Morphology transition of self-aggregates of poly(amino acid)-drug conjugates

• A series of amphiphilic phytosphingosine (PHS) grafted poly(amino acid)s were synthesized.
• Self-aggregation of the polymers were observed as functions of grafting degrees and types of poly(amino acid)s by small angle neutron scattering analysis.
• Morphology transitions of the self-aggregates from sphere to ellipsoid to cylindrical micelles were observed with increasing number of grafted phytosphingosines.
• The morphological change of PHS-grafted poly(amino acid) was interpreted with changes in the geometry of the building blocks.

In this paper, we report morphology tunable self-aggregates of poly(amino acid)-drug conjugates. Amphiphilic drug-grafted polymers were synthesized by grafting hydrophobic phytosphingosine (PHS) onto two different hydrophilic poly(amino acid)s backbones, and the hydrophilic/hydrophobic ratio were controlled by varying the number of grafted drugs. The amphiphilic poly(amino acid)-g-PHS formed self-aggregates in aqueous solution, and morphology transitions of the self-aggregates from sphere to ellipsoid to cylindrical micelles were observed with increasing number of grafted phytosphingosines. Morphologies of self-aggregates were further confirmed by small angle neutron scattering, showing that the obtained self-aggregates consisted of a thin poly(amino acid) shell and a PHS core. The morphological changes of PHS-grafted poly(amino acid) were interpreted using geometrical changes of building blocks arising from the decrease of the hydrophilic part per PHS with increasing number of PHS grafts.

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