Protein–polymer interaction: Transfer loading at interfacial region of PES-based membrane and BSA Hamidreza Sadegh , 1 Rahul Sahay, 2 Shivani Soni 3 1 Faculty of Chemical Technology and Engineering, Institute of Inorganic Chemical Technology and Environmental Engineering, West Pomeranian University of Technology, ul. Pulaskiego 10, Szczecin 70-322, Poland 2 Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372 3 Department of Biological Sciences, California State University, Fullerton, California 9283 Correspondence to: H. Sadegh (E-mail: hamid-sadegh@zut.edu.pl) and (E-mail: h.sadegh@chemist.com) ABSTRACT: The adsorption of proteins onto polymeric surfaces is encountered in many natural and industrial processes and is a prerequi- site to their efficient identification, separation, and purification by methods such as chromatography, and filtration. Nevertheless, the exact nature of the adsorption mechanisms and interfacial interactions is not easy to identify for a given protein–polymer system. Here, we aim to document the adsorption mechanism of a protein–polymer system by investigating the adsorption as well as desorption phenomenon of a protein [bovine serum albumin (BSA)] from the polymeric surface [polyethersulfone (PES)]. The analyses performed to document the adsorption mechanism of the BSA–PES system include scanning electron microscope (SEM), attenuated total reflection-Fourier trans- form infrared (FTIR), contact angle, zeta potential, surface charge density measurement, and Derjaguin–Landau–Verwey–Overbeek (DLVO). Here, SEM and FTIR identified the physical and chemical properties of pure PES and PES–BSA membranes. The low water con- tact angle of the PES–BSA membrane confirms its applicability for tissue engineering applications. Further, the zeta potential, surface charge density measurement, and DLVO analyses were performed to document the adsorption mechanism. The adsorption of BSA parti- cles on the PES surface was carried out for pH values that ranged from 4 to 10 for contact times that ranged from 1 to 3 days. A mono- tonic increase in the zeta potential of the PES–BSA system indicated considerable adsorption of BSA particles on the PES surface. Further, BSA adsorption was very strong for pH values greater than 4.7 which confirms to strong electrostatic interactions between BSA and PES. The strong electrostatic interaction is also collaborated by low desorption rate, which was only 22% for pH 10 after 3 days of contact. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47931. KEYWORDS: adsorption; albumin; bovine serum; DLVO; membranes; polymer; protein; zeta potential Received 12 December 2018; accepted 5 April 2019 DOI: 10.1002/app.47931 INTRODUCTION The phenomenon of protein adsorption on a polymer membrane is seen in a wide variety of applications. 1–4 The applications include tis- sue engineering applications both in vitro and in vivo, biophysics, pharmaceutical sciences, and sensors. 5–11 The phenomenon is realized in many industrial applications such as protein purification/ separation, solid-phase immunoassay, chromatography, and filtration. 12–16 The protein-coated polymeric membrane displays properties which differ drastically from membranes with no protein coating. Therefore, understanding the adsorption process is critical to control, predict, and manipulate protein adsorption to design suit- able membranes to yield intended applications. Protein adsorption has been thoroughly studied in the last two decades. 17–21 Neverthe- less, it is difficult to predict the interaction at the interfaces between proteins and polymeric particles for several reasons including the large size of proteins molecules compared to particles of the poly- meric membrane. Further, the surface morphology of polymeric membranes affects the adsorption of protein to their surface. Researchers have found both hydrophilic and hydrophobic surfaces support protein adsorption. 22,23 Other factors that can affect the pro- tein adsorption on polymeric membrane include rigidity of the poly- meric particles. Protein properties such as isoelectric point (IEP), solubility, and its molecular weight affect its adsorption to the poly- meric surface as well. Also, buffer solution properties such as its pH, ionic strength, and viscosity can affect the adsorption process. 24–29 Here, we examined the adsorption of a protein [bovine serum albu- min (BSA)] onto a polyethersulfone (PES) polymeric surface. Hydrophilic PES was chosen because it is widely used in tissue engineering applications, such as sterile filtration and infusion therapy. 30 BSA was chosen because of its stability and lack of © 2019 Wiley Periodicals, Inc. 47931 (1 of 12) J. APPL. POLYM. SCI. 2019, DOI: 10.1002/APP.47931