Poly(lactic acid)-aspirin microspheres prepared via the traditional and improved solvent evaporation methods and its application performances

Drug-loaded microspheres are significant for the development of modern pharmaceutical products. It is well known that the taken of aspirin for long-term increases the risk of serious gastrointestinal complications, therefore a controllable delivery of aspirin is of importance to lighten those side effects. In this work, poly(lactic acid)(PLA) was chosen as the carrier to prepare PLA-aspirin microspheres by using the traditional and the improved solvent evaporation methods. It was found that no matter which experimental condition was, the encapsulation efficiency of aspirin was higher by using the improved method than that of the traditional method. Specifically, when the concentration of polyvinyl alcohol = 1%(mass),the polymer concentration = 1:20, the oil/water rate = 1:2.5, PLA-aspirin microspheres were obtained via the improved method with a high yield of 82.83%(mass) and an encapsulation efficiency of 44.09%. PLAaspirin microspheres were then prepared continuously using the improved method, which further enhanced the encapsulation efficiency to 54.56%. Approximate 85% aspirin released from microspheres within 7 days. Obvious degradation which was represented by reduction on hardness was observed by soaking microspheres in PBS for 60 days. This work is of interest because it provides a continuous route to prepare PLA-aspirin microspheres continuously with a high drug encapsulation efficiency.

Formation Mechanism of Heartwood and Research Status

The formation mechanism of heartwood is a scientific problem which has not been fully revealed in wood science.Effective regulation of heartwood formation is a scientific problem that is rarely studied and has not yet achieved a breakthrough in the field of forest cultivation.It is very beneficial to regulate the chemical properties of wood and directional and efficient cultivation of trees by fully understanding the formation mechanism of heartwood.Based on the author s research and practice,the recent research progress on the formation mechanism and regulation technology of heartwood is summarized,especially the research on the heartwood formation of Hongmu species.

Routine nasogastric tube placement in patients with small esophageal perforation after endoscopic foreign body removal may be unnecessary:a propensity score matching analysis

Background:Nasogastric tube(NGT)placement is part of the post-operative management of upper gastrointestinal perforation,but its routine use in esophageal perforation(EP)caused by foreign bodies remains unclear.The purpose of this research was to investigate the necessity for routine NGT placement in patients with EP after endoscopic foreign body removal.Methods:A total of 323 patients diagnosed with EP caused by foreign bodies at the First Affiliated Hospital of Nanchang University between January 2012 and December 2021 were included in this retrospective study.Patients were divided into the NGT group and the non-NGT group according to whether or not NGT placement was performed.The perforation healing rate,post-operative adverse events,hospital stay,and death rate were analysed using a 1:1 propensity score matching model.Results:Before matching,there were 263 patients in the NGT group and 60 patients in the non-NGT group.There were significant differences in the time to treatment,infection,albumin,and types of endoscopy between the two groups,while the length of hospital stay in the NGT group was significantly longer than that in the non-NGT group.After 1:1 propensity score matching,48 pairs of patients were matched between the two groups.The perforation healing rate,post-operative adverse events,length of hospital stay,and death rate did not show significant differences between the two groups.Conclusions:For patients with small EP caused by foreign bodies,routine NGT placement after endoscopic foreign body removal may be unnecessary.

Mineral Transition of Calcium Aluminate Clinker during High-Temperature Sintering with Low-lime Dosage

The mineral transition mechanism and physicochemical property of calcium aluminate clinker sintered at 1350 ℃ were systematically studied using analytical reagent α-Al_2O_3,CaCO_3 and SiO_2 when the molar ratio of CaO to Al_2O_3 is 1.0.The results show that the formation of Ca_2SiO_4 accelerates the diffusion of CaO and Al_2O_3,which promotes the formation of CaAl_2O_4 determined by dilatometer,X-ray diffraction,Fourier transform infrared spectroscopy and scanning electron microscopy methods.CaAl_4O_7,Ca_3Al_2O_6,Ca_3SiO_5 and Ca_2Al_2SiO_7 only exist in the initial stage of reactions,the amounts of which decrease with the increase of sintering duration.Ca_3Al_2O_6 and Ca_(12)Al_(14)O_(33) react with Al_2O_3 and CaAl_4O_7 to form CaAl_2O_4,while Ca_2Al_2SiO_7 reacts with CaO and Ca_(12)Al_(14)O_(33) to form Ca_2SiO_4 and CaAl_2O_4.The sintered clinker contains CaAl_2O_4 and γ-Ca_2SiO_4 as well as some Ca_(12)Al_(14)O_(33) when the sintering duration is longer than 1.0 h.The differential scanning calorimetry results reveal that Ca_2SiO_4,Ca_2Al_2SiO_7 and CaAl_2O_4 are formed at985 ℃,1045℃ and 1339 ℃,respectively.Increasing the sintering duration contributes to the transition of β-Ca_2SiO_4 to γ-Ca_2SiO_4,which improves the pulverization and alumina leaching property of the sintered clinker.