Electroanalytic Aspects of Single‐Entity Collision Methods for Bioanalytical and Environmental Applications

Abstract

entity electrochemistry based on measurements of collision events at electrode surfaces is a rapidly developing field which provides extensive capabilities for detection and characterization of a variety of materials including organic and inorganic nanoparticles (NPs) and nanostructures as well as biologicals. The method has demonstrated promising potential for the analysis of catalytic activity, physicochemical parameters, fundamental surface properties, functionalization and reactivity of NPs. Here, the most recent developments and capabilities of this method as a novel tool for characterizing nanoscale properties are discussed, illustrating novel applications for assessing bioconjugation, designing ultrasensitive biosensing methods and monitoring processes of biological and environmental significance. The main advantages and limitations as compared to commonly used spectroscopy and imaging techniques are described, highlighting areas in which collision measurements can be used as a complementary approach to characterize properties of inorganic NPs, organic molecules, soft materials and biologicals, and develop methodologies for detection and quantification of analytes of interest in the bioanalytical, biological and environmental fields. An overview of potential applications in these fields is provided along with a critical discussion of future research needs and opportunities.

Lipid Membrane Permeability of Synthetic Redox DMPC Liposomes Investigated by Single Electrochemical Collisions

“…[35][36][37][38][39][40][41] Especially, the electrochemical detection of single liposome collisions at UMEs is becoming an efficient and complementary tool for analyzing fundamental biological processes related to intracellular and extracellular electron transfers to discrete biological or artificial entities. [42][43][44] To explore the factors influencing the vesicles membrane permeability, we investigated the electrochemical and electrocatalytic reaction of different aqueous redox species (potassium ferrocyanide and cobalt(II) nitrate) encapsulated inside synthetic DMPC (1,2dimyristoyl-sn-glycero-3-phosphocholine) liposomes subjected to different experimental conditions (addition of surfactant, increase of temperature or presence of a redox probe in solution), by single collision detection on 10 μm diameter UMEs (Pt and carbon) as illustrated in Figure 1. We discuss the effect of the solution temperature on the liposome collision, its membrane rupture, and subsequent electrolysis of its redox content.…”

“…Furthermore, it is well established that the liposome membrane stability is strongly dependent on its lipid composition and external parameters such as temperature and pH but also depends on interactions with specific molecules able to weaken, permeabilize, and penetrate the lipid bilayer following different pathways. − An understanding of these different interactions and especially the mechanism leading to the lipid membrane opening is still an active research field. To this end, chronoamperometry is a useful method to probe the liposomes membrane permeability and to understand vesicle fusion processes onto electrode surface. − Especially, the electrochemical detection of single liposome collisions at UMEs is becoming an efficient and complementary tool for analyzing fundamental biological processes related to intracellular and extracellular electron transfers to discrete biological or artificial entities. − …”

Collision-Based Electrochemical Detection of Lysozyme Aggregation

“…The SPCE technique measures single-impact events of a nano-entity colliding with the working microelectrode and monitoring current changes at a fixed potential value, which can be related to the size, coating, concentration, and redox state of that entity. 25 The method has been used to study a variety of entities including small inorganic NPs (e.g., Ag, Pt, and CeO 2 ), organics, 26 polymer capsules, 27 and biologicals. 28 We previously demonstrated that silver nanoparticles (AgNPs) are an effective electroactive probe for monitoring the structural characteristics of NP stabilizers and conformational changes of biological molecules assembling at their surface.…”

Engineering Electrostatic Repulsion of Metal Nanoparticles for Reduced Adsorption in Single-Impact Electrochemical Recordings

“…They offer, for instance, a clear distinction between the signal and background, a theoretical LOD of a single entity, and an increasing precision with recording time . Hence, stochastic electrochemistry-based sensors could open up entirely new opportunities and may provide calibration curves at subfemtomolar levels in the future. − Recently, various groups successfully applied the concepts of stochastic electrochemistry in environmental and biosensing applications. − Particularly in diagnostics, the early detection of very dilute disease markers is of outstanding interest. However, to apply stochastic electrochemistry as a reliable digital (bio)­sensor, several issues have to be addressed .…”