Applied Surface Science 349 (2015) 763–773 Contents lists available at ScienceDirect Applied Surface Science jou rn al h om ep age: www.elsevier.com/locate/apsusc Effect of wettability and surface roughness on the adhesion properties of collagen on PDMS films treated by capacitively coupled oxygen plasma J.A. Juárez-Moreno a , A. Ávila-Ortega b , A.I. Oliva c , F. Avilés a , J.V. Cauich-Rodríguez a,∗ a Centro de Investigación Científica de Yucatán, Calle 43 No. 130, Col. Chuburna de Hidalgo C.P., 97200 Mérida, Yucatán, Mexico b Facultad de Ingeniería Química—UADY, Periférico Norte Kilómetro 33.5, Col. Chuburna de Hidalgo Inn, C.P. , 97203 Mérida, Yucatán, Mexico c Centro de Investigación y de Estudios Avanzados del IPN–Unidad Mérida, Km. 6 Antigua carretera a Progreso Apdo. Postal 73, Cordemex, 97310 Mérida, Yucatán, Mexico a r t i c l e i n f o Article history: Received 3 February 2015 Received in revised form 29 April 2015 Accepted 4 May 2015 Available online 18 May 2015 Keywords: Oxygen plasma Surface treatment PDMS Collagen Adhesion a b s t r a c t Direct chemical bonding of biomolecules to the surface of chemically inert polymers such as poly- dimethylsiloxane (PDMS) is not easily achieved. Therefore, pre-activation of such materials, followed by attachment of the biomolecule is necessary. This paper describes a procedure to functionalize a PDMS surface by oxygen-based plasma followed by the adhesion of collagen type I for the preparation of adhesive-free bilayer composite intended as skin substitute. Plasma treatments between 40 and 120 W for 5 to 15 min were used and the extent of surface modification was followed by contact angle, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM) and adhesion test. It was found that as the plasma power and time were increased, PDMS contact angle decreased while surface roughness increased as revealed by SEM and AFM. The formation of oxygen-containing functional groups at the surface was detected by FTIR. T-peel tests, performed on PDMS treated at 80 W/13 min and covered with collagen showed maximum peel strength of 0.1 N/mm which was 3 times higher than that measured for the untreated bilayer composite. The observed enhancement in the adhesion strength was attributed to the increased mechanical interlocking driven by the increased roughness and the formation of hydrophilic functional groups. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Skin substitutes and dressing materials are commonly used for the treatment of burns and ulcers due to diabetes complica- tions. For the treatment of superficial wounds, these materials should desirably be soft, non-adherent but sufficiently tacky to allow attachment to intact skin around the wound and to other absorbent layers. The wound-contacting material also needs to be liquid-permeable to allow passage of wound fluid, especially for heavily exuding wounds such as burns. In addition, the material should also be non-irritating, inexpensive, and stable to common sterilization methods such as ionizing radiation [1]. Semi-permeable polydimethylsiloxane (PDMS) films are widely used in the manufacture of wound dressings, because of its ability ∗ Corresponding author. Tel.: +52 9999428330; fax: +52 9999813900. E-mail address: jvcr@cicy.mx (J.V. Cauich-Rodríguez). to simulate the function of the skin of moisture transmission, flow properties of thixotropic nature while allowing uniform application with controlled penetration into surfaces. Silicones are polymers that are built around a frame of silicon and oxygen atoms, on which methyl groups are often present [2]. The individual polymer chains may differ in length and in the degree of crosslinking parameters that are critical in defining the physical properties of silicones [3]. These materials have been used in medicine for more than 65 years due to its good biocompatibility, low toxicity, good mechanical properties, and good thermal and chemical stability [2,4]. It is also relatively inexpensive, and easy to process and their application ranges from catheters to implants and prostheses. Two commercial examples of the use of PDMS in wound dressings are Integra ® and Biobrane ® [5]. These cell-free prod- ucts consist of a thin PDMS film coated with collagen, which makes it both biocompatible and hydrophilic and currently, they have become gold standards for the treatment of major burn wounds. For this type of applications, PDMS is typically used as the http://dx.doi.org/10.1016/j.apsusc.2015.05.063 0169-4332/© 2015 Elsevier B.V. All rights reserved.