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Many cell membrane functions emerge from the lateral presentation of membrane receptors. The link between the nanoscale organization of the receptors and ligand binding remains, however, mostly unclear. In this work, we applied surface molecular imprinting and utilized the phase behavior of lipid bilayers to create platforms that recapitulate the lateral organization of membrane receptors at the nanoscale. We used liposomes decorated with amphiphilic boronic acids that commonly serve as synthetic saccharide receptors and generated three lateral modes of receptor presentation─random distribution, nanoclustering, and receptor crowding─and studied their interaction with saccharides. In comparison to liposomes with randomly dispersed receptors, surface-imprinted liposomes resulted in more than a 5-fold increase in avidity. Quantifying the binding affinity and cooperativity proved that the boost was mediated by the formation of the nanoclusters rather than a local increase in the receptor concentration. In contrast, receptor crowding, despite the presence of increased local receptor concentrations, prevented multivalent oligosaccharide binding due to steric effects. The findings demonstrate the significance of nanometric aspects of receptor presentation and generation of multivalent ligands including artificial lectins for the sensitive and specific detection of glycans.

Charge interactions play a critical role in the activation of the innate immune system by damage- and pathogen-associated molecular pattern receptors. The ability of these receptors to recognize a wide spectrum of ligands through a common mechanism is critical in host defense. In this article, we argue that platelet glycoprotein receptors that signal through conserved tyrosine-based motifs function as pattern recognition receptors (PRRs) for charged endogenous and exogenous ligands, including sulfated polysaccharides, charged proteins and nanoparticles. This is exemplified by GPVI, CLEC-2 and PEAR1 which are activated by a wide spectrum of endogenous and exogenous ligands, including diesel exhaust particles, sulfated polysaccharides and charged surfaces. We propose that this mechanism has evolved to drive rapid activation of platelets at sites of injury, but that under some conditions it can drive occlusive thrombosis, for example, when blood comes into contact with infectious agents or toxins. In this Opinion Article, we discuss mechanisms behind charge-mediated platelet activation and opportunities for designing nanoparticles and related agents such as dendrimers as novel antithrombotics.

The dynamic nature of micellar nanostructures is employed to form a self-assembled Förster resonance energy transfer (FRET) nanoplatform for enhanced sensing of DNA. The platform consists of lipid oligonucleotide FRET probes incorporated into micellar scaffolds, where single recognition events result in fusion and fission of DNA mixed micelles, triggering the fluorescence response of multiple rather than a single FRET pair. In comparison to conventional FRET substrates where a single donor interacts with a single acceptor, the micellar multiplex FRET system showed ∼20- and ∼3-fold enhancements in the limit of detection and FRET efficiency, respectively. This supramolecular signal amplification approach could potentially be used to improve FRET-based diagnostic assays of nucleic acid and non-DNA based targets.

Single-domain antibodies, known as nanobodies, have great potential as biorecognition elements for sensors because of their small size, affinity, specificity, and robustness. However, facile and efficient methods of nanobody immobilization are sought that retain their maximum functionality. Herein, we describe the direct immobilization of nanobodies on gold sensors by exploiting a modified cysteine strategically positioned at the C-terminal end of the nanobody. The experimental data based on secondary ion mass spectrometry, circular dichroism, and surface plasmon resonance, taken together with a detailed computational work (molecular dynamics simulations), support the formation of stable and well-oriented nanobody monolayers. Furthermore, the nanobody structure and activity is preserved, wherein the nanobody is immobilized at a high density (approximately 1 nanobody per 13 nm(2)). The strategy for the spontaneous nanobody self-assembly is simple and effective and possesses exceptional potential to be used in numerous sensing platforms, ranging from clinical diagnosis to environmental monitoring. The authors acknowledge the financial support of this work by the EPSRC (EP/K027263/1, EP/P029868/1, EP/L01646X/1, and EP/P031684/1), ERC (Consolidator Grant 614787), and Hasselt University and the Research Foundation Flanders (FWO Vlaanderen) via the Hercules project AUHL/15/2 - GOH3816N. The MD simulations and analyses were performed using the ARCHIE-WeSt High-Performance Computer (www.archie-west.ac.uk). S.J. acknowledges the support of the EPSRC (EP/ P030017/1).

Self‐assembled monolayers (SAMs) based on oligopeptides have garnered immense interest for a wide variety of innovative biomedical and electronic applications. However, to exploit their full potential, it is necessary to understand and control the surface chemistry of oligopeptides. Herein, we report on how different electrical potentials affect the adsorption kinetics, stability and surface coverage of charged oligopeptide SAMs on gold surfaces. Kinetic analysis using electrochemical surface plasmon resonance (e‐SPR) reveals a slower oligopeptide adsorption rate at more positive or negative electrical potentials. Additional analysis of the potential‐assisted formed SAMs by X‐ray photoelectron spectroscopy demonstrates that an applied electrical potential has minimal effect on the packing density. These findings not only reveal that charged oligopeptides exhibit a distinct potential‐assisted assembly behaviour but that an electrical potential offers another degree of freedom in controlling their adsorption rate., Self‐assembled monolayers based on oligopeptides are promising materials for biomedical and electronic applications. Herein, studies on potential‐assisted assembly of charged oligopeptides are presented that reveal slower adsorption kinetics in comparison with those self‐assembled at the open circuit potential, without it affecting the packing density. These findings expand the parameter space available to control oligopeptide assembly.

The kynurenine metabolite is associated with many diseases and disorders, ranging from diabetes and sepsis to more recently COVID-19. Here we report a fluorescence-based assay for the detection of kynurenine in urine using a specific chemosensor, 3-formyl-4-(ethylthio)-7-(diethylamino)-coumarin. The assay produces a linear response at clinically relevant ranges (1-20 μM), with a limit of detection of 0.7 μM. The average standard addition recoveries of kynurenine in synthetic urine samples are near to 100%, and the relative standard deviation values are less than 8%. The established fluorescence assay for quantitative analysis of kynurenine in urine is facile, sensitive and accurate and holds great potential for low-cost and high-throughput analysis of kynurenine in clinical laboratory settings.

Sialic acid recognition remains an interesting and challenging target in molecular receptor design. Herein, we report a series of benzoboroxole-based receptors in which cationic hydrogen-bond donors have been introduced and shown to promote multipoint sialic acid recognition. One striking feature revealed by these receptors is that the carboxylate sialic acid residue is the primary binding determinant for recognition by benzoboroxole, in which the presence of charge-reinforced hydrogen bonds results in enhanced selectivity for sialic acid over other carbohydrates and a 4.5-fold increase in affinity. These findings open up wide possibilities for benzoboroxole-based receptors use in life science research, biotechnology, and diagnostics.

The development of stimuli-responsive interfaces between synthetic materials and biological systems is providing the unprecedented ability to modulate biomolecular interactions for a diverse range of biotechnological and biomedical applications. Antibody-antigen binding interactions are at the heart of many biosensing platforms, but no attempts have been made yet to control antibody-antigen binding in an on-demand fashion. Herein, a molecular surface was designed and developed that utilizes an electric potential to drive a conformational change in surface bound peptide moiety, to give on-demand control over antigen-antibody interactions on sensor chips. The molecularly engineered surfaces allow for propagation of conformational changes from the molecular switching unit to a distal progesterone antigen, resulting in promotion (ON state) or inhibition (OFF state) of progesterone antibody binding. The approach presented here can be generally applicable to other antigen-antibody systems and meets the technological needs for in situ long-term assessment of biological processes and disease monitoring on-demand.

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link. Modified thymine bases, each containing a polymerizable group (either carboxymethylvinyl or acrylamide) at the 5-position, have been incorporated multiple times into an aptamer sequence allowing the sequence to act as the key recognition element in an aptamer-molecularly imprinted polymer (MIP) hybrid nanoparticle (aptaMIP NP) system for the molecular recognition of the antibiotic moxifloxacin. These materials combine the recognition properties of an aptamer, with the robustness and stability of a MIP, offering a “best-of-both-worlds” approach. Both aptaMIP nanoparticles offer 10-fold superior binding affinity and selectivity over conventional MIP nanoparticles (nanoMIPs), with KD values of 3.65 × ±0.9 nM, 5.72 ± 0.6 nM and 48.60 ± 7.0 nM for the carboxy aptaMIP, acrylamide aptaMIP and nanoMIP, respectively; and 100-fold superior affinity compared to the unfunctionalized aptamer only (0.325 ± 0.16 μM), all with excellent selectivity for the template antibiotic. When applied to a sensor platform (Surface Plasmon Resonance), the limit of detection based on the aptaMIP nanoparticles was approximately three-fold lower (0.51 nM and 0.56 nM for the carboxy aptaMIP and acrylamide aptaMIP, respectively) compared to the nanoMIP (1.4 nM). The introduction of the aptamer as a “macro-monomer” into the imprinted polymer scaffold is a promising strategy for significantly improving the properties of both components of the hybrid material (aptamer and MIP). These hybrid polymers, bearing nucleic acid recognition materials offer a powerful tool for robust high affinity selective molecular recognition.

Glycans - simple or complex carbohydrates - play key roles as recognition determinants and modulators of numerous physiological and pathological processes. Thus, many biotechnological, diagnostic and therapeutic opportunities abound for molecular recognition entities that can bind glycans with high selectivity and affinity. This review begins with an overview of the current biologically and synthetically derived glycan-binding scaffolds that include antibodies, lectins, aptamers and boronic acid-based entities. It is followed by a more detailed discussion on various aspects of their generation, structure and recognition properties. It serves as the basis for highlighting recent key developments and technical challenges that must be overcome in order to fully deal with the specific recognition of a highly diverse and complex range of glycan structures.

Precise macromolecular recognition and self-sorting are essential in biological systems to maintain life. Herein, we report the self-assembly between one single dendritic macromolecule with discrete molecular weight and one single gold nanoparticle (Au NP) during the in situ growth of the Au NP. This process resembles an artificial, organic, and soft nanohand picking up a growing inorganic hard nanoparticle of a particular size (∼1.4 nm). Discrete 1 : 1 organic–inorganic hybrid nanostructures based on four finger-like dendritic macromolecules with different anchors have been investigated with their ability to wrap up a Au NP of different sizes. Both experimental and theoretical studies demonstrate that the dendrons with different anchoring groups can control the nucleation and growth, and stabilized the sizes of Au NPs. These results highlight the importance of the dendron's anchoring groups in the gold nucleation step before the small gold cluster grows into a Au NP and is then firmly wrapped within the whole dendron. These results provide the fundamental understanding of soft nanomachinery on sorting out nanosized products of particular size and shape.

Label-free protein characterization at surfaces is commonly achieved using digestion and/or matrix application prior to mass spectrometry. We report the assignment of undigested proteins at surfaces in situ using secondary ion mass spectrometry (SIMS). Ballistic fragmentation of proteins induced by a gas cluster ion beam (GCIB) leads to peptide cleavage producing fragments for subsequent OrbitrapTM analysis. In this work we annotate 16 example proteins (up to 272 kDa) by de novo peptide sequencing and illustrate the advantages of this approach by characterizing a protein monolayer biochip and the depth distribution of proteins in human skin., Label-free protein characterization at surfaces requires digestion or matrix application prior to mass spectrometry. Here, the authors report the assignment of undigested proteins at surfaces by de novo sequencing and apply the methodology to a protein monolayer biochip and for in situ depth profiling of proteins through human skin.

Calcium phosphates are used widely as orthopaedic implants and in nanocrystalline form to enable the transfer of genetic material into cells. Despite widespread use, little is known about their fate after they have crossed the cell membrane. Here we present a method of surface modification of silicon-substituted hydroxyapatite (SiHA) through a silane group, which enables the engraftment of a fluorescent dye to facilitate real-time biological tracking. Surface modification of the nanocrystal surface was undertaken using (3-mercaptopropyl)trimethoxysilane (MPTS), which presented a thiol for the further attachment of a fluorophore. Successful modification of the surface was demonstrated using zeta potential measurements and fluorescence microscopy and the number of thiol groups at the surface was quantified using Ellman's reagent. In vitro experiments using the fluorescently modified particles enabled the discrimination of the calcium phosphate particulate from other biological debris following internalisation by a population of MC3T3 (pre-osteoblast) cells and the particles were shown to maintain fluorescence for 24 hours without quenching. The successful modification of the surface of SiHA with thiol groups offers the tantalising possibility of the intracellular growth factor delivery.

Correction for ‘The challenges of glycan recognition with natural and artificial receptors’ by Stefano Tommasone et al., Chem. Soc. Rev., 2019, 48, 5488–5505.

The reference cantilever method is shown to act as a direct and simple method for determination of torsional spring constant. It has been applied to the characterization of micropaddle structures similar to those proposed for resonant functionalized chemical sensors and resonant thermal detectors. It is shown that this method can be used as an effective procedure to characterize a key parameter of these devices and would be applicable to characterization of other similar MEMS/NEMS devices such as micromirrors. In this study, two sets of micropaddles are manufactured (beams at centre and offset by 2.5 μm) by using LPCVD silicon nitride as a substrate. The patterning is made by direct milling using focused ion beam. The torsional spring constant is achieved through micromechanical analysis via atomic force microscopy. To obtain the gradient of force curve, the area of the micropaddle is scanned and the behaviour of each pixel is investigated through an automated developed code. The experimental results are in a good agreement with theoretical results.

The commercialisation of polymer electrolyte fuel cells (PEFCs) has been hampered by the high cost of platinum metal. Due to its high durability and catalytic activity, platinum is widely used to catalyse the oxygen reduction and hydrogen oxidation reactions essential to the operation of these cells. Core@shell nanoparticles with thin layers of platinum deposited on cores composed of cheaper materials have offered an attractive route towards the reduction of overall loading of platinum, with the retention of active catalyst surface area. This review surveys approaches taken to prepare idealised active and durable core@shell nanocatalysts by tweaking core compositions. A critical reflection on the current status of the field, as well as predictions as to likely directions for future developments, are discussed as a conclusion to the review.

Die wichtige Rolle von Vesikeln in vielen Bereichen der Zellfunktion ist gut bekannt, aber erst seit kurzem offenbart sich mithilfe neuer, komplexerer Bildgebungsverfahren ihre Allgegenwart in der Natur. Wahrend die biologischen Eigenschaften von Vesikeln und ihre physiologischen Funktionen immer besser verstanden werden, werden auch vermehrt sehr elegante, kunstliche Vesikel fur eine Reihe technischer Anwendungen und die Grundlagenforschung entwickelt. Hier wollen wir den Stand der Technik von biologischen und synthetischen Vesikeln darstellen und ihre biologischen Eigenschaften in Zusammenhang mit aktuellen Syntheseentwicklungen bringen, um so einen Uberblick uber diese komplexen, rasch aufstrebenden Fachgebiete zu geben. Daruber hinaus werden die Herausforderungen und Moglichkeiten fur die zukunftige biologische und praparative Entwicklung von Vesikeln prasentiert.

The synthesis of a novel modified nucleoside phosphoramidite, Acrylamide-dT-CE phosphoramidite, obtained in three steps from commercially available starting materials, is reported. It was readily incorporated into thrombin binding aptamer (TBA) sequences using automated solid-phase synthesis under ultra-mild conditions, with the modification shown not to adversely affect duplex stability, G-quadruplex structure, or thrombin binding. The reaction and integration of the modified strands with acrylamide polymers was evidenced by gel electrophoresis. The Acrylamide-dT functional handle promises to be an ideal synthon for preparing DNA–polymer hybrids for use in various macromolecular materials applications.

[Image: see text] Since glycoproteins have become increasingly recognized as key players in a wide variety of disease processes, there is an increasing need for advanced affinity materials for highly selective glycoprotein binding. Herein, for the first time, a surface-initiated controlled radical polymerization is integrated with supramolecular templating and molecular imprinting to yield highly reproducible synthetic recognition sites on surfaces with dissociation constants (K(D)) in the low micromolar range for target glycoproteins and minimal binding to nontarget glycoproteins. Importantly, it is shown that the synthetic strategy has a remarkable ability to distinguish the glycosylated and nonglycosylated forms of the same glycoprotein, with a >5-fold difference in binding affinity. The precise control over the polymer film thickness and positioning of multiple carbohydrate receptors plays a crucial role in achieving an enhanced affinity and selectivity. The generated functional materials of unprecedented glycoprotein recognition performance open up a wealth of opportunities in the biotechnological and biomedical fields.

The ability to design surfaces with reversible, high-affinity protein binding sites represents a significant step forward in the advancement of analytical methods for diverse biochemical and biomedical applications. Herein, we report a dynamic supramolecular strategy to directly assemble proteins on surfaces based on multivalent host–guest interactions. The host–guest interactions are achieved by one-step nanofabrication of a well-oriented β-cyclodextrin host-derived self-assembled monolayer on gold (β-CD-SAM) that forms specific inclusion complexes with hydrophobic amino acids located on the surface of the protein. Cytochrome c, insulin, α-chymotrypsin, and RNase A are used as model guest proteins. Surface plasmon resonance and static time-of-flight secondary ion mass spectrometry studies demonstrate that all four proteins interact with the β-CD-SAM in a specific manner via the hydrophobic amino acids on the surface of the protein. The β-CD-SAMs bind the proteins with high nanomolar to single-digit micromolar dissociation constants (KD). Importantly, while the proteins can be captured with high affinity, their release from the surface can be achieved under very mild conditions. Our results expose the great advantages of using a supramolecular approach for controlling protein immobilization, in which the strategy described herein provides unprecedented opportunities to create advanced bioanalytic and biosensor technologies.

The current study investigated the unique combination of alloying (Pt with Cr) and Nafion stabilisation to reap the benefits of catalyst systems with enhanced catalytic activity and improved durability in PEMFCs. Pt–Cr alloy nanoparticles stabilised with Nafion were chosen in the current study owing to their higher stability in acidic and oxidising media at high temperatures compared to other Pt-transition metal alloys (e.g. Pt–Ni, Pt–Co). Two different precursor : reducing agent (1 : 10 and 1 : 20) ratios were used in order to prepare two different alloys, denoted as Pt–Cr 10 and Pt–Cr 20. The Pt–Cr 20 alloy system (with composition Pt80Cr20) demonstrated higher electrocatalytic activity for the oxygen reduction reaction compared to commercial Pt/C (TKK) catalysts. Accelerated stress tests and single cell tests revealed that Nafion stabilised alloy catalyst systems displayed significantly enhanced durability (only ∼20% loss of ECSA) compared with Pt/C (50% loss of ECSA) due to improved catalyst–ionomer interaction. Furthermore, the Pt–Cr 20 alloy system demonstrated a current density comparable to that of Pt/C making them promising potential electrocatalysts for proton exchange membrane fuel cells.

Recognition of oligosaccharides is associated with very limited specificity due to their strong solvation in water and the high degree of subtle structural variations between them. Here, oligosaccharide recognition sites are created on material surfaces with unmatched, binary on–off binding behavior, sharply discriminating a target oligosaccharide over closely related carbohydrate structures. The basis for the superselective binding behavior relies on the highly efficient generation of a pure, high order complex of the oligosaccharide target with synthetic carbohydrate receptor sites, in which the spatial arrangement of the multiple receptors in the complex is preserved upon material surface incorporation. The synthetic binding scaffolds can easily be tailored to recognize different oligosaccharides and glycoconjugates, opening up a realm of possibilities for their use in a wide field of applications, ranging from life sciences to diagnostics., A unique modular, synthetic strategy allows for the creation of artificial binding sites with precise spatial positioning of multiple carbohydrate receptors, enabling the remarkable ability to distinguish a target oligosaccharide over closely related carbohydrate structures. The synthetic binding scaffolds can easily be tailored to bind not only specifically oligosaccharides in free form but also when they are linked to proteins as glycoconjugates.

In nature, interfacial molecular interactions are at the heart of all biological processes and are mediated by diverse stimuli. Inspired by nature's responsive mechanisms and our increased capability to manipulate matter at the molecular level, new bio-interface materials are being developed that respond efficiently to a variety of external stimuli. In this Review, we discuss emerging methods for imparting surfaces with dynamic properties and how this, in turn, is leading to increased functional complexity at the bio-interface. We examine how recent advances are becoming important in providing new insights into cell behaviour and spurring substantial progress in the fields of regenerative medicine and tissue engineering. These advances provide new opportunities to address the complex issues associated with biofouling and facilitate the production of implantable on-demand sensing devices and highly effective delivery, bioseparation and bioelectrocatalytic systems. Although progress is being made, we also highlight that current methods are still limited in their capability to impart complex functionality onto the bio-interface to fully address the current challenges in biotechnology and biomedicine. Exciting prospects include the incorporation of full reversibility of interactions, a broad repertoire of multi-responsiveness and bidirectional actuation at the bio-interface, as well as the capability to incorporate the developed systems in practical applications. Bio-interface materials inspired by natural systems that respond efficiently to various external stimuli can dynamically regulate molecular interactions between biological entities and material surfaces. In this Review, Gomes and colleagues describe advances in bio-interface materials that may provide insights into cell behaviour, biofouling and the production of on-demand devices with medical applications, among others.

Herein, we report a highly sensitive electrocatalytic sensor-cell construct that can electrochemically communicate with the internal environment of immune cells (e.g., macrophages) via the selective monitoring of a particular reactive oxygen species (ROS), hydrogen peroxide. The sensor, which is based on vertically aligned single-walled carbon nanotubes functionalized with an osmium electrocatalyst, enabled the unprecedented detection of a local intracellular “pulse” of ROS on a short second time scale in response to bacterial endotoxin (lipopolysaccharide-LPS) stimulation. Our studies have shown that this initial pulse of ROS is dependent on NADPH oxidase (NOX) and toll like receptor 4 (TLR4). The results suggest that bacteria can induce a rapid intracellular pulse of ROS in macrophages that initiates the classical innate immune response of these cells to infection.

Under the exerted external electric field (Eex), significant polarization effects are demonstrated in the switching process of positively charged oligopeptide chains on the gold surface by using the polarizable force-field-based molecular dynamics (MD) simulations. The changes of electrostatic environment during the conformational switching are described by calling density functional theory (DFT) calculations of atomic charges or fragment-centered dipole moments. The charge-variable polarizable force field (Q-POL) model shows a good agreement with the experimental observations of both the open-circuit state (OC) without Eex and extended/bent conformation (ON/OFF) with upward/downward Eex, while the nonpolarizable force field (Non-POL) with the fixed atomic partial charges fails to reproduce experiments for the ON state. The charged oligopeptide chains (with each residue furnished with a positive charge) challenge the application of the coarse-graining polarizable force field based on the fragment dipoles ...

Layered core-shell bimetallic Cr-Pt nanoparticles were prepared by the formation and later reduction of an intermediate Pt-ion-containing supramolecular complex onto preformed Cr nanoparticles. The resultant nanoparticles were characterized by X-ray diffraction analysis, transmission electron microscopy, X-ray photoelectron spectroscopy, and aberration-corrected scanning transmission electron microscopy. The results are consistent with the presence of Pt diffusion during or after bimetallic nanoparticle formation, which has resulted in a Pt/Cr-alloyed core and shell. We postulate that such Pt diffusion occurs by an electric-field-assisted process according to Cabrera-Mott theory and that it originates from the low work function of the preformed oxygen-defective Cr nanoparticles and the rather large electron affinity of Pt.

Many glycoproteins are intimately linked to the onset and progression of numerous heritable or acquired diseases of humans, including cancer. Indeed the recognition of specific glycoproteins remains a significant challenge in analytical method and diagnostic development. Herein, a hierarchical bottom-up route exploiting reversible covalent interactions with boronic acids and so-called click chemistry for the fabrication of glycoprotein selective surfaces that surmount current antibody constraints is described. The self-assembled and imprinted surfaces, containing specific glycoprotein molecular recognition nanocavities, confer high binding affinities, nanomolar sensitivity, exceptional glycoprotein specificity and selectivity with as high as 30 fold selectivity for prostate specific antigen (PSA) over other glycoproteins. This synthetic, robust and highly selective recognition platform can be used in complex biological media and be recycled multiple times with no performance decrement.

The fabrication of a molecularly tailored surface functionalised with a saccharide binding motif, a phenyl boronic acid derivative is reported. The functionalised surface facilitated the transfer of electrons, via unique electronic interactions mediated by the presence of the boronic acid, from a macrophage cell line. This is the first example of eukaryotic cellular-electrical communication mediated by the binding of cells via their cell–surface saccharide units.

All organisms respond to vibration and bacteria are no exception. Previous studies showed that bacteria cells respond to vibrational cues, but the precise mechanisms of adhesion and growth in such conditions are still poorly explored. This work aims to unravel the mechanisms underlying bacterial adhesion to surfaces by investigating how vibrational environments influence bacterial behavior. To answer such questions, substrates based on the piezoelectric polymer Polyvinylidene Fluoride (PVDF) are used.

Reported herein is a switchable surface that relies on electrically-induced conformational changes within surface-grafted arginine–glycine–aspartate (RGD) oligopeptides as the means of modulating cell adhesion.

Herein, electrically switchable mixed self-assembled monolayers based on oligopeptides have been developed and investigated for their suitability in achieving control over biomolecular interactions in the presence of complex biological conditions. Our model system, a biotinylated oligopeptide tethered to gold within a background of tri(ethylene glycol) undecanethiol, is ubiquitous in both switching specific protein interactions in highly fouling media while still offering the non-specific protein-resistance to the surface. Furthermore, the work demonstrated that the performance of the switching on the electro-switchable oligopeptide is sensitive to the characteristics of the media, and in particular, its protein concentration and buffer composition, and thus such aspects should be considered and addressed to assure maximum switching performance. This study lays the foundation for developing more realistic dynamic extracellular matrix models and is certainly applicable in a wide variety of biological and medical applications.

The important role of vesicles in many aspects of cell function is well-recognized, but only recently have sophisticated imaging techniques begun to reveal their ubiquity in nature. While we further our understanding of the biological properties of vesicles and their physiological functions, increasingly elegant artificial vesicles are being developed for a wide range of technological applications and basic research. Herein, we examine the state of the art of biological and synthetic vesicles and place their biological features in the context of recent synthetic developments, thus providing a unique overview of these complex and rapidly developing fields. The challenges and opportunities associated with future biological and synthetic studies of vesicles are also presented.

Conspectus Stimuli-responsive surfaces have sparked considerable interest in recent years, especially in view of their biomimetic nature and widespread biomedical applications. Significant efforts are continuously being directed at developing functional surfaces exhibiting specific property changes triggered by variations in electrical potential, temperature, pH and concentration, irradiation with light, or exposure to a magnetic field. In this respect, electrical stimulus offers several attractive features, including a high level of spatial and temporal controllability, rapid and reverse inducement, and noninvasiveness. In this Account, we discuss how surfaces can be designed and methodologies developed to produce electrically switchable systems, based on research by our groups. We aim to provide fundamental mechanistic and structural features of these dynamic systems, while highlighting their capabilities and potential applications. We begin by briefly describing the current state-of-the-art in integrating electroactive species on surfaces to control the immobilization of diverse biological entities. This premise leads us to portray our electrically switchable surfaces, capable of controlling nonspecific and specific biological interactions by exploiting molecular motions of surface-bound electroswitchable molecules. We demonstrate that our self-assembled monolayer-based electrically switchable surfaces can modulate the interactions of surfaces with proteins, mammalian and bacterial cells. We emphasize how these systems are ubiquitous in both switching biomolecular interactions in highly complex biological conditions while still offering antifouling properties. We also introduce how novel characterization techniques, such as surface sensitive vibrational sum-frequency generation (SFG) spectroscopy, can be used for probing the electrically switchable molecular surfaces in situ. SFG spectroscopy is a technique that not only allowed determining the structural orientation of the surface-tethered molecules under electroinduced switching, but also provided an in-depth characterization of the system reversibility. Furthermore, the unique support from molecular dynamics (MD) simulations is highlighted. MD simulations with polarizable force fields (FFs), which could give proper description of the charge polarization caused by electrical stimulus, have helped not only back many of the experimental observations, but also to rationalize the mechanism of switching behavior. More importantly, this polarizable FF-based approach can efficiently be extended to light or pH stimulated surfaces when integrated with reactive FF methods. The interplay between experimental and theoretical studies has led to a higher level of understanding of the switchable surfaces, and to a more precise interpretation and rationalization of the observed data. The perspectives on the challenges and opportunities for future progress on stimuli-responsive surfaces are also presented.

Understanding how bacteria adhere to a surface is a critical step in the development of novel materials and coatings to prevent bacteria forming biofilms. Here, surface plasmon resonance (SPR) spectroscopy, in combination with self-assembled monolayers (SAMs) that have different backbone structures and/or functional groups, is used for the first time to study the initial stages of bacterial adhesion to surfaces (i.e., initial interaction of cells with a surface, a process governed by van der Waals, electrostatic, and hydrophobic interactions). The work highlights SPR spectroscopy as a powerful and unique approach to probe bacterial adhesion in real time. SPR spectral data reveal different kinetics of adhesion for the interaction of two marine bacterial species (Marinobacter hydrocarbonoclasticus and Cobetia marina) to a range of organosulfur SAMs. Furthermore, the extent of adhesion is dependent on the backbone structures and functional groups of the SAMs. The role of extracellular polymeric substances (EPS) in bacterial adhesion is also investigated. Pre-conditioning experiments with cell-free culture supernatants, containing planktonic EPS, allow quantification of the amount adsorbed onto surfaces and directly account for the impact of EPS adsorption on bacterial adhesion in the assay. While the physicochemical characteristics of the surfaces play a significant role in determining bacterial cell adhesion for low levels of conditioning by planktonic EPS, greater levels of conditioning by EPS reduce the difference between surfaces.

The ability to monitor intracellular events in real time is paramount to advancing fundamental biological and clinical science. We present the first demonstration of a direct interface of vertically aligned single-walled carbon nanotubes (VASWCNTs) with eukaryotic cells, RAW 264.7 mouse macrophage cell line. The cells were cultured on indium tin oxide with VASWCNTs. VASWCNTs entered the cells naturally without application of any external force and were shown to sense the intracellular presence of a redox active moiety, methylene blue. The technology developed provides an alluring platform to enable electrochemical study of an intracellular environment.

Regardless of the institution or discipline, the UK’s National Student Survey (NSS) has consistently highlighted that the level of student satisfaction about the feedback they receive is notably lower than for other aspects of their learning experience. This study explored how students understand concepts and practices rated through NSS questions evaluating feedback practices in higher education. Drawing on questionnaires completed by first, third and fourth year Chemical Engineering students, the study calls into particular question the reliability of NSS data on promptness of feedback. In conclusion, it calls for greater attention to be paid at institutional level to the identification and management of students’ perceptions and expectations of the process, content and outcomes of feedback.

The degradation behavior of Pt/C electrocatalysts derived from Nafion®-stabilized colloidal Pt was found to be dependent on their morphology. Catalysts having agglomerated Pt particles showed significantly enhanced durability compared with those having well-dispersed Pt, and compared with a commercial (E-Tek) Pt/C catalyst. It is proposed that the preparation route starting from Nafion®-stabilized colloidal Pt results in a highly-effective distribution of Nafion® within the catalyst layer, which enhances durability via inhibition of particle growth mechanisms.

A Pt/C electrocatalyst was prepared from colloidal Pt nanoparticles stabilised by Nafion. This electrocatalyst was found to exhibit negligible degradation under a potential cycling regime conducted on a model thin-film catalyst layer in a 3-electrode cell set-up, in which an E-Tek Pt/C commercial catalyst showed a 23% loss of specific electrochemical surface area (SECSA). The enhanced durability of the Nafion-derived is thought to arise from the protection of Pt particles against dissolution and sintering by the surrounding Nafion layer. The use of the ionomer phase as a protective agent in the catalyst layer presents a novel strategy for the production of more durable Pt/C catalysts for the Proton Exchange Membrane Fuel Cell (PEMFC), which currently presents a significant challenge for the commercialisation of this technology. Keywords: PEMFC, Fuel cell, Pt/C, Nafion, Platinum, Electrocatalyst, Durability