We report here on poly(amino acid)-based bioadhesives with potential to bon
d to soft tissues. The systems investigated included homopolymer poly(amino
acids), mixtures of poly(amino acids) and amino acids, and blends of diffe
rent poly(amino acids). Adhesive performance was tested in tension on glass
surfaces, chondroitin sulfate surfaces, as well as bovine cartilage surfac
es. The amino acid structural units contained acidic, basic, or polar side
chains and were found to adhere reasonably well to the surfaces of glass an
d chondroitin sulfate. The formation of polymer-monomer complexes with the
addition of a basic monomer such as L-lysine to negatively charged polymers
such as poly(L-aspartic acid) and poly(L-glutamic acid) was found to resul
t in greater adhesive strength relative to homopolymers. Further improvemen
t in adhesion was observed in blends of poly(L-lysine) with polar poly(amin
o acids) such as poly(L-asparagine). Adhesion on wet cartilage surfaces was
the weakest measured but a priming approach designed to form electrostatic
or hydrogen bonds appears promising. We believe the strength of the adhesi
ves studied here is based on the ability of their constituent polymers and
monomers to form molecular entanglements and crosslinks for load transfer.
We also believe hydrogen bonds and electrostatic forces play a role in the
adhesion of the systems to the substrates probed in this work.