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Hydrogen peroxide (H2O2) plays critical roles innumerous biological process, including cell proliferation, differentiation, and apoptosis; oxidative stress and cancer cells related metabolic activities. But its accurate detection remains challenging. This [...]

Silicon-based nanoparticles (SiNPs) have been investigated for their applications in a wide variety of cell labeling with low toxicity and biocompatibility. However, SiNPs are frequently reported to have a strong [...]

Metal-containing nanoparticles are now common in applications ranging from catalysts to biomarkers. However, little research has focused on per-particle metal content in multicomponent nanoparticles. In this work, we used single-particle inductively coupled plasma mass spectrometry (ICP-MS) to determine the per-particle metal content of silica nanoparticles doped with tris(2,2′-bipyridyl)ruthenium(II). Monodispersed silica nanoparticles with varied Ru doping levels were prepared using a water-in-oil microemulsion method. These nanoparticles were characterized using common bulk-sample methods such as absorbance spectroscopy and conventional ICP-MS, and also with single-particle ICP-MS. The results showed that averaged concentrations of metal dopant measured per-particle by single-particle ICP-MS were consistent with the bulk-sample methods over a wide range of dopant levels. However, the per-particle amount of metal varied greatly and did not adhere to the usual Gaussian distribution encountered with one-component nanoparticles, such as gold or silver. Instead, the amount of metal dopant per silica particle showed an unexpected geometric distribution regardless of the prepared doping levels. The results indicate that an unusual metal dispersal mechanism is taking place during the microemulsion synthesis, and they challenge a common assumption that doped silica nanoparticles have the same metal content as the average measured by bulk-sample methods. [ABSTRACT FROM AUTHOR]

Silica nanoparticles (SiNPs) have been used as vehicles for drug delivery, molecular detection, and cellular manipulations in nanoneuromedicine. SiNPs may cause adverse effects in the brain including neurotoxicity, neuroinflammation, neurodegeneration, and enhancing levels of amyloid beta (A[beta]) protein--all pathological hallmarks of Alzheimer's disease. Therefore, the extent to which SiNPs influence A[beta] generation and the underlying mechanisms by which this occurs deserve investigation. Our studies were focused on the effects of SiNPs on endolysosomes which uptake, traffic, and mediate the actions of SiNPs. These organelles are also where amyloidogenesis largely originates. We found that SiNPs, in primary cultured hippocampal neurons, accumulated in endolysosomes and caused a rapid and persistent deacidification of endolysosomes. SiNPs significantly reduced endolysosome calcium stores as indicated by a significant reduction in the ability of the lysosomotropic agent glycyl-L-phenylalanine 2-naphthylamide (GPN) to release calcium from endolysosomes. SiNPs increased Ap1-40 secretion, whereas 2 agents that acidified endolysosomes, ML-SA1 and CGS21680, blocked SiNP-induced deacidification and increased generation of Ap1-40. Our findings suggest that SiNP-induced deacidification of and calcium release from endolysosomes might be mechanistically linked to increased amyloidogenesis. The use of SiNPs might not be the best nanomaterial for therapeutic strategies against Alzheimer's disease and other neurological disorders linked to endolysosome dysfunction. Key words: Alzheimer's disease, amyloid beta protein, endolysosomes, nanoparticles, ML-SA1, silica nanoparticles, SiNP. Les nanoparticules de silice (ou SiNP pour << silica nanoparticles >>) ont ete utilisees en nanoneuromedecine comme vehicule en vue du largage de medicaments, de la detection moleculaire et de la manipulation cellulaire. Par contre, les SiNP pourraient entrainer des effets indesirables dans le cerveau, notamment de la neurotoxicite, de la neuroinflammation, de la neurodegenerescence, ainsi que l'augmentation des taux de la proteine beta amyloide (A[beta]) : toutes des caracteristiques de la maladie d'Alzheimer. Par consequent, l'etendue de l'influence des SiNP sur la production d'Ap et les modes d'action sous-jacents meritent d'etre etudies. Nos etudes etaient centrees sur les effets des SiNP sur les endolysosomes, lesquels recueillent les SiNP, les font circuler et participent a la mediation de leurs effets. Ces organites sont aussi largement a la base de l'amyloidogenese. Dans des cultures de neurones de l'hippocampe primitifs, nous avons observe que les SiNP s'accumulent dans les endolysosomes et y entrainent une desacidification rapide et persistante. Les SiNP entrainaient une diminution importante des stocks de calcium dans les endolysosomes dont temoignait une diminution notable de la capacite du GPN (glycyl-L-phenylalanine 2-naphthylamide), un agent lysosomotrope, d'en liberer du calcium. Les SiNP entrainaient une augmentation de la secretion de l'Ap1-40 alors que le ML-SA1 et le CGS21680, deux agents qui entrainaient une acidification des endolysosomes, permettaient d'inhiber la desacidification et l'augmentation de la production d'Ap1-40 engendrees par les SiNP. Nos resultats laissent entendre que les modes d'action de la desacidification et de la liberation du calcium des endolysosomes engendrees par les SiNP pourraient etre lies a une augmentation de l'amyloidogenese. En somme, les SiNP pourraient ne pas etre les meilleurs nanomateriaux a utiliser dans des strategies visant le traitement de la maladie d'Alzheimer ou d'autres maladies neurologiques liees au dysfonctionnement des endolysosomes. [Traduit par la Redaction] Mots-cles : maladie d'Alzheimer, proteine amyloide beta, endolysosomes, nanoparticules, ML-SA1, nanoparticules de silice, SiNP., Introduction The discovery of silica nanoparticles (SiNPs) has led, in part, to the growth of nanotechnology in various fields including electronics, aerospace engineering, health care, and biomedicine (Singh et al. [...]

An ultrasensitive assay is described for the detection and determination of Hg2+(aq) in water samples based on single-particle inductively-coupled plasma/mass spectrometry (spICP-MS). In the presence of Hg2+(aq), AuNPs modified with a segment of single-stranded DNA aggregate due to the formation of the well-known thymine (T)-Hg2+-T complex. Single particle (sp) ICP-MS is used quantify the degree of aggregation by the overall decrease in number of detected AuNPs or NP aggregates. Compared with most other Hg2+ assays that use the same principle of aggregation-dispersion with DNA modified AuNPs, this method has a much lower detection limit of (0.031 ng L−1, 155 fM) and a wider (10,000-fold) linear range (up to 1 μg L−1). The method also showed good practical potential because of its minimal interference from the water sample matrix. [ABSTRACT FROM AUTHOR]