Construction of catechol-grafted chitosan alginate/barium sulfate microcapsules for computed tomography real-time imaging and gastroretentive drug delivery.

Background: The gastroretentive drug delivery system is an effective administration route, which can improve the bioavailability of the drug and the therapeutic effect by prolonging the release time of the drug and controlling the release rate in the stomach. Methods: Inspired by the excellent adhesion properties of mussel protein, we prepared novel catechol-grafted chitosan alginate/barium sulfate microcapsules (Cat-CA/BS MCs) with mucoadhesive properties and computed tomography (CT) imaging function for gastric drug delivery. First, barium sulfate nanoclusters used as CT contrast agent were synthesized in situ in the Cat-CA/BS MCs through a one-step electronic spinning method. Next, catechol-grafted chitosan as the mucoadhesive moiety was coated on the surface of Cat-CA/BS MCs by polyelectrolyte molecule self-assembly. Results: The prepared Cat-CA/BS MCs could effectively retained in the stomach for 48 hours and successively released ranitidine hydrochloride, which could be used for the treatment of gastric ulcer. Cat-CA/BS MCs exhibited superior CT contrast imaging properties for real-time tracking in vivo after oral administration. Conclusion: These findings demonstrate that Cat-CA/BS MCs serving as multifunctional oral drug carriers possess huge potential in gastroretentive drug delivery and non-invasive visualization.

Facile synthesis of cerium-doped carbon quantum dots as a highly efficient antioxidant for free radical scavenging.

Excessive reactive oxygen species (ROS) can lead to irreversible damage to the human body in vivo, therefore it is highly desirable to exploit an efficient antioxidant. Recently, cerium oxide nanoparticles have attracted extensive attention in the field of biomedicine due to their excellent antioxidant properties. In this study, cerium-doped carbon quantum dots (Ce-doped CQDs) with hydroxyl radical scavenging capacity were synthesized for first time by one-step hydrothermal carbonization method. The resultant Ce-doped CQDs with the average particle size of 2.5 nm possessed the properties of good water solubility, colloid stability, and strong fluorescence, which are similar to traditional CQDs. Meanwhile, the Ce-doped CQDs had good biocompatibility and negligible cytotoxicity. Taking advantage of inherent ultra-small size, the Ce-doped CQDs exhibited a high Ce3+/Ce4+ ratio at the surface of particles. The radical scavenging capability of the Ce-doped CQDs was proved by a simple photometric system in vitro, which provided direct evidence for its antioxidant potency. Furthermore, the Ce-doped CQDs had a high ability to protect cells from hydrogen peroxide-induced damage by scavenging hydroxyl radicals. These results suggest that Ce-doped CQDs as a new ROS scavenger may provide potential prospects for the treatment of oxidative stress-related diseases.