水凝胶

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Temperature-sensitive hydrogels



Comb-type graft hydrogels of PNIPAAm: main chain of the cross-linked PNIPAAm contain smallmolecular-weight graft of PNIPAAm Under condition of gel collapse (above LCST), hydrophobic regions were developed in the pores of the gel resulting in a rapid collapse The materials had the ability to collapse from a fully swollen conformation in less than 20 minutes Gel without graft chain required up to a month to fully collapse Major promise for rapid and abrupt or oscillatory release of drugs, peptides, or proteins


按外界刺激的响应情况分类
• 传统水凝胶 • 智能水凝胶
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按高分子凝胶的响应性分类

pH响应性凝胶


温度响应性凝胶
光响应性凝胶


电场响应性凝胶
盐敏凝胶

压力敏感性凝胶
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pH- sensitive hydrogels


含有羟基或胺基 Most common ionic polymers: poly(acrylamide) PAAm, poly(acrylic acid)聚丙 烯酸 (PAA), poly(methacrylic acid) (PMAA)聚 甲基丙烯酸 , poly(diethylaminoethyl methacrylate)二乙基胺基乙基甲基丙烯酸酯 (PDEAEMA), and poly(dimethylaminoethyl methacrylate) (PDMAEMA) In acid medium, the gel did not swell significantly; in neutral or basic media, the gels swelled to a high degree because of ionization of the pendant acid group
n
poly(s odium a lginate)
poly(hya luronic acid)
透明质酸 Synthetic
O O n O n NH
海藻酸钠
O n
poly(lactic acid)
poly(N-is opropyl acrylamide)
poly(ethylene g lycol)
聚乳酸
Chemical and Physical crosslinking
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DNA水凝胶,无须交联剂
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互穿聚合物网络( interpenetrating polymer network, IPN)
由两种或两种以上聚合物通过网络互穿缠结而形成的一 类独特的聚合物共混物或聚合物合金。 IPN特有的强迫作用 能使两种性能差异很大或具有不同功能的聚合物形成稳定的 结合,从而实现组分之间性能的互补。同时IPN的特殊细胞状 结构、界面互穿、双相连续等结构形态特征,又使得它们在 性能或功能上产生特殊的协同作用,防止相分离,并极大地 提高了水凝胶的机械强度,并可以提高它的响应性。
+
Copolymerization Monomer Crosslinker Polymerization
Hydrogel network Vinyl group-containing water-soluble polymers
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高分子凝胶的制备
Physical crosslinking
• Cross-linking without chemical reaction • ionic interaction, hydrogen bonding, antigen-antibody interaction, supramolecular association • Ionic hydrogel
聚(N-异丙基丙烯酰胺) PNIPAAm
O = Susceptive to hydrolysis
聚氧乙烯


poly(vinyl alcohol)聚乙烯醇
poly(N-vinyl-2-pyrrolidone)聚(N-乙烯基-2-吡咯烷酮) (PNVP) poly(ethylene glycol)聚乙二醇 poly(hydroxyethyl metharylate) 聚甲基丙烯酸羟乙酯 (PHEMA) poly(acrylamide) 聚丙烯酰胺(PAAm) poly(acrylic acid)聚丙烯酸 (PAA) poly(methacrylic acid) 聚甲基丙烯酸 (PMAA)
Drug-loaded gel Change in temperature for gel collapse
Change in pH for gel swelling
Drug release through the swollen network
Drug release by the 26 squeezing action
• Molecular structures of environmental-sensitive hydrogels
(2) pH sensitive
hydrogel
CH2 H C C
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Applications of Hydrogels in Drug Delivery

Environment-Sensitive Hydrogels
• respond to environmental change : temperature, pH, specific molecule • reversible volume phase transition or sol-gel phase transition • “intelligent” or “smart” hydrogel
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Temperature-sensitive hydrogels

poly(N-isopropylacrylamide) and its copolymers nylon capsule grafted poly(IPAAm)
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Temperature-sensitive hydrogels



Poly(N-isopropyl acrylamide)聚异丙基丙烯酰胺 (PNIPAAm) LCST (lowest critical solution temp): 34.30C Below LCST: significant gel swelling occurred, Transition about this point as reversible LCST raised when PNIPAAm copolymer with small amount of ionic monomers Heterogeneous gels containing PNIAAm collapsed at significantly faster rate than homopolymer of PNIPAAm
A polymer gel is a threedimensional network swollen by a large amount of solvent. It has some properties between solutions and solids.
MD2 MD3 MD4
SEM micrograph of pHsensitive copolymer P(DEAM-co-MAA) hydrogels obtained at different pH values.
药物释放曲线
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Applications of Hydrogels in Drug Delivery
• Molecular structures of environmental-sensitive hydrogels
(1) Temperature sensitive hydrogel
CH2 H C C NH
MD5
MD6
pH = 9.5
MD7
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凝胶的性质
(1)触变性:物理凝胶受外力作用,网状结构被破 坏而变成流体,外部作用停止后,又恢复成半固体 凝胶结构,这种凝胶与溶胶相互转化的过程,称为 触变性。 (2)溶胀性:指凝胶吸收流体后自身体积明显增大 的现象,是弹性凝胶的重要特性。 (3)脱水收缩性:溶胀的凝胶在低蒸气压下保存, 流体缓慢地自动从凝胶中分离出来的现象。 (4)透过性:凝胶与流体性质相似,可以作为扩散 介质。
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pH敏感性
离子强度敏感性
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高分子凝胶的制备



起始原料: 单体(水溶或油溶单体) 聚合物(天然或合成聚合物) 单体和聚合物的混合物 两个前提: 主链或侧链上带有大量的亲水基团 适当的交联网络结构 制备方法: 单体的交联聚合 接枝共聚 其它交联或转化等
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高分子凝胶的制备
Chemical crosslinking Polymerization of water soluble monomers in the presence of bi- or multifunctional cross-linking agent
CH3 CH2 H C C NH CH2 O CH C O CH2CH2CH2CH3 CH3
n
O
n
O
CH H3C CH3
CH H3C
Poly(N-isopropylacrylamide) (PNIPAAm)
Poly(NIPAAm-co-butyl methacrylate) P(NIPAAm-co-BMA)
CH3 HO CH2 CH2 O x CH2 C H O
y CH2
CH2
O
x HΒιβλιοθήκη Baidu
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Poly(ethylene oxide-co-propylene oxide-co-ethylene oxide) (PEO-PPO-PEO)
Applications of Hydrogels in Drug Delivery
高分子凝胶
1
• gel 凝胶 • hydrogel 水凝胶 • soft & wet matter 软湿件 • intelligent or smart material 智能/灵巧材料 • fuzzy 模糊
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海参有一个特性:如 果有谁用手去碰一下它 柔软的身体,它就会一 下变得象木头一样坚硬, 但如果将它在手中紧捏 一会,它就会慢慢地溶 变成滑溜溜的液体从你 手中逃走。
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高分子凝胶的体积相转变
外界环境因子的变化
溶胀相
收缩相
体积不连续变化
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凝胶的分类
由非共价键交联形成,加热可以 • 物理凝胶: 拆散范德华力交联,使冻胶溶解。 是高分子链之间以化学键形成的 • 化学凝胶: 交联结构的溶胀体,加热不能溶 解也不能熔融。
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按来源分类
Natural
H O 2C HO O HO O OH HO O NH O O NaO 2 C HO OH O O n
3
content
凝胶的定义 凝胶的分类 凝胶的制备 凝胶的应用

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凝胶:
指溶胀的三维网状结构高分子,即聚合物分子间相互 连结,形成空间网状结构,而在网状结构的孔隙中又 填充了液体介质。由于液体与高分子网络的亲和性, 液体被高分子网络封闭在里面,失去了流动性,因此 凝胶能象固体一样显示出一定的形状。
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Bonding in hydrogels •Covalent •Ionic •Hydrogen bonding •Polypeptide complexation(e.g., coiled coils) •Hydrophobiceffect
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7
MD2
MD3
MD4
MD5
pH = 7.0
MD6
MD7
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