Peptide-coated nanoparticles: Adsorption and desorption studies of cationic peptides on nanodiamonds

The functionalization of nanoparticle surfaces remains a major challenge for broader applications in biology. To study the physisorption of peptides on nanodiamonds (NDs), we developed reliable and facile methods: UV titration, MALDI-TOF mass spectrometry or fluorescence spectrophotometry. These readily applicable procedures allowed us to analyze the adsorption and desorption behaviors of different cationic peptides. A rough estimate led to propose that an average of three to four shells of amphiphilic peptides rapidly adsorbed on NDs surface: about half of the molecules being adsorbed with a high affinity, while the other half may be exchanged within a few minutes. If a photoactivatable amino acid was incorporated in the peptide sequence, the subsequent irradiation allowed similarly the coating of three to five shells of peptides on the NDs surface, but in that case peptides were not exchangeable at all, even after a few days. Stable cationic nanodiamonds may be obtained by simple physisorption of amphiphilic peptides, leading to nanoparticles with a positive zeta potential in the appropriate range for biological applications.