Eudragit S100 coated nanodiamond-based nanoparticles as an oral chemo-photothermal delivery system for local treatment of colon cancer

Oral colonic nano-drug delivery system has received more and more attention in the treatment of colon cancer due to local precision treatment and reduction of drug system distribution. However, the complex and harsh gastrointestinal environment and the retention of nanoparticles in the colon limit its development. To this end, we designed Eudragit S100 (ES) coated nanoparticles (ES@PND-PEG-TPP/DOX). Polydopamine coated nanodiamond (PND) was modified with amino-functionalized polyethylene glycol (NH2-PEG-NH2) and triphenylphosphine (TPP) successively. Due to the high specific surface area of PND, it can efficiently load the model drug doxorubicin hydrochloride (DOX). In addition, PND also has high photothermal conversion efficiency, generating heat to kill cancer cells under near infrared (NIR) laser, realizing the combination of chemotherapy and photothermal therapy (CT-PTT). TPP modification enhanced nanoparticle uptake by colon cancer cells and prolonged preparations retention time at the colon. ES shell protected the drug from being destroyed and prevented the nanoparticles from sticking to the small intestine. Ex vitro fluorescence imaging showed that TPP modification can enhance the residence time of nanoparticles in the colon. In vivo pharmacodynamics demonstrated that CT-PTT group has the greatest inhibitory effect on tumor growth, which means that the nanocarrier has potential clinical value in the in-situ treatment of colon cancer.