stiff CL surface, and had a broader topology range of optimal or near-optimal bioactivity. View Full-Text
Keywords: chemical surface modification; colloidal lithography; microcontact printing; structured polymer surfaces; surface-cell interactions chemical surface modification; colloidal lithography; microcontact printing; structured polymer surfaces; surface-cell interactions
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MDPI and ACS Style

Elsayed, S.M.; Widyaya, V.T.; Shafi, Y.; Eickenscheidt, A.; Lienkamp, K. Bifunctional Bioactive Polymer Surfaces with Micrometer and Submicrometer-sized Structure: The Effects of Structure Spacing and Elastic Modulus on Bioactivity. Molecules 2019, 24, 3371.

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