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Issue 24, 2009
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Synthesis and pH-responsive properties of pseudo-peptides containing hydrophobic amino acid grafts

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Abstract

Pseudo-peptidic polymers have been synthesised by grafting L-valine (PV), L-leucine (PL) and L-phenylalanine (PP) onto the pendant carboxylic acid moieties of a pH-responsive polyamide, poly(L-lysine isophthalamide). The pH-responsive aqueous solution properties of PV-75, PL-75 and PP-75 with a stoichiometric degree of substitution of 75 mol% have been compared with those of the parent poly(L-lysine isophthalamide) using UV-visible and fluorescence spectroscopy. At low concentrations (≤0.1 mg mL−1), the grafted polymers displayed pH-dependent conformation. The pH at the onset of hydrophobic association (pHh) and the pH range over which association occurred varied significantly between the different amino acid grafts. The pHh values of PV-75, PL-75 and PP-75 at 0.025 mg mL−1 were 6.2, 7.0 and 7.2, respectively. Increasing concentration enhanced intermolecular aggregation. A bis-functional Cy5 derivative, incorporated within the backbones of poly(L-lysine isophthalamide) (polyCy5) and PP-75 (PDP-75), was demonstrated to act as a fluorescence reporter on the state of polymer conformation and aggregation. The intracellular trafficking of PDP-75, examined by confocal microscopy, indicates potential applications of the grafted polymers in drug delivery and medical imaging.

Graphical abstract: Synthesis and pH-responsive properties of pseudo-peptides containing hydrophobic amino acid grafts

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Article information


Submitted
10 Feb 2009
Accepted
24 Apr 2009
First published
13 May 2009

J. Mater. Chem., 2009,19, 4217-4224
Article type
Paper

Synthesis and pH-responsive properties of pseudo-peptides containing hydrophobic amino acid grafts

R. Chen, M. E. Eccleston, Z. Yue and N. K. H. Slater, J. Mater. Chem., 2009, 19, 4217
DOI: 10.1039/B902822F

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