Sergey E. Paramonov

Peptides that non-covalently functionalize single-walled carbon nanotubes to give controlled solubility characteristics

Methods which solubilize single-walled carbon nanotubes (SWNTs) in water as individuals, not bundles, while retaining their unique electronic, photonic and mechanical properties are highly desirable. Furthermore, functionalization with a diverse array of selectable chemical moieties would allow the range of useful applications to be significantly extended and may permit the designed assembly of SWNT networks. This paper presents a series of peptides that non-covalently solubilize carbon nanotubes in water using a design motif that combines a combinatorial library sequence to bind to nanotubes with a rationally designed section to create environmentally tuned solubility characteristics. The ability of the peptides to individually disperse carbon nanotubes without altering their electronic structure is shown by vis-NIR absorbance, fluorescence, and regular and vitreous ice cryo-TEM. Identification of the species composition of each sample by NIR fluorescence reveals that the peptides exhibit some diameter selectivity. Additionally, one of the rationally designed modifications addresses the poor stability of non-covalently solubilized SWNT suspensions by including cysteine residues for covalent crosslinking between adjacent peptides.

Biomimetic self-assembled nanofibers

Peptide-amphiphiles, peptides to which a non-peptidic hydrophobic moiety has been added to the N or C terminal end, have been demonstrated to be a versatile method for simultaneously controlling nanostructure and chemical functionality. These amphiphiles are able to self-assemble, in a controlled fashion, into nanofibers with diameter between 6-10 nm and with length in excess of 1000 nm. At proper concentration these nanofibers form a viscoelastic gel capable of entrapping living cells and eliciting specific responses from them. Because of the flexibility of the display of chemical functionality on a controlled nanofibrous scaffold, applications for peptide-amphiphiles have been proposed including heterogeneous catalysis, nanoelectronics, drug delivery, and tissue engineering.

Tuning the mechanical and bioresponsive properties of peptide-amphiphile nanofiber networks.

Here we describe peptide amphiphiles (PAs) which can be self-assembled into nanofiber networks using divalent ions. These networks possess several key properties of extracellular matrix (ECM) including cell-adhesive ligands, enzyme-mediated degradation and self-assembly into hierarchical organization. The self-assembly of PAs and growth of nanofibers could be controlled by modifications of the chemical structure of the PA and/or addition of divalent ions. Altering the length of PAs alters the viscoelastic properties and degradation kinetics of nanofiber networks. Neural cells were successfully encapsulated within nanofiber networks by self-assembly of PAs. Cell adhesive ligands containing nanofiber networks supported neural cells growth, and their cellular behaviors depended on the concentration of cell adhesive ligands. Therefore, we have demonstrated that mechanical properties, degradability, and bioactivity of nanofiber networks could be tuned by altering the chemical composition and the length of PAs.