Strong resistance of oligo(phosphorylcholine) self-assembled monolayers to protein adsorption

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.

Modeling Polyzwitterion-Based Drug Delivery Platforms: A Perspective of the Current State-of-the-Art and Beyond

Drug delivery platforms are anticipated to have biocompatible and bioinert surfaces. PEGylation of drug carriers is the most approved method since it improves water solubility and colloid stability and decreases the drug vehicles' interactions with blood components. Although this approach extends their biocompatibility, biorecognition mechanisms prevent them from biodistribution and thus efficient drug transfer. Recent studies have shown (poly)zwitterions to be alternatives for PEG with superior biocompatibility. (Poly)zwitterions are super hydrophilic, mainly stimuli-responsive, easy to functionalize and they display an extremely low protein adsorption and long biodistribution time. These unique characteristics make them already promising candidates as drug delivery carriers. Furthermore, since they have highly dense charged groups with opposite signs, (poly)zwitterions are intensely hydrated under physiological conditions. This exceptional hydration potential makes them ideal for the design of therapeutic vehicles with antifouling capability, i.e., preventing undesired sorption of biologics from the human body in the drug delivery vehicle. Therefore, (poly)zwitterionic materials have been broadly applied in stimuli-responsive "intelligent" drug delivery systems as well as tumor-targeting carriers because of their excellent biocompatibility, low cytotoxicity, insignificant immunogenicity, high stability, and long circulation time. To tailor (poly)zwitterionic drug vehicles, an interpretation of the structural and stimuli-responsive behavior of this type of polymer is essential. To this end, a direct study of molecular-level interactions, orientations, configurations, and physicochemical properties of (poly)zwitterions is required, which can be achieved via molecular modeling, which has become an influential tool for discovering new materials and understanding diverse material phenomena. As the essential bridge between science and engineering, molecular simulations enable the fundamental understanding of the encapsulation and release behavior of intelligent drug-loaded (poly)zwitterion nanoparticles and can help us to systematically design their next generations. When combined with experiments, modeling can make quantitative predictions. This perspective article aims to illustrate key recent developments in (poly)zwitterion-based drug delivery systems. We summarize how to use predictive multiscale molecular modeling techniques to successfully boost the development of intelligent multifunctional (poly)zwitterions-based systems.

Biochemistry strategies for label-free optical sensor biofunctionalization: advances towards real applicability

Label-free biosensors, and especially those based on optical transducers like plasmonic or silicon photonic systems, have positioned themselves as potential alternatives for rapid and highly sensitive clinical diagnostics, on-site environmental monitoring, and for quality control in foods or other industrial applications, among others. However, most of the biosensor technology has not yet been transferred and implemented in commercial products. Among the several causes behind that, a major challenge is the lack of standardized protocols for sensor biofunctionalization. In this review, we summarize the most common methodologies for sensor surface chemical modification and bioreceptor immobilization, discussing their advantages and limitations in terms of analytical sensitivity and selectivity, reproducibility, and versatility. Special focus is placed on the suggestions of innovative strategies towards antifouling and biomimetic functional coatings to boost the applicability and reliability of optical biosensors in clinics and biomedicine. Finally, a brief overview of research directions in the area of device integration, automation, and multiplexing will give a glimpse of the future perspectives for label-free optical biosensors.

Unraveling the Mechanism and Kinetics of Binding of an LCI-eGFP-Polymer for Antifouling Coatings

The ability of proteins to adsorb irreversibly onto surfaces opens new possibilities to functionalize biological interfaces. Herein, the mechanism and kinetics of adsorption of protein-polymer macromolecules with the ability to equip surfaces with antifouling properties are investigated. These macromolecules consist of the liquid chromatography peak I peptide from which antifouling polymer brushes are grafted using single electron transfer-living radical polymerization. Surface plasmon resonance spectroscopy reveals an adsorption mechanism that follows a Langmuir-type of binding with a strong binding affinity to gold. X-ray reflectivity supports this by proving that the binding occurs exclusively by the peptide. However, the lateral organization at the surface is directed by the cylindrical eGFP. The antifouling functionality of the unimolecular coatings is confirmed by contact with blood plasma. All coatings reduce the fouling from blood plasma by 8894% with only minor effect of the degree of polymerization for the studied range (DP between 101 and 932). The excellent antifouling properties, combined with the ease of polymerization and the straightforward coating procedure make this a very promising antifouling concept for a multiplicity of applications.

Bioadhesion in the oral cavity and approaches for biofilm management by surface modifications

BACKGROUND

All soft and solid surface structures in the oral cavity are covered by the acquired pellicle followed by bacterial colonization. This applies for natural structures as well as for restorative or prosthetic materials; the adherent bacterial biofilm is associated among others with the development of caries, periodontal diseases, peri-implantitis, or denture-associated stomatitis. Accordingly, there is a considerable demand for novel materials and coatings that limit and modulate bacterial attachment and/or propagation of microorganisms.

OBJECTIVES AND FINDINGS

The present paper depicts the current knowledge on the impact of different physicochemical surface characteristics on bioadsorption in the oral cavity. Furthermore, it was carved out which strategies were developed in dental research and general surface science to inhibit bacterial colonization and to delay biofilm formation by low-fouling or "easy-to-clean" surfaces. These include the modulation of physicochemical properties such as periodic topographies, roughness, surface free energy, or hardness. In recent years, a large emphasis was laid on micro- and nanostructured surfaces and on liquid repellent superhydrophic as well as superhydrophilic interfaces. Materials incorporating mobile or bound nanoparticles promoting bacteriostatic or bacteriotoxic properties were also used. Recently, chemically textured interfaces gained increasing interest and could represent promising solutions for innovative antibioadhesion interfaces. Due to the unique conditions in the oral cavity, mainly in vivo or in situ studies were considered in the review.

CONCLUSION

Despite many promising approaches for modulation of biofilm formation in the oral cavity, the ubiquitous phenomenon of bioadsorption and adhesion pellicle formation in the challenging oral milieu masks surface properties and therewith hampers low-fouling strategies.

CLINICAL RELEVANCE

Improved dental materials and surface coatings with easy-to-clean properties have the potential to improve oral health, but extensive and systematic research is required in this field to develop biocompatible and effective substances.

Interface of Phospholipid Polymer Grafting Layers to Analyze Functions of Immobilized Oligopeptides Involved in Cell Adhesion

The aim of this study was to design a material surface for use in the analysis of the behavior of biomolecules at the interface of direct cell contact. A superhydrophilic surface was prepared with poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), which was grafted onto a substrate with controlled polymer chain density. An arginine-glycine-aspartic acid (RGD) peptide was immobilized at the surface of the polymer graft surface (PMPC-RGD surface). Initial adhesion of the cells to this substrate was observed. The PMPC-RGD surface could enable cell adhesion only through RGD peptide-integrin interactions. The density and movability of the RGD peptide at the terminal of the graft PMPC chain and the orientation of the RGD peptide affected the density of adherent cells. Thus, the PMPC graft surface may be a good candidate for a new platform with the ability to immobilize biomolecules to a defined position and enable accurate analysis of their effects on cells.

Computational Investigation of Antifouling Property of Polyacrylamide Brushes

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.

Preparation and Properties of a Low Fouling Magnetic Nanoparticle and Its Application to the HPV Genotypes Assay in Whole Serum

Gold magnetic particles as a new carrier of disease diagnosis probes have attracted wide attention but encountered a bottleneck. That is, the interfacial properties of gold magnetic particles are susceptible to the influence of nonspecific biological molecules in actual diagnostic samples. Here, a novel nanoparticle made by the covalent attachment of polyethyleneimine and hyperbranched polyether polyol onto the gold shell surface of a magnetic bead demonstrated not only low fouling properties but also excellent stability in a variety of external environments, especially in complex biological systems. Most importantly, in its application as the probe for sensitive and selective fluorescence detection of high-risk human papillomavirus (HPV) genotypes 18, 16 in buffer, even in 100% serum, a good linear correlation with the concentration of HPV_18/16 target DNA ranging from 5 nM to 1 μM was shown with the low detection limits. To our knowledge, this is one of the few successful examples of direct application of magnetic beads to the detection of disease markers in whole serum, suggesting that this material has good commercial potential and value.

Designs of Zwitterionic Interfaces and Membranes

Zwitterionic materials are the latest generation of materials for nonfouling interfaces and membranes. They outperform poly(ethylene glycol) derivatives because they form tighter bonds with water molecules and can trap more water molecules. This feature article summarizes our laboratory's fundamental developments related to the functionalization of interfaces and membranes using zwitterionic materials. Our molecular designs of zwitterionic polymers and copolymers, sulfobetaine-based, carboxybetaine-based, or phosphobetaine-based, are first reviewed. Then, the strategies used to functionalize surfaces/membranes by coating, grafting onto, grafting from, or in situ modification are examined and discussed, and the third part of this article shifts the focus to key applications of zwitterionic materials. Finally, some potential future directions for molecular designs, functionalization processes, and applications are presented.

Molecular Design of Zwitterionic Polymer Interfaces: Searching for the Difference

The widespread occurrence of zwitterionic compounds in nature has incited their frequent use in designing biomimetic materials. Therefore, zwitterionic polymers are a thriving field. A particular interest for this particular polymer class has currently focused on their use in establishing neutral, low-fouling surfaces. After highlighting strategies to prepare model zwitterionic surfaces as well as those that are more suitable for practical purposes relying strongly on radical polymerization methods, we present recent efforts to diversify the structure of the hitherto quite limited variety of zwitterionic monomers and of the derived polymers. We identify key structural variables, consider their influence on essential properties such as overall hydrophilicity and long-term stability, and discuss promising targets for the synthesis of new variants.

Charge reversal and swelling in saccharide binding polyzwitterionic phenylboronic acid-modified poly(4-vinylpyridine) nanoparticles

We present the synthesis and characterization of zwitterionic poly(4-vinylpyridine) nanoparticles quaternized with phenylboronic acid (QxPVP-PBA) whose size and surface charge can be tuned by varying the saccharide and the degree of quaternization.

Sterilization effects on ultrathin film polymer coatings for silicon-based implantable medical devices

Novel biomaterials for medical device applications must be stable throughout all stages of preparation for surgery, including sterilization. There is a paucity of information on the effects of sterilization on sub-10 nm-thick polymeric surface coatings suitable for silicon-based bioartificial organs. This study explores the effect of five standard sterilization methods on three surface coatings applied to silicon: polyethylene glycol (PEG), poly(sulfobetaine methacrylate) (pSBMA), and poly (2-methacryloyloxyethyl phosphorylcholine) (pMPC). Autoclave, dry heat, hydrogen peroxide (H2 O2 ) plasma, ethylene oxide gas (EtO), and electron beam (E-beam) treated coatings were analyzed to determine possible polymer degradation with sterilization. Poststerilization, there were significant alterations in contact angle, maximum change resulting from H2 O2 (Δ - 14°), autoclave (Δ + 15°), and dry heat (Δ + 23°) treatments for PEG, pSBMA, and pMPC, respectively. Less than 5% coating thickness change was found with autoclave and EtO on PEG-silicon, E-beam on pSBMA-silicon and EtO treatment on pMPC-silicon. H2 O2 treatment resulted in at least 30% decrease in thickness for all coatings. Enzyme-linked immunosorbent assays showed significant protein adsorption increase for pMPC-silicon following all sterilization methods. E-beam on PEG-silicon and dry-heat treatment on pSBMA-silicon exhibited maximum protein adsorption in each coating subset. Overall, the data suggest autoclave and EtO treatments are well-suited for PEG-silicon, while E-beam is best suited for pSBMA-silicon. pMPC-silicon was least impacted by EtO treatment. H2 O2 treatment had a negative effect on all three coatings. These results can be used to determine which surface modifications and sterilization processes to utilize for devices in vivo. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2327-2336, 2018.

Impact of Anti-Biofouling Surface Coatings on the Properties of Nanomaterials and Their Biomedical Applications

Understanding and subsequently controlling non-specific interactions between engineered nanomaterials and biological environment have become increasingly important for further developing and advancing nanotechnology for biomedical applications. Such non-specific interactions, also known as the biofouling effect, mainly associate with the adsorption of biomolecules (such as proteins, DNAs, RNAs, and peptides) onto the surface of nanomaterials and the adhesion or uptake of nanomaterials by various cells. By altering the surface properties of nanomaterials the biofouling effect can lead to in situ changes of physicochemical properties, pharmacokinetics, functions, and toxicity of nanomaterials. This review provides discussions on the current understanding of the biofouling effect, the factors that affect the non-specific interactions associated with biofouling, and the impact of the biofouling effect on the performances and functions of nanomaterials. An overview of the development and applications of various anti-biofouling coating materials to preserve and improve the properties and functions of engineered nanomaterials for intended biomedical applications is also provided.

Improved antifouling properties of photobioreactors by surface grafted sulfobetaine polymers

To improve the antifouling (AF) properties of photobioreactors (PBR) for microalgal cultivation, using trihydroxymethyl aminomethane (tris) as the linking agent, a series of polyethylene (PE) films grafted with sulfobetaine (PE-SBMA) with grafting density ranging from 23.11 to 112 μg cm^-2 were prepared through surface-initiated atom transfer radical polymerization (SI-ATRP). It was found that the contact angle of PE-SBMA films decreased with the increase in the grafting density. When the grafting density was 101.33 μg cm^-2, it reached 67.27°. Compared with the PE film, the adsorption of protein on the PE-SBMA film decreased by 79.84% and the total weight of solid and absorbed microalgae decreased by 54.58 and 81.69%, respectively. Moreover, the transmittance of PE-SBMA film recovered to 86.03% of the initial value after cleaning, while that of the PE film recovered to only 47.27%. The results demonstrate that the AF properties of PE films were greatly improved on polySBMA-grafted surfaces.

Properties of modified surface for biosensing interface

Properties of modified surface, behavior against salting-out effect, suppressive effect for protein nonspecific adsorption, and wettability were examined using various mercapto compounds bearing methyloligoethylene glycol, oligoethylene glycol, alkyl oligoethylene glycol, alkyl phosphoryl choline, alkyl inverse phosphoryl choline, and alkyl sulfobetaine moieties. The behavior against salting-out effect was examined using gold nanoparticle with PBS and NaCl aqueous solution. The suppressive effect for protein nonspecific adsorption was evaluated by SPR, and the wettability was measured on the SPR chip. The gold nanoparticle modified with 8C3EG, 12C4EG, 12CPC, 6CCP, and 12CCP showed excellent behavior against salting-out effect. The suppression of protein nonspecific adsorption was effective with 6EG, 12C4EG, 12CPC, and 12CS. On the other hand, the modified surface possessed high wettability except for the surface modified with M6EG. The results indicate that incorporation of alkyl group into surface modification materials is effective for the enhancement of behavior against salting-out effect and suppressive effect for protein nonspecific adsorption regardless of wettability. Among the zwitter ionic derivatives, inverse phosphoryl choline derivatives showed intriguing properties, high behavior against salting-out effect with high wettability but low suppressive effect for protein nonspecific adsorption.

Magnetic Nanoparticle Facilitated Drug Delivery for Cancer Therapy with Targeted and Image-Guided Approaches

With rapid advances in nanomedicine, magnetic nanoparticles (MNPs) have emerged as a promising theranostic tool in biomedical applications, including diagnostic imaging, drug delivery and novel therapeutics. Significant preclinical and clinical research has explored their functionalization, targeted delivery, controllable drug release and image-guided capabilities. To further develop MNPs for theranostic applications and clinical translation in the future, we attempt to provide an overview of the recent advances in the development and application of MNPs for drug delivery, specifically focusing on the topics concerning the importance of biomarker targeting for personalized therapy and the unique magnetic and contrast-enhancing properties of theranostic MNPs that enable image-guided delivery. The common strategies and considerations to produce theranostic MNPs and incorporate payload drugs into MNP carriers are described. The notable examples are presented to demonstrate the advantages of MNPs in specific targeting and delivering under image guidance. Furthermore, current understanding of delivery mechanisms and challenges to achieve efficient therapeutic efficacy or diagnostic capability using MNP-based nanomedicine are discussed.

Strategies To Achieve Control over the Surface Ratio of Two Different Components on Modified Electrodes Using Aryldiazonium Salts

Controlling the composition of an interface is very important in tuning the chemical and physical properties of a surface in many applications including biosensors, biomaterials, and chemical catalysis. Frequently, this requires one molecular component to a minor component in a mixed layer. Such subtle control of composition has been difficult to achieve using aryldiazonium salts. Herein, aryldiazonium salts of carboxyphenyl (CP) and phenylphosphorylcholine (PPC), generated in situ from their corresponding anilines, are electrografted to form molecular platform that are available for further functionalization. These two components are chosen because CP provides a convenient functionality for further coupling of biorecognition species while PPC offers resistance to nonspecific adsorption of proteins to the surface. Mixed layers of CP and PPC were prepared by grafting them either simultaneously or consecutively. The latter strategy allows an interface to be developed in a controlled way where one component is at levels of less than 1% of the total layer.

Synthesis of catechol and zwitterion-bifunctionalized poly(ethylene glycol) for the construction of antifouling surfaces

Versatile antifouling coatings from catechol and zwitterion-bifunctionalized poly(ethylene glycol).

Non-covalent phosphorylcholine coating reduces protein adsorption and phagocytic uptake of microparticles

Phosphorylcholine co-polymer was assembled on model polystyrene microparticles through a simple, widely-applicable ethanol coating process. The coating rendered particles resistant to protein adsorption and phagocytosis by macrophages, making it useful for a range of biological applications.

Immunomagnetic nanoparticles based on a hydrophilic polymer coating for sensitive detection of Salmonella in raw milk by polymerase chain reaction

The super hydrophilic poly(2-methacryloyloxyethyl phosphorylcholine (PMPC) coating could increase the capture performance of immunomagnetic nanoparticles effectively in the experimentally contaminated milk.

Probing the weak interaction of proteins with neutral and zwitterionic antifouling polymers

Protein-polymer interactions are of great interest in a wide range of scientific and technological applications. Neutral poly(ethylene glycol) (PEG) and zwitterionic poly(sulfobetaine methacrylate) (pSBMA) are two well-known nonfouling materials that exhibit strong surface resistance to proteins. However, it still remains unclear or unexplored how PEG and pSBMA interact with proteins in solution. In this work, we examine the interactions between two model proteins (bovine serum albumin and lysozyme) and two typical antifouling polymers of PEG and pSBMA in aqueous solution using fluorescence spectroscopy, atomic force microscopy and nuclear magnetic resonance. The effect of protein:polymer mass ratios on the interactions is also examined. Collective data clearly demonstrate the existence of weak hydrophobic interactions between PEG and proteins, while there are no detectable interactions between pSBMA and proteins. The elimination of protein interaction with pSBMA could be due to an enhanced surface hydration of zwitterionic groups in pSBMA. New evidence is given to demonstrate the interactions between PEG and proteins, which are often neglected in the literature because the PEG-protein interactions are weak and reversible, as well as the structural change caused by hydrophobic interaction. This work provides a better fundamental understanding of the intrinsic structure-activity relationship of polymers underlying polymer-protein interactions, which are important for designing new biomaterials for biosensor, medical diagnostics and drug delivery applications.

Design and fabrication of biosensing interface for waveguide-mode sensor

In order to develop a biosensing system with waveguide-mode sensor, fabrication of a biosensing interface on the silica surface of the sensing chip was carried out using triethoxysilane derivatives with anti-leptin antibody. Triethoxysilane derivatives bearing succinimide ester and oligoethylene glycol moieties were synthesized to immobilize the antibody and to suppress nonspecific adsorption of proteins, respectively. The chip modified with triethoxysilane derivatives bearing oligoethylene glycol moiety suppressed nonspecific adsorption of proteins derived from human serum effectively by rinse with PBS containing surfactant (0.05% Tween 20). On the other hand, it was confirmed that antibody was immobilized on the chip by immersion into antibody solution to show response of antigen-antibody reaction, where the chip was modified with triethoxysilane derivatives bearing succinimide ester moiety. When the interface was fabricated with antibody and a mixture of triethoxysilane derivatives bearing succinimide ester and oligoethylene glycol moieties, the response of antigen-antibody reaction depended on composition of the mixture and enhanced with the increase of ratio for triethoxysilane derivatives bearing succinimide ester moiety reflecting the antibody concentration immobilized on the chip. While introduction of excess triethoxysilane derivatives bearing succinimide ester moiety induced nonspecific adsorption of proteins derived from human serum, the immobilized antibody on the chip kept its activity after 1-month storage in a refrigerator. Taking into consideration those factors, the biosensing interface was fabricated using triethoxysilane derivatives with anti-leptin antibody to examine performance of the waveguide-mode sensor. It was found that the detection limits for human leptin were 50 ng/mL in PBS and 100 ng/mL in human serum. The results demonstrate that the waveguide-mode sensor powered by the biosensing interface fabricated with those triethoxysilane derivatives and antibody has potential to detect several tens of nanograms per milliliter of biomarkers in human serum with an unlabeled detection method.

Ultrasensitive impedimetric lectin biosensors with efficient antifouling properties applied in glycoprofiling of human serum samples

Ultrasensitive impedimetric lectin biosensors recognizing different glycan entities on serum glycoproteins were constructed. Lectins were immobilized on a novel mixed self-assembled monolayer containing 11-mercaptoundecanoic acid for covalent immobilization of lectins and betaine terminated thiol to resist nonspecific interactions. Construction of biosensors based on Concanavalin A (Con A), Sambucus nigra agglutinin type I (SNA), and Ricinus communis agglutinin (RCA) on polycrystalline gold electrodes was optimized and characterized with a battery of tools including electrochemical impedance spectroscopy, various electrochemical techniques, quartz crystal microbalance (QCM), Fourier transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) and compared with a protein/lectin microarray. The lectin biosensors were able to detect glycoproteins from 1 fM (Con A), 10 fM (Ricinus communis agglutinin (RCA), or 100 fM (SNA) with a linear range spanning 6 (SNA), 7 (RCA), or 8 (Con A) orders of magnitude. Furthermore, a detection limit for the Con A biosensor down to 1 aM was achieved in a sandwich configuration. A nonspecific binding of proteins for the Con A biosensor was only 6.1% (probed with an oxidized invertase) of the signal toward its analyte invertase and a negligible nonspecific interaction of the Con A biosensor was observed in diluted human sera (1000×), as well. The performance of the lectin biosensors was finally tested by glycoprofiling of human serum samples from healthy individuals and those having rheumatoid arthritis, which resulted in a distinct glycan pattern between these two groups.

Synthesis of agarose-graft-poly[3-dimethyl (methacryloyloxyethyl) ammonium propanesulfonate] zwitterionic graft copolymers via ATRP and their thermally-induced aggregation behavior in aqueous media

A novel polysaccharide-based zwitterionic copolymer, agarose-graft-poly[3-dimethyl (methacryloyloxyethyl) ammonium propanesulfonate] (agarose-g-PDMAPS) with UCST, depending both on hydrogen bonding and electrostatic interaction, was synthesized by ATRP, and its aggregation behavior in aqueous media was investigated in detail. Proton nuclear magnetic resonance spectroscopy, Fourier transform-infrared spectroscopy, and gel-permeation chromatography were performed to characterize the copolymer. Thermosensitive behaviors of the copolymers in water, NaCl, and urea solution were tracked by ultraviolet, dynamic light scattering, and transmission electron microscopy analysis. It was found that the copolymers existed as "core-shell" spheres at an elevated temperature, as a result of the self-assembly of the agarose backbones located in the "core" driven by hydrogen-bonding interactions. When the copolymer solution was cooled below UCST, the core-shell spheres began to aggregate because of the electrostatic interactions and collapse of PDMAPS side chains in the "shell" layer. UCST of the copolymer could be tuned in a wide range, depending on the chain lengths of PDMAPS. This is the first example to investigate the thermosensitivity, combining ionic interactions of the zwitterionic side chains with hydrogen bondings from the biocompatible agarose backbones. The synthetic strategy presented here can be employed in the preparation of other novel biomaterials from a variety of polysaccharides.

Layer by layer self-assembly of poly[2-(methacryloyloxy) ethyl phosphorylcholine] multilayer via the ionic complexation with zirconium

Zirconium-phosphonate (Zr-P) ionic complexation chemistry is explored as a new approach to fabricate poly[2-(methacryloyloxy) ethyl phosphorylcholine] (PMPC) multilayer film by layer-by-layer self-assembly method. Quartz crystal microbalance with dissipation (QCM-D) and optical ellipsometry measurements demonstrated that PMPC layer can be fully absorbed on each Zr(4+) layer. The thickness of the multilayer film with a good linear relationship was followed by the ellipsometry in situ adlayer characterization. The influence of pH of the PMPC and Zr(4+) solutions on the multilayer deposition were investigated by optical ellipsometry. QCM-D results indicated that the multilayer film is stable in a PBS flowing chamber at a high flow rate of 5.2×10(-3)m/s. The ellipsometry data demonstrated that 67.2% of the film still remained on the silicon wafer after being strong shaken in PBS at 80 rpm for 12h. The adsorption of bovine serum albumin (BSA) and fetal bovine serum (FBS) on the PMPC surface was monitored by the QCM-D and spectroscopic ellipsometry, and the results showed the multilayer film have excellent protein resistance.

Resistance of galactoside-terminated alkanethiol self-assembled monolayers to marine fouling organisms

Self-assembled monolayers (SAMs) of galactoside-terminated alkanethiols have protein-resistance properties which can be tuned via the degree of methylation [Langmuir 2005, 21, 2971-2980]. Specifically, a partially methylated compound was more resistant to nonspecific protein adsorption than the hydroxylated or fully methylated counterparts. We investigate whether this also holds true for resistance to the attachment and adhesion of a range of marine species, in order to clarify to what extent resistance to protein adsorption correlates with the more complex adhesion of fouling organisms. The partially methylated galactoside-terminated SAM was further compared to a mixed monolayer of ω-substituted methyl- and hydroxyl-terminated alkanethiols with wetting properties and surface ratio of hydroxyl to methyl groups matching that of the galactoside. The settlement (initial attachment) and adhesion strength of four model marine fouling organisms were investigated, representing both micro- and macrofoulers; two bacteria (Cobetia marina and Marinobacter hydrocarbonoclasticus), barnacle cypris larvae (Balanus amphitrite), and algal zoospores (Ulva linza). The minimum in protein adsorption onto the partially methylated galactoside surface was partly reproduced in the marine fouling assays, providing some support for a relationship between protein resistance and adhesion of marine fouling organisms. The mixed alkanethiol SAM, which was matched in wettability to the partially methylated galactoside SAM, consistently showed higher settlement (initial attachment) of test organisms than the galactoside, implying that both wettability and surface chemistry are insufficient to explain differences in fouling resistance. We suggest that differences in the structure of interfacial water may explain the variation in adhesion to these SAMs.

Antifouling coatings: recent developments in the design of surfaces that prevent fouling by proteins, bacteria, and marine organisms

The major strategies for designing surfaces that prevent fouling due to proteins, bacteria, and marine organisms are reviewed. Biofouling is of great concern in numerous applications ranging from biosensors to biomedical implants and devices, and from food packaging to industrial and marine equipment. The two major approaches to combat surface fouling are based on either preventing biofoulants from attaching or degrading them. One of the key strategies for imparting adhesion resistance involves the functionalization of surfaces with poly(ethylene glycol) (PEG) or oligo(ethylene glycol). Several alternatives to PEG-based coatings have also been designed over the past decade. While protein-resistant coatings may also resist bacterial attachment and subsequent biofilm formation, in order to overcome the fouling-mediated risk of bacterial infection it is highly desirable to design coatings that are bactericidal. Traditional techniques involve the design of coatings that release biocidal agents, including antibiotics, quaternary ammonium salts (QAS), and silver, into the surrounding aqueous environment. However, the emergence of antibiotic- and silver-resistant pathogenic strains has necessitated the development of alternative strategies. Therefore, other techniques based on the use of polycations, enzymes, nanomaterials, and photoactive agents are being investigated. With regard to marine antifouling coatings, restrictions on the use of biocide-releasing coatings have made the generation of nontoxic antifouling surfaces more important. While considerable progress has been made in the design of antifouling coatings, ongoing research in this area should result in the development of even better antifouling materials in the future.

Preparation of amphiphilic polymer-functionalized carbon nanotubes for low-protein-adsorption surfaces and protein-resistant membranes

Multiwalled carbon nanotubes functionalized with poly(sulfone) (PSF) and poly(sulfobetaine methacrylate) (PSBMA) (MWNT-PSF/PSBMA) have been prepared through sequential atom transfer radical polymerization. The structure of MWNT-PSF/PSBMA hybrid has been characterized with FTIR, Raman spectroscopy, and high-resolution transmission electron microscopy. Incorporation of PSBMA chains to MWNTs introduces amphiphilic and protein-resistant properties to MWNT-PSF/PSBMA. Addition of 1 wt % MWNT-PSF/PSBMA to PSF films significantly improves their protein-resistant characteristic, as the composite films show a 4.4% of protein adsorption compared to poly(styrene) Petri dishes. The PSF/MWNT-PSF/PSBMA composite has been applied to prepare antifouling ultrafiltration membranes for protein separation. This work demonstrates an effective and convenient approach to prepare low-protein-adsorption surfaces and antifouling membranes.