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

Abstract

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.