Temperature/pH dual responsive microgels of crosslinked poly(N‐vinylcaprolactam‐co‐undecenoic acid) as biocompatible materials for controlled release of doxorubicin

Undecenoic acid functionalized thermo/pH responsive microgels, poly(N‐vinylcaprolactam‐co‐undecenoic acid) [poly(VCL‐co‐UA)], were synthesized by precipitation emulsion copolymerization. The microgels exhibit reversible thermo/pH responsive phase transition behavior, which can be tuned by varying the monomer feed ratio. The lower critical solution temperatures (LCSTs) of the materials are close to body temperature. As a result, when temperatures rise above ca. 37°C, a rapid thermal gelation process occurs, accompanied by a phase transition, resulting in expulsion of encapsulated compound. In vitro experiment evaluated its applicability as a drug carrier for controlled release of an anticancer agent (doxorubicin) and showed that the drug encapsulation efficiency (EE), releasing rate, and kinetics are dependent on the temperature and pH value as expected. Minimal cytotoxicity of the microgels was observed by a cytotoxicity assay using 3T3 fibroblast cells. Our finding suggests that the poly(VCL‐co‐UA) based microgels may be considered a promising candidate for temperature or pH‐controlled delivery of anticancer drugs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41146.     

Thermo‐ and pH‐responsive microgels for controlled release of insulin

Microgel particles were prepared, made of hydroxypropylcellulose‐graft‐(acrylic acid) (HPC‐g‐AA) and acrylic acid(AA). The particles undergo reversible volume phase transitions in response to both pH and temperature changes while keeping the inherent properties of PAA and HPC‐g‐AA. Dynamic light scattering measurements reveal that the average hydrodynamic radius and hydrodynamic radius distributions of the microgel particles depend on temperature and pH. The microgels exhibit excellent pH sensitivity and a higher swelling ratio at higher pH in aqueous solution. In vitro release study shows that the amount of insulin released from the microgels is less at pH = 1.2 than at pH = 6.8. The results indicate that the resultant microgels seem to be of great potential for intelligent oral drug delivery. Copyright © 2012 Society of Chemical Industry     

Atmospheric Photopolymerization of Acrylamide Enabled by Aqueous Glycerol Mixtures: Characterization and Application for Surface‐Based Microfluidics

Polyacrylamide usually is the material of choice for electrophoretic separation in slab gels, capillaries, and microfluidic devices. So far its polymerization requires anaerobic environments because oxygen impurities inhibit or even terminate the polymerization reaction of acrylamide. Here, it is demonstrated that gel precursor solutions with glycerol contents above 20 vol% enable direct atmospheric photopolymerization of acrylamide with no need for sealing or degassing the solution in advance. The positive effect of glycerol on the polymerization reaction is proven by simulation‐validated electron paramagnetic resonance measurements. Nuclear magnetic resonance reveals that glycerol does not interfere with the reaction indicating that the observed enhancement in polymerization is owed to the low oxygen solubility of aqueous glycerol mixtures. Glycerol concentrations of >60 vol% in the gel precursor solution enable complete polymerization of volumes down to 5 nL within less than 5 s. This enables using liquid handling robots to fabricate channel‐free open microfluidic structures of solid polyacrylamide hydrogel in a low‐cost automated manner in a standard lab environment.     

Novel approach for attapulgite/poly(acrylic acid) (ATP/PAA) nanocomposite microgels as selective adsorbent for Pb(II) Ion

A novel approach was developed for the preparation of the attapulgite/poly(acrylic acid) (ATP/PAA) nanocomposite microgels via the “one-pot” inverse suspension radical polymerization of acrylic acid (AA) with the multi-functionalized attapulgite nanorods (org-ATP) as the sole crosslinker. The parameters of the feeding ratio of the functional attapulgite (org-ATP) nanorods and AA (org-ATP/AA), oil (liquid paraffin)–water ratio, and feeding ratios of dispersing agent (sodium dodecyl benzene sulfonate (SDBS)) and initiator (ammonium persulfate (APS)) were optimized via 4-Variable 3-Level Orthogonal experiments. Under the optimized preparation condition, more than 85% of the monomer AA had been grafted onto the org-ATP nanorods to form the 3-dimensional network of the ATP/PAA nanocomposite microgel. The ATP/PAA nanocomposite microgel exhibited better mechanical stabilities (resistance to pressure and resistance to agitation) and selective adsorption to heavy metal ions, especially to Pb²⁺. The adsorbed Pb²⁺ ion could be completely eluted with HCl solution. The better mechanical stability and regeneration make it potential adsorbent for the heavy metal contaminated water.     

Preparation and characterization of surfactant‐free stimuli‐sensitive microgel dispersions

A surfactant‐free method to produce responsive polymer microgels is introduced. As an example, poly(methacrylic acid) hydrogels with varying crosslinking density have been synthesized in bulk and then chopped using a high shear mechanical cutter to form microgel particles dispersed in water. The mechanical cutting technique enables the concentration and particle size distribution of the microgel suspensions to be easily controlled, therefore making the rheology of the suspensions tuneable. The particle size distribution of the dispersions, characterized using light scattering, was dependent on the speed and duration of mechanical cutting. The particle size distribution also depended on the degree of crosslinking of the hydrogel. The higher the crosslinking density, the lower the average mean diameter of the resulting microgel particles. The lower the crosslinking density of the hydrogel, the larger the difference between the maximum and minimum particle size. The time to complete swelling of the particles upon change in pH was measured to be up to 45 s, depending on the particle size. The rheology of the resulting suspensions as a function of pH was investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 104: 1912–1919, 2007     

温敏性微凝胶对蛋白质和酶的吸附性能

用微乳液聚合方法以N-异丙基丙烯酰胺为单体合成了温敏性微凝胶聚N-异丙基丙烯酰胺(PNIPAM),研究了其对两种蛋白质和两种酶的吸附性能,测定了吸附等温线和温度对吸附量的影响。结果表明,微凝胶在低临界溶解温度(LCST)附近吸附蛋白质和酶的量有一突跃,例如在LCST前后,1 g纳米颗粒吸附的酪蛋白的质量分别为225 mg和415 mg;吸附的枯草杆菌蛋白酶的质量分别为12 000U/mg和27 500 U/mg。蛋白质和酶是通过物理吸附作用结合到PNIPAM微凝胶上,可以用调节温度的方法,来控制温敏微凝胶对蛋白质和酶的吸附与脱附。     

食品微凝胶的特性与应用研究进展

食品微凝胶是指尺寸在微米及亚微米量级,由天然生物大分子构成的具有一定凝胶网络状结构的胶体粒子。由于材料的多样性和尺寸效应,微凝胶表现出结构稳定、溶胀响应、界面活性、流变特性等一系列特殊的性质,受到食品科学研究领域越来越多的关注,在食品乳化、食品功能性物质荷载与递送、质构调节等方面具有广泛应用前景。本文主要综述了食品类微凝胶的材料、制备方法、基本性质及其在食品领域中应用的最新研究进展,旨在为微凝胶在食品领域中的应用提供理论依据和实际指导。     

pH条件对肌原纤维蛋白乳液微凝胶性质的影响

肌原纤维蛋白乳液微凝胶是在加热肌原纤维蛋白乳状液过程中同时施加剪切,导致变性蛋白质聚集在乳状液滴上所形成的离散球形颗粒。通过测定不同pH条件下制备的肌原纤维蛋白乳液微凝胶流变行为及微观结构,研究pH对其流变性质的影响。结果表明：在强酸性条件及接近其等电点时,乳液微凝胶的粒径大于其他pH范围。不同pH条件下的乳液微凝胶均为非牛顿流体,具有假塑性流体特征,pH的变化不会改变其流体类型。其黏度随pH的升高呈现先减小后增大的趋势,pH为6时,在低频率扫描时呈现最高的黏弹性,触变性也最好。剪切恢复力测试中,微凝胶颗粒的结构受到一定程度的破坏,其中pH为5时恢复性最好。