Reversible and Rapid pH-Regulated
Self-Assembly of
a Poly(ethylene glycol)–Peptide Bioconjugate
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Abstract
The use of external triggers to manipulate
the secondary structure
of self-assembling peptides conjugated to flexible synthetic polymers
is a challenging problem, particularly in terms of reversibility.
Here, we demonstrate, for the first time, sustained rapid and reversible,
pH-regulated self-assembly of the peptide ELELELELELF (EL-5F) and
its conjugates with 2 and 5 kDa poly(ethylene glycol) (EL-5F–PEG-2K
and EL-5F–PEG-5K). Circular dichroism indicated the formation
of β-sheet structures at pH < 5.9, 5.8, and 5.4 and disassembly
to random coils above those pH values for EL-5F, EL-5F–PEG-2K,
and EL-5F–PEG-5K, respectively. β-sheets were confirmed
by the thioflavin T assay, while transmission electron microscopy
revealed the existence of extended fibrillar structures below the
above pH values. pH-induced secondary structure conversion was reproducible
for over 15 cycles, even at salt concentrations of up to 200 mM NaCl,
and was quantitatively related to the pH. Self-supporting hydrogelation
after self-assembly was observed at concentrations as low as 0.2 wt
%, which is 15-fold lower than previously reported concentrations.
This simple approach to mediate reversible self-assembly of EL-5F–PEG
bioconjugates is expected to offer novel functionality relevant to
drug delivery and bioseparation systems
