Functionalization of Poly(oligo(ethylene glycol) methacrylate) Films on Gold and Si/SiO2 for Immobilization of Proteins and Cells: SPR and QCM Studies

Biorecognition antifouling coatings in complex biological fluids: a review of functionalization aspects

Recent progress in biointerface research has highlighted the role of antifouling functionalizable coatings in the development of advanced biosensors for point-of-care bioanalytical and biomedical applications dealing with real-world complex samples. The resistance to nonspecific adsorption promotes the biorecognition performance and overall increases the reliability and specificity of the analysis. However, the process of modification with biorecognition elements (so-called functionalization) may influence the resulting antifouling properties. The extent of these effects concerning both functionalization procedures potentially changing the surface architecture and properties, and the physicochemical properties of anchored biorecognition elements, remains unclear and has not been summarized in the literature yet. This critical review summarizes these key functionalization aspects with respect to diverse antifouling architectures showing low or ultra-low fouling quantitative characteristics in complex biological media such as bodily fluids or raw food samples. The subsequent discussion focuses on the impact of functionalization on fouling resistance. Furthermore, this review discusses some of the drawbacks of available surface sensitive characterization methods and highlights the importance of suitable assessment of the resistance to fouling.

Reversible Stimuli-Dependent Aggregation-Induced Emission from a "Nonfluorescent" Amphiphilic PVDF Graft Copolymer

A poly(vinylidine fluoride) graft random copolymer of t-butyl aminoethyl methacrylate (tBAEMA) and oligo(ethylene glycol) methyl ether methacrylate (OEGMA, Mn = 300) [PVDF-g-P(tBAEMA-ran-OEGMA), PVBO] is synthesized by atom transfer radical polymerization (ATRP), and PVBO is fractionated to get a highly water-soluble fraction (PVBO-1) showing a reversible on/off fluorescence behavior with gradual increase and decrease in pH, respectively, achieving a maximum quantum yield of 0.18 at pH = 12. PVBO-1 dissolved in water shows large multimicellar aggregates (MMcA), but at pH 12, crumbling of larger aggregates to much smaller micelles occurs, forming nonconjugated polymer dots (NCPDs), as supported by transmission electron microscopy and dynamic light scattering study. The reversible fluorescence on/off behavior also occurs with the decrease and increase of temperature. Theoretical study indicates that, at high pH, most of the amino groups become neutral and exhibit a strong tendency to form aggregates from crowding of a large number of carbonyl and amine groups, minimizing the HOMO-LUMO gap, showing an absorption peak at the visible region, and generating aggregation-induced emission.

Antifouling Coatings Generated from Unsymmetrical Partially Fluorinated Spiroalkanedithiols

Biofouling negatively impacts modern society on a daily basis, especially with regard to the important industries of medicine, oil, and shipping. This manuscript describes the preparation and study of model antifouling coatings generated from the adsorption of unsymmetrical partially fluorinated spiroalkanedithiols on gold. The antifouling properties of the self-assembled monolayers (SAMs) derived from the spiroalkanedithiols were compared to SAMs derived from analogous monodentate partially fluorinated and nonfluorinated alkanethiols. The antifouling properties were evaluated using in situ surface plasmon resonance spectroscopy (SPR), ex situ electrochemical quartz crystal microbalance (QCM) measurements, and ex situ ellipsometric thickness measurements. The resistance to nonspecific protein adsorption of the SAMs was evaluated with proteins having a wide range of properties and applications including protamine, lysozyme, bovine serum albumin, and fibrinogen. The results from the SPR and the QCM measurements demonstrated that in most cases, the SAM coatings derived from the partially fluorinated spiroalkanedithiols having mixed hydrocarbon and fluorocarbon tail groups exhibited better antifouling performance when compared to the SAMs derived from their single-component monodentate counterparts. The studies also revealed that while the SPR and the QCM measurements in most cases were able to distinguish the adsorption trends for the SAMs and proteins examined, the ellipsometric thickness measurements were markedly less discriminating. On the whole, these studies validate the use of unsymmetrical partially fluorinated spiroalkanedithiols for generating effective antifouling coatings on metal substrates.

The Covalent Tethering of Poly(ethylene glycol) to Nylon 6 Surface via N,N'-Disuccinimidyl Carbonate Conjugation: A New Approach in the Fight against Pathogenic Bacteria

Different forms of unmodified and modified Poly(ethylene glycols) (PEGs) are widely used as antifouling and antibacterial agents for biomedical industries and Nylon 6 is one of the polymers used for biomedical textiles. Our recent study focused on an efficient approach to PEG immobilization on a reduced Nylon 6 surface via N,N'-disuccinimidyl carbonate (DSC) conjugation. The conversion of amide functional groups to secondary amines on the Nylon 6 polymer surface was achieved by the reducing agent borane-tetrahydrofuran (BH3-THF) complex, before binding the PEG. Various techniques, including water contact angle and free surface energy measurements, atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy, were used to confirm the desired surface immobilization. Our findings indicated that PEG may be efficiently tethered to the Nylon 6 surface via DSC, having an enormous future potential for antifouling biomedical materials. The bacterial adhesion performances against S. aureus and P. aeruginosa were examined. In vitro cytocompatibility was successfully tested on pure, reduced, and PEG immobilized samples.

Highly-reactive haloester surface initiators for ARGET ATRP readily prepared by radio frequency glow discharge plasma

New surface initiators for ARGET ATRP (activators regenerated by electron transfer atomic transfer radical polymerization) have been prepared by the plasma deposition of haloester monomers. Specifically, methyl 3-bromopropionate (M3BP), methyl 2-chloropropionate, and ethyl 2-fluoropropionate (E2FP) were plasma deposited onto glass discs using RF glow discharge plasma. This technique creates surface coatings that are resistant to delamination and rich in halogen species making them good candidates for surface initiators for ARGET ATRP. Of all the plasma polymerized surface coatings, M3BP showed the highest halogen content and was able to grow 2-hydroxyethyl methacrylate (HEMA) polymer brushes on its surface via ARGET ATRP in as little as 15 min as confirmed by XPS. Surprisingly, E2FP, a fluoroester, was also able to grow HEMA polymer brushes despite fluorine being a poor leaving group for ARGET ATRP. The versatility of RF glow discharge plasma offers a clear advantage over other techniques previously used to immobilize ARGET ATRP surface initiators.

Antifouling Surface Coating Using Droplet-Based SI-ARGET ATRP of Carboxybetaine under Open-Air Conditions

The formation of a dense zwitterionic brush through surface-initiated atom transfer radical polymerization (SI-ATRP) is a typical graft-from approach used to achieve antifouling surfaces with high fidelity; however, their air-tightness may cause inconvenience to users. In this context, activator regenerated by electron transfer (ARGET) ATRP is emerging as an alternative surface-coating tool because limited amount of air is allowed to form a dense polymer brush. However, the degree of air tolerance that can ensure a thick polymer brush has not been clearly defined, limiting its practical usage under ambient-air conditions. In this study, we investigated the SI-ARGET ATRP of carboxybetaine (CB) by changing the air conditions, along with the air-related parameters, such as the concentration of the reducing agent, the volume of the polymerization solution (PS), or the solvent composition, and correlated their effects with the poly(CB) thickness. Based on the optimized reaction conditions, a poly(CB) brush with reliable thickness was feasibly formed even under open-air conditions without a degassing step. In addition, a microliter droplet (∼100 μL) of PS was sufficient to proceed with the SI-ARGET ATRP for the covering of a poly(CB) brush on the surface area of interest. By applying an optimized SI-ARGET ATRP of CB, antifouling was feasibly achieved in the surface region of interest using an array to form a large surface area under fully exposed air conditions. In other words, optimized SI-ARGET ATRP enabled the formation of a thick poly(CB) brush on the surfaces of various dimensions under open-air conditions.

Preparation and antibacterial activity of silver-loaded poly(oligo(ethylene glycol) methacrylate) brush

Herein, we report on a robust approach to fabricate antibacterial nanocomposite coating simply by immersing poly(oligo(ethylene glycol) methacrylate) (POEGMA) brush into a silver perchlorate solution without using any external reducing agents. The POEGMA brush of 48.3 nm in thickness is prepared via surface-initiated atom transfer radical polymerization method. Field-emission scanning electron microscope and Raman measurements indicate that silver nanoparticles of 14 ∼ 25 nm in diameter are successfully embedded into the POEGMA brush. Antibacterial activities of the resultant silver-loaded POEGMA brushes against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus are measured by zone of inhibition and colony-counting methods, respectively. The results show that the silver-loaded POEGMA coatings exhibit enhanced antibacterial efficiency compared to bare POEGMA brush. In order to elucidate their antibacterial mechanism, silver release behaviors of these silver-loaded POEGMA brushes are monitored via inductively coupled plasma mass spectrometry.

Development of a shear ultrasonic spectroscopy technique for the evaluation of viscoelastic fluid properties: Theory and experimental validation

In-situ measurement of viscosity advances the field of rheology, and aides the development of sensing systems for condition and performance monitoring of lubricated mechanisms. Many lubricated mechanisms, such as journal bearings or seals, are characterised by three-layer interfaces; an oil separating two solid (usually metallic) bodies. The viscoelastic study of the lubricating oil in layered systems is possible in-situ by means of ultrasonic reflection (Schirru et al. (2015)). General solutions exist for the reflection of longitudinal plane waves from multi-layered solid-fluid systems. Similar solutions can be applied to plane shear waves. The use of a quarter-wavelength intermediate matching layer improves the sensitivity of the ultrasonic measurement and overcomes problems of acoustic mismatch. This opens the possibility of using reflectance methods to measure engineering (metal-oil) bearing applications that are acoustically mismatched. In this paper, a rigorous mathematical model for wave propagation in a three-layer system is solved for the reflection coefficient modulus and validated using a quarter wavelength ultrasonic viscometer. The model was tested against experimental data for two Newtonian reference fluids, water and hexadecane, and for one non-Newtonian reference fluid, squalene plus polyisoprene (SQL + PIP), measured ultrasonically at frequencies between 5 and 15 MHz. The results are in agreement with the expected viscosity values for the reference fluids. Further, the viscosity measurement is not limited to the resonance frequency, but it is performed over a broad band frequency range. This is important to improve measurement confidence and accurate spectroscopy measurement for the determination of viscoelastic properties.

Architectural Modification of Conformal PEG-Bottlebrush Coatings Minimizes Anti-PEG Antigenicity While Preserving Stealth Properties

Poly(ethylene glycol) (PEG), a linear polymer known for its "stealth" properties, is commonly used to passivate the surface of biomedical implants and devices, and it is conjugated to biologic drugs to improve their pharmacokinetics. However, its antigenicity is a growing concern. Here, the antigenicity of PEG is investigated when assembled in a poly(oligoethylene glycol) methacrylate (POEGMA) "bottlebrush" configuration on a planar surface. Using ethylene glycol (EG) repeat lengths of the POEGMA sidechains as a tunable parameter for optimization, POEGMA brushes with sidechain lengths of two and three EG repeats are identified as the optimal polymer architecture to minimize binding of anti-PEG antibodies (APAs), while retaining resistance to nonspecific binding by bovine serum albumin and cultured cells. Binding of backbone- versus endgroup-selective APAs to POEGMA brushes is further investigated, and finally the antigenicity of POEGMA coatings is assessed against APA-positive clinical plasma samples. These results are applied toward fabricating immunoassays on POEGMA surfaces with minimal reactivity toward APAs while retaining a low limit-of-detection for the analyte. Taken together, these results offer useful design concepts to reduce the antigenicity of polymer brush-based surface coatings used in applications involving human or animal matrices.

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.

Reducing Bacterial Infections and Biofilm Formation Using Nanoparticles and Nanostructured Antibacterial Surfaces

With the rapid spreading of resistance among common bacterial pathogens, bacterial infections, especially antibiotic-resistant bacterial infections, have drawn much attention worldwide. In light of this, nanoparticles, including metal and metal oxide nanoparticles, liposomes, polymersomes, and solid lipid nanoparticles, have been increasingly exploited as both efficient antimicrobials themselves or as delivery platforms to enhance the effectiveness of existing antibiotics. In addition to the emergence of widespread antibiotic resistance, of equal concern are implantable device-associated infections, which result from bacterial adhesion and subsequent biofilm formation at the site of implantation. The ineffectiveness of conventional antibiotics against these biofilms often leads to revision surgery, which is both debilitating to the patient and expensive. Toward this end, micro- and nanotopographies, especially those that resemble natural surfaces, and nonfouling chemistries represent a promising combination for long-term antibacterial activity. Collectively, the use of nanoparticles and nanostructured surfaces to combat bacterial growth and infections is a promising solution to the growing problem of antibiotic resistance and biofilm-related device infections.

Systematic Study of Functionalizable, Non-Biofouling Agarose Films with Protein and Cellular Patterns on Glass Slides

Herein we demonstrate a systematic investigation of chemically functionalizable, non-biofouling agarose films over large-area glass surfaces. Agarose films, prepared with various concentrations of aqueous agarose, were activated by using periodate oxidation to generate aldehyde groups at the termini of the agarose chains. The non-biofouling efficacy and binding capabilities of the activated films were evaluated by using protein and cellular patterning, performed by using a microarrayer, microcontact printing, and micromolding in capillaries. Characterization by using a fluorescence slide scanner and a scanning-probe microscope revealed that the pore sizes of the agarose films played an important role in achieving desirable film performance; the 0.2 wt % agarose film exhibited the optimum efficacy in this work.

Poly(oligo(ethylene glycol) methyl ether methacrylate) Brushes on High-κ Metal Oxide Dielectric Surfaces for Bioelectrical Environments

Advances in electronics and life sciences have generated interest in "lab-on-a-chip" systems utilizing complementary metal oxide semiconductor (CMOS) circuitry for low-power, portable, and cost-effective biosensing platforms. Here, we present a simple and reliable approach for coating "high-κ" metal oxide dielectric materials with "non-fouling" (protein- and cell-resistant) poly(oligo(ethylene glycol) methyl ether methacrylate (POEGMA) polymer brushes as biointerfacial coatings to improve their relevance for biosensing applications utilizing advanced electronic components. By using a surface-initiated "grafting from" strategy, POEGMA films were reliably grown on each material, as confirmed by ellipsometric measurements and X-ray photoelectron spectroscopy (XPS) analysis. The electrical behavior of these POEGMA films was also studied to determine the potential impact on surrounding electronic devices, yielding information on relative permittivity and breakdown field for POEGMA in both dry and hydrated states. We show that the incorporation of POEGMA coatings significantly reduced levels of nonspecific protein adsorption compared to uncoated high-κ dielectric oxide surfaces as shown by protein resistance assays. These attributes, combined with the robust dielectric properties of POEGMA brushes on high-κ surfaces open the way to incorporate this protein and cell resistant polymer interface into CMOS devices for biomolecular detection in a complex liquid milieu.

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.

Dielectric and Mechanical Investigations on the Hydrophilicity and Hydrophobicity of Polyethylene Oxide Modified on a Silicon Surface

Polyethylene oxide (PEO) has been widely used in biomedical fields. The antibiofouling property of the PEO-modified surface has been extensively investigated but is far from being fully understood. A series of PEOs with narrowly distributed molecular weight (M_w), synthesized with the technique of high vacuum anionic polymerization, have been successfully grafted onto the surface of silicon wafers. The power-law relationship between the thickness of the monolayer versus the M_w of the grafted PEO shows a scaling of 0.3, indicating compact condensing of the chains. The static contact angles show higher hydrophobicity for the layer of PEO with higher M_w, which can be attributed to the closely packed conformation of the chains with high density. The frequency shift of the contact resonance indicates that the Young's modulus decreases and the loss factor increases with the increase in the M_w of PEO and the thickness of the PEO layers. Dielectric spectroscopy of bare or PEO-grafted wafers in the aqueous solutions reveals an interfacial polarization, which results from compositional and structural changes in the interface layer and depends on temperatures and salt concentrations. At a given grafting density, the PEO chains are swollen in pure water, demonstrating hydrophilic behavior, whereas they collapse in salt solutions, showing hydrophobic characteristics.

Controlling integrin-based adhesion to a degradable electrospun fibre scaffold via SI-ATRP

While polycaprolactone (PCL) and similar polyesters are commonly used as degradable scaffold materials in tissue engineering and related applications, non-specific adsorption of environmental proteins typically precludes any control over the signalling pathways that are activated during cell adhesion to these materials. Here we describe the preparation of PCL-based fibres that facilitate cell adhesion through well-defined pathways while preventing adhesion via adsorbed proteins. Surface-initiated atom transfer radical polymerisation (SI-ATRP) was used to graft a protein-resistant polymer brush coating from the surface of fibres, which had been electrospun from a brominated PCL macroinitiator. This coating also provided alkyne functional groups for the attachment of specific signalling molecules via the copper-mediated azide-alkyne click reaction; in this case, a cyclic RGD peptide with high affinity for α_vβ₃ integrins. Mesenchymal stem cells were shown to attach to the fibres via the peptide, but did not attach in its absence, nor when blocked with soluble peptide, demonstrating the effective control of cell adhesion pathways.

Polymer Brushes for Membrane Separations: A Review

The fundamentals and applications of polymer brush-modified membranes are reviewed. This new class of synthetic membranes is explored with an emphasis on tuning the membrane performance through polymer brush grafting. This work highlights the intriguing performance characteristics of polymer brush-modified membranes in a variety of separations. Polymer brushes are a versatile and effective means in designing membranes for applications in protein adsorption and purification, colloid stabilization, sensors, water purification, pervaporation of organic compounds, gas separations, and as stimuli responsive materials.

Backfilling-Free Strategy for Biopatterning on Intrinsically Dual-Functionalized Poly[2-Aminoethyl Methacrylate-co-Oligo(Ethylene Glycol) Methacrylate] Films

We demonstrated protein and cellular patterning with a soft lithography technique using poly[2-aminoethyl methacrylate-co-oligo(ethylene glycol) methacrylate] films on gold surfaces without employing a backfilling process. The backfilling process plays an important role in successfully generating biopatterns; however, it has potential disadvantages in several interesting research and technical applications. To overcome the issue, a copolymer system having highly reactive functional groups and bioinert properties was introduced through a surface-initiated controlled radical polymerization with 2-aminoethyl methacrylate hydrochloride (AMA) and oligo(ethylene glycol) methacrylate (OEGMA). The prepared poly(AMA-co-OEGMA) film was fully characterized, and among the films having different thicknesses, the 35 nm-thick biotinylated, poly(AMA-co-OEGMA) film exhibited an optimum performance, such as the lowest nonspecific adsorption and the highest specific binding capability toward proteins.

Control of Protein Affinity of Bioactive Nanocellulose and Passivation Using Engineered Block and Random Copolymers

We passivated TEMPO-oxidized cellulose nanofibrils (TOCNF) toward human immunoglobulin G (hIgG) by modification with block and random copolymers of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA). The block copolymers reversibly adsorbed on TOCNF and were highly effective in preventing nonspecific interactions with hIgG, especially if short PDMAEMA blocks were used. In such cases, total protein rejection was achieved. This is in contrast to typical blocking agents, which performed poorly. When an anti-human IgG biointerface was installed onto the passivated TOCNF, remarkably high affinity antibody-antigen interactions were observed (0.90 ± 0.09 mg/m(2)). This is in contrast to the nonpassivated biointerface, which resulted in a significant false response. In addition, regeneration of the biointerface was possible by low pH aqueous wash. Protein A from Staphylococcus aureus was also utilized to successfully increase the sensitivity for human IgG recognition (1.28 ± 0.11 mg/m(2)). Overall, the developed system based on TOCNF modified with multifunctional polymers can be easily deployed as bioactive material with minimum fouling and excellent selectivity.

Robust Thick Polymer Brushes Grafted from Gold Surfaces Using Bidentate Thiol-Based Atom-Transfer Radical Polymerization Initiators

A new bromoisobutyrate-terminated alkanethiol, 16-(3,5-bis(mercaptomethyl)phenoxy)hexadecyl 2-bromo-2-methylpropanoate (BMTBM), was designed as a bidentate adsorbate to form thermally stable bromoisobutyrate-terminated self-assembled monolayers (SAMs) on flat gold surfaces to conduct atom-transfer radical polymerizations (ATRPs). The monolayers derived from BMTBM were characterized by ellipsometry, X-ray photoelectron spectroscopy (XPS), and polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and compared to the monolayers formed from 16-mercaptohexadecyl 2-bromo-2-methylpropanoate (MBM), 16-(3-(mercaptomethyl)phenoxy)hexadecyl 2-bromo-2-methyl-propanoate (MTBM), and octadecanethiol (C18SH). In this study, although the monolayer derived from BMTBM was less densely packed than those derived from MBM and MTBM, the bidentate adsorbates demonstrated much higher thermal stability in solution-phase thermal desorption tests, owing to the "chelate effect". The enhanced stability of the BMTBM SAMs ensured the development of thick brushes of poly(methyl methacrylate) and polystyrene at elevated temperatures (60, 90, 105, and 120 °C). In contrast, SAMs derived from MBM and MTBM failed to grow polymer brushes at temperatures above 100 °C.

Clickable and Antifouling Platform of Poly[(propargyl methacrylate)-ran-(2-methacryloyloxyethyl phosphorylcholine)] for Biosensing Applications

A functional copolymer platform, namely, poly[(propargyl methacrylate)-ran-(2-methacryloyloxyethyl phosphorylcholine)] (PPgMAMPC), was synthesized by reversible addition-fragmentation chain-transfer polymerization. In principle, the alkyne moiety of propargyl methacrylate (PgMA) should serve as an active site for binding azide-containing molecules via a click reaction, i.e., Cu-catalyzed azide/alkyne cycloaddition (CuAAC), and 2-methacryloyloxyethyl phosphorylcholine (MPC), the hydrophilic monomeric unit, should enable the copolymer to suppress nonspecific adsorption. The copolymers were characterized using Fourier transform infrared (FTIR) and (1)H NMR spectroscopies. Thiol-terminated, PPgMAMPC-SH, obtained by aminolysis of PPgMAMPC, was immobilized on a gold-coated substrate using a "grafting to" approach via self-assembly. Azide-containing species, namely, biotin and peptide nucleic acid (PNA), were then immobilized on the alkyne-containing copolymeric platform via CuAAC. The potential use of surface-attached PPgMAMPC in biosensing applications was shown by detection of specific target molecules, i.e., streptavidin (SA) and DNA, by the developed sensing platform using a surface plasmon resonance technique. The copolymer composition strongly influenced the performance of the developed sensing platform in terms of signal-to-noise ratio in the case of the biotin-SA system and hybridization efficiency and mismatch discrimination for the PNA-DNA system.

Patchable, flexible heat-sensing hybrid ionic gate nanochannel modified with a wax-composite

Heat-driven ionic gate nanochannels have been recently demonstrated, which exploit temperature-responsive polymer brushes based on wettability. These heat-sensing artificial nanochannels operate in a broad temperature-response boundary and fixed liquid cell environment, thereby experiencing limited system operation in the flat and solid state. Here we have developed a patchable and flexible heat-sensing artificial ionic gate nanochannel, which can operate in the range of the human body temperature. A wax-elastic copolymer, coated onto a commercial nanopore membrane by a controlled-vacuum filtration method, was used for the construction of temperature-responsive nanopores. The robust and flexible nanochannel heat sensor, which is combined with an agarose gel electrolyte, can sustain reversible thermo-responsive ionic gating based on the volumetric work of the wax-composite layers in a selective temperature range. The ionic current is also effectively distinguished in the patchable bandage-type nanochannel for human heat-sensing.

One-step functionalization of zwitterionic poly[(3-(methacryloylamino)propyl)dimethyl(3-sulfopropyl)ammonium hydroxide] surfaces by metal–polyphenol coating

The non-biofouling properties of a zwitterionic sulfobetaine polymer surface were easily made attractive to bioentities by metal–polyphenol coating.

Synthesis of grafted phosphorylcholine polymer layers as specific recognition ligands for C-reactive protein focused on grafting density and thickness to achieve highly sensitive detection

We studied the effects of layer thickness and grafting density of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) thin layers as specific ligands for the highly sensitive binding of C-reactive protein (CRP).

A quartz crystal microbalance as a tool for biomolecular interaction studies

A quartz crystal microbalance was successfully applied to quantitatively analyze biomolecular interactions using a poly(ethylene glycol) matrix and equations for impedance analysis of frequency changes at multiple overtones.

A robust graft-to strategy to form multifunctional and stealth zwitterionic polymer-coated mesoporous silica nanoparticles

Mesoporous silica nanoparticles (MSNs) are a new class of carrier materials promising for drug/gene delivery and many other important applications. Stealth coatings are necessary to maintain their stability in complex media. Herein, a biomimetic polymer conjugate containing one ultralow fouling poly(carboxybetaine) (pCBMA) chain and one surface-adhesive catechol (DOPA) residue group was efficiently grafted to the outer surface of SBA-15 type MSNs using a convenient and robust method. The cytotoxicity of SBA-15-DOPA-pCBMAs was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Results showed no significant decrease in cell viability at the tested concentration range. Macrophage cell uptake studies revealed that the uptake ratios of SBA-15-DOPA-pCBMAs were much lower than that of parent MSNs. Furthermore, inductively coupled plasma mass spectrometry (ICP-MS) analysis results showed that after SBA-15-DOPA-pCBMAs were conjugated with a targeting cyclo-[Arg-Gly-Asp-d-Tyr-Lys] (cRGD) peptide, uptake by bovine aortic endothelial cells (BAECs) was notably increased. Results indicated that cRGD-functionalized MSNs were able to selectively interact with cells expressing αvβ3 integrin. Thus, MSNs with DOPA-pCBMAs are promising as stealth multifunctional biocarriers for targeted drug delivery or diagnostics.