Interaction of silica nanoparticles with tau proteins and PC12 cells: Colloidal stability, thermodynamic, docking, and cellular studies

Prospects and hazards of silica nanoparticles: Biological impacts and implicated mechanisms

With the thrive of nanotechnology, silica nanoparticles (SiNPs) have been extensively adopted in the agriculture, food, cosmetic, and even biomedical industries. Due to the mass production and use, SiNPs inevitably entered the environment, resulting in ecological toxicity and even posing a threat to human health. Although considerable investigations have been conducted to assess the toxicity of SiNPs, the correlation between SiNPs exposure and consequent health risks remains ambiguous. Since the biological impacts of SiNPs can differ from their design and application, the toxicity assessment for SiNPs may be extremely difficult. This review discussed the application of SiNPs in different fields, especially their biomedical use, and documented their potential release pathways into the environment. Meanwhile, the current process of assessing SiNPs-related toxicity on various model organisms and cell lines was also detailed, thus estimating the health threats posed by SiNPs exposure. Finally, the potential toxic mechanisms of SiNPs were also elaborated based on results obtained from both in vivo and in vitro trials. This review generally summarizes the biological effects of SiNPs, which will build up a comprehensive perspective of the application and toxicity of SiNPs.

Silicon dioxide nanoparticles adsorption alters the secondary and tertiary structures of catalase and undermines its activity

The expanding production and use of nanomaterials in various fields caused big concern for human health. Oxidative stress is the most frequently described mechanism of nanomaterial toxicity. A state of oxidative stress can be defined as the imbalance of reactive oxygen species (ROS) production and antioxidant enzyme activities. Although nanomaterials-triggered ROS generation has been extensively investigated, little is known regarding the regulation of antioxidant enzyme activities by nanomaterials. This study used two typical nanomaterials, SiO₂ nanoparticles (NPs) and TiO₂ NPs, to predict their binding affinities and interactions with antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD). The molecular docking results showed that CAT and SOD had different binding sites, binding affinity, and interaction modes with SiO₂ NPs and TiO₂ NPs. The binding affinities of the two NPs to CAT were more potent than those to SOD. Consistently, the experimental work indicated NPs adsorption caused the perturbation of the second and tertiary structures of both enzymes and thus resulted in the loss of enzyme activities.

Cytotoxicity towards Breast Cancer Cells of Pluronic F-127/Hyaluronic Acid Hydrogel Containing Nitric Oxide Donor and Silica Nanoparticles Loaded with Cisplatin

The incorporation of both nitric oxide (NO) donor (S-nitrosoglutathione, GSNO) and silica nanoparticles loaded with cisplatin (SiO₂@CisPt NPs) into a polymeric matrix represents a suitable approach to creating a drug-delivery system with sustained and localized drug release against tumor cells. Herein, we report the synthesis, characterization, and cytotoxicity evaluation of Pluronic F-127/hyaluronic acid hydrogel containing GSNO and SiO₂@CisPt NPs against breast cancer cells. SiO₂@CisPt NPs were successfully synthesized, revealing a spherical morphology with an average size of 158 ± 20 nm. Both GSNO and SiO₂@CisPt NPs were incorporated into the thermoresponsive Pluronic/hyaluronic hydrogel for sustained and localized release of both NO and cisplatin. The kinetics of NO release from a hydrogel matrix revealed spontaneous and sustained release of NO at the millimolar range for 24 h. The MTT assay showed concentration-dependent cytotoxicity of the hydrogel. The combination of GSNO and SiO₂@CisPt incorporated into a polymeric matrix decreased the cell viability 20% more than the hydrogel containing only GSNO or SiO₂@CisPt. At 200 µg/mL, this combination led to a critical cell viability of 30%, indicating a synergistic effect between GSNO and SiO₂@CisPt NPs in the hydrogel matrix, and, therefore, highlighting the potential application of this drug-delivery system in the field of biomedicine.

Probing the Interactions of Lamotrigine and Phenobarbital with Tau Protein: Experimental and Molecular Modeling Studies

Tau, as a small protein in neurons, plays a main role in stabilizing and assembling the internal microtubules. Here, the effects of antiepileptic drugs, including lamotrigine (LTG) and phenobarbital (PHB), on tau protein structure have been investigated by surface plasmon resonance (SPR), fluorescence spectroscopy along molecular modeling. Fluorescence data analysis revealed that both drugs quench the intrinsic emission intensity of tau protein via a static quenching mechanism. Analysis of SPR data at three different temperatures revealed that binding of LTG and PHB to tau protein leads to a decrease and increase in equilibrium constants (K_D) values with increasing temperature, respectively. Therefore, the affinity of LTG decreases and PHB increases with increasing temperature. In addition, molecular docking studies indicated that both LTG and PHB bind to the S1 pocket of tau protein. Our data demonstrated the preventive effect of two important antiepileptic pharmaceuticals on the aggregation of tau protein. Given that any damage to the tau protein possibly leads to neurodegenerative diseases, this study can provide useful and important information and a basis for further research and study to treat tauopathy.

Tin oxide nanoparticles trigger the formation of amyloid β oligomers/protofibrils and underlying neurotoxicity as a marker of Alzheimer's diseases

Alzheimer's disease (AD) is known as one of the most common forms of dementia, and oligomerization of amyloid β (Aβ₄₂) peptides can result in the onset of AD. Tin oxide nanoparticles (SnO₂ NPs) showed several applications in biomedical fields can trigger unwanted interaction with proteins and inducing protein aggregation. Herein, we synthesized SnO₂ NPs via the hydrothermal method and characterized by UV-visible, XRD, FTIR, TEM, and DLS techniques. Afterward, the formation of Aβ₄₂ amyloid oligomers/protofibrils treated alone and with SnO₂ NPs was explored by ThT and Nile red fluorescence and CD spectroscopic methods along with TEM imaging. The neurotoxicity of different spices of Aβ₄₂ samples against PC-12 cells was then explored by MTT and caspase-3 activity assays. The characterization of SnO₂ NPs confirmed the successful synthesis of crystalline NPs (20-30 nm). Different biophysical and cellular analyses indicated that SnO₂ NPs accelerated Aβ₄₂ fibrillogenesis and promoted amyloid oligomers/protofibrils cytotoxicity. As compared to the Aβ₄₂ samples grown alone, the ThT and ANS fluorescence intensity along with ellipticity results indicated the promotory effect of SnO₂ NPs on the formation of oligomers/protofibrils. Also, the cellular results showed that the treated Aβ₄₂ samples with SnO₂ NPs further reduced cell viability through activation of caspase-3. In conclusion, SnO₂ NPs greatly accelerate the fibrillation of Aβ₄₂ peptides and lead to the formation of more toxic species. The present data may offer further warrants into nano-based systems for biomedical applications in the central nervous system.

The application of multifunctional nanomaterials in Alzheimer's disease: A potential theranostics strategy

By virtue of their small size, nanomaterials can cross the blood-brain barrier and, when modified to target specific cells or regions, can achieve high bioavailability at the intended site of action. Modified nanomaterials are therefore promising agents for the diagnosis and treatment of neurodegenerative diseases such as Alzheimer's disease (AD). Here we review the roles and mechanisms of action of nanomaterials in AD. First, we discuss the general characteristics of nanomaterials and their application to nanomedicine. Then, we summarize recent studies on the diagnosis and treatment of AD using modified nanomaterials. These studies indicate that using nanomaterials is a potential strategy for AD treatment by slowing the progression of AD through enhanced therapeutic effects.

Interaction of nanoparticles with biological macromolecules: a review of molecular docking studies

The high frequency of using engineered nanoparticles in various medical applications entails a deep understanding of their interaction with biological macromolecules. Molecular docking simulation is now widely used to study the binding of different types of nanoparticles with proteins and nucleic acids. This helps not only in understanding the mechanism of their biological action but also in predicting any potential toxicity. In this review, the computational techniques used in studying the nanoparticles interaction with biological macromolecules are covered. Then, a comprehensive overview of the docking studies performed on various types of nanoparticles will be offered. The implication of these predicted interactions in the biological activity and/or toxicity is also discussed for each type of nanoparticles.

The dual effect of natural organic matter on the two-step internalization process of Au@Sio2 in freshwater

Dissolved organic matter (DOM) in aquatic ecosystems reshapes the surface of nanoparticles (NPs) greatly. Understanding how these changes influence the bioavailability of NPs is critical for accurately predicting the ecological risks of NPs. A quantitative model based on the two-step internalization process enabled the differentiation between the adhesion ability of NPs to membranes and the internalization capacity. Using protozoa Tetrahymena thermophila as the test organism, fluorescein isothiocyanate-modified silica NPs (FITC-SiO₂) and silica-coated gold NPs (Au@SiO₂) were prepared to validate the model and study the influence of DOM on uptake. DOM reduced the ability of Au@SiO₂ to adhere onto cell membranes and the inhibitory effect of bovine serum albumin (BSA) and β-lactoglobulin was higher due to their higher molecular weights and the weaker interaction. Moreover, DOM increased the internalization capacity. 80% Au@SiO₂ was internalized in the presence of humic acid (HA), over 90% Au@SiO₂ was internalized in the presence of the two proteins, whereas only 60% were internalized by the control group. Next, the specific recognition of the cell internalization in the presence of DOM was confirmed. We concluded that the traditional "accumulation" may misestimate the true biological effect caused by NPs coated with DOM. NPs coated with highly bioavailable DOM pose a greater risk to aquatic ecosystems because they are more likely to be internalized by living organisms.

Doxorubicin-loaded pH-responsive nanoparticles coated with chlorin e6 for drug delivery and synergetic chemo-photodynamic therapy

The integration of chemotherapy drugs and photosensitizers to form versatile nanoplatforms for achieving chemo-photodynamic synergetic therapy has shown great superiority in tumor theranostic applications. We constructed pH-responsive nanoparticles (DOX/PB NPs) encapsulating the chemotherapeutic drug doxorubicin (DOX) into the cores of PLGA NPs coated with bovine serum albumin (BSA) via a water-in-oil (W/O/W) emulsion method. A simple and efficient chemo-photodynamic synergetic nanoplatform (DOX/PB@Ce6 NPs) was obtained by the adsorption of photosensitizer chlorin e6 (Ce6) onto the surface of the DOX/PB NPs. With optimal size, pH-responsive drug release behavior and excellent singlet oxygen production, the DOX/PB@Ce6 NPs have the potential to enhance anti-tumor efficiency. The cellular uptake, cytotoxicity, chemo-photodynamic synergetic effect and biocompatibility of the NPs were evaluated based on HeLa cells via in vitro experiments. The in vitro chemo-photodynamic synergetic experiments indicated that the DOX/PB@Ce6 NPs had remarkable cancer cell killing efficiency under laser irradiation. Notably, by hemolysis assay, all the NPs displayed excellent blood compatibility and were expected to be applicable for intravenous injection. In summary, the designed DOX/PB@Ce6 NPs multifunctional theranostic nanoplatform had excellent reactive oxygen species generation and would be a potential therapeutic platform for chemo-photodynamic synergetic therapy.

Spectroscopic approach for the interaction of carbon nanoparticles with cytochrome c and BY-2 cells: Protein structure and mitochondrial function

In this study, we employed multiple spectroscopic methods to analyze the effects of carbon nanoparticles (CNPs) on structure of cytochrome c (Cyt c) and mitochondrial function in plant cells. The tertiary structures of aromatic amino acid in Cyt c were not changed after addition of CNPs. Cyt c was found to be absorbed on the surfaces of CNPs in a non-linear manner and only bound Cyt c can be reduced. In addition, the binding of Cyt c was found to increase the diameter of CNPs at lower concentrations. The redox potential of Cyt c was almost not affected after treatment with CNPs. There were no obvious differences in cellular ATP after exposure to CNPs, and the mitochondrial membrane potential (MMP) was significantly decreased once the CNPs concentration exceeded 31.25 μg/mL. The levels of reactive oxygen species (ROS) also were increased in BY-2 cells. Taken together, these findings provide basis for the interactions between CNPs and Cyt c, as well as the effect of CNPs treatment on the mitochondria function in plant cells.

Silica nanoparticles induce conformational changes of tau protein and oxidative stress and apoptosis in neuroblastoma cell line

The adverse effects of SiO₂ NPs on the biological systems like nervous system have not been well explored. This study aimed to evaluate the toxicity of SiO₂ NPs on the nervous system in vitro. Therefore, human tau protein and neuroblastoma cell line (SH-SY5Y) were used as targets. In this study we examined the side effects of SiO₂ NPs on tau protein structure using several techniques including CD, ANS fluorescence, UV-vis (360 nm), Congo red absorbance, TEM, and molecular dynamic. Also, the cytotoxicity effects of SiO₂ NPs against SH-SY5Y cell line were evaluated using MTT, ROS and apoptotic assays. Spectroscopic and molecular dynamic investigations indicated that natively unfolded structure of tau in the presence of SiO₂ NPs experienced a partially folded and amorphous aggregated structure. Cellular assay demonstrated that SiO₂ NPs exerted cytotoxic effect on SH-SY5Y cells through ROS accumulation and induction of apoptosis. Overall, these findings proved that SiO₂ NPs could induce adverse effects on tau structure and SH-SY5Y cell integrity. Moreover, further studies are required to elucidate the molecular mechanism of SiO₂ NPs-induced side effects in vivo.