新型骨支架复合材料修复牙槽骨缺损研究

目的:探讨多孔聚丙烯晴基碳纤维/壳聚糖/双相磷酸钙/聚乳酸-羟基乙酸(PAN/CS/BCP/PLGA)复合支架对大白兔牙槽骨缺损的修复能力。方法:采用真空冷冻干燥技术制备多孔PAN/CS/BCP/PLGA复合支架。选取32只成年雄性新西兰大白兔,随机分为实验组和对照组,手术制备大小为10mm×10mm×10mm牙槽骨缺损区。实验组骨缺损区植入PAN/CS/BCP/PLGA复合支架,对照组植入CS/PLGA复合材料,术后2、4、8、12周分期取材,进行X线检查、组织学观察、扫描电镜(SEM)检测和成骨细胞计数分析。结果:术后12周实验组检测结果,X线观察:骨缺损区阻射影与自体骨相同。组织学观察:骨缺损区完全被新骨充填,且为较成熟的板层骨,与自体骨完全融合。SEM检测:骨-材料界面形成骨性结合,移植材料大部分降解,被成熟骨组织替代。成骨细胞计数分析:成骨细胞生长活跃,统计学有显著性差异。结论:多孔PAN/CS/BCP/PLGA复合支架具备良好的生物活性和生物可降解性,对骨缺损的修复能力要优于CS/PLGA复合材料,为其成为骨组织工程支架替代材料提供理论依据。     

Does chlorhexidine in different formulations interfere with the force of orthodontic elastics

Objective:To evaluate the effects of different concentrations of chlorhexidine on the decline in force of orthodontic elastics.Materials and Methods:In a laboratory study, five groups of samples were tested, with one control group represented by distilled water (group 1) and four experimental groups: 0.12% manipulated chlorhexidine (group 2), 0.2% manipulated chlorhexidine (group 3), 0.12% chlorhexidine gluconate–based oral solution (0.12% Periogard; group 4), and 0.2% Cleanform mouthwash (formula and action; group 5). The test groups were submersed in artificial saliva at 37°C. Templates were used and submerged in the chlorhexidine solutions for 30 seconds twice a day. Force was measured with a digital dynamometer at six different time intervals: 0, 1, 7, 14, 21, and 28 days.Results:No statistical differences were found among the groups in the initial period, at 24 hours, and at 7 days (P > .05). There were statistical differences between groups 2 and 5 at 14 days of the experiment and between group 1 and the others at 28 days. In the initial period, the force was statistically higher than it was at any of the other periods of the experiment (P < .05).Conclusion:In the present study, chlorhexidine showed no significant influence on the force degradation of the chain elastics tested.     

Oral gram-positive bacterial DNA-based identification of saliva from highly degraded samples

Analyzing degraded evidence is an important challenge in forensic casework. Saliva remaining at a crime scene may deteriorate, due to various factors, making it difficult to identify. This study aims to clarify the efficacy of oral gram-positive and -negative bacterial DNA-based identification of saliva for analyzing highly degraded samples. Saliva samples were subjected to three different degradation treatments (heat denaturation: 40–80 °C in wet conditions; microbial decomposition: 1–5 days in humid soil; and ultraviolet (UV) irradiation: 0.01–1 J/cm²). We compared saliva markers’ detectability from the degraded samples—oral gram-positive bacterial DNA (Streptococcus salivarius and Streptococcus oralis), oral gram-negative bacterial DNA (Veillonella atypica and Prevotella maculosa) and salivary α-amylase. Oral bacterial DNA was detected using a melting curve analysis following real-time PCR. The efficacy of short tandem repeats (STR) and mitochondrial DNA (mtDNA) analyses were also compared. All oral bacterial DNA were detected with specific melting peaks from the heat-denatured samples, while neither catalytic nor immunochromatographic tests detected salivary α-amylase from the heat (80 °C) samples. The gram-positive bacterial DNA (S. salivarius and S. oralis) was detected from the microbial degradation (1–5 days) samples. In contrast, the gram-negative bacterial DNA (V. atypica and P. maculosa) and salivary α-amylase were not detected from samples treated for more than two days. UV exposure made bacterial DNA-based saliva identification difficult in a dose–dependent manner; however, UV irradiation did not influence protein-based saliva tests using salivary α-amylase as an indicator. As a result of STR and mtDNA typing, partial or null STR profiles were generated from the severely degraded (microbial (2–5 days) and UV (0.1–1 J/cm²) degradation) samples, but full mtDNA profiles were obtained from all degraded samples. The forensic applicability of bacterial DNA test evaluated, using mock case samples, indicates that the oral gram-positive bacterial DNA was more resistant to degradation than the other markers. We conclude that the oral gram-positive bacterial DNA-based examination could be useful for identifying saliva from severely environmentally-exposed forensic samples as well as mtDNA typing.     

Nerve regeneration and elastin formation within poly(glycerol sebacate)-based synthetic arterial grafts one-year post-implantation in a rat model

The objective of this study was to evaluate the long-term performance of cell-free vascular grafts made from a fast-degrading elastic polymer. We fabricated small arterial grafts from microporous tubes of poly(glycerol sebacate) (PGS) reinforced with polycaprolactone (PCL) nanofibers on the outer surface. Grafts were interpositioned in rat abdominal aortas and characterized at 1 year post-implant. Grafts remodeled into “neoarteries” (regenerated arteries) with similar gross appearance to native rat aortas. Neoarteries mimic arterial tissue architecture with a confluent endothelium and media and adventita-like layers. Patent vessels (80%) showed no significant stenosis, dilation, or calcification. Neoarteries contain nerves and have the same amount of mature elastin as native arteries. Despite some differences in matrix organization, regenerated arteries had similar dynamic mechanical compliance to native arteries in vivo. Neoarteries responded to vasomotor agents, albeit with different magnitude than native aortas. These data suggest that an elastic vascular graft that resorbs quickly has potential to improve the performance of vascular grafts used in small arteries. This design may also promote constructive remodeling in other soft tissues.     

Resisting protein adsorption on biodegradable polyester brushes

The protein adsorption and degradation behaviors of poly(lactic acid), poly(glycolic acid) (PGA) and poly(ε-caprolactone) (PCL) brushes and their co-polymer brushes with oligo(ethylene glycol) (OEG) were studied. Both brush structure and relative amount of OEG and polyester were found to be important to the protein resistance of the brushes. A protein-resisting surface can be fabricated either by using OEG as the top layer of a copolymer brush or by increasing the amount of OEG relative to polyester when using a hydroxyl terminated OEG (OEG-OH) and a methoxy terminated OEG (OEG-OMe) mixture as the substrate layer. The degradation of single polyester brushes and their co-polymer brushes using OEG-OH as a substrate layer or using OEG as a top layer was hindered. This phenomenon was rationalized by the inhibition of the proposed back-biting process as the hydroxy end groups of polyester were blocked by OEG molecules. Among these brushes tested, PGA co-polymer brushes using the methoxy/hydroxyl OEG mixture as the substrate layer proved to be both protein-resistant and degradable due to the relatively large amount of OEG moieties and the good biodegradability of PGA.     

盐酸青藤碱水溶液的降解动力学研究

目的:研究盐酸青藤碱水溶液的降解动力学特征。方法:应用比色法确定盐酸青藤碱在不同pH值、不同离子强度、不同介电常数水溶液中经80℃恒温加速试验所得的降解动力学参数。结果:经过线性拟合对比分析,盐酸青藤碱水溶液的降解反应级数为n=1。降解速率常数(k)值随pH值的上升而增高,在pH<3的低pH值区域降解十分缓慢;而进入pH3.9～5的区域趋于稳定,出现一个较低的平台;当pH>5时,k值随pH值的上升而迅速增高。盐酸青藤碱水溶液随离子强度的增加,降解速率增加;溶液的介电常数增加,其降解速率也增加。结论:盐酸青藤碱水溶液的降解属于近似1级动力学过程,降解速率受溶液pH影响显著;降解速率与溶液离子强度成正相关,与溶液介电常数亦成正相关。     

LC-MS-MS法分析伏立康唑的碱降解产物

目的:建立以液相色谱-串联质谱法快速分析伏立康唑的碱降解产物的方法。方法:借助色谱-串联质谱技术,比较并分析伏立康唑对照品和其碱降解产物的相对分子质量、碎片、光谱特征等信息。结果:伏立康唑与其降解产物能有效分离,2个主要降解产物分别为去4-乙基-5-氟嘧啶的同分异构体。结论:该方法快速、灵敏、专属性强,可用于推测伏立康唑降解产物的结构。     

Biodegradation and biocompatibility of polyorganophosphazene

We investigated biodegradation and biocompatibility of poly(organophosphazenes). We prepared poly(organophosphazenes) having different side chain groups. The blood compatibility of poly(organophosphazenes) containing fluorinated side groups, poly(bis[trifluoroethoxy]phosphazene) (PbFP) and poly([trifluoroethoxy][ethyl glycinate]phosphazene) (PFGP), without heparinization were evaluated in vitro. The deformation and aggregation of platelets adhered on PbFP and PFGP were not observed and they suppressed platelet activation. Additionally, PbFP and PFGP showed a higher degradation rate, despite their high hydrophobic nature. We found that the high mobility of water in PbFP and PFGP was one of the important factors facilitating their degradation. Their polymer structures were formed in a more open nature, indicating that water easily attacked the backbone of the phosphorus and nitrogen atoms in the poly(organophosphazene). On the other hand, the proliferation of HeLa cells cultured on poly(organophosphazene) was reduced compared with that on the control tissue culture polystyrene.     

Development of a stable solution of 5-aminolaevulinic acid for intracutaneous injection in photodynamic therapy

. Photodynamic therapy using 5-aminolaevulinic acid (ALA) as a photosensitiser is a new treatment modality for basal cell carcinomas. Until now ALA has been used topically as a cream. As this administration route leads sometimes to insufficient penetration in the skin, an intracutaneously injectable solution of ALA was developed. The influence of pH, concentration and temperature on the degradation of ALA in aqueous solution was investigated in order to optimise the formulation of the injection. In 0.1% ALA solutions with pH values between 4 and 8 a pH dependency of ALA degradation was shown, comprising fast decomposition at pH values higher than 7, whereas at a pH value of 6 or lower the solutions remained within the range of 90–110% of the initial concentration for at least 128 days. An increase of degradation rate with increasing concentrations became evident which is consistent with the supposed second-order degradation kinetics. After accelerated stability research at 63°C and 85°C a shelf life of 281 days for a 0.1% ALA solution pH 5 was calculated from an Arrhenius plot. A 2% ALA solution was proven to be isotonic. From our results a 0.1–2% ALA solution with pH 5 and an appropriate amount of sodium chloride to obtain isotonicity is recommended as an injectable solution. Paper received 3 January 2002; accepted after revision 11 January 2002.     

盐酸哌仑西平在水溶液中的降解动力学

目的:研究盐酸哌仑西平(pirenzepine hydrochloride,PRZ)在水溶液中的降解动力学.方法:采用经典恒温法进行试验,通过高效液相色谱法(HPLC法)检测PRZ的浓度.结果:PRZ在水溶液中的水解为伪一级动力学反应,同时受H 和OH-催化,酸催化速率常数(K1)为0.595 h-1*mol-1*L,碱催化速率常数(K2)为4.67×103 h-1*mol-1*L,K2是K1的7 849倍,表明PRZ在水溶液中主要受OH-催化水解.PRZ在水溶液中的最稳定pH(pHm)为5.1.PRZ在pH 1.1、pH 5.1、pH 7.0和pH 10.0(I=0.3)的水解反应活化能(Ea)分别是72.83、105.10、74.33和71.67(KJ/mol),在室温(25 ℃)下的有效期(t0.9)分别为13.1,783.6,58.2和0.7 d;在pH 1.1的水溶液中PRZ表观水解速率常数随离子强度(I)的增加而增大;相反,在pH 7.9的水溶液中,PRZ表观水解速率常数随离子强度增加而降低.结论:PRZ在强酸和强碱条件下均不稳定,若制成液体制剂可调pH为5.1左右.