甲基纤维素温敏水凝胶的凝固及体外释药特性

为研究新型反向温敏凝胶在植入型药物释放系统中的应用,通过粘度跟踪法考察了“甲基纤维素聚乙二醇柠檬酸钠”三组分体系在体温下的凝固特性,分析了凝胶配方对于凝固过程的影响;以5-氟尿嘧啶为模型药物,研究了凝胶配方对体外释放特性的影响。结果表明,甲基纤维素使体系具有反向温敏性,高分子量聚乙二醇具有加速胶凝的作用,柠檬酸钠的盐析作用能降低成胶温度。通过调整凝胶配方,能使体系在体温下在10m in内迅速凝固,并使5-氟尿嘧啶的释放时间达到24 h以上。     

Rapidly recovering hydrogel scaffolds from self-assembling diblock copolypeptide amphiphiles

Protein-based hydrogels are used for many applications, ranging from food and cosmetic thickeners to support matrices for drug delivery and tissue replacement. These materials are usually prepared using proteins extracted from natural sources, which can give rise to inconsistent properties unsuitable for medical applications. Recent developments have utilized recombinant DNA methods to prepare artificial protein hydrogels with specific association mechanisms and responsiveness to various stimuli. Here we synthesize diblock copolypeptide amphiphiles containing charged and hydrophobic segments. Dilute solutions of these copolypeptides would be expected to form micelles; instead, they form hydrogels that retain their mechanical strength up to temperatures of about 90 degrees C and recover rapidly after stress. The use of synthetic materials permits adjustment of copolymer chain length and composition, which we varied to study their effect on hydrogel formation and properties. We find that gelation depends not only on the amphiphilic nature of the polypeptides, but also on chain conformations--alpha-helix, beta-strand or random coil. Indeed, shape-specific supramolecular assembly is integral to the gelation process, and provides a new class of peptide-based hydrogels with potential for applications in biotechnology.     

生物还原响应的酶交联可注射水凝胶

可注射水凝胶作为生物材料被广泛用于生物医学领域. 合成了含有二硫键的葡聚糖衍生物(Dex-SS-PA), 使用辣根过氧化酶化学交联制备出新型的生物还原响应的可注射水凝胶. 系统研究了这些水凝胶的物理化学属性, 包括成胶时间、胶含量及降解性, 同时使用生死染色实验和噻唑蓝比色法实验评价了它们的细胞生物相容性. 研究结果表明, 葡聚糖的分子量越大、根皮酸的取代度越高、Dex-SS-PA 的浓度越大, 获得的水凝胶成胶时间越短、胶含量越高. 在还原环境中, Dex-SS-PA 水凝胶能够被降解. 此外, 这些水凝胶没有明显的细胞毒性. 因此, 这类新的水凝胶预示着较好的生物医学应用前景.     

聚N-异丙基丙烯酰胺水凝胶的微波合成及其药物控释性研究

用微波引发合成了聚N-异丙基丙烯酰胺,并制成整体型释放器,对非水溶性药物阿昔洛韦在不同温度响应时的药物缓释行为进行了研究.     

A reversibly antigen-responsive hydrogel.

Stimuli-responsive hydrogels that undergo abrupt changes in volume in response to external stimuli such as pH, temperature and solvent composition have potential applications in biomedicine and the creation of 'intelligent' materials systems, for example as media for drug delivery, separation processes and protein immobilization. Hydrogels have been reported that respond to pH, temperature, electric fields and saccharides. For some biomedical applications it would be very useful to have a material whose swelling response was dictated by a specific protein. Here we report such a material, which swells reversibly in a buffer solution in response to a specific antigen. The hydrogel was prepared by grafting the antigen and corresponding antibody to the polymer network, so that binding between the two introduces crosslinks in the network. Competitive binding of the free antigen triggers a change in gel volume owing to breaking of these non-covalent crosslinks. In addition, we show that the hydrogel displays shape-memory behaviour, and that stepwise changes in antigen concentration can induce pulsatile permeation of a protein through the network.     

Novel enzymatically crosslinked chitosan hydrogels with free-radical-scavenging property and promoted cellular behaviors under hyperglycemia

The impairment of regenerative processes induced by high blood-glucose level (hyperglycemia) and excessive reactive oxygen species (ROS) contributes to the diabetic complication progression and development. In this study, an injectable, in situ crosslinkable chitosan hydrogel with ROS-scavenging capability was developed by conjugating gallic acid onto the chitosan backbone (CGA). We hypothesized that gallic acid serves as both antioxidant and crosslinking moieties to form hydrogel in situ by means of enzymatic crosslinking with horseradish peroxidase (HRP). The rapid gelation (from 30 s) was observed by vial tilting. The mechanical properties and microstructures of CGA hydrogels can be well controlled by varying the concentrations of H₂O₂. The ROS-scavenging ability of these CGA hydrogels was demonstrated against DPPH radical, hydroxyl radical, and total reducing power. Notably, in an in vitro hyperglycemia environment, CGA hydrogels significantly improved the proliferation and migration of human dermal fibroblast cells, which are closely related to diabetic wound healing. These results suggest that CGA hydrogels have potential as advanced materials for the treatment of diabetes-related diseases via attenuating the excessive ROS production and improving cellular behaviors.     

智能海藻酸钙/PNIPAAm互穿网络水凝胶微囊制备研究

以海藻酸钙凝胶为聚合模板，过硫酸铵/偏重亚硫酸钠氧化还原引发剂体系、自由基水溶液法聚合制备了温度敏感和pH敏感的海藻酸钙/聚N异丙基丙烯酰胺（CA/PNIPAAm）互穿网络水凝胶微囊。并研究了引发剂用量、单体量、单体/海藻酸钠配比、缓冲液pH值等因素对该互穿智能水凝胶温度敏感和pH敏感性的影响。结果表明：该互穿凝胶微囊对pH/温度具有敏感溶胀性，可望作为口服药物缓释制剂的载体。     

Highly stretchable and tough hydrogels

Hydrogels are used as scaffolds for tissue engineering, vehicles for drug delivery, actuators for optics and fluidics, and model extracellular matrices for biological studies. The scope of hydrogel applications, however, is often severely limited by their mechanical behaviour. Most hydrogels do not exhibit high stretchability; for example, an alginate hydrogel ruptures when stretched to about 1.2 times its original length. Some synthetic elastic hydrogels have achieved stretches in the range 10-20, but these values are markedly reduced in samples containing notches. Most hydrogels are brittle, with fracture energies of about 10?J?m(-2) (ref. 8), as compared with ～1,000?J?m(-2) for cartilage and ～10,000?J?m(-2) for natural rubbers. Intense efforts are devoted to synthesizing hydrogels with improved mechanical properties; certain synthetic gels have reached fracture energies of 100-1,000?J?m(-2) (refs 11, 14, 17). Here we report the synthesis of hydrogels from polymers forming ionically and covalently crosslinked networks. Although such gels contain ～90% water, they can be stretched beyond 20 times their initial length, and have fracture energies of ～9,000?J?m(-2). Even for samples containing notches, a stretch of 17 is demonstrated. We attribute the gels' toughness to the synergy of two mechanisms: crack bridging by the network of covalent crosslinks, and hysteresis by unzipping the network of ionic crosslinks. Furthermore, the network of covalent crosslinks preserves the memory of the initial state, so that much of the large deformation is removed on unloading. The unzipped ionic crosslinks cause internal damage, which heals by re-zipping. These gels may serve as model systems to explore mechanisms of deformation and energy dissipation, and expand the scope of hydrogel applications.     

Helical self-assembled polymers from cooperative stacking of hydrogen-bonded pairs

The double helix of DNA epitomizes this molecule's ability to self-assemble in aqueous solutions into a complex chiral structure using hydrogen bonding and hydrophobic interactions. Non-covalently interacting molecules in organic solvents are used to design systems that similarly form controlled architectures. Peripheral chiral centres in assemblies and chiral side chains attached to a polymer backbone, have been shown to induce chirality at the supramolecular level, and highly ordered structures stable in water are also known. However, it remains difficult to rationally exploit non-covalent interactions for the formation of chiral assemblies that are stable in water, where solvent molecules can compete effectively for hydrogen bonds. Here we describe a general strategy for the design of functionalized monomer units and their association in either water or alkanes into non-covalently linked polymeric structures with controlled helicity and chain length. The monomers consist of bifunctionalized ureidotriazine units connected by a spacer and carrying solubilizing chains at the periphery. This design allows for dimerization through self-complementary quadruple hydrogen bonding between the units and solvophobically induced stacking of the dimers into columnar polymeric architectures, whose structure and helicity can be adjusted by tuning the nature of the solubilizing side chains.     

Preparation and Characterization of pH-Sensitive Polyvinyl Alcohol Hydrogel for Cancer Therapy

Hydrogel has emerged as an excellent carrier platform for smart drug delivery and effective cancer treatment due to its high water content, good biocompatibility and sufficient mechanical properties. In this work,the DOX-loaded polyvinyl alcohol（ PVA）hydrogel was prepared by freeze-thawing technique. The swelling test and the mechanical properties of the pure PVA hydrogels were performed. In addition, the in vitro drug release profiles were examined and the in vitro antitumor efficiency against He La cells was also estimated. The results indicated that the resulting PVA hydrogels contained significant amounts of water and possessed good mechanical properties,and DOX-loaded PVA hydrogel exhibited a sustained and p H-responsive DOX release. The MTT assays also demonstrated that the released DOX could effectively inhibit the proliferation of He La cells. Thus,the cross-linked PVA hydrogel can be further developed as a promising platform for cancer therapy.     

Preparation of 3D graphene-based architectures and their applications in supercapacitors

Three dimensional (3D) graphene-based architectures such as 3D graphene-based hydrogels, aerogels, foams, and sponges have attracted huge attention owing to the combination of the structural interconnectivities and the outstanding properties of graphene which offer these interesting structures with low density, high porosity, large surface area, stable mechanical properties, fast mass and electron transport. They have been extensively studied for a wide range of applications including capacitors, batteries, sensors, catalyst, etc. There are several reviews focusing on the 3D graphene-based architectures and their applications. In this work, we only summarise the latest development on the preparation of 3D graphene-based architectures and their applications in supercapacitors, with emphasis on the preparation strategies.     

PDMAA/Clay纳米复合水凝胶的制备与性能

以无机黏土为交联剂,采用偶氮二异丁腈(AIBN)为引发剂制备了新型的聚N,N ＇-二甲基丙烯酰胺/黏土(PDMAA/Clay)纳米复合水凝胶,作为对比,采用过硫酸钾(KPS)为引发剂制备了相对应的水凝胶.对两种纳米复合水凝胶的结构、形态、溶胀行为和力学性能等进行了研究.试验表明,黏土的结晶结构均已被破坏,黏土规整的片层被剥离并在凝胶中无序分布,起到交联剂的作用.随着黏土含量的增加,水凝胶的溶胀速率和溶胀度降低.采用AIBN制备的PDMAA/Clay水凝胶具有更好的韧性及更高的断裂强度,其断裂伸长率可达1 800％以上,而KPS制备的水凝胶的断裂伸长率在1 200％左右.     

海藻酸-羧甲基壳聚糖/聚乙烯醇水凝胶的制备及对蛋白药物释放的探讨简

以牛血清白蛋白（BSA）为模型药物,制备了海藻酸-羧甲基壳聚糖（CMCS）/聚乙烯醇（PVA）复合水凝胶,考察了海藻酸水凝胶微球的粒径和微球在水凝胶基质中的分散性,分析了复合水凝胶基质的结构、溶解分数以及水凝胶在不同pH值下的溶胀率和药物释放。结果表明,药物的累积释放率（犆R）随pH值的升高而升高,当pH值为1．2时CR 为32％,当pH值为6．8时犆R 为53％,当pH值为8．0时CR 达到70％,表明该复合水凝胶的释药性能受pH值的影响较大。     

芘荧光探针跟踪纳米复合水凝胶的形成过程

采用阳离子型芘荧光探针芘甲胺基盐酸盐跟踪聚N-异丙基丙烯酰胺(PNIPAm)/锂藻土Laponite原位聚合制备纳米复合水凝胶的过程.首先通过提高Laponite分散液的离子强度,采用离心分离和紫外-可见光吸收光谱验证了荧光探针在Laponite片层上的吸附;然后通过跟踪吸附荧光探针的激基缔合物的荧光光谱,发现反应液在聚合反应开始20min后出现的乳白色不透明现象与体系中形成的PNIPAm链的不均匀分布相关.聚合生成的高分子链吸附在Laponite片层周围,占据了片层上一定的空间,使得吸附在Laponite片层上的荧光分子被挤压而靠近,造成荧光激基缔合物的出现,因此可以通过荧光光谱变化来推测纳米复合(NC)凝胶聚合过程中透光率的变化及生成的聚合物链与交联剂Laponite之间的相互作用,这为深入认识NC凝胶的交联结构提供了一种实验方法.     

自修复水凝胶的研究进展及油气田应用

针对自修复水凝胶能够模仿自然界中植物受损后从分子水平上对受损部位进行自修复的现象,对自修复水凝胶设计和合成基本原理进行了归纳总结。自修复水凝胶主要分为化学型自修复水凝胶和物理型自修复水凝胶。化学型自修复水凝胶大体上又可分为基于Diels-Alder加成反应的自修复水凝胶、基于可逆二硫键的自修复水凝胶和基于酰腙键的自修复水凝胶;物理型自修复水凝胶大体上可分为基于氢键作用的自修复水凝胶、基于主客体相互作用的自修复水凝胶和基于静电相互作用的自修复水凝胶等类型。自修复水凝胶不仅保留了传统水凝胶良好的吸水保水性、生物相容性等性能,而且其具有的自修复性能可以有效地延长材料的使用寿命、降低材料的使用成本。在此基础上,分析讨论了自修复水凝胶在油气田、生物医药等领域的潜在应用价值和应用情况,并对自修复水凝胶在油气田领域的发展趋势进行了展望。     

Redox modulated hydrogelation of a self-assembling short peptide amphiphile

Hydrogels resulting from the self-assembly of small peptides are smart nanobiomaterials as their nanostructuring can be readily tuned by environmental stimuli such as pH,ionic strength and temperature,thereby favoring their practical applications.This work reports experimental observations of formation of peptide hydrogels in response to the redox environment.Ac-I 3 K-NH 2 is a short peptide amphiphile that readily self-assembles into long nanofibers and its gel formation occurs at concentrations of about 10 mmol/L.Introduction of a Cys residue into the hydrophilic region leads to a new molecule,Ac-I 3 CGK-NH 2,that enables the formation of disulfide bonds between self-assembled nanofibers,thus favoring cross-linking and promoting hydrogel formation.Under oxidative environment,Ac-I 3 CGK-NH 2 formed hydrogels at much lower concentrations(even at 0.5 mmol/L).Furthermore,the strength of the hydrogels could be easily tuned by switching between oxidative and reductive conditions and time.However,AFM,TEM,and CD measurements revealed little morphological and structural changes at molecular and nano dimensions,showing no apparent influence arising from the disulfide bond formation.     

聚甲基丙烯酸/碳纳米管杂合水凝胶的制备、结构及溶胀性研究

通过自由基交联聚合的方法制得了新型的聚甲基丙烯酸/多壁碳纳米管(PMAA/MWCNT)杂合水凝胶。研究了碳纳米管含量对水凝胶的结构与溶胀性能的影响。实验结果表明,通过调节MWCNT的含量,可以使得PMAA/MWCNT杂合水凝胶表现出了更高的膨胀性和更强的pH敏感性。     

高强度聚N-异丙基丙烯酰胺-黏土纳米复合水凝胶的制备及表征

采用原位聚合方法制备出一种具有高强度、良好温度响应性的聚N-异丙基丙烯酰胺/黏土纳米复合水凝胶,并用红外光谱、扫描电镜、透射电镜对其结构进行了分析.测试结果表明,纳米黏土与聚合物分子链之间具有强的氢键作用,水凝胶具有均匀的多孔聚合物骨架,且黏土可均匀地分散在聚合物基体中.热力学测试结果表明,黏土的引入未对水凝胶热敏特性产生显著影响,即三种水凝胶均在35℃左右产生明显的相转变;同时,溶胀动力学测试结果表明,水凝胶样品在该温度下具有明显的去溶胀特性.机械性能测试结果表明,纳米黏土的加入,可显著提高水凝胶的机械性能.     

聚苯胺导电水凝胶基柔性应变传感器的制备

以蒙脱土改性聚丙烯酰胺水凝胶为基底,通过苯胺预渗透方法制备聚苯胺浓度梯度分布的聚苯胺/改性蒙脱土/聚丙烯酰胺（PANI/DCM/PAM）导电水凝胶（PDPG）,重点考察力学性能和应变传感性能。结果表明：壳聚糖改性蒙脱土的分散液稳定性明显提高;苯胺预渗透5 s、脱水5 h所得PDPG水凝胶的拉伸强度和断裂伸长率分别达到194 kPa和685%;改变苯胺预渗透时间可以调控PDPG水凝胶的导电性能和传感性能;当应变为0~400%时,PDPG水凝胶的灵敏度（GF）最高值为7.02。基于PDPG导电水凝胶的柔性应变传感器能够实现对人体全尺度运动的监测,并具有很好的循环稳定性。     

Selective assembly on a surface of supramolecular aggregates with controlled size and shape.

The realization of molecule-based miniature devices with advanced functions requires the development of new and efficient approaches for combining molecular building blocks into desired functional structures, ideally with these structures supported on suitable substrates 1-4.Supramolecular aggregation occurs spontaneously and can lead to controlled structures if selective and directional non-covalent interactions are exploited. But such selective supramolecular assembly has yielded almost exclusively crystals or dissolved structures 5; the self-assembly of absorbed molecules into larger structures 6-8, in contrast, has not yet been directed by controlling selective intermolecular interactions. Here we report the formation of surface-supported supramolecular structures whose size and aggregation pattern are rationally controlled by tuning the non-covalent interactions between individual absorbed molecules.Using low-temperature scanning tunnelling microscopy, we show that substituted porphyrin molecules adsorbed on a gold surface form monomers, trimers, tetramers or extended wire-like structures. We find that each structure corresponds in a predictable fashion to the geometric and chemical nature of the porphyrin substituents that mediate the interactions between individual adsorbed molecules.Our findings suggest that careful placement of functional groups that are able to participate in directed non-covalent interactions will allow the rational design and construction of a wide range of supramolecular architectures absorbed to surfaces.