Cytotoxicity and Genotoxicity of Carbon Nanomaterials

Carbon Nanomaterial Fluorescent Probes and Their Biological Applications

Fluorescent carbon nanomaterials have broadly useful chemical and photophysical attributes that are conducive to applications in biology. In this review, we focus on materials whose photophysics allow for the use of these materials in biomedical and environmental applications, with emphasis on imaging, biosensing, and cargo delivery. The review focuses primarily on graphitic carbon nanomaterials including graphene and its derivatives, carbon nanotubes, as well as carbon dots and carbon nanohoops. Recent advances in and future prospects of these fields are discussed at depth, and where appropriate, references to reviews pertaining to older literature are provided.

An overview on atmospheric carbonaceous particulate matter into carbon nanomaterials: A new approach for air pollution mitigation

Air pollutants consisting of atmospheric particulate matter (PM) poses a major threat to the environment and human health. However, due to their carbonaceous nature, these atmospheric PM can also be used as a precursor for fabrication of high-valued carbon nanomaterials (CNMs) leading to waste to wealth as well as mitigation of air pollution. Over the few years, various results have been reported on different types of physical and chemical methods for the synthesis of CNMs from atmospheric particulate matter with the help of top down and bottom up methods; however, there is a lack of review on these innovative processes and outcome in order to assess their feasibility and suitability for further investigation. This review critically assesses the synthesis, identification, and characterization of different types of CNMs derived from the atmospheric PM. The fascinating fluorescence properties along with the novel multifarious applications of such PM-derived CNMs are also extensively discussed in this review work. This unique review will certainly help to make a new avenue for air pollution mitigation through conversion of PMs in to value added nanomaterials (VNMs) and will boost the research activity in the field of environmental nanotechnology for a cleaner environment.

Conductive Nanodiamond-Based Detection of Neurotransmitters: One Decade, Few Sensors

Nanodiamond (ND) is a class of carbon nanomaterial with covalently connected sp³ carbon atoms in its core and an sp² carbon adorned surface via edge defects or doping. Endogenous chemicals that provoke physiological responses in the human system called neurotransmitters (NTs) have been detected with several sensors with carbon-based nanomaterials. Nanodiamonds (NDs), another class of carbon nanomaterial, have shown the requisite surface area and electrocatalytic activity toward NTs in the past decade. Surprisingly, only a few electrochemical ND based NT sensors are available. This work briefly looked into the performance of the available sensors, NT and ND interactions, and the possible reason for data paucity on the subject matter.

Biocompatible nucleus-targeted graphene quantum dots for selective killing of cancer cells via DNA damage

Graphene quantum dots (GQDs) are nano-sized graphene slices. With their small size, lamellar and aromatic-ring structure, GQDs tend to enter into the cell nucleus and interfere with DNA activity. Thus, GQD alone is expected to be an anticancer reagent. Herein, we developed GQDs that suppress the growth of tumor by selectively damaging the DNA of cancer cells. The amine-functionalized GQDs were modified with nucleus targeting TAT peptides (TAT-NGs) and further grafted with cancer-cell-targeting folic acid (FA) modified PEG via disulfide linkage (FAPEG-TNGs). The resulting FAPEG-TNGs exhibited good biocompatibility, nucleus uptake, and cancer cell targeting. They adsorb on DNA via the π-π and electrostatic interactions, which induce the DNA damage, the upregulation of the cell apoptosis related proteins, and the suppression of cancer cell growth, ultimately. This work presents a rational design of GQDs that induce the DNA damage to realize high therapeutic performance, leading to a distinct chemotherapy strategy for targeted tumor therapy.

Biomineralization inspired engineering of nanobiomaterials promoting bone repair

A biomineralization processes is disclosed for engineering nanomaterials that support bone repair. The material was fabricated through a hot press process using electrospun poly(lactic acid) (PLA) matrix covered with hybrid composites of carbon nanotubes/graphene nanoribbons (GNR) and nanohydroxyapatite (nHA). Various scaffolds were devised [nHA/PLA, PLA/GNR, and PLA/nHA/GNR (1 and 3%)] and their structure and morphology characterized through Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), and Atomic force microscope (AFM). Moreover, thorough biocompatibility and toxicity studies were performed. Here, in vivo studies on toxicity and cytotoxicity were conducted in aqueous dispersions of the biomaterials at concentrations of 30, 60, and 120 μg/mL using the Allium cepa test. Further toxicity studies were performed through hemolysis toxicity tests and genotoxicity tests evaluating the damage index and damage frequencies of DNAs through comet assays with samples of the animals' peripheral blood, marrow, and liver. Additionally, the regenerative activity of the scaffolds was analyzed by measuring the cortical tibiae of rats oophorectomized implanted with the biomaterials. Biochemical analyzes [glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT), urea, calcium, phosphorus, and alkaline phosphatase (ALP)] were also performed on blood samples. The results suggested a toxicity and cytotoxicity level for the GNR biomaterials at a concentration of 60 and 120 μg/mL, but non-toxicity and cytotoxicity for the 30 μg/mL concentration. The scaffolds obtained at a concentration of 0.3 mg/cm² were not toxic in the hemolysis test and demonstrated no cytotoxicity, genotoxicity, and mutagenicity in the blood, marrow, and liver analyzes of the animals, corroborating data from the biochemical markers of GPT, GOT, and urea. Tissue regeneration was performed in all groups and was more pronounced in the group containing the combination of nHA/GNR (3%), which is consistent with the data obtained for the calcium, serum phosphorus, and ALP concentrations. Consequently, the study indicates that the engineered nanobiomaterial is a promising candidate for bone tissue repair and regenerative applications. STATEMENT OF SIGNIFICANCE: The scientific contribution of this study is the engineering of a synthetic hybrid biomaterial, in nanoscale by a pressing and heating process. A biodegradable polymeric matrix was covered on both sides with a carbonated hybrid bioceramic/graphene nanoribbons (GNR), which has hydrophilic characteristics, with chemical elements stoichiometrically similar to bone mineral composition. The nanomaterial displayed promising bone regeneration ability, which is the first example to be used in an osteoporotic animal model. Moreover, detailed biocompatibility and toxicity studies were performed on the nanomaterials and their compositions, which is of great interest for the scientific community.

Environmental and toxicological assessment of nanodiamond-like materials derived from carbonaceous aerosols

Carbonaceous aerosols (CAs) are ubiquitous and among the most significant environmental materials found in ambient air, mainly derived from anthropogenic sources (biomass burning, industrial activity, vehicle emissions, etc.). Elemental carbon (black carbon) and organic carbons are the major constituents of CAs. Due to their toxic effects, they are considered as high-risk compounds for human health. The key objective of the present work is to conduct a feasibility study for the conversion of CAs (TSP and PM₁₀) into a value-added carbon nanostructured product by using a chemical method. High resolution-transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), Raman spectroscopy, Fourier transforms infrared spectroscopy (FT-IR), X-ray photoelectron spectrometer (XPS), ultraviolet-visible spectroscopy (UV-visible), fluorescence spectroscopy (FL), and Zeta potential analyses indicated the formation of carbon nanomaterials with crystalline phases, which exhibit the characteristics of nanodiamonds (NDs). The HR-TEM image analysis showed that the nominal size of the CAs-derived NDs ranged from 4 to 17 nm composed of mainly carbon and oxygen. The FT-IR and XPS analysis indicated that the NDs are highly functionalized with an oxygen-containing functional group. The CAs-derived NDs showed the property of blue-fluorescence with excitation dependent. In the cytotoxicity and genotoxicity study, the NDs obtained was observed to be biocompatible and suitable for bioimaging applications. This result provides a new avenue for the conversion of CAs to high-value products leading to the mitigation of atmospheric pollution.

Engineering the Interface: Nanodiamond Coating on 3D-Printed Titanium Promotes Mammalian Cell Growth and Inhibits Staphylococcus aureus Colonization

Additively manufactured selective laser melted titanium (SLM-Ti) opens the possibility of tailored medical implants for patients. Despite orthopedic implant advancements, significant problems remain with regard to suboptimal osseointegration at the interface between the implant and the surrounding tissue. Here, we show that applying a nanodiamond (ND) coating onto SLM-Ti scaffolds provides an improved surface for mammalian cell growth while inhibiting colonization of Staphylococcus aureus bacteria. Owing to the simplicity of our methodology, the approach is suitable for coating SLM-Ti geometries. The ND coating achieved 32 and 29% increases in cell density of human dermal fibroblasts and osteoblasts, respectively, after 3 days of incubation compared with the uncoated SLM-Ti substratum. This increase in cell density complements an 88% reduction in S. aureus detected on the ND-coated SLM-Ti substrata. This study paves a way to create facile antifouling SLM-Ti structures for biomedical implants.

A Novel High Mechanical Property PLGA Composite Matrix Loaded with Nanodiamond-Phospholipid Compound for Bone Tissue Engineering

A potential bone tissue engineering material was produced from a biodegradable polymer, poly(lactic-co-glycolic acid) (PLGA), loaded with nanodiamond phospholipid compound (NDPC) via physical mixing. On the basis of hydrophobic effects and physical absorption, we modified the original hydrophilic surface of the nanodiamond (NDs) with phospholipids to be amphipathic, forming a typical core-shell structure. The ND-phospholipid weight ratio was optimized to generate sample NDPC50 (i.e., ND-phospholipid weight ratio of 100:50), and NDPC50 was able to be dispersed in a PLGA matrix at up to 20 wt %. Compared to a pure PLGA matrix, the introduction of 10 wt % of NDPC (i.e., sample NDPC50-PF10) resulted in a significant improvement in the material's mechanical and surface properties, including a decrease in the water contact angle from 80 to 55°, an approximately 100% increase in the Young's modulus, and an approximate 550% increase in hardness, thus closely resembling that of human cortical bone. As a novel matrix supporting human osteoblast (hFOB1.19) growth, NDPC50-PFs with different amounts of NDPC50 demonstrated no negative effects on cell proliferation and osteogenic differentiation. Furthermore, we focused on the behaviors of NDPC-PFs implanted into mice for 8 weeks and found that NDPC-PFs induced acceptable immune response and can reduce the rapid biodegradation of PLGA matrix. Our results represent the first in vivo research on ND (or NDPC) as nanofillers in a polymer matrix for bone tissue engineering. The high mechanical properties, good in vitro and in vivo biocompatibility, and increased mineralization capability suggest that biodegradable PLGA composite matrices loaded with NDPC may potentially be useful for a variety of biomedical applications, especially bone tissue engineering.

Electrospun fish gelatin fibrous scaffolds with improved bio-interactions due to carboxylated nanodiamond loading

This work emphasizes the potential of COOH-functionalized nanodiamond (NDs) particles to improve bio-interactions when embedded into fish gelatin electrospun fibers.

The hemocompatibility of oxidized diamond nanocrystals for biomedical applications

Low-dimensional carbon-based nanomaterials have recently received enormous attention for biomedical applications. However, increasing evidence indicates that they are cytotoxic and can cause inflammatory responses in the body. Here, we show that monocrystalline nanodiamonds (NDs) synthesized by high-pressure-high-temperature (HPHT) methods and purified by air oxidation and strong oxidative acid treatments have excellent hemocompatibility with negligible hemolytic and thrombogenic activities. Cell viability assays with human primary endothelial cells suggested that the oxidized HPHT-NDs (dimensions of 35-500 nm) are non-cytotoxic. No significant elevation of the inflammatory cytokine levels of IL-1β and IL-6 was detected in mice after intravenous injection of the nanocrystals in vivo. Using a hindlimb-ischemia mouse model, we demonstrated that 35-nm NDs after covalent conjugation with polyarginine are useful as a drug delivery vehicle of heparin for prolonged anticoagulation treatment. The present study lays a solid foundation for further therapeutic applications of NDs in biomedicine.

Tracking the engraftment and regenerative capabilities of transplanted lung stem cells using fluorescent nanodiamonds

Lung stem/progenitor cells are potentially useful for regenerative therapy, for example in repairing damaged or lost lung tissue in patients. Several optical imaging methods and probes have been used to track how stem cells incorporate and regenerate themselves in vivo over time. However, these approaches are limited by photobleaching, toxicity and interference from background tissue autofluorescence. Here we show that fluorescent nanodiamonds, in combination with fluorescence-activated cell sorting, fluorescence lifetime imaging microscopy and immunostaining, can identify transplanted CD45(-)CD54(+)CD157(+) lung stem/progenitor cells in vivo, and track their engraftment and regenerative capabilities with single-cell resolution. Fluorescent nanodiamond labelling did not eliminate the cells' properties of self-renewal and differentiation into type I and type II pneumocytes. Time-gated fluorescence imaging of tissue sections of naphthalene-injured mice indicates that the fluorescent nanodiamond-labelled lung stem/progenitor cells preferentially reside at terminal bronchioles of the lungs for 7 days after intravenous transplantation.

Genotoxicity of carbon nanofibers: are they potentially more or less dangerous than carbon nanotubes or asbestos?

The production of carbon nanofibers and nanotubes (CNF/CNT) and their composite products is increasing globally. CNF are generating great interest in industrial sectors such as energy production and electronics, where alternative materials may have limited performance or are produced at a much higher cost. However, despite the increasing industrial use of carbon nanofibers, information on their potential adverse health effects is limited. In the current study, we examine the cytotoxic and genotoxic potential of carbon-based nanofibers (Pyrograf®-III) and compare this material with the effects of asbestos fibers (crocidolite) or single-walled carbon nanotubes (SWCNT). The genotoxic effects in the lung fibroblast (V79) cell line were examined using two complementary assays: the comet assay and micronucleus (MN) test. In addition, we utilized fluorescence in situ hybridization to detect the chromatin pan-centromeric signals within the MN indicating their origin by aneugenic (chromosomal malsegregation) or clastogenic (chromosome breakage) mechanisms. Cytotoxicity tests revealed a concentration- and time-dependent loss of V79 cell viability after exposure to all tested materials in the following sequence: asbestos>CNF>SWCNT. Additionally, cellular uptake and generation of oxygen radicals was seen in the murine RAW264.7 macrophages following exposure to CNF or asbestos but not after administration of SWCNT. DNA damage and MN induction were found after exposure to all tested materials with the strongest effect seen for CNF. Finally, we demonstrated that CNF induced predominantly centromere-positive MN in primary human small airway epithelial cells (SAEC) indicating aneugenic events. Further investigations are warranted to elucidate the possible mechanisms involved in CNF-induced genotoxicity.

Using carbon nanotubes to induce micronuclei and double strand breaks of the DNA in human cells

Carbon nanotubes are unique one-dimensional macromolecules with promising applications in biology and medicine. Since their toxicity is still under debate, here we present a study investigating the genotoxic properties of purified single wall carbon nanotubes (SWCNTs), multiwall carbon nanotubes (MWCNTs), and amide functionalized purified SWCNTs on cultured human lymphocytes employing cytokinesis block micronucleus assay and enumeration of gamma H2AX foci as a measure of double strand breaks (DSBs) of the DNA in normal human fibroblasts. SWCNTs induce micronuclei (MN) formation in lymphocytes and decrease the proliferation potential (CBPI) of cells. In a fibroblast cell line the same dose of SWCNTs induces gamma H2AX foci 2.7-fold higher than in a control. Amide functionalized purified SWCNTs behave differently: they do not disturb the cell proliferation potential of harvested lymphocytes, but induce micronuclei to a higher extent than SWCNTs. When applied on fibroblasts, amide functionalized SWCNTs also induce gamma H2AX foci, 3.18-fold higher than the control. The cellular effects of MWCNTs display the broad spectrum of clastogenic properties seen as the highest incidence of induced lymphocyte micronuclei and anaphase bridges among nuclei in binucleated cells. Surprisingly, the incidence of induced gamma H2AX foci was not as high as was expected by the micronucleus test, which indicates that MWCNTs act as clastogen and aneugen agents simultaneously. Biological endpoints investigated in this study indicate a close relationship between the electrochemical properties of carbon nanotubes and observed genotoxicity.