Effects on the crystallization behavior and biocompatibility of poly(LLA-ran-PDO-ran-GA) with poly(d-lactide) as nucleating agents

The blends of poly(l-lactide acid-p-dioxanone-glycolide) (PLPG) with poly(d-lactide) (PDLA) (PLPG/PDLA) were prepared by a solution-casting method. The effects of PDLA on the properties of the PLPG were studied. DSC and WAXD results confirmed that PLA stereocomplex (sc-PLA) crystals were formed by blending PLLA segments in PLPG with PDLA, and the melting endotherm for both PLLA and sc-PLA relied on PDLA content. The non-isothermal crystallization results indicated that the crystallization process was remarkably accelerated by the addition of PDLA. Meanwhile, the results of isothermal crystallization indicated that the half-time of crystallization decreased with the increase of PDLA content. Besides, the enzymatic degradation behavior of the samples showed that with the increase of PDLA content, the mass loss gradually decreased. Furthermore, TGA and DTG results indicated that the thermal degradation of the samples was a complex process. Moreover, the biocompatibility of the samples was tested by cell culture and using CCK-8 and live/dead staining. Results showed that the samples possessed lower cytotoxicity. Therefore, the PLPG/PDLA blends are promising candidate materials in biomedical applications.

Sc-PLA crystals in the PLPG/PDLA blends were formed by hydrogen bond between PDLA and PLLA segments, which enhance the crystallization ability of PLLA in the PLPG matrix by decreasing the activation free energy.     

村边草垛周围鼠类分布调查

1984年秋季在临沭县调查了杨楼村村边草垛周围鼠类的分布情况‘其鼠密度和黑线姬鼠密度均明显高于野外(P<0.01),黑线姬鼠为优势种,占捕获总数的81.82％。在秋冬季节的灭鼠防病工作中,重点做好村周灭鼠,对于降低黑线姬鼠密度,预防流行性出血热的发生具有一定的作用。     

The Enamel Microstructures of Bovine Mandibular Incisors

Bovine teeth have been considered as an excellent substitute for human teeth for dental research, however, the enamel microstructures of bovine incisors that include arrangements of prisms and interprisms, and their spatial relationships have not been well described. The aim of this study was to investigate the detail enamel microstructures of bovine incisors. Eight bovine mandibular incisors were cut into 77 pieces at eight equal intervals either in the longitudinal direction or in the horizontal direction before each piece had been tangentially cut (parallel to enamel–dentin junction) through the middle of the enamel thickness. All the sectioned surfaces were treated 1 M HCl for 10 sec to expose the prisms and interprisms before observation by scanning electron microscopy. The parallel enamel prisms were located in all the outer enamel, the cervical region and the incisal ridge of the bovine incisors. Most labial inner enamel and the cingulum of lingual inner enamel were composed of the Hunter–Schreger bands with the characteristics of decussating groups of prisms and decussating planes between interprisms and prisms. The interprisms were thicker in the inner enamel than in the outer enamel. Anat Rec, 2012. © 2012 Wiley Periodicals, Inc.     

椎间孔镜下腰椎间盘髓核摘除治疗腰椎间盘突出症的生物力学优势

文题释义：腰椎间盘突出症的手术治疗：腰椎间盘突出症是脊柱外科常见病,手术方式较多。近年来,经皮椎间孔镜腰椎间盘髓核摘除术作为微创治疗方法迅速发展,具有创伤小、出血量少并能快速康复的优点,受到越来越多的关注。 背景：腰椎间盘突出症的手术方式较多,各有优缺点,通过有限元分析方法进行脊柱生物力学研究可以指导临床工作。 目的：建立L_3-5三维有限元模型,分析不同术式在椎间盘摘除后对脊柱力学的影响。方法：选择1名无腰椎病史的35岁男性志愿者,收集腰椎CT数据构建有限元模型并验证。在L₃/L₅脊柱正常模型(模型Ⅰ)的基础上建立L_4/5节段单纯开窗髓核摘除模型(模型Ⅱ)、椎间盘镜手术模型(模型Ⅲ)、经皮椎间孔镜腰椎间盘髓核摘除模型(模型Ⅳ)、关节突关节切除模型(模型Ⅴ),在7种加载工况下测定L₄/L₅节段椎体、椎间盘和左右关节软骨应力分布及L₄椎体位移。 结果与结论：①建立的三维有限元模型有效,方差分析模型有效;②L_4-5椎间盘两两比较后模型Ⅲ、Ⅳ在椎间盘应力集中最小;L₄椎体应力,模型Ⅳ对椎体影响最小;L₄椎体位移,模型Ⅲ和Ⅳ对椎体稳定影响最小;③从加载方式看,关节突关节损伤越小,椎间盘应力越小,模型Ⅳ最小;左侧关节突模型Ⅲ和Ⅳ均保持关节完整;右侧关节左右旋转加载下手术侧关节越完整,应力越大,故模型Ⅳ较大;左右侧倾加载下反而相反,模型Ⅴ最大;L₄椎体应力模型Ⅳ最小;椎体位移,模型Ⅲ和Ⅳ位移最小,接近模型Ⅰ;④提示经皮椎间孔镜腰椎间盘髓核摘除模型在椎体、椎间盘和关节突关节应力分布最小,有明显优势;椎间盘镜手术模型和经皮椎间孔镜腰椎间盘髓核摘除模型位移均较其他手术模型稳定,二者无差异;故经皮椎间孔镜腰椎间盘髓核摘除目前是较理想的术式。　 ORCID: 0000-0002-2604-0049(吐尔洪江·阿布都热西提) 中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程     

PLLA‐Grafted Gelatin Amphiphilic Copolymer and Its Self‐Assembled Nano Carrier for Anticancer Drug Delivery

A series of poly(l ‐lactide)‐grafted gelatin (Gel‐g‐PLLA) copolymers are synthesized by coupling the amino groups of gelatin with different molar masses and the carboxyl endgroup of poly(l ‐lactide) in the presence of 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide hydrochloride and N‐hydroxysuccinimide. Fourier transform infrared and nuclear magnetic resonance (¹H NMR) data confirm the successful bonding between gelatin and PLLA. Self‐assembled micelles of copolymers are prepared by using the direct dissolution method. The size and micellar morphology are determined from dynamic light scattering as well as transmission electron microscopy measurements. Meanwhile, in vitro drug release reveals that Gel‐g‐PLLA micelles show excellent sustained‐release properties when used as the carrier of the anticancer drug paclitaxel. A burst release of about 70% is observed in the first 24 h. All these features, together with the outstanding biocompatibility, make Gel‐g‐PLLA micelles a promising drug carrier for cancer therapy.     

Surface Modification of PTLG Terpolymer Using PNIPAAm and Its Cell Adhesion/Detachment Behavior

Novel biodegradable terpolymer poly (1,3‐trimethylene carbonate‐b‐(l ‐lactide‐r‐glycolide)) grafted with poly(N‐isopropylacrylamide) (PTLG‐PNIPAAm) is prepared by plasma‐induced polymerization. The experimental results show that PNIPAAm segments of samples have a dramatic effect on surface layer structure and cell behavior of PTLG‐PNIPAAm. The thickness of PNIPAAm layer on PTLG surface increases rapidly from 50 nm to 1 µm with the molecular weight of samples increasing. Cell toxicity analysis indicates that PTLG‐PNIPAAm possesses good cytocompatibility to human adipose‐derived stem cells (hADSCs). For cell adhesion and detachment process on modified surface, the “hook and loop” process is proposed to understand the cell adhesion on modified surface with coiled conformation PNIPAAm segments at 37 °C, and then the cell sheet detached from surface spontaneously due to the conformation of PNIPAAm segments extends below its lower critical solution temperature. The research demonstrates that with increasing thickness of the PNIPAAm layer on PTLG surface, the hADSCs with well cell viability presents rapider thermal‐responsive detachment behavior. Therefore, the surface modification of biodegradable PTLG with stimuli‐sensitive functional PNIPAAm is an efficacious route for further application in stem cell culture and tissue engineering stent.