Interrelation of Elasticity, Isotherm of Adsorbed Proteins, and its Subsequent Displacement by a Surfactant

Abstract

Quartz crystal microbalance with dissipation (QCM-D) is used to study the adsorption characteristics of insulin, myoglobin, bovine serum albumin, and β-galactosidase over amine and methyl surfaces. The water-based and D2O-based phosphate buffers are used for making protein solution. The kinetics of adsorption data, equilibrium adsorption data, and the elasticity of an adsorbed protein is obtained experimentally. A kinetic model of the adsorption of protein with surface phase is developed and fitted to experimental kinetic data. The kinetic parameter involving the first binding step with the surface depends on the surface and physical characteristics of the protein such as charge and component of the secondary structure. The experimental adsorption isotherm data are fitted to a multilayer model with two equilibrium adsorption constants (K s and K L). The relative strength of adsorption over the bare surface is denoted by K s, and the relative adsorption strength of protein over the adsorbed protein is denoted by K L. A protein containing a higher amount of β content has a higher K s value during its adsorption on amine surface. The elastic component G′ of the viscoelastic properties of the adsorbed proteins is found to be high for the protein layer obtained through high K s and low K L values. The desorption kinetics of the adsorbed proteins using a surfactant solution is also investigated. The elastic properties of the adsorbed proteins and desorption characteristics of the adsorbed proteins by a surfactant (sodium dodecyl sulfate) are strongly related to the adsorption strengths determining factors K s and K L. An adsorbed protein obtained through a high K s value is difficult to remove by the surfactant solution.

Adsorption and Conformation Behavior of Lysozyme on a Gold Surface Determined by QCM-D, MP-SPR, and FTIR

“…In contrast, for the albumin hydrated in 80%, the elasticity modulus was equal to 250 kPa, which corresponds well with those studies [ 26 ]. Similar values of shear modulus at the level of 100-kPa were also recorded by I. Sharma and S. Pattanayek for myoglobin, which is of a similar size to lysozyme, in the concentration of 250–1000 ppm dissolved in water and adsorbed on an APDMES surface [ 59 ]. According to the presented results, an increase in lysozyme concentration causes a reduction in shear modulus, which is related to more elastic properties during progressive bilayer formation.…”

Chemical functionality of surfaces for the characteristic adsorption of melamine

“…Silica‐coated quartz crystal and silicon wafers were utilized in our investigations. The cleaning and modification procedures were discussed extensively in our previously reported work 14–19 . A rigorous cleanup method was adopted in removing all impurities from the wafer interfaces.…”

“…The silica quartz crystal was cleaned sequentially with ethanol and water for 5 min in the first stage. Next, the silica‐coated quartz crystal was cleaned using an Ammonia‐peroxide mixture (water, hydrogen peroxide, and ammonium hydroxide in the volumetric ratio 5:1:1) as discussed in earlier publications 16,18 . The thoroughly clean substrate is placed in the glove box to dry and prevent exposure to ambient contaminants.…”

“…Adsorption isotherms are analyzed to determine the characteristics of adsorption and the distribution of adsorbate over an adsorbent. The investigation aimed to determine melamine molecules' interaction with the functionalized surface as the concentration increased 16,19 . The modified Brunauer–Emmett–Teller (mBET) model with n layers was used to determine the equilibrium adsorbed mass at a given concentration of melamine 16,22 …”

“…The mBET adsorption isotherm, 22 which was used to fit the adsorption data of various molecules 16 on different types of surfaces is given by where Γ m is the amount of adsorbed species required to achieve maximum monolayer adsorption (mg/m 2 ), and n represents the maximum number of layers on adsorbed layers on a solid substrate. K S and K L are denoted as the equilibrium adsorption constant for the primary and subsequent layers.…”