Switching of self-assembly in a peptide nanostructure with a specific enzyme

Abstract

Peptide self-assembly has been shown to be a useful tool for the preparation of bioactive nanostructures, and recent work has demonstrated their potential as therapies for regenerative medicine. In principle, one route to make these nanostructures more biomimetic would be to incorporate in their molecular design the capacity for biological sensing. We report here on the use of a reversible enzymatic trigger to control the assembly and disassembly of peptide amphiphile (PA) nanostructures. The PA used in these studies contained a consensus substrate sequence specific to protein kinase A (PKA), a biological enzyme important for intracellular signaling that has also been shown to be an extracellular cancer biomarker. Upon treatment with PKA, this PA molecule becomes phosphorylated causing the high aspect-ratio filamentous PA nanostructures to disassemble. Treatment with an enzyme to cleave the phosphate group results in reformation of the filamentous nanostructures. We also show that disassembly in the presence of PKA allows the enzyme-triggered release of an encapsulated cancer drug. In addition, these drug-loaded nanostructures were found to induce preferential cytotoxicity in a cancer cell line that is known to secrete high levels of PKA. This ability to control nanostructure through an enzymatic switch could allow for the preparation of highly sophisticated and biomimetic materials that incorporate a biological sensing capability to enable therapeutic specificity.

Catalysis of Supramolecular Hydrogelation

“…We now added a fifth design principle 25 : 5) use a catalyst to enhance the rate of the final bond forming reaction leading to formation of the assembling molecule. To various degrees, these principles have been applied to controlling self-assembly through enzymatic catalysis 26,27,28,29,30,31 and synthetic catalysis 32,33 . Figure 1.…”

Biocatalytic Self-Assembly of Tripeptide Gels and Emulsions

“…The first example of the use of an alkaline phosphatase to trigger the formation of a hydrogel by the dephosphorylation of 9-fluorenylmethoxycarbonyl (Fmoc)-tyrosine phosphate [18][19][20] preceded several others. [21][22] Hirst et al have shown that the amount of biocatalyst used can direct the self-assembly pathway resulting in (kinetic) control of the supramolecular organization of the final supramolecular structure. 23 They also demonstrated that these kinetically locked gels may be ÔunlockedÕ to access a minimum energy state by performing a heat/cool cycle.…”

Recent advances in self-assembled peptides: Implications for targeted drug delivery and vaccine engineering

“…Peptide-based hydrogels have prominent advantages over traditional polymeric hydrogels which include biodegradability, low bioaccumulation and toxicity, spontaneous formation without the use of harmful reagents (such as chemical crosslinkers), and the facile incorporation of cell-specific bioactive moieties. Peptide-based hydrogels are also cost effective, easily synthesized and responsive to external stimuli, including temperature, ionic strength, pH, light, enzyme and magnetic fields [41][42][43][44][45][46][47]. The responsiveness of these peptide hydrogels to biological stimuli attributed to their ability to sense changes to the local environment and release therapeutics in a controlled manner [47].…”

“…Peptide-based hydrogels are also cost effective, easily synthesized and responsive to external stimuli, including temperature, ionic strength, pH, light, enzyme and magnetic fields [41][42][43][44][45][46][47]. The responsiveness of these peptide hydrogels to biological stimuli attributed to their ability to sense changes to the local environment and release therapeutics in a controlled manner [47]. The hydrogelation of peptide hydrogels is easily modified through the attachment of chemical and biological moieties [48].…”