Transport-Limited Adsorption of Plasma Proteins on Bimodal Amphiphilic Polymer Co-Networks: Real-Time Studies by Spectroscopic Ellipsometry

Abstract

Traditional hydrogels are commonly limited by poor mechanical properties and low oxygen permeability. Bimodal amphiphilic co-networks (β-APCNs) are a new class of materials that can overcome these limitations by combining hydrophilic and hydrophobic polymer chains within a network of co-continuous morphology. Applications that can benefit from these improved properties include therapeutic contact lenses, enzymatic catalysis supports, and immunoisolation membranes. The continuous hydrophobic phase could potentially increase the adsorption of plasma proteins in blood-contacting medical applications and compromise in vivo material performance, so it is critical to understand the surface characteristics of β-APCNs and adsorption of plasma proteins on β-APCNs. From real-time spectroscopic visible (Vis) ellipsometry measurements, plasma protein adsorption on β-APCNs is shown to be transport-limited. The adsorption of proteins on the β-APCNs is a multistep process with adsorption to the hydrophilic surface initially, followed by diffusion into the material to the internal hydrophilic/hydrophobic interfaces. Increasing the cross-linking of the PDMS phase reduced the protein intake by limiting the transport of large proteins. Moreover, the internalization of the proteins is confirmed by the difference between the surface-adsorbed protein layer determined from XPS and bulk thickness change from Vis ellipsometry, which can differ up to 20-fold. Desorption kinetics depend on the adsorption history with rapid desorption for slow adsorption rates (i.e., slow-diffusing proteins within the network), whereas proteins with fast adsorption kinetics do not readily desorb. This behavior can be directly related to the ability of the protein to spread or reorient, which affects the binding energy required to bind to the internal hydrophobic interfaces.

End Point Versus Backbone Specificity Governs Characteristics of Antibody Binding to Poly(ethylene glycol) Brushes

“…We have recently used NR to study the specific adsorption of end-binding (EB) Abs to PEG brushes of variable grafting density σ and constant polymerization degree N (ref ). In contrast to conventional methods that merely yield the adsorbed protein amount per unit area, like surface plasmon resonance, quartz-crystal microbalance, , or ellipsometry, NR resolves matter distributions perpendicular to planar interfaces with high depth resolution and is therefore uniquely suited to structurally characterize protein adsorption to polymer brushes. The technique was therefore used to identify and characterize primary adsorption to the brush grafting surface as well as weak and strong ternary adsorption within the PEG brush itself.…”

Neutron Reflectometry Elucidates Protein Adsorption from Human Blood Serum onto PEG Brushes

“…The obtained value is low when compared to the extent of protein adsorption reported for commonly studied surface types such as polystyrene (PS) and iron oxide (typically ≳0.5 mg/m 2 for at least one abundant protein species) 51−53 and consistent with earlier studies reporting low protein adsorption to phospholipid surfaces. 49,50 In contrast to earlier studies of adsorption out of serum/plasma that utilized surface plasmon resonance (SPR), 33 quartz-crystal microbalance (QCM), 55,56 or ellipsometry, 57 our NR measurements yield not only Γ pro but also the structural details of the adsorbed protein layer. The adsorbed protein layer thickness, defined as the full width at half the maximum (fwhm) of the protein volume fraction distribution, is approximately 12 Å, corresponding to w pro ≈ 5 Å in eq 8.…”

Shear-Induced Microstructural Variations in Nanoemulsion-Laden Organohydrogel Fibers

“…The microstructural variation in the gelled precursor is photopolymerized by ultraviolet (UV) light at the outlet of the cylindrical millifluidic channel to generate a solid composite organohydrogel fiber. This system is different from the copolymer blends used to generate bulk hydrogels, in that the PDMS self-assembly process is mesoscopic rather than nanoscopic in nature. − There are two main advantages to our system: (1) the loading of hydrophobic substances is maximized to near saturation concentration by the presence of the mesoscale oil domains; (2) the mass transport properties can be controlled by physically changing the domain sizes through flow processing rather than through custom chemical syntheses of complex copolymers.…”