Multi‐Responsive Bilayer Hydrogel Actuators with Programmable and Precisely Tunable Motions

Multi‐responsive hydrogel actuators show promising applications for soft robotics, biomedical engineering, and artificial muscles, but the uncontrollable nature of their motions poses a barrier to practical applications. Herein, a novel type of bilayer hydrogel actuators (BHAs) is presented comprising of a poly(N‐isopropylacrylamide) (PNIPAm) and a poly (N‐hydroxyethyl acrylamide) (PHEAm) hydrogel layer with various compositions, which demonstrate thermal‐responsive and novel solvent‐responsive actuation under water or within solvents. These BHAs exhibit a wide range of regulable bidirectional motions due to the simultaneous co‐nonsolvency property of PNIPAm and the shrinking behavior of PHEAm in ethanol/water mixtures with various ethanol contents. By adjusting the compositions of ethanol/water mixtures, the bending directions and amplitudes of BHAs are precisely regulable and the curvatures of actuators are tunable between ?0.34 and 0.3. Because of the temperature‐responsive character of PNIPAm, BHAs fulfilled thermal‐driven motions to lift items. By reinforcing PHEAm layers with cellulose nanocrystals (CNCs) or CNCs bearing methacylamide moieties on the surface, the weight‐lifting capability of BHAs is highly improved to 18 times the weight of their own polymer weights. This design concept with bilayer structures provides a new strategy for the construction of precisely regulable hydrogel actuators, which allows using solvents to exactly control their motions.     

A papain‐induced disc degeneration model for the assessment of thermo‐reversible hydrogel–cells therapeutic approach

Nucleus pulposus (NP) regeneration by the application of injectable cell‐embedded hydrogels is an appealing approach for tissue engineering. We investigated a thermo‐reversible hydrogel (TR‐HG), based on a modified polysaccharide with a thermo‐reversible polyamide [poly(N‐isopropylacrylamide), pNIPAM], which is made to behave as a liquid at room temperature and hardens at > 32 °C. In order to test the hydrogel, a papain‐induced bovine caudal disc degeneration model (PDDM), creating a cavity in the NP, was employed. Human mesenchymal stem cells (hMSCs) or autologous bovine NP cells (bNPCs) were seeded in TR‐HG; hMSCs were additionally preconditioned with rhGDF‐5 for 7 days. Then, TR‐HG was reversed to a fluid and the cell suspension injected into the PDDM and kept under static loading for 7 days. Experimental design was: (D1) fresh disc control + PBS injection; (D2) PDDM + PBS injection; (D3) PDDM + TR‐HG (material control); (D4) PDDM + TR‐HG + bNPCs; (D5) PDDM + TR‐HG + hMSCs. Magnetic resonance imaging performed before and after loading, on days 9 and 16, allowed imaging of the hydrogel‐filled PDDM and assessment of disc height and volume changes. In gel‐injected discs the NP region showed a major drop in volume and disc height during culture under static load. The RT–PCR results of injected hMSCs showed significant upregulation of ACAN, COL2A1, VCAN and SOX9 during culture in the disc cavity, whereas the gene expression profile of NP cells remained unchanged. The cell viability of injected cells (NPCs or hMSCs) was maintained at over 86% in 3D culture and dropped to ~72% after organ culture. Our results underline the need for load‐bearing hydrogels that are also cyto‐compatible. Copyright © 2013 John Wiley & Sons, Ltd.     

封闭负压吸引在腹部带蒂真皮下血管网皮瓣修复手部热压伤中的临床应用

目的探讨封闭负压吸引在腹部带蒂真皮下血管网皮瓣修复手热压伤的临床应用中,促进皮瓣与创面愈合的作用机制。方法选择42例手部严重热压伤患者行腹部带蒂真皮下血管网皮瓣修复创面,随机分成实验组和对照组,每组21例。实验组皮瓣转移后,在皮瓣下均匀放置3～6根硅胶管（直径0.2cm,带侧孔6～8个）,各管另一端穿出皮瓣两侧集中成一束,连接中心负压吸引（压力0.02～0.06MPa）,皮瓣边缘以医用粘贴手术巾封闭。对照组常规皮瓣转移缝合,皮瓣下放置1条橡皮引流条。两组术后,适当加压包扎创面,72小时拔出引流管（条）。术后第5天开始皮瓣蒂部阻断血运训练,皮瓣阻断1h以上无血运障碍后实施断蒂手术。观察两组皮瓣的成活率及断蒂时间,所获数据采用完全随机化设计法进行分析,组间比较分别采用χ2检验和t检验。结果实验组皮瓣100%成活率16例,98%～99%成活率5例,对照组皮瓣100%成活率8例,98%～99%成活率13例;实验组平均的断蒂时间为（10.4±2.4）天,对照组则为（15.0±5.3）天。实验组皮瓣成活率明显高于对照组（P〈0.05）,断蒂时间也较对照组缩短（P〈0.01）。结论封闭负压吸引在腹部带蒂真皮下血管网皮瓣修复手部热压伤的应用中,可促进皮瓣与创面愈合,提高皮瓣的成活率及缩短断蒂时间。     

Thermo‐Responsive Copolymers Based on Poly(N‐isopropylacrylamide) and Poly[2‐(methacryloyloxy)ethyl phosphorylcholine]: Light Scattering and Microscopy Experiments

Aqueous self‐assembly of thermosensitive triblock copolymers based on poly(N‐isopropylacrylamide) and poly[2‐(methacryloyloxy)ethyl phosphorylcholine] (PNIPAM_m–PMPC_n–PNIPAM_m and PNIPAM_m–PMPC_n–S–S–PMPC_n–PNIPAM_m) were studied using light scattering (SLS and DLS), TEM and fluorescence experiments. These techniques were used to investigate the morphological transition as a function of the temperature, below and above the LCST of the PNIPAM, at various triblock copolymer concentrations ranging from dilute to semi‐dilute regimes. Below the LCST and at low concentrations, aqueous solutions show micellar behavior, while above the LCST self‐assembly leading to large nanoparticles stabilized with PMPC chains. Such behavior is the onset of a gel‐like phase transition observed at higher concentrations.

     

Temperaturresistenz pathogener Dermatophyten und von Candida albicans unter Sauna-ähnlichen Bedingungen

Zusammenfassung: Ausgehend von der großen Morbidität an Dermatomykosen und der ständigen Zunahme sowie der raschen Verbreitung öffentlicher und privater Saunen konnte aufgezeigt werden, daß trotz der in Saunen herrschenden hohen Temperaturen und Luftfeuchtigkeit eine Kontamination mit pathogenen Dermatophyten und Candida albicans möglich ist, da sie bei 30-minütiger Exposition in geringer Luftfeuchte Temperaturen von 80°-100° C tolerieren und unter entsprechenden Bedingungen bei hoher Luftfeuchte Temperaturen von 60°-80° C aushalten. Als zusätzlicher Faktor der erhöhten Temperaturresistenz läßt sich feststellen, daß die in Saunen verwendeten Baumaterialien (Holz) die Überlebensfähigkeit um 10°-20° C erhöhen.
Summary: In spite of the high temperature and high air moisture in saunas, contamination with pathogenic dermatophytes and Candida albicans is possible as the thermoresistance during an exposition time of 30 minutes proved to be 80°-100°C at low air moisture and 60°-80°C at high air moisture. Using wood as germ carrier increased the thermoresistance by 10°-20°C as compared with glass carriers. This is of practical importance as wood is the main construction material of saunas.     

Does the transition temperature of Cu–NiTi archwires affect the amount of tooth movement during alignment?

OBJECTIVES: To examine whether the transition temperature of Cu-NiTi archwires has an effect on the tooth movement during the alignment phase of orthodontic treatment. DESIGN: 'Split mouth' design in randomly selected patients. SETTING AND SAMPLE POPULATION: The Department of Orthodontics, School of Dentistry, University of Aarhus. Fifteen randomly selected patients with identical level of irregularity in the alignment phase of their treatment. Experiment Variable - Specially manufactured Cu-NiTi archwires for the upper arch were inserted. These consisted of two separate halves, each with its own transition temperature, respectively 27 degrees and 40 degrees C, and clamped together in the middle. OUTCOME MEASURE: The tooth movement, expressed as two translations and a rotation, in the occlusal plane was measured from the patients' intraoral photographs taken upon insertion of the archwires and again after 1 month. RESULTS: Tooth movements tended to be larger on the 40 degrees C-side, however only in case of the total translation of the premolars was this difference significant. In general, patients had not noticed any difference between the two sides of the archwire, although one patient stated the 27 degrees C-side to be more comfortable as the 40 degrees C-side had bothered her when drinking hot beverages. CONCLUSION: The transition temperature of Cu-NiTi archwires has indeed an effect on the amount of tooth movement during alignment. However, the differences are so small though that it is the question whether they can be noticed clinically. The study corroborates the trend towards the use of lower forces within orthodontics.     

热扫描成像系统专用床的研制

运用机械与电气结构相结合的方法，带动透热网托移动，结果可使人体平卧在床上，达到既能转动人体，又不影响散热之目的。专用床是红外热成像卧位检查的有用设备。     

宫颈癌后装治疗的剂量分布测试

目的:根据临床常用的治疗方案,用JR1152F型热释光剂量计(TLD)和仿真人体盆腔模型研究宫颈癌腔内后装治疗剂量分布,并了解临床后装放射治疗体内剂量测量点各参数对直肠并发症的影响.方法:选定TLD元件测量剂量线性响应范围和重复性、体模的关键器官的剂量分布以及近源区剂量分布,并对TLD元件及热释光剂量仪进行剂量刻度.结果:TLD元件剂量线性范围0～300 cGy,重复性好;体模和近源区参考点实测剂量与TPS计算值符合较好.结论:本工作采用的实验测量方法简便,严密,可靠性高.各项指标均达到预期目标.     

Doxorubicin‐Loaded Nanogel Assemblies with pH/Thermo‐triggered Payload Release for Intracellular Drug Delivery

For improving intracellular doxorubicin (DOX) delivery, DOX‐encapsulated nanogel assemblies with pH/thermo‐responsive drug release are developed. DOX and a graft copolymer comprising acrylic acid (AAc) and 2‐methacryloyloxyethyl acrylate (MEA) units as the backbone and with poly(N‐isopropylacrylamide) (PNIPAAm) and monomethoxy poly(ethylene glycol) as the grafts at pH 7.4 and 4 °C undergo electrostatically induced co‐association into copolymer/DOX nanocomplexes. After being crosslinked by polymerization of the MEA moieties, the complex nanoconstructs exhibit a unique nanogel‐like architecture. Taking advantage of the extensive electrostatic attraction of the DOX molecules with ionized AAc residues and π–π stacking among copolymer‐bound DOX molecules, the DOX‐loaded nanogels show a relatively high payload content. With the milieu pH being reduced from 7.4 to 4.7, the drug release is appreciably promoted due to the massive disruption of ionic AAc/DOX pairings. The thermo‐evolved phase transition of the PNIPAAm grafts further accelerates drug elution, particularly at pH 4.7. In vitro characterization indicates that the DOX‐embedded nanogels endocytosed by HeLa cells can progressively release DOX within acidic organelles. As a result, the viability of cancer cells treated with DOX‐loaded nanoparticles can be further reduced by prolonging incubation time. This work demonstrates the great potential of the DOX‐loaded nanogel assemblies for effective intracellular drug delivery.

     

Thermosensitivity in a reconstructed microtic ear

The aim of this study was to evaluate thermo-thresholds in autologous reconstructed microtic ears. Nineteen patients with unilateral microtia were investigated no less than two years after the last operation (3.6±1.7 years). Their normal corresponding ear acted as controls. Eight healthy children were also investigated to illustrate technical differences between measuring the two sides. Thermal sensitivity was tested quantitatively using a SENSELab MSA Thermotest. The skin temperature was also tested. Three different areas of the ear were examined: the lobe, the antihelix, and the helix. The reconstructed ear had a significantly higher skin temperature for all investigated areas compared with the normal ear (reconstructed ear 30.2±1.2°C, normal ear 28.6±0.9°C). For the controls there were no significant differences in any area. For the patients there were small differences in perception of cold between the reconstructed and the normal ear. There were significant differences in the antihelix region and the helix in heat perception in the reconstructed ear compared with the normal one (helix reconstructed ear 43.9±3.8°C, helix normal ear 38.3±3.0°C, antihelix reconstructed ear 39.9±3.0°C, antihelix normal ear 36.4±1.7°C). The reconstructed ear had a changed thermosensitivity, but there did not seem to be any clinical disadvantages.