温敏型智能化靶向式药物载体研究(Ⅰ)--具有温敏开关的多孔膜

研究了膜孔内接枝聚异丙基丙烯酰胺(PNIPAM)"开关"的温敏型智能膜的制备,并对其进行了温度感应开关性能实验.实验中采用等离子体接枝填孔聚合法将PNIPAM接枝在多孔平板膜的膜孔中,结果表明,这种接枝了PNIPAM"开关"的多孔膜具有温度感应特性,其利用膜孔内PNIPAM接枝链的膨胀-收缩特性实现了感温性开关性能.当环境温度低于PNIPAM的低临界溶解温度(LCST)时,膜孔内PNIPAM分子链膨胀而使膜孔呈"关闭"状态;而当环境温度高于LCST时,PNIPAM分子链变为收缩状态而使膜孔"开启".温敏开关的LCST可通过添加丙烯酰胺(AAM)与异丙基丙烯酰胺(NIPAM)共聚来调节,AAM与NIPAM共聚开关的LCST随AAM添加量的增加而单调上升.     

温敏型智能化靶向式药物载体研究(Ⅱ)-具有温敏开关的微囊

采用环境感应式微囊作为智能化靶向式药物载体，可以实现药物的定点、定时、定量控制释放。本文研究了膜孔内接枝聚异丙基丙烯酰胺(PNIPAM)“开关”的温敏型控制释放微囊载体的制备，并对其进行了温度感应控释性能实验。实验中采用界面聚合法制备聚酰胺多孔微囊，然后利用等离子体接枝填孔聚合法将PNIPAM接枝在微囊壁的膜孔中。研究结果表明，这种接枝了PNIPAM“开关”的微囊具有温度感应特性，其利用膜孔内PNIPAM接枝链的膨胀一收缩特性实现了感温性控制释放。当环境温度低于PNIPAM的低临界溶解温度(LCST)时，膜孔内PNIPAM分子链膨胀而使膜孔呈“关闭”状态，从而限制囊内溶质分子通过，于是释放速率慢；而当环境温度高于LCST时，PNIPAM分子链变为收缩状态而使膜孔“开启”，为微囊内溶质分子的释放敞开通道，于是释放速率快。     

温敏型智能化靶向式药物载体研究(II)——具有温敏开关的微囊

采用环境感应式微囊作为智能化靶向式药物载体 ,可以实现药物的定点、定时、定量控制释放。本文研究了膜孔内接枝聚异丙基丙烯酰胺 (PNIPAM)“开关”的温敏型控制释放微囊载体的制备 ,并对其进行了温度感应控释性能实验。实验中采用界面聚合法制备聚酰胺多孔微囊 ,然后利用等离子体接枝填孔聚合法将PNIPAM接枝在微囊壁的膜孔中。研究结果表明 ,这种接枝了PNIPAM“开关”的微囊具有温度感应特性 ,其利用膜孔内PNI PAM接枝链的膨胀 收缩特性实现了感温性控制释放。当环境温度低于PNIPAM的低临界溶解温度 (LCST)时 ,膜孔内PNIPAM分子链膨胀而使膜孔呈“关闭”状态 ,从而限制囊内溶质分子通过 ,于是释放速率慢 ;而当环境温度高于LCST时 ,PNIPAM分子链变为收缩状态而使膜孔“开启” ,为微囊内溶质分子的释放敞开通道 ,于是释放速率快。     

聚乙烯醇/丙烯酰胺接枝共聚物水凝胶的制备及表征

背景：交联水凝胶主要是使大分子链形成网状结构,网固交联基质,这样所得的水凝胶力学性能和透明性相对较差。 目的：采用自由基聚合机制制备聚乙烯醇/丙烯酰胺接枝共聚物水凝胶。 方法：以聚乙烯醇分子作为主链,聚乙烯醇分子中羟基为接枝点,共价接入丙烯酰胺单体。考察反应温度、时间、单体用量和引发剂用量对产物接枝率的影响,通过红外光谱表征聚乙烯醇/丙烯酰胺接枝共聚物共聚物的化学结构。 结果与结论：接枝聚合反应最佳反应条件：引发剂浓度0.04 mol/L、丙烯酰胺/聚乙烯醇(侧羟基)摩尔比6∶1、在40 ℃条件下反应4 h。经过FTIR分析,确认丙烯酰胺与聚乙烯醇发生了聚合反应;经过平衡溶胀测试,分析了接枝聚合物与聚乙烯醇的溶胀率随温度的变化关系,进一步证实了接枝聚合反应的发生,验证了接枝聚乙烯醇/丙烯酰胺接枝共聚物具有明显的温敏性能。      

温敏型凝胶的缓释作用与临床应用

文题释义：温敏型凝胶：是一种特殊的水凝胶,能根据一定温度从流动的液体(溶胶相)转变为非流动的水凝胶(凝胶相)。因其特性,在生物医学和制药方面有广泛的应用,即药物输送、细胞培养、组织工程等。聚N-异丙基丙烯酰胺：由单体N-异丙基丙烯酰胺聚合而成,其大分子链上同时具有亲水性的酰氨基和疏水性的异丙基,使线型聚N-异丙基丙烯酰胺的水溶液及交联后的聚N-异丙基丙烯酰胺水凝胶呈现温度敏感特性。 背景：温敏型凝胶是近年来兴起的一种药物新剂型,因其具有缓释、控释、靶向给药等优势而成为近年来的研究热点。 目的：总结搜索文献中温敏型凝胶各种缓释机制,以及温敏型凝胶在临床上的应用疗效。 方法：在万方、中国知网、维普、PubMed、谷歌学术等数据库中,以“温敏型凝胶,缓释,给药途径”为中文检索词,以“thermosensitive gel,sustained release,administration route”为英文检索词检索温敏型凝胶缓释机制及临床应用方面的文章。结果与结论：①温敏型凝胶具有最低临界溶解温度,能随环境温度改变而发生一定程度的相变,比其他剂型有更多的优势,能使药物在人体内发挥很好的缓释作用,降低药物毒性,防止药物外渗,并提高药物的稳定性,还具有很好的临床应用前景;②温敏型凝胶有着注射、口腔、耳内、鼻腔、眼内、皮肤等多种给药方式,具有广泛的应用前景。但是各种凝胶材料都存在不同缺点,比如天然生物材料具有可塑性差、机械强度不足、容易被病原微生物污染、难以大量生产的缺点,人工合成材料往往亲水性还不够,而且温敏型凝胶在体内的代谢途径对组织器官的影响也尚在研究中。 ORCID: 0000-0002-9070-7602(陈泳佳) 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

纳米纤维大孔支架制备技术在骨组织工程研究中的应用与意义

文题释义：热致相分离：是一种特殊的制备类似于天然细胞外基质的聚合物纳米纤维材料的方法，首先是将聚合物与高沸点、低分子质量的液态或固态稀释剂混合，在高温时形成均相溶液，再将混合物溶液制成所需要的形状，降低温度使溶液发生相分离，然后用某些溶剂进行萃取除去稀释剂，最后进行冷冻干燥得到孔结构。 纳米纤维：是指直径为纳米尺度而长度较大的具有一定长径比的线状材料，此外，将纳米颗粒填充到普通纤维中对其进行改性的纤维也称为纳米纤维。狭义上讲，纳米纤维的直径介于1-100 nm之间；广义上讲，纤维直径低于1 000 nm的纤维均称为纳米纤维。背景：用于骨组织工程的仿生多孔支架要求具有类细胞外基质纳米纤维结构和连通大孔结构，从而有效支持细胞植入、黏附、增殖等行为，促进组织再生。 目的：结合最新相关研究动态，综述用于骨组织工程的纳米纤维大孔支架制备技术研究进展。 方法：由第一作者以“bone tissue engineering，nanofibrous，macroporous，scaffolds”为英文检索词，以“骨组织工程、纳米纤维、大孔、支架”为中文检索词，使用计算机检索Web of science、知网、百度学术数据库中2000至2019年已发表的相关文献，并进行筛选，归纳和总结，最终纳入58篇相关文献进行综述。结果与结论：目前构建纳米纤维结构方法仍局限于静电纺丝、热致相分离和自组装，单一方法制备的骨组织工程支架存在很多问题，其中最大的问题是：很难提供一个三维相互连通的大孔结构来模拟体内的微环境，诱导细胞的迁移、生长、分化、增殖，最终再生新的组织和器官。通过多技术手段的综合运用开发制备大孔纳米纤维支架是必要的，具有重要的科学与现实意义。三维打印对于结构的调控十分精确，可以对支架内部结构及外部形状进行定制，达到双重调控，为骨组织工程的将来带来了发展。 ORCID: 0000-0002-3530-7374(张伟忠) 中国组织工程研究杂志出版内容重点：生物材料；骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性；组织工程     

Smart Antifouling and Self-Cleaning Membrane for Effective Oil/Water Separation

A novel membrane consisting of cellulose acetate (CA) nanofibers and poly(N-isopropylacrylamide) (PNIPAM) microparticles is successfully fabricated by simultaneous electrospinning and electrospraying. The CA/PNIPAM membrane has highly effective gravity-driven separation performances for both oil/water mixtures and oil-in-water emulsions. It separates oil droplets from oil-in-water mixtures and oil-water emulsions with rejection rates of 99.83% and 96%, respectively. In order to examine the contribution of PNIPAM particles, the performance of the CA/PNIPAM membrane is compared with the CA membrane. Increased hydrophilicity due to the inclusion of the PNIPAM particles between CA nanofibers results in a higher rejection ratio and superior antifouling performance. While the CA membrane becomes unusable after 10 cycles during the separation of the oil–water emulsion, the CA/PNIPAM membrane is still in good shape after 20 cycles. The self-cleaning ability of the membrane is examined through the permeation flux below and above the lower critical solution temperature (LCST) of PNIPAM. The reversible thermo-responsive flux variation proves that the pore sizes increase at temperatures above the LCST of PNIPAM. Moreover, when the lubricating oil–water emulsion is filtered through the membrane, the permeate changes from clear to turbid due to the nonretained oil particles as the temperature passes through the LCST.     

Synthesis and swelling-deswelling kinetics of poly(N-isopropylacrylamide) hydrogels grafted with LCST modulated polymers

Two types of thermo-responsive hydrogels are synthesized to obtain comb-type grafted gels with different lower critical solution temperatures (LCSTs) between graft chains and cross-linked backbone networks: these are poly(N-isopropylacrylamide) (PIPAAm) cross-linked hydrogels grafted with poly(N-isopropylacryl amide-co-N,N-dimethylacrylamide) (poly(IPAAm-co-DMAAm)) maintaining a freely mobile end and poly(IPAAm-co-DMAAm) cross-linked hydrogels grafted with PIPAAm chains. The effect of graft chain hydrophilic/hydrophobic balance as well as its mobility on deswelling kinetics of these grafted gels are investigated through the polymer LCST modulation and external temperature changes. The deswelling rate of poly(IPAAm-co-DMAAm)-grafted PIPAAm gel increases with increasing in temperature. This gel shows a discontinuous increase of the deswelling rate when the temperature is applied from below to above the graft chain LCST (37 degrees C). The deswelling rate of PIPAAm-grafted poly(IPAAm-co-DMAAm) gel increases continuously when the temperature is applied from below to above the graft chain LCST (31 degrees C). Due to the strong hydrophilicity of backbone network, the hydrophobic aggregation force weak. In contrast to the graft-type gels, normal-type poly(IPAAm-co-DMAAm) cross-linked gel without graft chains demonstrates the discontinuous decrease for the deswelling rate when the temperature is applied from below to above the polymer LCST (36 degrees C), entrapping water inside the gel due to the formation of an impermeable dense skin layer at the gel surface. These gel deswelling mechanisms are discussed in terms of gel structures.     

Synthesis and swelling-deswelling kinetics of poly(N-isopropylacrylamide) hydrogels grafted with LCST modulated polymers

Two types of thermo-responsive hydrogels arc synthesized to obtain comb-type grafted gels with different lower critical solution temperatures (LCSTS) between graft chains and cross-linked backbone networks: these are poly(N-isopropylacrylamide) (PIPAAm) cross-linked hydrogels grafted with poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (poly(IPAAm-(-o-DMAAiii)) maintaining a freely mobile end and poly(IPAAm-co-DMAAm) cross-linked hydrogels grafted with PIPAAm chains. The effect of graft chain hydrophilic/hydrophobic balance as well as its mobility on deswelling kinetics of these grafted gels are investigated through the polymer LCST modulation and external temperature changes. The deswelling rate of poly(IPAAm-co-DMAAm)-grafted PIPAAm gel increases with increasing in temperature. This gel shows a discontinuous increase of the deswelling rate when the temperature is applied from below to above the graft chain LCST (37°C). The deswelling rate of PIPAAm-grafted poly(IPAAm-co-DMAAm) gel increases continuously when the temperature is applied from below to above the graft chain LCST (31°C). Due to the strong hydrophilicity of backbone network, the hydrophobic aggregation force weak. In contrast to the graft-type gels, normal-type poly(IPAAm-co-DMAAm) cross-linked gel without graft chains demonstrates the discontinuous decrease for the deswelling rate when the temperature is applied from below to above the polymer LCST (36°C), entrapping water inside the gel due to the formation of an impermeable dense skin layer at the gel surface. These gel deswelling mechanisms are discussed in terms of gel structures.     

The effect of extensible PEG tethers on shielding between grafted thermo-responsive polymer chains and integrin-RGD binding

The affinity control of integrin-RGD (Arg-Gly-Asp) binding by a thermal "on-off" switch has been achieved using newly designed surfaces presenting grafted temperature-responsive poly(N-isopropylacrylamide-co-2-carboxyisopropylacrylamide) copolymers functionalized with synthetic peptides. The prepared surface was designed to expose the tethered peptides available for cell binding at active "on" state above the lower critical solution temperature (LCST). The fully extended chains, on the other hand, masked the peptides completely and the cells started to detach from the surfaces at inactive "off" sate below the LCST. This paper elucidates the shielding effect of the grafted polymer chains on the dissociation of integrin-RGD binding below the LCST. To assess the ability of the polymer-shielding, extensible poly(ethylene glycol) (PEG) tethers were introduced between peptides and the grafted polymers. PEG chains allow peptides to be tethered to surfaces via functional PEG end-groups, leading to active "on" state even below the LCST. The time required to release cells from the surface was found to be longer when peptides were coupled to an extensible tether ends, suggesting that the surfaces can engender cell attachment through adhesive moieties covalently bound to the free ends of PEG chains. These results indicate that architectural changes on the nanometer length scale are crucial for controlling integrin-RGD binding and one of the main factors causing cell detachment is the shielding effect of the grafted polymer chains.     

Triggering the Thermosensitive Properties of Hydrophobically Modified Poly(N‐isopropylacrylamide) by Complexation with Cyclodextrin Polymers

Summary: Hydrophobically modified poly(N‐isopropylacrylamide) (PNIPAM) containing either an adamantyl or a dodecyl group were prepared and characterized. Self‐association in aqueous solutions was evidenced by fluorescence measurements using pyrene as a probe. The lower critical solution temperatures (LCST) were determined from cloud point measurements. They strongly depended on the hydrophobic group and the substitution level. The association between hydrophobically modified PNIPAM and β‐cyclodextrin (monomers and polymers) was investigated by cloud point and viscosity measurements. The presence of β‐cyclodextrin monomers generally shifted the LCST to a higher temperature, the complexation increasing the solubility of PNIPAM chains. β‐Cyclodextrin polymers mixed with hydrophobically modified PNIPAM generated supramolecular assemblies. This was evidenced by viscosity measurements of the mixtures at temperatures lower than the LCST. Moreover, depending on the substitution level of the PNIPAM, the LCST was increased (1% hydrophobic groups) or decreased (4% hydrophobic groups) by more than 10 °C upon β‐cyclodextrin polymer addition.

Transmission variations of different mixtures of PNIPAM‐C12 with cyclodextrin compounds vs temperature.     

Effect of a Polymeric Additive on the Pore‐Size Distribution and Shrinking Process of a Hydrogel Network

A systematic comparison of the effect of architectural modifications to the network structure on the internal microstructure of N‐isopropylacrylamide (NIPA) based hydrogels showed that the addition of a second component to the network significantly increased the proportion of macropores in the network. The second components considered were short poly(N‐isopropylacrylamide) (PNIPAM) chains grafted to the network backbone, high‐molecular‐weight polyacrylamide (PAM) chains, or microsphere particles of PNIPAM. Structures are proposed for each of the modified gel networks taking into account the new structural information. Through a combination of the pore size and network structure data reported here, and with the shrinking data obtained previously, shrinking mechanisms are proposed for each of the modified network structures. In all cases, the enhanced shrinking rates were directly caused by the presence of the second component, which acted as nuclei for shrinking (graft‐PNIPAM and PNIPAM microspheres) or as water‐release channels (PAM gel), and indirectly caused by the second components via their affect on the network microstructure.

Proposed structures for the architecturally modified gels based on the pore‐size information. Graft‐PNIPAM gel. The freely mobile graft chains prevent chains from meeting resulting in larger pores.     

Temperature‐Responsiveness and Antimicrobial Properties of CNT–PNIPAM Hybrid Brush Films

Temperature‐responsive carbon nanotube (CNT)/poly(N‐isopropylacrylamide) (PNIPAM) hybrid brush films were prepared by combining the layer‐by‐layer and surface‐initiated polymerization (LbL‐SIP) techniques. Atom transfer radical polymerization (ATRP) is employed for the preparation of PNIPAM polymer brushes. Antibacterial activity of the CNT/PNIPAM films are investigated against Exiguobacterium sp. AT1b and Exiguobacterium sibiricum strains. Dead assay results show high microbial inactivation on coated surfaces with CNT films, while very low microbial inactivation is observed in PNIPAM films at all temperatures tested. The CNT–PNIPAM films, on the other hand, have antibacterial properties below 32 °C, which is below the lower critical solution temperature (LCST), but allows biofilm formation above the LCST.     

Surface modification of PHBV nanofiber mats for rapid cell cultivation and harvesting

Abstract

To maintain the original function of a specific tissue for therapeutic tissue engineering, an advanced cell culture surface for repeat cell proliferation is necessary. We designed a novel cell proliferation and rapid harvesting surface by combining nonwoven nanofiber mat and a thermo-responsive polymer. Nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) mats were fabricated by the electrospinning technique. A poly(N-isopropylacrylamide) (PNIPAM) thermo-responsive layer was grafted on the PHBV nanofiber mat by electron beam irradiation. The average diameter of the PNIPAM-grafted PHBV nanofibers was determined by SEM. ATR-FTIR and ESCA were used to confirm the grafting of PNIPAM onto the PHBV nanofiber surface. Water contact angles on the mats were measured in response to temperature changes. Human adipose-derived stem cells (ADSCs) were cultured on the PNIPAM-grafted PHBV nanofiber mat to investigate cell proliferation, harvesting, and functionality during repeat subculture. Detached ADSCs from each surface by low temperature treatment and trypsin-EDTA were compared by a fluorescence-activated cell sorter (FACS) using expression of stem cell membrane-specific markers such as CD-13 PE, CD-29 PE, and CD-90 FITC. The mass cultivation and intact harvesting of stem cells by low temperature treatment using a thermo-responsive PHBV nanofiber mat is a promising technique for use in regenerative medicine and stem cell therapy.