Gold nanoparticles capped with polysaccharides extracted from pineapple gum: Evaluation of their hemocompatibility and electrochemical sensing properties.

In the present work, gold nanoparticles were synthesized through a green route by using, for the first time, polysaccharides extracted from pineapple gum (PG) as the reducing and capping agent. The obtained nanoparticles (AuNPs-PG) were characterized by UV-VIS, FTIR, TEM, FESEM, EDX, XRD, and zeta potential measurements, which confirmed that PG was effective to produce AuNPs with an average diameter of 10.3 ± 1.6 nm. The AuNPs-PG were employed as the modifier of glassy carbon paste electrodes (CPE/AuNPs-PG), which were applied as sensitive electrochemical sensors to the determination of the antihistamine drug promethazine hydrochloride (PMZ). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements showed that the AuNPs-PG could enhance the electronic transfer properties of the glassy carbon paste, which was due to their large surface area and high electrical conductivity. After optimization of the instrumental parameters of square wave voltammetry (SWV) through a Box-Behnken factorial design, a linear relationship between the anodic peak current and PMZ concentration was obtained in the range from 2.0 to 15.7 µmol L-1 in McIlvaine buffer solution pH 5.0. The detection and quantification limits were found to be equal to 1.33 and 4.44 µmol L-1, respectively. The developed sensors could successfully quantify PMZ in different commercial pharmaceutical formulations, with satisfactory levels of accuracy and precision. In addition to improving the analytical features of the electrodes, hemocompatibility assays carried out on erythrocytes and leukocytes showed that the AuNPs-PG do not exhibit toxic effects on the referred cells. This interesting behavior enables their use in biocompatible electrochemical sensing platforms as well as for future biomedical investigations.

Porphyran-capped silver nanoparticles as a promising antibacterial agent and electrode modifier for 5-fluorouracil electroanalysis.

In the present work, the green synthesis of silver nanoparticles (AgNPs) using the sulfated polysaccharide porphyran (PFR) as capping agent and d-glucose as reducing agent is described. PFR was extracted from red seaweed and characterized by employing 13C NMR and determination of total sugar, protein, and sulfate contents. The obtained AgNPs-PFR were characterized by using UV-VIS spectroscopy, zeta potential determination, FESEM, and TEM, which demonstrated that PFR was effective at capping the AgNPs, yielding stable suspensions. The AgNPs-PFR presented good antimicrobial properties against Gram-positive and Gram-negative bacterial strains (Staphylococcus aureus and Escherichia coli, respectively). The AgNPs-PFR were also employed as the modifier of carbon paste electrodes, which were efficiently applied as electrochemical sensors for the determination of 5-fluorouracil (5-FU), an important anticancer drug, through square wave voltammetry (SWV). The AgNPs-PFR improved the electrochemical properties of the electrodes, and enhanced their electroanalytical performance. The developed sensing device presented detection and quantification limits equal to 10.7 and 35.8 µmol L-1, respectively, towards 5-FU determination. The proposed electrochemical sensor successfully quantified 5-FU in a real pharmaceutical formulation, confirming its potential as a new promising analytical detection tool for 5-FU quality control purposes.

A sensitive label-free impedimetric DNA biosensor based on silsesquioxane-functionalized gold nanoparticles for Zika Virus detection.

Zika virus (ZIKV) has recently become a global health challenge due to its rapid geographical expansion, since it is associated with serious neurological anomalies such as Guillain-Barré syndrome and microcephaly. Currently, the techniques for ZIKV diagnosis require labor-intensive, expensive and lengthy tests using sophisticated equipment. Moreover, false-positive or false-negative results can occur. In the present work, a DNA biosensor to detect ZIKV in real human serum samples was developed using an oxidized glassy carbon electrode (ox-GCE) modified with silsesquioxane-functionalized gold nanoparticles (AuNPs-SiPy). This nanohybrid was characterized by UV-Vis, FTIR and Raman spectroscopies, DLS, and XRD. The conditions for the immobilization of a ZIKV ssDNA probe on the electrode surface (ox-GCE-[AuNPs-SiPy]) were optimized by univariate and multivariate analysis. The optimized biosensor was characterized by CV, EIS and AFM experiments. The ZIKV target recognition was based on the variation of the charge transfer resistance (ΔRct) of the redox marker ([Fe(CN)6]3-/4-) used and the roughness (Rq) of the electrode surface. The proposed biosensor presented a LOD of 0.82 pmol L-1, with a linear range of 1.0 x10-12 - 1.0 x10-6 mol L-1. Moreover, the reported device showed a suitable stability and satisfactory sensitivity and selectivity to quantify ZIKV in human serum samples, which suggests its promising clinical applications for the early diagnosis of ZIKV-associated pathologies.