Reactive and stimuli-responsive maleic anhydride containing macromers – multi-functional cross-linkers and building blocks for hydrogel fabrication

Macromers with functional groups that allow for chemical derivatization, polymerization reactions or impart specific physico-chemical properties are functional building blocks for polymeric systems used in different biomedical applications. With this motivation, a series of oligomeric macromers was synthesized by free radical polymerization of maleic anhydride (MA) with N-isopropylacrylamide (NiPAAm) and pentaerythritol diacrylate monostearate (PEDAS). This chemical design provides anhydride groups for effective reactivity of the macromers with amines and other nucleophiles, copolymerized NiPAAm for temperature responsiveness and lipophilic stearate domains for increased hydrogel stability. Macromers were synthesized with different MA co-monomer feeds and oligomeric molecules (Mn below 5000 Da) were obtained with MA contents between 7% and 27% as determined by titration. The fraction of chemically intact anhydrides was calculated to range from 75% to 80%. The ability of the macromers to cross-link di- or oligovalent amines as a function of MA content was investigated rheologically. It was also demonstrated that monovalent amines, e.g. aminofluorescein, could be grafted to the macromer chain utilizing only a fraction of the anhydride functionalities. The derivatized macromers could still participate in cross-linking reactions due to the remaining anhydrides. Temperature sensitivity was shown for aqueous solutions of macromers with fully dissociated anhydride groups. The solutions were additionally responsive to changes in calcium ion concentration and pH. Extracts from macromer cross-linked polyether hydrogels showed no toxicity on L929 fibroblasts.The macromers have perspective as biocompatible cross-linkers for hydrogel fabrication from various biomacromolecules with the opportunity to decorate the gels with monoamine molecules that alter the biological or physico-chemical properties.     

Improvement of poly(vinyl alcohol)/poly(vinylpyrrolidone) blended hydrogel by radiation crosslinking

1IntroductionHydrogelisapolymericmaterial(syntheticornaturaJ)whichswellswhenplacedincontactwithwaterbutisnotsolubleandhastheabililtytoretainwaterwithinitsstructare.InIecentyears,muchattentionhasbeenfocusedontheresearchanddevelopmentofthepolymerhydIogelsforbiomaterials,suchascontactlenses,wounddressing,enzymeimmunoassay,cathetersanddIugdeliverysystems[1~3].Adressingisoftencoveredonthewotmdtoaccelerateitshealing.TheIearetwokindsofdiessings:drytypeandwettype.Ithasbeenreportedthatheallngwithawe…     

Microporous thermally sensitive hydrogels based on hydroxypropyl cellulose crosslinked with poly-ethyleneglicol diglycidyl ether

New microporous thermally sensitive hydrogels were prepared by crosslinking hydroxypropylcellulose (HPC) with poly-ethyleglicol diglycidyl ether. The crosslinking reaction was carried out in heterogeneous liquid crystalline phase. Phase separation was obtained at room temperature by using the mixed solvent water/dimethylsulfoxide (DMSO). A study of phase equilibrium for the ternary system HPC/water/DMSO is reported. Hydrogels obtained from heterogeneous conditions show a porous structure with interconnected channels characterized by high solvent adsorption rate, while gels obtained from homogeneous solutions show a compact structure. The hydrogels have thermally sensitive behaviour, swelling at low temperature and contracting at high temperature. A thermal cycle corresponding to a reversible process of solvent absorption and deabsorpion is illustrated.     

疏水缔合水凝胶对CH4的储气性能研究

以丙烯酰胺（AM）为亲水单体,与两种单体（丙烯酸十八酯C18、两性单体二甲基乙酰胺DMAC）、三种表面活性剂（十二烷基硫酸钠SDS、四丁基溴化铵TBAB、十六烷基三甲基溴化铵CTAB）采用自由基溶液聚合法制备得到5种疏水缔合水凝胶,并测量了5种水凝胶对CH4的储气性能及吸水性能。结果表明,两种表面活性剂（TBAB、CTAB）的添加,对水凝胶的储气性能有明显的影响,其中,水凝胶HC⁃SDS/TBAB对CH4的储气性能最好;两种表面活性剂的添加,对水凝胶的溶胀率也存在明显的影响,添加有两种表面活性剂的水凝胶溶胀性能明显低于单一添加SDS的水凝胶溶胀性能。     

An organic hydrogel film with micron-sized pillar array for real-time and indicator-free detection of Zn

A hydrogel sensing film for a real-time and indicator-free detection of Zn²⁺ is developed by embedding a fluorescent indicator 11,16-bis(phenyl)-6,6,21,21-tetramethyl-m-benzi-6,21-porphodimethene in a hydrogel host poly(2-hydroxyethyl methacrylate). The sensing film shows high stability and selectivity to Zn²⁺. The sensitivity of the sensing film is increased by fabricating a micron-sized pillar array on the surface of the sensing film to increase the surface area. For Zn²⁺ concentrations of 10⁻⁴ and 10⁻³ M, the response time is 30 and 3 s, respectively.     

Oxygen transport in composite mediated biocathodes

A numerical simulation of an enzyme-catalyzed oxygen cathode is presented and applied to the analysis of transport limitations in operating electrodes, with the goal of predicting the limits of obtainable cathode current density. Based on macrohomogeneous and thin-film theories, and accounting for dual-substrate enzyme kinetics, the one-dimensional model predicts a maximum current density of about 9.2 mA cm⁻² at 0.6 V (SHE) for a 300 μm thick electrode operating oxygen-saturated pH 5 buffer at 37 °C and relying on diffusion of dissolved oxygen alone. However, by introducing gas-phase diffusive transport, or alternatively a convective, flow-through approach, the model predicts that electrodes of identical thickness may provide current densities up to 60 mA cm⁻² in air and exceeding 100 mA cm⁻² in pure O₂. Such performance would move enzyme electrodes closer to practical implementation in implantable power devices and other low-temperature fuel cells such as direct methanol fuel cells.     

Factors influencing the prescribing of hydrogel contact lenses

Despite the current market popularity of silicone hydrogel contact lenses, conventional hydrogel lenses still represent a significant proportion of the overall contact lens market. Data gathered from annual UK contact lens fitting surveys over the past 13 years indicate that 64% of hydrogel lenses prescribed during this period were of low/medium water content (≤60% water). Whereas, in the past, practitioners would choose the water content of a hydrogel lens to meet specific clinical needs, this choice appears today to be largely governed by product availability.     

Bilayer hydrogel assembly

The combination of two hydrogel layers based on photo-cross-linkable poly(dimethyl acrylamide) (PDMAAm) as base layer and poly(N-isopropyl acrylamide) (PNIPAAm) as top layer forms a bilayer assembly where, the base layer is highly swollen and the top layer shows temperature responsive swelling. Characterization was done by a combination of surface plasmon resonance spectroscopy and optical waveguide spectroscopy as well as atomic force microscopy. The PDMAAm and PNIPAAm within the bilayer assembly retain their swelling behavior, which they showed as a separate layer. Due to the presence of the photo-cross-linker such bilayer films can be patterned to develop surfaces with different properties at different regions.     

辐射制备甲基丙烯酸β-羟乙酯(HEMA)水凝胶的动力学研究

本文主要介绍辐射合成PHEMA水凝胶动力学进程的一些研究结果:(1)在动力学进程中,首先单体HEMA被聚合为聚合物的溶胶,当聚合率达到约20％之后才开始产生凝胶。(2)这一聚合过程是按自由基机构进行:V_0∞I~(0.6)。(3)完成这一聚合—交联过程所需剂量很小,为不到1×10~4Gy即可得到高于90％的凝胶含量的水凝胶产物。(4)所得水凝胶具有优良的物理机械性能:吸水率:20～70％,透氧系数:(ηO_2):10~(-11)～10~(-9)ml·cm/cm~2·s·cmHg,ηCO_2:10~(-11)～10~(-9)ml·cm/cm~2·s·cmHg;抗张强度5～30kg/cm~2,延长率:100～300％。     

Temperature-sensitive hydrogel modified by polymerizable liquid crystal AAc-Brij-58: Optical and protein adsorption/desorption behaviors

To avoid template-like action of polyoxyethylene 20 cetyl ether (Brij-58) in hydrogel matrix, a polymerizable liquid crystal AAc-Brij-58 based acrylic acid (AAc) and Brij-58, and poly(NIPAm-co-AAc-Brij-58) (ACHX) hydrogels based on N-isopropylacrylamide (NIPAm) and AAc-Brij-58 were synthesized by esterification and free-radical polymerization. The chemical structures of resulting ACHX hydrogels were confirmed by FTIR and ¹H NMR. The optical property of ACHX pre-polymerization solution was monitored by ultraviolet–visible spectrophotometry (UV/Vis). The pore structure was observed by scanning electron microscopy (SEM). The adsorption and desorption behaviors of Bovine Serum Albumin (BSA) were investigated by temperature-oscillating between 37 °C and 25 °C. The result shows that AAc-Brij-58 and ACHX hydrogels have been successfully synthesized. With increasing mass percent of AAc-Brij-58/NIPAm from 0 to 10 wt%, the transparency of ACH01-10 hydrogel decreases to 0 at 20, 17, 14, 12 and 16 min, respectively. The interior of ACHX hydrogels presents honeycomb structure with thick pore wall with pore size from 120 to 600 μm, but shows vent-like structure on the outer surface after copolymerization by AAc-Brij-58. The adsorption and desorption of ACHX hydrogels exhibit reversible temperature oscillation responsibility between 37 °C and 25 °C. As mass percent of AAc-Brij-58/NIPAm is 1 wt%, ACH01 hydrogel presents highest adsorbed BSA amount, about 1090 ± 24 mg/g at 37 °C. After desorption at 25 °C, columniform BSA aggregates on the surface of ACHX hydrogels were not observed.