Real-Time Investigation of Acute Toxicity of ZnO Nanoparticles on Human Lung Epithelia with Hopping Probe Ion Conductance Microscopy

Scanning Ion Conductance Microscopy

Scanning ion conductance microscopy (SICM) has emerged as a versatile tool for studies of interfaces in biology and materials science with notable utility in biophysical and electrochemical measurements. The heart of the SICM is a nanometer-scale electrolyte filled glass pipette that serves as a scanning probe. In the initial conception, manipulations of ion currents through the tip of the pipette and appropriate positioning hardware provided a route to recording micro- and nanoscopic mapping of the topography of surfaces. Subsequent advances in instrumentation, probe design, and methods significantly increased opportunities for SICM beyond recording topography. Hybridization of SICM with coincident characterization techniques such as optical microscopy and faradaic electrodes have brought SICM to the forefront as a tool for nanoscale chemical measurement for a wide range of applications. Modern approaches to SICM realize an important tool in analytical, bioanalytical, biophysical, and materials measurements, where significant opportunities remain for further exploration. In this review, we chronicle the development of SICM from the perspective of both the development of instrumentation and methods and the breadth of measurements performed.

Scanning Ion Conductance Microscopy Study Reveals the Disruption of the Integrity of the Human Cell Membrane Structure by Oxidative DNA Damage

Oxidative stress can damage organs, tissues, and cells through reactive oxygen species (ROS) by oxidizing DNA, proteins, and lipids, thereby resulting in diseases. However, the underlying molecular mechanisms remain to be elucidated. In this study, employing scanning ion conductance microscopy (SICM), we explored the early responses of human embryonic kidney (HEK293H) cells to oxidative DNA damage induced by potassium chromate (K₂CrO₄). We found that the short term (1-2 h) exposure to a low concentration (10 μM) of K₂CrO₄ damaged the lipid membrane of HEK293H cells, resulting in structural defects and depolarization of the cell membrane and reducing cellular secretion activity shortly after the treatment. We further demonstrated that the K₂CrO₄ treatment decreased the expression of the cytoskeleton protein, β-actin, by inducing oxidative DNA damage in the exon 4 of the β-actin gene. These results suggest that K₂CrO₄ caused oxidative DNA damage in cytoskeleton genes such as β-actin and reduced their expression, thereby disrupting the organization of the cytoskeleton beneath the cell membrane and inducing cell membrane damages. Our study provides direct evidence that oxidative DNA damage disrupted human cell membrane integrity by deregulating cytoskeleton gene expression.

Bio-synthesis of Barleria gibsoni leaf extract mediated zinc oxide nanoparticles and their formulation gel for wound therapy in nursing care of infants and children

Bio-synthesis of nano-metal oxide particles is gaining lot of significance and recommended as promising substitute not only physical methods but also chemical methods. Here in, we demonstrate the nano-zinc oxide (nano-ZnO) particles were successfully prepared by an eco-friendly process using plant Barleria gibsoni (B. gibsoni) aqueous leaf extract. The water leaf extract of B. gibsoni responsible for not only reducing source but also protective agent. The prepared nano-ZnO particles were studied by UV-Vis diffuse reflectance (UV-DRS), Photoluminescence (PL), Fourier transform (FT-IR) infrared spectroscopy, X-ray diffraction spectroscopy (X-RD), transmission electron microscopy (TEM), thermal stability was studied by thermogravimetric and differential thermal (TG-DTA) analysis and particle size by zeta sizer, dynamic light scattering (DLS). UV-DRS spectrum of nano-ZnO particles showed below at wave length 400 nm. FT-IR spectra showed that plant metabolites like polyphenols, flavonoids and amino acids etc., are act as reducing and protective agent. X-RD studies revealed the formed nano-ZnO particles have hexagonal (wurtzite) structure. TEM analysis confirmed the range of nanoparticles between 30 and 80 nm, which is supported by DLS analysis. The antibacterial property of synthesized nano-ZnO particles was tested with bacterial pathogens showed good results. The developed nano-ZnO gel act as an efficient and superior another tropical antimicrobial formulations for healing of burn infections. Moreover, the formulated nano-ZnO gel exhibited a remarkable wound healing potential in rats.

Smart Scanning Ion-Conductance Microscopy Imaging Technique Using Horizontal Fast Scanning Method

To solve extended acquisition time issues inherent in the conventional hopping-scanning mode of scanning ion-conductance microscopy (SICM), a new transverse-fast scanning mode (TFSM) is proposed. Because the transverse motion in SICM is not the detection direction and therefore presents no collision problem, it has the ability to move at high speed. In TSFM, the SICM probe gradually descends in the vertical/detection direction and rapidly scans in the transverse/nondetection direction. Further, the highest point that decides the hopping height of each scanning line can be quickly obtained. In conventional hopping mode, however, the hopping height is artificially set without a priori knowledge and is typically very large. Consequently, TFSM greatly improves the scanning speed of the SICM imaging system by effectively reducing the hopping height of each pixel. This study verifies the feasibility of this novel scanning method via theoretical analysis and experimental study, and compares the speed and quality of the scanning images obtained in the TFSM with that of the conventional hopping mode. The experimental results indicate that the TFSM method has a faster scanning speed than other SICM scanning methods while maintaining the quality of the images. Therefore, TFSM provides the possibility to quickly obtain high-resolution three-dimensional topographical images of extremely complex samples.

Overview on biological implications of metal oxide nanoparticle exposure to human alveolar A549 cell line

Metal oxides (MeOx) are exponentially being used in a wide range of applications and are the largest class of commercially produced nanomaterials. This presents unprecedented human exposure. Thus, understanding nanoparticle induced cellular stress can greatly help design strategies to combat them. Scores of studies have been carried out to understand the effects of MeOx nanoparticle exposure on human alveolar cells, which are highly susceptible to aerosolized matter. There is a huge redundancy of information generated, also, a lack of a comprehensive conglomeration of this information. We have built here in a sincere summary of the cellular responses reported till date as a direct consequence of MeOx nanoparticle exposure on human alveolar (A549) cells. Detailed accounts of cellular morphology modulation, generation of reactive oxygen species (ROS) and oxidative stress, inflammation and cytokine release, genotoxic and epi-genotoxic insults, toxicological trend, nanoparticle internalization, modes of cell death, protein synthesis, and membrane damage among others are discussed. Finally, to aid predictability of the highly dynamic and multifactorial nature of this toxicity, we have hypothesized models that describe the ensuing mechanisms based on common patterns discovered throughout our literature survey.

Preparation and Biological Activity of New Collagen Composites, Part I: Collagen/Zinc Titanate Nanocomposites

The aim of this investigation was to develop new antimicrobial collagen/zinc titanate (ZnTiO3) biomaterials using a sol-gel cryogenic draying technology in keeping the native collagen activity. Broad-spectrum antimicrobial activity was demonstrated against Firmicutes (Staphylococcus epidermidis, Bacillus cereus, and Candida lusitaniae) and Gracilicutes (Escherichia coli, Salmonella enterica, and Pseudomonas putida) microorganisms. The antimicrobial activity as well as the cytotoxicity were specific for the different test microorganisms (Gram-positive and Gram-negative bacteria and fungi) and model eukaryotic cells (osteosarcoma, fibroblast, and keratinocyte cells), respectively, and both were depending on the ZnTiO3 concentration. Three mechanisms of the antimicrobial action were supposed, including (i) mechanical demolition of the cell wall and membrane by the crystal nanoparticles of the ZnTiO3 entrapped in the collagen matrix, (ii) chelation of its metal ions, and (iii) formation of free oxygen radicals due to the interaction between the microbial cells and antimicrobial agent. It was concluded that the optimal balance between antimicrobial activity and cytotoxicity could be achieved by a variation of the ZnTiO3 concentration. The antifungal and broad-spectrum antibacterial activity of the studied collagen/ZnTiO3 nanocomposites, combined with a low cytotoxicity, makes them a promising anti-infection biomaterial.

Silver nanoparticles induced oxidative and endoplasmic reticulum stresses in mouse tissues: implications for the development of acute toxicity after intravenous administration

Concerns have arisen about the health and environmental impacts of the increasing commercial use of silver nanoparticles (AgNPs). However, the toxic mechanisms and target tissues of AgNPs have not been fully defined. In this paper, we investigated the tissue toxicity of mice after intravenous administration of AgNPs at a single-dose of 0.2, 2 or 5 mg per kg (body weight), respectively. Biodistribution, endoplasmic reticulum stress, and oxidative stress were examined in mouse organs at eight hours after exposure. Stress markers, e.g. HSP70, BIP, p-IRE1, p-PERK, chop and xbp-1s proteins/genes, were significantly upregulated in a dose-dependent manner. In the liver, spleen, lung and kidney, high stress accompanied by apoptosis occurred. Low stress levels were observed in the heart and brain. Thus, it is proposed that the liver, spleen, lung and kidney are dominant target tissues of AgNP exposure. The lower stress and toxicity in the heart and brain were in agreement with lower AgNP accumulation. The present results demonstrated that AgNP exposure eventually resulted in permanent toxic damage by gradually imposing stress impacts on target organs. These findings highlight the potent applications of stress markers in future risk evaluation of silver nanoparticle toxicity.

Characterization of green synthesized nano-formulation (ZnO-A. vera) and their antibacterial activity against pathogens

The application of nanotechnology in medicine has recently been a breakthrough in therapeutic drugs formulation. This paper presents the structural and optical characterization of a new green nano-formulation (ZnO-Aloe vera) with considerable antibacterial activity against pathogenic bacteria. Its particle structure, size and morphology were characterized by XRD, TEM and SEM. And optical absorption spectra and photoluminescence were measured synchronously. Their antibacterial activity against Escherichia coli and Staphylococcus aureus was also investigated using thermokinetic profiling and agar well diffusion method. The nano-formulation is spherical shape and hexagonal with a particle size ranging from 25 to 65 nm as well as an increased crystallite size of 49 nm. For antibacterial activity, the maximum inhibition zones of ZnO and ZnO+A. vera are 18.33 and 26.45 mm for E. coli, 22.11 and 28.12 mm for S. aureus (p<0.05). Considering Pmax, Qt and k, ZnO+A. vera nano-formulation has a significant (p < 0.05) antibacterial effect against S. aureus almost at all concentration and against E. coli at 15 and 25mg/L. ZnO+A. vera nano-formulation is much more toxic against S. aureus than E. coli, with an IC50 of 13.12 mg/L and 21.31 mg/L, respectively. The overall results reveal that the ZnO-A. vera nano-formulation has good surface energy, crystallinity, transmission, and enriched antibacterial activities. Their antibacterial properties are possibly relevant to particle size, microstructural ionization, the crystal formation and the Gram property of pathogens. This ZnO-A. vera nano-formulation could be utilized effectively as a spectral and significant antibacterial agent for pathogens in future medical and environmental concerns.

Advances in studies of nanoparticle–biomembrane interactions

Nanoparticles (NPs) are widely applied in nanomedicine and diagnostics based on the interactions between NPs and the basic barrier (biomembrane). Understanding the underlying mechanism of these interactions is important for enhancing their beneficial effects and avoiding potential nanotoxicity. Experimental, mathematical and numerical modeling techniques are involved in this field. This article reviews the state-of-the-art techniques in studies of NP–biomembrane interactions with a focus on each technology's advantages and disadvantages. The aim is to better understand the mechanism of NP–biomembrane interactions and provide significant guidance for various fields, such as nanomedicine and diagnosis.

Use of non-contact hopping probe ion conductance microscopy to investigate dynamic morphology of live platelets

Circulating platelets are anucleated and multi-functional cells that participate in hemostasis and arterial thrombosis. Multiple ligands and mechanical forces activate platelets, leading to cytoskeletal rearrangement and dramatic shape-changes. Such dramatic changes in platelets membrane structures are commonly detected by optical and electron microscopy after platelets are fixed. We have recently developed a method to study the membrane morphology of live platelets using Hopping Probe Ion Conductance Microscopy (HPICM). We have successfully used this technology to study the process of platelet microvesiculation upon exposure to selective agonists. Here, we further discussed technical details of using HPICM to study platelet biology and compared results from HPICM to those from conventional atomic force microscopy and scanning electron microscopy. This method offers several advantages over current technologies. First, it monitors morphological changes of platelets in response to agonists in real time. Second, platelets can be repeatedly scanned over time without damages brought by heat and prolong light exposure. Third, there is no direct contact with platelet surface so that there will no or minimal mechanical damages brought by a cantilever of a conventional atomic force microscopy. Finally, it offers the potential to study platelet membrane ion channels, which have been technically challenging up-to-date. Our data show that HPICM has high-resolution in delineating changes of platelet morphology in response to stimulations and could help to unravel the complex role of platelet in thrombus formation.

Phosphoinositide 3-kinase pathway mediates early aldosterone action on morphology and epithelial sodium channel in mammalian renal epithelia

Involvement of phosphoinositide 3-kinases (PI3Ks) in early aldosterone action on epithelial sodium channel (ENaC) in mammalian renal epithelia was investigated by hopping probe ion conductance microscopy combined with patch-clamping in this study. Aldosterone treatment enlarged the cell volume and elevated the apical membrane of renal mpkCCDc14 epithelia, which resulted in enhancing the open probability of ENaC. Inhibition of PI3K pathway by LY294002 obviously suppressed these aldosterone-induced changes in both cell morphology and ENaC activity. These results indicated the important role of PI3K pathway in early aldosterone action and the close relationship between cell morphology and ENaC activity in mammalian renal epithelia.

ZnO nanoparticles induced effects on nanomechanical behavior and cell viability of chitosan films

The aim of this paper is to develop novel chitosan-zinc oxide nanocomposite films for biomedical applications. The films were fabricated with 1, 5, 10 and 15% w/w of zinc oxide (ZnO) nanoparticles (NPs) incorporated with chitosan (CS) using a simple method. The prepared nanocomposite films were characterized using atomic force microscopy, Raman and X-ray diffraction studies. In addition, nano and micro mechanical properties were measured. It was found that the microhardness, nanohardness and its corresponding elastic modulus increased with the increase of ZnO NP percentage in the CS films. However, the ductility of films decreased as the percentage of ZnO NPs increased. Cell attachment and cytotoxicity of the prepared films at days two and five were evaluated in vitro using osteoblasts (OBs). It was observed that OB viability decreased in films with higher than 5% ZnO NPs. This result suggests that although ZnO NPs can improve the mechanical properties of pure CS films, only a low percentage of ZnO NPs can be applied for biomedical and bioengineering applications because of the cytotoxicity effects of these particles.

Scanning ion conductance microscopy for studying biological samples

Scanning ion conductance microscopy (SICM) is a scanning probe technique that utilizes the increase in access resistance that occurs if an electrolyte filled glass micro-pipette is approached towards a poorly conducting surface. Since an increase in resistance can be monitored before the physical contact between scanning probe tip and sample, this technique is particularly useful to investigate the topography of delicate samples such as living cells. SICM has shown its potential in various applications such as high resolution and long-time imaging of living cells or the determination of local changes in cellular volume. Furthermore, SICM has been combined with various techniques such as fluorescence microscopy or patch clamping to reveal localized information about proteins or protein functions. This review details the various advantages and pitfalls of SICM and provides an overview of the recent developments and applications of SICM in biological imaging. Furthermore, we show that in principle, a combination of SICM and ion selective micro-electrodes enables one to monitor the local ion activity surrounding a living cell.