Tissue engineering (TE) is the discipline which includes both creation of the new tissue and design and realization of the cells on substrates [1, 2]. Substrates play a key role in creation of the cell environment . To guide the organization, growth, and differentiation of cells in TE constructs, the biomaterial scaffold should be able to provide not only a physical support but also the chemical and biological clues needed in forming functional tissue [4–6].
Biomaterials and various synthetic and natural materials, such as polymers, ceramics, metals, or their composites, have been investigated and used in different manners [5, 7]. Polymeric materials have been widely studied as substrates for tissue engineering due to their unique features such as mechanical properties, high availability, low cost, and relatively easy design and production [6, 8]. However, only a few polymers provide the biocompatibility needed to be used with the cells in vitro and in vivo. High-density polyethylene (HDPE) has been extensively used for application such as the part of orthopedic implants . To induce a regeneration process and to avoid the problems due to tissue replacement with a permanent implant, research has been oriented towards the development of polymers that would degrade and could be replaced by human tissue produced by the cells surrounding the material . Despite of their advantages, however, some of their characteristic properties, like wettability, adhesion, surface composition, and suchlike are insufficient for many applications. The positive effect of the above-mentioned properties and also biocompatibility of the polymer surface provide an opportunity of modification of existing material with bioactive molecules (amino acids, peptides, anticoagulants) bound by covalent bonds to polymer surface [11–13].
Polymer surfaces are often modified by thin layers of protein-like collagen or fibronectin to improve their biocompatibility . Bioactive molecules influence also the growth factors and regulate cell adhesion, migration, and proliferation [9, 15]. Bovine serum albumin (BSA) is a globular protein that is used in numerous biochemical applications. Bovine serum albumin (BSA) can be used as a reference (model) protein in which its properties are compared with other proteins. BSA is also included in the protein part of the various media used for operations with cells. BSA was chosen as a representative protein present in cell culture as a supplement to increase the growth and productivity of cells and increase overall cell health.
A very important part of the general study of biocompatibility of materials is the surface characterization of the prepared substrates and adhered bioactive compounds. As basic parameters influencing the cell-substrate interaction, surface chemistry, polarity, wettability morphology, and roughness can be included.
In this work, the influence of BSA protein grafting on the surface properties of the polyethylene (HDPE) and poly-l-lactide acid (PLLA) was studied. HDPE was chosen as the representative of the non-polar/non-biodegradable polymer. With its very simple structure containing only carbon and hydrogen atoms, this polymer can serve as a model material. PLLA was chosen as a polar/biodegradable polymer, whose cell affinity is often compromised because of its hydrophobicity and low surface energy . The surface properties were characterized by X-ray photoelectron spectroscopy, nano-LC-ESI-Q-TOF mass spectrometry, atomic force microscopy, electrokinetic analysis, and goniometry. One of the motivations for this work is the idea that due to cell interaction with the substrate, the proteins will form an interlayer between the cell and the substrate surface .