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991.
《Analytical letters》2012,45(5):790-806
Abstract A new absorbance-based enzymatic biosensor for determination of urea (in the range 0.01 to 6.7 mM) is described. Quantification using cresol red dye, immobilized in the nanofilm coatings assembled on alginate microspheres to immobilize the urease enzyme, has been accomplished using ratiometric absorbance measurements. The effect of salt concentration in polyelectrolyte nanofilms (on the stability of dye molecules) and buffer pH (on the enzyme stability) are reported. The results demonstrate excellent stability of sensing assay within alginate microspheres. Urea-sensing experiments demonstrate the potential to develop an optical urea sensor that is stable over a month. 相似文献
992.
《Analytical letters》2012,45(6):997-1011
ABSTRACT An optical urea biosensor was developed by immobilizing an urease enzyme layer on a thin ammonium-selective polymer membrane. The ammonium optical membrane utilized dichlorofluorescein octadecyl ester (DCFOE) as anionic chromophore and nonactin as neutral ionophore. The urease layer was coated on the top of the ammonium layer by gelatin entrapment combined with glutaradehyde cross-linking. Hydrolysis of urea catalyzed by urease produced ammonium ion, which was extracted into the-polymer film to form complexes with nonactin. A proton was released which resulted in a color change of the optical membrane due to charge neutrality principle. The biosensor 相似文献
993.
Dana Hayoun‐Neeman Nataly Korover Sharon Etzion Rivka Ofir Rachel G. Lichtenstein Smadar Cohen 《先进技术聚合物》2019,30(10):2493-2505
Engineering human cardiac tissue is a promising solution for myocardial repair of injured hearts and for drug screening. Herein, we examined the capability of chemically defined alginate scaffolds to promote cardiac tissue regeneration from human embryonic stem cell‐derived cardiomyocytes (hESC‐CMs) in serum‐free, chemically defined medium. The cells were single seeded or coseeded with human dermal fibroblasts (HFs) in macroporous scaffolds made from pristine alginate or alginate modified with arginine‐glycine‐aspartate (RGD) peptide and heparin‐binding peptide (HBP). Our results show that the addition of fibroblasts to the 3‐D culture is indispensable for the formation of functional cardiac tissues and that the presence of RGD/HBP attached to the alginate matrix further improves its functionality. The engineered tissue displayed the typical fiber morphology with massive striation. An increase in contraction amplitude and calcium transients with time, together with a decrease in excitation threshold, indicated advancement toward tissue maturation. Our results thus point to the importance of co‐cultivating fibroblasts with hESCs‐CMs in chemically defined peptide‐functionalized alginate scaffolds and culture medium for regenerating functional cardiac tissue in vitro. 相似文献
994.
995.
An acylative Suzuki coupling of activated amides with aryl boronic acids has been reported via palladium-catalyzed CN bond cleavage. This protocol demonstrate amides can be activated by an atom-economic and cheap succinimide, which can be efficiently utilized to synthesize broad array of diaryl ketones in moderate to good yields. 相似文献
996.
Pratip Kumar Dutta Arpi Majumder Sanjay Dutta Basab Bijayi Dhar Parthapratim Munshi Subhabrata Sen 《Tetrahedron letters》2017,58(6):527-530
An efficient solvent free Pd(pCH2S)2dba catalyzed green-chemical strategy for the synthesis of diaryl disulfides from aryl thiols in moderate to excellent yield is reported. Variety of diaryl disulfides were synthesized. The catalyst is recyclable up to four cycles. 相似文献
997.
Nareerat Thongtham Poowadon Chai‐in Onuma Unger Suwimon Boonrungsiman Orawan Suwantong 《先进技术聚合物》2020,31(7):1496-1507
Here, we demonstrated the fabrication of a composite scaffold (chitosan [CS], collagen [Col], and hydroxyapatite [HA]) with the incorporation of encapsulated Cissus quadrangularis (CQ) extract for tissue engineering applications. First, the crude extract of CQ loaded nanoparticles were synthesized via double emulsion technique using polycaprolactone (PCL) and polyvinyl alcohol (PVA) as oil and aqueous phases, respectively. Both PCL (20, 40, and 80 mg/mL) and PVA (0.5%, 1%, and 3% w/v) concentrations were varied to determine the optimum concentrations for CQ‐loaded nanoparticle preparation. The CQ‐loaded PCL nanoparticles (CQ‐PCL NPs), prepared with 20 mg/mL PCL and 0.5% (w/v) PVA, exhibited the smallest size of 334.22 ± 43.21 nm with 95.54 ± 1.49% encapsulation efficiency. Then, the CQ‐PCL NPs were incorporated into the CS/Col/HA scaffolds. These scaffolds were also studied for their ultrastructure, pore sizes, chemical composition, compressive modulus, water swelling, weight loss, and biocompatibility. The results showed that the addition of CQ‐PCL NPs into the scaffolds did not dramatically alter the ultrastructure and properties of the scaffolds, compared to CS/Col/HA scaffolds alone. However, incorporation of CQ‐PCL NPs in the scaffolds improved the release profile of CQ by preventing the initial burst release and prolonging the release rate of CQ. In addition, the CQ‐PCL NPs‐loaded CS/Col/HA scaffolds supported the attachment and proliferation of MC3T3‐E1 osteoblast cells. 相似文献
998.
Xin He Song Jin Licheng Miao Yichao Cai Yunpeng Hou Haixia Li Kai Zhang Zhenhua Yan Jun Chen 《Angewandte Chemie (International ed. in English)》2020,59(38):16705-16711
Sodium metal is a promising anode, but uneven Na deposition with a dendrite growth seriously impedes its application. Herein, a fibrous hydroxylated MXene/carbon nanotubes (h‐Ti3C2/CNTs) composite is designed as a scaffold for dendrite‐free Na metal electrodes. This composite displays fast Na+/electron transport kinetics and good thermal conductivity and mechanical properties. The h‐Ti3C2 contains abundant sodiophilic functional groups, which play a significant role in inducing homogeneous nucleation of Na. Meanwhile, CNTs provide high tensile strength and ease of film‐forming. As a result, h‐Ti3C2/CNTs exhibit a high average Coulombic efficiency of 99.2 % and no dendrite after 1000 cycles. The h‐Ti3C2/CNTs/Na based symmetric cells show a long lifespan over 4000 h at 1.0 mA cm?2 with a capacity of 1.0 mAh cm?2. Furthermore, Na‐O2 batteries with a h‐Ti3C2/CNTs/Na anode exhibit a low potential gap of 0.11 V after an initial 70 cycles. 相似文献
999.
The aim of the present study is to investigate the urea-induced denaturation of bovine serum albumin. The native and denatured bovine serum albumin interactions with 32π-Norcorrole were investigated, respectively. The circular dichroism spectra indicated that the α-helix content of bovine serum albumin reduces in the presence of urea and 32π-Norcorrole. The Stern–Volmer quenching constant indicated that both dynamic and static quenching exist in the interaction; moreover, the denaturation of bovine serum albumin leads to the decrease of Stern–Volmer quenching constant. Binding constant illustrated that the native bovine serum albumin has stronger combination capacity than the denatured bovine serum albumin. The fluorescence lifetime studies demonstrated that denaturation lead to the fluorescence decay of bovine serum albumin. The binding sites experiment and molecular docking studies demonstrated that the binding site of 32π-Norcorrole on bovine serum albumin is mainly located in site I. 相似文献
1000.