The self-assembly of amphiphilic peptide I 3 K (Ac-I 3 K-NH 2 ) and its potential application as a drug nanocarrier have been investigated. I 3 K monomers and nanotubular segments were initially the dominant species in aqueous solution and they gradually self-assembled into mature nanotubes with heights of approximately 12 nm and lengths of more than 1 mm. The encapsulation properties of the self-assembled peptide nanotubes were then investigated using model compound guests, including anionic hydrophilic methyl orange (MO) and hydrophobic oil red. It revealed that the model compounds could be efficiently encapsulated by I 3 K assemblies via electrostatic and hydrophobic interactions, respectively. Atomic force microscopy images demonstrated that variations in drug concentration did not significantly alter the structures of the peptide assemblies but could affect their sizes. Circular dichroism analyses indicated the predominance of b-sheet conformation associated with the self-assembled system regardless of drug concentrations. The in vitro releasing behavior of the encapsulated model drugs was also studied by the techniques of dialysis. The entrapped model drug MO exhibited an accelerated release as the solution pH was either decreased to 2.0-3.0 or increased to 10.0-11.0 but revealed a sustained release at physiological pH. These results demonstrated that these self-assembled peptide nanotubes could serve as potential drug nanocarriers with efficient encapsulation ability, and sustained and pH-responsive release properties.

We report the molecular self-assembly of two amphiphilic peptides (A 6 K and V 6 K) and the application of their self-assemblies as organic templates to direct biosilica formation. Under ambient conditions, A 6 K selfassembled into nanotubes 2.7 nm tall and approximately 1 mm to 2 mm long. In contrast, V 6 K selfassembled into lamellar-stack nanostructures approximately 4 nm tall and under 100 nm long. The selfassembled peptide nanostructures were used as organic templates to direct biosilica formation.Comparing with the self-assembled structures formed by the peptide/anions system, novel silica morphologies can be obtained by changing the peptide composition, using different anions, and applying electrostatic/flow fields. We observed that the presence of anions is important but not enough to produce ordered silica structures with novel morphologies. This study provides further understanding of silica biomineralization tailored by assembled peptides, which offers a simple but efficient method to control the formation of inorganic material.

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