Synthesis and characterization of cholic acid‐containing biodegradable hydrogels by photoinduced copolymerization

A cholic acid (CA)‐containing biodegradable hydrogel (PLA‐PEG‐PLA‐co‐MACAH) was synthesized from the photoinduced copolymerization of a CA‐modified methacrylate monomer (MACAH), bearing a spacer of hexane‐1,6‐diol spacer between the methacryloyl and the cholanoate moieties, and a macromonomer (PLA‐PEG‐PLA‐DA), bearing two acryloyl end groups derived from a poly(lactic acid)‐b‐poly(ethylene glycol)‐b‐poly(lactic acid) triblock copolymer. The structure of MACAH was confirmed by FTIR, ¹H‐NMR, and MS. The hydrogel PLA‐PEG‐PLA‐co‐MACAH was characterized by scanning electron microscopy and X‐ray diffraction. The experiment results showed that the swelling ratios of the hydrogels decreased with the increase of the CA fraction. The investigation on the in vitro degradation of the hydrogel showed that the CA‐containing hydrogels degraded much slower than the hydrogels without CA component. The bioactivity of the synthesized hydrogels was assessed by the simulated body fluid method. The observed formation of hydroxyapatite on the scaffold of the hydrogels indicated that the hydrogels possess good bioactivity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

pH值／温度双重敏感淀粉水凝胶的合成与表征

首先合成具有功能性基团的淀粉马来酸酯（starch—MAH）,然后将starch—MAH与N-异丙基丙烯酰胺（NI-PA）共聚,合成出一种新型的淀粉水凝胶（starch—MAH／NIPA）。采用红外光谱仪（FT—IR）、扫描电镜（SEM）、差示扫描量热仪（DSC）、溶胀度测定以及体外药物释放试验,对水凝胶的结构和性能进行了表征。实验结果表明,该水凝胶具有良好的pH值、温度敏感性以及药物释放性能。     

Tissue Engineering: Scaffold‐Mediated 2D Cellular Orientations for Construction of Three Dimensionally Engineered Tissues Composed of Oriented Cells and Extracellular Matrices (Adv. Funct. Mater. 7/2009)

Various hydrogels, such as poly(γ‐glutamic acid) (γ‐PGA), gelatin (GT), alginic acid (Alg), and agarose (Aga), with 3D interconnected and oriented fibrous pores (OP gels) are prepared for 3D polymeric cellular scaffolds by using silica fiber cloth (SC) as template. After the preparation of these hydrogels with the SC templates, the latter are subsequently removed by washing with hydrofluoric acid solution. Scanning electron microscopy (SEM) clearly shows OP structures in the hydrogels. These various types of OP gels are successfully prepared in this way, independently of the crosslinking mechanism, such as chemical (γ‐PGA or GT), coordinate‐bonded (Alg), or hydrogen‐bonded (Aga) crosslinks. SEM, confocal laser scanning microscopy, and histological evaluations clearly demonstrate that mouse L929 fibroblast cells adhere to and extend along these OP structures on/in γ‐PGA hydrogels during 3D cell culture. The L929 cells that adhere on/in the oriented hydrogel are viable and proliferative. Furthermore, 3D engineered tissues, composed of the oriented cells and extracellular matrices (ECM) produced by the cells, are constructed in vitro by subsequent decomposition of the hydrogel with cysteine after 14 days of cell culture. This novel technology to fabricate 3D‐engineered tissues, consisting of oriented cells and ECM, will be useful for tissue engineering.     

导电水凝胶的制备及应用研究进展

导电水凝胶是一类将亲水性基质和导电介质有机结合的新型水凝胶,具有较高的柔韧性、可调的力学性能和优异的电化学性能,在柔性电子设备等领域具有广阔的应用前景。本文综述了导电水凝胶材料的研究前沿和动态,介绍了导电水凝胶的分类及制备方法,讨论了导电水凝胶的结构设计与性能,重点阐述了导电水凝胶材料的应用研究进展,归纳了导电水凝胶材料面临的问题与挑战,并展望了导电水凝胶材料的发展趋势,指出采用天然可再生资源为原料开发具有高导电性、力学性能稳定、耐极端温度、生物相容性和生物可降解的导电水凝胶将成为下一步研究重点,同时优化柔性电子装置、提高器件输出稳定性也将成为重要的研究方向之一。导电水凝胶的制备及应用研究将促进柔性电子功能材料领域的快速发展。     

交联壳聚糖薄膜及其水凝胶骨架片的制备与控释性能探讨

针对活性物质生物利用度提高这一热点问题,本文以三聚磷酸钠为交联剂,研究了交联壳聚糖薄膜的相关结构性能,探讨了交联壳聚糖水凝胶骨架片对活性物质的控释性能。壳聚糖来源广泛、生物相容性好,FT-IR-ATR分析显示,通过交联反应壳聚糖薄膜上引入一定基团,增强了薄膜的三维网络结构,从而使其具有一定的溶胀吸水性能。同时,交联后的壳聚糖薄膜耐酸性能明显提升,通过扫描电镜观察,交联壳聚糖薄膜经模拟胃液运转后表面仍然致密,无破损,具有作为活性物质载体材料的潜质。另外,以5-ASA为模型活性物质,通过压制得到交联壳聚糖水凝胶骨架片,在模拟释放实验中,5-ASA在胃液中0.5~1 h的释放率明显降低。研究结果显示,交联改性壳聚糖在活性物质传递及药物控释等领域都具有良好的应用前景。     

Drug Delivery Systems for the Treatment of Knee Osteoarthritis: A Systematic Review of In Vivo Studies

Many efforts have been made in the field of nanotechnology to improve the local and sustained release of drugs, which may be helpful to overcome the present limitations in the treatment of knee OA. Nano-/microparticles and/or hydrogels can be now engineered to improve the administration and intra-articular delivery of specific drugs, targeting molecular pathways and pathogenic mechanisms involved in OA progression and remission. In order to summarize the current state of this field, a systematic review of the literature was performed and 45 relevant studies were identified involving both animal models and humans. We found that polymeric nanoparticles loaded with anti-inflammatory drugs (i.e., dexamethasone or celecoxib) are the most frequently investigated drug delivery systems, followed by microparticles and hydrogels. In particular, the nanosystem most frequently used in preclinical research consists of PLGA-nanoparticles loaded with corticosteroids and non-steroidal anti-inflammatory drugs. Overall, improvement in histological features, reduction in joint inflammation, and improvement in clinical scores in patients were observed. The last advances in the field of nanotechnology could offer new opportunities to treat patients affected by knee OA, including those with previous meniscectomy. New smart drug delivery approaches, based on nanoparticles, microparticles, and hydrogels, may enhance the therapeutic potential of intra-articular agents by increasing the permanence of selected drugs inside the joint and better targeting specific receptors and tissues.     

Preparation and Swelling Behavior of Fast‐Swelling Superabsorbent Hydrogels Based On Starch‐g‐Poly(acrylic acid‐co‐sodium acrylate)

Summary: A novel fast‐swelling porous superabsorbent hydrogel was prepared by grafting acrylic acid onto corn starch through free‐radical polymerization in aqueous solution using N,N′‐methylenebisacrylamide as a crosslinker, ammonium persulfate as an initiator, sodium dodecyl sulfate and p‐octyl poly(ethylene glycol)phenyl ether as pore‐forming agents. The graft polymerization and surface morphology of the porous superabsorbents were characterized by FTIR and SEM. The results indicate that the porous superabsorbents were endowed with higher equilibrium water absorbency and faster swelling rate (they needed only 10 min to reach 90% of their equilibrium water absorbency) compared with the nonporous superabsorbents. The dewatering method employed had a significant influence on the swelling behavior of the superabsorbents and dewatering agents were useful to preserve the pores formed during the polymerization process.

The equilibrium water absorbency in distilled water, for the porous and non‐porous starch‐g‐poly(acrylic acid‐co‐sodium acrylate) superabsorbent hydrogels dried through different procedures.     

Preparation and characterization of cotton fibers coated with AA-IA hydrogel containing silver/graphene or graphene oxide nanoparticles

This study presents the fabrication and characterization of cotton textile fibers coated with hydrogels containing silver and Graphene or Graphene Oxide nanoparticles using 1-hexyl-3-methyl-imidazolium (HMIMPF6) ionic liquid (IL) as carbon filler dispersant. Acrylic acid/Itaconic acid (AA-IA) hydrogels are synthesized by polymerizing an acrylic acid-itaconic acid aqueous (80/20 v/v) solution and mixed with 2-2-Azobis (2-methylpropionamide) diclorohydrate, and N,N´-methylenbis (acrylamide). Then silver nanoparticles are generated throughout the hydrogel networks using in situ method by incorporating the silver ions and subsequent reduction with sodium borohydride. Then a cotton textile fiber substrate was coated with this hydrogel. Finally, graphene or graphene oxide was added to the textile substrate already impregnated with hydrogel and silver nanoparticles. In order to favor the dispersion of the carbon nano-structures in the system, an IL was used. The influence of these nanocomposite hydrogels on the properties of textile fiber were investigated by infrared spectroscopy (ATR), scanning electron microscopy (SEM), inductively coupled plasma mass spectroscopy (ICP) and antibacterial tests against Staphylococcus aureus (Gram positive) and Escherichia coli (Gram negative). The effect of each and combined fillers dispersion on antimicrobial properties were determined. Cotton fibers coated with hydrogel containing silver nanoparticles and graphene showed better results when the ionic liquid was used. Graphene showed greater antimicrobial efficiency than graphene oxide. It was proved that the textiles coated with hydrogels containing these fillers had an excellent antibacterial ability and are a good option to be used for medical applications such as wounds and burns dressing.     

Site‐Specific Oxidation‐Induced Stiffening and Shape Morphing of Soft Tough Hydrogels

Living biological tissues are made of structures with properly defined mechanical properties (toughness and stiffness) toward specific biological functions. Herein, a chemical manipulation strategy is developed to locally vary the oxidation state of Fe ions from divalent to trivalent in the tough hydrogels. The resultant trivalent ionically cross‐linked networks become less flexible and lead to a significant enhancement of the stiffness of the tough hydrogels. The mechanical strengthening of Fe²⁺/Ca²⁺‐alginate/polyacrylamide tough hydrogels is demonstrated by the oxidation with ammonium persulfate (APS). Moreover, by applying surface patterning, the mechanical properties of the tough hydrogels are spatially stiffened and thus can serve as anisotropic elements to guide the shape morphing of tough hydrogels into complex 3D structures. This method opens up a simple strategy not only to dynamically vary the mechanics of tough hydrogels, both in bulk and locally from prefabricated soft tough hydrogels, but also toward their shape morphing behaviors on demand.