Nanodiamond bioconjugate probes and their collection by electrophoresis

The application of detonation nanodiamonds (NDs) as probes for protein capture and electrophoretic collection was investigated. NDs were chemically modified in a series of reactions to produce a ND-NH2 product that had increased chemical homogeneity. The product was characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). FTIR spectra were taken using an IR vacuum cuvette and the samples were dehydrated at different temperatures. The ND-NH2 product was capable of conjugating to N-hydroxysuccinimide derivatives of TAMRA and biotin. We calculated that the number of chemically attached TAMRA molecules on ND-NH2 was ∼ 1 molecule/nm2. The singly conjugated TAMRA-ND (T-ND) and doubly conjugated TAMRA-ND-Biotin (T-ND-B) products formed stable aqueous colloidal suspensions. T-ND and T-ND-B were collected on planar electrodes and silicon field tip arrays using a field of 10 V/cm. The rate of collection for the aminated ND is dependent upon field strength and an exponential decrease in current was observed as a function of time. Streptavidin was captured by the T-ND-B bioconjugate probe and this nanoparticle–protein complex was collected from solution by electrophoresis.