Multiscale modeling for the heterogeneous strength of biodegradable polyesters

A heterogeneous method of coupled multiscale strength model is presented in this paper for calculating the strength of medical polyesters such as polylactide (PLA), polyglycolide (PGA) and their copolymers during degradation by bulk erosion. The macroscopic device is discretized into an array of mesoscopic cells. A polymer chain is assumed to stay in one cell. With the polymer chain scission, it is found that the molecular weight, chain recrystallization induced by polymer chain scissions, and the cavities formation due to polymer cell collapse play different roles in the composition of mechanical strength of the polymer. Therefore, three types of strength phases were proposed to display the heterogeneous strength structures and to represent different strength contribution to polymers, which are amorphous phase, crystallinity phase and strength vacancy phase, respectively. The strength of the amorphous phase is related to the molecular weight; strength of the crystallinity phase is related to molecular weight and degree of crystallization; and the strength vacancy phase has negligible strength. The vacancy strength phase includes not only the cells with cavity status but also those with an amorphous status, but a molecular weight value below a threshold molecular weight. This heterogeneous strength model is coupled with micro chain scission, chain recrystallization and a macro oligomer diffusion equation to form a multiscale strength model which can simulate the strength phase evolution, cells status evolution, molecular weight, degree of crystallinity, weight loss and device strength during degradation. Different example cases are used to verify this model. The results demonstrate a good fit to experimental data

Synthesis and Biological Activities of a 3′-Azido Analogue of Doxorubicin Against Drug-Resistant Cancer Cells

Doxorubicin (DOX), an anthracycline antibiotic, is one of the most active anticancer chemotherapeutic agents. The clinical use of DOX, however, is limited by the dose-dependant P-glycoprotein (P-gp)-mediated resistance. Herein, a 3′-azido analogue of DOX (ADOX) was prepared from daunorubicin (DNR). ADOX exhibited potent antitumor activities in drug-sensitive (MCF-7 and K562) and drug-resistant cell lines (MCF-7/DNR, K562/DOX), respectively. The drug resistance index (DRI) values of ADOX were much lower than that of DOX. The cytotoxicity experiments of ADOX or DOX against K562/DOX, with or without P-gp inhibitor, indicated that ADOX circumvents resistance by abolishing the P-gp recognition. This conclusion was further supported by drug influx/efflux flow cytometry experiments, as well as by molecular docking of ADOX to P-gp. In vivo animal tests, ADOX exhibited higher activity and less toxicity than DOX. The current data warranted ADOX for additional pre-clinical evaluations for new drug development

Exometabolomic analysis of decidualizing human endometrial stromal and perivascular cells

Differentiation of endometrial fibroblasts into specialized decidual cells controls embryo implantation and transforms the cycling endometrium into a semi-permanent, immune-protective matrix that accommodates the placenta throughout pregnancy. This process starts during the midluteal phase of the menstrual cycle with decidual transformation of perivascular cells (PVC) surrounding the terminal spiral arterioles and endometrial stromal cells (EnSC) underlying the luminal epithelium. Decidualization involves extensive cellular reprogramming and acquisition of a secretory phenotype, essential for coordinated placental trophoblast invasion. Secreted metabolites are an emerging class of signalling molecules. Here, we used liquid chromatography-mass spectrometry to characterise the dynamic changes in metabolite secretion (exometabolome) of primary PVC and EnSC decidualized over 8 days. We identified 79 annotated metabolites differentially secreted upon decidualization, including prostaglandin, sphingolipid, and hyaluronic acid metabolites. Secreted metabolites encompassed 21 metabolic pathways, most prominently glycerolipid and pyrimidine metabolism. Although temporal exometabolome changes were comparable between decidualizing PVC and EnSC, 32 metabolites were differentially secreted across the decidualization time-course. Further, targeted metabolomics demonstrated a conspicuous difference in xanthine secretion between decidualized PVC and EnSC. Taken together, our findings indicate that the metabolic footprints generated by different decidual subpopulations encode spatiotemporal information that may be important for optimal embryo implantation

The Development and Application of the Acrylamide Kind Polymers for Tertiary Oil Recovery in China

 As many oilfields shift from high permeability and medium-high permeability to low permeability and ultra-low permeability, the complexity and specificity of their formation channels increase, and the requirements on injectivity and liquidity of polymer flooding become increasingly stricter. This paper, from the perspective of the molecular configuration of poly(acrylamide) (PAM), gives an introduction to their respective characteristics, and analyzes the applicability of PAMs in tertiary oil recovery on the basis of the applications of polymer flooding in China. The study suggests that, on the one hand, the problem that urgently needs to be solved at present is achieving the viscosification of polymers with medium-low molecular weight or low molecular weight in high-temperature and high-salt conditions; on the other hand, researchers shall change their original research thoughts, shift from large-scale design of original PAM products to one-to-one “customized” research on and development for meeting specific oilfield demands from the perspective of polymer molecular structure

Study on a Polymer Profile Control Agent with Controllable Swelling Time

 The study provided a microsphere profile control agent, which can smoothly go deep into the stratum by using the hydrophobic shell structure as the “protective film”. While the solution time in simulated brine was prolonged, water molecules went deep into the inside of the microsphere particles through the pore structure, and combined with hydrophilic groups. Because of the combination, the microsphere polymer started to swell, and opened the shell into long chain for days, and then at the end, its hydrophilic-hydrophobic block groups were all exposed in the solution, which resulted in self-thickening property. The dissolution time after entering into the stratum, i.e. the shell “rupture” time can be controlled by adjusting the carbon chains length of hydrophobic groups in the synthetic process. The agent can not only prolong the depth of plugging and provide a stable plugging rate, but also enlarge the water swept volume after dissolution. This method can stabilize the oil production and control the water cut. The function of delayed thickening ability makes the stratum sealed but kept at a certain permeability