Controlling the spread of bacterial infectious diseases is a major public health issue, particularly in view of the pandemic of bacterial resistance to antibiotics. In this context, the detection and identification of pathogenic bacteria is a prerequisite for the implementation of control measures. Current reference methods are mainly based on culture methods, which generate a delay in obtaining a result and requires equipment. Consequently, focusing on the detection of the whole bacterium represents a very attractive alternative, since no culture is required. Several techniques have already been deployed to identify whole-cell bacteria. In recent decades, growing interest in nucleic acid aptamers has emerged as a viable alternative to antibodies as recognition elements, offering preferable stability, cost-efficiency, good specificity and affinity. This review explores current alternative methods for the detection of whole-cell bacteria, with particular emphasis on aptamer-based assays. These assays have shown promising results in various transduction mechanisms, including optical, electrochemical, and mechanical approaches, enhancing their versatility in different diagnostic platforms. The integration of aptamers in these detection methods offers rapid, sensitive, versatile and portable solutions for pathogen identification, positioning them as valuable tools in the fight against bacterial infections.

Mesoporous Silica Nanoparticles (MSNs) have been increasingly investigated as versatile drug delivery carriers. A particular challenge for the systemic use of MSNs lies in the control of their degradation, which has not been fully understood until now. We implemented standard dynamic light scattering (DLS) experiments and introduced a novel DLS technique in a confocal volume to track the dynamics of large-pore MSN degradation in situ. This unique DLS technique, which involves a small observation volume, was chosen for its ability to count particle by particle during the degradation process, a method that has not been commonly used in nanoparticle research. The experiments were performed in different media compositions at low particle concentrations, below the silica solubility limit. MSNs with large conical pores were prepared and studied as they offer the possibility to incorporate and release large-sized biomolecules. Large-pore MSNs followed a singular degradation mechanism following a stochastic-like behavior, a finding that challenges the common idea that all nanoparticles (NPs) degrade similarly and homogeneously over time. We showed that some NPs are observed intact over a prolonged period while most other NPs have already vanished or been transformed into swollen NPs. Thus, a heterogeneous degradation process occurs, while the total concentration of NPs undergoes an exponential decay. These large conical pores MSNs will be utilized as reliable biomolecule nanocarriers by predicting the factors underlying the NP hydrolytic stability.

A new analytical methodology, using capillary electrophoresis in indirect UV absorbance mode, is developed for the quantification of analytes in the absence of reference materials. The methodology allows the quantification of organic molecules and/or small ions, anionic or cationic, absorbing or not in the UV range, carrying either one or two electric charges. Two methods of data processing were compared. The first is based on the use of a dynamic simulator of electromigration, and the second uses the Kohlrausch regulating function combined with the electroneutrality equation. The experimental conditions presented in this work allow a precise quantification of anions having electrophoretic mobilities (μep) between -22.71 and -36.92 × 10-9 m2 V-1 s-1 and cations with μep between +30.59 and +63.60 × 10-9 m2 V-1 s-1 with percent relative errors lower than -5.52%. The effect of the integration errors on the reliability of the results is discussed in detail.

We introduced an aptamer switch design that relies on the ability of post-transition/transition metal ions to trigger, through their coordination to nucleobases, substantial DNA destabilization. In the absence of molecular target, the addition of one such metal ion to usual aptamer working solutions promotes the formation of an alternative, inert DNA state. Upon exposure to the cognate compound, the equilibrium is shifted towards the competent DNA form. The switching process was preferentially activated by metal ions of intermediate base over phosphate complexation preference (i.e. Pb2+ , Cd2+ ) and operated with diversely structured DNA molecules. This very simple aptamer switch scheme was applied to the detection of small organics using the fluorescence anisotropy readout mode. We envision that the approach could be adapted to a variety of signalling methods that report on changes in the surface charge density of DNA receptors.

Naturally occurring polymers (and their derivatives) such as polysaccharides and proteins are very popular chiral selectors in analytical sciences. In contrast, nucleic acids have received much less attention in the enantiomeric analysis field. However, some significant advances have been accomplished during the last thirty years. The present review covers these different contributions in the development of both chiral sensor and separation systems. They rely on the use of either nonspecific nucleic acid molecules or target-specific oligonucleotides. The main practical factors as well as the applicability features of the reported nucleic acid-based enantioselective tools are summarized. Some possible routes for improvement are also suggested.

Silicon bolometers for space and astronomy applications, fabricated in standard CMOS-SOI technology are now successfully used as cryogenic detectors working at very low temperature, typically in the range of 0.05 to 0.1 K.They feature a remarkably high electromagnetic absorption, high temperature sensitivity and low noise.However, the mechanical behavior of suspended silicon bolometers results from the fabrication process parameters and a good understanding of these mechanisms is necessary to better control their deformation.In this work, silicon bolometer pixels with a pitch of 1200 μm and 500 μm for millimeter-wave (mm-wave) polarization detection have been fabricated and their mechanical behavior is investigated at room temperature and cryogenic temperature.First, a mechanical model was developed based on simulated and experimental deformations at room temperature of multi-layer cantilever test structures with different Young's modulus and thickness (Ei, hi).The actual multi-layer suspended structures are modeled as an equivalent composite layer with an effective Young's modulus (Eeff), an effective thickness (heff) and residual stresses (σ0, σ1).The residual stress values are positive, corresponding to a tensile stress in the fabricated multilayer stack.The impact of the a-Si passivation thickness on the total stress is discussed.The equivalent model is used in the simulation of the full pixel structure and results in excellent agreement with optical measurements of the deflection at room temperature.At cryogenic temperatures, mechanical deformations can hardly be measured, so the mechanical behavior of a 500-µm pixel was simulated at 0.1 K assuming that tensile residual stresses coming from defects are independent on temperature, and a good mechanical stability of the pixel was obtained.The optical performance simulation of this 500-µm pixel is discussed and showed that the mechanical deformations result in a degradation of the Noise Equivalent Power (NEP) from 1.59x10 -18 to 1.05x10 -17 W/Hz 1/2 for an optical load of 6x10 -15 W at 0.1 K.

Titration methods are routinely used in the laboratories for the quantification of acids and bases, for the complexometric determination of metal ions and for the ion-pair titrations of drugs in pharmaceutical control. They also find application in a wide variety of chemical and biochemical studies. However, conventional titration methods (CTM) require large amounts of samples that are not always available. In absence of micro-titrator devices, the application of these methods for expensive samples and for small batch sizes is not possible. In this work, it was demonstrated that the commercial capillary electrophoretic apparatus (CEa) can be used, in a quick and easy way, for the end-point detection in a microtitration process. The proposed methodology exploits the change of the solutions conductivity during the titrations. The equivalent points can be easily located by plotting the change in electrical current as a function of the titrant volume added. More interestingly, only 1.1-1.5 mL of analyte solutions are required to establish the titration curves. The advantages and the limitations of the procedure are discussed in detail.

The inline coupling of the field-amplified sample injection (FASI) to Taylor dispersion analysis (TDA) was used to characterize low-UV absorbing carboxylated silica nanoparticles (cNPs). The hydrodynamic diameters (Dh) were measured by using a commercial capillary electrophoresis instrument. The proposed methodology did not require any complicated instruments or chromophoric dye to increase the detection sensitivity. A practical method based on a half-Gaussian fitting was proposed for the data processing. The results obtained by this method were compared with those derived from dynamic light scattering (DLS) and transmission electron microscopy (TEM) analyses. From these results, it appeared that the size derived by TDA is in excellent agreement with those measured by DLS and TEM, as demonstrated by stable nanoparticles with narrow size distributions. Intermediate precision relative standard deviations less than 5% were obtained by FASI-TDA. The effect of the FASI-induced cNP peak dispersion on the reliability of the results was discussed in detail.

We recently reported that a great variety of DNA oligonucleotides (ONs) used as chiral selectors in partial‐filling capillary electrophoresis (CE) exhibited interesting enantioresolution properties toward low‐affinity DNA binders. Herein, the sequence prerequisites of ONs for the CE enantioseparation process were studied. First, the chiral resolution properties of a series of homopolymeric sequences (Poly‐dT) of different lengths (from 5 to 60‐mer) were investigated. It was shown that the size increase‐dependent random coil‐like conformation of Poly‐dT favorably acted on the apparent selectivity and resolution. The base‐unpairing state constituted also an important factor in the chiral resolution ability of ONs as the switch from the single‐stranded to double‐stranded structure was responsible for a significant decrease in the analyte selectivity range. Finally, the chemical diversity enhanced the enantioresolution ability of single‐stranded ONs. The present work could lay the foundation for the design of performant ON chiral selectors for the CE separation of weak DNA binder enantiomers.

A novel electrokinetic preconcentration technique based on multiple isotachophoresis (M-ITP) realised in a micro-bored capillary to improve sensitivity for capillary electrophoresis with hydrodynamic injection was developed. The M-ITP operation relies on pressure-assisted pushing of a preconcentrated sample plug after the first ITP process back to the injection end of the capillary, followed by a large volume hydrodynamic injection prior to application of the second ITP step. This operational cycle was repeated as many times as desired with very good repeatability of the peak areas and peak heights at each ITP round (RSD less than 8%). Using imidazole and benzoate as models for cationic and anionic analytes, important insights into the mechanism of this electrokinetic preconcentration process with and without the presence of the electro-osmotic flow (EOF) at acidic and basic conditions were provided. Stacking of the benzoate ion, selected as one model analyte, in the presence of EOF and from a sample plug representing up to 300% of the total capillary length was successfully demonstrated. M-ITP was then demonstrated through the enrichment of the Aβ 1-40 amyloid peptide, considered as one of the biomarkers for biochemical diagnosis of Alzheimer's disease. Quantification of Aβ 1-40 down to 50nM with UV detection was made possible with 6 M-ITP cycles.

In this communication, we present a very simple strategy to focus covalently derivatized proteins for high sensitivity CE analysis by LIF detection. We demonstrated that the covalently tagged protein can be focused just by adding SDS at a concentration above the CMC in the derivatized sample. Under specific injection conditions, SDS concentration below the CMC is also sufficient to induce the focusing of the tagged protein. This method allows the quantification and detection of the covalently tagged protein in a narrow zone with an efficiency approaching 220 000 plates/m. Very good linearity was obtained for the ubiquitin in a concentration range of 2–25 μM.

Herein, we studied the chiral resolution properties of a repertoire of arbitrarily chosen DNA oligonucleotides (ON). Ten oligonucleotidic sequences characterized by diverse base compositions, sizes, and structural features, ranging from secondary structure-free homo-oligonucleotides to duplex, hairpin, and three-way junction architectures, were investigated as potential chiral selectors. Their enantioselective features were assessed by using ONs as running buffer additives in partial-filling capillary electrophoresis. It was shown that all the screened sequences displayed enantiodiscrimination capabilities toward small aromatic compounds. Under (sub)millimolar DNA concentration conditions, the combination of only three oligonucleotidic sequences provided the chiral resolution of around 20 racemates, including drugs, illegal drugs, amino-acids, and nucleosides. This work represents the first demonstration of such analyte selectivity spectrum for nucleic acid-based chiral separation tools.

Separation of closely related nanoparticles is still a challenging issue for the characterization of complex mixtures for industrial/research applications or regulatory purposes. In this work, the remarkable separating performances of CE were complemented with the absolute size-based determination provided by Taylor dispersion analysis (TDA) for the characterization of nanoparticle mixtures. The inline hyphenation of CE to TDA was successfully implemented for the baseline separation followed by a size-based characterization of a bimodal mixture containing two closely size-related nanolatexes (70nm and 56nm radii). A pixel sensor UV area imager providing three detection points along the capillary was used for a differential measurement of the peak broadening during the Taylor dispersion step. Comparison of this new technique with dynamic light scattering and hydrodynamic chromatography is also discussed.

(1,2-diamino-cyclohexane)Platinum(II) ((DACH)Pt) loaded polymeric micelles of poly(ethylene glycol-b-sodium glutamate) (PEG-b-PGlu) are currently studied as a potential candidate to replace oxaliplatin in the treatment of cancers with the aim to reduce side effects like cumulative peripheral distal neurotoxicity and acute dysesthesias. As for all synthetic polymeric drug delivery systems, the characterization of the (co)polymer precursors and of the final drug delivery system (polymeric micelles) is crucial to control the repeatability of the different batches and to get correlation between physico-chemical structure and biological activity. In this work, the use of capillary electrophoresis (CE) and related methods for the characterization of (DACH)Pt-loaded polymeric micelles and their precursor (PEG-b-PGlu copolymer) has been investigated in detail. The separation and quantification of residual PGlu homopolymer in the PEG-b-PGlu sample were performed by free solution capillary zone electrophoresis mode. This mode brought also information on the PEG-b-PGlu copolymer composition and polydispersity. It also permitted to monitor the decomposition of polymeric micelles in the presence of NaCl at room temperature. Interactions between PEG-b-PGlu unimers, on one hand, and polymeric micelles or surfactants, on the other hand, were studied by using the Micellar Electrokinetic Chromatography and Frontal Analysis Capillary Electrophoresis modes. Finally, weight-average hydrodynamic radii of the loaded polymeric micelles and of the PEG-b-PGlu unimers were determined by Taylor Dispersion Analysis (an absolute size determination method that can be easily implemented on CE apparatus).

We report an improved CE method to monitor in vitro the self‐assembly of monomeric amyloid β‐peptide (42 amino acids amyloid β‐peptide, Aβ1–42) and in particular the crucial early steps involved in the formation of the neurotoxic oligomers. In order to start the kinetics from the beginning, sample preparation was optimized to provide samples containing exclusively the monomeric form. The CE method was also improved using a dynamic coating and by reducing the separation distance. Using this method, the disappearance of the monomer as well as the progressive formation of four species during the self‐assembly process can now be monitored and quantified over time. The hydrodynamic radius of the species present at the initial kinetics step was estimated around 1.8 nm by Taylor dispersion analysis while SDS‐PAGE analyses showed the predominance of the monomer. These results confirmed that the Aβ1–42 species present at this initial time was the monomer. Methylene blue, an anti‐Alzheimer disease candidate, was then evaluated. In spite of an oligomerization inhibition, the enhanced disappearance of the Aβ1–42 monomer provoked by methylene blue was demonstrated for the first time. This method, allowing the monomeric and smallest oligomeric species to be monitored, represents a new accurate and precise way to evaluate compounds for drug discovery.

This manuscript describes a new analytical methodology that allows one to stop the apparent fluid flow in uncoated fused silica capillaries. This method, which requires neither capillary coating nor buffer additive, is based on the use of a 22% polyethylene oxide gel which is placed at the anodic end of the capillary. Its high viscosity precludes its penetration into the capillary and the apparent electro-osmotic pumping effect is stopped. To avoid sample depletion in the gel, the concentration of the background electrolyte in the gel has to be at least 10-fold higher than that of the background electrolyte. This method was applied to isotachophoretic experiments performed in unmodified silica capillaries and at high alkaline pHs. The sharpness of the zone boundaries was perfectly conserved. The separation voltages recorded during the isotachophoretic processes demonstrate a very good stability of the system preventing fluctuations of the analyte migration times between runs. This approach can be virtually applied at any pH value of the background electrolyte, in the presence of organic solvents or surfactants. Using this methodology, it has been possible to detect underivatized Amyloid-β peptide 1-40, one of the potential Alzheimer's disease biomarkers, at lower concentrations than ever previously achieved using UV detection.

Silver nanoparticles possess potent antibacterial properties and have extremely high affinities to radioiodine. For several applications, it is essential to anchor the nanoparticles to microparticles or solid surfaces to make them insoluble while retaining their unique properties. This current work is related to the design of anionic and cationic macroporous polymer microspheres based on poly(glycidyl methacrylate) (PGMA) obtained using a multistep swelling polymerisation. According to scanning electron microscopy, the microspheres were monodisperse in size and 4.2 μm in diameter. The presence of the carboxyl and amino groups in the PGMA-COOH and PGMA-NH2 microspheres was confirmed by FT-IR spectroscopy. Capillary electrophoresis (CE) and pressure-assisted capillary electrophoresis (PACE) were used to study the electrophoretic behaviour of both types of microparticles. The electrophoretic mobility of the microparticles was changed into ζ potential using Smoluchowski modelling. Finally, silver-containing microspheres were prepared by reducing silver nitrate in the presence of the microspheres, and they proved effective for scavenging radioiodide ions from a model medium.

Dendrigraft poly-L-lysine (DGL) are biomacromolecules of great interest for many applications including antibacterial activity, drug delivery systems, gene therapy and production of antibodies. As human serum albumin (HSA) is the most abundant serum protein, the study of interactions between these two compounds is crucial for the use of DGL in drug or gene delivery systems. The present work aims at determining the number of binding sites and the corresponding successive equilibrium constants between DGL of generation 3 (G3) and HSA in physiological conditions. To meet this end, continuous frontal analysis capillary electrophoresis (FACCE) and fluorescence spectroscopic methods were implemented and compared. FACCE was performed on a polycationic modified capillary in combination with a co-pressure that allowed for selectively introducing the free G3 from the G3/HSA mixtures. FACCE studies demonstrated that HSA has 2 binding sites with DGL G3 with the following successive constants K-1 = 31.2 x 10(3) M-1 and K-2 = 30.6 x 10(3) M-1. For a 1 g/L concentration in G3 and assuming a plasmatic HSA concentration of 40 g/L, these binding constants lead to only 5% free DGL in the medium. It was also shown that the interactions between G3 and HSA corresponded to a model of cooperative sites. These results are in good agreement with the presence of two negatively charged domains in the HSA. Good fitting of the fluorescence spectroscopy data was obtained using the equilibrium constants derived from FACCE. Nevertheless, due to the high number of fitting parameters, it was difficult to fit the fluorescence spectroscopic data independently of the results obtained by FACCE. (c) 2013 Elsevier B.V. All rights reserved.