Modular Design for Proteins Assembling into Antifouling Coatings: Case of Gold Surfaces

Multistep Self-Assembly of the Gold-Binding Peptide AuBP1

Solid-binding peptides have emerged as a distinct class of peptides, offering significant potential for biohybrid materials technologies due to their ability to bind selectively to a specific target material and integrate different materials with bioactive molecules and their ease of biochemical and genetic conjugation with proteins. Their vast applications span health and nonmedical applications including biocatalysis, biosensing, and agriculture, as well as sustainable engineering platforms. As these applications continue to expand, it is critical to understand the optimal performance conditions of these peptides and develop a fundamental understanding of the factors controlling their binding and surface organization that lead to self-assembled properties at the material interfaces. In this work, the self-assembly of one such peptide, AuBP1 (WAGAKRLVLRRE), was revisited through atomic force microscopy (AFM) studies conducted on a Au(111) surface to gain further insight into the assembly process. Peptide film coverage on the surface was monitored as a function of adsorption time (seconds to hours) and concentration of the peptide (1 fM to 10 μM). Our analysis reveals that initial isolated peptide binding is followed by assembly into a large-scale network of clustered peptides, slower filling of the remaining sites on the surface into a uniform film, and finally reorganization of the peptide film. Our observations suggest a multistep assembly process involving both peptide-peptide and peptide-surface interactions that cooperatively influence binding transitions. We compared noncooperative and semicooperative models, which provided additional insight into the growth phase of the peptide adsorption and assembly process. Understanding real-time binding kinetics and the boundary conditions that lead to robust self-assembled peptide films could extend the utilization of material-binding peptides into future technologies.

Probing Solid-Binding Peptide Self-Assembly Kinetics Using a Frequency Response Cooperativity Model

Biomolecular adsorption has great significance in medical, environmental, and technological processes. Understanding adsorption equilibrium and binding kinetics is essential for advanced process implementation. This requires identifying intrinsic determinants that predict optimal adsorption properties at bio-hybrid interfaces. Solid-binding peptides (SBPs) have targetable intrinsic properties involving peptide-peptide and peptide-solid interactions, which result in high-affinity material-selective binding. Atomic force microscopy investigations confirmed this complex interplay of multi-step peptide assemblies in a cooperative modus. Yet, most studies report adsorption properties of SBPs using non-cooperative or single-step adsorption models. Using non-cooperative kinetic models for predicting cooperative self-assembly behavior creates an oversimplified view of peptide adsorption, restricting implementing SBPs beyond their current use. To address these limitations and provide insight into surface-level events during self-assembly, a novel method, the Frequency Response Cooperativity model, was developed. This model iteratively fits adsorption data through spectral analysis of several time-dependent kinetic parameters. The model, applied to a widely used gold-binding peptide data obtained using a quartz crystal microbalance with dissipation, verified multi-step assembly. Peak deconvolution of spectral plots revealed distinct differences in the size and distribution of the kinetic rates present during adsorption across the concentrations. This approach provides new fundamental insights into the intricate dynamics of self-assembly of biomolecules on surfaces.

AB-Type Zwitterionic Hydrogel Paint

Zwitterionic hydrogels exhibit excellent nonfouling and hemocompatibility. However, the practical application of these materials as antifouling coatings for biomedical devices is hindered by several key challenges, including the harsh preparation conditions and the weak coating stability. Here, we present a two-component zwitterionic hydrogel paint for the in situ preparation of robust zwitterionic hydrogel coatings on various substrate surfaces without UV assistance. It is performed by the curing and adhesion of a zwitterionic hydrogel simultaneously through the ring opening reaction of epoxy and amino inspired by the successful commercial two-component epoxy structural glue. The obtained AB-type PSBMA coating can withstand water flow velocities of up to 15 m/s and still maintain its structural integrity and functional stability. It is noteworthy that the coating preparation process does not require the use of any organic solvent, which greatly simplifies the postprocessing steps for its application in medical devices. Moreover, the coating not only resists bacterial and cell adhesion but also exhibits favorable hemocompatibility. This approach offers a novel concept for the design of zwitterionic hydrogel coatings for biomedical devices.

Mitigating Membrane Biofouling in Protein Production with Zwitterionic Peptides

Biofouling on polymeric membranes poses a significant challenge in protein production and separation processes. We report here on the use of zwitterionic peptides composed of alternating lysine (K) and glutamic acid (E) residues to reduce biomolecular fouling on gold substrates and polymeric membranes within a protein production-mimicking environment. Our findings demonstrate that both gold chips and polymeric membranes functionalized with longer sequence zwitterionic peptides, along with a hydrophilic linker, exhibit superior antifouling performance across various protein-rich environments. Furthermore, increasing the grafting density of these peptides on substrates enhances their antifouling properties. We believe that this work sheds light on the antifouling capabilities of zwitterionic peptides in cell culture environments, advancing our understanding and paving the way for the development of zwitterionic peptide-based antifouling materials for polymeric membranes.

Protein-based bioactive coatings: from nanoarchitectonics to applications

Protein-based bioactive coatings have emerged as a versatile and promising strategy for enhancing the performance and biocompatibility of diverse biomedical materials and devices. Through surface modification, these coatings confer novel biofunctional attributes, rendering the material highly bioactive. Their widespread adoption across various domains in recent years underscores their importance. This review systematically elucidates the behavior of protein-based bioactive coatings in organisms and expounds on their underlying mechanisms. Furthermore, it highlights notable advancements in artificial synthesis methodologies and their functional applications in vitro. A focal point is the delineation of assembly strategies employed in crafting protein-based bioactive coatings, which provides a guide for their expansion and sustained implementation. Finally, the current trends, challenges, and future directions of protein-based bioactive coatings are discussed.