Functionalized carbon nanotube adsorption interfaces for electron transfer studies of galactose oxidase

Monolayer-Protected Gold Nanoparticles Functionalized with Halogen Bonding Capability─An Avenue for Molecular Detection Schemes

The use of functionalized nanoparticles (NPs) and their aggregation in the presence of a targeted analyte is a well-established molecular detection strategy predicated on harnessing specific molecular interactions to the NP periphery. Molecules able to specifically interact with the functionalized NPs alter the unique optical and electrochemical properties of the NPs as a function of interparticle spacing. While many intermolecular interactions have been successfully exploited in this manner in conjunction with aqueous NP systems, the use of non-aqueous NPs in the same capacity is significantly less explored. A fundamental interaction that has not been previously investigated in NP schemes is halogen bonding (XB). XB is an orthogonal, electrostatic interaction between a region of positive electrostatic potential (δ+) on a halogen atom (i.e., XB donor) and a negative (δ-) Lewis base (XB acceptor) molecule. To couple XB with NP systems, ligands featuring a molecular structure that promotes XB interactions need to be identified, optimized, and synthesized for subsequent attachment to NPs. Herein, density functional theory (DFT) and NMR techniques are used to identify a strong XB-donor moiety (-C₆F₄I) and a synthetic scheme for a thiolate ligand featuring that functionality is devised and executed with high purity/yield (78%). Ligand-exchange reactions allow functionalization of non-aqueous alkanethiolate-protected gold NPs or monolayer-protected clusters (MPCs) with the XB-donor ligands. Functionalized MPCs (f-MPCs), within both assembled films and in solution, are shown to engage in XB interactions with target XB-acceptor molecules. Molecular recognition events, including induced aggregation of the f-MPCs, are characterized with UV-vis spectroscopy, cyclic voltammetry, TEM imaging, and diffusion-ordered spectroscopy NMR with limits of detection of 50-100 nM for strong XB acceptors. While fundamental exploration of XB interactions is ongoing, this study represents a step toward utilizing XB within molecular detection schemes, an application with implications for supramolecular chemistry, forensic, and environmental chemical sensing.

Reconstituting electrical conduction in soft tissue: the path to replace the ablationist

Cardiac arrhythmias are a leading cause of morbidity and mortality in the developed world. A common mechanism underlying many of these arrhythmias is re-entry, which may occur when native conduction pathways are disrupted, often by myocardial infarction. Presently, re-entrant arrhythmias are most commonly treated with antiarrhythmic drugs and myocardial ablation, although both treatment methods are associated with adverse side effects and limited efficacy. In recent years, significant advancements in the field of biomaterials science have spurred increased interest in the development of novel therapies that enable restoration of native conduction in damaged or diseased myocardium. In this review, we assess the current landscape of materials-based approaches to eliminating re-entrant arrhythmias. These approaches potentially pave the way for the eventual replacement of myocardial ablation as a preferred therapy for such pathologies.

Amperometric Biosensors Based on Direct Electron Transfer Enzymes

The accurate determination of analyte concentrations with selective, fast, and robust methods is the key for process control, product analysis, environmental compliance, and medical applications. Enzyme-based biosensors meet these requirements to a high degree and can be operated with simple, cost efficient, and easy to use devices. This review focuses on enzymes capable of direct electron transfer (DET) to electrodes and also the electrode materials which can enable or enhance the DET type bioelectrocatalysis. It presents amperometric biosensors for the quantification of important medical, technical, and environmental analytes and it carves out the requirements for enzymes and electrode materials in DET-based third generation biosensors. This review critically surveys enzymes and biosensors for which DET has been reported. Single- or multi-cofactor enzymes featuring copper centers, hemes, FAD, FMN, or PQQ as prosthetic groups as well as fusion enzymes are presented. Nanomaterials, nanostructured electrodes, chemical surface modifications, and protein immobilization strategies are reviewed for their ability to support direct electrochemistry of enzymes. The combination of both biosensor elements-enzymes and electrodes-is evaluated by comparison of substrate specificity, current density, sensitivity, and the range of detection.

Current Use of Carbon-Based Materials for Biomedical Applications—A Prospective and Review

Among a large number of current biomedical applications in the use of medical devices, carbon-based nanomaterials such as graphene (G), graphene oxides (GO), reduced graphene oxide (rGO), and carbon nanotube (CNT) are frontline materials that are suitable for developing medical devices. Carbon Based Nanomaterials (CBNs) are becoming promising materials due to the existence of both inorganic semiconducting properties and organic π-π stacking characteristics. Hence, it could effectively simultaneously interact with biomolecules and response to the light. By taking advantage of such aspects in a single entity, CBNs could be used for developing biomedical applications in the future. The recent studies in developing carbon-based nanomaterials and its applications in targeting drug delivery, cancer therapy, and biosensors. The development of conjugated and modified carbon-based nanomaterials contributes to positive outcomes in various therapies and achieved emerging challenges in preclinical biomedical applications. Subsequently, diverse biomedical applications of carbon nanotube were also deliberately discussed in the light of various therapeutic advantages.

Using Surface Amide Couplings to Assemble Photocathodes for Solar Fuel Production Applications

A facile surface amide-coupling method was examined to attach dye and catalyst molecules to silatrane-decorated NiO electrodes. Using this method, electrodes with a push-pull dye were assembled and characterized by photoelectrochemistry and transient absorption spectroscopy. The dye-sensitized electrodes exhibited hole injection into NiO and good photoelectrochemical stability in water, highlighting the stability of the silatrane anchoring group and the amide linkage. The amide-coupling protocol was further applied to electrodes that contain a molecular proton reduction catalyst for use in photocathode architectures. Evidence for catalyst reduction was observed during photoelectrochemical measurements and via femtosecond-transient absorption spectroscopy demonstrating the possibility for application in photocathodes.

Capillary electrophoresis-integrated immobilized enzyme microreactor with graphene oxide as support: Immobilization of negatively charged L-lactate dehydrogenase via hydrophobic interactions

We report the first application of hydrophobic interaction between graphene oxide (GO) and negatively charged enzymes to fabricate CE-integrated immobilized enzyme microreactors (IMERs) by a simple and reliable immobilization procedure based on layer by layer assembly. L-lactate dehydrogenase (L-LDH), which is negatively charged during the enzymatic reaction, is selected as the model enzyme. Various spectroscopic techniques, including SEM, FTIR, and UV-vis are used to characterize the fabricated CE-IMERs, demonstrating the successful immobilization of enzymes on the negatively charged GO layer in the capillary surface. The IMER exhibits excellent repeatability with RSDs of inter-day and batch-to-batch less than 3.49 and 6.37%, respectively, and the activity of immobilized enzymes remains about 90% after five-day usage. The measured K_m values of pyruvate and NADH of the immobilized L-LDH are in good agreement with those obtained by free enzymes. The results demonstrate that the hydrophobic interactions and/or π-π stacking is significant between the GO backbone and the aromatic residues of L-LDH and favorable to fabrication of CE-integrated IMERs. Finally, the method is successfully applied to the determination of pyruvate in beer samples.

Overview of Carbon Nanotubes for Biomedical Applications

The unique combination of mechanical, optical and electrical properties offered by carbon nanotubes has fostered research for their use in many kinds of applications, including the biomedical field. However, due to persisting outstanding questions regarding their potential toxicity when considered as free particles, the research is now focusing on their immobilization on substrates for interface tuning or as biosensors, as load in nanocomposite materials where they improve both mechanical and electrical properties or even for direct use as scaffolds for tissue engineering. After a brief introduction to carbon nanotubes in general and their proposed applications in the biomedical field, this review will focus on nanocomposite materials with hydrogel-based matrices and especially their potential future use for diagnostics, tissue engineering or targeted drug delivery. The toxicity issue will also be briefly described in order to justify the safe(r)-by-design approach offered by carbon nanotubes-based hydrogels.