High-performance reusable materials from renewable resources
are
rare and urgently required in bioseparation. Herein, a series of tannic
acid-chitosan composite membranes for the enrichment of phosphopeptides
were fabricated by the freeze casting method. First, a tannic acid-chitosan
composite membrane was acquired via the multiple hydrogen bonds between
tannic acid and chitosan, which had a long-range aligned three-dimensional
microstructure. Second, a covalent–hydrogen bond hybrid composite
was also fabricated, with stable and aligned honeycomb-like microstructures
that formed by the synergy of covalence and hydrogen bonding. Besides,
a ternary composite membrane was “one-pot” synthesized
by the copolymerization of tannic acid, chitosan, and Ti4+ ions, indicating the feasibility of involving metal ions in the
composition of the polymer skeleton in place of additional modification
steps. The as-prepared chitosan composite membranes exhibited excellent
performance in the enrichment of phosphopeptides from β-casein
tryptic digest and human serum. Benefitting from the long-range aligned
honeycomb-like structure coordinated by hydrogen bonds and covalent
bonds, and a large number of pyrogallol functional groups provided
by tannic acid, the covalent–hydrogen bond hybrid membrane
showed excellent reusability and could be reused up to 16 times in
phosphopeptide enrichment, as far as we know, which is the best reported
result to date.