RESUMO
Decoration of nanoparticles with specific molecules such as antibodies, peptides, and proteins that preserve their biological properties is essential for the recognition and internalization of their specific target cells. Inefficient preparation of such decorated nanoparticles leads to nonspecific interactions diverting them from their desired target. We report a simple two-step procedure for the preparation of biohybrid nanoparticles containing a core of hydrophobic quantum dots coated with a multilayer of human serum albumin. These nanoparticles were prepared by ultra-sonication, crosslinked using glutaraldehyde, and decorated with proteins such as human serum albumin or human transferrin in their native conformations. These nanoparticles were homogeneous in size (20-30 nm), retained the fluorescent properties of quantum dots, and did not show a "corona effect" in the presence of serum. The uptake of transferrin-decorated quantum dot nanoparticles was observed in A549 lung cancer and SH-SY5Y neuroblastoma cells but not in non-cancerous 16HB14o- or retinoic acid dopaminergic neurons differentiated SH-SY5Y cells. Furthermore, digitoxin-loaded transferrin-decorated nanoparticles decreased the number of A549 cells without effect on 16HB14o-. Finally, we analyzed the in vivo uptake of these biohybrids by murine retinal cells, demonstrating their capacity to selectively target and deliver into specific cell types with excellent traceability.
RESUMO
Enzyme inks can be inkjet printed to fabricate enzymatic biosensors. However, inks containing enzymes present a low shelf life because enzymes in suspension rapidly lose their catalytic activity. Other major problems of printing these inks are the non-specific adsorption of enzymes onto the chamber walls and stability loss during printing as a result of thermal and/or mechanical stress. It is well known that the catalytic activity can be preserved for significantly longer periods of time and to harsher operational conditions when enzymes are immobilized onto adequate surfaces. Therefore, in this work, horseradish peroxidase was covalently immobilized onto silica nanoparticles. Then, the nanoparticles were mixed into an aqueous ink containing single walled carbon nanotubes. Electrodes printed with this specially formulated ink were characterized, and enzyme electrodes were printed. To test the performance of the enzyme electrodes, a complete amperometric hydrogen peroxide biosensor was fabricated by inkjet printing. The electrochemical response of the printed electrodes was evaluated by cyclic voltammetry in solutions containing redox species, such as hexacyanoferrate (III/II) ions or hydroquinone. The response of the enzyme electrodes was studied for the amperometric determination of hydrogen peroxide. Three months after the ink preparation, the printed enzyme electrodes were found to still exhibit similar sensitivity, demonstrating that catalytic activity is preserved in the proposed ink. Thus, enzyme electrodes can be successfully printed employing highly stable formulation using nanoparticles as carriers.
RESUMO
The combination of different nanomaterials through step-by-step synthesis procedures has turned into a promising alternative to fabricate high-quality nanosystems in order to satisfy the increasingly demanding requirements of the biomedical field. In this work, we report a detailed study on the synthesis and characterization of a complex nanosystem composed of nanoparticles with a single magnetic nanoparticle core and a shell of dense and mesoporous silica arranged in layers. The procedure designed to fabricate these systems lead us to the formation of a dispersion of non-agglomerated spherical nanoparticles of nearly 100 nm. The structural characterization performed over the final samples confirmed both the prevalence of single-core systems and the presence of the mesoporous silica shell in the outer layer. The performance of the nanosystem in a specific technological application was tested by sequentially loading two different fluorescents molecules by covalent and non-covalent bonding strategies. Due to the distinct loading strategies, the resulting nanosystem presented a magnetically-assisted probe & release functionality as analyzed in a magnetophoretic experiment.
RESUMO
This study aimed to investigate the acute effects of chlorpyrifos on biomarkers related to neurotoxicity and immunotoxicity in two allopatric freshwater gastropod species belonging to the family Planorbidae. For this purpose, Planorbarius corneus and Biomphalaria glabrata were exposed to chlorpyrifos (active ingredient or commercial formulation) for 48 h at environmentally realistic concentrations (1 and 7.5 µg L-1). Basal acetylcholinesterase activity in soft tissues and hemolymph was almost one order of magnitude higher in P. corneus than in B. glabrata. However, upon chlorpyrifos exposure, statistically significant inhibition of enzymatic activity was registered in both species. Acetylcholinesterase was more sensitive to inhibition in soft tissues than in hemolymph. The highest inhibition was observed in the B. glabrata soft tissues exposed to the commercial formulation (88 % at 1 µg L-1 and 93 % at 7.5 µg L-1). Hemocyte number and lysosomal membrane stability did not show significant changes with respect to controls in any of the exposed groups. Superoxide anion generation was diminished (21-46 %) in P. corneus hemocytes exposed to the active ingredient and in B. glabrata hemocytes exposed to the active ingredient or the formulation. In contrast, hemocyte phagocytic activity increased in all exposed groups. Phagocytosis was most stimulated (89 %) in hemocytes sampled from B. glabrata treated with 7.5 µg L-1 chlorpyrifos. Altogether the results suggest that the freshwater gastropods P. corneus and B. glabrata are suitable model animals for environmental monitoring studies in the Northern Hemisphere and Latin America, respectively. Furthermore, these results add information on the relevance of testing pesticide formulations and on the usefulness of acetylcholinesterase inhibition and immunological parameters as biomarkers of the acute effects of chlorpyrifos in these species.