Polyethylene glycol fusion repair of severed rat sciatic nerves reestablishes axonal continuity and reorganizes sensory terminal fields in the spinal cord

Peripheral nerve injuries result in the rapid degeneration of distal nerve segments and immediate loss of motor and sensory functions;behavioral recovery is typically poor.We used a plasmalemmal fusogen,polyethylene glycol(PEG),to immediately fuse closely apposed open ends of severed proximal and distal axons in rat sciatic nerves.We have previously reported that sciatic nerve axons repaired by PEG-fusion do not undergo Wallerian degeneration,and PEG-fused animals exhibit rapid(within 2–6 weeks)and extensive locomotor recovery.Furthermore,our previous report showed that PEG-fusion of severed sciatic motor axons was non-specific,i.e.,spinal motoneurons in PEG-fused animals were found to project to appropriate as well as inappropriate target muscles.In this study,we examined the consequences of PEG-fusion for sensory axons of the sciatic nerve.Young adult male and female rats(Sprague–Dawley)received either a unilateral single cut or ablation injury to the sciatic nerve and subsequent repair with or without(Negative Control)the application of PEG.Compound action potentials recorded immediately after PEG-fusion repair confirmed conduction across the injury site.The success of PEG-fusion was confirmed through Sciatic Functional Index testing with PEG-fused animals showing improvement in locomotor function beginning at 35 days postoperatively.At 2–42 days postoperatively,we anterogradely labeled sensory afferents from the dorsal aspect of the hindpaw following bilateral intradermal injection of wheat germ agglutinin conjugated horseradish peroxidase.PEG-fusion repair reestablished axonal continuity.Compared to unoperated animals,labeled sensory afferents ipsilateral to the injury in PEG-fused animals were found in the appropriate area of the dorsal horn,as well as inappropriate mediolateral and rostrocaudal areas.Unexpectedly,despite having intact peripheral nerves,similar reorganizations of labeled sensory afferents were also observed contralateral to the injury and repair.This central reorganization may contribute to the improved behavioral recovery seen after PEG-fusion repair,supporting the use of this novel repair methodology over currently available treatments.

Polyethylene glycol has immunoprotective effects on sciatic allografts, but behavioral recovery and graft tolerance require neurorrhaphy and axonal fusion

Behavioral recovery using(viable)peripheral nerve allografts to repair ablation-type(segmental-loss)peripheral nerve injuries is delayed or poor due to slow and inaccurate axonal regeneration.Furthermore,such peripheral nerve allografts undergo immunological rejection by the host immune system.In contrast,peripheral nerve injuries repaired by polyethylene glycol fusion of peripheral nerve allografts exhibit excellent behavioral recovery within weeks,reduced immune responses,and many axons do not undergo Wallerian degeneration.The relative contribution of neurorrhaphy and polyethylene glycol-fusion of axons versus the effects of polyethylene glycol per se was unknown prior to this study.We hypothesized that polyethylene glycol might have some immune-protective effects,but polyethylene glycol-fusion was necessary to prevent Wallerian degeneration and functional/behavioral recovery.We examined how polyethylene glycol solutions per se affect functional and behavioral recovery and peripheral nerve allograft morphological and immunological responses in the absence of polyethylene glycol-induced axonal fusion.Ablation-type sciatic nerve injuries in outbred Sprague–Dawley rats were repaired according to a modified protocol using the same solutions as polyethylene glycol-fused peripheral nerve allografts,but peripheral nerve allografts were loose-sutured(loose-sutured polyethylene glycol)with an intentional gap of 1–2 mm to prevent fusion by polyethylene glycol of peripheral nerve allograft axons with host axons.Similar to negative control peripheral nerve allografts not treated by polyethylene glycol and in contrast to polyethylene glycol-fused peripheral nerve allografts,animals with loose-sutured polyethylene glycol peripheral nerve allografts exhibited Wallerian degeneration for all axons and myelin degeneration by 7 days postoperatively and did not recover sciatic-mediated behavioral functions by 42 days postoperatively.Other morphological signs of rejection,such as collapsed Schwann cell basal lamina tubes,were absent in polyethylene glycol-fused peripheral nerve allografts but commonly observed in negative control and loose-sutured polyethylene glycol peripheral nerve allografts at 21 days postoperatively.Loose-sutured polyethylene glycol peripheral nerve allografts had more pro-inflammatory and less anti-inflammatory macrophages than negative control peripheral nerve allografts.While T cell counts were similarly high in loose-sutured-polyethylene glycol and negative control peripheral nerve allografts,loose-sutured polyethylene glycol peripheral nerve allografts expressed some cytokines/chemokines important for T cell activation at much lower levels at 14 days postoperatively.MHCI expression was elevated in loose-sutured polyethylene glycol peripheral nerve allografts,but MHCII expression was modestly lower compared to negative control at 21 days postoperatively.We conclude that,while polyethylene glycol per se reduces some immune responses of peripheral nerve allografts,successful polyethylene glycol-fusion repair of some axons is necessary to prevent Wallerian degeneration of those axons and immune rejection of peripheral nerve allografts,and produce recovery of sensory/motor functions and voluntary behaviors.Translation of polyethylene glycol-fusion technologies would produce a paradigm shift from the current clinical practice of waiting days to months to repair ablation peripheral nerve injuries.

Polyethylene glycol fusion repair of severed sciatic nerves accelerates recovery of nociceptive sensory perceptions in male and female rats of different strains

Successful polyethylene glycol fusion(PEG-fusion)of severed axons following peripheral nerve injuries for PEG-fused axons has been reported to:(1)rapidly restore electrophysiological continuity;(2)prevent distal Wallerian Degeneration and maintain their myelin sheaths;(3)promote primarily motor,voluntary behavioral recoveries as assessed by the Sciatic Functional Index;and,(4)rapidly produce correct and incorrect connections in many possible combinations that produce rapid and extensive recovery of functional peripheral nervous system/central nervous system connections and reflex(e.g.,toe twitch)or voluntary behaviors.The preceding companion paper describes sensory terminal field reo rganization following PEG-fusion repair of sciatic nerve transections or ablations;howeve r,sensory behavioral recovery has not been explicitly explored following PEG-fusion repair.In the current study,we confirmed the success of PEG-fusion surgeries according to criteria(1-3)above and more extensively investigated whether PEG-fusion enhanced mechanical nociceptive recovery following sciatic transection in male and female outbred Sprague-Dawley and inbred Lewis rats.Mechanical nociceptive responses were assessed by measuring withdrawal thresholds using von Frey filaments on the dorsal and midplantar regions of the hindpaws.Dorsal von Frey filament tests were a more reliable method than plantar von Frey filament tests to assess mechanical nociceptive sensitivity following sciatic nerve transections.Baseline withdrawal thresholds of the sciatic-mediated lateral dorsal region differed significantly across strain but not sex.Withdrawal thresholds did not change significantly from baseline in chronic Unoperated and Sham-operated rats.Following sciatic transection,all rats exhibited severe hyposensitivity to stimuli at the lateral dorsal region of the hindpaw ipsilateral to the injury.However,PEG-fused rats exhibited significantly earlier return to baseline withdrawal thresholds than Negative Control rats.Furthermore,PEG-fused rats with significantly improved Sciatic Functional Index scores at or after 4 weeks postoperatively exhibited yet-earlier von Frey filament recove ry compared with those without Sciatic Functional Index recovery,suggesting a correlation between successful PEG-fusion and both motor-dominant and sensory-dominant behavioral recoveries.This correlation was independent of the sex or strain of the rat.Furthermore,our data showed that the acceleration of von Frey filament sensory recovery to baseline was solely due to the PEG-fused sciatic nerve and not saphenous nerve collateral outgrowths.No chronic hypersensitivity developed in any rat up to 12 weeks.All these data suggest that PEG-fusion repair of transection peripheral nerve injuries co uld have important clinical benefits.

Reaction pathways and selectivity in the chemo-catalytic conversion of cellulose and its derivatives to ethylene glycol:A review

Biomass-to-ethylene glycol is an effective means to achieve high-value utilisation of cellulose but is hindered by low conversion efficiency and poor catalyst activity and stability.Glucose and cellobiose are derivatives of cellulose conversion to ethylene glycol,and it is found that studying the reaction process of both can help to understand the reaction mechanism of cellulose.It is desirable to develop a reusable,highly active catalyst to convert cellulose into ethylene glycol.This ideal catalyst might have one or more active sites described the conversion steps above.Here,we discuss the catalyst development of celluloseto-ethylene glycol,including tungsten,tin,lanthanide,and other transition metal catalysts,and special attention is given to the reaction mechanism and kinetics for preparing ethylene glycol from cellulose,and the economic advantages of biomass-to-ethylene glycol are briefly introduced.The insights given in this review will facilitate further development of efficient catalysts,for addressing the global energy crisis and climate change related to the use of fossil fuels.

Sn nucleation and growth from Sn(II)dissolved in ethylene glycol:Electrochemical behavior and temperature effect

Thermodynamic and kinetic aspects of Sn nucleation and growth processes onto a glassy carbon electrode from SnCl2·2H2O dissolved in ethylene glycol solutions were studied.Typical reduction and oxidation peaks observed in voltammograms have demonstrated the capability of ethylene glycol solutions to electrodeposit Sn.The temperature-dependence of diffusion coefficient values derived from potentiodynamic and potentiostatic studies helped to determine and validate estimations of the activation energy for Sn(II)bulk diffusion.Chronoamperometric results have identified that,the suitable model to describe the early stage of Sn electrodeposition could be composed of Sn three-dimensional nucleation and diffusion-controlled growth and water reduction contributions,which was duly validated by theoretical and experimental approaches.From the model,typical kinetic parameters such as the nucleation frequency of Sn(A),number density of Sn nuclei(N_(0)),and diffusion coefficient of Sn(II)ions(D),were determined.The presence of Sn nuclei with excellent quality and their structures were verified using SEM,EDX,and XRD techniques.

Vertically aligned montmorillonite aerogel-encapsulated polyethylene glycol with directional heat transfer paths for efficient solar thermal energy harvesting and storage

The conversion and storage of photothermal energy using phase change materials(PCMs)represent an optimal approach for harnessing clean and sustainable solar energy.Herein,we encapsulated polyethylene glycol(PEG)in montmorillonite aerogels(3D-Mt)through vacuum impregnation to prepare 3D-Mt/PEG composite PCMs.When used as a support matrix,3D-Mt can effectively prevent PEG leakage and act as a flame-retardant barrier to reduce the flammability of PEG.Simultaneously,3D-Mt/PEG demonstrates outstanding shape retention,increased thermal energy storage density,and commendable thermal and chemical stability.The phase transition enthalpy of 3D-Mt/PEG can reach 167.53 J/g and remains stable even after 50 heating-cooling cycles.Furthermore,the vertical sheet-like structure of 3D-Mt establishes directional heat transport channels,facilitating efficient phonon transfer.This configuration results in highly anisotropic thermal conductivities that ensure swift thermal responses and efficient heat conduction.This study addresses the shortcomings of PCMs,including the issues of leakage and inadequate flame retardancy.It achieves the development and design of 3D-Mt/PEG with ultrahigh strength,superior flame retardancy,and directional heat transfer.Therefore,this work offers a design strategy for the preparation of high-performance composite PCMs.The 3D-Mt/PEG with vertically aligned and well-ordered array structure developed in this research shows great potential for thermal management and photothermal conversion applications.

Electrodeposition behavior of bright nickel in air and water-stable betaine·HCl-ethylene glycol ionic liquid

The electrodeposition behaviors of nickel on glassy carbon（GC） and carbon steel（CS） electrodes were investigated in the14.3%-85.7%（mole fraction） betaine.HCl ethylene glycol（EG） ionic liquid using cyclic voltammetry and chronoamperometry.The results indicated that the reduction of Ni（Ⅱ） on CS electrode via a diffusion-controlled quasi-reversible process was much more facile and easier than that occurred on GC electrode,which followed a diffusion-controlled three-dimensional instantaneous nucleation and growth.Scanning electron microscopy was used to observe that the deposit was dense and contained fine crystallites with average size of（80±4） nm.Energy dispersive spectrometer analysis showed that the obtained deposit was metallic nickel.X-ray diffraction spectroscopy indicated that（111） plane was the most preferred crystal orientation.The nickel deposit was luminous and bright,and had good adhesion with the CS substrate.

Effects of Oral Administration of Propylene Glycol and Ca-P-Mg Mixture on Milk Quality and SCC of Dairy Cows after Birth

In order to further study the postpartum care technology of dairy cows,the effects of oral administration of propylene glycol or Ca-P-Mg mixture and compound oral rehydration salts on milk quality and SCC of dairy cows after birth were investigated. The results showed that the milk fat and dry matter contents in the dairy cows administered with Ca-P-Mg mixture and compound oral rehydration salts were higher than those in the dairy cows administered with propylene glycol（P 〈0.05）. However, there were no significant differences in milk sugar and protein contents and SCC between the two administration groups.

5R,6S-Tg立体异构体稳定构型的理论研究

胸腺嘧啶二醇(Thymine glycol,Tg)是最常见的DNA氧化损伤,人体基因组内含有数千个Tg损伤.Tg对DNA聚合酶有强的阻断,可能导致细胞死亡、癌症等严重后果.一旦生成,Tg就以两对顺反立体异构体混合物的形式存在,修复酶对Tg的修复表现出立体选择性.在所有的异构体中,5R,6S-Tg数量最多.NMR实验表明5R,6S-Tg 5-CH_(3)可能存在轴向或赤道两种不同构象,但是5R,6S-Tg最稳定构象依然存在争论.基于碱基水平的理论研究表明5R,6S-Tg 5-CH_(3)取向为轴向时最稳定.然而,本研究在核苷水平的计算表明,5-CH_(3)取向为赤道时最稳定,高精度的簇耦合理论CCSD(T)/6-311++G(d,p)对结果进行了验证.进一步的分析表明,分子内氢键和氧孤电子对之间的π-π共轭协同作用稳定了5R,6S-Tg的赤道构象.

PREPARATION OF HIGH DENSITY POLYETHYLENE/POLYETHYLENE-BLOCK-POLY(ETHYLENE GLYCOL)COPOLYMER BLEND POROUS MEMBRANES VIA THERMALLY INDUCED PHASE SEPARATION PROCESS AND THEIR PROPERTIES

High density polyethylene （HDPE）/polyethylene-block-poly（ethylene glycol） （PE-b-PEG） blend porous membranes were prepared via thermally induced phase separation （TIPS） process using diphenyl ether （DPE） as diluent. The phase diagrams of HDPE/PE-b-PEG/DPE systems were determined by optical microscopy and differential scanning calorimetry （DSC）. By varying the content of PE-b-PEG, the effects of PE-b-PEG copolymer on morphology and crystalline structure of membranes were studied by scanning electron microscopy （SEM） and wide angle X-ray diffraction （WAXD）. The chemical compositions of whole membranes and surface layers were characterized by elementary analysis, Fourier transform infrared spectroscopy-attenuated total reflection （FTIR-ATR） and X-ray photoelectron spectroscopy （XPS）. Water contact angle, static protein adsorption and water flux experiments were used to evaluate the hydrophilicity, antifouling and water permeation properties of the membranes. It was found that the addition of PE-b-PEG increased the pore size of the obtained blend membranes. In the investigated range of PE-b-PEG content, the PEG blocks could not aggregate into obviously separated domains in membrane matrix. More importantly, PE-b-PEG could not only be retained stably in the membrane matrix during membrane formation, but also enrich at the membrane surface layer. Such stability and surface enrichment of PE-b-PEG endowed the blend membranes with improved hydrophilicity, protein absorption resistance and water permeation properties, which would be substantially beneficial to HDPE membranes for water treatment application.

THE STRUCTURE AND PROPERTIES OF CHITOSAN/POLYETHYLENE GLYCOL/SILICA TERNARY HYBRID ORGANIC-INORGANIC FILMS

The ternary hybrid films consisting of chitosan(CS),polyethylene glycol(PEG)and nano-sized silica which was surface-modified by amino groups(RNSA)were prepared.The structures of the blend membranes were characterized by attenuation total reflection-infrared spectroscopy(ATR-IR),X-ray diffraction(XRD),optical microscopy(OM)and differential scanning calorimetry(DSC).The results showed that the addition of silica affected not only the distribution and crystallinity of PEG on the sample surface,but also the pha...

Y-shaped block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide) synthesized by ATRP

Novel Y-shaped block copolymers of poly（ethylene glycol） and poly（N-isopropylacrylamide）, PEG-b-（PNIPAM）2, were successfully synthesized through atom transfer radical polymerization （ATRP）. A difunctional macroinitiator was prepared by esterification of 2,2-dichloroacetyl chloride with poly（ethylene glycol） monomethyl ether （PEG）. The copolymers were obtained via the ATRP ofN-isopropylacrylamide （NIPAM） at 30℃ with CuCl/Me6TREN as a catalyst system and DMF/H2O （v/v = 3：1） mixture as solvent. The resulting copolymers were characterized by gel permeation chromatography （GPC） and ^1H NMR. These block copolymers show controllable molecular weights and narrow molecular weight distributions （PDI 〈 1.15）. Their phase transition temperatures and the corresponding enthalpy changes in aqueous solution were measured by differential scanning calorimetry （DSC）. As a result, the phase transition temperature of PEG45-b-（PNIPAM55）2 is higher than that of PNIPAM, however, the corresponding enthalpy change is much lower, indicating the significant influence of the macromolecular composition and architecture on the phase transition.

Surface Modification of 316L Stainless Steel by Grafting Methoxy Poly（ethylene glycol） to Improve the Biocompatibility

Percutaneous coronary intervention（PCI） has become an important method for the treatment of the pa- tients with coronary heart disease; however, problems, such as vascular endothelial inflammation, late thrombosis, and stent restenosis still exist as a result of poor biocompatibility of the materials. To enhance the biocompatibility, methoxy poly（ethylene glycol）（mPEG） was immobilized on the surface of AISI 316 grade stainless steel（SS）（AISI： American Iron and Steel Institute）. First, silanized mPEG was synthesized by the direct coupling of mPEG with 3-isocyanatopropyltriethoxysilane（IPTS） via urethane bonds, and the silanized mPEG was then grafted on the surface of SS that was hydroxylated with piranha solution. The results obtained from contact angle goniometry, X-ray pho- toelectron spectroscopy（XPS）, and atomic force microscopy（AFM） confirm that the mPEG modified steel contained more C and Si and less Fe and Cr on its surface, exhibiting a morphological change and decrease in the contact angle. The biocompatibility of the mPEG modified SS was evaluated with fibrinogen adsorption, platelet activation and adhesion, and human umbilical vein endothelial celI（HUVEC） adhesion. Fibrinogen adsorption, platelet activation, and adhesion were clearly suppressed on the surface-modified steel. In addition, human umbilical vein endothelial cell（HUVEC） could adhere and proliferate on the surface of the mPEG-modified SS. This study indicates that the modification of 316L SS with mPEG could enhance the biocompatibility and provide a primary experimental founda- tion for the development of next-generation coronary stent materials for clinical application.

PLGA/赖氨酸接枝氧化石墨烯纳米粒子复合支架对MC3T3细胞成骨分化的影响

背景:骨损伤后如何有效促进骨再生和骨重建一直是临床骨修复研究中的关键问题,利用生物和降解材料搭载生物活性因子在骨修复中具有优秀的应用前景。目的:探究赖氨酸接枝氧化石墨烯(LGA-g-GO)纳米粒子改性的聚乳酸-羟基乙酸共聚物(PLGA)复合支架对成骨分化及新骨形成的影响。方法:将PLGA溶于二氯甲烷中,利用溶剂挥发法制备PLGA支架;将氧化石墨烯均匀分散于PLGA溶液中制备PLGA/GO复合支架;利用化学接枝法制备LGA-g-GO纳米粒子,将LGA-g-GO纳米粒子按不同的质量比(1%,2%,3%)与PLGA共混构建出PLGA/LGA-g-GO复合支架。表征5组支架的微观形貌、亲水性、蛋白吸附能力。将MC3T3细胞分别接种于5组支架表面,检测细胞增殖与成骨分化情况。结果与结论:①扫描电镜下可见PLGA支架表面光滑平坦,其余4组支架表面粗糙,并且随着LGA-g-GO纳米粒子加入量的增加,复合支架的表面粗糙程度加重;PLGA/LGA-g-GO(3%)复合支架的水接触角低于其他4组支架(P<0.05);PLGA/LGA-g-GO(1%,2%,3%)复合支架的蛋白吸附能力强于PLGA、PLGA/GO支架(P<0.05);②CCK-8检测显示,PLGA/LGA-g-GO(2%,3%)复合支架可促进MC3T3细胞的增殖;碱性磷酸酶染色与茜素红染色显示,PLGA/LGA-g-GO(2%,3%)组细胞碱性磷酸酶活性高于其他3组(P<0.05),PLGA/GO组、PLGA/LGA-g-GO(1%,2%,3%)组钙沉积多于PLGA组(P<0.05);③结果表明,PLGA/LGA-g-GO复合支架能够促进成骨细胞的增殖和成骨分化,有利于骨损伤后的骨再生和骨重建。

Modification of polycarbonateurethane surface with poly （ethylene glycol） monoacrylate and phosphorylcholine glyceraldehyde for anti-platelet adhesion

Poly（ethylene glycol） monoacrylate （PEGMA） is grafted onto polycarbonateurethane （PCU） surface via ultraviolet initiated photopolymerization. The hydroxyl groups of poly（PEGMA） on the surface react with one NCO group of isophorone diisocyanate （IPD1） and another NCO group of IPDI is then hydrolyzed to form amino terminal group, which is further grafted with phosphorylcholine glyceraldehyde to establish a biocompatible hydrophilic structure on the surface. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirm the successful grafting of both PEG and phosphorylcholine functional groups on the surface. The decrease of the water contact angle for the modified film is caused by synergic effect of PEG and phosphorylcholine, which both have the high hydrophilicity. Furthermore, the number of platelets adhered is relative low on the synergetically modified PCU film compared with the PCU film modified only by poly（PEGMA）. Our synergic modification method using both PEG and phosphorylcho- line may be applied in surface modification of bloodcontacting biomaterials and some relevant devices.

AN APPROACH TO SYNTHESIZE POLY(ETHYLENE GLYCOL)-b-POLY(ε-CAPROLACTONE) WITH TERMINAL AMINO GROUP via SCHIFF'S BASE AS AN INITIATOR

A new method to synthesize a degradable terminal amino group-containing copolymer,poly(ethylene glycol)-b- poly(ε-caprolactone)(MPEG-PCL-NH_2),was developed in the following three steps:(1)the ring-opening polymerization (ROP)ofε-caprolactone from the Schiff base prepared from benzatdehyde and ethanolamine(Ph-CH=NCH_2CH_2OH)used as an initiator to obtain heterobifunctional poly(ε-caprolactone)with one terminal Schiff base group and one hydroxyl group (HO-PCL-CH_2CH_2N=CH-Ph);(2)the coupling reaction of two ...

Stereoselective Synthesis of Polysubstituted Cyclopropanes from Poly(ethylene glycol) Supported Pyridinium Ylide

Polysubstituted cyclopropanes were efficiently prepared with poly（ethylene glycol）（PEG） as soluble support. The reaction of PEG-supported pyridinium ylide with arylidenemalononitrile（R=CN） or ethyl arylidenecyanoa-cetate（R=COOEt） in the presence of triethylamine（TEA） afforded PEG-supported cyclopropanecarboxylates, which were cleaved by 1% KCN/EtOH to obtain polysubstituted cyclopropanes with exclusive trans-selectivity and good yields.

Adsorption-desorption of Silica Nanoparticles on Poly（ethylene glycol） Brushes Grafted onto Au Substrate Studied by Quartz Crystal Microbalance

The adsorption-desorption of silica nanoparticles（NPs） on poly（ethylene glycol）（PEG） grafted onto gold（Au） substrate was studied by quartz crystal microbalance with dissipation monitoring（QCM-D） technique. The results of frequency and dissipation show that SiO2 NPs can be adsorbed strongly on PEG-SH brushes at pH of 9.6, and a new dense and rigid construction is formed. Adjusting the pH from 9.6 to 12.3 resulted in the desorption of si- lica NPs from the PEG brushes because of a significant weakening of the hydrogen bond between the silica NPs and PEG chains. In addition, the viscoelastic properties of the system during the adsorption-desorption process were also analyzed via the relationship between the normalized frequency（Af/n） and mass. And the corresponding atomic force microscopy（AFM） images also exhibit morphological changes during the above process, consistent with the changes in viscoelasticity.

Characterization of UV-curable Poly（ethylene glycol） Diacrylate Based Hydrogels

Poly（ethylene glycol） diacrylate/polyvinyl alcohoI（PEGDA/PVA） hydrogels were prepared from PEGDA and PVA as precurors by means of single UV radiation（UV ra.）, UV radiation followed by high energy electron beam irradiation（Irra.）, UV radiation followed by freeze-thawing（FT） or UV ra. and Irra. followed by FT, respectively. 2-Hydroxy-l-[4-（hydroxyethoxy）phenyl]-2-methyl-l-propanone（Irgacure 2959） was used as a photoinitiator. The effects of the various methods on the swelling and mechanical properties of the hydrogels were investigated. The results show that hydrogels made by UV ra. plus high energy electron beam irradiation followed by FT showed a higher crosslinking density and a larger tensile strength than those made by the other methods.

Enzymatic Synthesis and Characterization of Novel Amphiphilic Triblock Copolymer Poly(p-dioxanone-co-5-benzyloxytrimethylene carbonate)-block-poly(ethylene glycol)

Novel amphiphilic triblock copolymer poly（p-dioxanone-co-5-benzyloxytrimethylene carbonate）-block-poly（ethylene glycol）-block-poly（p-dioxanone-co-5-benzyloxytrimethylene carbonate） （p（PDO-co-BTMC）-b-PEG-b-p（PDO-co-BTMC）） was successfully synthesized using immobilized porcine pancreas lipase on porous silica particles （IPPL） as the catalyst for the fLrSt time. 1H NMR, 13C NMR and GPC analysis were used to confirm the structures of resulting copolymers. The molecular weight （Mn） of the copolymer with feed ratio of 69：20：11 （BTMC： PDO： PEG ） was 31300 g/mol and the polydispersity was 1.85, while the Mn decreased to 25000 g/mol and polydispersity of 1.93 with the feed ratio of 50：40：10.