Multilayered stable 2D nano-sheets of Ti2NTx MXene: synthesis, characterization, and anticancer activity.

BACKGROUND: The biological activity of MXenes has been studied for several years because of their potential biomedical applications; however, investigations have so far been limited to 2D titanium carbides. Although monolayered Ti2NTx MXene has been expected to have biological activity, experimental studies revealed significant difficulties due to obstacles to its synthesis, its low stability and its susceptibility to oxidation and decomposition. RESULTS: In this paper, we report our theoretical calculations showing the higher likelihood of forming multilayered Ti2NTx structures during the preparation process in comparison to single-layered structures. As a result of our experimental work, we successfully synthesized multilayered Ti2NTx MXene that was suitable for biological studies by the etching of the Ti2AlN MAX phase and further delamination. The biocompatibility of Ti2NTx MXene was evaluated in vitro towards human skin malignant melanoma cells, human immortalized keratinocytes, human breast cancer cells, and normal human mammary epithelial cells. Additionally, the potential mode of action of 2D Ti2NTx was investigated using reactive oxygen tests as well as SEM observations. Our results indicated that multilayered 2D sheets of Ti2NTx showed higher toxicity towards cancerous cell lines in comparison to normal ones. The decrease in cell viabilities was dose-dependent. The generation of reactive oxygen species as well as the internalization of the 2D sheets play a decisive role in the mechanisms of toxicity. CONCLUSIONS: We have shown that 2D Ti2NTx in the form of multilayered nanoflakes exhibits fair stability and can be used for in vitro studies. These results show promise for its future applications in biotechnology and nanomedicine.

Quantification of the APE2 gene expression level in Candida albicans clinical isolates from patients with diagnosed fungal infections.

The production of hydrolytic enzymes is considered a key virulence determinant of Candida albicans. Aminopeptidase 2 (Ape2) facilitates the penetration of C. albicans into the host tissue, by providing free amino acids to support fungal growth and proliferation. The objective of this study was to estimate the APE2 expression profile in C. albicans cells during invasion of the human epithelium. Sixty-one clinical fungal isolates and five reference strains were included in this study. The wild-type APE2 sequence was analyzed by polymerase chain reaction (PCR) amplification using genomic DNA from pathogenic isolates. Amplicons were verified in 1% agarose gel and visualized by illumination with ultraviolet (UV) light. The APE2 expression levels were analyzed with reverse transcription quantitative real-time PCR (RT-qPCR) and APE2 quantification was normalized against the reference gene in C. albicans cells grown in YEPD and during Caco-2 invasion. The APE2-specific PCR product band was found in all C. albicans and C. dubliniensis strains, but not in other common pathogenic fungi. APE2 transcript abundance was elevated in the clinical isolates growing on the Caco-2 cell line in comparison to their counterparts grown in YEPD. Our data indicate a potential role for Ape2 in the invasion of epithelial cells. APE2 expression is also strain-specific, and it is not related to isolation site or disease entity.

On the rapid in situ oxidation of two-dimensional V2CTz MXene in culture cell media and their cytotoxicity.

The plethora of emerging two-dimensional (2D) materials exhibit wide potential application in novel technologies and advanced devices. However, their stability in environmental conditions could be an issue, affecting their application possibilities and posing health risks. Moreover, their decomposed leftovers can also induce a negative influence on human health. In particular, transition metal carbides commonly referred to as MXenes are susceptible to environmental oxidation being decomposed toward transition metal oxides and carbide-derived carbon. In this study we focused on the oxidation-state-related in vitro cytotoxicity of delaminated V2CTz onto immortalized keratinocytes (HaCaT) and malignant melanoma (A375) human cell lines. Due to the fact, that the V2CTx MXenes are least stable from all known obtained MXenes up to date, the vanadium ones were a practical choice to visualize the oxidation-cytotoxic correlation keeping the standards of 24-48 h of cell culturing. We found that the oxidation of V2CTz highly increases their cytotoxicity toward human cells, which is also time and dose dependent. The identified mode of action relates to the cell cycle as well as cellular membrane disintegration through direct physicochemical interactions.

Collaborative study to establish a replacement World Health Organization International Standard for parvovirus B19 DNA nucleic acid amplification technology (NAT)-based assays.

BACKGROUND AND OBJECTIVES: The aim of the study was to replace the 1(st) World Health Organization International Standard for parvovirus B19 DNA for nucleic acid amplification technique (NAT)-based assays (code 99/800). Two lyophilized preparations (coded 99/800 and 99/802) had been evaluated in the original collaborative study. The present study re-evaluates these two preparations in terms of potency, stability and encapsidation of virus DNA. MATERIALS AND METHODS: The 1(st) International Standard (99/800) and 99/802 were re-coded as Samples 1 and 2, respectively. The samples were distributed to six laboratories and assayed on four separate occasions. Accelerated thermal degradation samples of the two preparations were examined after storage at 20 degrees C for 7 years. Nuclease treatment was used to investigate the encapsidation of virus DNA. RESULTS: Data were returned from a total of six different quantitative NAT-based assays. The results of the present study confirm those of the original, with no significant differences found in estimated international units (IU)/ml for the 1(st) International Standard (Sample 1 in this study) and the proposed replacement preparation, Sample 2 (99/802). Accelerated thermal degradation studies demonstrate that both samples are very stable, with no loss of potency after storage at 20 degrees C for 7 years. Both lyophilized preparations contained the majority of B19V DNA encapsidated in virions. CONCLUSIONS: On the basis of the data presented in this collaborative study, Sample 2 (code number 99/802) was established as the 2(nd) International Standard for parvovirus B19 DNA for NAT-based assays with a potency of 10(6) IU/ml (500 000 IU/vial).

Reliability of CE-marked NATs for HIV-1 subtype C detection and quantitation.

We compared seven CE-marked HIV-1 RNA nucleic acid amplification technology (NAT) based assays for their detection efficiency and quantitation concordance in regard to HIV-1 subtype C. We used 398 plasma samples from South African repeat blood donors identified as HIV positive at occasion of routine screening NAT performed mainly during the years 2010-2013, with most plasma samples reflecting recent HIV-1 infections. All HIV-1 subtype C specimens were detected, independent of mono- or dual-target assay design. In the same time period new variants of HIV-1 subtype B had been identified which were missed by some mono-target assays, a finding which was not corroborated for subtype C in our study. A high level of concordance of HIV-1 subtype C quantitation was determined for the HIV-1 NATs, showing successful standardization in this diagnostic field.

A simple, low-cost and green method for controlling the cytotoxicity of MXenes.

MXene phases are a member of the intriguing 2D material family, beyond graphene. They are good candidates for many applications, however, their potential toxicity is of crucial importance for future development. Herein, we present a simple, low-cost and fully green approach for controlling the potential cytotoxicity of 2D MXenes after delamination by harnessing the interactions that occur between the surface of MXene phases and natural biomacromolecule - collagen. We also demonstrate that the step-by-step adsorption and desorption of collagen from the surface of 2D MXenes is easily controlled using in situ zeta potential measurements coupled with dynamic light scattering (DLS) method. The obtained results demonstrated that the electrostatically driven unprecedented susceptibility of the MXenes' surfaces to collagen. Surface-modification reduces toxicity of MXenes in vitro i.e. adjust cells' viabilities as well as reduce their oxidative stress. This indicates enhanced biocompatibility of 2D Ti3C2 and Ti2C MXenes surface-modified with collagen, which is involved in many bio-interactions as important building blocks in the human body. The presented study opens new avenues for designing MXenes with defined surface properties and paves the way for their future successful management in nano-medicinal applications.

Forty years of atmospheric radiocarbon monitoring around Bohunice nuclear power plant, Slovakia.

Radiocarbon variations in the atmospheric CO(2) with attenuating amplitudes and decreasing mean values with typical maxima in summer and minima in winter have been observed since 1967 in two localities of Slovakia, in Bratislava and Zlkovce, situated about 60 km NE from Bratislava, only 5 km from the Bohunice Nuclear Power Plant (NPP). The (14)C record in Bratislava has been influenced mainly by fossil CO(2) emissions, in contrast to the Zlkovce record which has been more variable, as it has clearly been affected by operation of the Bohunice NPP. However, during specific meteorological conditions with NE transport of air masses to Bratislava, the effect of the Bohunice NPP has been visible in Bratislava as well. Maximum (14)C concentrations (up to 120% above a natural background) were observed around A1 NPP which used CO(2) with admixture of air as a cooling agent. The (14)C concentrations around four pressurized light water reactors were up to 30% above the background. The Delta(14)C values in the heavily polluted atmosphere of Bratislava were up to 10% and at Zlkovce up to 5% lower than the European clean air represented by the Jungfraujoch Delta(14)C data. Later the Delta(14)C values were similar at both sites, and from 2003 they were close to the European clean air levels. The observed Delta(14)C behaviour in the atmosphere provides a unique evidence of decreased fossil fuel CO(2) emissions in the region, as well as the long-term effect of the Bohunice NPP on the Bratislava and Zlkovce stations. The estimated annual radiation doses to the local public due to digestion of radiocarbon contaminated food have been estimated to be around 3 microSv.

An international collaborative study to establish the 2nd World Health Organization International Standard for hepatitis B virus DNA nucleic acid amplification technology-based assays.

BACKGROUND AND OBJECTIVES: The aim of this study was to replace the 1st World Health Organization International Standard for hepatitis B virus DNA for nucleic acid amplification technique (NAT)-based assays (code 97/746) with a new International Standard. Two lyophilized preparations freeze dried from the same bulk were evaluated in the original collaborative study (coded 97/746 and 97/750, and termed AA and BB, respectively, in the original study). This present study re-evaluates these two preparations in terms of potency and real-time stability. MATERIALS AND METHODS: The 1(st) International Standard (97/746) and the second lyophilized preparation (97/750) were coded Samples 1 and 2, respectively, in the present study. The samples were distributed to six laboratories and assayed on four separate occasions. Accelerated thermal degradation samples of the two preparations were examined after long-term storage at 4 degrees C and 20 degrees C for more than 51 months. RESULTS: Data were returned from a total of nine different NAT-based assays, five in qualitative format and four in quantitative format. The results of this study confirm the results of the original collaborative study, with no significant differences being found in estimated international units (IU)/ml or polymerase chain reaction-detectable units/ml for the 1(st) International Standard (Sample 1 in this study) and the proposed replacement preparation, Sample 2 (97/750). Real-time and accelerated degradation studies indicate that both samples are very stable. Storage of both preparations at 20 degrees C for more than 51 months resulted in no detectable degradation. CONCLUSIONS: On the basis of the data presented in this collaborative study, Sample 2 (code 97/750) was established as the 2nd International Standard for hepatitis B virus DNA for NAT-based assays with a potency of 10(6) IU/ml (500,000 IU/vial).

Impact of the Bohunice Nuclear Power Plant on atmospheric radiocarbon.

Radiocarbon variations in the atmospheric CO(2) have been observed at two localities in Slovakia (Bratislava and Zlkovce). Zlkovce is situated about 60 km NE from Bratislava, and only 5 km from the Bohunice Nuclear Power Plant (NPP). The observed Delta(14)C levels provide a unique evidence of the long-term impact of the Bohunice NPP on the Bratislava region, as well as on the decreased fossil fuel CO(2) emissions. The radiation doses estimated to the local public have been around 3 microSv/year, 20% of the dose from global fallout (14)C present in the environment.

A549 and MRC-5 cell aggregation in a microfluidic Lab-on-a-chip system.

In this paper, we present a culture of A549 and MRC-5 spheroids in a microfluidic system. The aim of our work was to develop a good lung cancer model for the evaluation of drug cytotoxicity. Our research was focused on determining the progress of cell aggregation depending on such factors as the depth of culture microwells in the microdevices, a different flow rate of the introduced cell suspensions, and the addition of collagen to cell suspensions. We showed that these factors had a significant influence on spheroid formation. It was found that both MRC-5 and A549 cells exhibited higher aggregation in 500 µm microwells. We also noticed that collagen needs to be added to A549 cells to form the spheroids. Optimizing the mentioned parameters allowed us to form 3D lung tissue models in the microfluidic system during the 10-day culture. This study indicates how important an appropriate selection of the specified parameters is (e.g., geometry of the microwells in the microsystem) to obtain the spheroids characterized by high viability in the microfluidic system.

Establishment of the Ph. Eur. Hepatitis A virus RNA for NAT testing BRP batch 1.

Detection of viral contamination in plasma donations is critical to prevent transmission of infectious diseases. The European Pharmacopoeia (Ph. Eur.) monograph 1646 'Human plasma (pooled and treated for virus inactivation)', requires that plasma pools used for the manufacture of this product be tested, among others, for the presence of hepatitis A virus RNA by nucleic acid testing (NAT) using a positive control containing 100 International Units (IU) of hepatitis A virus (HAV) RNA per mL. To this end, the European Directorate for the Quality of Medicines & HealthCare (EDQM, Council of Europe) organised an international collaborative study under the aegis of the Biological Standardisation Programme, for the establishment of the 1st Biological Reference Preparation (BRP) for HAV RNA for NAT testing. A freeze-dried candidate material was thus prepared and calibrated against the WHO 2nd International Standard for HAV for NAT (00/562) in a study in which thirteen European and North American laboratories including Official Medicines Control Laboratories (OMCLs), manufacturers of plasma-derived products, producers of in vitro diagnostic kits and a blood transfusion centre participated. Based on the outcome of the study, an HAV RNA content of 40 000 IU/vial (corresponding approximately to 4.6 log10 IU/vial) was assigned to the BRP, which was adopted by the Ph. Eur. Commission in March 2016 as Ph. Eur. hepatitis A virus RNA for NAT testing BRP batch 1.

In vitro studies on cytotoxicity of delaminated Ti3C2 MXene.

MXenes are a novel family of 2D materials, the biological activity of which has been largely unexplored. The present study, for the first time, shows some aspects of the in vitro toxicity of 2D sheets of Ti3C2 MXene. The Ti3AlC2 MAX phase was used in an expansion and delamination process to obtain Ti3C2 material in the form of 2D sheets. The obtained 2D material was characterized using SEM, TEM, DLS, XPS, and zeta potential. The biological activity of the MXene was determined on two normal (MRC-5 and HaCaT) and two cancerous (A549 and A375) cell lines. The cytotoxicity results indicated that the observed toxic effects were higher against cancerous cells compared to normal ones. The mechanisms of potential toxicity were also elucidated. It was shown that MXene may affect the occurrence of oxidative stress and, in consequence, the generation of reactive oxygen species (ROS). The results of the present study provide the principal knowledge to date regarding the biological activity of the MXenes; the lack of such knowledge is the major obstacle on the MXenes' road to further research and development on their applications in bioscience and biotechnology, e.g. as drug-delivery systems.

Molecular epidemiology of West Nile Virus in humans.

After the introduction of West Nile Virus into the United States of America in 1999 followed by annual WNV epidemics during the mosquito seasons and spreading of the virus from the East (New York; 1999) to the West of the U.S. (California; 2003/2004) there appeared the question of whether a similar scenario could happen in Europe, too. To be able to answer this question the German Ministry of Health decided to investigate the prevalence and incidence of WNV infections in German blood donors. First a test algorithm was established taking into account the high level of cross-reactivity between different flavivirus infections in serological test systems. AntiWNV-suspicious specimens were further investigated for their neutralisation capacity and by an antiWNV confirmation assay developed in-house. As a preliminary result of our studies a very low prevalence of WNV infections in healthy German blood donors was measured. Development of highly specific test systems is necessary for accurate and reliable differential diagnosis of flavivirus infections.

A natural asymptomatic herpes B virus infection in a colony of laboratory brown capuchin monkeys (Cebus apella).

Herpes B virus (BV) infection of macaques persists in the natural host, but is mainly asymptomatic. However, BV can cause fatal disease in humans and in several non-macaque species such as capuchin monkeys (Cebus apella). The BV infection described here in a colony of capuchin monkeys was persistent but asymptomatic. Initially the infection was detected serologically in five out of seven animals. However, using polymerase chain reaction (PCR) developed specifically for BV, we found the virus in all seven clinically healthy animals. It is probable that the infection was transferred from BV-infected macaques housed in different cages but in the same room for several years. We have no evidence to indicate that similar asymptomatic infections may occur in other New World species but the possibility should not be discounted. We recommend that the housing of capuchin monkeys in close proximity to macaques should be avoided and that greater caution should be used when handling capuchin monkeys and possibly other New World species that have been in contact with macaques. All may act as a source of BV infection in humans, hence routine, repeated testing of all primates is essential.

Performance of hepatitis B surface antigen tests with the first WHO international hepatitis B virus genotype reference panel.

BACKGROUND: Standardization of hepatitis B surface antigen (HBsAg) tests is indispensable for consistent quality and comparability. Ideally, the assays should detect all known hepatitis B virus (HBV) genotypes equally well. OBJECTIVE: Development of an HBV genotype reference panel for HBsAg assays representing the most prevalent HBV subgenotypes to address commutability and traceability of the heat-inactivated 2nd WHO International Standard (IS) for HBsAg in relation to native HBsAg and to HBV genotypes. STUDY DESIGN: An HBV panel of 15 non-inactivated lyophilized specimens representing the subgenotypes A1, A2, B1, B2, C2, D1-D3, E, F2, and H was evaluated in parallel to the IS by 15 laboratories using 19 different HBsAg tests and tree unitages. The virus content of the samples was reduced by ultracentrifugation and dilution to <2×10(4) IU HBV DNA/mL. RESULTS: Twenty-two qualitative and 6 quantitative data sets were evaluated. Overall, the results demonstrated consistent detection of HBV genotypes by the majority of tests with a mean potency variability relative to the IS of 36%. Some assays showed significant genotype-dependent differences in analytical sensitivity. Some tests were more sensitive with the IS, others less. On average, one IU HBsAg corresponded to 0.88±0.20 ng HBsAg protein. CONCLUSIONS: The panel was accepted by the WHO as the "1st International Reference Panel for HBV genotypes for HBsAg-based assays". The panel is a helpful complementation to the IS to validate HBV genotype specific analytical test sensitivities.

First WHO International Reference Panel containing hepatitis B virus genotypes A-G for assays of the viral DNA.

BACKGROUND: WHO International Standards (IS) are provided for the calibration and validation of diagnostic and screening assays, e.g. for hepatitis B virus (HBV). HBV forms numerous subgenotypes and the current IS for HBV DNA reflects subgenotype A2. OBJECTIVE: A reference panel with the most prevalent subgenotypes should facilitate evaluation of genotype-specific detection efficiencies. STUDY DESIGN: 215 HBV positive plasma samples collected worldwide were characterized for HBV markers and sequenced. Fifteen subgenotype A1, A2, B2, B4, C2, D1, D3, E, F2 and G samples were selected for the panel. The lyophilized samples were tested in parallel with the IS in an international collaborative study with 16 laboratories using 13 different nucleic acid amplification techniques (NATs). RESULTS: Eight of 13 NAT had a HBV DNA detection efficiency which was independent of the genotype and consistent with the IS, while with five assays, certain deviations were noted, particularly with genotype F which was under quantitated or even missed by three assays. The panel was accepted by the WHO as the "1st WHO International Reference Panel for HBV Genotypes for HBV NAT-Based Assays". CONCLUSIONS: The evaluation of HBV DNA assays should include many different genotypes. The WHO Reference Panel is universally available for manufacturers of HBV DNA assays, diagnostic laboratories and control authorities to facilitate standardized validation of HBV genotype specific detection efficiency of both diagnostic (quantitative and qualitative) and screening NAT assays.

Long-term variations of 14C and 137Cs in the Bratislava air--implications of different atmospheric transport processes.

This study summarizes measurements of atmospheric (14)C and (137)Cs in the Bratislava air since 1976. Higher (14)C levels observed in spring and early summer months until the 1980's confirm injection of the stratospheric air into the troposphere. Later, deep winter minima were observed in (14)C concentrations, probably due to the depletion of the atmospheric (14)C levels in winter months by the injection of large quantities of fossil CO(2). Presently observed (14)C maxima in summer and minima in winter were caused by the depletion of the atmospheric (14)C in winter months, amplified by temperature inversions during winter, rather than by the injection of the stratospheric air into the troposphere. The observed (137)Cs activity concentrations also showed an impact of the stratospheric air on the (137)Cs levels until the early 1980's, documented by typical spring/early summer maxima and winter minima. The global fallout (137)Cs record was then disturbed by the Chernobyl accident (1986) when large quantities of (137)Cs were released to the atmosphere. The recent (137)Cs variations observed in the atmosphere, characterised by winter maxima and summer minima, are assumed to be mainly due to the resuspension of (137)Cs from the soil. A correlation was found between the (137)Cs activity concentration and the dust level in the air (the correlation coefficient r = 0.74), as well as an anticorrelation with the temperature (r = -0.56).

First case of hepatitis C virus transmission by a red blood cell concentrate after introduction of nucleic acid amplification technique screening in Germany: a comparative study with various assays.

BACKGROUND AND OBJECTIVES: Pooled nucleic acid amplification techniques (NAT) and donor screening for anti-hepatitis C virus (HCV) have reduced the diagnostic window period of HCV infection in the blood donor population from about 12 to 1 or 2 weeks. During that time, HCV RNA is hardly detectable by pooled or individual donation NAT. Here we describe a case of transfusion-acquired HCV infection from an extremely low-titre donation. After a repeat donor tested positive for HCV, a look-back procedure was initiated. A recipient of a red cell concentrate from the previous donation was identified and found to be infected with HCV as well. We compared several commercial NAT systems for their ability to detect the viraemic plasma. MATERIALS AND METHODS: Molecular analyses of HCV in donor and recipient samples were performed. The HCV-transmitting plasma was tested using different commercially available qualitative and quantitative NAT assays. RESULTS: HCV transmission was verified by molecular analyses and was assigned to genotype 2b. NAT with various commercial HCV assays detected the infection erratically in individual donations. However, the detection rate was not directly related to the claimed sensitivity of some HCV NATs. CONCLUSIONS: HCV transmission can be caused by donations that escape NAT detection even when tested in an individual donation. Comparison of different assays led to results that did not necessarily reflect the expected sensitivities. The need for standard materials representing further HCV genotypes is discussed.