Virucidal activity of Cu-doped TiO2 nanoparticles under visible light illumination: Effect of Cu oxidation state

Copper (Cu) is an effective antimicrobial material; however, its activity is inhibited by oxidation. Titanium dioxide (TiO2) photocatalysis prevents Cu oxidation and improves its antimicrobial activity and stability. In this study, the virucidal efficacy of Cu-doped TiO2 nanoparticles (Cu-TiO2) with three different oxidation states of the Cu dopant (i.e., zero-valent Cu (Cu0), cuprous (CuI), and cupric (CuII) oxides) was evaluated for the phiX174 bacteriophage under visible light illumination (Vis/Cu-TiO2). CuI-TiO2 exhibited superior virucidal activity (5 log inactivation in 30 min) and reusability (only 11 % loss of activity in the fifth cycle) compared to Cu0-TiO2 and CuII-TiO2. Photoluminescence spectroscopy and photocurrent measurements showed that CuI-TiO2 exhibited the highest charge separation efficiency and photocurrent density (approximately 0.24 μA/cm2) among the three materials, resulting in the most active redox reactions of Cu. Viral inactivation tests under different additives and viral particle integrity analyses (i.e., protein oxidation and DNA damage analyses) revealed that different virucidal species played key roles in the three Vis/Cu-TiO2 systems; Cu(III) was responsible for the viral inactivation by Vis/CuI-TiO2. The Vis/CuI-TiO2 system exhibited substantial virucidal performance for different viral species and in different water matrices, demonstrating its potential practical applications. The findings of this study offer valuable insights into the design of effective and sustainable antiviral photocatalysts for disinfection.

Practical scale evaluation of a photocatalytic air purifier equipped with a Titania-zeolite composite bead filter for VOC removal and viral inactivation

A practical scale photocatalytic air purifier equipped with a TiO₂/H-ZSM-5 composite bead filter was demonstrated to be able to effectively remove indoor volatile organic compounds (VOCs) and viruses with sustainable performances under UVA-LED illumination. TiO₂ hybridized with 5 wt% H-ZSM-5 zeolite significantly enhanced its photocatalytic activity for degrading VOCs including formaldehyde, acetaldehyde, and toluene, than bare TiO₂. H-ZSM-5 provided strong adsorption sites for these compounds, thus accelerating their photocatalytic conversion into CO₂ by adjacent TiO₂ photocatalyst. Moreover, owing to its superior adsorption capacity, the composite bead filter completely prevented the emission of formaldehyde produced by photocatalytic oxidation of toluene. The sustainability of this composite bead filter for VOC removal was confirmed by regeneration and accelerated durability tests. In addition, the photocatalytic air purifier was effective in removing aerosolized viral particles of bacteriophage Phi-X 174. It was confirmed that the viruses on filter surfaces were completely inactivated by photocatalytic oxidation. TiO₂/H-ZSM-5 composite beads also exhibited excellent efficacies for inactivation of pathogenic coronaviruses including SARS-CoV-2. The photocatalytic process degraded viral RNAs of SARS-CoV-2 by more than 99.999% in 1 h, eliminating the viral infectivity. Results of this study suggest that the air purifier equipped with the composite bead filter is ready for practical applications for home and hospital uses.

Fabrication of Ag-doped ZnO/PAN composite nanofibers by electrospinning: Photocatalytic and antiviral activities

Ag-doped ZnO nanoparticles (AZNs) were directly synthesized using sol-gel method to embed into polyacrylonitrile (PAN) nanofibers by electrospinning. The synthesized AZNs were optically and structurally characterized by UV-VIS spectroscopy, photoluminescence spectroscopy, high resolution HR-TEM and XRD. The photocatalytic activity of the AZNs was examined by photocatalytic degradation of methylene blue to correlate with their antiviral efficacy in PAN nanofibers fabricated via electrospinning technique. The PAN nanofibers containing AZNs were characterized using SEM and EDS. Finally, antiviral activity of AZNs/PAN nanofibers was investigated by using virus ϕx174 under visible light irradiation. As a result, the antiviral efficacy of nanofibers increased as the concentration of Ag in AZNs increased. The results show that better antiviral efficacy was obtained in AZNs/PAN nanofibers prepared with AZNs of higher photocatalytic performance.

Shaping of a Metal-Organic Framework-Polymer Composite and Its CO2 Adsorption Performances from Humid Indoor Air

Diamine-functionalized metal-organic frameworks (MOFs) are known as desirable adsorbents that can capture CO₂ even at low pressures, but the humidity instability of bare MOF powders as well as their shaping have not yet adequately addressed for practical applications. Herein, we report an effective synthetic strategy for fabricating millimeter-sized MOF/poly(vinylidene fluoride) (PVDF) composite beads with different amounts of PVDF binders (30, 40, and 50 wt %) via a phase inversion method, followed by the postfunctionalization of 1-ethylpropane-1,3-diamine (epn). Compared with the pristine MOF powder, the diamine-grafted bead, epn-MOF/PVDF40, upon mixing with 40% binder polymers, exhibited a superior long-term performance without structural collapse for up to 1 month. The existence of the hydrophobic PVDF polymer in the composite material is responsible for such durability. This work provides a promising preparative route toward developing stable and shaped MOFs for the removal of indoor CO₂.

Metal-Organic Framework Adsorbent for Practical Capture of Trace Carbon Dioxide

Control of indoor CO₂ concentration to a safe level is important to human health. Metal-organic-framework-based adsorbents show superior adsorption performance at moderate CO₂ concentration compared to other solid adsorbents but suffer from low capacities and high regeneration temperature at indoor CO₂ concentrations and poor humidity stability. Herein, we report epn-grafted Mg₂(dobpdc) (epn = 1-ethylpropane-1,3-diamine) showing a CO₂ capacity of 12.2 wt % at an acceptable concentration of 1000 ppm and a practically low desorption temperature of 70 °C, which surpasses the performance of conventional solid adsorbents under the given conditions. After poly(dimethylsiloxane) coating, this material reveals a significant adsorption amount (∼10 wt %) in humid conditions (up to 98% relative humidity) with structural durability.

Demetylation of the sex-determining region Y gene promoter and incidence of disorder of sex development in cloned dog males

Canine cloning is occasionally accompanied by abnormal sexual development. Some male donor cells produce cloned pups with female external genitalia and complete male gonadal dysgenesis, which is classified as an XY disorder of sex development (XY DSD). In this study, we examine the potential of 5-aza-2'-deoxycytidine (5-aza-dC), a DNA methyltransferase inhibitor, to reduce the phenotypic abnormality XY DSD in somatic cell nuclear transfer (SCNT)- derived pups. We used a 9-year-old normal male German Shepherd dog as a cell donor. Donor cells were treated with 10 nM 5-aza-dC for 4 days before being used for SCNT. At the same stage of cell development, significantly lower levels of DNA methylation of the sex-determining region Y (SRY) promoter was observed in the treated donor cells compared to that in the untreated cells (95.2% versus 53.3% on day 4 for the control and treated groups, respectively). No significant differences were observed in the control or treatment groups concerning fusion rate, pregnancy rate (30 days or entire period), the number of pups, or the incidence of XY DSD. However, more XY DSD dogs were observed in the control group (31.25%) than in the treatment group (14.29%). Hypermethylation of the SRY promoter was observed in the XY DSD cloned pups in both the treatment (84.8%) and control groups (91.1 ± 1.4%) compared to the methylation level in the phenotypically normal male pups of the treatment (23.2 ± 20.9%) and control groups (39.1 ± 20.1%). These results suggest that 5-aza-dC treatment of donor cells can reduce the methylation level of the SRY promoter in donor cells, and thus, 5-aza-dC is advantageous for reducing the incidence of XY DSD in canine cloning.

Lipopolysaccharide-induced indoleamine 2,3-dioxygenase expression in the periodontal ligament

BACKGROUND AND OBJECTIVE

Indoleamine 2,3-dioxygenase (IDO) is a tryptophan-oxidizing enzyme with immune-inhibitory effects. The aim of this study was to investigate the expression of IDO by lipopolysaccharide (LPS), a component of gram-negative bacteria, in human periodontal ligament (PDL) cells.

MATERIAL AND METHODS

Human PDL cells and gingival fibroblasts (GFs) were prepared from explants of human PDLs and from gingival tissues of clinically healthy donors, respectively. Real-time RT-PCR, western blotting and the IDO enzyme assay were performed to determine the expression of IDO following LPS treatment of cells. LPS was injected into mice tail veins to evaluate the effects of LPS in vivo in the maxillary first molar. Immunofluorescence staining and histological analysis were followed to localize IDO in mouse PDL.

RESULTS

The level of expression of IDO mRNA in primary human PDL cells after LPS treatment was increased in a dose-dependent manner, reaching a peak 8 h after LPS treatment. The expression and activities of IDO protein were significantly increased in comparison with those of the control. In addition, the increased production of kynurenine in culture medium was observed 72 h after LPS treatment. In the immunofluorescence findings, stronger immunoreactivities were shown in PDL than in gingival tissues in the maxillae. In accordance with the immunofluorescence findings, LPS treatment induced a strong up-regulation of IDO mRNA in human PDL cells, whereas human GFs showed only a weak response to LPS.

CONCLUSION

These results clearly show that IDO was induced by LPS in primary human PDL cells, suggesting that PDL might be involved in the regulation of oral inflammatory disease.

The analysis of telomere length and telomerase activity in cloned pigs and cows

Inefficiency in the production of cloned animals is most likely due to epigenetic reprogramming errors after somatic cell nuclear transfer (SCNT). In order to investigate whether nuclear reprogramming restores cellular age of donor cells after SCNT, we measured telomere length and telomerase activity in cloned pigs and cattle. In normal pigs and cattle, the mean telomere length was decreased with biological aging. In cloned or transgenic cloned piglets, the mean telomere length was elongated compared to nuclear donor fetal fibroblasts and age-matched normal piglets. In cloned cattle, no increases in mean telomere length were observed compared to nuclear donor adult fibroblasts. In terms of telomerase activity, significant activity was observed in nuclear donor cells and normal tissues from adult or new-born pigs and cattle, with relatively higher activity in the porcine tissues compared to the bovine tissues. Cloned calves and piglets showed the same level of telomerase activity as their respective donor cells. In addition, no difference in telomerase activity was observed between normal and transgenic cloned piglets. However, increased telomerase activity was observed in porcine SCNT blastocysts compared to nuclear donor cells and in vitro fertilization (IVF)-derived blastocysts, suggesting that the elongation of telomere lengths observed in cloned piglets could be due to the presence of higher telomerase activity in SCNT blastocysts. In conclusion, gathering from the comparative studies with cattle, we were able to demonstrate that telomere length in cloned piglets was rebuilt or elongated with the use of cultured donor fetal fibroblasts.

Antibiotic selective pressure for the maintenance of antibiotic resistant genes in coliform bacteria isolated from the aquatic environment

Coliform bacteria isolated from the aquatic environment were investigated for antibiotic susceptibility and detailed structures of class 1 integrons. A high proportion of isolates were found to be resistant to sulfamethoxazole, aminoglycosides, and beta-lactams. The 750 (53.6%) isolates were resistant to one or more of the antibiotics tested out of 1,400 coliform bacteria. Based on the MIC of antibiotics and antibiogram, 150 isolates were selected and further studied for class 1 integrons. The intI1 gene was found in 36 (24.0%) of the 150 isolates. Twelve isolates carried the gene cassettes responsible for antibiotic resistance, while no gene cassettes were found in 24 isolates. Seven different genes, dfrA5, dfrA7, dfrA12, dfrA17, aaA2, aaA5, and aad(3'), were detected in gene cassettes. The dfrA and aad genes located on class 1 integrons were responsible for resistance to trimethoprim and aminoglycosides. The remaining 24 coliform bacteria had the incomplete or non-functional class 1 integrons. These results indicated that antibiotic selective pressures may play an important role to maintain gene cassettes of class 1 integrons and in the absence of sustained antibiotic pressures, such as the aquatic environment, coliform bacteria may carry empty or non-functional class 1 integrons.

p21(WAF1) is associated with CDK2 and CDK4 protein during HL-60 cell differentiation by TPA treatment

TPA-treated HL-60 cells are mainly arrested in G1 by p21(WAF1) accumulation. We investigate the downstream changes following such accumulation. Increased p21(WAF1) is associated with CDK2 and CDK4. pRb is dephosphorylated in the presence of p21-CDK2/4 complexes, and the Rb-E2F1 complex increases after TPA treatment, whereas the Rb-HDAC1 complex decreases slightly. Our results suggest that increased p21(WAF1) is associated with CDK2/4, and that these complexes induce pRb dephosphorylation. In turn, hypophosphorylated pRb are mainly complexed with E2F1, but HDAC1 appears not to be a key component in this process.

Apoptotic cell death induced by Acinetobacter baumannii in epithelial cells through caspase-3 activation

Epithelial cell death induced by Acinetobacter baumannii infection was investigated using in vitro assays. Eight hours after live A. baumannii infection, HeLa cells exhibited detachment from the dish, rounding morphologies, high proportions of trypan blue-positive cells and extensive DNA breakdown with faint apoptotic banding, which is indicative of cells undergoing apoptosis. The enzymatic activity of caspase-3 was increased in cells as early as 2 h after infection. In addition, apoptosis of HeLa cells was induced by treatment with bacterial culture filtrates but not with formalin-killed bacteria. These results indicate that A. baumannii infection triggers apoptosis in HeLa cells through caspase-3 activation.

Antimicrobial resistance of Shigella sonnei in Korea during the last two decades

Eighty-eight strains of Shigella sonnei isolated in Korea during the period 1980 to 1999 were tested for susceptibility to 13 antimicrobial agents. S. sonnei isolates demonstrated high frequencies of resistance to sulfamethoxazole (97.7%), tetracycline (96.6%), and trimethoprim (95.5%). S. sonnei isolates from the 1990s were more resistant to nalidixic acid than isolates from the 1980s (100 vs 7.7%), while isolates from the 1990s were more susceptible to chloramphenicol than isolates from the 1980s (0 vs 100%). Ampicillin-resistant S. sonnei isolates produced the TEM-1 beta-lactamase with a pI of 5.4. The TEM-1 gene was located on conjugally transferable plasmids in the majority of isolates. S. sonnei isolates were all susceptible to cefotaxime, cefoxitin, ceftazidime, ciprofloxacin, and norfloxacin. These results indicate that cephalosporins and quinolones may be alternative antibiotics for the treatment of S. sonnei infections in Korea.

Improved sample preparation for cross-sectional transmission electron microscopy of layered structures using rocking-angle ion-milling techniques

The rocking-angle ion-milling technique has been employed to produce optimum Pt/Ti/SiO2/Si, W/TiN/SiO2/Si, and (Pb,La)TiO3/Pt/MgO samples for cross-sectional transmission electron microscopy (TEM). Because of the different ion-milling rates between film layers and substrate materials, no satisfactory cross-sectional TEM samples could be obtained when they were made by the conventional ion-milling method. The differential thinning problems could be effectively solved by optimizing both ion-milling rocking-angle and ion-beam incidence angle without the increase of overall milling time. It was found that the rocking-angle of around 40 degrees is good when the multilayer structure is composed of materials with great ion-milling rate differences, while the rocking angle of around 80 degrees is good when the ion-milling rate differences are relatively small.