Rapid preparation of adherent mammalian cells for basic scanning electron microscopy (SEM) analysis

Multifunctional bone substitute using carbon dot and 3D printed calcium-deficient hydroxyapatite scaffolds for osteoclast inhibition and fluorescence imaging

Multifunctional bone substitute materials (BSM) have gained considerable attention with the exponential increase in aging populations. The development of hybrid materials for diagnosis and therapy of bone-related diseases and dysfunctions, especially, has been a significant challenge in the biological and the biomedical field, due to the shortage of agents with specificity and selectivity toward bone. In this study, a hybrid material, referred as Alen-CDs@CDHA, fabricated from alendronate-conjugated carbon dots (Alen-CDs) and calcium-deficient hydroxyapatite (CDHA, the mineral component of bones) scaffolds is offered as a novel multifunctional BSM for in vivo osteoclasts deactivation and fluorescence imaging. The fluorescent Alen-CDs were hydrothermally prepared using phytic acid as carbon source, followed by conjugating alendronate, for controlled alendronate release and fluorescent imaging under acidic conditions. As-prepared fluorescent Alen-CDs were consecutively immobilized on surfaces of CDHA scaffolds, exhibiting high affinity by bisphosphonate group, easily fabricated from α-tricalcium phosphate (α-TCP) paste using three-dimensional (3D) printing system. The resultant Alen-CDs@CDHA caused a significant decrease (> 50%) in viability of osteoclasts at 7 days after in vitro treatment. Furthermore, when Alen-CDs@CDHA was implanted in balb/c nude mice for in vivo evaluation, we found Alen-CDs@CDHA to be suitable for bone imaging through fluorescence signals, without necrosis or inflammatory symptoms in the epidermal tissues. Thus, these observations offer new opportunities for a novel and revolutionary use of Alen-CDs@CDHA as highly specific multifunctional BSM for bone diagnosis and imaging, and as bone-specific drug delivery materials, eventually providing anti-osteoclastogenic treatments solution for degenerative bone disorders. STATEMENT OF SIGNIFICANCE: Alen-CDs@CDHA significantly reduced the viability of osteoclasts and fluorescently imaged in vivo after transplantation, releasing drug via pH modulation. The development of fluorescence materials for bone imaging remains still a major challenge in the biomedical field owing to the shortage of selectivity and specificity. The results could lead to improvements in bone treatment strategies, as it could reduce the invasiveness of procedures and the associated negative outcomes, and increase the precision of strategies. Further, we believe that this study will be of interest to the readership of your journal as clearly focuses on the advancement of a biomaterial, where we have engineered a substance to substitute bone and integrate with a living system.

A Simple Protocol for Sample Preparation for Scanning Electron Microscopic Imaging Allows Quick Screening of Nanomaterials Adhering to Cell Surface

Preparing biological specimens for scanning electron microscopy (SEM) can be difficult to implement, as it requires specialized equipment and materials as well as the training of dedicated personnel. Moreover, the procedure often results in damage to the samples to be analyzed. This work presents a protocol for the preparation of biological samples to evaluate the adherence of nanomaterials on the cell surface using SEM. To this end, we used silicon wafers as a substrate to grow cells and replaced difficult steps such as the critical point drying of the samples in order to make the method quicker and easier to perform. The new protocol was tested using two different types of cells, i.e., human osteosarcoma cells and adipose-derived mesenchymal stem cells, and it proved that it can grossly preserve cell integrity in order to be used to estimate nanomaterials' interaction with cell surfaces.

Preparation and Preliminary Evaluation of Silver-Modified Anodic Alumina for Biomedical Applications

The present study reports a specific method for preparation of silver-modified anodic alumina substrates intended for biomaterial applications. Al2O3 coatings were obtained by anodization of technically pure aluminum alloy in sulfuric acid electrolyte. Silver deposition into the pores of the anodic structures was carried out employing in situ thermal reduction for different time periods. The obtained coatings were characterized using scanning electron microscopy (SEM), potentiodynamic scanning after 168 h in 3.5% NaCl solution and bioassays with human fibroblast and NIH/3T3 cell lines. The modified alumina substrates demonstrated better biocompatibility compared to the control anodic Al2O3 pads indicated by increased percent cell survival following in vitro culture with human and mouse fibroblasts. The Ag-deposition time did not affect considerably the biocompatibility of the investigated anodic layers. SEM analyses indicated that mouse NIH/3T3 cells and human fibroblasts adhere to the silver-coated alumina substrates retaining normal morphology and ability to form cell monolayer. Therefore, the present studies demonstrate that silver coating of anodic alumina substrates improves their biocompatibility and their eventual biomedical application.

RFP-based method for real-time tracking of invasive bacteria in a heterogeneous population of cells

Quantification of bacterial invasion into eukaryotic cells is a prerequisite to unfold the molecular mechanisms of this vector's function to obtain insights for improving its efficiency. Invasion is traditionally quantified by antibiotic protection assays that require dilution plating and counting of colony-forming units rescued from infected cells. However, to differentiate between attached and internalized bacteria vector, this assay requires supplementation by a time-consuming and tedious immunofluorescence staining, making it laborious and reduces its reliability and reproducibility. Here we describe a new red fluorescent protein (RFP)-based high-throughput and inexpensive method for tracking bacterial adherence and internalization through flow cytometry to provide a convenient and real-time quantification of bacterial invasiveness in a heterogeneous population of cells. We invaded MCF-7, A549, and HEK-293 cells with the E. coli vector and measured RFP using imaging flow cytometry. We found high cellular infection of up to 70.47% in MCF-7 compared to 27.4% and 26.2% in A549 and HEK-293 cells, respectively. The quantitative evaluation of internalized E. coli is rapid and cell-dependent, and it distinctively differentiates between attached and cytosolic bacteria while showing the degree of cellular invasiveness. This imaging flow cytometry approach can be applied broadly to study host-bacteria interaction.

An easy, fast and inexpensive method of preparing a biological specimen for scanning electron microscopy (SEM)

Biological samples usually require cumbersome preparation steps before SEM imaging. Here we propose a simple, fast and inexpensive method to prepare and visualize biological cell culture samples in a few easy steps. We have tested this method with success on several adherent breast cancer and non-adherent leukemia cell lines. This method gives results comparable to other well-established techniques, and it can be convenient in day-to-day biological sample preparation for SEM imaging.•An easy and rapid method to visualize biological specimens under SEM.•Cells are grown on carbon tapes and gold coated.•Air drying without compromising the image quality.

Visualization of Bacteria-Mediated Gene Delivery Using High-Resolution Electron and Confocal Microscopy

Visual analysis of the gene delivery process when using invasive bacteria as a vector has been conventionally performed using standard light and fluorescence microscopy. These microscopes can provide basic information on the invasiveness of the bacterial vector including the ability of the vector to successfully adhere to the cell membrane. Standard microscopy techniques however fall short when finer details including membrane attachment as well as internalization into the cytoplasm are desired. High-resolution visual analysis of bacteria-mediated gene delivery can allow accurate measurement of the adherence and internalization capabilities of engineered vectors. Here, we describe the use of scanning electron microscopy (SEM) to directly quantify vectors when they are external to the cell wall, and confocal microscopy to evaluate the vectors when they have internalized into the cytoplasm. By performing the invasion procedure on microscope coverslips, cells can be easily prepared for analysis using electron or confocal microscopes. Imaging the invasion complexes in high resolution can provide important insights into the behavior of bacterial vectors including E. coli, Listeria, and Salmonella when invading their target cells to deliver DNA and other molecules.

Fast and cost-effective preparation of plant cells for scanning electron microscopy (SEM) analysis

The analysis of plant cell structure provides valuable information about its morphological, physiological, and biochemical characteristics. Nowadays, scanning electron microscope (SEM) is widely used to provide high-resolution images at the surface of biological samples. However, biological specimens require preparation, including dehydration and coating with conductive materials for imaging by SEM. There are several techniques for providing images with maximum maintenance of cell structure and minimum cellular damage, but each requires the use of expensive and hazardous materials, which can be damaging to the cell in many cases. Therefore, the provision of new and effective preparation methods based on maintaining cell structure for imaging can be very practical. In the present study, a fast and cost-effective protocol was first performed for chemical fixation and preparation of the plant cells for imaging by SEM. Taxus baccata and Zhumeria majdae cells were chemically fixed using glutaraldehyde and then successfully dried with different percentages of ethanol including 70, 80, 90, and 100%. In addition, SEM was performed for imaging the cell surface in different micro-scales. This protocol can be used by plant cell biologists and biotechnologists who are interested in studying structural and biochemical responses of treated or stressed plant cells by SEM.

Comparative toxicity assessment of nano- and bulk-phase titanium dioxide particles on the human mammary gland in vitro

There is a major concern that exposure to titanium dioxide (TiO₂) nanoparticles (NPs) can have degrading effects on human health as well as mammary gland because of the increased use in numerous sorts of nanotech-based health care and food merchandise. Also, there is a scarcity in NP toxicity studies on the mammary gland; therefore, the aim of the present study was to compare toxicity caused by nano- and bulk-phase TiO₂ particles on the human mammary gland in vitro. In comparison to bulk-TiO₂ particles, nano-TiO₂ cause a significant (p < 0.05) reduction in viability and increased reactive oxygen species generation in the human mammary epithelial cells after a dose- (1, 2, 5, 10, 20, 50, and 100 µg/mL) and time (6, 12, 24, and 48 h)-dependent exposure. Further, an increase in genotoxicity in the mammary epithelial cells was observed as percent tail DNA and comet area was increased significantly (p < 0.05) at 12 h of exposure (10 and 100 µg/mL) with nano-TiO₂. The scanning electron microscopic examination showed that a 50 µg/mL dose of both nano-TiO₂ and bulk-TiO₂ particles cause morphological changes and retarded growth pattern of mammary epithelial cells at 12 h. Moreover, a significant (p < 0.05) increase in apoptosis at 10 µg/mL and necrosis at 50 µg/mL concentrations of nano-TiO₂ in comparison to bulk-TiO₂ was observed in mammary epithelial cells. Finally, we can conclude that the toxicity caused by nano-TiO₂ particles on the human mammary gland cells was comparatively higher than the bulk-TiO₂ particles.

Acrylamide Decreases Cell Viability, and Provides Oxidative Stress, DNA Damage, and Apoptosis in Human Colon Adenocarcinoma Cell Line Caco-2

Acrylamide (AA) toxicity remains an interesting subject in toxicological research. The aim of the research performed in this paper was to determine mechanisms of cyto- and genotoxic effects of AA on the human colon adenocarcinoma cell line Caco-2, to estimate the inhibitory concentration (IC)₅₀ values in cell viability assays, to measure the basal and oxidative DNA damage as well as the oxidative stress leading to apoptosis, and to assess the morphological changes in cells using microscopic methods. It has been proven that AA induces cytotoxic and genotoxic effects on Caco-2 cells. Higher cytotoxic activity was gained in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay compared with the PrestoBlue assay, with IC₅₀ values of 5.9 and 8.9 mM after 24 h exposure, respectively. In the single-cell gel electrophoresis assay, the greatest DNA damage was caused by the highest concentration of acrylamide equal to 12.5 mM (89.1% ± 0.9%). AA also induced oxidative DNA damage and generated reactive oxygen species (ROS), which was concentration dependent and correlated with the depletion of mitochondrial membrane potential and apoptosis induction. In the microscopic staining of cells, AA in the dosage close to the IC₅₀ induced morphological changes typical for apoptosis. Taken together, these results demonstrate that AA has a pro-oxidative effect on Caco-2 cells, leading to apoptotic cell death.

Modified mussel shell powder for microalgae immobilization to remove N and P from eutrophic wastewater

In this work, calcined mussel shell powder (CMSP) was activated by K₂CO₃ (K-CMSP), and this porous K-CMSP surface was modified by L-arginine (L-ARG) to render porous biomass a positively charged surface, which was innovatively utilized as a carrier to immobilize microalgae by adsorption via electrostatic interactions. The pore and the surface structures of CMSP and K-CMSP were characterized by XRD, FTIR, BET and SEM. The surface morphology of immobilized microalgae was visualized via using inverted optical microscope and SEM. It was found that microalgae could survive for 60 days, and the loss rate of chlorophyll-a preserved at -24 °C was the lowest, 44.73%. The microalgae could revive to normal growth level within 10 days and the cell content of microalgae was the highest at 25 °C, 2.8022 × 10⁶ cell/mL. At 25 °C, the highest removal rate of N and P was obtained about 95.0% and 88.63%, respectively.

Generation and characterization of a functional human adipose-derived multipotent mesenchymal stromal cell line

Multipotent mesenchymal stromal cells (MSC) and MSC-derived products have emerged as promising therapeutic tools. To fully exploit their potential, further mechanistic studies are still necessary and bioprocessing needs to be optimized, which requires an abundant supply of functional MSC for basic research. To address this need, here we used a novel technology to establish a human adipose-derived MSC line with functional characteristics representative of primary MSC. Primary MSC were isolated and subjected to lentiviral transduction with a library of expansion genes. Clonal cell lines were generated and evaluated on the basis of their morphology, immunophenotype, and proliferation potential. One clone (K5 iMSC) was then selected for further characterization. This clone had integrated a specific transgene combination including genes involved in stemness and maintenance of adult stem cells. Favorably, the K5 iMSC showed cell characteristics resembling juvenile MSC, as they displayed a shorter cell length and enhanced migration and proliferation compared with the non-immortalized original primary MSC (p < 0.05). Still, their immunophenotype and differentiation potential corresponded to the original primary MSC and the MSC definition criteria, and cytogenetic analyses revealed no clonal aberrations. We conclude that the technology used is applicable to generate functional MSC lines for basic research and possible future bioprocessing applications.

Enhanced steroidogenic and altered antioxidant response by ZnO nanoparticles in mouse testis Leydig cells

Zinc oxide nanoparticles (ZnO NPs) are important nanomaterials with myriad applications and in widespread use. The main aim of this study was to evaluate the direct effect of ZnO NPs on steroidogenesis by considering mouse testicular Leydig cells (TM3) as an in vitro model system. The uptake, intracellular behaviour, cytotoxicity and morphological changes induced by ZnO NPs (0-200 µg/ml) in a time-dependent manner in the TM3 were assessed. A significant ( p < 0.05) decrease in TM3 viability was observed at 2 µg/ml ZnO NP after a 1-h incubation time period. Increased antioxidant enzyme activity, namely, superoxide dismutase (SOD) and catalase, was regularly observed. Not surprisingly, apoptosis also increased significantly after a 4-h exposure period. Transmission electron micrographs illustrated that ZnO NPs were taken up by Leydig cells and resulted in the formation of autophagosomes, autolysosomes and autophagic vacuoles. Concomitant real-time data indicated that ZnO NPs significantly increased the expression of steroidogenesis-related genes (steroidogenic acute regulatory protein and cytochrome P450 side-chain cleavage enzyme) and significantly ( p < 0.05) decreased antioxidant enzyme gene (SOD) expression after a 4-h incubation period. Moreover, ZnO NPs exposure significantly increased testosterone production at 2 µg/ml concentration after a 12-h incubation period. Our findings confirm the adverse effects of ZnO NPs by being cytotoxic, enhancing apoptosis, causing steroidogenic effect in Leydig cells and increasing autophagic vacuole formation possibly via alteration of antioxidant enzyme activity in TM3 cells.