Active Protein-Functionalized Poly(poly(ethylene glycol) monomethacrylate)-Si(100) Hybrids from Surface-Initiated Atom Transfer Radical Polymerization for Potential Biological Applications

Peptide-Modified Surfaces for Binding Carbamylated Proteins from Plasma

Carbamylation of blood proteins is a common post-translational modification that occurs upon kidney dysfunction that is strongly associated with deleterious outcomes for patients treated using hemodialysis. In this study, we focused on the removal of two representative carbamylated plasma proteins, carbamylated albumin (cHSA) and fibrinogen (cFgn), through adsorption onto a surface functionalized with a specific peptide (cH2p1). Surfaces modified with poly(hydroxyethyl methacrylate) (p(HEMA)) were prepared using surface-initiated atom transfer radical polymerization (SI-ATRP) techniques and functionalized with cH2p1. cH2p1-functionalized surfaces showed selective binding toward cHSA and cFgn, compared to their native protein form, with NH-cH2p1 of superior selectivity than CO-cH2p1. The adsorption capacity of carbamylated protein on NH-cH2p1 was maintained in diluted plasma, and ultralow adsorption of native Fgn was observed. Similar to unmodified p(HEMA) surfaces, NH-cH2p1 showed a low platelet adhesion and activation, suggesting that the designed surface does not adversely affect platelets.

Polymer brush interfaces for protein biosensing prepared by surface-initiated controlled radical polymerization

This article discusses protein-binding polymer brushes and the various strategies that can be used to immobilize proteins on these films.

Antitumor activity of a folate receptor-targeted immunoglobulin G-doxorubicin conjugate

Development of antibody-drug conjugates (ADCs) is a promising therapeutic strategy for cancer therapy. In this study, folate was conjugated via a polyethyleneglycol (PEG) linker to immunoglobulin G (IgG), which was linked to doxorubicin (DOX), to form a novel ADC folate-PEG-IgG-DOX (FA-PEG-IgG-DOX). The FA-PEG-IgG-DOX showed high targeting efficiency in HeLa and KB cells and significantly improved the uptake and retention of DOX compared with IgG-DOX about 10-fold. Subsequently, FA-PEG-IgG-DOX was shown to have at least 8 times higher antitumor activity than IgG-DOX both in HeLa and KB cells and also induced more apoptosis in those cells than IgG-DOX. Moreover, FA-PEG-IgG-DOX had a 2 times longer circulating time than FA-IgG-DOX, but did not increase the DOX distribution in mouse hearts. Importantly, FA-PEG-IgG-DOX treatment significantly inhibited tumor growth in xenograft mice. Together, our results indicate that FA-PEG-IgG is an effective ADC carrier for delivery of chemotherapeutic agents and that conjugating tumor targeting ligands to antibodies is a promising strategy for producing ADC drugs.

Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ever increasing set of computational and simulation tools that allow understanding and predictions of these surface-grafted polymer architectures. The aim of this contribution is to provide a comprehensive review that critically assesses recent advances in the field and highlights the opportunities and challenges for future work.

Grafting of functional methacrylate polymer brushes by photoinduced SET-LRP

The growth of polymer brushes from a variety of methacrylate monomers was accomplished using UV light as a polymerization trigger.

Infection-resistant styrenic thermoplastic elastomers that can switch from bactericidal capability to anti-adhesion

Infection-resistant styrenic thermoplastic elastomers that can switch from bactericidal capability to anti-adhesion are facilely chloromethylated, followed by quaternization with methyl 3-(dimethylamino) propionate.

Fabrication of a photocontrolled surface with switchable wettability based on host-guest inclusion complexation and protein resistance

A novel surface-modification strategy has been developed for the construction of a photocontrolled silicon wafer surface with switchable wettability based on host-guest inclusion complexation. The silicon wafer was first modified by guest molecule azobenzene (Azo) via a silanization reaction. Subsequently, a series of polymers with different polarities were attached to host molecule β-cyclodextrin (β-CD) to prepare β-CD-containing hemitelechelic polymers via click chemistry. Finally, a photocontrolled silicon wafer surface modified with polymers was fabricated by inclusion complexation between β-CD and Azo, and the surface properties of the substrate are dependent on the polymers we used. The elemental composition, surface morphology, and hydrophilic/hydrophobic property of the modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscope, and contact angle measurements, respectively. The antifouling property of the PEG-functionalized surface was evaluated by a protein adsorption assay using bovine serum albumin, which was also characterized by XPS. The results demonstrate that the surface modified with PEG possesses good protein-resistant properties.

Fabricating a cycloolefin polymer immunoassay platform with a dual-function polymer brush via a surface-initiated photoiniferter-mediated polymerization strategy

The development of technologies for a biomedical detection platform is critical to meet the global challenges of various disease diagnoses. In this study, an inert cycloolefin polymer (COP) support was modified with two-layer polymer brushes possessing dual functions, i.e., a low fouling poly[poly(ethylene glycol) methacrylate] [p(PEGMA)] bottom layer and a poly(acrylic acid) (PAA) upper layer for antibody loading, via a surface-initiated photoiniferter-mediated polymerization strategy for fluorescence-based immunoassay. It was demonstrated through a confocal laser scanner that, for the as-prepared COP-g-PEG-b-PAA-IgG supports, nonspecific protein adsorption was suppressed, and the resistance to nonspecific protein interference on antigen recognition was significantly improved, relative to the COP-g-PAA-IgG references. This strategy for surface modification of a polymeric platform is also applicable to the fabrication of other biosensors.

Fabrication of a detection platform with boronic-acid-containing zwitterionic polymer brush

Development of technologies for biomedical detection platform is critical to meet the global challenges of various disease diagnoses, especially for point-of-use applications. Because of its natural simplicity, effectiveness, and easy repeatability, random covalent-binding technique is widely adopted in antibody immobilization. However, its antigen-binding capacity is relatively low when compared to site-specific immobilization of antibody. Herein, we report that a detection platform modified with boronic acid (BA)-containing sulfobetaine-based polymer brush. Mainly because of the advantage of oriented immobilization of antibody endowed with BA-containing three-dimensional polymer brush architecture, the platform had a high antigen-binding capacity. Notably, nonspecific protein adsorption was also suppressed by the zwitterionic pendants, thus greatly enhanced signal-to-noise (S/N) values for antigen recognition. Furthermore, antibodies captured by BA pendants could be released in dissociation media. This new platform is promising for potential applications in immunoassays.

Thin polymer brush decouples biomaterial's micro-/nanotopology and stem cell adhesion

Surface morphology and chemistry of polymers used as biomaterials, such as tissue engineering scaffolds, have a strong influence on the adhesion and behavior of human mesenchymal stem cells. Here we studied semicrystalline poly(ε-caprolactone) (PCL) substrate scaffolds, which exhibited a variation of surface morphologies and roughness originating from different spherulitic superstructures. Substrates were obtained by varying the parameters of the thermal processing, that is, crystallization conditions. The cells attached to these polymer substrates adopted different morphologies responding to variations in spherulite density and size. In order to decouple substrate topology effects on the cells, sub-100 nm bioadhesive polymer brush coatings of oligo(ethylene glycol) methacrylates were grafted from PCL and functionalized with fibronectin. On surfaces featuring different surface textures, dense and sub-100 nm thick brush coatings determined the response of cells, irrespective to the underlying topology. Thus, polymer brushes decouple substrate micro-/nanoscale surface topology and the adhesion of stem cells.

Crosslinked PEG mats for peptide immobilization and stem cell adhesion

We have designed a lightly crosslinked PEG based copolymer coating with compositional flexibility as well as extended stability for studying human mesenchymal stem cells (hMSCs). Copolymers contain a majority of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) as a cytophobic background with poly(ethylene glycol) methacrylate (PEGMA) for peptide coupling, and less than 10% glycidyl methacrylate (GMA) for crosslinking. Copolymer thin films were crosslinked into 30 nm thick mats by either thermal treatment or ultraviolet light and were stable for 35 days in water at 37 °C. The amount of PEGMA in the copolymer was optimized to ∼11% to minimize non-specific cell-protein interactions while maximizing the amount of total bound peptides. Following the binding of RGDSP to the mat, hMSCs were seeded. The hMSC adhesion, spreading and focal adhesion complex formation were promoted in a concentration dependent manner. Mats coupled with a non-adhesive scramble (RDGSP) maintained their cytophobicity. Competitive detachment experiments further demonstrated that cell adhesion was mediated by receptor binding to the RGDSP peptide. Cell culture experiments performed at 1 and 2 weeks show that mats can still resist cell adhesion after incubation in a serum containing medium. X-ray photoelectron spectroscopy (XPS) was effectively used to quantify the average total peptide concentration as 12.6 ± 6.14 pmol cm^-2. A square 2.2 mm N (1s) element map shows an average value of 17.9 pmol cm^-2 of RGDSP, which correlates well with the multipoint high resolution data. The stability of the copolymer, compositional flexibility, ease of application and the ability to precisely quantify bound peptides on the mats make these materials ideal for the study of cellular processes, where stability, functionality and topography of the biointerface are relevant.

Biomimetic anchors for antifouling and antibacterial polymer brushes on stainless steel

Barnacle cement (BC) was beneficially applied on stainless steel (SS) to serve as the initiator anchor for surface-initiated polymerization. The amine and hydroxyl moieties of barnacle cement reacted with 2-bromoisobutyryl bromide to provide the alkyl halide initiator for the surface-initiated atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate (HEMA). The hydroxyl groups of HEMA polymer (PHEMA) were then converted to carboxyl groups for coupling of chitosan (CS) to impart the SS surface with both antifouling and antibacterial properties. The surface-functionalized SS reduced bovine serum albumin adsorption, bacterial adhesion, and exhibited antibacterial efficacy against Escherichia coli (E. coli). The effectiveness of barnacle cement as an initiator anchor was compared to that of dopamine, a marine mussel inspired biomimetic anchor previously used in surface-initiated polymerization. The results indicate that the barnacle cement is a stable and effective anchor for functional surface coatings and polymer brushes.

Anti-fouling bioactive surfaces

Bioactive surfaces refer to surfaces with immobilized bioactive molecules aimed specifically at promoting or supporting particular interactions. Such surfaces are of great importance for various biomedical and biomaterials applications. In the past few years, considerable effort has been made to create bioactive surfaces by forming specific biomolecule-modified surfaces on a non-biofouling "base" or "background". Hydrophilic and bioinert polymers have been widely used as anti-fouling layers that resist non-specific protein interactions. They can also serve as "spacers" to effectively move the immobilized biomolecule away from the surface, thus enhancing its bioactivity. In this review we summarize several successful approaches for the design and preparation of bioactive surfaces based on different types of anti-fouling/spacer materials. Some perspectives on future research in this area are also presented.

Lysozyme-coupled poly(poly(ethylene glycol) methacrylate)-stainless steel hybrids and their antifouling and antibacterial surfaces

An environmentally benign approach to impart stainless steel (SS) surfaces with antifouling and antibacterial functionalities was described. Surface-initiated atom transfer radical polymerization (ATRP) of poly(ethylene glycol) monomethacrylate) (PEGMA) from the SS surface-coupled catecholic L-3,4-dihydroxyphenylalanine (DOPA) with terminal alkyl halide initiator was first carried out, followed by the immobilization of lysozyme at the chain ends of poly(ethylene glycol) branches of the grafted PEGMA polymer brushes. The functionalized SS surfaces were shown to be effective in preventing bovine serum albumin (BSA) adsorption and in reducing bacterial adhesion and biofilm formation. The surfaces also exhibited good bactericidal effects against Escherichia coli and Staphylococcus aureus. The concomitant incorporation of antifouling hydrophilic brushes and antibacterial enzymes or peptides onto metal surfaces via catecholic anchors should be readily adaptable to other metal substrates, and is potentially useful for biomedical and biomaterial applications.