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Ways to Improve the Safety of Filtering Respiratory Protective Devices Against Bioaerosols
Published in Katarzyna Majchrzycka, Małgorzata Okrasa, Justyna Szulc, Respiratory Protection Against Hazardous Biological Agents, 2020
Katarzyna Majchrzycka, Justyna Szulc
In recent years, as a result of the cooperation of the IFR, USDA-ARS and the British Food Standards Agency (FSA), a ComBase database was created. It was created to collect data on the growth and inactivation of microorganisms in food and is systematically being expanded. ComBase contains over 60,000 curves describing the kinetics of growth or survive of microorganisms in microbiological media and various food products, taking into account many variable environmental factors. ComBase is a valuable source of knowledge about research being conducted and results achieved in the field of food microbiology, as well as allows for comparative research and validation of newly created predictive models [Amézquita et al. 2011; ComBase]. ComBase Predictor (CP) programme is available on the database's website, which enables creating predictions concerning the growth of microorganisms in response to such environmental factors as temperature, pH and water activity. CP contains 23 growth models and 6 thermal inactivation models. Among others, it gives the ability to establish specific bacterial growth rate or lag phase duration. In order to carry out the modelling using ComBase Predictor, the following input data are required: input temperature, pH, NaCl, water activity, carbon dioxide and nitrate content, duration of the given production stage, initial number of bacteria and physiological condition [ComBase website]. Currently, new microbial databases of Microbial Responses Viewer (MRV) are being created in relation with thorough testing of microorganisms included in the ComBase database.
Hydrogels Formed by Cross-Linked Poly(Vinyl Alcohol)
Published in Severian Dumitriu, Valentin Popa, Polymeric Biomaterials, 2020
The approach used to introduce electrophilic moieties on PVA is based [32] on the coupling of amino-derivatized PVA with N-hydroxysuccinimide ester of acids containing electrophilic groups as maleimide, acrylate, α-iodoacetyl functionalities (see Scheme 2.6). The elastic properties and the degree of swelling of the resulting hydrogels were, as expected, determined by the stability and density of the cross-links contributing to the network elasticity. The same group [33] designed hydrogel based on two PVA components, containing aldehydes and hydrazide side chains, respectively. In this study, encapsulation of murine neuroblastoma cells in the hydrogel was carried out during the cross-linking reaction occurring in aqueous medium at physiological condition of pH and temperature.
Cartilage Mechanobiology
Published in Jiro Nagatomi, Eno Essien Ebong, Mechanobiology Handbook, 2018
Hai Yao, Yongren Wu, Xin L. Lu
Mechanocoupling involves the conversion of applied physical force at tissue level into detectable physical signals at cellular level. Under physiological condition, the chondrocyte population is exposed to changes in a mechanical, physicochemical, and electrical environment of ECM, including spatial–temporal variations of stress, strain, fluid flow, fluid pressure, osmotic pressure, FCD, pH, electrical field, and solute transport within the ECM (Figure 15.2). At the final steady state of static loading condition (no fluid movement), there is a change (usually an increase) in the FCD, the concentration of positive counterions (Na+, H+, Ca2+), and the osmotic pressure due to the dilatation of ECM. This change may also inhibit aggrecan synthesis. Dynamic loading conditions, however, may promote the metabolic activities of chondrocytes through temporal variations of hydrostatic pressure, fluid flow, streaming potentials, or oscillations in cell shape. During excessive compression or impact loading, high levels of strain or strain rate can induce ECM disruption, tissue swelling, increased diffusion, and loss of ECM macromolecules through abrupt fluid convection. All of these physical phenomena (cell deformation, osmotic pressure, hydrostatic pressure, fluid flow, shear stress, and streaming potential) induced by mechanical loading at various levels can activate different signaling pathways in chondrocytes and can further result in distinct biochemical responses.
Keratin-dopamine conjugate nanoparticles as pH/GSH dual responsive drug carriers
Published in Journal of Biomaterials Science, Polymer Edition, 2020
Xiao Han, Lijuan Wang, Jinsong Du, Jie Dou, Jiang Yuan, Jian Shen
In order to minimize the toxicity and side effect of anticancer drugs, drug-loaded nanoparticles should be stimuli-responsive and release drugs at tumor site exactly. Compared with the normal physiological condition, the tumor microenvironments have lower pH and higher GSH levels. In this study, phosphate buffers (pH 5.0) and GSH (10 mM) were adopted to simulate tumor microenvironments. To test the pH and GSH sensitivity of DKNPs, the size and zeta potential under different pH and GSH conditions were measured through DLS method. As presented in Figure3, the size of nanoparticles (pH 5.0) was larger in the acidic environment than that in normal physiological condition (pH 7.4). It was attributed to the protonation of keratin and polydopamine (PDA), resulting in particle swelling. Correspondingly, the zeta potentials of the nanoparticles were all negative and changed from −23.7 mV to −17.6 mV, assigning to the protonation of keratin and PDA [28]. Furthermore, the size of DKNPs was sharply enlarged to 2260 nm in the presence of 10 mM GSH. The mutation of the particle size was due to the synergistic effect of the pH-triggered protonation and the reduction-triggered break of disulfide bonds within KNPs. Interestingly, when DKNPs were incubated in GSH solution, the zeta potential of the nanoparticles changed from negative (-17.6 mV) to positive (2.1 mV). This charge value was not high enough to make DKNPs stable, resulting in accumulation. Thus, DKNPs would efficiently aggregate and accumulate at tumor sites due to enhanced permeation retention effect (EPR).
Investigating folate-conjugated combinatorial drug loaded ZnO nanoparticles for improved efficacy on nasopharyngeal carcinoma cell lines
Published in Journal of Experimental Nanoscience, 2020
Here in our study, we adopted a slightly different kind of approach in this particular study and were influenced by the study by Asadishad et al [9]. We knew that because of the PEG coating the drug release from the nanoparticle formulations will be slow and sustained. Hence, to define the kinetics and response of drug release, the DOC-FOL-PEG-ZnO, CIS-FOL-PEG-ZnO and DUAL-FOL-PEG-ZnO was made with varying molar ratios (2:1, 1:1, and 1:2) of ZnO/PEG with activated-PEG concentrations of 0.25, 0.5 and 1 mM, correspondingly and was vacuum-packed in porous dialysis membranes. The drugs were released into 50 mL of Milli-Q water at 37 °C. The released drugs along with the medium were removed at various time intervals with immediate renewal of the media. The fraction of drugs released was directly calculated from the absorbance at 254 nm aided by a UV-Visspectrophotometer (UV-9200).The entire in-vitro release of drugs was carried out in two different pH of 4.5 and 7.4 corresponding to tumor microenvironment and normal physiological condition respectively.
Tunable nonenzymatic degradability of N-substituted polyaspartamide main chain by amine protonation and alkyl spacer length in side chains for enhanced messenger RNA transfection efficiency
Published in Science and Technology of Advanced Materials, 2019
Mitsuru Naito, Yuta Otsu, Rimpei Kamegawa, Kotaro Hayashi, Satoshi Uchida, Hyun Jin Kim, Kanjiro Miyata
The degradability of each PAsp(R) was evaluated by SEC analysis in physiological conditions (pH 7.4, 37 °C). The chromatogram obtained for PAsp(AE) for the 24 h incubation revealed the generation of low molecular weight fragments at around 13–19 mL in the elution volume (Figure 1(a)), demonstrating the nonenzymatic degradability of PAsp(AE). To clarify which of the amide bonds in the main or the side chains were cleaved, the PAsp(AE) sample was further incubated for 72 h under the physiological condition and was analyzed by SEC and 1H NMR. The SEC chart reveals that after the 72 h incubation, PAsp(AE) generated even lower molecular weight fragments (15–19 mL in elution volume) (Figure S4(a)). This indicates that the degradation reaction was further progressed. Also, the 1H NMR spectrum displays only a slight peak derived from free EDA (δ = 3.4) for the PAsp(AE) sample even after extended incubation for 72 h (Figure S4(b)); the intensity ratio of this peak to those from the AE moiety (δ = 3.2 and 3.6) was calculated to be ~6%. These results indicate that few cleavage reactions occurred in the side-chain amide bonds of PAsp(AE). Therefore, we conclude that the degradability of PAsp(AE) under the physiological condition (pH 7.4, 37 °C) was mostly due to the cleavage of the amide bond in the main chain.