Immobilization methods for continuous hydrogen gas production biofilm formation versus granulation

Hydrogen gas was continuously produced by treating glucose-containing synthetic wastewater with sewage digester sludge. The activity of methanogenic bacteria in the sludge was repressed by pH-control at 5.0 under anaerobic conditions. For efficient continuous hydrogen production. two immobilization methods were employed, biofilm formation on poly vinyl alcohol (PVA) and granulation of the sludge with cationic and anionic polymers. Acetic acid was the dominant fatty acid in the early operation stage in both cases. In the case of the biofilm, biogas production at 20 h hydraulic retention time was severely repressed to around 50 ml/L-reactor/h when propionic acid was sharply increased after 20 days of operation. In the case of granular sludge, propionic acid was produced only during the early operation stage and the biogas production rate was maintained at around 300 ml/L-reactor/h at 20 h of hydraulic retention time. The hydrogen gas content in the biogas was in the range of 40-60% and no methane was detected either case. Since granular sludge harboured more microorganisms and its density was higher than the biofilm on PVA medium, granulation was considered to be a better method for continuous hydrogen gas production. (C) 2004 Elsevier Ltd. All rights reservedclos

Six Germline Genetic Variations Impair the Translesion Synthesis Activity of Human DNA Polymerase kappa

DNA polymerase (pol) κ efficiently catalyzes error-free translesion DNA synthesis (TLS) opposite bulky N2-guanyl lesions induced by carcinogens such as polycyclic aromatic hydrocarbons. We investigated the biochemical effects of nine human nonsynonymous germline POLK variations on the TLS properties of pol κ, utilizing recombinant pol κ (residues 1-526) enzymes and DNA templates containing an N2-CH2(9-anthracenyl)G (N2-AnthG), 8-oxo-7,8-dihydroguanine (8-oxoG), O6-methyl(Me)G, or an abasic site. In steady-state kinetic analyses, the R246X, R298H, T473A, and R512W variants displayed 7- to 18-fold decreases in kcat/Km for dCTP insertion opposite G and N2-AnthG, with 2- to 3-fold decreases in DNA binding affinity, compared to that of the wild-type, and further showed 5- to 190-fold decreases in kcat/Km for next-base extension from C paired with N2-AnthG. The A471V variant showed 2- to 4-fold decreases in kcat/Km for correct nucleotide insertion opposite and beyond G (or N2-AnthG) compared to that of the wild-type. These five hypoactive variants also showed similar patterns of attenuation of TLS activity opposite 8-oxoG, O6-MeG, and abasic lesions. By contrast, the T44M variant exhibited 7- to 11-fold decreases in kcat/Km for dCTP insertion opposite N2-AnthG and O6-MeG (as well as for dATP insertion opposite an abasic site) but not opposite both G and 8-oxoG, nor beyond N2-AnthG, compared to that of the wild-type. These results suggest that the R246X, R298H, T473A, R512W, and A471V variants cause a general catalytic impairment of pol κ opposite G and all four lesions, whereas the T44M variant induces opposite lesion-dependent catalytic impairment, i.e., only opposite O6-MeG, abasic, and bulky N2-G lesions but not opposite G and 8-oxoG, in pol κ, which might indicate that these hypoactive pol κ variants are genetic factors in modifying individual susceptibility to genotoxic carcinogens in certain subsets of populations. © 2016 American Chemical Society.

Solid Free-Form Fabrication of Tissue-Engineering Scaffolds with a Poly(lactic-co-glycolic acid) Grafted Hyaluronic Acid Conjugate Encapsulating an Intact Bone Morphogenetic Protein-2/Poly(ethylene glycol) Complex

Despite wide applications of bone morphogenetic protein-2 (BMP-2), there are few methods to incorporate BPM-2 within polymeric scaffolds while maintaining biological activity. Solid free-form fabrication (SFF) of tissue-engineering scaffold is successfully carried out with poly(lactic-co-glycolic acid) grafted hyaluronic acid (HA-PLGA) encapsulating intact BMP-2/poly(ethylene glycol) (PEG) complex. HA-PLGA conjugate is synthesized in dimethyl sulfoxide (DMSO) by the conjugation reaction of adipic acid dihydrazide modified HA (HA-ADH) and PLGA activated with N,N'-dicyclohexylcarbodilmide (DCC) and N-hydroxysuccinimide (NHS). BMP-2 is complexed with PEG, which is encapsulated within the PLGA domain of the HA-PLGA conjugate by SFF to prepare tissue-engineering scaffolds. In vitro release tests confirm the sustained release of intact BMP-2 from the scaffolds for up to a month. After confirmation of the enhanced osteoblast cell growth, and high gene-expression levels of alkaline phosphatase (ALP), osteocalcin (OC), and osterix (OSX) in the cells, the HA-PLGA/PEG/BMP-2 scaffolds are implanted into calvarial bone defects of Sprague Dawley (SD) rats. Microcomputed tomography (mu CT) and histological analyses with Masson's trichrome, and hematoxylin and eosin (H&E) staining reveal effective bone regeneration on the scaffolds of HA-PLGA/PEG/BMP-2 blends.X116165sciescopu

Guided bone regeneration by poly(lactic-co-glycolic acid) grafted hyaluronic acid bi-layer films for periodontal barrier applications

A novel protocol for the synthesis of biocompatible and degradation controlled poly(lactic-co-glycolic acid) grafted hyaluronic acid (HA-PLGA) was successfully developed for periodontal barrier applications. HA was chemically modified with adipic acid dihydrazide (ADH) in the mixed solvent of water and ethanol, which resulted in a high degree of HA modification up to 85 mol.%. The stability of HA-ADH to enzymatic degradation by hyaluronidase increased with ADH content in HA-ADH. When the ADH content in HA-ADH was higher than 80 mol.%, HA-ADH became soluble in dimethyl sulfoxide and could be grafted to the activated PLGA with N,N'-dicyclohexyl carbodiimide and N-hydroxysuccinimide. The resulting HA-PLGA was used for the preparation of biphasic periodontal barrier membranes in chloroform. According to in vitro hydrolytic degradation tests in phosphate buffered saline, HA-PLGA/PLGA blend film with a weight ratio of 1/2 degraded relatively slowly compared to PLGA film and HA coated PLGA film. Four different sa I triples of a control, OSSIX (TM) membrane, PLGA film, and HA-PLGA/PLGA film were assessed as periodontal barrier membranes for the calvarial critical size bone defects in SD rats. Histological and histomorphometric analyses revealed that HA-PLGA/PLGA film resulted in the most effective bone regeneration compared to other samples with a regenerated bone area of 63.1% covering the bone defect area. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.X1137sciescopu

Environmental contamination in the isolation rooms of COVID-19 patients with severe pneumonia requiring mechanical ventilation or high-flow oxygen therapy.

BackgroundIdentifying the extent of environmental contamination of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is essential for infection control and prevention. The extent of environmental contamination has not been fully investigated in the context of severe coronavirus disease (COVID-19) patients.AimTo investigate environmental SARS-CoV-2 contamination in the isolation rooms of severe COVID-19 patients requiring mechanical ventilation or high-flow oxygen therapy.MethodsEnvironmental swab samples and air samples were collected from the isolation rooms of three COVID-19 patients with severe pneumonia. Patients 1 and 2 received mechanical ventilation with a closed suction system, while patient 3 received high-flow oxygen therapy and non-invasive ventilation. Real-time reverse transcription-polymerase chain reaction (rRT-PCR) was used to detect SARS-CoV-2; viral cultures were performed for samples not negative on rRT-PCR.FindingsOf the 48 swab samples collected in the rooms of patients 1 and 2, only samples from the outside surfaces of the endotracheal tubes tested positive for SARS-CoV-2 by rRT-PCR. However, in patient 3's room, 13 of the 28 environmental samples (fomites, fixed structures, and ventilation exit on the ceiling) showed positive results. Air samples were negative for SARS-CoV-2. Viable viruses were identified on the surface of the endotracheal tube of patient 1 and seven sites in patient 3's room.ConclusionEnvironmental contamination of SARS-CoV-2 may be a route of viral transmission. However, it might be minimized when patients receive mechanical ventilation with a closed suction system. These findings can provide evidence for guidelines for the safe use of personal protective equipment

Three-dimensional bioprinting of multilayered constructs containing human mesenchymal stromal cells for osteochondral tissue regeneration in the rabbit knee joint

The use of cell-rich hydrogels for three-dimensional (3D) cell culture has shown great potential for a variety of biomedical applications. However, the fabrication of appropriate constructs has been challenging. In this study, we describe a 3D printing process for the preparation of a multilayered 3D construct containing human mesenchymal stromal cells with a hydrogel comprised of atelocollagen and supramolecular hyaluronic acid (HA). This construct showed outstanding regenerative ability for the reconstruction of an osteochondral tissue in the knee joints of rabbits. We found that the use of a mechanically stable, host-guest chemistry-based hydrogel was essential and allowed two different types of extracellular matrix (ECM) hydrogels to be easily printed and stacked into one multilayered construct without requiring the use of potentially harmful chemical reagents or physical stimuli for post-crosslinking. To the best of our knowledge, this is the first study to validate the potential of a 3D printed multilayered construct consisting of two different ECM materials (atelocollagen and HA) for heterogeneous tissue regeneration using an in vivo animal model. We believe that this 3D printing-based platform technology can be effectively exploited for regeneration of various heterogeneous tissues as well as osteochondral tissue.114418Nsciescopu