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Items 3021 to 3023 of 3023 total

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  • Design of Molecularly Imprinted Polymeric Materials: The Crucial Choice of Functional Monomers

    Anene, A; Kalfat, R; Chevalier, Y; Hbaieb, S
    Laboratoire Matériaux, Traitement et Analyse, Institut National de Recherche et d’Analyse Physico-Chimique, Biotechpole Sidi-Thabet, 2020 Ariana, Tunisia
    Product(s): Patulin
    The consequences of such findings on the selectivity of adsorption of the MIPs are interesting since they contradict in some aspects the first intuitive ideas. The selectivity discussed in the present work refers to a comparison between the binding behavior of the target molecule to MIPs and NIPs. In this framework, selectivity comes from an excess number of binding sites in the MIPs. Let us notice that some authors based their discussion on selectivity defined as the differential binding of the target and interfering molecules, which is a different concept of selectivity. The higher selectivity for patulin uptake of Sil-MA/MIP compared to Sil-MAA/MIP comes from a higher density of selective binding sites. However, both the amount of grafted polymer material and the fraction of functional monomer in the grafted copolymers were larger for Sil-MAA/MIP. The much larger density of acidic sites in Sil-MAA/MIP did not yield a larger excess binding of patulin with respect to the NIP. The key difference between Sil-MA/MIP and Sil-MAA/MIP is the composition of the copolymer that sets the cross-linking density. A high cross-linking density is required for quenching the acidic sites oriented towards the template in such a way that their position is retained after elimination of the template for keeping maximum interactions with the target molecules. A high cross-linking density comes from a large EGDMA fraction in the copolymer composition, therefore, a low content of functional monomer. It might be considered that high cross-linking is at the expense of the density of binding sites. The present work shows that such poor density is largely compensated by the effects of the higher cross-linking density that prevent the loss of specific binding site when the material is too soft or when the functional monomers are incorporated into flexible polymer segments in between cross-links. Accordingly, the reactivity ratios of MA are favorable, resulting in the formation of isolated MA units surrounded by two cross-links. It is also worth to point out that adsorption of the target molecules takes place at the surface of the materials. Therefore, it is not useful to have a large amount of polymer material bound to the solid support as a thick coating because most of the functional units would be buried inside the material and not accessible for adsorption. A low density of functional units is enough for the formation of a large surface density at the external surface of the materials. Sil-MAA/MIP was coated with a thick layer of polymer that filled the interstices in between the silica particles, resulting in a loss of specific area as measured by the BET method. On the contrary, Sil-MA/MIP retained a large specific area and the thin coating was highly cross-linked at the adsorption sites.
  • Generation Process and Performance Evaluation of Engineered Microsphere Agarose Adsorbent for Application in Fluidized-bed Systems

    Mofidian, R; Barati, A; Jahanshahi, M; Shahavi, MH;
    Department of Chemical Engineering, Faculty of Engineering, Arak University, Arak, Iran
    In this research, the generation process of engineered microsphere agarose adsorbent has been explained that has surfaces with different active sites to adsorb protein nanoparticles into the fluidized-bed system. Also, excellent selectivity of protein nanoparticles, high adsorption capacity, and fast equilibrium rate through the eco-friendly polymeric adsorbents were vital aims in here. Hence, agarose as a cheap, and abundant natural polymer, with a ferromagnetic condenser, and dye-ligand adsorbents, were employed to generate the engineered microsphere agarose adsorbent. Then, the performance of produced adsorbents was evaluated in the batch and fluidized-bed system. Scanning electron microscopy, atomic force microscopy, and optical microscope were used. Results showed the shape of adsorbents is spherical, with the size distribution range of 50-250 µm, the porosity of around 90%, and the wet density of 2.6 g/mL. Then, to compare the performance of the engineered adsorbents in a fluidized-bed system, the dye ligand was immobilized on the Streamline™. The obtained results were compared at the same conditions. In batch adsorption tests, the results of lactoferrin nanoparticle adsorption were shown higher dynamic binding capacity with engineered microsphere agarose adsorbents. Also, the results demonstrated that more than 75% of the adsorption process occurred in the first half-hour, which is a very suitable time for a fluidized-bed system. Also, adsorption equilibrium data were evaluated with isothermal adsorption models, and Langmuir’s model suits the data, and the maximum of adsorption was close to 45.3 mg/mL adsorbent. The fluidized-bed adsorption tests showed that engineered adsorbents gained a sound breakthrough performance at high flow velocity and upper dynamic binding capacity compared to commercial adsorbents. The dynamic binding capacity at 10% breakthrough achieved 71% of the flooded adsorption process at the major fluid velocity of 348 cm/h, so the engineered adsorbent has been proved the good potential for use in high flow rate fluidized-bed systems. KEYWORDS
  • Microenvironmental changes induced by placenta-derived mesenchymal stem cells restore ovarian function in ovariectomized rats via activation of the PI3K-FOXO3 pathway

    Choi, JH; Seok, J; Lim, SM; Kim, TH; Kim, GJ
    Department of Oral Pathology, College of Dentistry, Gangneung-Wonju National University, Gangneung-si, 25457, Republic of Korea
    Background: Translational studies have explored the therapeutic potential and feasibility of mesenchymal stem cells (MSCs) in several degenerative diseases; however, mechanistic studies of the function of these cells have been insufficient. As ovarian failure causes anovulation as well as ovarian steroid hormonal imbalances, the specific aims of this study were to analyze the therapeutic role of placenta-derived MSCs (PD-MSCs) in an ovarian failure ovariectomy (OVX) rat model and evaluate whether PD-MSC transplantation (Tx) improved folliculogenesis and oocyte maturation in the injured ovary through PI3K/Akt and FOXO signaling. Methods: Blood and ovary tissue were collected and analyzed after various PD-MSC Tx treatments in an ovariectomized rat model. Changes in the expression of folliculogenesis- and ovary regeneration-related genes induced by PD-MSC treatments were analyzed by qRT-PCR, Western blotting, and histological analysis. Results: The levels of hormones related to ovary function were significantly increased in the PD-MSC Tx groups compared with those in the nontransplantation group (NTx). The follicle numbers in the ovarian tissues were increased along with increased expression of genes related to folliculogenesis in the PD-MSC Tx groups compared with NTx groups. Furthermore, Tx PD-MSCs induced follicle maturation by increasing the phosphorylation of GSK3 beta and FOXO3 (p

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