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Carboxylesterase Inhibitors: Relevance for Pharmaceutical Applications
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2019
Notably, several mammalian CES, especially CES1, display transesterification activities. When alcohol presents in the CES1 reaction system, alcohol replaces water to attack the acyl-enzyme intermediate to generate an ethyl ester product. One of the well-studied examples of this reaction is the formation of cocaethylene in individuals abusing both cocaine and alcohol (Brzezinski et al., 1994; Beckemeier and Bora, 1998; Parker and Laizure, 2010). Under these conditions, the ethyl group from ethanol replaces the methyl group of cocaine to produce a more toxic metabolite cocaethylene. Furthermore, CES1 can process the creation of cholesteryl esters from cholesterol and fatty acids, as well as to generate fatty acid ethyl esters (FAEEs) from fatty acyl-Coenzyme A (CoA) and ethanol, using transesterification reaction (Brzezinski et al., 1994; Bora et al., 1996; Beckemeier and Bora, 1998; Tang et al., 2006). Since CES have cholesteryl esters hydrolysis and FAEE hydrolysis activity, the formation of these endogenous esters is the result of the balance between classic hydrolysis reaction and transesterification reaction.
Lipid Nanoparticles Based on Liquid Crystalline Phases
Published in Vladimir Torchilin, Mansoor M Amiji, Handbook of Materials for Nanomedicine, 2011
Many cholesterol esters are physiological lipids forming thermotropic mesophases due to their strongly anisometric, rod-like molecule shape.84 Physiologically, cholesterol esters present the storage and transport form of cholesterol and occur in lipoproteins. Particularly low density lipoproteins (LDL) contain high amounts of cholesterol ester (Table 10.2). LDL show a liquid crystalline-isotropic liquid phase transition between about 15 and 36°C87,88 and, interestingly, a nearly cylindrical shape was observed for isolated LDL particles when the samples were prepared at room temperature or below.89–91 As many tumors exhibit a high density of LDL receptors due to their high demand of cholesterol,92–94 isolated as well as protein-free model LDL are intensively studied as drug carrier systems in cancer chemotherapy.94,95 A variety of different antineoplastic drugs were incorporated into isolated LDL and protein-free LDL-like emulsions (LDE, composed of cholesteryl oleate, lecithin, triolein and cholesterol) and studied in different tumor cell lines as well as in vivo in animals and humans.96–106 Often, lipophilic prodrugs were loaded into LDL and LDL-like particles to assure a tight association of the drug with the carrier.98,103–106 LDL and their protein-free models are, however, in an isotropic liquid state at body temperature.
Preparation and characterisation of liquid crystal elastomer films with selective reflectivity
Published in Liquid Crystals, 2023
Tianyu Xing, Bo Jiao, Xin-Yi Wan, Yuan-Yuan Gao, Danshu Yao, Mei Tian
By grafting 4-allyloxybenzoic acid cholesteryl ester (MB) and a flexible cross-linker (MG) onto polymethyl hydrosiloxane (A’, n = 35), a series of side-chain LCE films (A’BG-1, A’BG-2 and A’BG-3) have been synthesised. The LCEs are cholesteric LCEs. And Tg is from 16.4°C to 40.8°C, which is mainly affected by the MB rigidity. A’BG series films display shape memory properties near room temperature. The thermal stability of the LCEs is high, the temperature of weight loss 5% is above 300°C. The decomposition of the LCEs experienced two rapid decomposition processes. The first rapid decomposition is caused by the shedding of the -COOChol structure in MB and the remaining structure after the second rapid decomposition is mainly the siloxane skeleton. The results of UV-vis analysis show that with the decreasing content of the cross-linker in the elastomer, A’BG-3 displays the selective reflection in the visible region, and the wavelength reflected occurs blue shift with increasing the temperature.
Spontaneous polarisation due to flexoelectric effect in liquid crystalline elastomers prepared by cross-linking under splay distortion
Published in Liquid Crystals, 2022
Kazuyuki Hiraoka, Toshio Ishihara, Hiroyuki Minami, Shiori Taira, Seiryu Komesu, Katsumi Yamada
An elastomer was synthesised by a hydrosilylation reaction of liquid crystalline side groups with a polysiloxane backbone using the well-known synthesis route [1]. Polymethyl-hydrosiloxane (polymerisation degree of 25–35), undecylenic acid cholesteryl ester and undecylenic acid 4-undec-10-enoyloxy-phenyl ester were used as the polymer backbone, mesogenic monomer and cross-linker, respectively. Their chemical structures are shown in Figure 1(a). As described in some detail later, it is noteworthy that the cholesterol-derived mesogen seems to be a wedge-shaped molecule, which enhances the emergence of the flexoelectric effect under splay distortion [19,20]. The elastomer exhibited the following phase sequence [g 25 SmA* 125 I (in °C)] upon heating. As already reported, these transition temperatures were determined by differential scanning calorimetry (DSC), thermomechanical analysis (TMA) and temperature-dependent X-ray diffractometry [27,28].
A novel thermoresponsive membrane as potential material for tissue engineering
Published in Liquid Crystals, 2021
Na Li, Zexiang Zheng, Xiang Cai, Qiao Liu, Yifan Zhang, Changren Zhou, Lihua Li, Yaowu Zhao
These results indicated that TCLC/PU favoured cell spreading and promoted cell-material interactions compared with the PU matrix. Previous analysis revealed that the combination of PU and LC can simulate the natural ECM to generate a soft elastic response that modulates the behaviours of cells [39]. However, the mechanism and the differences between different liquid crystal substrates still need to be studied in more detail. Our previous study also showed the excellent hemocompatibility of COC, but the interaction between COC and cells was unclear [34]. On the other hand, the fluidity and cholesteryl ester compound of the liquid crystals may be the factor causing cellular affinity because it can promote sensitivity in sensing cell contractions and enhance the physical properties of cells during attachment and proliferation [40,41]. In summary, it is necessary to discuss the physicochemical properties and intercellular interactions of TCLC in this study. Compared to pristine membranes, the uniform distribution of TCLC and its particular characteristics as well as the formation of liquid crystal domains of the TCLC/PU membranes might have provided a platform for enhanced biochemical interaction with cells [42,43]. Under physiological conditions, continuous liquid crystal domains, similar to the lipid bilayer structure of the molecule, were formed and contacted cells directly, which may be the key factor to improve the cell affinity and biocompatibility of the membrane.