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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).

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.

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

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.

A novel methodology was developed for the synthesis of tuneable silver–silica core–shell nanoparticles (Ag@SiO2). The use of tannic acid and sodium citrate to reduce and stabilize silver atoms allowed the controlled synthesis of silver cores ranging from 26–118 nm in diameter, and silica shells of tuneable thicknesses from 6–51 nm were deposited using a combination of tetraethyl orthosilicate and sodium citrate. Both core size and spacer thickness can be tuned over a wide range of diameters and thicknesses by the simple variation of the reagent stoichiometric ratios, and mg range quantities of highly uniform core–shell nanoparticles can be prepared with excellent repeatability and reproducibility. To ascertain the usefulness of the core–shell nanoparticles for plasmonic enhancement studies, fluorescence measurements were performed on core–shell and coreless nanoparticles coated with a molecular fluorophore.

Large fluorescence enhancement of UV-active molecular models Carbostyril 124 and tryptophan by core-shell indium-based plasmonic architectures demonstrates the metal's potential in the design of bioprobes. Precise control over the metal-fluorophore distance is achieved through the controlled deposition of a uniform silica layer over the nanosized indium particles.