Abel Silvestre Bongiovanni, Molina María A, Rivarola Claudia R, Kogan Marcelo J, Barbero Cesar A
Programa de Materiales Avanzados, Departamento de Química, Universidad Nacional de Río Cuarto, Ruta 8, Km 601, Agencia postal N° 3, 5800, Río Cuarto, Argentina.
Nanotechnology. 2014 Dec 12;25(49):495602. doi: 10.1088/0957-4484/25/49/495602. Epub 2014 Nov 19.
Conductive polyaniline nanoparticles (PANI NPs) are synthesized by oxidation of aniline with persulfate in acid media, in the presence of polymeric stabilizers: polyvinilpyrrolidone (PVP), poly(N-isopropylacrylamide) (PNIPAM), and hydroxylpropylcellulose (HPC). It is observed that the size of the nanoparticles obtained depends on the polymeric stabilizer used, suggesting a mechanism where the aggregation of polyaniline molecules is arrested by adsorption of the polymeric stabilizer. Indeed, polymerization in the presence of a mixture of two polymers having different stabilizing capacity (PVP and PNIPAM) allows tuning of the size of the nanoparticles. Stabilization with biocompatible PVP, HPC and PNIPAM allows use of the nanoparticle dispersions in biological applications. The nanoparticles stabilized by thermosensitive polymers (PNIPAM and HPC) aggregate when the temperature exceeds the phase transition (coil to globule) temperature of each stabilizer (Tpt = 32 °C for PNIPAM or Tpt = 42 °C for HPC). This result suggests that an extended coil form of the polymeric stabilizer is necessary to avoid aggregation. The dispersions are reversibly restored when the temperature is lowered below Tpt. In that way, the effect could be used to separate the nanoparticles from soluble contaminants. On the other hand, the PANI NPs stabilized with PVP are unaffected by the temperature change. UV-visible spectroscopy measurements show that the nanoparticle dispersion changes their spectra with the pH of the external solution, suggesting that small molecules can easily penetrate the stabilizer shell. Near infrared radiation is absorbed by PANI NPs causing an increase of their temperature which induces the collapse of the thermosensitive polymer shell and aggregation of the NPs. The effect reveals that it is possible to locally heat the nanoparticles, a phenomenon that can be used to destroy tumor cells in cancer therapy or to dissolve protein aggregates of neurodegenerative diseases (e.g. Alzheimer). Moreover, the long range control of aggregation can be used to modulate the nanoparticle residence inside biological tissues.
导电聚苯胺纳米粒子（PANI NPs）是在酸性介质中，以过硫酸盐氧化苯胺，并在聚合物稳定剂（聚乙烯吡咯烷酮（PVP）、聚（N-异丙基丙烯酰胺）（PNIPAM）和羟丙基纤维素（HPC））存在的条件下合成的。据观察，所得纳米粒子的尺寸取决于所使用的聚合物稳定剂，这表明存在一种机制，即聚苯胺分子的聚集通过聚合物稳定剂的吸附而受阻。实际上，在具有不同稳定能力的两种聚合物（PVP和PNIPAM）的混合物存在下进行聚合，可以调节纳米粒子的尺寸。用生物相容性的PVP、HPC和PNIPAM进行稳定化处理，使得纳米粒子分散体可用于生物应用。当温度超过每种稳定剂的相转变（从线圈状到球状）温度（PNIPAM的Tpt = 32°C或HPC的Tpt = 42°C）时，由热敏聚合物（PNIPAM和HPC）稳定的纳米粒子会发生聚集。这一结果表明，聚合物稳定剂的伸展线圈形式对于避免聚集是必要的。当温度降低到Tpt以下时，分散体可可逆地恢复。通过这种方式，该效应可用于将纳米粒子与可溶性污染物分离。另一方面，用PVP稳定的PANI NPs不受温度变化的影响。紫外-可见光谱测量表明，纳米粒子分散体的光谱会随外部溶液的pH值而变化，这表明小分子可以很容易地穿透稳定剂外壳。近红外辐射被PANI NPs吸收，导致其温度升高，进而引起热敏聚合物外壳的塌陷和纳米粒子的聚集。该效应表明，可以局部加热纳米粒子，这一现象可用于癌症治疗中破坏肿瘤细胞或溶解神经退行性疾病（如阿尔茨海默病）的蛋白质聚集体。此外，聚集的远程控制可用于调节纳米粒子在生物组织内的停留时间。
