Evaluation of multiwalled carbon nanotube cytotoxicity in cultures of human brain microvascular endothelial cells grown on plastic or basement membrane

Functional Nanomaterials in Biomedicine: Current Uses and Potential Applications

Nanomaterials, that is, materials made up of individual units between 1 and 100 nanometers, have lately involved a lot of attention since they offer a lot of potential in many fields, including pharmacy and biomedicine, owed to their exceptional physicochemical properties arising from their high surface area and nanoscale size. Smart engineering of nanostructures through appropriate surface or bulk functionalization endows them with multifunctional capabilities, opening up new possibilities in the biomedical field such as biosensing, drug delivery, imaging, medical implants, cancer treatment and tissue engineering. This article highlights up-to-date research in nanomaterials functionalization for biomedical applications. A summary of the different types of nanomaterials and the surface functionalization strategies is provided. Besides, the use of nanomaterials in diagnostic imaging, drug/gene delivery, regenerative medicine, cancer treatment and medical implants is reviewed. Finally, conclusions and future perspectives are provided.

In vitro toxicity of carbon nanotubes: a systematic review

Carbon nanotube (CNT) toxicity-related issues provoke many debates in the scientific community. The controversial and disputable data about toxicity doses, proposed hazard effects, and human health concerns significantly restrict CNT applications in biomedical studies, laboratory practices, and industry, creating a barrier for mankind in the way of understanding how exactly the material behaves in contact with living systems. Raising the toxicity question again, many research groups conclude low toxicity of the material and its potential safeness at some doses for contact with biological systems. To get new momentum for researchers working on the intersection of the biological field and nanomaterials, i.e., CNT materials, we systematically reviewed existing studies with in vitro toxicological data to propose exact doses that yield toxic effects, summarize studied cell types for a more thorough comparison, the impact of incubation time, and applied toxicity tests. Using several criteria and different scientific databases, we identified and analyzed nearly 200 original publications forming a "golden core" of the field to propose safe doses of the material based on a statistical analysis of retrieved data. We also differentiated the impact of various forms of CNTs: on a substrate and in the form of dispersion because in both cases, some studies demonstrated good biocompatibility of CNTs. We revealed that CNTs located on a substrate had negligible impact, i.e., 90% of studies report good viability and cell behavior similar to control, therefore CNTs could be considered as a prospective conductive substrate for cell cultivation. In the case of dispersions, our analysis revealed mean values of dose/incubation time to be 4-5 μg mL-1 h-1, which suggested the material to be a suitable candidate for further studies to get a more in-depth understanding of its properties in biointerfaces and offer CNTs as a promising platform for fundamental studies in targeted drug delivery, chemotherapy, tissue engineering, biosensing fields, etc. We hope that the present systematic review will shed light on the current knowledge about CNT toxicity, indicate "dark" spots and offer possible directions for the subsequent studies based on the demonstrated here tabulated and statistical data of doses, cell models, toxicity tests, viability, etc.

The mechanism of cell death induced by silver nanoparticles is distinct from silver cations

Background

Precisely how silver nanoparticles (AgNPs) kill mammalian cells still is not fully understood. It is not clear if AgNP-induced damage differs from silver cation (Ag⁺), nor is it known how AgNP damage is transmitted from cell membranes, including endosomes, to other organelles. Cells can differ in relative sensitivity to AgNPs or Ag⁺, which adds another layer of complexity to identifying specific mechanisms of action. Therefore, we determined if there were specific effects of AgNPs that differed from Ag⁺ in cells with high or low sensitivity to either toxicant.

Methods

Cells were exposed to intact AgNPs, Ag⁺, or defined mixtures of AgNPs with Ag⁺, and viability was assessed. The level of dissolved Ag⁺ in AgNP suspensions was determined using inductively coupled plasma mass spectrometry. Changes in reactive oxygen species following AgNP or Ag⁺ exposure were quantified, and treatment with catalase, an enzyme that catalyzes the decomposition of H₂O₂ to water and oxygen, was used to determine selectively the contribution of H₂O₂ to AgNP and Ag⁺ induced cell death. Lipid peroxides, formation of 4-hydroxynonenol protein adducts, protein thiol oxidation, protein aggregation, and activation of the integrated stress response after AgNP or Ag⁺ exposure were quantified. Lastly, cell membrane integrity and indications of apoptosis or necrosis in AgNP and Ag⁺ treated cells were examined by flow cytometry.

Results

We identified AgNPs with negligible Ag⁺ contamination. We found that SUM159 cells, which are a triple-negative breast cancer cell line, were more sensitive to AgNP exposure less sensitive to Ag⁺ compared to iMECs, an immortalized, breast epithelial cell line. This indicates that high sensitivity to AgNPs was not predictive of similar sensitivity to Ag⁺. Exposure to AgNPs increased protein thiol oxidation, misfolded proteins, and activation of the integrated stress response in AgNP sensitive SUM159 cells but not in iMEC cells. In contrast, Ag⁺ cause similar damage in Ag⁺ sensitive iMEC cells but not in SUM159 cells. Both Ag⁺ and AgNP exposure increased H₂O₂ levels; however, treatment with catalase rescued cells from Ag⁺ cytotoxicity but not from AgNPs. Instead, our data support a mechanism by which damage from AgNP exposure propagates through cells by generation of lipid peroxides, subsequent lipid peroxide mediated oxidation of proteins, and via generation of 4-hydroxynonenal (4-HNE) protein adducts.

Conclusions

There are distinct differences in the responses of cells to AgNPs and Ag⁺. Specifically, AgNPs drive cell death through lipid peroxidation leading to proteotoxicity and necrotic cell death, whereas Ag⁺ increases H₂O₂, which drives oxidative stress and apoptotic cell death. This work identifies a previously unknown mechanism by which AgNPs kill mammalian cells that is not dependent upon the contribution of Ag⁺ released in extracellular media. Understanding precisely which factors drive the toxicity of AgNPs is essential for biomedical applications such as cancer therapy, and of importance to identifying consequences of unintended exposures.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-021-00430-1.

Carbon Nanotubes: Smart Drug/Gene Delivery Carriers

The unique properties of carbon nanotubes (CNTs) (such as their high surface to volume ratios, enhanced conductivity and strength, biocompatibility, ease of functionalization, optical properties, etc.) have led to their consideration to serve as novel drug and gene delivery carriers. CNTs are effectively taken up by many different cell types through several mechanisms. CNTs have acted as carriers of anticancer molecules (including docetaxel (DTX), doxorubicin (DOX), methotrexate (MTX), paclitaxel (PTX), and gemcitabine (GEM)), anti-inflammatory drugs, osteogenic dexamethasone (DEX) steroids, etc. In addition, the unique optical properties of CNTs have led to their use in a number of platforms for improved photo-therapy. Further, the easy surface functionalization of CNTs has prompted their use to deliver different genes, such as plasmid DNA (PDNA), micro-RNA (miRNA), and small interfering RNA (siRNA) as gene delivery vectors for various diseases such as cancers. However, despite all of these promises, the most important continuous concerns raised by scientists reside in CNT nanotoxicology and the environmental effects of CNTs, mostly because of their non-biodegradable state. Despite a lack of widespread FDA approval, CNTs have been studied for decades and plenty of in vivo and in vitro reports have been published, which are reviewed here. Lastly, this review covers the future research necessary for the field of CNT medicine to grow even further.

Hypoxia-mimicking cobalt-doped multi-walled carbon nanotube nanocomposites enhance the angiogenic capacity of stem cells from apical papilla

Adequate and timely vascularization is crucial for the success of dental pulp tissue engineering. Hypoxia, an important driving force of angiogenesis, plays an important role in this process. However, few studies have investigated the fabrication of hypoxia-simulating biomaterials for dental applications. In this study, a novel hypoxia-mimicking, multi-walled carbon nanotubes/cobalt (MWCNTs/Co) nanocomposite was prepared using the metal-organic framework (MOF) route for the in situ insertion of MWCNTs into Co₃O₄ polyhedra. The obtained nanocomposites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Cobalt ion release of MWCNTs/Co was analyzed in vitro. Cell viability and proliferation were assessed by culturing stem cells from apical papilla (SCAP) with MWCNTs/Co nanocomposites. The angiogenic capacity of SCAP after exposure to nanocomposites was evaluated by enzyme-linked immunosorbent assay (ELISA), western blotting and the Matrigel angiogenesis assay. Our results proved that the synthesized MWCNTs/Co nanocomposites possessed a well-designed connecting structure and could release cobalt ions in a sustained way. The MWCNTs/Co nanocomposites at 50 μg/mL significantly upregulated hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) protein expression in SCAP, with no apparent cellular cytotoxicity. The conditioned medium collected from SCAP treated with MWCNTs/Co markedly promoted endothelial cells vessel formation. In conclusion, hypoxia-mimicking MWCNTs/Co nanocomposites exhibit promising angiogenic potential for dental tissue engineering and might provide an alternative solution for translational applications.

Multi-walled carbon nanotubes decrease neuronal NO synthase in 3D brain organoids

Multi-walled carbon nanotubes (MWCNTs) might induce the dysfunction of neuronal NO synthase (nNOS) and impair the function of brains. But to the best of our knowledge, this conclusion was made by using laboratory animals or conventional nerve cell cultures; however, these models might not reflect the complex conditions of human brains. Recently, the development of 3D brain organoids (also known as organotypic cultures) derived from human induced pluripotent stem cells (iPSCs) provides a platform to investigate the behaviors of human brains in vitro. In this study, we investigated the toxicity of MWCNTs to 3D brain organoids which expressed the cortical layer markers. It was shown that MWCNTs induced cytotoxicity to 3D brain organoids but not in dose-dependent manner. Exposure to high level of MWCNTs (64 μg/mL) reduced the levels of intracellular NO but increased superoxide. As the mechanism, 64 μg/mL MWCNTs significantly reduced the protein level of nNOS. The nNOS regulators nuclear factor kappa-B (NF-κB) proteins were significantly induced by MWCNTs, whereas Kruppel-like factor 4 (KLF4) proteins were reduced particularly after exposure to low level of MWCNTs (16 μg/mL). The results from fluorescence micro-optical sectioning tomography (MOST) confirmed the decrease of nNOS proteins, not only at the out-layers that directly contacted MWCNTs, but also at the inner-layers. Combined, our results suggested that MWCNTs could decrease nNOS activity by inducing oxidative stress and modulating NF-κB-KLF4 pathway. This study also showed the potential of 3D brain organoids in mechanism-based toxicology studies.

Cellular Responses of Human Lymphatic Endothelial Cells to Carbon Nanomaterials

One of the greatest challenges to overcome in the pursuit of the medical application of carbon nanomaterials (CNMs) is safety. Particularly, when considering the use of CNMs in drug delivery systems (DDSs), evaluation of safety at the accumulation site is an essential step. In this study, we evaluated the toxicity of carbon nanohorns (CNHs), which are potential DDSs, using human lymph node endothelial cells that have been reported to accumulate CNMs, as a comparison to fibrous, multi-walled carbon nanotubes (MWCNTs) and particulate carbon black (CB). The effect of different surface characteristics was also evaluated using two types of CNHs (untreated and oxidized). In the fibrous MWCNT, cell growth suppression, as well as expression of inflammatory cytokine genes was observed, as in previous reports. In contrast, no significant toxicity was observed for particulate CB and CNHs, which was different from the report of CB cytotoxicity in vascular endothelial cells. These results show that (1) lymph endothelial cells need to be tested separately from other endothelial cells for safety evaluation of nanomaterials, and (2) the potential of CNHs as DDSs.

Different influence of sulfated chitosan with different sulfonic acid group sites on HUVECs behaviors

The vascularization within the scaffold is still a significant challenge in tissue engineering applications. Sulfated chitosan (SCS) as an amazing substance have been used in tissue engineering to stimulate angiogenesis. However, it is not clear whether they have difference in the ability to promote vascularization of SCS with different sulfonic acid group sites. The aim of this study was to evaluate human umbilical vein endothelial cells (HUVECs) viability and differentiation in vitro, affected by three types of sulfated chitosan' i.e. 2-N-6-O-sulfated chitosan (2,6-SCS), 3'6-O-sulfated chitosan (3,6-SCS) and 6-O-sulfated chitosan (6-SCS). The results are showed that all the SCS possesses excellent biological properties to promote HUVECs viability and proliferation. Especially, 2,6-SCS promotes desirable intracellular nitric oxide secretion and capillary tube formation. Meanwhile, 2,6-SCS up-regulate the related gene and protein expression compared with other sulfonic acid group sites SCS and heparin. Therefore, 2,6-SCS is a promising substitute material for angiogenesis and as aqueous formulation can be employed to fabrication functionalization scaffold surface with promoted angiogenesis.

Sulfated chitosan coated polylactide membrane enhanced osteogenic and vascularization differentiation in MC3T3-E1s and HUVECs co-cultures system

This study aimed to compare the effects of the two type chitosan derivatives, sulfated chitosan (SCS) and phosphorylated chitosan (PCS), coated on poly(d,l-lactide) (PDLLA) membrane via polydopamine, respectively, on vascularization and osteogenesis in vitro. Mouse preosteoblast cells (MC3T3-E1s) and human umbilical vein endothelial cells (HUVECs) were used as co-cultures system. The effects of two type membranes on calcium deposition, alkaline phosphatase (ALP) activity, vascularization related factors nitric oxide (NO) and angiogenic growth factor vascular endothelial growth factor (VEGF) were assessed. The changes of osteogenic and angiogenic related gene, and protein expression were evaluated too. In fact, SCS modified PDLLA membrane had the highest related gene and protein expression than other PDLLA membranes. Our results demonstrated that the SCS maybe a promising matrix for bone regeneration by co-cultures of ECs and OCs than PCS.

Nanoformulations for glioblastoma multiforme: a new hope for treatment

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor in adults, associated with a high mortality rate and a survival of between 12 and 15 months after diagnosis. Due to current treatment limitations involving surgery, radiotherapy and chemotherapy with temozolamide, there is a high rate of treatment failure and recurrence. To try to overcome these limitations nanotechnology has emerged as a novel alternative. Lipid, polymeric, silica and magnetic nanoparticles, among others, are being developed to improve GBM treatment and diagnosis. These nanoformulations have many advantages, including lower toxicity, biocompatibility and the ability to be directed toward the tumor. This article reviews the progress that have been made and the large variety of nanoparticles currently under study for GBM.