Fine-tuning the pH trigger of self-assembly.
The creation of smart, self-assembling materials that undergo morphological transitions in response to specific physiological environments can allow for the enhanced accumulation of imaging or drug delivery agents based on differences in diffusion kinetics. Here, we have developed a series of self-assembling peptide amphiphile molecules that transform either isolated from molecules or spherical micelles into nanofibers when the pH is slightly reduced from 7.4 to 6.6, in isotonic salt solutions that simulate the acidic extracellular microenvironment of malignant tumor tissue. This transition is rapid and reversible, indicating the system is in thermodynamic equilibrium. The self-assembly phase diagrams show a single-molecule-to-nanofiber transition with a highly concentration-dependent transition pH. However, addition of a sterically bulky Gd(DO3A) imaging tag on the exterior periphery shifts this self-assembly to more acidic pH values and also induces a spherical micellar morphology at high pH and concentration ranges. By balancing the attractive hydrophobic and hydrogen-bonding forces, and the repulsive electrostatic and steric forces, the self-assembly morphology and the pH of transition can be systematically shifted by tenths a pH unit.
Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA.
Arijit
A
Ghosh
Mark
M
Haverick
Keith
K
Stump
Xiangyu
X
Yang
Michael F
MF
Tweedle
Joshua E
JE
Goldberger
D005682:Gadolinium; D006571:Heterocyclic Compounds / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008823:Micelles; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry; D010316:Particle Size; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry; D013499:Surface Properties; D013816:Thermodynamics
D006571:Heterocyclic Compounds; D008823:Micelles; D009942:Organometallic Compounds; D010455:Peptides; C062402:gadoteridol; D005682:Gadolinium