Preparation, Properties, and Bioapplications of Block Copolymer Nanopatterns

Block copolymer (BCP) self-assembly has emerged as a feasible method for large-scale fabrication with remarkable precision - features that are not common for most of the nanofabrication techniques. In this review, recent advancements in the molecular design of BCP along with state-of-the-art processing methodologies based on microphase separation alone or its combination with different lithography methods are presented. Furthermore, the bioapplications of the generated nanopatterns in the development of protein arrays, cell-selective surfaces, and antibacterial coatings are explored. Finally, the current challenges in the field are outlined and the potential breakthroughs that can be achieved by adopting BCP approaches already applied in the fabrication of electronic devices are discussed.

Enhancing the Activity of Surface Immobilized Antimicrobial Peptides Using Thiol-Mediated Tethering to Poly(ethylene glycol)

Considering the need for versatile surface coatings that can display multiple bioactive signals and chemistries, the use of more novel surface modification methods is starting to emerge. Thiol-mediated conjugation of biomolecules is shown to be quite advantageous for such purposes due to the reactivity and chemoselectivity of thiol functional groups. Herein, the immobilization of poly(ethylene glycol) (PEG) and antimicrobial peptides (AMPs) to silica colloidal particles based on thiol-mediated conjugation techniques, along with an assessment of the antimicrobial potential of the functionalized particles against Pseudomonas aeruginosa and Staphylococcus aureus is investigated. Immobilization of PEG to thiolated Si particles is performed by either a two-step thiol-ene "photo-click" reaction or a "one-pot" thiol-maleimide type conjugation using terminal acrylate or maleimide functional groups, respectively. It is demonstrated that both immobilization methods result in a significant reduction in the number of viable bacterial cells compared to unmodified samples after the designated incubation periods with the PEG-AMP-modified colloidal suspensions. These findings provide a promising outlook for the fabrication of multifunctional surfaces based upon the tethering of PEG and AMPs to colloidal particles through thiol-mediated biocompatible chemistry, which has potential for use as implant coatings or as antibacterial formulations that can be incorporated into wound dressings to prevent or control bacterial infections.

Antithrombotic and hemocompatible properties of nanostructured coatings assembled from block copolymers

We describe the antithrombotic properties of nanopatterned coatings created by self-assembly of poly(styrene-block-2-vinylpyridine) (PS-b-P2VP) with different molecular weights. By changing the assembly conditions, we obtained nanopatterns that differ by their morphology (size and shape of the nanopattern) and chemistry. The surface exposition of P2VP block allowed quaternization, i.e. introduction of positive surface charge and following electrostatic deposition of heparin. Proteins (albumin and fibrinogen) adsorption, platelet adhesion and activation, cytocompatibility, and reendothelization capacity of the coatings were assessed and discussed in a function of the nanopattern morphology and chemistry. We found that quaternization results in excellent antithrombotic and hemocompatible properties comparable to heparinization by hampering the fibrinogen adhesion and platelet activation. In the case of quaternization, this effect depends on the size of the polymer blocks, while all heparinized patterns had similar performance showing that heparin surface coverage of 40 % is enough to improve substantially the hemocompatibility.

Diblock Polymer Brush (PHEAA- b-PFMA): Microphase Separation Behavior and Anti-Protein Adsorption Performance

In this paper, a series of amphiphilic diblock polymers of poly(hydroxyethylacrylamide)- b-poly(1H,1H-pentafluoropropyl methacrylate) (PHEAA- b-PFMA) were grafted from silicon wafer via surface-initiated atom transfer radical polymerization (SI-ATRP). Surface wettability and chemical compositions of the modified surfaces were characterized by contact angle goniometer and X-ray photoelectron spectroscopy (XPS) respectively. Molecular weight and polydispersity of each block were measured using gel permeation chromatography (GPC). The topography and the microphase separation behavior of PHEAA- b-PFMA surfaces were investigated by atomic force microscope (AFM). The results show that only when the grafting density (σ) and thickness of PHEAA brush were in the range of 0.9-1.3 (chain/nm²) and 6.6-15.1 nm, respectively, and the ratio of PFMA/PHEAA varied from 89/42 to 89/94, could the diblock copolymer phase separate into nanostructures. Further, the antiprotein adsorption performance of the modified surfaces against BSA, fibrinogen, and lysozyme was studied. The results indicated the modified surfaces could reduce the protein adsorption compared to the pristine silicon wafer. For Fibrinogen, the antiadsorption effect of PHEAA- b-PFMA-modified surfaces with microphase segregation was better than that of corresponding PHEAA modified surfaces. The results provide further evidence that surface composition and microphase segregation of fluorinated moieties of block copolymer brushes significantly impact protein adsorption behaviors.

Recent advances in RAFT-mediated surfactant-free emulsion polymerization

We summarized the RAFT-mediated surfactant-free emulsion polymerization using various RAFT agents and the polymerization types for the preparation of organic/inorganic hybrid materials.

Hybrid Hairy Janus Particles as Building Blocks for Antibiofouling Surfaces

Herein, we report a new strategy for the design of antifouling surfaces by using hybrid hairy Janus particles. The amphiphilic Janus particles possess either a spherical or a plateletlike shape and have core-shell structures with an inorganic core and hydrophilic/hydrophobic polymeric shells. Subsequently, these bifunctional Janus particles enable the fabrication of surfaces with modularity in chemical composition and final surface topography, which possess antifouling properties. The antifouling and fouling-release capability of the composite Janus particle-based surfaces is investigated using the marine biofilm-forming bacteria Cobetia marina. The Janus particle-based coatings are robust and significantly reduce bacterial retention under both static and dynamic conditions independent of the particle geometry. The plateletlike (kaolinite-based) Janus particles represent a scalable system for the rational design of antifouling coatings as well as their large-scale production and application in the future.

Heterogeneous surfaces to repel proteins

The nonspecific adsorption of proteins is usually undesirable on solid surfaces as it induces adverse responses, such as platelet adhesion on medical devices, negative signals of biosensors and contamination blockage of filtration membranes. Thus, an important scheme in material science is to design and fabricate protein-repulsive surfaces. Early approaches in this field focused on homogeneous surfaces comprised of single type functionality. Yet, recent researches have demonstrated that surfaces with heterogeneities (chemistry and topography) show promising performance against protein adsorption. In this review, we will summarize the recent achievements and discuss the new perspectives in the research of developing and characterizing heterogeneous surfaces to repel proteins. The protein repulsion mechanisms of different heterogeneous surfaces will also be discussed in details, followed by the perspective and challenge of this emerging field.