An online dual-enzyme co-immobilized microreactor based on capillary electrophoresis for enzyme kinetics assays and screening of dual-target inhibitors against thrombin and factor Xa

In this study, an online capillary electrophoresis (CE) based dual-enzyme (thrombin and factor Xa) co-immobilized microreactor (THR-FXa IMER) was constructed for studying enzyme kinetics and screening dual-target inhibitors against THR and FXa with the aid of the polydopamine/graphene oxide (PDA/GO) coating. Based on the developed THR-FXa IMER, the Michaelis-Menten constants (K_m) of THR and FXa were calculated to be 187.26 and 48.80 μM, respectively. The inhibition constants (K_i) for two known inhibitors, argatroban and rivaroxaban, on THR and FXa were determined to be 14.73 and 0.41 nM, respectively. In addition, after 30 consecutive runs, the enzymes' activity was remained 98% of the initial immobilized activity for both THR and FXa, which shows that the constructed IMER has good stability and repeatability. Finally, the developed method was successfully applied to screen dual-target inhibitors against THR and FXa from 30 small molecular compounds. Among them, 10 compounds such as salvianolic acid C and epigallocatechin gallate (EGCG) have dual-enzyme inhibitory activity, and 2 compounds named saikosaponin A and oleuropein have single THR inhibitory activity, 5 compounds such as rosemary acid and salvianolic acid B have single FXa inhibitory activity. Finally, the molecular interactions between enzyme and potential inhibitors were further verified via the molecular docking, and a new compound with a theoretically good coagulation inhibition effect was designed by the scaffold hopping study. In summary, the developed THR-FXa IMER is a reliable method for screening THR and/or FXa inhibitors.

Tissue-compatible and adhesive polyion complex hydrogels composed of amphiphilic phospholipid polymers

To investigate the tissue adhesive function of a hydrogel composed of biocompatible amphiphilic polymers, polymers with various architectures were prepared from 2-methacryloyloxyethyl phosphorylcholine (MPC), electrolyte monomers and hydrophobic n-butyl methacrylate (BMA). A polyion complex (PIC) hydrogel was formed within a few minutes after aqueous solutions containing the cationic and anionic MPC polymers were mixed. Provided the electrical charge of the cationic and anionic MPC polymers was approximately balanced, the PIC hydrogel existed stably in a large amount of aqueous medium. The results of the fluorescence study of the MPC polymers suggested that dissociation was suppressed and that the electrostatic interaction was enhanced in the block and graft polymers compared to the random polymers. This is due to the strategically designed architectures and the hydrophobic BMA units. Based on the results of the cytotoxicity test, the cytotoxicity of the MPC polymers was lower than that of glutaraldehyde, a cross-linker contained in aldehyde-type tissue adhesives. The cationic MPC polymers demonstrated higher cytotoxicity compared to the anionic ones, which demonstrated no significant cytotoxicity at examined concentrations. The tissue adhesion of the PIC hydrogels was evaluated with a dura incision model. The results indicated that the tissue adhesion strength of the PIC hydrogel was lower than that of a commercially available fibrin glue. However, the tissue adhesion strength increased with an increase in the polymer concentration and could be controlled by the water content of the hydrogel. Although further investigation of the biocompatibility of the PIC hydrogels and control of the water content is crucial, it can be concluded that the PIC hydrogels formed by the amphiphilic MPC polymers can be promising tissue adhesives which demonstrate properties according to the architectures and chemical structures.

Understanding the Mechanism of Gelation and Stimuli-Responsive Nature of a Class of Metallo-Supramolecular Gels

Utilizing metal-ligand binding as the driving force for self-assembly of a ditopic ligand, which consists of a 2,6-bis-(1'-methylbenzimidazolyl)-4-oxypyridine moiety attached to either end of a penta(ethylene glycol) core, in the presence of a transition metal ion (Zn(II)) and a lanthanide metal ion (La(III)), we have achieved formation of stimuli-responsive metallo-supramolecular gels. We describe herein a series of experimental studies, including optical and confocal microscopy, dynamic light scattering, wide-angle X-ray diffraction, and rheology, to explore the properties of such gels, as well as the nature of the gelation mechanism. Morphological and X-ray diffraction observations suggest gelation occurs via the flocculation of semicrystalline colloidal particles, which results in the gels exhibiting pronounced yielding and thixotropic behavior. Application of mechanical stress results in a decrease in the particle size, which is accompanied by an increase in gel strength after removal of the stress. Moreover, studies show that the presence of lanthanide(III) perchlorate increases the mechano-responsiveness of the gels, as a consequence of reduced crystallinity of the colloidal particles, presumably due to the different coordination ability of lanthanide(III) and zinc(II), which changes the nature of the self-assembly in these materials.