Effects of surface wettability and contact time on protein adhesion to biomaterial surfaces - PubMed (original) (raw)

Effects of surface wettability and contact time on protein adhesion to biomaterial surfaces

Li-Chong Xu et al. Biomaterials. 2007 Aug.

Abstract

Atomic force microscopy (AFM) was used to directly measure the adhesion forces between three test proteins and low density polyethylene (LDPE) surfaces treated by glow discharge plasma to yield various levels of water wettability. The adhesion of proteins to the LDPE substrates showed a step dependence on the wettability of surfaces as measured by the water contact angle (theta). For LDPE surfaces with theta> approximately 60-65 degrees , stronger adhesion forces were observed for bovine serum albumin, fibrinogen and human FXII than for the surfaces with theta<60 degrees . Smaller adhesion forces were observed for FXII than for the other two proteins on all surfaces although trends were identical. Increasing the contact time from 0 to 50s for each protein-surface combination increased the adhesion force regardless of surface wettability. Time varying adhesion data was fit to an exponential model and free energies of protein unfolding were calculated. This data, viewed in light of previously published studies, suggests a 2-step model of protein denaturation, an early stage on the order of seconds to minutes where the outer surface of the protein interacts with the substrate and a second stage involving movement of hydrophobic amino acids from the protein core to the protein/surface interface. Impact statement: The work described in this manuscript shows a stark transition between protein adherent and protein non-adherent materials in the range of water contact angles 60-65 degrees , consistent with known changes in protein adsorption and activity. Time-dependent changes in adhesion force were used to calculate unfolding energies relating to protein-surface interactions. This analysis provides justification for a 2-step model of protein denaturation on surfaces.

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Figures

Fig. 1

Fig. 1

AFM topographic images of LDPE surfaces following plasma treatment. (a) 0, (b) 15, (c) 45, (d) 60, (e) 90, and (f)150 min. The mean water contact angle value of each surface is shown below the image. Scan size is 2 mm × 2 mm, z scale is 100 nm.

Fig. 2

Fig. 2

Average adhesion forces for Si3N4 probes to LDPE surfaces having different water adhesion tension values. Shaded area is drawn to aid the eye.

Fig. 3

Fig. 3

(a) Representative separation force curves for BSA coated probes and LDPE surfaces, showing larger adhesion forces for BSA and poorly wettable surfaces than BSA and wettable surfaces. (b) Average adhesion forces of BSA coated probes to LDPE surfaces with different water adhesion tension values. Shaded area is drawn to aid the eye.

Fig. 4

Fig. 4

(a) Representative separation force curves for Human Fibrinogen coated probes with LDPE surfaces, showing larger adhesion forces to non-wettable surfaces than to wettable surfaces. (b) Average adhesion forces for Human Fibrinogen coated tips to LDPE surfaces with different water adhesion tension values. Shaded area is drawn to aid the eye.

Fig. 5

Fig. 5

(a) Representative separation force curves for Human Factor XII coated probes with LDPE surfaces, showing larger adhesion forces for poorly wettable surface than wettable surfaces. (b) Average adhesion forces of HFXII coated tips to PE surfaces with different water adhesion tension values. Shaded area is drawn to aid the eye.

Fig. 6

Fig. 6

Representative retraction curves for BSA probes and (a) poorly wettable LDPE (water contact angle = 83.7°) or (b) highly wettable LDPE (water contact angle = 50.5°) surfaces at increasing contact times.

Fig. 7

Fig. 7

Mean values of adhesion forces between protein-coated probes and LDPE surfaces with contact time, (a) BSA, (b) Fibrinogen, (c) HF XII. Curves illustrate fit of the exponential described in Eq. (2) to the experimental data.

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