Cytotoxic assessment of carbon nanotube interaction with cell cultures

Bactericidal Effect and Cytotoxicity of Graphene Oxide/Silver Nanocomposites

To tackle the proliferation of pathogenic microorganisms without relying on antibiotics, innovative materials boasting antimicrobial properties have been engineered. This study focuses on the development of graphene oxide/silver (GO/Ag) nanocomposites, derived from partially reduced graphene oxide adorned with silver nanoparticles. Various nanocomposites with different amounts of silver (GO/Ag-1, GO/Ag-2, GO/Ag-3, and GO/Ag-4) were synthesized, and their antibacterial efficacy was systematically studied. The silver nanoparticles were uniformly deposited on the partially reduced graphene oxide surface, exhibiting spherical morphologies with an average size of 25 nm. The nanocomposites displayed potent antibacterial properties against both gram-positive bacteria (S. aureus and B. subtilis) and gram-negative bacteria (E. coli and S. enterica) as confirmed by minimum inhibition concentration (MIC) studies and time-dependent experiments. The optimal MIC for Gram-positive bacteria was 62.5 μg/mL and for Gram-negative bacteria was 125 μg/mL for the GO/Ag nanocomposites. Bacterial cells that encountered the nanocomposite films exhibited significantly greater inhibitory effects compared to those exposed to conventional antibacterial materials. Furthermore, the cytotoxicity of these nanocomposites was assessed using human epithelial cells (HEC), revealing that GO/Ag-1 and GO/Ag-2 exhibited lower toxicity levels toward HEC and remained compatible even at higher dilution rates. This study underscores the potential of GO/Ag-based nanocomposites as versatile materials for antibacterial applications, particularly as biocompatible wound dressings, offering promising prospects for wound healing and infection control.

Fanarraga M. Carbon nanotubes targeted to the tumor microenvironment inhibit metastasis in a preclinical model of melanoma

Despite notable progress in cancer therapy, metastatic diseases continue to be the primary cause of cancer-related mortality. Multi-walled carbon nanotubes (MWCNTs) can enter tissues and cells and interfere with the dynamics of the cytoskeletal nanofilaments biomimetically. This endows them with intrinsic anti-tumoral effects comparable to those of microtubule-binding chemotherapies such as Taxol®. In this study, our focus was on exploring the potential of oxidized MWCNTs in selectively targeting the vascular endothelial growth factor receptor (VEGFR). Our objective was to evaluate their effectiveness in inhibiting metastatic growth by inducing anti-proliferative, anti-migratory, and cytotoxic effects on both cancer and tumor microenvironment cells. Our findings demonstrated a significant reduction of over 80 % in malignant melanoma lung metastases and a substantial enhancement in overall animal welfare following intravenous administration of the targeted biodegradable MWCNTs. Furthermore, the combination of these nanomaterials with the conventional chemotherapy agent Taxol® yielded a remarkable 90 % increase in the antimetastatic effect. These results highlight the promising potential of this combined therapeutic approach against metastatic disease and are of paramount importance as metastasis is responsible for nearly 60,000 deaths each year.

Effectiveness In Vivo and In Vitro of Polymeric Nanoparticles as a Drug Release System in the Treatment of Leishmaniasis

Leishmaniasis is a neglected disease caused by the parasite of the genus Leishmania. Current treatment regimens are obsolete and cause several side effects, promoting poor patient compliance, in addition to the vast majority already having the potential for resistance. Therefore, polymeric nanoparticles emerge as one of the viable alternatives to overcome existing limitations, through passive or active vectorization. This review aims to summarize the latest studies of polymeric nanoparticles as an alternative treatment for leishmaniasis. In the first section, the main pharmacokinetic and pharmacodynamic challenges of current drugs are reported. The second section details how nanoparticles with and without functionalization are efficient in the treatment of leishmaniasis, discussing the characteristics of the polymer in the formulation. In this way, polymeric nanoparticles can improve the physicochemical properties of leishmanicidal drugs, improving solubility and stability, as well as improve the release of these drugs, directly or indirectly reaching monocytes/macrophages. 64.28% drugs were focused on the treatment of visceral leishmaniasis, and 28.57% on cutaneous leishmaniasis. The most chosen polymers in the literature are chitosan (35.71%) and PLGA (35.71%), the others represented 14.30% drugs, with all able to manage the drug release and increase the in vitro and/or in vivo efficacy of the original molecule. However, there are several barriers for these nanoformulations to cross laboratory research and is necessary more in-depth studies about the metabolites and degradation pathways of the polymers used in the formulations and plasma proteomics studies.

Nanoplatforms for the Delivery of Nucleic Acids into Plant Cells

Nanocarriers are widely used for efficient delivery of different cargo into mammalian cells; however, delivery into plant cells remains a challenging issue due to physical and mechanical barriers such as the cuticle and cell wall. Here, we discuss recent progress on biodegradable and biosafe nanomaterials that were demonstrated to be applicable to the delivery of nucleic acids into plant cells. This review covers studies the object of which is the plant cell and the cargo for the nanocarrier is either DNA or RNA. The following nanoplatforms that could be potentially used for nucleic acid foliar delivery via spraying are discussed: mesoporous silica nanoparticles, layered double hydroxides (nanoclay), carbon-based materials (carbon dots and single-walled nanotubes), chitosan and, finally, cell-penetrating peptides (CPPs). Hybrid nanomaterials, for example, chitosan- or CPP-functionalized carbon nanotubes, are taken into account. The selected nanocarriers are analyzed according to the following aspects: biosafety, adjustability for the particular cargo and task (e.g., organelle targeting), penetration efficiency and ability to protect nucleic acid from environmental and cellular factors (pH, UV, nucleases, etc.) and to mediate the gradual and timely release of cargo. In addition, we discuss the method of application, experimental system and approaches that are used to assess the efficiency of the tested formulation in the overviewed studies. This review presents recent progress in developing the most promising nanoparticle-based materials that are applicable to both laboratory experiments and field applications.

Discovery of new pyridine heterocyclic hybrids; design, synthesis, dynamic simulations, and in vitro and in vivo breast cancer biological assays

Pyridine is a nitrogen bearing heterocyclic scaffold that shows a wide range of biological activities. The pyridine nucleus has become an interesting target for medicinal chemistry researchers worldwide. Several pyridine derivatives exhibited good anticancer effects against diverse cell lines. Therefore, to explore new anticancer pyridine entities, novel pyridine derivatives were designed and synthesized and evaluated for their anticancer abilities in vitro and in vivo. All of the target compounds were evaluated against three different human cancer cell lines (Huh-7, A549 and MCF-7) via MTT assay. Most of the compounds exhibited significant cytotoxic activities. Compounds 3a, 3b, 5a and 5b showed superior antiproliferative activities to Taxol. Where, compound 3b showed IC₅₀ values of 6.54, 15.54 and 6.13 μM compared to Taxol (6.68, 38.05, 12.32 μM) against Huh-7, A549 and MCF-7, respectively. Also, tubulin polymerization assay was carried out. The most potent compounds 3a, 3b, 5a and 5b could significantly inhibit tubulin polymerization with IC₅₀ values of 15.6, 4.03, 6.06 and 12.61 μM, respectively. Compound 3b exhibited the highest tubulin polymerization inhibitory effect with an IC₅₀ value of 4.03 μM compared to combretastatin (A-4) (1.64 μM). Molecular modeling studies of the designed compounds confirmed that most of the compounds made the essential binding interactions compared to the reference compound which assisted in the prediction of the structure requirements for the detected anticancer activity. Finally, in vivo studies showed that compound 3b could significantly inhibit breast cancer.

Functionalized carbon nanotube microfibers for chronic neural implants

BACKGROUND

Much progress has been made at the interface between neural tissue and electrodes for neurophysiology. However, there continues to be a need for novel materials that integrate well with the nervous system and facilitate neural recordings with longer-term sustainability and stability. Such materials have the potential to improve clinical approaches and provide important tools for basic neuroscience research.

NEW METHOD

In this paper, we explore the use of dry-spun untreated or functionalized carbon nanotube fibers as implantable electrodes for neural recordings from insects over extended time periods.

RESULTS

Measurements of fly eyes responding to light flashes illustrate the suitability of these materials for recording both the low- and high-frequency components of neural signals. Repeated recordings show good sustainability, especially with functionalized carbon nanotube fibers. In particular, recordings from the optic lobes of Madagascar hissing cockroaches last for at least 8 weeks.

COMPARISON WITH EXISTING METHOD(S)

Electrophysiological research continues to rely heavily on metal electrodes that are good for short-lived preparations but less suitable for longer-term recordings, as scar tissue formation and cytotoxicity tend to cause a gradual reduction in signals.

CONCLUSIONS

Functionalized carbon nanotubes are a promising novel material that can be used to obtain long-term or repeated stable recordings, which are necessary for longitudinal studies, or to maintain other neural tissue interfaces such as those in insect-machine hybrid robots. The introduced insect preparation can also be used for the relatively rapid and cost-efficient testing of novel electrode materials.

Enhanced mesenchymal stem cells growth on antibacterial microgrooved electrospun zinc chloride/polycaprolactone conduits for peripheral nerve regeneration

In this study, we have investigated the effect of adding zinc chloride (ZnCl2) on polycaprolactone (PCL) before and after electrospinning. The rheological properties and conductivity of ZnCl2/PCL solutions were measured prior to the electrospinning process. The resultant electrospun mats were characterized by SEM, contact angle, FTIR, XRD, mechanical properties, as well as its antibacterial and stem cell proliferation assessment were tested. It was found that the fibers became finer by increasing the zinc salt content. Moreover, stability increased slightly up to 5% Zn-PCL and also the hydrophilicity has been enhanced by 52%. By adding ZnCl2, the degradation rate and mechanical properties were significantly increased. Also, the resultant mats have shown antibacterial properties against S. aureus than E. coli. From the stem cells proliferation study, it can be observed that by increasing ZnCl2, the stem cells proliferation was significantly increased. Grooved multichannel nerve conduits were successfully fabricated by rolling the electrospun mats produced on corn husks which has shown better cell alignment and attachment. Hence, adding zinc chloride is a facile biocompatible enhancement to polycaprolactone nanofibers to be used in nerve regeneration.

Toward Spontaneous Neuronal Differentiation of SH-SY5Y Cells Using Novel Three-Dimensional Electropolymerized Conductive Scaffolds

Neuroblastoma-derived SH-SY5Y cells have become an excellent model for nervous system regeneration to treat neurodegenerative disorders. Many approaches achieved a mature population of derived neurons in in vitro plates. However, the importance of the third dimension in tissue regeneration has become indispensable to achieve a potential implant to replace the damaged tissue. Therefore, we have prepared porous 3D structures composed uniquely of carbon nanotubes (CNT) and poly(3,4-ethylenedioxythiophene) (PEDOT) that show great potential in the tridimensional differentiation of SH-SY5Y cells into mature neurons. The scaffolds have been manufactured through electropolymerization by applying 1.2 V in a three-electrode cell using a template of sucrose/CNT as a working electrode. By this method, PEDOT/CNT 3D scaffolds were obtained with homogeneous porosities and high conductivity. In vitro analyses showed that an excellent biocompatibility of the scaffold and the presence of high amount of β-tubulin class III and MAP-II target proteins that mainly expresses in neurons, suggesting the differentiation into neuronal cells already after a week of incubation.

Development of an accurate method for dispersion and quantification of carbon nanotubes in biological media

Understanding the biological effects triggered by nanomaterials is crucial, not only in nanomedicine but also in toxicology. The dose-response relation is relevant in biological tests due to its use for determining appropriate dosages for drugs and toxicity limits. Carbon nanotubes can trigger numerous unusual biological effects, many of which could have unique applications in biotechnology and medicine. However, their resuspension in saline solutions and the accurate determination of their concentration after dispersion in biological media are major handicaps to identify the magnitude of the response of organisms as a function of this exposure. This difficulty has led to inconsistent results and misinterpretations of their in vivo behavior, limiting their potential use in nanomedicine. The lack of a suitable protocol that allows comparing different studies of the content of carbon nanotubes and their adequate resuspension in culture cell media gives rise to this study. Here, we describe a methodology to functionalize, resuspend and determine the carbon nanotube concentration in biocompatible media based on UV-Vis spectroscopy. This method allows us to accurately estimate the concentration of these resuspended carbon nanotubes, after removing bundles and micrometric aggregates, which can be used as a calibration standard, for dosage-dependent studies in biological systems. This method can also be extended to any other nanomaterial to properly quantify the actual concentration.

Synthesis of Biogenic Gold Nanoparticles from Terminalia mantaly Extracts and the Evaluation of Their In Vitro Cytotoxic Effects in Cancer Cells

Scientists have demonstrated the potential of plant materials as ‘green’ reducing and stabilizing agents for the synthesis of gold nanoparticles (AuNPs) and opened new ecofriendly horizons to develop effective and less harmful treatment strategies. The current study demonstrated the use of Terminalia mantaly (TM) extracts to synthesize AuNPs with enhanced cytotoxic effects. The TM-AuNPs were synthesized at 25 and 70 °C using water (_WTM) and methanolic (_MTM) extracts of the leaf, root and stem/bark parts of the plant. The TM-AuNPs were characterized using UV–visible spectrophotometry, dynamic light scattering (DLS), transmission electron microscopy, energy dispersive X-ray (EDX), selection area electron diffraction (SAED) and Fourier transform infrared (FTIR) spectroscopy. Majority of the TM-AuNPs were spherical with a mean diameter between 22.5 and 43 nm and were also crystalline in nature. The cytotoxic effects of TM-AuNPs were investigated in cancer (Caco-2, MCF-7 and HepG2) and non-cancer (KMST-6) cell lines using the MTT assay. While the plant extracts showed some cytotoxicity towards the cancer cells, some of the TM-AuNPs were even more toxic to the cells. The IC₅₀ values (concentrations of the AuNPs that inhibited 50% cell growth) as low as 0.18 µg/mL were found for TM-AuNPs synthesized using the root extract of the plant. Moreover, some of the TM-AuNPs demonstrated selective toxicity towards specific cancer cell types. The study demonstrates the potential of TM extracts to produce AuNPs and describe the optimal conditions for AuNPs using TM extracts. The toxicity of some the TM-AuNPs can possibly be explored in the future as an antitumor treatment.

Quantitative Flow Cytometric Evaluation of Oxidative Stress and Mitochondrial Impairment in RAW 264.7 Macrophages after Exposure to Pristine, Acid Functionalized, or Annealed Carbon Nanotubes

Conventional nanotoxicological assays are subjected to various interferences with nanoparticles and especially carbon nanotubes. A multiparametric flow cytometry (FCM) methodology was developed here as an alternative to quantify oxidative stress, mitochondrial impairment, and later cytotoxic and genotoxic events. The experiments were conducted on RAW264.7 macrophages, exposed for 90 min or 24 h-exposure with three types of multiwalled carbon nanotubes (MWCNTs): pristine (Nanocyl™ CNT), acid functionalized (CNTf), or annealed treatment (CNTa). An original combination of reactive oxygen species (ROS) probes allowed the simultaneous quantifications of broad-spectrum ROS, superoxide anion (O₂^•-), and hydroxyl radical (•OH). All MWCNTs types induced a slight increase of broad ROS levels regardless of earlier antioxidant catalase activity. CNTf strongly stimulated the O₂^•- production. The •OH production was downregulated for all MWCNTs due to their scavenging capacity. The latter was quantified in a cell-free system by electron paramagnetic resonance spectroscopy (EPR). Further FCM-based assessment revealed early biological damages with a mitochondrial membrane potential collapse, followed by late cytotoxicity with chromatin decondensation. The combined evaluation by FCM analysis and cell-free techniques led to a better understanding of the impacts of MWCNTs surface treatments on the oxidative stress and related biological response.

Applications of Carbon Nanotubes in Bone Tissue Regeneration and Engineering: Superiority, Concerns, Current Advancements, and Prospects

With advances in bone tissue regeneration and engineering technology, various biomaterials as artificial bone substitutes have been widely developed and innovated for the treatment of bone defects or diseases. However, there are no available natural and synthetic biomaterials replicating the natural bone structure and properties under physiological conditions. The characteristic properties of carbon nanotubes (CNTs) make them an ideal candidate for developing innovative biomimetic materials in the bone biomedical field. Indeed, CNT-based materials and their composites possess the promising potential to revolutionize the design and integration of bone scaffolds or implants, as well as drug therapeutic systems. This review summarizes the unique physicochemical and biomedical properties of CNTs as structural biomaterials and reinforcing agents for bone repair as well as provides coverage of recent concerns and advancements in CNT-based materials and composites for bone tissue regeneration and engineering. Moreover, this review discusses the research progress in the design and development of novel CNT-based delivery systems in the field of bone tissue engineering.

Three-Dimensional Conductive Scaffolds as Neural Prostheses Based on Carbon Nanotubes and Polypyrrole

Three-dimensional scaffolds for cellular organization need to enjoy a series of specific properties. On the one hand, the morphology, shape and porosity are critical parameters and eventually related with the mechanical properties. On the other hand, electrical conductivity is an important asset when dealing with electroactive cells, so it is a desirable property even if the conductivity values are not particularly high. Here, we construct three-dimensional (3D) porous and conductive composites, where C8-D1A astrocytic cells were incubated to study their biocompatibility. The manufactured scaffolds are composed exclusively of carbon nanotubes (CNTs), a most promising material to interface with neuronal tissue, and polypyrrole (PPy), a conjugated polymer demonstrated to reduce gliosis, improve adaptability, and increase charge-transfer efficiency in brain-machine interfaces. We developed a new and easy strategy, based on the vapor phase polymerization (VPP) technique, where the monomer vapor is polymerized inside a sucrose sacrificial template containing CNT and an oxidizing agent. After removing the sucrose template, a 3D porous scaffold was obtained and its physical, chemical, and electrical properties were evaluated. The obtained scaffold showed very low density, high and homogeneous porosity, electrical conductivity, and Young's Modulus similar to the in vivo tissue. Its high biocompatibility was demonstrated even after 6 days of incubation, thus paving the way for the development of new conductive 3D scaffolds potentially useful in the field of electroactive tissues.

Live Imaging of Label-Free Graphene Oxide Reveals Critical Factors Causing Oxidative-Stress-Mediated Cellular Responses

The interest in graphene and its translation into commercial products has been expanding at a high pace. Based on previously described pulmonary safety concerns for carbon nanomaterials, there is a great need to define parameters guiding interactions between graphene-based materials and the pulmonary system. The aim of the present study was to determine the importance of two critical parameters: lateral dimensions of the material and coating with proteins in relation to each other and their pulmonary impact. Endotoxin-free materials with distinct lateral dimensions, s-GO (50-200 nm) and l-GO (5-15 μm), were produced and thoroughly characterized. Exploiting intrinsic fluorescence of graphene oxide (GO) and using confocal live-cell imaging, the behavior of the cells in response to the material was visualized in real time. Although BEAS-2B cells internalized GO efficiently, l-GO was linked to higher plasma membrane interactions correlated with elevated reactive oxygen species (ROS) levels, pro-inflammatory response, and greater cytotoxicity, in agreement with the oxidative stress paradigm. For both GO types, the presence of serum alleviated lipid peroxidation of plasma membrane and decreased intracellular ROS levels. However, protein coating was not enough to entirely mitigate toxicity and inflammatory response induced by l-GO. In vitro results were validated in vivo, as l-GO was more prone to induce pulmonary granulomatous response in mice compared to s-GO. In conclusion, the lateral dimension of GO played a more important role than serum protein coating in determining biological responses to the material. It was also demonstrated that time-lapse imaging of live cells interacting with label-free GO sheets can be used as a tool to assess GO-induced cytotoxicity.

Toxicological assessment of multi-walled carbon nanotubes in vitro: potential mitochondria effects on male reproductive cells

Multi-walled carbon nanotubes (MWCNTs) have been widely used in many fields and were reported to cause reversible testis damage in mice at high-dose. However the reproductive effects of low dose MWCNTs remained elusive. Herein, we used the mice spermatocyte cell line (GC-2spd) to assess the reproductive effects of MWCNTs. Size distribution, zeta potential, and intensity of MWCNTs were characterized. A maximal concentration of 0.5 μg/mL MWCNTs was found to be nonlethal to GC-2spd. At this dose, cell cycles and the ROS levels were in normal status. We also found MWCNTs accumulated in mitochondria, which caused potential mitochondrial DNA damage in spermatocyte. Furthermore, the expression level of mitochondria-related genes, the oxygen consumption rate, and cellular ATP content were declined compared to controls, even at the nonlethal dose. Our results suggested for the first time that, in germ cells, mitochondrion was a cellular organelle that accumulated MWCNTs.

Water-based and biocompatible 2D crystal inks for all-inkjet-printed heterostructures

Exploiting the properties of two-dimensional crystals requires a mass production method able to produce heterostructures of arbitrary complexity on any substrate. Solution processing of graphene allows simple and low-cost techniques such as inkjet printing to be used for device fabrication. However, the available printable formulations are still far from ideal as they are either based on toxic solvents, have low concentration, or require time-consuming and expensive processing. In addition, none is suitable for thin-film heterostructure fabrication due to the re-mixing of different two-dimensional crystals leading to uncontrolled interfaces and poor device performance. Here, we show a general approach to achieve inkjet-printable, water-based, two-dimensional crystal formulations, which also provide optimal film formation for multi-stack fabrication. We show examples of all-inkjet-printed heterostructures, such as large-area arrays of photosensors on plastic and paper and programmable logic memory devices. Finally, in vitro dose-escalation cytotoxicity assays confirm the biocompatibility of the inks, extending their possible use to biomedical applications.

Zebrafish: A complete animal model to enumerate the nanoparticle toxicity

Presently, nanotechnology is a multi-trillion dollar business sector that covers a wide range of industries, such as medicine, electronics and chemistry. In the current era, the commercial transition of nanotechnology from research level to industrial level is stimulating the world’s total economic growth. However, commercialization of nanoparticles might offer possible risks once they are liberated in the environment. In recent years, the use of zebrafish (Danio rerio) as an established animal model system for nanoparticle toxicity assay is growing exponentially. In the current in-depth review, we discuss the recent research approaches employing adult zebrafish and their embryos for nanoparticle toxicity assessment. Different types of parameters are being discussed here which are used to evaluate nanoparticle toxicity such as hatching achievement rate, developmental malformation of organs, damage in gill and skin, abnormal behavior (movement impairment), immunotoxicity, genotoxicity or gene expression, neurotoxicity, endocrine system disruption, reproduction toxicity and finally mortality. Furthermore, we have also highlighted the toxic effect of different nanoparticles such as silver nanoparticle, gold nanoparticle, and metal oxide nanoparticles (TiO₂, Al2O₃, CuO, NiO and ZnO). At the end, future directions of zebrafish model and relevant assays to study nanoparticle toxicity have also been argued.

Nanomedicine in the application of uveal melanoma

Rapid advances in nanomedicine have significantly changed many aspects of nanoparticle application to the eye including areas of diagnosis, imaging and more importantly drug delivery. The nanoparticle-based drug delivery systems has provided a solution to various drug solubility-related problems in ophthalmology treatment. Nanostructured compounds could be used to achieve local ocular delivery with minimal unwanted systematic side effects produced by taking advantage of the phagocyte system. In addition, the in vivo control release by nanomaterials encapsulated drugs provides prolong exposure of the compound in the body. Furthermore, certain nanoparticles can overcome important body barriers including the blood-retinal barrier as well as the corneal-retinal barrier of the eye for effective delivery of the drug. In summary, the nanotechnology based drug delivery system may serve as an important tool for uveal melanoma treatment.

Carbon nanotubes' surface chemistry determines their potency as vaccine nanocarriers in vitro and in vivo

Carbon nanotubes (CNTs) have shown marked capabilities in enhancing antigen delivery to antigen presenting cells. However, proper understanding of how altering the physical properties of CNTs may influence antigen uptake by antigen presenting cells, such as dendritic cells (DCs), has not been established yet. We hypothesized that altering the physical properties of multi-walled CNTs (MWNTs)-antigen conjugates, e.g. length and surface charge, can affect the internalization of MWNT-antigen by DCs, hence the induced immune response potency. For this purpose, pristine MWNTs (p-MWNTs) were exposed to various chemical reactions to modify their physical properties then conjugated to ovalbumin (OVA), a model antigen. The yielded MWNTs-OVA conjugates were long MWNT-OVA (~386nm), bearing net positive charge (5.8mV), or short MWNTs-OVA (~122nm) of increasing negative charges (-23.4, -35.8 or -39mV). Compared to the short MWNTs-OVA bearing high negative charges, short MWNT-OVA with the lowest negative charge demonstrated better cellular uptake and OVA-specific immune response both in vitro and in vivo. However, long positively-charged MWNT-OVA showed limited cellular uptake and OVA specific immune response in contrast to short MWNT-OVA displaying the least negative charge. We suggest that reduction in charge negativity of MWNT-antigen conjugate enhances cellular uptake and thus the elicited immune response intensity. Nevertheless, length of MWNT-antigen conjugate might also affect the cellular uptake and immune response potency; highlighting the importance of physical properties as a consideration in designing a MWNT-based vaccine delivery system.

Synthesis of double-clickable functionalised graphene oxide for biological applications

Azide- and alkyne-double functionalised graphene oxide (Click(2) GO) was synthesised and characterised with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA) and Raman spectroscopy. Fourteen-percentage increase in azide content was found, after pre-treatment of GO with meta-chloroperoxybenzoic acid (mCPBA), determined with elemental analysis. No effect on A549 cell viability was found, up to 100 μg mL(-1) and 72 h of incubation, determined with the modified lactate dehydrogenase (mLDH) assay. Two sequential copper(i) catalysed azide-alkyne cycloaddition (CuAAC) reactions were performed to conjugate the propargyl-modified blood-brain barrier targeting peptide Angiopep-2, and a bis-azide polyethylene glycol (MW = 3500), to the Click(2) GO. The final conjugate was characterised with ATR-FTIR and TGA.

Nanovehicles as a novel target strategy for hyperthermic intraperitoneal chemotherapy: a multidisciplinary study of peritoneal carcinomatosis

In general, detection of peritoneal carcinomatosis (PC) occurs at the late stage when there is no treatment option. In the present study, we designed novel drug delivery systems that are functionalized with anti-CD133 antibodies. The C1, C2 and C3 complexes with cisplatin were introduced into nanotubes, either physically or chemically. The complexes were reacted with anti-CD133 antibody to form the labeled product of A0-o-CX-chem-CD133. Cytotoxicity screening of all the complexes was performed on CHO cells. Data showed that both C2 and C3 Pt-complexes are more cytotoxic than C1. Flow-cytometry analysis showed that nanotubes conjugated to CD133 antibody have the ability to target cells expressing the CD133 antigen which is responsible for the emergence of resistance to chemotherapy and disease recurrence. The shortest survival rate was observed in the control mice group (K3) where no hyperthermic intraperitoneal chemotherapy procedures were used. On the other hand, the longest median survival rate was observed in the group treated with A0-o-C1-chem-CD133. In summary, we designed a novel drug delivery system based on carbon nanotubes loaded with Pt-prodrugs and functionalized with anti-CD133 antibodies. Our data demonstrates the effectiveness of the new drug delivery system and provides a novel therapeutic modality in the treatment of melanoma.

Kupffer Cell Isolation for Nanoparticle Toxicity Testing

The large majority of in vitro nanotoxicological studies have used immortalized cell lines for their practicality. However, results from nanoparticle toxicity testing in immortalized cell lines or primary cells have shown discrepancies, highlighting the need to extend the use of primary cells for in vitro assays. This protocol describes the isolation of mouse liver macrophages, named Kupffer cells, and their use to study nanoparticle toxicity. Kupffer cells are the most abundant macrophage population in the body and constitute part of the reticulo-endothelial system (RES), responsible for the capture of circulating nanoparticles. The Kupffer cell isolation method reported here is based on a 2-step perfusion method followed by purification on density gradient. The method, based on collagenase digestion and density centrifugation, is adapted from the original protocol developed by Smedsrød et al. designed for rat liver cell isolation and provides high yield (up to 14 x 10(6) cells per mouse) and high purity (>95%) of Kupffer cells. This isolation method does not require sophisticated or expensive equipment and therefore represents an ideal compromise between complexity and cell yield. The use of heavier mice (35-45 g) improves the yield of the isolation method but also facilitates remarkably the procedure of portal vein cannulation. The toxicity of functionalized carbon nanotubes f-CNTs was measured in this model by the modified LDH assay. This method assesses cell viability by measuring the lack of structural integrity of Kupffer cell membrane after incubation with f-CNTs. Toxicity induced by f-CNTs can be measured consistently using this assay, highlighting that isolated Kupffer cells are useful for nanoparticle toxicity testing. The overall understanding of nanotoxicology could benefit from such models, making the nanoparticle selection for clinical translation more efficient.

Organic Solvent-Free, One-Step Engineering of Graphene-Based Magnetic-Responsive Hybrids Using Design of Experiment-Driven Mechanochemistry

In this study, we propose an organic solvent-free, one-step mechanochemistry approach to engineer water-dispersible graphene oxide/superparamagnetic iron oxide (GO/SPIOs) hybrids, for biomedical applications. Although mechanochemistry has been proposed in the graphene field for applications such as drug loading, exfoliation or polymer-composite formation, this is the first study to report mechanochemistry for preparation of GO/SPIOs hybrids. The statistical design of experiment (DoE) was employed to control the process parameters. DoE has been used to control formulation processes of other types of nanomaterials. The implementation of DoE for controlling the formulation processes of graphene-based nanomaterials is, however, novel. DoE approach could be of advantage as one can tailor GO-based hybrids of predicted yields and compositions. Hybrids were characterized by TEM, AFM FT-IR, Raman spectroscopy, and TGA. The dose-response magnetic resonance (MR) properties were confirmed by MR imaging of phantoms. The biocompatibility of the hybrids with A549 and J774 cell lines was confirmed by the modified LDH assay.

Cationic Liposome- Multi-Walled Carbon Nanotubes Hybrids for Dual siPLK1 and Doxorubicin Delivery In Vitro

Purpose

To formulate f-MWNTs-cationic liposome hybrids for the simultaneous delivery of siPLK1 and doxorubicin to cancer cells.

Method

f-MWNTs-cationic liposome hybrids were prepared by the thin film hydration method where the lipid film was hydrated with 100 μg/ml or 1 mg/ml of ox-MWNTs-NH₃⁺ or MWNTs-NH₃⁺ in 5% dextrose. siRNA complexation and protection ability was determined by agarose gel electrophoresis. f-MWNTs and liposome interaction was evaluated using Nile Red (NR) fluorescence spectroscopy. Cellular uptake in A549 cells was assessed by flow cytometry. Silencing of target proteins was determined by Luciferase and MTT assays. Sub-G1 analysis was performed to evaluate apoptosis following co-delivery of siPLK1 and Doxorubicin (Dox).

Results

Zeta potential and siRNA complexation profile obtained for all hybrids were comparable to those achieved with cationic liposomes. ox-MWNTs-NH₃⁺ showed greater extent of interaction with cationic liposomes compared to MWNTs-NH₃⁺. ox-MWNTs-NH₃⁺ was able to protect siRNA from nuclease-mediated degradation. Enhanced cellular uptake of both the carrier and loaded siRNA in A549 cell, were observed for this hybrid compared to the liposomal carrier. A synergistic pro-apoptotic effect was obtained when siPLK1 silencing was combined with doxorubicin treatment for the hybrid:siRNA complexes compared to the lipoplexes, in A549 cells in vitro.

Conclusions

f-MWNTs-cationic liposome hybrid designed in this study can serve as a potential vehicle for the co-delivery of siRNA and cytotoxic drugs to cancer cells in vitro.

Electronic supplementary material

The online version of this article (doi:10.1007/s11095-015-1707-1) contains supplementary material, which is available to authorized users.

Adsorption of lactate dehydrogenase enzyme on carbon nanotubes: how to get accurate results for the cytotoxicity of these nanomaterials

Carbon nanotube (CNT) cytotoxicity is frequently investigated using in vitro classical toxicology assays. However, these cellular tests, usually based on the use of colorimetric or fluorimetric dyes, were designed for chemicals and may not be suitable for nanosized materials. Indeed, because of their unique physicochemical properties CNT can interfere with the assays and bias the results. To get accurate data and draw reliable conclusions, these artifacts should be carefully taken into account. The aim of this study was to evaluate qualitatively and quantitatively the interferences occurring between CNT and the commonly used lactate dehydrogenase (LDH) assay. Experiments under cell-free conditions were performed, and it was clearly demonstrated that artifacts occurred. They were due to the intrinsic absorbance of CNT on one hand and the adsorption of LDH at the CNT surface on the other hand. The adsorption of LDH on CNT was modeled and was found to fit the Langmuir model. The K(ads) and n(eq) constants were defined, allowing the correction of results obtained from cellular experiments to get more accurate data and lead to proper conclusions on the cytotoxicity of CNT.

Comprehensive spectroscopic studies on the interaction of biomolecules with surfactant detached multi-walled carbon nanotubes

This paper investigates the interaction of ten diverse biomolecules with surfactant detached Multi-Walled Carbon Nanotubes (MWCNTs) using multiple spectroscopic methods. Declining fluorescence intensity of biomolecules in combination with the hyperchromic effect in UV-Visible spectra confirmed the existence of the ground state complex formation. Quenching mechanism remains static and non-fluorescent. 3D spectral data of biomolecules suggested the possibilities of disturbances to the aromatic microenvironment of tryptophan and tyrosine residues arising out of CNTs interaction. Amide band Shifts corresponding to the secondary structure of biomolecules were observed in the of FTIR and FT-Raman spectra. In addition, there exists an increased Raman intensity of tryptophan residues of biomolecules upon interaction with CNTs. Hence, the binding of the aromatic structures of CNTs with the aromatic amino acid residues, in a particular, tryptophan was evidenced. Far UV Circular spectra have showed the loss of alpha-helical contents in biomolecules upon interaction with CNTs. Near UV CD spectra confirmed the alterations in the tryptophan positions of the peptide backbone. Hence, our results have demonstrated that the interaction of biomolecules with OH-MWCNTs would involve binding cum structural changes and alteration to their aromatic micro-environment.

Porous and strong three-dimensional carbon nanotube coated ceramic scaffolds for tissue engineering

A method to coat high-quality uniform coatings of carbon nanotubes throughout 3D porous structures is developed. Testing of their physical and biological properties demonstrate their potential for application in tissue engineering.

Investigation of gelatin/multi-walled carbon nanotube nanocomposite films as packaging materials

Gelatin composite films were prepared from gelatin solutions (10% w/v) containing multi-walled carbon nanotubes (MWCNT, 0.5, 1, 1.5, and 2% w/w gelatin) as nanofiller. The water solubility, water swelling, water uptake, water vapor permeability (WVP), mechanical, and antibacterial properties of the films were examined. Water solubility, water swelling, water uptake, and WVP for gelatin films were 45 ± 1%, 821 ± 42%, 45 ± 1.1%, and 0.4 ± 0.022 g mm/m² kPa h, respectively. Incorporation of MWCNT caused a significant decrease in water solubility, water swelling, water uptake, and WVP. Gelatin/MWCNT films containing 1–1.5% MWCNT showed the lowest water vapor transmission. Tensile strength, elongation at break, and Young's modulus for gelatin films were 13.4 ± 1.2 MPa, 95 ± 5%, and 45.4 ± 7 MPa, respectively. Incorporation of MWCNT caused a significant increase in tensile strength and decrease in the elongation at break. The largest mechanical strength was found at 1.5% MWCNT. All gelatin/MWCNT films showed significant antibacterial activities against both gram-positive and gram-negative bacteria. Our results suggest that the gelatin/MWCNT composites films could be used as a very attractive alternative to traditional materials for different biomedical and food applications.

Carbon nanotubes in neuroregeneration and repair

In the last decade, we have experienced an increasing interest and an improved understanding of the application of nanotechnology to the nervous system. The aim of such studies is that of developing future strategies for tissue repair to promote functional recovery after brain damage. In this framework, carbon nanotube based technologies are emerging as particularly innovative tools due to the outstanding physical properties of these nanomaterials together with their recently documented ability to interface neuronal circuits, synapses and membranes. This review will discuss the state of the art in carbon nanotube technology applied to the development of devices able to drive nerve tissue repair; we will highlight the most exciting findings addressing the impact of carbon nanotubes in nerve tissue engineering, focusing in particular on neuronal differentiation, growth and network reconstruction.

Carbon nanotubes: their potential and pitfalls for bone tissue regeneration and engineering

The extracellular environment which supports cell life is composed of a hierarchy of maintenance, force and regulatory systems which integrate from the nano- through to macroscale. For this reason, strategies to recreate cell supporting environments have been investigating the use of nanocomposite biomaterials. Here, we review the use of carbon nanotubes as part of a bottom-up approach for use in bone tissue engineering. We evaluate the properties of carbon nanotubes in the context of synthetic tissue substrates and contrast them with the nanoscale features of the extracellular environment. Key studies are evaluated with an emphasis on understanding the mechanisms through which carbon nanotubes interact with biological systems. This includes an examination of how the different properties of carbon nanotubes affect tissue growth, how these properties and variation to them might be leveraged in regenerative tissue therapies and how impurities or contaminates affect their toxicity and biological interaction.

FROM THE CLINICAL EDITOR

In this comprehensive review, the authors describe the status and potential applications of carbon nanotubes in bone tissue engineering.

Purified graphene oxide dispersions lack in vitro cytotoxicity and in vivo pathogenicity

Prompted by the excitement from the description of single layer graphene, increased attention for potential applications in the biomedical field has been recently placed on graphene oxide (GO). Determination of the opportunities and limitations that GO offers in biomedicine are particularly prone to inaccuracies due to wide variability in the preparation methodologies of GO material in different laboratories, that results in significant variation in the purity of the material and the yield of the oxidation reactions, primarily the Hummers method used. Herein, the fabrication of highly pure, colloidally stable, and evenly dispersed GO in physiologically-relevant aqueous buffers in comparison to conventional GO is investigated. The purified GO material is thoroughly characterized by a battery of techniques, and is shown to consist of single layer GO sheets of lateral dimensions below 500 nm. The cytotoxic impact of the GO in vitro and its inflammation profile in vivo is investigated. The purified GO prepared and characterized here does not induce significant cytotoxic responses in vitro, or inflammation and granuloma formation in vivo following intraperitoneal injection. This is one of the initial steps towards determination of the safety risks associated with GO material that may be interacting with living tissue.

Biofunctionalized carbon nanotubes in neural regeneration: a mini-review

Carbon nanotubes (CNTs) have become an intriguing and promising biomaterial platform for the regeneration and functional recovery of damaged nerve tissues. The unique electrical, structural and mechanical properties, diversity of available surface chemistry and cell-penetrating ability of CNTs have made them useful implantable matrices or carriers for the delivery of therapeutic molecules. Although there are still challenges being faced in the clinical applications of CNTs mainly due to their toxicity, many studies to overcome this issue have been published. Modification of CNTs with chemical groups to ensure their dissolution in aqueous media is one possible solution. Functionalization of CNTs with biologically relevant and effective molecules (biofunctionalization) is also a promising strategy to provide better biocompatibility and selectivity for neural regeneration. Here, we review recent advances in the use of CNTs to promote neural regeneration.

Functionalized carbon nanotubes: biomedical applications

Carbon nanotubes (CNTs) are emerging as novel nanomaterials for various biomedical applications. CNTs can be used to deliver a variety of therapeutic agents, including biomolecules, to the target disease sites. In addition, their unparalleled optical and electrical properties make them excellent candidates for bioimaging and other biomedical applications. However, the high cytotoxicity of CNTs limits their use in humans and many biological systems. The biocompatibility and low cytotoxicity of CNTs are attributed to size, dose, duration, testing systems, and surface functionalization. The functionalization of CNTs improves their solubility and biocompatibility and alters their cellular interaction pathways, resulting in much-reduced cytotoxic effects. Functionalized CNTs are promising novel materials for a variety of biomedical applications. These potential applications are particularly enhanced by their ability to penetrate biological membranes with relatively low cytotoxicity. This review is directed towards the overview of CNTs and their functionalization for biomedical applications with minimal cytotoxicity.

Carbon nanotube-mediated wireless cell permeabilization: drug and gene uptake

Aim: This work aims to exploit the ‘antenna’ properties of multiwalled carbon nanotubes (MWCNTs). They can be used to induce cell permeabilization in order to transfer drugs (normally impermeable to cell membranes) both in in vitro and in vivo models. Material & Methods: The performance of the MWCNTs as receiver antenna was modeled by finite element modeling. Once the appropriate field has been identified, the antenna properties of MWCNTs were investigated in sequential experiments involving immortalized fibroblast cell line (drug model: doxorubicin chemothererapeutic agent) and living mice (drug model: bcl-2 antiapoptotic gene) following stereotactic injection in the cerebral motor cortex. Results: Finite element modeling analysis predicts that our MWCNTs irradiated in the radiofrequency field resemble thin-wire dipole antennas. In vitro experiments confirmed that combination of MWCNTs and electromagnetic field treatment dramatically favors intracellular drug uptake and, most importantly, drug nuclear localization. Finally, the brain of each irradiated animal exhibits a significantly higher number of transfected cells compared with the appropriate controls. Conclusion: This wireless application has the potential for MWCNT-based intracellular drug delivery and electro-stimulation therapies.

Binding of blood proteins to carbon nanotubes reduces cytotoxicity

With the potential wide uses of nanoparticles such as carbon nanotubes in biomedical applications, and the growing concerns of nanotoxicity of these engineered nanoparticles, the importance of nanoparticle-protein interactions cannot be stressed enough. In this study, we use both experimental and theoretical approaches, including atomic force microscope images, fluorescence spectroscopy, CD, SDS-PAGE, and molecular dynamics simulations, to investigate the interactions of single-wall carbon nanotubes (SWCNTs) with human serum proteins, and find a competitive binding of these proteins with different adsorption capacity and packing modes. The π-π stacking interactions between SWCNTs and aromatic residues (Trp, Phe, Tyr) are found to play a critical role in determining their adsorption capacity. Additional cellular cytotoxicity assays, with human acute monocytic leukemia cell line and human umbilical vein endothelial cells, reveal that the competitive bindings of blood proteins on the SWCNT surface can greatly alter their cellular interaction pathways and result in much reduced cytotoxicity for these protein-coated SWCNTs, according to their respective adsorption capacity. These findings have shed light toward the design of safe carbon nanotube nanomaterials by comprehensive preconsideration of their interactions with human serum proteins.