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Raman spectroscopy is a non-destructive and label-free molecular identification technique capable of producing highly specific spectra with various bands correlated to molecular structure. Moreover, the enhanced detection sensitivity offered by surface-enhanced Raman spectroscopy (SERS) allows analyzing mixtures of related chemical species in a relatively short measurement time. Combining SERS with deep learning algorithms allows in some cases to increase detection and classification capabilities even further. The present study evaluates the potential of applying deep learning algorithms to SERS spectroscopy to differentiate and classify different species of bile acids, a large family of molecules with low Raman cross sections and molecular structures that often differ by a single hydroxyl group. Moreover, the study of these molecules is of interest for the medical community since they have distinct pathological roles and are currently viewed as potential markers of gut microbiome imbalances. A convolutional neural network model was developed and used to classify SERS spectra from five bile acid species. The model succeeded in identifying the five analytes despite very similar molecular structures and was found to be reliable even at low analyte concentrations.

Monitoring antibody response to SARS-CoV-2 is critical for assessing the humoral response, especially important considering the emergence of multiple SARS-CoV-2 variants of concern (VOCs).

SARS-CoV-2 variants of concern (VOCs) have emerged worldwide, with implications on the spread of the pandemic. Characterizing the cross-reactivity of antibodies against these VOCs is necessary to understand the humoral response of non-hospitalized individuals previously infected with SARS-CoV-2, a population that remains understudied. Thirty-two SARS-CoV-2-positive (PCR-confirmed) and non-hospitalized Canadian adults were enrolled 14–21 days post-diagnosis in 2020, before the emergence of the B.1.351 (also known as Beta), B.1.617.2 (Delta) and P.1 (Gamma) VOCs. Sera were collected 4 and 16 weeks post-diagnosis. Antibody levels and pseudo-neutralization of the ectodomain of SARS-CoV-2 spike protein/human ACE-2 receptor interaction were analyzed with native, B.1.351, B.1.617.2 and P.1 variant spike proteins. Despite a lower response observed for the variant spike proteins, we report evidence of a sustained humoral response against native, B.1.351, B.1.617.2 and P.1 variant spike proteins among non-hospitalized Canadian adults. Furthermore, this response inhibited the interaction between the spike proteins from the different VOCs and ACE-2 receptor for ≥ 16 weeks post-diagnosis, except for individuals aged 18–49 years who showed no inhibition of the interaction between B.1.617.1 or B.1.617.2 spike and ACE-2. Interestingly, the affinity (KD) measured between the spike proteins (native, B.1.351, B.1.617.2 and P.1) and antibodies elicited in sera of infected and vaccinated (BNT162b2 and ChAdOx1 nCoV-19) individuals was invariant. Relative to sera from vaccine-naïve (and previously infected) individuals, sera from vaccinated individuals had higher antibody levels (as measured with label-free SPR) and more efficiently inhibited the spike–ACE-2 interactions, even among individuals aged 18–49 years, showing the effectiveness of vaccination., Author correction published in volume 11, article number 22912 (2021), Nov. 19, 2021. DOI: 10.1038/s41598-021-02484-9

International audience; Hybrid dielectric−metal colloid nanoparticle heterostructures have recently attracted attention in both fundamentals and applications. In this paper, we developed a new approach based on mechanical grinding and chemical synthesis in order to obtain hybrid dielectric−metal nanoparticles. By increasing the amounts of the stabilizing agent (polyvinylpyrrolidone (PVP)), three different types of hybrid colloidal structures were obtained, Si/Au core−island, core−shell, and core−shell oligomers heterostructures, respectively. The obtained colloidal heterostructures were analyzed by dynamic light scattering (DLS) and scanning electron microscope (SEM) measurements. Moreover, the optical properties of hybrid nanostructure have been carefully studied. A splitting was observed in the extinction spectra of colloidal solutions for different Si/Au colloidal heterostructures compared to Si colloidal nanoparticles, attributed to the hybridization of plasmon. Thanks to photolitholographic and drop-cast deposition techniques on a substrate, we were able to locate the colloidal nanoparticles heterostructures and to measure the backward scattering spectra using single-particle dark-field scattering spectroscopy. To better understand scattering results, FDTD simulations of scattering cross-section and electric near-field distributions were performed. As is well-known, the scattering spectrum of the pristine Si core is dominated by electric and magnetic dipolar modes in the visible region. More importantly, the scattering spectra of Si/Au core−island and core−shell support several phenomena such as collective magnetic dipolar modes and multiple Fano lineshapes. Our finding highlights the potential of our dielectric−metal heterostructures as a platform for studying light−matter interactions at the nanoscale.

Prostate cancer affects thousands of men who undergo clinical screening tests every year. The main biomarker used for the diagnosis of prostate cancer, prostate specific antigen (PSA), presents limitations that justify investigating new biomarkers to improve reliability. Antibodies against the tumor-associated carbohydrate antigen (Tn), or TACA, develop early in carcinogenesis, making them an interesting alternative as a target for prostate cancer diagnostics. In this work, the Tn antigen was synthesized and immobilized on a surface plasmon resonance sensor coated with a polydopamine/polyethylene oxide mixed layer used both as an anchoring surface for Tn capture moieties and to minimize surface fouling. The sensor could be regenerated and reused at least 60 times without any significant loss in sensitivity. Anti-Tn antibodies were detected in the 0-10 nM concentration range with detection limits of 0.1 and 0.3 nM in spiked buffer solutions and diluted human blood serum samples, respectively. Finally, as a proof-of-concept, this carbohydrate-based sensor was used to successfully discriminate blood serum samples from prostate cancer-free and prostate cancer patients.

DNA hybridization phenomena occurring on solid supports are not understood as clearly as aqueous phase hybridizations and mathematical models cannot predict some empirically obtained results. Ongoing research has identified important parameters but remains incomplete to accurately account for all interactions. It has previously been shown that the length of the overhanging (dangling) end of the target DNA strand following hybridization to the capture probe is correlated to interactions with the complementary strand in solution which can result in unbinding of the target and its release from the surface. We have developed an instrument for real-time monitoring of DNA hybridization on spherical particles functionalized with oligonucleotide capture probes and arranged in the form of a tightly packed monolayer bead bed inside a microfluidic cartridge. The instrument is equipped with a pneumatic module to mediate displacement of fluid on the cartridge. We compared this system to both conventional (passive) and centrifugally-driven (active) microfluidic microarray hybridization on glass slides to establish performance levels for the detection of single nucleotide polymorphisms. The system was also used to study the effect of the dangling end's length in real-time when the immobilized target DNA is exposed to the complementary strand in solution. Our findings indicate that increasing the length of the dangling end leads to desorption of target amplicons from bead-bound capture probes at a rate approaching that of the initial hybridization process. Finally, bead bed hybridization was performed with Streptococcus agalactiae cfb gene amplicons obtained from randomized clinical samples, which allowed for identification of group B streptococci within 5–15 min. The methodology presented here is useful for investigating competitive hybridization mechanisms on solid supports and to rapidly validate the suitability of microarray capture probes.

There is a growing need for brighter luminescent materials to improve the detection and imaging of biomarkers. Relevant contexts include low-abundance biomarkers and technology-limited applications, where an example of the latter is the emerging use of smartphones and other nonoptimal but low-cost and portable devices for point-of-care diagnostics. One approach to achieving brighter luminescent materials is incorporating multiple copies of a luminescent material into a larger supra-nanoparticle (supra-NP) assembly. Here, we present a facile method for the preparation and immunoconjugation of supra-NP assemblies (SiO2@QDs) that comprised many quantum dots (QDs) around a central silica nanoparticle (SiO2 NP). The assembly was entirely driven by spontaneous affinity interactions between the constituent materials, which included imidazoline-functionalized silica nanoparticles, ligand-coated QDs, imidazole-functionalized dextran, and tetrameric antibody complexes (TACs). The physical and optical properties of the SiO2@QDs were characterized at both the ensemble and single-particle levels. Notably, the optical properties of the QDs were preserved upon assembly into supra-NPs, and single SiO2@QDs were approximately an order of magnitude brighter than single QDs and nonblinking. In proof-of-concept applications, including selective immunolabeling of breast cancer cells, the SiO2@QDs provided higher sensitivity and superior signal-to-background ratios whether using research-grade fluorescence microscopy or smartphone-based imaging. Overall, the SiO2@QDs are promising materials for enhanced bioanalysis and imaging.

Metal-enhanced fluorescence (MEF) is a powerful tool in the design of sensitive chemical sensors by improving brightness and photostability of target-responsive fluorophores. Compounding these advantages with the modest hardware requirements of fluorescence sensing compared to that of centralized elemental analysis instruments, thus expanding the use of MEF to the detection of low-level inorganic pollutants, is a compelling aspiration. Among the latter, monitoring mercury in the environment, where some of its species disseminate through the food chain and, in time, to humans, has elicited a broad research effort toward the development of Hg

We report the integration of surface plasmon resonance (SPR), cyclic voltammetry and electrochemiluminescence (ECL) responses to survey the interfacial adsorption and energy transfer processes involved in ECL on a plasmonic substrate. It was observed that a Tween 80/tripropylamine nonionic layer formed on the gold electrode of the SPR sensor, while enhancing the ECL emission process, affects the electron transfer process to the luminophore, Ru(bpy)32+ , which in turn has an impact on the plasmon resonance. Concomitantly, the surface plasmon modulated the ECL intensity, which decreased by about 40 %, due to an interaction between the excited state of Ru(bpy)32+ and the plasmon. This occurred only when the plasmon was excited, demonstrating that the optically excited surface plasmon leads to lower plasmon-mediated luminescence and that the plasmon interacts with the excited state of Ru(bpy)32+ within a very thin layer.

We report on the development of surface plasmon resonance (SPR) sensors and matching ELISAs for the detection of nucleocapsid and spike antibodies specific against the novel coronavirus 2019 (SARS-CoV-2) in human serum, plasma and dried blood spots (DBS). When exposed to SARS-CoV-2 or a vaccine against SARS-CoV-2, the immune system responds by expressing antibodies at levels that can be detected and monitored to identify the fraction of the population potentially immunized against SARS-CoV-2 and support efforts to deploy a vaccine strategically. A SPR sensor coated with a peptide monolayer and functionalized with various sources of SARS-CoV-2 recombinant proteins expressed in different cell lines detected human anti-SARS-CoV-2 IgG antibodies in clinical samples. Nucleocapsid expressed in different cell lines did not significantly change the sensitivity of the assays, whereas the use of a CHO cell line to express spike ectodomain led to excellent performance. This bioassay was performed on a portable SPR instrument capable of measuring 4 biological samples within 30 minutes of sample/sensor contact and the chip could be regenerated at least 9 times. Multi-site validation was then performed with in-house and commercial ELISA, which revealed excellent cross-correlations with Pearson's coefficients exceeding 0.85 in all cases, for measurements in DBS and plasma. This strategy paves the way to point-of-care and rapid testing for antibodies in the context of viral infection and vaccine efficacy monitoring.

SARS-CoV-2 variants of concern (VOCs) have emerged worldwide, with implications on the spread of the pandemic. Characterizing the cross-reactivity of antibodies against these VOCs is necessary to understand the humoral response of non-hospitalized individuals previously infected with SARS-CoV-2, a population that remains understudied. Thirty-two SARS-CoV-2-positive (PCR-confirmed) and non-hospitalized Canadian adults were enrolled 14-21 days post-diagnosis in 2020, before the emergence of the B.1.351 VOC (also known as Beta). Sera were collected 4 and 16 weeks post-diagnosis. Antibody levels and pseudo-neutralization of the ectodomain of SARS-CoV-2 spike protein/human ACE-2 receptor interaction were analyzed with native and B.1.351 variant spike proteins. Despite a lower response observed for the variant spike protein, we report evidence of a sustained humoral response against native and B.1.351 variant spike protein among non-hospitalized Canadian adults. Furthermore, this response inhibited the interaction between the spike protein variant of concern and ACE-2 receptor for ≥16 weeks post-diagnosis.

We report on the development of surface plasmon resonance (SPR) sensors and matching ELISAs for the detection of nucleocapsid and spike antibodies specific against the novel coronavirus 2019 (SARS-CoV-2) in human serum, plasma and dried blood spots (DBS). When exposed to SARS-CoV-2 or a vaccine against SARS-CoV-2, the immune system responds by expressing antibodies at levels that can be detected and monitored to identify the fraction of the population potentially immunized against SARS-CoV-2 and support efforts to deploy a vaccine strategically. A SPR sensor coated with a peptide monolayer and functionalized with various sources of SARS-CoV-2 recombinant proteins expressed in different cell lines detected human anti-SARS-CoV-2 IgG in the nanomolar range. Nucleocapsid expressed in different cell lines did not significantly change the sensitivity of the assays, whereas the use of a CHO cell line to express spike ectodomain led to excellent performance. This bioassay was performed on a portable SPR instrument capable of measuring 4 biological samples within 30 minutes of sample/sensor contact and the chip could be regenerated at least 9 times. Multi-site validation was then performed with in-house and commercial ELISA, which revealed excellent cross-correlations with Pearson’s coefficients exceeding 0.85 in all cases, for measurements in DBS and plasma. This strategy paves the way to point-of-care and rapid testing for antibodies in the context of viral infection and vaccine efficacy monitoring.

We report a surface plasmon resonance (SPR) sensor detecting nucleocapsid antibodies specific against the novel coronavirus 2019 (SARS-CoV-2) in undiluted human serum. When exposed to SARS-CoV-2, the immune system responds by expressing antibodies at levels that can be detected and monitored to identify the patient population immunized against SARD-CoV-2 and support efforts to deploy a vaccine strategically. A SPR sensor coated with a peptide monolayer and functionalized with SARS-CoV-2 nucleocapsid recombinant protein detected anti-SARS-CoV-2 antibodies in the nanomolar range. This bioassay was performed on a portable SPR instrument in undiluted human serum and results were collected within 15 minutes of sample/sensor contact. This strategy paves the way to point-of-care and label-free rapid testing for antibodies.

The synthesis of core-shell (Fe3O4@SiO2) magnetic nanoparticles (MNP) functionalized using a Schiff base ligand (bis(3-methoxysalicylaldehyde)-o-phenylenediimine; MeOSalophen) for uranium extraction is reported. Extractive performances with respect to pH, adsorption kinetics, chemical nature of the equilibration phase, and elemental selectivity were evaluated and a maximal adsorption capacity of 92 mg g−1 at pH 6 in presence of sulfate ions for an equilibration time of 4 h was determined. The functionalized MNP offer very high affinity for uranyl ion (Kd > 11,000 mL g−1) as well as a high degree of selectivity for this element over several metal ions present in leach liquors containing rare earth elements . While Th was also extracted with the functionalized MNP, equivalent extractive performances were achieved with the non-functionalized counterpart, suggesting that this element is most likely adsorbed on the surface of the silica coating layer. The Schiff base-functionalized core-shell nanoparticles also exhibited a high degree of reusability in the conditions tested.

A multifunctional nanosystem was synthesized to be used as a dual sensor of UV light and temperature. NaGdF4:Yb3+:Er3+ upconverting nanoparticles (UCNPs) were synthesized and coated with a silica shell to which a europium(III) complex was incorporated. The synthesis of NaGdF4 UCNPs was performed via thermal decomposition of lanthanide ion fluoride precursors in the presence of oleic acid. To achieve sufficient water dispersibility, the surface of the hydrophobic oleate-capped UCNPs in the hexagonal phase was modified by a silica coating through a modified Stober process through a reverse microemulsion method. An Eu(tta)3 (tta: thenoyltrifluoroacetonate) complex was prepared in situ at the silica shell. A dual-mode nanothermometer was obtained from a near infrared to visible upconversion fluorescence signal of Er3+ ions together with UV-excited downshifting emission from the Eu3+ complex. Measurements were recorded near the physiological temperature range (293–323 K), revealing excellent linearity (R2 > 0....

The development of rapid, accurate and affordable diagnostic tests is essential for screening the population in order to properly manage and control the spread of the COVID-19 pandemic caused by the novel coronavirus (SARS-CoV-2). Current diagnostic techniques rely on tests which are time-consuming, must be performed in a specialized laboratory, and are limited in terms of sensitivity and specificity to active infection. Therefore, they don’t provide any information on previous exposure to the virus. Optical biosensors have the potential to overcome the current limitations in diagnostic techniques for COVID-19. My research project aims to develop a new rapid and precise analytical method using surface plasmon resonance (SPR) to detect anti-SARS-CoV-2 antibodies directly in crude sample. The SPR biosensor used in this project is based on the Kretschmann configuration. When the polarized light travels from the higher refractive index medium to the lower refractive index medium, the total internal reflection occurs. This leads to the formation of evanescent waves which are responsible for the excitation of the surface plasmons. Changes in the refractive index of the sample solution vary the resonance wavelength. Therefore, the adsorption-desorption activities on the surface of the sensor can be analyzed by tracking the wavelength location of the SPR band over time. The SPR technique allows real-time and label-free detection of molecular interactions. It is also very sensitive, can reduce test time to minutes, and can be used at the point of care for infectious diseases. Serological test involves the direct quantification of antibodies by exposing them to the virus protein immobilized on the surface of the sensor. Antibodies to SARS-CoV-2 are produced by the immune system within days or even weeks after viral infection and remain at an elevated level for months. Many research works in the development and evaluation of coronavirus vaccines require antibody testing for characterization of the affinity and kinetics of the immune response during vaccine development. Therefore, the development of a robust method by using SPR for performing serological tests is necessary. In this project, the various analytical parameters are optimized in order to increase the specific interactions between SARS-CoV-2 proteins and human antibodies and to decrease the non-specific adsorptions of other proteins to ensure a sensitive and specific test. Different COVID-19 proteins, such as the Nucleocapsid, the S1 domain of the Spike, the RBD domain of the Spike and the complete Spike were immobilized on the gold surface functionalized with the peptides 3-MPA-LHDLHD-OH to detect animal antibodies raised against each protein in the buffer and human serum. In each case, the immobilization conditions, such as concentration, chemistry and pH were optimized and detection limits were calculated for each antibody of animal origin. Although the direct detection of antibodies worked well, the use of a secondary antibody improved the results significantly in human serum. The validation of tests with animal antibodies made it possible to move on to the next step, which consists in using this detection method with a first cohort of clinical samples provided by the Centre hospitalier de l’Université de Laval (CHUL) to validate my research work in a clinical setting.

Core-shell nanoparticles are versatile nanostructures that can be used as luminescent biosensing platforms in many nanotechnological developments. Ultraluminescent fluorescent gold core-shell nanoparticles based on Metal-Enhanced Fluorescence (MEF) were synthesized. The nanoparticles obtained were formed by 40.0 nm cores and variable silica spacer lengths. Silica spacer lengths from 6.0 to 25.0 nm were obtained. The plasmon maximal wavelength of the core-shell nanoparticles was shifted to a longer wavelength from a gold nanoparticle plasmon centered at 537.0 nm to 545.0 nm and 548 nm from 6.0 nm to 20.0 nm spacer length, respectively. The effect of the gold core on emission was evaluated by determination of Metal Enhanced Fluorescence enhancement factors (MEFEF), applying the sodium cyanide method for core leaching. We observed maximal MEFEF = 8.1 and 7.2 for 6.0 and 14.0 nm, respectively, and a significant decrease at longer silica spacer lengths. From nanoimaging by confocal fluorescence microscopy it was possible to detect ultraluminescent gold core-shell nanoparticle aggregates and obtain an MEFEF that can rise to 40. These parameters and properties were discussed from the point of view of fluorescent platform applications. Moreover in order to show the potential application of these nanoparticles in biodetection and nanomedicine, Escherichia coli bacteria were labelled with ultraluminescent nanoparticles. Bright and clear bacteria images were obtained by laser fluorescence microscopy. Based on these results, future applications for individual bacterial detection will be developed. Fil: Gontero, Daniela Ivana. Clínica de la Familia II. Laboratorio de Análisis Clínicos y Bacteriológicos; Argentina Fil: Veglia, Alicia Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina Fil: Bracamonte, Angel Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina Fil: Boudreau, Denis. Universite Laval; Francia

The internal structure of hollow AgAu nanorods created by partial galvanic replacement was manipulated reversibly, and its effect on optical properties was mapped with nanometer resolution. Using the electron beam in a scanning transmission electron microscope to create solvated electrons and reactive radicals in an encapsulated solution-filled cavity in the nanorods, Ag ions were reduced nearby the electron beam, reshaping the core of the nanoparticles without affecting the external shape. The changes in plasmon-induced near-field properties were then mapped with electron energy-loss spectroscopy without disturbing the internal structure, and the results are supported by finite-difference time-domain calculations. This reversible shape and near-field control in a hollow nanoparticle actuated by an external stimulus introduces possibilities for applications in reprogrammable sensors, responsive materials, and optical memory units. Moreover, the liquid-filled nanorod cavity offers new opportunities for in situ microscopy of chemical reactions.

A nanosensor based on β-cyclodextrin (ßCD) macrocycles linked to gold nanoparticles for rhodamine B (RhB) sensing was developed applying the metal-enhanced fluorescence effect (MEF). Hence, we have developed many ways to control the distance of supramolecular systems to nanoparticle surface with different bioconjugation strategies in order to optimize signal detection. Different PEG spacer arm lengths were used to cover the nanoparticle surface with molecular spacers. This type of molecular shell is biocompatible, enabling to switch on/off the MEF effect using a dithiane linker by a simple reduction reaction. In the presence of the nanosensor obtained, an increase was observed in RhB fluorescence emission depending on molecular length, that is a characteristic effect ofMEF. Themajor increase measuredwas 60% compared with RhB emission in buffer at 1 nM level, for a spacer length of 3.58 nm and an 80% increase as compared with that in the presence of ßCD. These differences are ascribed to the fact that, in the presence of macrocycle, we can observe a well-known quenching effect that is overcome by the presence of the metallic core. Even at shorter spacer distances, with PEG lengths of 1.2 and 2.17nm, increases of 25 and 47% respectively allowthe analyte detection by the RhB complexation with ßCD. The optimal MEF enhancement was measured with the maximal emission signal stabilized after 50 min due to plasmonic effects based on inter nanoparticle interactions. Moreover, the emission increase, in the presence of the metallic core, was accompanied with a diminution in the fluorescence lifetime's decay value averages, characteristic of MEF. This fact shows that the excited state is protected from the non-radiative emission decays enhancing the analytical signal. Fil: Bracamonte, Angel Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina Fil: Brouard, Danny. Université Laval; Canadá Fil: Lessard Viger, Mathieu. Université Laval; Canadá Fil: Boudreau, Denis. Université Laval; Canadá Fil: Veglia, Alicia Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina

A method for creating pH maps in microchannels containing liquid/liquid and liquid/gas phases comprised of water and CO2 is demonstrated. It is based on a glass slide coated with nanoparticles exhibiting metal-enhanced fluorescence. The time resolution is better than 500 ms, limited by the fluidic control. This work opens the way for new in situ measurements of physical dissolution and chemical reactions in dynamic CO2 gas-liquid systems.

Hollow AgAu nanostructures have a myriad of potential applications related to their strong and tunable localized surface plasmon resonances. Here, we describe how the hydrolysis of the Au precursor, AuCl4–, produces AuCl4–x(OH)x–, where x is both time and pH-dependent, and how this can be used to control the morphology of hollow nanoshells in the co-reduction-assisted galvanic replacement of Ag by Au. Controlling the degree of hydrolysis is the key to obtain smooth shells: too small values of x (low hydrolysis) yield inhomogeneously replaced rough shells whereas too large values of x lead to the dominance of Au nucleation over galvanic replacement. Kinetic studies reveal two time constants for the galvanic replacement varying with temperature and composition; a short (100 min) half-life component associated with the continuous reduction and replacement of Ag. By optimizing the reaction’s pH and Au speciation, we obtained smooth alloy shells with fine control of composition, size, and shape over a broad range, thereby tuning the optical properties. This framework for understanding and controlling reaction kinetics and nanoshell morphology is applicable to other metallic systems and precursors, providing new ways to rationally design nanostructure syntheses.

Hollow noble metal nanoparticles are of growing interest due to their localized surface plasmon resonance (LSPR) tunability. A popular synthetic approach is galvanic replacement which can be coupled with a co-reducer. Here, we describe the control over morphology, and therefore over plasmonic properties including energy, bandwidth, extinction and scattering intensity, offered by co-reduction galvanic replacement. This study indicates that whereas the variation of atomic stoichiometry using the co-reduction method described in this work offers a rather modest tuning range of LSPR energy when compared to traditional galvanic replacement, it nevertheless has a profound effect on shell thickness, which imparts a degree of control over scattering intensity and sensitivity to changes in the dielectric constant of the surrounding environment. Therefore, in this context particle size and gold content become two design parameters that can be used to independently tune LSPR energy and intensity.

Background A point‐of‐care rapid test (POCRT) may help early and targeted use of antiviral drugs for the management of influenza A infection. Objective (i) To determine whether antiviral treatment based on a POCRT for influenza A is cost‐effective and, (ii) to determine the thresholds of key test parameters (sensitivity, specificity and cost) at which a POCRT based‐strategy appears to be cost effective. Methods An hybrid « susceptible, infected, recovered (SIR) » compartmental transmission and Markov decision analytic model was used to simulate the cost‐effectiveness of antiviral treatment based on a POCRT for influenza A in the social perspective. Data input parameters used were retrieved from peer‐review published studies and government databases. The outcome considered was the incremental cost per life‐year saved for one seasonal influenza season. Results In the base‐case analysis, the antiviral treatment based on POCRT saves 2 lives/100 000 person‐years and costs $7600 less than the empirical antiviral treatment based on clinical judgment alone, which demonstrates that the POCRT‐based strategy is dominant. In one and two way‐sensitivity analyses, results were sensitive to the POCRT accuracy and cost, to the vaccination coverage as well as to the prevalence of influenza A. In probabilistic sensitivity analyses, the POCRT strategy is cost‐effective in 66% of cases, for a commonly accepted threshold of $50 000 per life‐year saved. Conclusion The influenza antiviral treatment based on POCRT could be cost‐effective in specific conditions of performance, price and disease prevalence.

En héritant de l’ensemble de la collection de ressources en généalogie de la salle Gagnon de la défunte Bibliothèque centrale de Montréal en 2005, le Centre d’archives de Montréal reçoit notamment une grande quantité de revues de ce domaine. Cette acquisition enrichit avantageusement la collection de revues du Centre, jusque-là plutôt modeste. Ce sont plus de 280 titres différents qui forment aujourd’hui cette collection qui compte bien sûr des publications québécoises, mais aussi canadiennes, américaines et européennes. Même s’il n’est pas rare que l’on voie des usagers se consacrer au dépouillement des numéros de l’une ou l’autre de ces revues, il serait faux de dire que le potentiel de ces périodiques pour la recherche en généalogie est bien connu. Notre objectif est donc de valoriser cette collection.

Low-polydispersity europium-doped (H3O)Y3F10·xH2O single-crystal nanoparticles can be prepared via a simple reverse microemulsion method. The doping level of the particles can be varied by changing the relative concentration of europium to yttrium in the initial precursor mixture. Doping levels of up to 14 ± 2 at% can be attained without loss of the host crystal structure. Final europium concentrations, however, fall below those of the precursor solutions, suggesting that europium ions are less readily incorporated into the (H3O)Y3F10·xH2O crystal lattice than are yttrium ions. Emission spectra of the doped nanoparticles show sharp well-defined lines, which can be assigned to known europium transitions. The emission intensity increases linearly with increasing europium content. Europium ions within the nanocrystals exhibit excited-state lifetimes of 3–5 ms. These values are an order of magnitude greater than those of free ions in solution, indicating that ion incorporation in the yttrium fluoride matrix efficiently reduces non-radiative energy losses. Finally, data from time-resolved phosphorescence measurements suggests that europium ions within the particles are located in spectroscopically different environments which can be tentatively assigned to surface and core sites.

Background and Objectives The last two decades have seen major developments in genotyping assays to facilitate the procurement of red blood cell units to alloimmunized patients. To make genotyping faster, simpler and less costly, a nanotechnology approach based on metal/silica fluorescent nanoparticles and a polymer-based hybridization optical transducer was designed. The objectives of this study were (1) to verify whether this nanobiosensor has the ability to discriminate single nucleotide polymorphisms in non-amplified genomic DNA and (2) to establish whether the signal generated by the nanobiosensor is sufficiently intense to be detected by standard flow cytometry. Materials and Methods Silver-core silica-shell fluorescent nanoparticles (Ag@SiO2) were prepared, and amine-modified DNA probes were grafted to their surface. A cationic conjugated polymer was electrostatically bound to the surface probes to become optically active upon hybridization with a target. Two nanobiosensor formulations specific to DO*01 and DO*02 alleles were prepared. DNA was extracted from whole blood and mixed with the nanobiosensor for hybridization. The nanobiosensor fluorescence was measured by flow cytometry. Results Nine volunteers were typed for Dombrock blood group antigens DO*01 and DO*02. A statistically significant increase in the optical transduction signal was observed for sequence-specific samples. All nine genotypes were correctly identified when compared to standardized PCR assays. Conclusion The nanobiosensor provides rapid and simple genotyping of blood group antigens from unamplified genomic DNA and can be measured using standard flow cytometers. This PCR-free approach could be applied to any known genetic polymorphism.

The field known as plasmonics has seen a tremendous growth in interest from the research community. One of the more popular topics is the surface plasmon waveguide. As an alternative to solid linear nanostructures, a chain of plasmonic nanoparticles can also be used to propagate a traveling wave of surface charges. Experimentally, plasmonic nanoparticles lend themselves well to the fabrication of plasmonic waveguides via the self-assembly of nanoparticles into linear structures with very small inter-particle separation. In the present work, we used wrinkled PDMS stamps to fabricate large (i.e., several microns in length) one-dimensional nanoparticle assemblies. Combining this technique with the use of tunable, metal-dielectric, core-shell nanoparticles [1] allows the fabrication of linear assemblies with adjustable inter-particle separation. The observation of isolated nanoparticle assemblies by single particle microscopy/spectroscopy (epifluorescence, dark-field scattering, fluorescence lifetime microscopy) and scanning electron microscopy allows us to gather optical and structural information in order to derive interesting structure-properties correlations – in particular the interaction between propagating dark plasmons with the emission behavior from nearly fluorophores.

Supramolecular chemistry is a well-known field that, applied to analytical chemistry gives, as a result, supramolecular analytical chemistry. Based in its interactions, this field is part of a new area of nanomedicine, called supramolecular medicine. In order to improve the detection of biological molecules to be applied in cell tracking, health problems and biological events, supramolecular chemistry has lately been combined with supra-nanostructures design. In other words, supramolecular systems can be used as tools in the nano-design of nano-systems for the bio-recognition of biological events, host of ions and organic molecules with different structures and intrinsic chemical properties, as enhancer of the solubility, modification of surface properties, bioconjugation for the nanoparticles design, etc. The versatility of these types of systems is very wide; specifically their use in the nanosensor design using nanoparticles was not highly applied. However, in the last years, the bioconjugation of supramolecular systems, such as macrocycles and antibodies, and proteins with metallic and polymeric nanoparticles has increased, as well as the development of supramolecular nanoparticles based on host guest interactions of macrocycles. Therefore, this review focuses on the application of supramolecular systems as signal transducers in the nanosensors design for bio-recognition events, detection of biological targets, and drug delivery system. These nanosystems, as transducer hosts and building blocks, are linked to metallic and polymeric nanoparticles; and organize molecular systems for different applications. Fil: Gontero, Daniela. Laval University. Centre Hospitalier de L'universite Laval; Canadá Fil: Lessard Viger, Mathieu. Laval University; Canadá Fil: Brouard, Danny. Groupe Évaluation Optimisation; Canadá Fil: Bracamonte, Angel Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina Fil: Boudreau, Denis. Universite Laval; Francia Fil: Veglia, Alicia Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina

A novel method allowing for the inscription of optical waveguides up to the surface of almost any transparent material is introduced. The resulting waveguides are employed for the photoexcitation of fluorescence-emitting nanostructures.

International audience; The present work involves the design of a multifunctional system based on gold nanoshells (AuNSs) decorated with lanthanide-based upconversion nanoparticles (UCNPs) intended as an optical heater and a temperature probe at the nanoscale. The synthesis of NaGdF4 UCNPs doped with ions Yb3+:Er3+ was performed via thermal decomposition of lanthanide fluoride precursors at high temperatures (>300 °C) in the presence of a coordinating ligand (oleic acid). UCNPs were synthesized at three different temperatures (310, 315 and 320 °C) and characterized in terms of morphological, structural and emission properties. In view of the intended biological applications, the surface of hydrophobic oleate-capped UCNPs was modified using a silica coating to achieve sufficient water dispersibility, through a modified Stöber process using a reverse micro-emulsion method. Monodisperse NaGdF4:Yb3+:Er3+ upconversion nanocrystals (∼25 nm dia.) were obtained in cubic (at 310, 315 °C) and hexagonal (at 320 °C) phases. The UCNPs in the hexagonal phase were shown to be more suitable as temperature sensors, due to their lower red-to-green emission ratios and higher thermal sensitivities. The emission spectrum of NaGdF4:Yb3+:Er3+ (oleate- or silica-coated) UCNPs was recorded at different temperatures in the vicinity of the physiological range (20–70 °C) and presented suitable properties for application as temperature sensors, such as excellent linearity (r2 > 0.99) and sensitivity (>3 × 10−3 K−1). The heating capacity of AuNSs@UCNPs was verified by monitoring the Er3+ emission, showing their potential for application as a hyperthermia agent controlled using a nanothermometer function.

In this work, we designed a ratiometric core-shell nanoarchitecture composed of an indium UV plasmonic core, an internal reference (rhodamine B), a pH-sensitive probe (fluorescein), and a halide ion sensor (6-methoxyquinolinium). Immobilizing the fluorophores in distinct silica layers at precise distances from the core modulates the plasmon coupling and tunes the linear concentration range of halide ion detection.

A microfluidic platform with a fluorescent nanoparticle-based sensor is demonstrated for real-time, ratiometric pH imaging of biofilms. Sensing is accomplished by a thin patterned layer of covalently bonded Ag@SiO2+FiTC nanoparticles on an embedded planar glass substrate. The system is designed to be sensitive, responsive and give sufficient spatial resolution to enable new micro-scale studies of the dynamic response of oral biofilms to well-controlled chemical and hydrodynamic stimulation. Performance under challenging operational conditions is demonstrated, which include long-duration exposure to sheer stresses, photoexcitation and pH sensor biofouling. After comprehensive validation, the device was used to monitor pH changes at the attachment surface of a biofilm of the oral bacteria, Streptococcus salivarius. By controlling flow and chemical concentration conditions in the microchannel, biochemical and mass transport contributions to the Stephan curve could be probed individually. This opens the way for the analysis of separate contributions to dental caries due to localized acidification directly at the biofilm tooth interface.