In vitro cytotoxicity of SiO2 or ZnO nanoparticles with different sizes and surface charges on U373MG human glioblastoma cells

The Size-dependent Cytotoxicity of Amorphous Silica Nanoparticles: A Systematic Review of in vitro Studies

With the increasing production and application of engineered amorphous silica nanoparticles (aSiNPs), people have more opportunities to be exposed to aSiNPs. However, the knowledge of its adverse health effects and related mechanisms is still limited, compared with the well-studied crystalline micron-sized silica. Since small differences in the physical–chemical properties of nanoparticles could cause significant differences in the toxic effect, it is important to distinguish how these variations influence the outcoming toxicity. Notably, particle size, as one of the essential characterizations of aSiNPs, is relevant to its biological activities. Thus, the aim of this systematic review was to summarize the relationship between the particle size of aSiNPs and its adverse biological effects. In order to avoid the influence of complicated in vivo experimental conditions on the toxic outcome, only in vitro toxicity studies which reported on the cytotoxic effect of different sizes aSiNPs were included. After the systematic literature retrieval, selection, and quality assessment process, 76 eligible scientific papers were finally included in this review. There were 76% of the studies that concluded a size-dependent cytotoxicity of aSiNPs, in which smaller-sized aSiNPs possessed greater toxicity. However, this trend could be modified by certain influence factors, such as the synthetic method of aSiNPs, particle aggregation state in cell culture medium, toxicity endpoint detection method, and some other experimental conditions. The effects of these influence factors on the size-dependent cytotoxicity of aSiNPs were also discussed in detail in the present review.

Antimicrobial Properties of the Polyaniline Composites against Pseudomonas aeruginosa and Klebsiella pneumoniae

CuO, TiO2, or SiO2 was decorated on polyaniline (PANI) by a sonochemical method, and their antimicrobial properties were investigated for two common Gram-negative pathogens: Pseudomonas aeruginosa (PA) and Klebsiella pneumoniae (KP). Without PANI, CuO, TiO2, or SiO2 with a concentration of 220 µg/mL exhibited no antimicrobial activities. In contrast, PANI-CuO and PANI-TiO2 (1 mg/mL, each) completely suppressed the PA growth after 6 h of exposure, compared to 12 h for the PANI-SiO2 at the same concentration. The damage caused by PANI-SiO2 to KP was less effective, compared to that of PANI-TiO2 with the eradication time of 12 h versus 6 h, respectively. This bacterium was not affected by PANI-CuO. All the composites bind tightly to the negative groups of bacteria cell walls to compromise their regular activities, leading to the damage of the cell wall envelope and eventual cell lysis.

ZnO Nanolower-Based NanoPCR as an Efficient Diagnostic Tool for Quick Diagnosis of Canine Vector-Borne Pathogens

Polymerase chain reaction (PCR) is a unique technique in molecular biology and biotechnology for amplifying target DNA strands, and is also considered as a gold standard for the diagnosis of many canine diseases as well as many other infectious diseases. However, PCR still faces many challenges and issues related to its sensitivity, specificity, efficiency, and turnaround time. To address these issues, we described the use of unique ZnO nanoflowers in PCR reaction and an efficient ZnO nanoflower-based PCR (nanoPCR) for the molecular diagnosis of canine vector-borne diseases (CVBDs). A total of 1 mM of an aqueous solution of ZnO nanoflowers incorporated in PCR showed a significant enhancement of the PCR assay with respect to its sensitivity and specificity for the diagnosis of two important CVBDs, Babesia canis vogeli and Hepatozoon canis. Interestingly, it drastically reduced the turnaround time of the PCR assay without compromising the yield of the amplified DNA, which can be of benefit for veterinary practitioners for the improved management of diseases. This can be attributed to the favorable adsorption of ZnO nanoflowers to the DNA and thermal conductivity of ZnO nanoflowers. The unique ZnO nanoflower-assisted nanoPCR greatly improved the yield, purity, and quality of the amplified products, but the mechanism behind these properties and the effects and changes due to the different concentrations of ZnO nanoflowers in the PCR system needs to be further studied.

Effect of surface organic coatings of cellulose nanocrystals on the viability of mammalian cell lines

Cellulose nanocrystals (CNCs) have emerged as promising candidates for a number of bio-applications. Surface modification of CNCs continues to gain significant research interest as it imparts new properties to the surface of the nanocrystals for the design of multifunctional CNCs-based materials. A small chemical surface modification can potentially lead to drastic behavioral changes of cell-material interactions thereby affecting the intended bio-application. In this work, unmodified CNCs were covalently decorated with four different organic moieties such as a diaminobutane fragment, a cyclic oligosaccharide (β-cyclodextrin), a thermoresponsive polymer (poly[N-isopropylacrylamide]), and a cationic aminomethacrylamide-based polymer using different synthetic covalent methods. The effect of surface coatings of CNCs and the respective dose-response of the above organic moieties on the cell viability were evaluated on mammalian cell cultures (J774A.1 and MFC-7), using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphe-nyltetrazolium bromide and lactate dehydrogenase assays. Overall, the results indicated that cells exposed to surface-coated CNCs for 24 h did not display major changes in cell viability, membrane permeability as well as cell morphology. However, with longer exposure, all these parameters were somewhat affected, which appears not to be correlated with either anionic or cationic surface coatings of CNCs used in this study.

The Effects of Silica Nanoparticles on Apoptosis and Autophagy of Glioblastoma Cell Lines

Silica nanoparticles (SiNPs) are one of the most commonly used nanomaterials in various medical applications. However, possible mechanisms of the toxicity caused by SiNPs remain unclear. The study presented here provides novel information on molecular and cellular effects of SiNPs in glioblastoma LBC3 and LN-18 cells. It has been demonstrated that SiNPs of 7 nm, 5–15 nm and 10–20 nm induce time- and dose-dependent cytotoxicity in LBC3 and LN-18 cell lines. In contrast to glioblastoma cells, we observed only weak reduction in viability of normal skin fibroblasts treated with SiNPs. Furthermore, in LBC3 cells treated with 5–15 nm SiNPs we noticed induction of apoptosis and necrosis, while in LN-18 cells only necrosis. The 5–15 nm SiNPs were also found to cause oxidative stress, a loss in mitochondrial membrane potential, and changes in the ultrastructure of the mitochondria in LBC3 cells. Quantitative real-time PCR results showed that in LBC3 cells the mRNA levels of pro-apoptotic genes Bim, Bax, Puma, and Noxa were significantly upregulated. An increase in activity of caspase-9 in these cells was also observed. Moreover, the activation of SiNP-induced autophagy was demonstrated in LBC3 cells as shown by an increase in LC3-II/LC3-I ratio, the upregulation of Atg5 gene and an increase in AVOs-positive cells. In conclusion, this research provides novel information concerning molecular mechanisms of apoptosis and autophagy in LBC3 cells.

Neurons Internalize Functionalized Micron-Sized Silicon Dioxide Microspheres

Microparticles have potential as neuron-specific delivery platforms and devices with many applications in neuroscience, pharmacology, and biomedicine. To date, most literature suggests that neurons are not phagocytic cells capable of internalizing microparticles larger than 0.5 μm. We report that neurons transport fluorescently labeled silica microspheres with diameters of 1-2 μm into neurons in vitro and in rat brain without having overt effects on cell viability. Using flow cytometry, fluorescence-activated cell sorting, and confocal and electron microscopy, we first found that SH-SY5Y human neuroblastoma cells internalized 1-μm silicon microspheres with surface charges of -70 mV (hydroxyl and carboxyl), -30 mV (amino), and +40 mV (ammonio). Uptake was rapid, within 2-4 h, and did not affect cell viability 48 h later. Flow cytometry assays indicate that SH-SY5Y cells internalize 1- and 1.5-μm microspheres at the same rate over a 24-h incubation period. Electron microscopy confirms that SH-SY5Y cells internalize 1-, 1.5-, and 2-μm microspheres. Confocal microscopy demonstrated that primary cortical neurons also internalized 1-, 1.5-, and 2-μm amino microspheres within 4 h. Finally, we injected 1-μm amino microspheres into rat striatum and found microspheres inside neurons. Overall, neurons can internalize microspheres up to 2 μm in diameter with a range of surface chemical groups and charges. These findings allow a host of neuroscience and neuroengineering applications including intracellular microdevices within neurons.

Role of surface modification in zinc oxide nanoparticles and its toxicity assessment toward human dermal fibroblast cells

The wide-scale applications of zinc oxide (ZnO) nanoparticles (NPs) in photocatalysts, gas sensors, and cosmetics may cause toxicity to humans and environments. Therefore, the aim of the present study was to reduce the toxicity of ZnO NPs by coating them with a silica (SiO2) layer, which could be used in human applications, such as cosmetic preparations. The sol-gel method was used to synthesize core ZnO with SiO2-shelled NPs (SiO2/ZnO NPs) with varying degrees of coating. Diverse studies were performed to analyze the toxicity of NPs against cells in a dose- and time-dependent manner. To ensure the decreased toxicity of the produced SiO2/ZnO NPs, cytotoxicity in membrane damage and/or intracellular reactive oxygen species (ROS) were assessed by employing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, lactate dehydrogenase, 2',7'-dichlorofluorescin, and lipid peroxide estimations. The cores of ZnO NPs exhibited cytotoxicity over time, regardless of shell thickness. Nevertheless, the thicker SiO2/ZnO NPs revealed reduced enzyme leakage, decreased peroxide production, and less oxidative stress than their bare ZnO NPs or thinner SiO2/ZnO NPs. Therefore, thicker SiO2/ZnO NPs moderated the toxicity of ZnO NPs by restricting free radical formation and the release of zinc ions, and decreasing surface contact with cells.