pH‐responsive phenylboronic acid‐modified diamond particles: Switch in carbohydrate capture ability triggers modulation of physicochemical and lectin‐recognition properties

Nanodiamonds (NDs) are new carbon-based materials that have recently been demonstrated to hold promise in a number of biomedical applications. The production of stable colloidal solutions from ND particles obtained through detonation still remains a challenge, as these particles have a strong tendency to form large aggregates. Herein, is described a 4-aminophenylboronic acid-modified ND (ND-BA) system that can either disperse or aggregate in aqueous solution, in the presence of an appropriate monosaccharide and in response to an external pH trigger. At pH = 8.4, the ND-BA forms stable colloidal solutions when mannose is present, as a consequence of their ability to sequester the monosaccharide through the formation of sugar boronic ester complexes. A decrease in the pH to 4 triggers the disruption of the boronic acid ester bonds and results in mannose-release thereby inducing aggregation of the ND-BA particles. The aggregation–dispersion process is seen to be completely reversible and effectively allows control of the physiochemical properties of the ND-BA–glycan couple through an external pH stimulus. Moreover, the mannose-saturated ND-BA particles are shown to interact selectively with appropriate lectins and this recognition demonstrated to be effectively switched off at low pH values.