Conjugation of Phenylboronic Acid Moiety through Multistep Organic Transformations on Nanodiamond Surface for an Anticancer Nanodrug for Boron Neutron Capture Therapy

Detonation nanodiamonds (DNDs) have attracted considerable attention, in particular, in the field of nanomedicine due to their biocompatibility as well as various functionalities imparted by surface modification. Meanwhile, boron neutron capture therapy (BNCT) is an advanced cancer treatment utilizing nuclear fission reaction of 10B upon neutron irradiation. Recently, quite a few boron-containing nanoparticles have been investigated to deliver 10B atoms into cancer tissue selectively and retentively. In this study, we explored boronic acid functionalized DNDs as an anticancer agent for BNCT. Phenylboronic acid (PBA) moiety was introduced to polyglycerol (PG) modified DNDs (DND-PG) through multistep organic transformation, giving percent order of boron atoms. The process is scalable and reliable by simple covalent chemistry and the resulting product is well dispersed, and stable chemically and physically under physiological conditions. In the in vivo experiments, the resulting material was accumulated in the tumor to exert BNCT efficacy upon neutron irradiation. These results demonstrate that the PBA functionalized DNDs are a promising candidate as an anticancer nanodrug for BNCT.