Antioxidant capacity of Myrciaria cauliflora seed extracts by spectrophotometric, biochemical, and electrochemical methods and its protective effect against oxidative damage in erythrocytes.

This study aimed to investigate the antioxidant activity of extracts obtained from jabuticaba (Myrciaria cauliflora) seeds. Ethanolic (ETJS), methanolic (MEJS), aqueous (AQJS), and propanone (PRJS) extracts was assessed by measuring spectrophotometrically their ability to scavenge DPPH· , ABTS·+ , HOCl, and O2 ·- radicals. Electrochemical methods were employed, and the obtained data presented a good correlation with the radical scavenging results. The extracts were also able to attenuate lipid peroxidation induced by Fe2+ ions in phospholipids due to their chelation ability. The extracts protected human erythrocytes against oxidative cellular damage caused by AAPH, which was confirmed by using FESEM analysis. PRJS extract demonstrated the highest effect in all assays used in this work. Our findings prove that jabuticaba seeds are an important source of antioxidants which act by different mechanisms. This study opens new frontiers regarding the use of this fruit byproduct as a food additive. PRACTICAL APPLICATIONS: Jabuticaba seeds are usually discarded as waste by food industries, but they are rich in bioactive products and present interesting biological properties. Herein, we demonstrated that their extracts show remarkable antioxidant power against different reactive oxygen species, which are involved in several human pathologies. In this way, this by-product can be further used in the development of products to protect the human body against diseases related to oxidative stress.

Nanoconjugates based on a novel organic-inorganic hybrid silsesquioxane and gold nanoparticles as hemocompatible nanomaterials for promising biosensing applications.

A new hybrid organic-inorganic silsesquioxane material, 3-n-propyl(2-amino-4-methyl)pyridium chloride (SiAMPy+Cl-), was synthesized and successfully applied for the synthesis of stable nanoconjugates with gold nanoparticles (AuNPs-SiAMPy+). SiAMPy+Cl- was obtained through a simple sol-gel procedure by using chloropropyltrimetoxysilane and tetraethylorthosilicate as precursors and 2-amino-4-methylpyridine as the functionalizing agent. The resulting material was characterized by employing FTIR, XRD, and 1H-, 13C-, and 29Si-NMR spectroscopy. The synthesis of AuNPs-SiAMPy+ nanoconjugates was optimized through a 23 full factorial design. UV-VIS, FTIR, TEM, DLS, and ζ-potential measurements were used to characterize the nanoconjugates, which presented a spherical morphology with an average diameter of 5.8 nm. To investigate the existence of toxic effects of AuNPs-SiAMPy+ on blood cells, which is essential for their future biomedical applications, toxicity assays on human erythrocytes and leukocytes were performed. Interestingly, no cytotoxic effects were observed for both types of cells. The nanoconjugates were further applied in the construction of electrochemical immunosensing devices, aiming the detection of anti-Trypanosoma cruzi antibodies in serum as biomarkers of Chagas disease. The AuNPs-SiAMPy+ significantly enhanced the sensitivity of the biodevice, which was able to discriminate between anti-T. cruzi positive and negative serum samples. Thus, the AuNPs-SiAMPy+-based biosensor showed great potential to be used as a new tool to perform fast and accurate diagnosis of Chagas disease. The promising findings described herein strongly confirm the remarkable potential of SiAMPy+Cl- to obtain nanomaterials, which can present notable biomedical properties and applications.

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.

Silsesquioxane as a new building block material for modified electrodes fabrication and application as neurotransmitters sensors.

Nanostructured films comprising a 3-n-propylpyridinium silsesquioxane polymer (designated as SiPy+Cl-) and copper (II) tetrasulfophthalocyanine (CuTsPc) were produced using the Layer-by-Layer technique (LbL). To our knowledge this is the first report on the use of silsesquioxane derivative polymers as building blocks for nanostructured thin films fabrication. Deposition of the multilayers were monitored by UV-Vis spectroscopy revealing the linear increment in the absorbance of the Q-band from CuTsPc at 617 nm with the number of SiPy+Cl-/CuTsPc or CuTsPc/SiPy+Cl-bilayers. FTIR analyses showed that specific interactions between SiPy+Cl- and CuTsPc occurred between SO3- groups of tetrasulfophthalocyanine and the pyridinium groups of the polycation. Morphological studies were carried out using the AFM technique, which showed that the roughness and thickness of the films increase with the number of bilayers. The films displayed electroactivity and were employed to detection of dopamine (DA) and ascorbic acid (AA) using cyclic voltammetry, at concentrations ranging from 1.96 x 10(-4) to 1.31 x 10(-3) molL(-1). The number and the sequence of bilayers deposition influenced the electrochemical response in presence of DA and AA. Using differential pulse technique, films comprising SiPy+/-/CuTsPc were able to distinguish between DA and ascorbic acid (AA), with a potential difference of approximately with 500 mV, in the concentration range of 9.0 x 10(-5) to 2.0 x 10(-4) molL(-1), in pH 3.0.