聚乙二醇缩水甘油醚改性丝素蛋白研究

采用聚乙二醇400与环氧氯丙烷合成聚乙二醇缩水甘油醚(PEGO)并对丝素蛋白(SF)进行改性,采用红外光谱、X射线衍射、差式量热扫描、扫描电镜和物理性能测试对共混膜的结构和性能进行表征,表明PEGO的加入使得丝素蛋白从silkⅠ结构向silkⅡ构象转变,而当m(PEGO)∶m(SF)>50%的时候,共混膜的二级结构却呈现相反变化。共混膜的含水量由共混膜的表面粗糙度和亲水性决定,在m(PEGO)∶m(SF)<50%时,其含水量随粗糙度增加而减少;在m(PEGO)∶m(SF)>50%时,随着PEGO的增加,SF/PEGO共混膜的含水量增加。当m(PEGO)∶m(SF)=50%时,共混膜SP50具有最好的热稳定性和良好的机械性能。     

用二维FTIR研究纳米TiO2改性丝素蛋白聚集态结构转变

采用溶胶-凝胶方法制备纳米TiO₂复合丝素膜。UV和SEM测试结果表明,该丝素膜中纳米TiO₂均匀分散在丝素中,TiO₂粒径约为80 nm;同时采用一维红外光谱、二维红外相关光谱对纯丝素膜及复合丝素膜结构进行表征。结果表明,随着纳米TiO₂的生成,丝素蛋白中弱氢键缔合的N—H键以及自由的N—H键发生断裂及重组,生成了强氢键;丝素分子从无序状态转变为有序排列,同时无规线团构象及α螺旋构象向β折叠构象发生转变,最后促使丝素蛋白的结晶构象从Silk Ⅰ转变为Silk Ⅱ。     

用二维FTIR研究纳米TiO2改性丝素蛋白聚集态结构转变

采用溶胶-凝胶方法制备纳米TiO₂复合丝素膜。UV和SEM测试结果表明,该丝素膜中纳米TiO₂均匀分散在丝素中,TiO₂粒径约为80 nm;同时采用一维红外光谱、二维红外相关光谱对纯丝素膜及复合丝素膜结构进行表征。结果表明,随着纳米TiO₂的生成,丝素蛋白中弱氢键缔合的N—H键以及自由的N—H键发生断裂及重组,生成了强氢键;丝素分子从无序状态转变为有序排列,同时无规线团构象及α螺旋构象向β折叠构象发生转变,最后促使丝素蛋白的结晶构象从Silk Ⅰ转变为Silk Ⅱ。     

丝素/羧甲基壳聚糖共混膜的结构性能探讨

将含有甘油和戊二醛的丝素与羧甲基壳聚糖按一定比例混合,制得丝素/羧甲基壳聚糖共混膜,对共混膜的结构与性能进行了探讨。结果表明:随着羧甲基壳聚糖含量的增加,共混膜的透气率增大,加入交联剂戊二醛有效地改善了共混膜的力学性能,但其透气率有所降低;当丝素与羧甲基壳聚糖的质量比为4/1时,共混膜的断裂强度最大,力学性能较好,共混膜相容性较好,其断面光滑、致密。制备丝素/羧甲基壳聚糖共混膜的较佳条件为:丝素中的甘油质量分数为15%,戊二醛质量分数为0.075%,丝素与羧甲基壳聚糖质量比为4/1。     

丝素蛋白/海藻酸钠复合纤维的制备与性能表征

为了提高海藻酸钠(SA)纤维的力学性能,将从蚕茧中提取的丝素蛋白(SF)和SA共混,制备了SF/SA纺丝溶液,通过湿法纺丝制得SF/SA复合纤维,对纺丝溶液流变性能进行了研究,对SF/SA复合纤维进行了结构与性能表征。结果表明:SF/SA纺丝溶液为切力变稀的假塑性流体,纺丝溶液的表观黏度随SF含量增加呈增加的趋势,当SF质量分数(相对SA)为10%时,纺丝溶液结构黏度指数最小,可纺性最好;提取的SF以无规卷曲结构和β-折叠结构为主,SA和SF间有较强的氢键作用;SF/SA复合纤维以非晶形态存在,纤维表面存在明显的沟槽结构,与纯SA纤维相比,SF的加入提高了SA纤维的力学性能,SF质量分数为10%的SF/SA复合纤维的断裂强度高达1.63 cN/dtex,较SA的提高了22.5%,SF的加入使复合纤维的耐热性略有降低。     

静电纺丝射流分裂过程的探讨

以质量分数28％再生蚕丝素蛋白水溶液进行静电纺丝,结合拉曼光谱和广角X射线分析测试纤维的构象和晶体结构,探讨了纺丝过程中射流发生情况。结果表明,静电纺丝所得纤维中,仅部分丝素蛋白分子转变为β折叠构象,丝素Ⅱ晶型含量少,纤维只经历了有限的拉伸,说明静电纺丝中射流不是单一细化,而是发生了分裂。     

丝素蛋白/聚丙烯酸共混膜仿生合成羟基磷灰石

将丝素蛋白(SF)与聚丙烯酸(PAA)共混,制备丝素蛋白/聚丙烯酸(SF/PAA)共混膜;然后将此共混膜进行改性及矿化处理后,放置于(37±0.5)℃人体仿生液中24h,诱导合成丝素蛋白/羟基磷灰石(SF/HA)复合材料.利用傅里叶红外(FTIR)、X-射线衍射(XRD)、环境扫描电镜(ESEM)以及X射线能谱(EDX...     

聚乳酸/丝素共混膜的制备及其性能

用分子量为10万的聚乳酸（PLLA）对丝素膜进行改性,研究不同的聚乳酸加入量对丝素膜性能的影响,对聚乳酸/丝素共混膜进行了一系列表征。万能电子试验机的测试结果表明,经聚乳酸改性后,丝素膜的断裂强度,断裂伸长率有了较大的改善,当加入聚乳酸占丝素质量为5%时,丝素膜的强度可达到27.1 MPa,伸长率达4.4%; 改性后的丝素膜的亲水性有一定程度降低,溶失率则明显减小,透汽透湿性也有所提高;红外光谱测试表明,改性后的丝素膜含有较多的β构象成分。     

γ射线辐照对PVAL/Gel共混膜拉伸性能的影响

将明胶(Gel)按不同比例加入到聚乙烯醇(PVAL)溶液中,制备Gel质量分数分别为0%,5%,10%,15%和20%的混合溶液,混合均匀后分别浇铸到用硅纸覆盖的玻璃板上制备PVAL/Gel共混膜。研究了用不同剂量的γ射线(60Co)辐照对共混膜拉伸性能的影响,最后用傅立叶变换红外光谱(FTIR)和扫描电子显微镜(SEM)对共混膜进行了结构表征和形貌分析。研究结果表明,用γ射线辐照时,纯PVAL膜、PVAL/Gel共混膜的拉伸强度和断裂伸长率均随着辐照剂量的增加而升高,但达到一定值后又开始下降;当辐照剂量为150 krad时,纯PVAL膜的拉伸强度达到最大值,为37 MPa;当辐照剂量为50 krad时,Gel质量分数分别为5%,10%,15%的共混膜的拉伸强度值均有极大值,分别为33,26,24 MPa。当辐照剂量为100 krad时,共混膜的断裂伸长率均有极大值,其中纯PVAL膜、Gel质量分数为10%的共混膜的断裂伸长率分别为175%,162%。FTIR和SEM分析结果表明,γ射线辐照处理后的膜发生了化学反应,形成了更多的化学键,改善了膜的拉伸性能。     

再生丝素/壳聚糖共混纳米纤维的结构与性能

以98%的甲酸为溶剂,不同质量分数的再生丝素溶液和3.5%的壳聚糖溶液以质量比70∶30共混静电纺丝。测定了壳聚糖的含量对共混膜的结构及力学、溶解等性能的影响。结果表明:随着壳聚糖相对含量的增加,丝素β化程度提高,纤维结晶度增大,丝素与壳聚糖以70∶30共混时的溶失率最小;甲醇处理后,溶失率明显降低;共混纳米纤维的断裂强度随着壳聚糖相对含量的增大而增加,柔软性也逐渐提高;共混纤维膜具有优异的抗菌性。     

Structure and properties of silk fibroin/carboxymethyl chitosan blend films

The secondary structure of silk fibroin (SF) and the compatibility of the two components were associated with the carboxymethyl chitosan (CMCS) content in SF/CMCS blend films. A rather complete conformation transition of SF from random coil to β-sheet occurred after adding 5% CMCS into the SF film, and the blend film exhibited a high crystallinity and a good compatibility. The conformation of SF changed from β-sheet to α-helix when blending 10% CMCS. When the CMCS content was up to 15%, the conformation of SF in blend films showed a transformation from β-sheet to a random coil and their crystallinities decreased evidently; accordingly, there was a two-phase separation structure for the blend films containing 15% CMCS or more. However, the intermolecular interaction between the two polymers still existed in blend film with 15% CMCS or more. The blend films with 5–10% CMCS content showed the lower moisture absorption, swelling capacity, and solubility in water. These properties of blend films increased when adding CMCS more than 15%.     

Enzymatic degradability and release properties of graphene oxide/silk fibroin nanocomposite films

The structure evolution of silk fibroin (SF) in the nanocomposite films with graphene oxide (GO) was investigated and related to the enzymatic degradability and release property. The interaction with GO was found to induce conformation transition of SF from random coil to β-sheet. However, the surface binding constrained the rearrangement of the silk chains, leading to a decrease of β-sheet when GO content was more than 1.0%. The crystal structure of SF played a key role in the degradation of GO/SF composites. The preferential degradation of the hydrophilic blocks resulted in a faster degradation of SF films with higher β-sheet content. The addition of GO to SF matrix led to a slower release and a reduction of the burst release of RhB, the model compound. The release profile was well fitted to the Rigter–Peppas equation, from which the characteristic constant decreased and the diffusional exponent increased with increasing GO content but quickly leveled off when GO content was more than 1.0%. Degradation of the composites had little influence on the characteristic constant of RhB release, however, led to an increased diffusional exponent, which was more evident for the composites with higher β-sheet content.     

剪切对再生丝素蛋白溶液流动性能的影响

文章对再生丝素蛋白溶液以不同的速度在毛细管中的流动情况进行了研究,结果表明,再生丝素蛋白溶液的流动性对低挤出速率比较敏感,而对高挤出速率相对不敏感。且随着溶液浓度的增大,在同一挤出速率下流出相同质量溶液所需的时间增加。通过Raman测试表明经过毛细管的剪切作用可加速丝素分子从无规线团或α螺旋向β折叠构象的转变速度。     

Studies of electrospun regenerated SF/TSF nanofibers

The Bombyx mori silk fibroin/Tussah silk fibroin (SF/TSF) nanofibers with diameters between 300 and 3500 nm were prepared by electrospinning with the solvent HFIP. The average diameters of SF/TSF blend fibers increased from 404 to 1977 nm, with the increase of SF content in blend solutions, and the relationship between the average diameters of SF/TSF and SF content was proved to be linear correlation. Results from FTIR, TG-DTA and X-ray diffraction showed that the electrospun fibers were mainly β-sheet structure and, heterogeneous micro-structures. In particular, the presence of two different endothermic peaks at 300 and 360 °C in the TG-DTA curves may be ascribed to the thermal decomposition of SF and TSF. These results suggested that SF and TSF were still immiscible even dissolved in hexafluoroisopropanol (HFIP) after electrospinning and ethanol treatment. Moreover, the thermal decomposition temperature and enthalpy were improved with the blend of SF and TSF, else the SF/TSF nanofibers' moisture absorption was higher than the pure SF or TSF nanofibers. To study the cytocompatibility and cell behavior on the SF/TSF nanofibers, MSCs, VECs, and Neurons were seeded onto the nanofibers. Results indicated that the SF/TSF nanofibers promote cell attachment and spreading, suggesting that these nanofibers could be a candidate scaffold for blood vessel and nerve injury recovery.     

Acceleration effect of sericin on shear-induced β-transition of silk fibroin

Although silk sericin (SS) occupies 25% of silk protein, its importance has often been overlooked in the natural silk spinning process and in the formation of the crystalline structure of silk fibroin (SF). In this study, we elucidated the role of SS in the crystallization process of SF under shear using SF/SS blend solutions. In order to apply shear stress to the blend solution, a rotating glass rod was inserted into a glass tube filled with the solution and the shear rate was determined to be in the range of 598–724 s⁻¹. After shearing, SF aggregates were formed and the amount of the aggregates increased with shearing time. Additionally, it was observed that the aggregate formation and β-sheet transition of SF were enhanced when a proper amount of SS was in the blend solution. Consequently, the SS considerably contributes to the structural transition of SF under shear. The SS can improve the shear-induced β-sheet transition and crystallization of SF.     

Effect of chitosan on morphology and conformation of electrospun silk fibroin nanofibers

The electrospinning of silk fibroin(SF)/chitosan(CS) blends with different composition ratios was performed with formic acid as a spinning solvent. The SF/CS blends containing up to the CS content of 30% could be electrospun into the continuous fibrous structure, although pure CS was not able to be electrospun into the fibrous structure. As-spun SF/CS blend nanofibers showed smaller diameter and narrower diameter distribution than pure SF nanofibers, and the diameter gradually decreased from 450 to 130 nm with the addition of CS in blends. However, at the blend compositions with above 40 wt% chitosan, the continuous SF nanofibers containing CS beads were produced. We also investigated the influence of the methanol treatment on the secondary structure of as-spun SF or SF/CS blend nanofibers by means of ATR-IR and solid-state CP-MAS ¹³C-NMR. Comparing with the pure SF nanofibers, the conformational change of the as-spun SF/CS blend nanofibers into β-sheet was faster because the CS with rigid backbone synergistically might promote the conformational transition of SF by an intermolecular interaction.     

Fabrication and intermolecular interactions of silk fibroin/hydroxybutyl chitosan blended nanofibers

The native extracellular matrix (ECM) is composed of a cross-linked porous network of multifibril collagens and glycosaminoglycans. Nanofibrous scaffolds of silk fibroin (SF) and hydroxybutyl chitosan (HBC) blends were fabricated using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) and trifluoroacetic acid (TFA) as solvents to biomimic the native ECM via electrospinning. Scanning electronic microscope (SEM) showed that relatively uniform nanofibers could be obtained when 12% SF was blended with 6% HBC at the weight ratio of 50:50. Meanwhile, the average nanofibrous diameter increased when the content of HBC in SF/HBC blends was raised from 20% to 100%. Fourier transform infrared spectra (FTIR) and (13)C nuclear magnetic resonance (NMR) showed SF and HBC molecules existed in hydrogen bonding interactions but HBC did not induce conformation of SF transforming from random coil form to β-sheet structure. X-ray diffraction (XRD) confirmed the different structure of SF/HBC blended nanofibers from both SF and HBC. Thermogravimetry-Differential thermogravimetry (TG-DTG) results demonstrated that the thermal stability of SF/HBC blend nanofibrous scaffolds was improved. The results indicated that the rearrangement of HBC and SF molecular chain formed a new structure due to stronger hydrogen bonding between SF and HBC. These electrospun SF/HBC blended nanofibers may provide an ideal tissue engineering scaffold and wound dressing.