AbstractElectrode fouling is a phenomenon that can severely affect the analytical characteristics of a technique or a sensor, such as sensitivity, detection limit, reproducibility, and overall reliability. Electrode fouling generally involves the passivation of an electrode surface by a fouling agent that forms an increasingly impermeable layer on the electrode, inhibiting the direct contact of an analyte of interest with the electrode surface for electron transfer. Some potential fouling agents include proteins, phenols, amino acids, neurotransmitters, and other biological molecules. Various antifouling strategies have been reported to reduce or eliminate electrode fouling. Most antifouling strategies exploit a protective layer or barrier on an electrode substrate to prevent the fouling agent from reaching the electrode surface. Although such strategies can be quite effective, they are inappropriate for systems in which the analyte itself is also the fouling agent. In such cases, other strategies must be used, including electrode surface modification and electrochemical activation. In this review, recent strategies to minimise and efforts to overcome electrode fouling across a diverse range of analytes and fouling agents will be presented.

PACS numbers: 82.65.Dp, 82.70.Dd, 87.22.Bt.We explore the interplay of membrane curvature and nonspecific binding due to excluded-volume effects among colloidal particles inside lipid bilayer vesicles. We trapped submicron spheres of two different sizes inside a pear-shaped, multilamellar vesicle and found the larger spheres to be pinned to the vesicle's surface and pushed in the direction of increasing curvature. A simple model predicts that hard spheres can induce shape changes in flexible vesicles. The results demonstrate an important relationship between the shape of a vesicle or pore and the arrangement of particles within it.Entropic excluded-volume (depletion) effects are well known to lead to phase separation in the bulk of colloids and emulsions consisting of large and small particles with short-range repulsive interactions [1][2][3][4][5][6]. More recently, attraction of the large particles to flat, hard walls [7,8] and repulsion from step edges [9] have been demonstrated in binary hard-sphere mixtures. A key concept suggested in these papers is that the geometric features of the surface can create "entropic force fields" that trap, repel or induce drift of the larger particles. This mechanism is not limited to suspensions of micron-sized particles; it may play a role in "lock and key" steric interactions on smaller macromolecular length scales. For example, the shape of pores and liposomes inside cells is likely to affect the behavior of macromolecules confined within them [10].In this Letter, we present experimental results that demonstrate new entropic effects at surfaces. In particular, the behavior of particles confined within vesicles reveals quantitatively the striking effect of membrane curvature. We first discuss experiments probing the behavior of a microscopic sphere trapped inside a rigid, phospholipid vesicle. Adding much smaller spheres to the mixture changes the distribution of the larger sphere in a way that depends on the curvature of the vesicle wall (see Fig. 1(b) and (c)). The results are consistent with the depletion force theory and illustrate a new mechanism for the size-dependent arrangement of particles within pores. We then explore theoretically some consequences of replacing the rigid wall with a flexible one. The entropic curvature effects can overcome the membrane's stiffness, leading to a new mechanism for shape changes in vesicles.We first briefly review depletion effects in mixtures of microscopic hard spheres of two different sizes. Moving two of the larger spheres toward one another does not change their interaction energy (which is zero for hard spheres) but does increase the volume accessible to the other particles (Fig. 2). The resulting gain in entropy reduces the free energy of the system by (3/2)αφ S k B T [11,12]. Here, α is the ratio of large to small radii (R L /R S ), φ S is the small-sphere volume fraction, and k B T is Boltzmann's constant times the absolute temperature. This simple result relies on the approximation that the small spheres are a structurel...

A novel nanoparticle label capable of amplifying the electrochemical signal of DNA hybridization is fabricated by functionalizing poly(styrene‐co‐acrylic acid) microbeads with CdTe quantum dots. CdTe‐tagged polybeads are prepared by a layer‐by‐layer self‐assembly of the CdTe quantum dots (diameter = 3.07 nm) and polyelectrolyte on the polybeads (diameter = 323 nm). The self‐assembly procedure is characterized using scanning and transmission electron microscopy, and X‐ray photoelectron, infrared and photoluminescence spectroscopy. The mean quantum‐dot coverage is (9.54 ± 1.2) × 103 per polybead. The enormous coverage and the unique properties of the quantum dots make the polybeads an effective candidate as a functionalized amplification platform for labelling of DNA or protein. Herein, as an example, the CdTe‐tagged polybeads are attached to DNA probes specific to breast cancer by streptavidin–biotin binding to construct a DNA biosensor. The detection of the DNA hybridization process is achieved by the square‐wave voltammetry of Cd2+ after the dissolution of the CdTe tags with HNO3. The efficient carrier‐bead amplification platform, coupled with the highly sensitive stripping voltammetric measurement, gives rise to a detection limit of 0.52 fmol L−1 and a dynamic range spanning 5 orders of magnitude. This proposed nanoparticle label is promising, exhibits an efficient amplification performance, and opens new opportunities for ultrasensitive detection of other biorecognition events.