Antimicrobial and osteogenic properties of a hydrophilic-modified nanoscale hydroxyapatite coating on titanium

Hydroxyapatite (HA)-coated titanium (Ti) is commonly used for implantable medical devices. This study examined in vitro osteoblast gene expression and antimicrobial activity against early and late colonizers of supra-gingival plaque on nanoscale HA-coated Ti prepared by discharge in a physiological buffered solution. The HA-coated Ti surface showed super-hydrophilicity, whereas the densely sintered HA and Ti surfaces alone showed lower hydrophilicity. The sintered HA and HA-coated Ti surfaces enhanced osteoblast phenotypes in comparison with the bare Ti surface. The HA-coated Ti enabled antimicrobial activity against early colonizers of supra-gingival plaques, namely Streptococcus mitis and Streptococcus gordonii. Such antimicrobial activity may be caused by the surface hydrophilicity, thereby leading to a repulsion force between the HA-coated Ti surface and the bacterial cell membranes. On the contrary, the sintered HA sample was susceptible to infection of microorganisms. Thus, hydrophilic-modified HA-coated Ti may have potential for use in implantable medical devices. From the Clinical Editor: This study establishes that Hydroxyapatite (HA)-coated titanium (Ti) surface of implanted devices may result in an optimal microenvironment to control and prevent infections and may have potential future clinical applications.     

钛种植体表面原位包裹大鼠骨髓基质细胞的研究

目的探讨钛种植体表面对大鼠骨髓基质细胞（bone marrow stromal cells,BMSCs）进行原位包裹的方法,为钛种植体表面组织工程支架构建提供实验基础。方法采用层层自组装技术在钛种植体表面构建以壳聚糖/海藻酸钠为组分的聚电解质多层膜结构,同时对BMSCs进行原位分层包裹,并通过扫描电镜及激光共聚焦显微镜观察包裹细胞的生长状态。结果扫描电镜及激光共聚焦显微镜观察证实BMSCs被成功包裹于钛种植体表面,并保持良好的生物学活性。结论钛种植体表面可以实现对BMSCs的原位分层包裹。     

Surface modification by argon plasma treatment improves antioxidant defense ability of CHO-k1 cells on titanium surfaces

Titanium is one of the most used materials in implants and changes in its surface can modify the cellular functional response to better implant fixation. An argon plasma treatment generates a surface with improved mechanical proprieties without modifying its chemical composition. Oxidative stress induced by biomaterials is considered one of the major causes of implant failure and studies in this field are fundamental to evaluate the biocompatibility of a new material. Therefore, in this work, induction of oxidative stress by titanium surfaces subjected to plasma treatment (PTTS) was evaluated. The viability of CHO-k1 cells was higher on PTTS discs. Cells grown on titanium surfaces are subjected to intracellular oxidative stress. Titanium discs subjected to the plasma treatment induced less oxidative stress than the untreated ones, which resulted in improved cellular survival. These were associated with improved cellular antioxidant response in Plasma Treated Titanium Surface (PTTS). Furthermore, a decrease in protein and DNA oxidative damage was observed on cells grown on the roughed surface when compared to the smooth one. In conclusion, our data suggest that the treatment of titanium with argon plasma may improve its biocompatible, thus improving its performance as implants or as a scaffold in tissue engineering.     

Ti-6Al-7Nb 喷砂酸蚀处理后对大鼠成骨细胞的影响

摘要 目的 纯钛（Ti）和Ti-6Al-7Nb(TC20)经机械打磨和喷砂酸蚀(SLA)两种不同方法处理后,研究其内部结构、表面能对小鼠成骨细胞的影响。方法 选取纯钛和Ti-6Al-7Nb钛片若干分为实验组和对照组,对照组直接用砂纸机械打磨,实验组用含有Al203的大颗粒石英砂和配比好的酸蚀液喷砂酸蚀两种钛片表面,将从小鼠中提取的成骨细胞接种于钛片上,使用低倍数显微镜观察经过不同处理的两种钛片表面形貌,接触角测量仪分析钛片表面亲水性,将喷砂酸蚀处理的两种钛片放入模拟体液(SBF)中7d、14d、21d后用扫描电镜(SEM)、X线衍射仪(XRD)观察样品表面沉积物形貌、物相,扫描电镜观察小鼠成骨细胞形貌,MTT测量小鼠成骨细胞增殖情况。结果 纯钛和Ti-6Al-7Nb打磨组表面呈机械划痕,喷砂酸蚀组表面拥有大量孔洞形貌,喷砂酸蚀处理后的钛片表面为亲水性结构,样品浸入模拟体液14天后Ti-6Al-7Nb表面最先观察到表面覆盖的羟基磷灰石涂层, 样品浸入模拟体液后21d,Ti和Ti-6Al-7Nb表面都观察到羟基磷灰石涂层,小鼠成骨细胞大量附着在喷砂酸蚀处理的钛片表面,经统计学分析成骨细胞在喷砂酸蚀组表面增殖能力强于光滑组（P<0.05）。结论 喷砂酸蚀处理的Ti-6Al-7Nb有利于成骨细胞的黏附, 羟基磷灰石涂层有利于促进种植体与骨组织的结合。     

The in vitro absorption of microfine zinc oxide and titanium dioxide through porcine skin.

Microfine metallic oxides such as titanium dioxide or zinc oxide have been found to be highly protective against harmful UV rays. Because their long-term use could potentially lead to health effects if significant amounts of these microfine metallic oxides would be absorbed through the skin, the in vitro absorption of microfine zinc oxide and titanium oxide in cosmetic formulations through porcine skin was investigated. In the experiments with a microfine zinc oxide formulation, the mean total recoveries of Zn were in the range from 102% to 107% of the total Zn applied. Virtually the total amount of applied Zn was recovered in the first five tape strips. The amounts of Zn found in the skin membrane and the receptor fluid were comparable in untreated, vehicle treated or test substance treated skin preparations. The absorption-time plots from diffusion cells treated with the vehicle did not differ from those treated with the ZnO containing formulation. In the experiments with microfine titanium dioxide formulations T-Lite SF-S and T-Lite SF, mean total recoveries of Ti ranged from 98% to 100% and 86% to 93% of the total Ti applied, respectively. Virtually the total amount of applied Ti could be removed from the skin surface by washing. The amounts of titanium found in the tape strips and skin preparations were in the order of the analytical determination limit. No Ti was found in the receptor fluid at any sampling time. The results show that neither zinc or titanium ions nor microfine zinc oxide or titanium dioxide particles were able to penetrate porcine stratum corneum. Therefore, from the absence of internal exposure we conclude that their use in sunscreens does not pose a health risk.     

A study of the effect of chrysotile fiber surface composition on genotoxicity in vitro.

Chrysotile fibers (NIEHS intermediate length) were treated with ultrapure HCl to alter the fiber surface chemistry without substantially changing fiber morphology or dimensions. The objective of the study was to determine whether fiber surface chemistry is an important variable in fiber genotoxicity in vitro. The modified fibers, along with native chrysotile fibers, were used to challenge Chinese hamster lung fibroblasts (V79) in vitro using the micronucleus induction genotoxicity assay. Fiber dimensions were assessed using scanning electron microscopy by measuring the distribution of fiber lengths in 3 length ranges: less than 3 microm, 3-10 microm, and greater than 10 microm. For both treated and native fiber samples, 500 fibers were examined. Results indicate that acid-treated fibers were about 20% shorter than untreated chrysotile. Surface chemistry alterations were verified by zeta-potential reversal, x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy/energy-dispersive x-ray spectroscopy (SEM-EDS) elemental analysis. Scanning Auger spectrometry indicated the presence of Mg, O, and Si in both treated and native chrysotile samples, which confirmed the surface purity of both fiber samples. Both XPS and SEM-EDS analysis demonstrated substantial depletion of Mg from fiber surfaces. Results of the micronucleus assay showed a positive concentration-related response for both samples, with toxicity evident only at the highest concentration. No significant difference was found for the treated and untreated chrysotile samples. These results indicate that the surface chemistry is not an important variable in the in vitro genotoxicity of chrysotile asbestos in V79 cells as detected by the micronucleus assay under the conditions used in this study, and support a model of chemically nonspecific chromosomal and spindle damage effects.     

钛及钛合金种植体的两种表面处理对细菌黏附能力的影响

目的研究两种表面处理(等离子渗氮和物理气相沉积TiN涂层)对钛、钛合金表面的组织结构、性能及对变形链球菌黏附的影响。方法将相同规格的钛、钛合金片经逐级抛光后分别随机分成3组,每组3片,依次为抛光组,渗氮表面处理组,TiN涂层表面处理组。以抛光钛、钛合金组作为对照。测量所有试件表面的粗糙度值,并采用扫描电镜、Axiovert 25CA光学图像分析仪及GDA750对钛、钛合金表面渗镀层的表面形态进行分析;将材料接种于变形链球菌悬液,在荧光显微镜下计数黏附细菌的数量。结果两种表面处理仅使原有表面粗糙度略微增加;扫描电镜显示两种表面处理后材料表面的原始划痕消失;GDS检测分析结果表明:钛、钛合金两种表面处理后,表面主要由氮化钛化合物组成。经两种处理后,钛、钛合金黏附细菌的量显著减少,而两种表面处理差异无统计学意义。结论钛、钛合金经两种表面处理后形成了稳定的改性层,且能减少细菌的黏附。相对于有涂层脱落之忧的物理气相沉积TiN涂层技术,等离子渗氮技术有望作为种植体穿龈部和种植体基台部的表面处理技术。     

The Effects of Food Protector Biphenyl on Sister Chromatid Exchange,Chromosome Aberrations,and Micronucleus in Human Lymphocytes

The aim of this study was to determine the possible genotoxic effects of biphenyl (E230), which is used as an antimicrobial agent in food by using sister chromatid exchanges (SCEs), chromosome aberrations (CAs), and micronucleus (MN) tests in human peripheral lymphocytes. The human peripheral lymphocytes were treated with four concentrations of biphenyl (10, 30, 50, and 70 μg/mL) for 24- and 48-h treatment periods. In the present study, biphenyl significantly increased the frequency of SCEs, CAs, and the frequency of MN when compared with both untreated control and solvent (dimethyl sulfoxide) control. The inductions of these abnormalities were in a dose-dependent manner. Biphenyl was capable to induce the structural CAs instead of numerical CAs. Biphenyl also showed a cytotoxic effect by decreasing the replication index at the highest two concentrations for 48 h and nuclear division index at the highest two concentrations for the 24- and 48-h treatment periods. However, biphenyl did not affect the mitotic index (MI).     

The effects of food protector biphenyl on sister chromatid exchange, chromosome aberrations, and micronucleus in human lymphocytes

The aim of this study was to determine the possible genotoxic effects of biphenyl (E230), which is used as an antimicrobial agent in food by using sister chromatid exchanges (SCEs), chromosome aberrations (CAs), and micronucleus (MN) tests in human peripheral lymphocytes. The human peripheral lymphocytes were treated with four concentrations of biphenyl (10, 30, 50, and 70 microg/mL) for 24- and 48-h treatment periods. In the present study, biphenyl significantly increased the frequency of SCEs, CAs, and the frequency of MN when compared with both untreated control and solvent (dimethyl sulfoxide) control. The inductions of these abnormalities were in a dose-dependent manner. Biphenyl was capable to induce the structural CAs instead of numerical CAs. Biphenyl also showed a cytotoxic effect by decreasing the replication index at the highest two concentrations for 48 h and nuclear division index at the highest two concentrations for the 24- and 48-h treatment periods. However, biphenyl did not affect the mitotic index (MI).     

Induction of chromosomal aberrations by carbon nanotubes and titanium dioxide nanoparticles in human lymphocytes in vitro

Abstract

We examined if three commercially available nanomaterials – short singlewall carbon nanotubes (SWCNTs), short multiwall carbon nanotubes (MWCNTs) and nanosized titanium dioxide anatase (TiO₂; primary particle size <25 nm) – can induce structural chromosomal aberrations (CAs) in cultures of isolated human lymphocytes. To find a suitable sampling time, the cells were treated with 6.25–300 μg/ml of the nanomaterials for 24, 48 and 72 h. The 48-h treatment was the most effective, inducing a dose-dependent increase in chromosome-type CAs (all materials) and chromatid-type CAs (SWCNTs and TiO₂ anatase). The 72-h treatment yielded a positive result with SWCNTs. None of the treatments significantly affected cell count or the mitotic index. Our results suggest that with nanomaterials a continuous treatment for about two cell cycles is needed for CA induction, possibly reflecting access of nanomaterials to the nucleus during the first mitosis or delayed secondary genotoxic effect associated with the inflammatory process.     

新一代人工心脏瓣膜材料血液相容性的实验研究

目的：探讨表面改性后的人工心脏瓣膜材料的血液相容性。方法：氧化钛（Ti-O)试样薄膜与目前的心脏瓣膜材料热解碳（LTIC）薄膜成对置入动物犬体内。1．腹主动脉内埋置60天。2．右心房内埋置17天,60天,100天。3．改性后Ti-O瓣膜支架与未改性瓣膜支架成对置入右心房内17天,60天,100天。结果：电镜扫描观察17天,60天Ti-O的薄膜及支架表面无血细胞粘附,100天Ti-O的薄膜支架仅有个别形态完整的血细胞,LTIC薄膜及未改性的瓣膜支架17天即可见到血球沉着,100天时血细胞和纤维状物大量粘附,支架被沉着物密布,血细胞变形有伪足,电 见血小板内有空泡,脱颗粒,微管扩张。结论：Ti-O有极好的血液相容性,有希望成为 新一代人工心脏瓣膜材料。     

An atomic force microscopy investigation of bioadhesive polymer adsorption onto human buccal cells

Atomic force microscopy (AFM) was used to examine the buccal cell surface in order to image the presence of adsorbed bioadhesive polymers identified from previous work. Isotonic saline solution (5 ml) containing either polycarbophil (pH 7.6), chitosan (pH 4.5) or hydroxypropyl methylcellulose (pH 7.6) (0.5% w/v) was exposed to freshly collected buccal cells (ca. 48×10⁴ cells/test) for 15 min at 30°C. The cells were then rinsed with a small volume of double distilled water, allowed to air-dry on a freshy cleaved mica surface and imaged using contact mode AFM. Untreated cells showed relatively smooth surface characteristics, with many small ‘crater-like’ pits and indentations spread over cell surfaces. Cells that had been treated with all the investigated polymers appeared to have lost the crater and indentation characteristic and gained a higher surface roughness. These results suggest that polymer chains had adsorbed onto the cell surfaces. Quantitative image analysis of cell topography showed significant increases (P<0.05) in arithmetic roughness average (R_a) for all the investigated polymer treated cells surfaces with respect to untreated control specimens. The changes in surface topography indicate the presence of adsorbed polymer, confirming previous work. This study demonstrates the suitability of AFM as a powerful and sensitive technique for detecting and imaging bioadhesive polymers present on mucosal cell surfaces.     

A STUDY OF THE EFFECT OF CHRYSOTILE FIBER SURFACE COMPOSITION ON GENOTOXICITY IN VITRO

Chrysotile fibers (NIEHS intermediate length) were treated with ultrapure HCl to alter the fiber surface chemistry without substantially changing fiber morphology or dimensions. The objective of the study was to determine whether fiber surface chemistry is an important variable in fiber genotoxicity in vitro. The modified fibers, along with native chrysotile fibers, were used to challenge Chinese hamster lung fibroblasts (V79) in vitro using the micronucleus induction genotoxicity assay. Fiber dimensions were assessed using scanning electron microscopy by measuring the distribution of fiber lengths in 3 length ranges: less than 3 mum, 3-10 mum, and greater than 10 mum. For both treated and native fiber samples, 500 fibers were examined. Results indicate that acid-treated fibers were about 20% shorter than untreated chrysotile. Surface chemistry alterations were verified by zeta-potential reversal, x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy/energy-dispersive x-ray spectroscopy (SEM-EDS) elemental analysis. Scanning Auger spectrometry indicated the presence of Mg, O, and Si in both treated and native chrysotile samples, which confirmed the surface purity of both fiber samples. Both XPS and SEM-EDS analysis demonstrated substantial depletion of Mg from fiber surfaces. Results of the micronucleus assay showed a positive concentration-related response for both samples, with toxicity evident only at the highest concentration. No significant difference was found for the treated and untreated chrysotile samples. These results indicate that the surface chemistry is not an important variable in the in vitro genotoxicity of chrysotile asbestos in V79 cells as detected by the micronucleus assay under the conditions used in this study, and support a model of chemically nonspecific chromosomal and spindle damage effects.     

Antibacterial activity and biofilm inhibition by surface modified titanium alloy medical implants following application of silver,titanium dioxide and hydroxyapatite nanocoatings

One of the most common causes of implant failure is peri-implantitis, which is caused by bacterial biofilm formation on the surfaces of dental implants. Modification of the surface nanotopography has been suggested to affect bacterial adherence to implants. Silver nanoparticles are also known for their antibacterial properties. In this study, titanium alloy implants were surface modified following silver plating, anodisation and sintering techniques to create a combination of silver, titanium dioxide and hydroxyapatite (HA) nanocoatings. Their antibacterial performance was quantitatively assessed by measuring the growth of Streptococcus sanguinis, proportion of live/dead cells and lactate production by the microbes over 24?h. Application of a dual layered silver–HA nanocoating to the surface of implants successfully inhibited bacterial growth in the surrounding media (100% mortality), whereas the formation of bacterial biofilm on the implant surfaces was reduced by 97.5%. Uncoated controls and titanium dioxide nanocoatings showed no antibacterial effect. Both silver and HA nanocoatings were found to be very stable in biological fluids with material loss, as a result of dissolution, to be less than 0.07% for the silver nanocoatings after 24?h in a modified Krebs-Ringer bicarbonate buffer. No dissolution was detected for the HA nanocoatings. Thus, application of a dual layered silver–HA nanocoating to titanium alloy implants creates a surface with antibiofilm properties without compromising the HA biocompatibility required for successful osseointegration and accelerated bone healing.     

In vivo cytogenetic studies on rat's bone-marrow cells of structurally related Schiff base complexes

The in vivo interactions of structurally-related Ni(II) and Fe(III) Schiff base complexes based on N-(8-quinolyl)salicylaldimine (HL(1)) and N-(8-quinolyl)napthaldimine (HL(2)) ligands with DNA molecules in the bone-marrow cells of rats were demonstrated using chromosomal aberrations (CAs) assay. The complexes differ by one aromatic group on the aldehyde site of the Schiff base (basicity or lipophilicity), or by the type of the central metal ions (Ni(II) or Fe(III)). Animals were injected intraperitoneally (i.p) with different concentrations of each drug, and CAs were examined in bone-marrow cells, 15 hours later. A significant increase in the frequency of CAs was induced upon treatment with 15?mg / kg weight of L(1) complexes (P < 0.001), and not with L(2) complexes (P > 0.05). Also, the magnitude of aberrations induced by L(1)-Ni(II) was higher than that induced by L(1)-Fe(III) (P < 0.01). The binding data, estimated using UV-Visible absorption technique, showed that the metal binding of HL(1) was much greater than that of HL(2) and that the affinity of HL(1) towards Ni(II) is higher than that for Fe(III) ions. Thus, the trends in the presented in vivo results signify the important role of complex stability in predicting the clastogenicity of metal-ion-chelating Schiff base drugs.     

Evaluation of Osseointegration around Tibial Implants in Rats by Ibandronate-Treated Nanotubular Ti-32Nb-5Zr Alloy

Materials with differing surfaces have been developed for clinical implant therapy in dentistry and orthopedics. This study was designed to evaluate bone response to titanium alloy containing Ti-32Nb-5Zr with nanostructure, anodic oxidation, heat treatment, and ibandronate coating. Rats were randomly assigned to two groups for implantation of titanium alloy (untreated) as the control group and titanium alloy group coated with ibandronate as the experimental group. Then, the implants were inserted in both tibiae of the rats for four weeks. After implantation, bone implant interface, trabecular microstructure, mechanical fixation was evaluated by histology, micro-computed tomography (μCT) and the push-out test, respectively. We found that the anodized, heat-treated and ibandronate-coated titanium alloy triggered pronounced bone implant integration and early bone formation. Ibandronate-coated implants showed elevated values for removal torque and a higher level of BV/TV, trabecular thickness and separation upon analysis with μCT and mechanical testing. Similarly, higher bone contact and a larger percentage bone area were observed via histology compared to untreated alloy. Furthermore, well coating of ibandronate with alloy was observed by vitro releasing experiment. Our study provided evidences that the coating of bisphosphonate onto the anodized and heat-treated nanostructure of titanium alloy had a positive effect on implant fixation.     

Characterization of a surface modified dry powder inhalation carrier prepared by "particle smoothing"

Atomic force microscopy (AFM) was used to investigate drug-carrier interactions between beclometasone dipropionate (BDP) and a series of untreated and modified lactose surfaces. This quantitative information was correlated with bulk characterization methods and an in-vitro study. Modified lactose surfaces were prepared using a proprietary process referred to as "particle smoothing" to obtain smooth carrier surfaces with or without the presence of magnesium stearate. The engineering of lactose carrier surfaces using the particle smoothing process resulted in significant differences in surface morphology when compared with the "as supplied" starting material. The energy of separation, between BDP and lactose samples, determined by AFM suggested similar lognormal distributions with a rank decrease in median separation energy (e(0.5)) (26.7, 20.6 and 7.7 microJ for untreated, particle-smoothed and particle-smoothed with magnesium stearate, respectively). A series of in-vitro twin stage impinger studies showed good correlation with the AFM separation energy measurements. The mean fine particle dose increased for the two processed lactose samples, with a significant increase for the lactose processed with magnesium stearate, 102.0+/-16 microg compared with 24.2+/-10.7 microg for the untreated lactose. Thus, the AFM presents as a possible pre-formulation tool for rapid characterization of particle interactions.     

The bone-implant interface – nanoscale analysis of clinically retrieved dental implants

Evaluation of the fine structure of the bone-implant interface in humans is a prerequisite for a deepened understanding of structure–function relationships with nano-modified biomaterials. In this study, three clinically stable, yet retrieved, laser-modified dental implants were evaluated using histological and interface ultrastructural analyses. The cumulative results for all threads containing intact tissue showed remodeled Haversian bone with bone area and bone-implant contact in excess of 85% and 80%, respectively. Collagen fibrils, laid down parallel to the surface oxide layer, were mineralized by plate-like crystallites of stoichiometrically relevant (Ca/P ratios 1.30-1.67) bone-apatite. An overlap of titanium, oxygen, calcium and phosphorus signals indicated the gradual intermixing of bone-apatite and the nano-rough surface oxide. These results suggest that bone bonding to nano-textured titanium implant surfaces is promoted in human jaw-bone after functional loading.From the Clinical EditorIn this study, newly developed and laser-modified titanium dental implants demonstrate strong evidence for implant-osseo integration basen on the surface and chemical analysis of three clinically stable dental implants.     

Cytogenetic damage induced by acrylamide and glycidamide in mammalian cells: correlation with specific glycidamide-DNA adducts.

Acrylamide (AA) is a suspected human carcinogen generated in carbohydrate-rich foodstuffs upon heating. Glycidamide (GA), formed via epoxidation, presumably mediated by cytochrome P450 2E1, is thought to be the active metabolite playing a central role in AA genotoxicity. In this work we investigated DNA damage induced by AA and GA in mammalian cells, using V79 Chinese hamster cells. For this purpose, we evaluated two cytogenetic end points, chromosomal aberrations (CAs) and sister chromatid exchanges (SCEs), as well as the levels of specific GA-DNA adducts, namely, N7-(2-carbamoyl-2-hydroxyethyl)guanine (N7-GA-Gua) and N3-(2-carbamoyl-2-hydroxyethyl)adenine (N3-GA-Ade) using high-performance liquid chromatography coupled with tandem mass spectrometry. GA was more cytotoxic and clastogenic than AA. Both AA and GA induced CAs (breaks and gaps) and decreased the mitotic index. GA induced SCEs in a dose-responsive manner; with AA, SCEs were increased at only the highest dose tested (2mM). A linear dose-response relationship was observed between the GA concentration and the levels of N7-GA-Gua. This adduct was detected for concentrations as low as 1 microM GA. N3-GA-Ade was also detected, but only at very high GA concentrations (>or= 250 microM). There was a very strong correlation between the levels of N7-GA-Gua in the GA- and AA-treated cells and the extent of SCE induction. Such correlation was not apparent for CAs. These data suggest that the induction of SCEs by AA is associated with the metabolism of AA to GA and subsequent formation of depurinating DNA adducts; however, other mechanisms must be involved in the induction of CAs.     

Evaluation of DNA damage induced by norcantharidin in human cultured lymphocytes

Norcantharidin (NCTD) is currently used in the treatment of several cancers such as leukemia, melanoma and hepatoma. The mechanism of action of NCTD is suggested to involve induction of apoptosis of cancer cells via production of reactive oxygen species. In this study, the genotoxic effect of different concentrations of NCTD (1, 10 and 20?μm) in human lymphocytes was investigated using sister chromatid exchanges (SCEs) and chromosomal aberrations (CAs) assays. The results revealed that NCTD significantly increased the rate of SCEs (p?<?0.05) in a dose-dependent manner. In addition, NCTD significantly increased the number of high-frequency cells (SCEs?≥?8, p?<?0.05). However, NCTD did not have any significant effect on the rate of CAs (p?>?0.05). In addition, no significant differences were detected in the mitotic index or proliferative index at examined doses (up to 20?μm). In conclusion, NCTD is genotoxic to human cultured lymphocytes as measured by SCE assay.