Protein adsorption onto polyester surfaces: Is there a need for surface activation?

Abstract

Surface hydrolysis of polyester scaffolds is a convenient technique suggested to promote protein adsorption for improving cell attachment. We have, therefore, investigated the effect of hydrolysis of polyester surfaces for protein adsorption to clarify the conditions needed. Three polyesters, poly(ethylene terephthalate) (PET), poly(lactic acid) (PLA), and poly(glycolic acid) (PGA), were selected. Adsorption was investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and quartz crystal microbalance (QCM). Hydrolyzed PET adsorbed significantly more proteins than nonhydrolyzed. Degradable polymers adsorbed at higher rates when the polymers were hydrolyzed prior to adsorption, but the same amount as nonhydrolyzed, suggesting spontaneous hydrolysis during the adsorption. XPS shows that hydrolysis prior to absorption for PET results in a surface nitrogen composition of ϳ14%, similar to pure protein (16%). Nonhydrolyzed PET surfaces showed only ϳ7% nitrogen, indicating protein layers thinner than ϳ10 nm. Adsorption to PLA and PGA shows nitrogen contents of 14 -15% in both cases. SEM revealed striking differences in morphology of the protein coating. Hydrolyzed or spontaneously hydrolyzable surfaces display a pronounced fibrous structure while nonhydrolyzed surfaces give smooth structures. In combination, the results show that surface hydrolysis increase adsorption rate, but not the amount of proteins on polyesters that degrades in vivo. Surface treatment of nondegradable polyester increases the total amount of proteins and induces the formation of fibrous protein structures. Post hydrolysis treatment by acetic acid, replacing the counter-ion to a proton, further enhances protein attachment. Finally, cell attachment experiments verifies that protein adsorption increase the cell attachment to polyester surfaces.

Assessing the Suitability of Electrospun Poly(Ethylene Terephthalate) and Polystyrene as Cell Carrier Substrates for Potential Subsequent Implantation as a Synthetic Bruch's Membrane

“…Closer evaluation of incubated PET spectra showed an increase in the number of carbon environments and a shift in the position of the oxygen peaks, as well as the presence of nitrogen peaks, suggesting that the N-terminal of the proteins were able to undergo aminolysis, opening the ester bond in PET (Figure 3) [31]. The two new carbon peaks found at 287.67 and 285.84 eV are -C(O)N and C-OH peaks, respectively, the nitrogen peak present is the nylon-like -C(O)N peak at 399.96 eV, which coincides with the suggestion of aminolysis occurring in the ester, and also explains why nitrogen was detected on untreated PET.…”

Design concepts and strategies for tissue engineering scaffolds

“…So, the addition of cell-binding peptides to a polymer can induce cell adhesion to otherwise nonadhesive or weakly adhesive surfaces. However, to introduce peptide moieties, scaffold materials need to contain appropriate functional groups, which may not be readily available in most resorbable aliphatic polyester polymers [20], [115].…”

Embroidered and Surface Modified Polycaprolactone-Co-Lactide Scaffolds as Bone Substitute: In Vitro Characterization

“…1,2,23,27 Surface properties of the scaffold material have a significant influence over initial protein interactions, which mediate subsequent cell response. Surface topography, chemistry, and wettability have shown to influence cell-material interactions.…”