Generalized Protein-Repellent Properties of Ultrathin Homopolymer Films

Abstract

Fouling is the undesirable accumulation of a material on a wide variety of objects and has now become a widespread global problem from land to ocean with both economic and environmental penalties. Here, we report protein-repellent properties of ultrathin polymer films that are considered to be of structural origin and generalizable across homopolymer systems. Ultrathin polymer films composed of polystyrene, poly­(2-vinyl pyridine), poly­(methyl methacrylate), and polybutadiene with different thicknesses (h) ranging from 2 to 60 nm were prepared on silicon substrates. Bovine serum albumin and fibrinogen (both are fluorescein-labeled) were used as model proteins. The polymer thin films were incubated in the protein solution, removed, and then rinsed with water. The fluorescence intensity I(h) measured by a photon-counting spectrofluorometer generated a master curve over the film thickness regardless of the polymer and protein choice, revealing the two different protein adsorption regimes with the following thicknesses: (i) below the critical thickness (h c ≅ 20 nm), I(h) is minimal (nearly zero at h < 5 nm) and exhibits a very weak thickness dependence; (ii) at h > h c, I(h) exhibits very strong thickness dependence (I(h) ∼ h 2). Molecular dynamics simulations identified a positive correlation between protein adsorption and highly packed conformations of polymer chains, which either adsorb on the substrate or do not adsorb but are in contact with the adsorbed polymer chains, resulting in a protein-repellent “dense layer” at h < h c. In addition, the effect of the dense layer propagates into the film interior up to at least 60 nm, resulting in an “interphase” that shows the quadratic adsorption behavior. These experimental and computational findings detail a new mechanism behind the structure-driven protein-repellent properties of polymer structures under nanoconfinement over surface chemistry.

Antifouling Surfaces Enabled by Surface Grafting of Highly Hydrophilic Sulfoxide Polymer Brushes

“…A common method of achieving antifouling properties is to graft antifouling polymers onto the material surface. These antifouling polymers are generally highly water-soluble, thus forming a hydration layer near the material surface. , The expulsion or removal of water molecules from these layers is a prerequisite but thermodynamically unfavored for protein adsorption. ,, Therefore, the hydration layer near the surfaces acts as a barrier to prevent biological adhesion. One of the most widely used antifouling polymeric materials is poly­(ethylene glycol) (PEG).…”

“…13,14 The expulsion or removal of water molecules from these layers is a prerequisite but thermodynamically unfavored for protein adsorption. 13,15,16 Therefore, the hydration layer near the surfaces acts as a barrier to prevent biological adhesion. One of the most widely used antifouling polymeric materials is poly(ethylene glycol) (PEG).…”

Langevin dynamics simulation on optimal conditions for large and stable loops of adsorbed homopolymers on substrates

“…Adsorption of polymer chains on a solid surface is a universal interfacial behavior. The adsorption of polymers plays a very important role in the stability of colloidal particles, 1,2 nanoscale surface modification, 3,4 antifouling, 5,6 adhesiveness 7,8 and glass transition temperature of polymer films. [9][10][11] The adsorbed chains usually have three kinds of structures: train, loop, and tail, corresponding to continuously adsorbed segments, segments between two adsorbed trains, and non-adsorbed segments at chain's end, respectively.…”

Lubricin-Inspired Loop Zwitterionic Peptide for Fabrication of Superior Antifouling Surfaces

“…4 Various strategies have been developed for antifouling, among which hydrophilic materials have been extensively studied because the removal of bound water is thermodynamically unfavored. 5,6 Poly(ethylene glycol) (PEG) and its derivatives exhibit an antifouling effect toward a wide variety of proteins, while its auto-oxidation limits its application. 7−9 Over the past decade, zwitterionic polymers containing alternating anionic and cationic groups have aroused considerable interest because of their good chemical stability and excellent antifouling activity.…”

“…Biofouling is the undesirable adsorption of proteins, bacteria, and microorganisms, and it poses significant challenges in a wide range of fields ranging from medical devices to industrial equipment. − Nonspecific protein adsorption to surfaces is generally considered as the first stage of forming biofouling films as it would facilitate the subsequential adsorption of bacteria and cells . Various strategies have been developed for antifouling, among which hydrophilic materials have been extensively studied because the removal of bound water is thermodynamically unfavored. , Poly­(ethylene glycol) (PEG) and its derivatives exhibit an antifouling effect toward a wide variety of proteins, while its auto-oxidation limits its application. − Over the past decade, zwitterionic polymers containing alternating anionic and cationic groups have aroused considerable interest because of their good chemical stability and excellent antifouling activity . The hydration layer formed by the solvation of the charged groups, assisted by hydrogen bonding, prevents the adsorption of proteins .…”