Gold Nanorods Decorated by Conjugated Microporous Polymers for Infrared Responsive Cytostatic Drug Delivery

Near-infrared (NIR) controlled drug delivery systems have drawn a lot of attention throughout the past few decades due to the deep penetration depth and comparatively minor side effects of the stimulus. In this study, we introduce an innovative approach for gastric cancer treatment by combining photothermal infrared-sensitive gold nanorods (AuNRs) with a conjugated microporous polymer (CMP) to create a drug delivery system tailored for transporting the cytostatic drug 5-fluorouracil (5-FU). CMPs are fully conjugated networks with high internal surface areas that can be precisely tailored to the adsorption and transport of active compounds through the right choice of chemical functionalities. By incorporation of surfactant-stabilized AuNRs into the CMP synthesis in dimethylformamide (DMF) the surfactant shell is destabilized and subsequently replaced by the CMP. Particularly, low initial surfactant concentrations led to uniform distribution of the AuNRs in the polymer matrix. Importantly, the integrated AuNRs maintain their plasmonic properties, as was confirmed via electron energy loss spectroscopy. Therefore, the significant photothermal properties are translated to the hybrid material as shown in a proof-of-principle experiment. Further, in an approximated gastric environment, 5-FU release studies were conducted with and without NIR stimulus. Thereby it was observed that increased Brownian motion due to the NIR irradiation not only accelerates the release but also increases the total released amount by influencing the adsorption-desorption equilibrium. This remarkable level of control of the release process underlines the immense potential of this hybrid material for precise and targeted drug delivery.