Interfacial Assembly Inspired by Marine Mussels and Antifouling Effects of Polypeptoids: A Neutron Reflection Study

Abstract

Polypeptoid-coated surfaces and many surface-grafted hydrophilic polymer brushes have been proven efficient in antifouling-the prevention of nonspecific biomolecular adsorption and cell attachment. Protein adsorption, in particular, is known to mediate subsequent cell-surface interactions. However, the detailed antifouling mechanism of polypeptoid and other polymer brush coatings at the molecular level is not well understood. Moreover, most adsorption studies focus only on measuring a single adsorbed mass value, and few techniques are capable of characterizing the hydrated in situ layer structure of either the antifouling coating or adsorbed proteins. In this study, interfacial assembly of polypeptoid brushes with different chain lengths has been investigated in situ using neutron reflection (NR). Consistent with past simulation results, NR revealed a common two-step structure for grafted polypeptoids consisting of a dense inner region that included a mussel adhesive-inspired oligopeptide for grafting polypeptoid chains and a highly hydrated upper region with very low polymer density (molecular brush). Protein adsorption was studied with human serum albumin (HSA) and fibrinogen (FIB), two common serum proteins of different sizes but similar isoelectric points (IEPs). In contrast to controls, we observed higher resistance by grafted polypeptoid against adsorption of the larger FIB, especially for longer chain lengths. Changing the pH to close to the IEPs of the proteins, which generally promotes adsorption, also did not significantly affect the antifouling effect against FIB, which was corroborated by atomic force microscopy imaging. Moreover, NR enabled characterization of the in situ hydrated layer structures of the polypeptoids together with proteins adsorbed under selected conditions. While adsorption on bare SiO 2 controls resulted in surface-induced protein denaturation, this was not observed on polypeptoids. Our current results therefore highlight the detailed in situ view that NR may provide for characterizing protein adsorption on polymer brushes as well as the excellent antifouling behavior of polypeptoids.

Preparation and Antifouling Property of Polyurethane Film Modified by PHMG and HA Using Layer-by-Layer Assembly

“…Adsorption of protein on the surface works as the initial step of biofouling when implanted in vivo and further compromises the surface properties, promotes cell attachment, and initiates the final foreign body response [ 46 , 47 ]. Thus, the resistance to protein adsorption of PU films is first taken into consideration.…”

Effects of Ionic Strength on the Morphology, Scattering, and Mechanical Response of Neurofilament-Derived Protein Brushes

“…Neurofilaments (NFs) are cylindrical, self-assembled protein filaments organized axially within the axon. Brushes consisting of intrinsically disordered proteins (IDPs) protrude out from the NF cores, which play a critical role in the stability, organization, and functionality of the neuron. , Mutations in the comprising proteins have also been linked to neurodegenerative diseases such as amyotrophic lateral sclerosis, Alzheimer’s disease, and Parkinson’s disease, in which the instability of the NFs may contribute to neuronal cell death. − Furthermore, protein-inspired brushes arouse great interest in practical applications because of their unique properties in biocompatibility, , sensitivity to external stimuli, , and ease of genetic modification . These advantages enable their wide application in biomedical devices and materials, such as sensors, − valves, , actuators, , artificial cartilage, and vehicles for drug/gene delivery …”

“…1,2 Mutations in the comprising proteins have also been linked to neurodegenerative diseases such as amyotrophic lateral sclerosis, Alzheimer's disease, and Parkinson's disease, in which the instability of the NFs may contribute to neuronal cell death. 3−5 Furthermore, protein-inspired brushes arouse great interest in practical applications because of their unique properties in biocompatibility, 6,7 sensitivity to external stimuli, 8,9 and ease of genetic modification. 10 These advantages enable their wide application in biomedical devices and materials, such as sensors, 11−13 valves, 14,15 actuators, 16,17 artificial cartilage, 18 and vehicles for drug/gene delivery.…”

Effect of Oil Polarity on the Protein Adsorption at Oil–Water Interfaces

“…The protein adsorption orientation and conformation , are largely affected by protein structures and the oil polarity . Recently, some experimental techniques have been used to characterize the orientation and conformation of the adsorbed proteins. , Neutron reflection could be used to determine the protein adsorption orientation; synchrotron radiation circular dichroism and Fourier transform infrared spectroscopy have identified secondary conformation changes; meanwhile, front-face tryptophan fluorescence spectroscopy has qualitatively discerned local rearrangements in the tertiary structure. However, detailed tertiary conformational information on individual adsorbed proteins is still lacking, with only the overall properties of a composite layer obtained by indirect methods .…”