Nanosphere Lithography as a Versatile Method to Generate Surface‐Imprinted Polymer Films for Selective Protein Recognition

A versatile approach based on nanosphere lithography is proposed to generate surface‐imprinted polymers for selective protein recognition. A layer of 750 nm diameter latex bead‐protein conjugate is deposited onto the surface of gold‐coated quartz crystals followed by the electrosynthesis of a poly(3,4‐ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) film with thicknesses on the order of the bead radius. The removal of the polymer bead‐protein conjugates, facilitated by using a cleavable protein‐nanosphere linkage is shown to result in 2D arrays of periodic complementary size cavities. Here it is demonstrated by nanogravimetric measurements that the imprinting proceeds further at molecular level and the protein (avidin) coating of the beads generates selective recognition sites for avidin on the surface of the PEDOT/PSS film. The binding capacity of such surface‐imprinted polymer films is ca. 6.5 times higher than that of films imprinted with unmodified beads. They also exhibit excellent selectivity against analogues of avidin, i.e., extravidin, streptavidin, and neutravidin, the latter being in fact undetectable. This methodology, if coupled with properly oriented conjugation of the macromolecular template to the nanoparticles, offers the possibility of site‐directed imprinting.     

Hybrid Material for Protein Sensing Based on Electrosynthesized MIP on a Mannose Terminated Self‐Assembled Monolayer

A novel strategy to prepare a surface confined molecularly imprinted polymer (MIP) film directly on a transducer surface for protein sensing is achieved by combining interaction with a natural binding receptor and binding to a fully synthetic MIP. A thiolated oligoethyleneglycol (OEG)/mannose conjugate is first self‐assembled on the transducer surface. Then the carbohydrate binding protein, concanavalin A (ConA), is “vectorially” immobilized as a submonolayer on the underlying mannose modified surface. Afterwards, an ultrathin polyscopoletin film with the thickness comparable to that of the protein is electrodeposited on the top. This architecture ensures that the target is confined to the film surface. The resulting functional material shows an approximately 20‐fold higher affinity than that obtained from the mannose self‐assembled monolayer. This result shows a synergism between multivalent binding of the natural sugar ligand and the non‐covalent interactions of the target within the MIP cavities. Recognition capability of the film is characterized by a real‐time measurement using quartz crystal microbalance. In comparison to the non‐imprinted film, the imprinted film reveals 8.6 times higher binding capacity towards ConA. High discrimination towards the target protein's homologues shows size and shape specificity of the imprint.     

A Zipper‐Like On/Off‐Switchable Molecularly Imprinted Polymer

A zipper‐like on/off‐switchable molecularly imprinted polymer is reported. This unique imprinted polymer was composed of template‐imprinted polymeric networks that incorporate zipper‐like interactions between poly(acrylamide) (PAAm) and poly(2‐acrylamide‐2‐methyl propanesulfonic acid) (PAMPS). This polymer showed marginal recognition ability towards the imprint species under low temperature conditions, due to the interpolymer interaction between PAAm and PAMPS, which inhibited access to the imprinted networks. In contrast, at relatively high temperatures (such as 40 °C), the polymer demonstrated significant molecular recognition ability towards the imprint species resulting from the dissociation of the interpolymer complexes of PAAm and PAMPS, which enabled access to the imprint networks. Unlike previously reported PNIPAm‐based imprinted polymers, which demonstrate alterable molecular recognition simply because of the thermosensitive hydrophilicity/hydrophobicity of PNIPAm, this polymer employed a zipper‐like supramolecular architecture between PAAm and PAMPS, thereby enabling switchable molecular recognition.     

pH‐Responsive Flower‐Type Micelles Formed by a Biotinylated Poly(2‐vinylpyridine)‐block‐poly(ethylene oxide)‐block‐poly(ε‐caprolactone) Triblock Copolymer

In the present work, a method is proposed to assemble pH‐responsive, flower‐like micelles that can expose a targeting unit at their periphery upon a decrease in pH. The micelles are composed of a novel biotinylated triblock copolymer of poly(εε‐caprolactone)‐block‐poly(ethylene oxide)‐block‐poly(2‐vinylpyridine) (PCL‐b‐PEO‐b‐P2VP) and the non‐biotinylated analogue. The block copolymers are synthesized by sequential anionic and ring‐opening polymerization. The pH‐dependent micellization behaviour in aqueous solution of the triblock copolymers developed is studied using dynamic light scattering, zeta potential, transmission electron microscopy (TEM), and fluorimetric measurements. The shielding of the biotin at neutral pH and their availability at the micelle surface upon protonation is established by TEM and surface plasmon resonance with avidin and streptavidin‐coated gold surfaces. The preliminary stealthy behavior of these pH‐responsive micelles is examined using the complement activation (CH50) test.     

Adhesion and Surface Interactions of a Self‐Healing Polymer with Multiple Hydrogen‐Bonding Groups

The surface properties and self‐adhesion mechanism of self‐healing poly(butyl acrylate) (PBA) copolymers containing comonomers with 2‐ureido‐4[1H]‐pyrimidinone quadruple hydrogen bonding groups (UPy) are investigated using a surface forces apparatus (SFA) coupled with a top‐view optical microscope. The surface energies of PBA–UPy4.0 and PBA–UPy7.2 (with mole percentages of UPy 4.0% and 7.2%, respectively) are estimated to be 45–56 mJ m^?2 under dry condition by contact angle measurements using a three probe liquid method and also by contact and adhesion mechanics tests, as compared to the reported literature value of 31–34 mJ m^?2 for PBA, an increase that is attributed to the strong UPy–UPy H‐bonding interactions. The adhesion strengths of PBA–UPy polymers depend on the UPy content, contact time, temperature and humidity level. Fractured PBA–UPy films can fully recover their self‐adhesion strength to 40, 81, and 100% in 10 s, 3 h, and 50 h, respectively, under almost zero external load. The fracture patterns (i.e., viscous fingers and highly “self‐organized” parallel stripe patterns) have implications for fabricating patterned surfaces in materials science and nanotechnology. These results provide new insights into the fundamental understanding of adhesive mechanisms of multiple hydrogen‐bonding polymers and development of novel self‐healing and stimuli‐responsive materials.     

Peptide‐Enhanced Selective Surface Deposition of Polymer‐Based Fragrance Delivery Systems

Surface deposition is a critical step in the application of fragrance‐containing products. This contribution presents a novel strategy to enhance the deposition of polymer‐based fragrance delivery systems onto cotton substrates from the application medium using phage display identified peptides. Following the identification of cotton binding peptide ligands under fabric softening conditions via phage display, the strongest binding peptide ligand is incorporated into two model polymer‐based fragrance delivery systems, viz., polymer profragrances and polymer nanoparticles. The model polymer profragrance used is a linear, water soluble poly(N‐(2‐hydroxypropyl)methacrylamide) conjugate, while poly(styrene‐co‐acrylic acid) (PS‐co‐PAA) nanoparticles prepared via miniemulsion polymerization are chosen as the second model system. The incorporation of the cotton binding peptide ligand into these fragrance delivery systems enhances their surface deposition two‐ to three‐fold, as evidenced by fluorescence intensity measurements. In the case of the fragrance‐containing PS‐co‐PAA nanoparticles, the enhanced surface deposition also translates into an increased fragrance release from the cotton surface according to dynamic headspace sampling measurements.     

Zn(II)‐Protoporphyrin IX‐Based Photosensitizer‐Imprinted Au‐Nanoparticle‐Modified Electrodes for Photoelectrochemical Applications

The electropolymerization of thioaniline‐modified Au nanoparticles (NPs) on thioaniline monolayer‐functionalized electrodes in the presence of Zn(II)‐protoporphyrin IX yields bis aniline‐crosslinked Au NPs matrices that include molecular imprinted sites for binding the Zn(II)‐protoporphyrin IX photosensitizer. The binding of the photosensitizer yields photoelectrochemically active electrodes that produce anodic photocurrents in the presence of the electron donor benzohydroquinone. The efficient photocurrents formed in the presence of the imprinted electrode are attributed to the high‐affinity binding of the photosensitizer to the imprinted sites, K_a = 3.2 × 10⁶ m ^?1, and to the effective transport of the photoejected electrons to the bulk electrode via the bridged Au NPs matrix. Similarly, a N,N′‐dialkyl‐4,4′‐bipyridinium‐modified Zn(II)‐protoporphyrin IX photosensitizer‐electron acceptor dyad is imprinted in the bis aniline‐crosslinked Au NPs matrix. The photocurrent generated by the imprinted matrix is approximately twofold higher as compared to the photocurrent generated by the Zn(II)‐protoporphyrin IX‐imprinted Au NPs matrix. The efficient photocurrents generated in the presence of the bipyridinium‐modified Zn(II)‐protoporphyrin IX‐imprinted matrix are attributed to the effective primary charge separation of the electron–hole species in the dyad structure, followed by the effective transport of the photoejected electrons to the electrode via the bis aniline‐crosslinked Au NPs matrix.     

Surface Molecularly Imprinted Polymer Core–Shell Particles

Core–shell molecularly imprinted polymers (CS‐MIPs) have been prepared by aqueous emulsion polymerization using water‐soluble template molecules. An amphiphilic binding monomer, oleyl phenyl hydrogen phosphate and ethylene glycol dimethacrylate were used in the formation of highly crosslinked surfaces around divinyl benzene crosslinked polystyrene core colloids. Evidence was obtained by transmission electron microscopy (TEM) for a change in surface morphology when the polymer shell was formed in the presence of a template. The caffeine‐imprinted polymers were shown to bind caffeine in preference to theophylline from an equimolar mixture of the compounds in aqueous solution at pH 7.0, whilst concentration–binding (Scatchard) curves revealed the presence of two populations of binding sites in aqueous phosphate buffer at pH 8.0 for caffeine and theophylline. Similar studies were also carried out for (S)‐propranolol and (S)‐atenolol at pH 5.5, which also revealed the presence of two populations of binding sites for core–shell particles imprinted with these compounds. (S)‐Propranolol was selectively removed from a solution of (S)‐propranolol and (S)‐atenolol by both of the CS‐MIPs, whereas the non‐imprinted particle showed no selectivity for either component.     

Protein Rebinding to a Surface‐Confined Imprint

A novel strategy to prepare a selective ultrathin molecularly imprinted polymer (MIP) film directly on the gold‐based transducer surface for the peptide and protein detection in aqueous solution is demonstrated using a combination of epitope‐ and electrochemical surface imprinting approach. The synthetic peptide derived from the surface‐exposed C‐terminus of cytochrome c (Cyt c, residues 96–104) is selected as the template for the imprinting. It is labeled with a fluorescent dye in order to quantitatively evaluate all stages of the imprinting process in terms of changes in mean fluorescence intensity. The labeled peptide template is first chemisorbed on the gold surface as an oriented submonolayer through an additional C‐terminal cysteine. After electropolymerization, the template is stripped off electrochemically. To allow the imprinted sites to be confined to the surface, the film thickness is controlled to be comparable to the thickness of the peptide layer. This is achieved by the electropolymerization of scopoletin. Recognition capabilities of the films are characterized and the resulting MIP film is able to selectively capture the template peptide and the corresponding target protein. In case of the peptide recognition, the MIP film can discriminate even the single amino acid mismatched sequences of the target peptide.     

Engineering a Robust,Versatile Amphiphilic Membrane Surface Through Forced Surface Segregation for Ultralow Flux‐Decline

Unlike biofoulants/pollutants, oil foulants/pollutants are prone to coalesce, spread and migrate to form continuous fouling layer covering on the surfaces. Therefore, such kind of fouling can not be simply alleviated by hydrophilic modification with currently extensively used antifouling materials such as poly(ethylene glycol) (PEG)‐based or zwitterionic polymers etc. In the present study, an amphiphilic porous membrane surface, comprising hydrophilic fouling resistant domains and hydrophobic fouling release microdomains, is explored via a "forced surface segregation" approach. The resultant membranes exhibit both superior oil‐fouling and bio‐fouling resistant property: membrane fouling is exquisitely suppressed and the permeation flux‐decline is decreased to an ultralow level. It can be envisaged that the present study may open a novel avenue to the design and construction of robust, versatile antifouling surfaces.     

Photo‐Induced Functionalization of Spherical and Planar Surfaces via Caged Thioaldehyde End‐Functional Polymers

The synthesis and application of a novel reversible addition‐fragmentation chain transfer (RAFT) agent carrying a photocaged thioaldehyde moiety is described (λ_max = 355 nm). RAFT polymerization of styrene, dimethylacrylamide and a glycomonomer is evidenced (3600 g mol^?1 ≤ M_n ≤ 15 000 g mol^?1; 1.07 ≤ ? ≤ 1.20) with excellent end‐group fidelity. The photogenerated thioaldehyde on the chain ends can undergo hetero Diels–Alder reactions with dienes as well as reactions with nucleophiles. The terminal photoreactive polymers are photografted to porous diene‐reactive polymeric microspheres. The grafted particles are in‐depth characterized via scanning electron microscopy, elemental analysis, X‐ray photoelectron spectroscopy, and high resolution FT‐IR microscopy, leading to a qualitative as well as quantitative image of the core–shell objects. Grafting densities up to 0.10 molecules nm^?2 are reached. The versatility of the thioaldehyde ligation is evidenced by spatially resolved grafting of polystyrene onto nucleophilic groups present in poly (dopamine) (PDA)‐coated glass slides and silicon wafers via two‐photon direct laser writing (DLW) imaged by ToF‐SIMS. The combination of thioaldehyde ligation, RAFT polymerization, and DLW allows for the spatially resolved grafting of a vast range of polymers onto various substrates in any desired pattern with sub‐micrometer resolution.     

Dispersions of Surface‐Modified Carbon Nanotubes in Water‐Soluble and Water‐Insoluble Polymers

Microscale aggregate formation, resulting from high intrinsic filler attractions, is one of the major issues in nanocomposite preparation and processing. Herein, the dispersive effects achieved by a wide range of surface‐active agents, as well as surface oxidation and functionalization, are investigated. The aim of our research is to form a uniform, multiwalled carbon nanotube (MWNT) distribution in water‐soluble (poly(ethylene glycol)) and water‐insoluble (polypropylene) polymers. In order to understand the surface‐charge‐related stability of the treated nanotubes solutions, zeta‐potential measurements are applied. Quantification of the state of the MWNT dispersion is derived from particle‐size analysis, while visual characterization is based on optical and electron microscopy. To estimate the nucleating ability of the surface‐modified carbon nanotubes, the temperature of crystallization and the degree of crystallinity are calculated from differential scanning thermograms. Finally, we suggest general guidelines to produce uniform MWNT dispersions using a dispersive agent and/or surface treatment in water‐soluble and water‐insoluble polymers.     

Enhanced Osteoblast Adhesion to Epoxide‐Functionalized Surfaces

As an alternative to expensive extracellular matrix (ECM) proteins generally applied as coatings in Petri dishes used for cell binding, an innovative system based on epoxide‐functionalized monolayers capable of protein binding is proposed. Since cells bind to material surfaces through proteins, protein‐binding surfaces should also promote cell binding. Here we investigate how the cell‐binding properties of an epoxide‐functionalized surface compares with ECM protein gel coated surfaces and tissue culture polystyrene control surfaces. Glass surfaces are functionalized with glycidoxypropyltriethoxysilane (GOPS), which results in an epoxide‐functionalized surface capable of binding proteins through an epoxide–amine reaction. Advancing contact angle measurements and atomic force microscopy measurements confirm the formation of a homogeneous GOPS monolayer. This monolayer is micropatterned with fluorescein‐labeled ECM protein gel by microcontact printing (µCP). Confocal laser scanning microscopy (CLSM) shows accurately transferred ECM protein gel micropatterns. Osteoblasts that are seeded on these micropatterned substrates show a clear preference for adhering to the epoxide‐functionalized areas. The morphology of these cultured osteoblasts is needle‐like with high aspect ratios. As controls, osteoblasts are cultured on GOPS‐functionalized surfaces, unstructured ECM protein gel surfaces, and tissue culture polystyrene (TCPS). The GOPS surfaces demonstrate a drastic increase in cell adhesion after 2 h, whilst the other tests show no adverse effects of this surface on the osteoblasts as compared to ECM and TCPS. CLSM shows healthy cell morphologies on each surface. It is demonstrated for the first time that epoxide groups outperform ECM protein gel in cell adhesion, thereby providing new routes for cost‐effective coatings that improve biocompatibility as well as exciting, new methodologies to control and direct cell adhesion.     

Blood‐Inert Surfaces via Ion‐Pair Anchoring of Zwitterionic Copolymer Brushes in Human Whole Blood

A strategy to create blood‐inert surfaces in human whole blood via ion‐pair anchoring of zwitterionic copolymer brushesand a systematic study of how well‐defined chain lengths and well‐controlled surface packing densities of zwitterionic polymers affect blood compatibility are reported. Well‐defined diblock copolymers, poly(11‐mercaptoundecyl sulfonic acid)‐block‐poly(sulfobetaine methacrylate) (PSA‐b‐PSBMA) with varying zwitterionic PSBMA or negatively charged PSA lengths, are synthesized via atom‐transfer radical polymerization (ATRP). PSA‐b‐PSBMA is grafted onto a surface covered with polycation brushes as a mimic polar/hydrophilic biomaterial surface via ion‐pair anchoring at a range of copolymer concentrations. Protein adsorption from single‐protein solutions, 100% blood serum, and 100% blood plasma onto the surfaces covered with PSA‐b‐PSBMA brushes is evaluated using a surface plasmon resonance sensor. Copolymer brushes containing a high amount of zwitterionic SBMA units are further challenged with human whole blood. Low protein‐fouling surfaces with >90% reduction with respect to uncoated surfaces are achieved with longer PSA blocks and higher concentrations of PSA‐b‐PSBMA copolymers using the ion‐pair anchoring approach. This work provides a platform to achieve the control of various surface parameters and a practical method to create blood‐inert surfaces in whole blood by grafting ionic‐zwitterionic copolymers to charged biomaterials via charge pairing.     

Temperature‐Switchable Assembly of Supramolecular Virus–Polymer Complexes

Here a method is presented for the temperature‐switchable assembly of viral particles into large hierarchical complexes. Dual‐functional diblock copolymers consisting of poly(diethyleneglycol methyl ether methacry­late) (poly(DEGMA)) and poly((2‐dimethylamino)ethyl methacrylate) (poly(DMAEMA)) blocks self‐assemble electrostatically with cowpea chlorotic mottle virus (CCMV) particles into micrometer‐sized objects as a function of temperature. The poly(DMAEMA) block carries a positive charge, which can interact electrostatically with the negatively charged outer surface of the CCMV capsid. When the solution temperature is increased above 40 °C, to cross the cloud point temperature (T_cp) of the DEGMA block, the polymer chains collapse on the surface of the virus particle, which makes them partially hydrophobic, and consequently causes the formation of large hierarchical assemblies. Disassembly of the virus–polymer complexes can be induced by reducing the solution temperature below the T_cp, which allows the poly(DEGMA) blocks to rehydrate and free virus particles to be released. The assembly process is fully reversible and can sustain several heating–cooling cycles. Importantly, this method relies on reversible supramolecular interactions and therefore avoids the irreversible covalent modification of the particle surface. This study illustrates the potential of temperature‐responsive polymers for controlled binding and releasing of virus particles.     

Halogen Bonding versus Hydrogen Bonding in Driving Self‐Assembly and Performance of Light‐Responsive Supramolecular Polymers

Halogen bonding is arguably the least exploited among the many non‐covalent interactions used in dictating molecular self‐assembly. However, its directionality renders it unique compared to ubiquitous hydrogen bonding. Here, the role of this directionality in controlling the performance of light‐responsive supramolecular polymers is highlighted. In particular, it is shown that light‐induced surface patterning, a unique phenomenon occurring in azobenzene‐containing polymers, is more efficient in halogen‐bonded polymer–azobenzene complexes than in the analogous hydrogen‐bonded complexes. A systematic study is performed on a series of azo dyes containing different halogen or hydrogen bonding donor moieties, complexed to poly(4‐vinylpyridine) backbone. Through single‐atom substitution of the bond‐donor, control of both the strength and the nature of the noncovalent interaction between the azobenzene units and the polymer backbone is achieved. Importantly, such substitution does not significantly alter the electronic properties of the azobenzene units, hence providing us with unique tools in studying the structure–performance relationships in the light‐induced surface deformation process. The results represent the first demonstration of light‐responsive halogen‐bonded polymer systems and also highlight the remarkable potential of halogen bonding in fundamental studies of photoresponsive azobenzene‐containing polymers.     

Induced SER‐Activity in Nanostructured Ag–Silica–Au Supports via Long‐Range Plasmon Coupling

A novel Ag–silica–Au hybrid device is developed that displays a long‐range plasmon transfer of Ag to Au leading to enhanced Raman scattering of molecules largely separated from the optically excited Ag surface. A nanoscopically rough Ag surface is coated by a silica spacer of variable thickness from ～1 to 21 nm and a thin Au film of ～25 nm thickness. The outer Au surface is further functionalized by a self‐assembled monolayer (SAM) for electrostatic binding of the heme protein cytochrome c (Cyt c) that serves as a Raman probe and model enzyme. High‐quality surface‐enhanced resonance Raman (SERR) spectra are obtained with 413 nm excitation, demonstrating that the enhancement results exclusively from excitation of Ag surface plasmons. The enhancement factor is estimated to be 2 × 10⁴–8 × 10³ for a separation of Cyt c from the Ag surface by 28–47 nm, corresponding to an attenuation of the enhancement by a factor of only 2–6 compared to Cyt c adsorbed directly on a SAM‐coated Ag electrode. Upon immobilization of Cyt c on the functionalized Ag–silica–Au device, the native structure and redox properties are preserved as demonstrated by time‐ and potential‐dependent SERR spectroscopy.     

Fabrication and Characterization of an OTFT‐Based Biosensor Using a Biotinylated F8T2 Polymer

Solution‐processable organic semiconductors have been investigated not only for flexible and large‐area electronics but also in the field of biotechnology. In this paper, we report the design and fabrication of biosensors based on completely organic thin‐film transistors (OTFTs). The active material of the OTFTs is poly(9,9‐dioctylfluorene‐co‐bithiophene) (F8T2) polymer functionalized with biotin hydrazide. The relationship between the chemoresistive change and the binding of avidin‐biotin moieties in the polymer is observed in the output and on/off characteristics of the OTFTs. The exposure of the OTFTs to avidin causes a lowering of ID at V_D = ‐40 V and V_G = ‐40 V of nearly five orders of magnitude.     

Functional and Well‐Defined β‐Sheet‐Assembled Porous Spherical Shells by Surface‐Guided Peptide Formation

Polypeptides have attracted widespread attention as building blocks for complex materials due to their ability to form higher‐ordered structures such as β‐sheets. However, the ability to precisely control the formation of well‐defined β‐sheet‐assembled materials remains challenging as β‐sheet formation tends to lead to ill‐defined and unprocessable aggregates. This work reports a simple, rapid, and robust strategy to form well‐defined peptide β‐sheet‐assembled shells (i.e., hollow spheres) by employing surface‐initiated N‐carboxyanhydride ring‐opening polymerization under a highly efficient surface‐driven approach. The concept is demonstrated by the preparation of enzyme‐degradable rigid shell architectures composed of H‐bonded poly(L‐valine) (PVal) grafts with porous and sponge‐like surface morphology. The porous PVal‐shells exhibit a remarkable and unprecedented ability to non‐covalently entrap metal nanoparticles, proteins, drug molecules, and biorelevant polymers, which could potentially lead to a diverse range of biodegradable and functional platforms for applications ranging from therapeutic delivery to organic catalysis.     

Hot Spot‐Localized Artificial Antibodies for Label‐Free Plasmonic Biosensing

The development of biomolecular imprinting over the last decade has raised promising perspectives in replacing natural antibodies with artificial antibodies. A significant number of reports have been dedicated to imprinting of organic and inorganic nanostructures, but very few were performed on nanomaterials with a transduction function. Herein, a relatively fast and efficient plasmonic hot spot‐localized surface imprinting of gold nanorods using reversible template immobilization and siloxane copolymerization is described. The technique enables a fine control of the imprinting process at the nanometer scale and provides a nanobiosensor with high selectivity and reusability. Proof of concept is established by the detection of neutrophil gelatinase‐associated lipocalin (NGAL), a biomarker for acute kidney injury, using localized surface plasmon resonance spectroscopy. The work represents a valuable step towards plasmonic nanobiosensors with synthetic antibodies for label‐free and cost‐efficient diagnostic assays. It is expected that this novel class of surface imprinted plasmonic nanomaterials will open up new possibilities in advancing biomedical applications of plasmonic nanostructures.