Optimization of Surface-Enhanced Raman Spectroscopy Detection Conditions for Interaction between Gonyautoxin and Its Aptamer

This study aimed to optimize the detection conditions for surface-enhanced Raman spectroscopy (SERS) of single-stranded DNA (ssDNA) in four different buffers and explore the interaction between gonyautoxin (GTX1/4) and its aptamer, GO18. The influence of the silver colloid solution and MgSO4 concentration (0.01 M) added under four different buffered conditions on DNA SERS detection was studied to determine the optimum detection conditions. We explored the interaction between GTX1/4 and GO18 under the same conditions as those in the systematic evolution of ligands by exponential enrichment technique, using Tris-HCl as the buffer. The characteristic peaks of GO18 and its G-quadruplex were detected in four different buffer solutions. The change in peak intensity at 1656 cm−1 confirmed that the binding site between GTX1/4 and GO18 was in the G-quadruplex plane. The relative intensity of the peak at 1656 cm−1 was selected for the GTX1/4–GO18 complex (I1656/I1099) to plot the ratio of GTX1/4 in the Tris-HCl buffer condition (including 30 μL of silver colloid solution and 2 μL of MgSO4), and a linear relationship was obtained as follows: Y = 0.1867X + 1.2205 (R2 = 0.9239). This study provides a basis for subsequent application of SERS in the detection of ssDNA, as well as the binding of small toxins and aptamers.

Improved Sensitivity with Chloride Ions on Nanoparticle Enhanced Laser-Induced Breakdown Spectroscopy

In this study, the addition of chloride ions to silver colloid was proposed as an effective approach to enhance laser-induced breakdown spectroscopy (LIBS) signal. We studied the emission intensity of...

New Generation of Antibacterial Products Based on Colloidal Silver

The main objective of the present paper is the green synthesis of colloidal silver by ultrasonication starting from silver nitrate and using soluble starch as the reducing agent. Soluble starch has been used during synthesis because it is a cheap and environmentally friendly reactive. Silver colloid has been characterized by physicochemical methods: UV–VIS spectroscopy, Scanning Electron Microscopy and Energy Dispersive X-Ray spectroscopy. This colloidal material was prepared in order to prove and establish its toxicity on heterotrophic bacteria. Toxicity tests were carried out using test cultures with and without silver colloid with different concentrations. This way was possible to establish the minimum silver concentration that presents a toxic effect against used bacteria. Quantitative evaluation of bacterial growth was performed by using the Most Probable Number method. By counting the bacterial colony number, the antibacterial effect was determined for colloidal silver deposited onto the cotton gauze by adsorption. During the present study, we optimized the adsorption specific parameters: solid:liquid ratio, temperature, contact time, colloidal silver concentration. By thermodynamic, equilibrium and kinetic studies, the adsorptive process mechanism was established.

Procaine Detection Using Hybrids of Cobalt-Metalloporphyrin with Gold and Silver Nanoparticles

Two organic-inorganic nanomaterials derived from Co(II)-tetra(3-hydroxyphenyl)porphyrin (Co-3OHPP) and noble metal nanoparticles, namely: Co-porphyrin-nanoAu (Co-3OHPP/nAu) and Co-porphyrin-nanoAg (Co-3OHPP/nAg) were obtained and tested for their capacity to detect procaine. Both hybrids present changes in UV-vis spectroscopy after interaction with procaine, in the same range of procaine concentration. The silver colloid is more easily obtainable and more economically affordable and its hybrid has a wider range of procaine detection from 5.39 x 10-5 mol l-1 to 28.04 x 10-5 mol l-1 concentration, thus being useful for the monitoring of the anesthesic remanence in patients’ plasma. Besides, the plasmonic band of the hybrid is more clearly defined. AFM studies were performed to compare the morphology of the two hybrid materials, Co-3OHPP/nAu and Co-3OHPP/nAg after being exposed to procaine. Both materials display triangular geometries that in case of Co-3OHPP/nAg are not very well defined taking also the form of kvatarons and these two coexisting forms generate pyramidal architectures.