BACKGROUND:Polylactic acid(PLA)surface is hydrophobic and there are no nataral recognition sites,so its application is limited.Many different strategies have been studied such as composition and chemical Drafting,to produce hydrophilic groups.However,these traditional methods are always involved in complex process and many organic reagents,resulting in decrease of biocompatibility.OBJECTIVE:To conduct the surfacr modification of PL.A and improve its hydrophilicity with low temperature plasma treatment.DESIGN:Controlled observation.SETTING:Department of Materials Science and Engineering in Jinan University.MATERIAIS:The experiment was processed from October 2004 to October 2005 at Guangzhou Research Center of Artificial Organs and Materials Engineering(Ministry of Education).The mainly used materials were:Poly-D,L-lactic acid(Mr 2.9×104,Shandong Medical Instrument Institute),N-vinyl-pyrrolidone(NVP,Acros Company,purified before use).METHODS:The materials were treated in the plasma reactor under different conditions(power=150 W,t=3,2,1 minutes;power=30 W,t=10,8,5,3,1 minutes)to choose the optimal condition,and then PLA were grafted with NVP by gas phase polymerization and liquid polymerization,respectively.MAIN OUTCOME MEASURES:THe surface morphology of the films was observed with scanning electron microscopy and atomic force microscopy.The hydrophilicity of native and treated material surfaces was measured using a water contact angle meter.Surface composition was detected with Fourier transform infrared spectrometer.Mass changesmeasurement was applied to characterize the grafting efficiency.RESULTS:Scanning electron microscopy and atomic force microscopy showed that the plasma medified materials possessed coarse surface with pores and notches.Water contact angles decreased obviously from 78°to 50°after grafting,Fourier transform infrared spectrometer showed a new absorption peak at 1 637.19 cm-1,which corresponded to the carbonyl stretch vibration absorption of amide group in poly-N-vinyl-pyrrolidone.After the plasma treatmerlt at low temperature.the mass change ratio of PLA film material was-0.6.CONCLUSION:The plasma treatment and polymerization can improve the hydrophilicity and cause coarsr surface of PLA material,which will be helpful for the cell attachment.

Objective To analyze the outcomes of catheter ablation for persistent atrial fibrillation(AF)and the independent risk factors for its recurrence in the elderly.Methods A total of 194 patients with persistent AF who underwent catheter ablation at our department from January 2019 to December 2021 were enrolled in this study.They were divided into elderly group(≥60 years old,99 cases)and non-elderly group(＜60 years old,95 cases).Their surgical characteris-tics,postoperative complications and recurrence were compared between the two groups,and the independent risk factors for postoperative recurrence were analyzed in the elderly group.Results Advanced age,higher B-type natriuretic peptide,larger proportions of hypertension and coronary heart disease,and increased CHA2DS2-VASc and HAS-BLED scores,while lower male ratio and estimated glomerular filtration rate were observed in the elderly group than the non-elderly group(P＜0.05,P＜0.01).The elderly group had a higher proportion of left atrial fibrosis than the non-elderly group(30.3％vs 8.4％,P=0.001).Postoperative complications in the elderly group in-cluded 1 case of pericardial effusion and 2 cases of hematoma at the puncture site,and all of these were improved after treatment.There were no significant differences in the 1-year success rate(71.7％vs 69.5％,P=0.763)or recurrence rate during blanking period(21.2％vs 21.1％,P=0.981)between the elderly and non-elderly groups.AF duration(HR=1.020,95％CI:1.007-1.032,P=0.002)and recurrence during blanking period(HR=6.781,95％CI:3.078-14.935,P=0.001)were independent risk factors for postoperative recurrence in the elderly group.Conclu-sion Catheter ablation is safe and effective in the treatment of persistent AF in the elderly.The elderly patients with long duration of AF and recurrences during blanking period are more likely to experience recurrences within 1 year after ablation.