Computational Investigation of Antifouling Property of Polyacrylamide Brushes

Abstract

Antifouling materials and coatings have broad fundamental and practical applications. Strong hydration at polymer surfaces has been proven to be responsible for their antifouling property, but molecular details of interfacial water behaviors and their functional roles in protein resistance remain elusive. Here, we computationally studied the packing structure, surface hydration, and protein resistance of four poly­(N-hydroxyalkyl acrylamide) (PAMs) brushes with different carbon spacer lengths (CSLs) using a combination of molecular mechanics (MM), Monte Carlo (MC), and molecular dynamics (MD) simulations. The packing structure of different PAM brushes were first determined and served as a structural basis for further exploring the CSL-dependent dynamics and structure of water molecules on PAM brushes and their surface resistance ability to lysozyme protein. Upon determining an optimal packing structure of PAMs by MM and optimal protein orientation on PAMs by MC, MD simulations further revealed that poly­(N-hydroxymethyl acrylamide) (pHMAA), poly­(N-(2-hydroxyethyl)­acrylamide) (pHEAA), and poly­(N-(3-hydroxypropyl)­acrylamide) (pHPAA) brushes with shorter CSLs = 1–3 possessed a much stronger binding ability to more water molecules than a poly­(N-(5-hydroxypentyl)­acrylamide) (pHPenAA) brush with CSL = 5. Consequently, CSL-induced strong surface hydration on pHMAA, pHEAA, and pHPAA brushes led to high surface resistance to lysozyme adsorption, in sharp contrast to lysozyme adsorption on the pHPenAA brush. Computational studies confirmed the experimental results of surface wettability and protein adsorption from surface plasmon resonance, contact angle, and sum frequency generation vibrational spectroscopy, highlighting that small structural variation of CSLs can greatly impact surface hydration and antifouling characteristics of antifouling surfaces, which may provide structural-based design guidelines for new and effective antifouling materials and surfaces.

Adsorption of Mussel Protein on Polymer Antifouling Membranes: A Molecular Dynamics Study

“…The longer the relaxation time is, the stronger the binding ability of antifouling membrane to water molecules is and representing the better antifouling effect. Its value can be obtained by fitting autocorrelation function [ 28 , 29 , 30 ]: where represents a binary operator, if the target molecule j remains in the initial range at time t , then , if not, then . is the total number of target molecules in the initial range defined by us, < > represents ensemble average.…”

Combinatorial Polyacrylamide Hydrogels for Preventing Biofouling on Implantable Biosensors

“…These prior studies have shown that surface density of grafted polymers resists adherence and that steric repulsion is leads to antifouling properties by blocking preventing protein adsorption sites [57][58][59] . Numerous other computational and molecular dynamics studies have shown that entropic contributions play a role in preventing biofouling 60,61 , wherein reduction in ligand mobility would lead to an entropic penalty against protein adsorption 62 Curiously, the composition of the top performing hydrogel formulations that yielded the lowest degree of platelet adhesion did not exhibit any intuitive trends, and so we utilized machinelearning analysis to identify mechanistic factors underpinning anti-biofouling activity. We first classified the copolymer hydrogels as "low platelet count" or "high platelet count" with a random forest model, which offers robustness to overfitting and the capability to evaluate relevance of data features via mean decrease of accuracy (MDA) (see Methods for technical details).…”

“…Numerous other computational and molecular dynamics studies have shown that entropic contributions play a role in preventing biofouling 63,64 , wherein reduction in ligand mobility would lead to an entropic penalty against protein adsorption 65 . Penna et al have identified the importance of ligand mobility and interfacial dynamics, highlighting a balance of hydration properties and a dynamic ligand layer that greatly affects entropic barriers associated with antifouling efficacy 66 .…”

“…Molecular simulations have also suggested that anti-biofouling properties may arise from steric repulsion of proteins and polymer surfaces - that the density of grafted polymer chains simply causes resistance to protein adhesion and obstructs their adsorption to the surface 17,60–62 . Numerous other computational and molecular dynamics studies have shown that entropic contributions play a role in preventing biofouling 63,64 , wherein reduction in ligand mobility would lead to an entropic penalty against protein adsorption 65 . Penna et al .…”

Anti-Biofouling Polymers with Special Surface Wettability for Biomedical Applications

“…As shown in Figure 1 , biofouling usually begins with a surface film formed by organic molecules, to which different foulants attach, resulting in mixed communities that may undergo long-term changes over long periods of time ( Rosenhahn et al, 2010 ). The presence of biofouling has significant impacts in various fields, including ships’ hulls, water pipes, biosensors, filters, and in the biomedical field where it contaminates applications such as surgical products, sutures, and dressings ( Liu et al, 2020a ).…”