Abstract
We report a simple way to obtain polymer-coated multiwalled boron nitride nanotubes (BNNTs) conducted under mild conditions compatible with fragile biopolymers. The approach converts aggregated pristine BNNTs into colloidally stable dispersions in water without requiring treatment at high temperature or in strongly oxidative conditions. The method relies on our experimental observation that glycine (NH2-CH2-COOH, Gly) interacts with BNNTs, in accordance with theoretical calculations. The role of glycine in this process is 2-fold: the Gly amine group binds to the B-sites of BNNTs, while the Gly carboxylic acid function provides ionic anchoring sites for interactions with polyelectrolytes. The formation of Gly-BNNTs proved to be essential, since they readily disperse in water as disentangled objects and spontaneously adsorb polycations, such as chitosan (CH), polyanions, such as hyaluronan (HA), and polyzwitterionic polymers, such as chitosan-phosphorylcholine (CH-PC). Treatment of aqueous dispersions of coarsely coated BNNTs with an immiscible solvent (hexane) resulted in the complete coverage of the BNNT surfaces via oil/water interfacial assembly. This work provides a rapid, mild, and scalable route to water-dispersible biofunctional BNNTs that may serve as drug delivery vehicles or scaffolds in tissue engineering.