School of Chemical Engineering , Purdue University , West Lafayette , Indiana 47907 , United States.
Physical and Computational Sciences Directorate , Pacific Northwest National Laboratory , Richland , Washington 99352 , United States.
ACS Appl Mater Interfaces. 2018 Aug 8;10(31):26084-26098. doi: 10.1021/acsami.8b09630. Epub 2018 Jul 27.
Poly(propylene carbonate) (PPC) decomposes at high temperature to release CO. This CO-generation temperature of PPC can be reduced down to less than 80 °C with the aid of a photoacid generator (PAG). In the present work, we demonstrate that using an additional helper component, surface plasmonic gold nanorods (GNRs), the PPC degradation reaction can also be initiated by infrared (IR) irradiation. For this purpose, a PPC-containing nanoparticle formulation was developed in which PPC-based amphiphilic block copolymers (BCPs), poly(poly(ethylene glycol) methacrylate- b-propylene carbonate- b-poly(ethylene glycol) methacrylate) (PPEGMA-PPC-PPEGMA), were self-assembled with GNRs and PAG molecules via solvent exchange. Under IR irradiation, GNRs produce heat that can cause PPC to decompose into CO, and PAG (after UV pretreatment) catalyzes this PPC degradation process. Two PPEGMA-PPC-PPEGMA materials were used for this study: PPEGMA-PPC-PPEGMA ("G7C6G7") and PPEGMA-PPC-PPEGMA ("G2C6G2"). Addition of CTAB-coated GNRs dispersed in water to a G2C6G2 solution in DMF produced individually G2C6G2-encapsulated GNRs, whereas the same solvent exchange procedure resulted in the formation of polymer-coated GNR clusters when G7C6G7 was used as the encapsulating material. GNR/G2C6G2 NPs exhibited a surface plasmon resonance peak at 697 nm. The clustered morphology of G7C6G7-encapsulated GNRs caused a blue shift of the absorbance maximum to 511 nm. As a consequence, GNR/G2C6G2 NPs showed a greater absorbance/heat generation rate under IR irradiation than did GNR/G7C6G7 NPs. The IR-induced CO generation rate was about 4.2 times higher with the GNR/G2C6G2+PAG sample than that with the GNR/G7C6G7+PAG sample. Both GNR/G7C6G7+PAG and GNR/G2C6G2+PAG systems produced ultrasound contrast enhancement effects under continuous exposure to IR light for >20 min; contrast enhancement was more spatially uniform for the GNR/G2C6G2+PAG sample. These results support the potential utility of PPC as a CO-generating contrast agent in ultrasound imaging applications.
聚（碳酸丙烯酯）（PPC）在高温下分解会释放 CO。借助光酸产生剂（PAG），可以将 PPC 的 CO 生成温度降低到 80°C 以下。在本工作中，我们证明了使用额外的助催化剂成分，表面等离激元金纳米棒（GNR），PPC 降解反应也可以通过红外（IR）辐照引发。为此，开发了一种含有 PPC 的纳米颗粒制剂，其中包含基于 PPC 的两亲嵌段共聚物（BCP），聚（聚（乙二醇）甲基丙烯酸酯- b-碳酸丙烯酯- b-聚（乙二醇）甲基丙烯酸酯）（PPEGMA-PPC-PPEGMA），通过溶剂交换与 GNR 和 PAG 分子自组装。在 IR 辐照下，GNR 产生的热量会导致 PPC 分解为 CO，而 PAG（在 UV 预处理后）则催化该 PPC 降解过程。本研究使用了两种 PPEGMA-PPC-PPEGMA 材料：PPEGMA-PPC-PPEGMA（“G7C6G7”）和 PPEGMA-PPC-PPEGMA（“G2C6G2”）。将 CTAB 包覆的 GNR 分散在水中添加到 G2C6G2 溶液中，得到单独的 G2C6G2 包封的 GNR，而当使用 G7C6G7 作为封装材料时，相同的溶剂交换程序会导致聚合物包封的 GNR 簇的形成。GNR/G2C6G2 NPs 的表面等离子体共振峰在 697nm 处。G7C6G7 包封的 GNR 的聚集形态导致吸收最大值蓝移至 511nm。因此，与 GNR/G7C6G7 NPs 相比，GNR/G2C6G2 NPs 在 IR 辐照下具有更大的吸收/发热率。带有 GNR/G2C6G2+PAG 样品的 IR 诱导 CO 生成率比带有 GNR/G7C6G7+PAG 样品的高约 4.2 倍。在连续暴露于 IR 光超过 20 分钟的情况下，GNR/G7C6G7+PAG 和 GNR/G2C6G2+PAG 系统均产生超声对比增强效果；对于 GNR/G2C6G2+PAG 样品，对比增强效果更均匀。这些结果支持 PPC 作为超声成像应用中 CO 生成对比剂的潜在用途。
