Ellipsometric Evaluation of β‐Lactoglobulin Adsorption onto Low‐and High‐Energy Materials

Abstract

Ellipsometry was used to study solid-surface energetic and temperature effects on the apparent equilibrium adsorptive behavior exhibited by ,&lactoglobulin. Adsorption isotherms were constructed for ,&lactoglobulin on seven different silicon surfaces chemically modified to exhibit varying hydrophobicities: plateau values of adsorbed mass were observed to increase with increasing degree of solid-surface silanization with dichlorodimethylsilane. &Lactoglobulin isotherms at 2,27, and 52 "C were constructed on unsilanized and completely silanized silicon surfaces: adsorbed mass increased upon increasing temperature beyond 2 "C, but no difference was observed between isotherms drawn at 27 and 52 "C for either surface. Isotherms were then constructed for acrylic, polycarbonate, polyester, glass, and no. 304 stainless steel surfaces at 37 and 55 "C. In all cases, optical properties of the protein films were ellipsometrically measured and their adsorbed mass was calculated from film thickness and refractive index. The protein adsorption results recorded for the polymer, glass, and stainless steel surfaces could not be explained with reference to solid-surface hydrophobicity alone. For polymers, adsorbed mass is suggested to be related to the extensibility of molecular structure at the surface. Glass was observed to adsorb the greatest mass of /3-lactoglobulin, and no. 304 stainless steel the lowest; however, glass and the polymers, being transparent, presented a different optical problem for ellipsometry compared to that posed by silicon and stainless steel. A temperature dependence of P-lactoglobulin adsorption was not observed between 37 and 55 "C, probably due in part to the temperatures studied having been below the denaturation temperature of 0-lactoglobulin, as indicated by differential scanning calorimetry. 8756-7938/92/3008-0058$03.00/0 0

Monitoring Protein Fouling of Metal Surfaces via a Quartz Crystal Microbalance

“…They concluded that the denaturation of β-lactoglobulin was irreversible whereas denaturation of α-lactalbumin was highly reversible. Almalah et al (36) confirmed that high temperature increases the adsorption of β-lactoglobulin on hydrophilic and hydrophobic silicon. Elofsson et al (14) found adsorption during heat treatment was related to thermal unfolding and aggregation of β-lactoglobulin.…”

Building a working understanding of protein adsorption with model systems and serendipity

“…There we set up a system for in situ detection of protein adsorption by ellipsometry [1] and began quantifying surface and protein properties affecting the rate and extent of protein adsorption from single-protein solutions [2][3][4][5][6][7]. We worked mainly with the milk proteins ˛-lactalbumin, ˇ-lactoglobulin, BSA, and ˇ-casein.…”

Ellipsometry Study of the Adsorption of Molecules at Electrolyte Interfaces with Gold and Stainless Steel

“…Malmsten (12) and Lassen (13) describe competitive adsorption from binary Luggin reference electrode; (2) solution inlet; (3) platinum counter elecprotein solutions. Al-Malah et al (14) measure adsorption trode; (4) working electrode. of b-lactoglobulin onto a variety of surfaces, finding the greatest adsorption onto glass and the least onto stainless steel, the latter showing an adsorption of 4 mg/m 2 .…”