The self-assembling tripeptide L-Leu-D-Phe-D-Phe (Lff) was synthesized as previously reported according to standard protocols, purified by reversed-phase high-performance liquid chromatography (HPLC), and its identity and purity was confirmed by ESI-MS, 1H and 13C-NMR (see ESI, Section 1). The tripeptide is easily dissolved in aqueous phosphate buffer at alkaline pH in its anionic form, so that the negative charges repel each other. In the presence of the tripeptide, NDs dispersions did not appear significantly different by the naked eye (see ESI, Section 2). We tested three different concentrations, analogously to previous studies with CNOs, to offer a means of comparison and better understand the effects of the different nanocarbon surface structure on its interactions with the peptide. Interestingly, transmission electron microscopy (TEM) analyses revealed fewer aggregates especially in the presence of the tripeptide at the lower (1 mg/ml) but also at medium (2 mg/ml) ND levels, while at the highest level tested (4 mg/ml), aggregates appeared to the same extent for samples that were prepared either with or without the peptide (Figure and ESI, Section 3). Dynamic light scattering (DLS) analyses (Table ) revealed a negative ζ-potential for NDs, as expected, which in the case of the lowest ND amount tested changed from -20.6 ±0.6 to -23.0 ±1.2 in the presence of the tripeptide, corresponding to an increase of 12% of negative charges on the ND surface with the anionic biomolecule. The hydrodynamic diameters confirmed presence of aggregates, albeit the peptide led to their reduced size corresponding to 85% of the average diameter found for NDs without the biomolecules. The DLS data were thus qualitatively in agreement with the high-magnification TEM micrographs (Figure ). NDs (4 mg/ml) + Lff peptide -22.9 ± 0.7 1452 ± 355