Subcategory: Materials Science
Douglas MacPherson - City University of New York
Co-Author(s): Brian Zeglis, PhD, City University of New York ; Rein Ulijn, PhD, City University of New York
Cancers metastasize, making the disease difficult to effectively detect and treat. Metastatic cancer cells uniquely overexpress a class of enzymes called matrix metalloproteinases (MMPs). MMP9 expression and activity is correlated with metastasis and tumor spread in breast and prostate cancer. Using enzyme-cleavable peptide sequences, we will be able to harness these MMPs for use against the disease. My central hypothesis is that radiolabeled enzyme-responsive peptides will provide a means to image metastatic cancer characterized by elevated MMP expression. Our laboratory has developed enzyme-responsive self-assembling peptide amphiphiles (ERSAPAs), that adopt a micelle structure, and switch conformation to a fiber when cleaved by enzymes. Short hydrophobic peptide fibers have been demonstrated to adhere to tumor tissue. We propose to tether a radioactive iodine molecule to an ERSAPA, permitting it to travel freely in the body, and when it arrives at a site of MMP9-expressing cancer tissue, the resulting cleavage and fiber formation will ?anchor? the radio-label at the cancer site. Using established peptide design rules, we have synthesized peptides with three distinct regions: (i) a hydrophobic fiber-forming sequence, (ii) a hydrophilic sequence that adjusts the amphiphilic balance of the peptide to favor micelle formation, and (iii) an MMP9-cleavable sequence separating the hydrophilic and hydrophobic regions. Our negative control consists of a micelle-forming peptide sequence in which the MMP-cleavable sequence is scrambled, preventing cleavage. Our positive control is a micelle-forming, cleavable peptide that does not have a radio-ligand attached. We have used atomic force microscopy (AFM) and fluorescence experiments to determine peptide assembly and nanostructure formation. Liquid chromatography ? mass spectrometry (LCMS) has been used to determine cleavage of the peptide by the enzyme. Thus far, we have demonstrated micelle formation of our peptides, MMP-cleavage of our positive control peptide, and effective ?cold? iodine coupling to the peptides. Remaining work involves demonstrating cleavage and micelle ?to? fiber transition of the iodine-labeled peptide. Following this, we will assess the tumor-targeting effectiveness using radioactive ‘hot’ iodine in murine models of MMP9 -expressing cancer. This technology will provide a nuclear imaging agent established from an enzyme-responsive nanoparticle, and will be the first imaging nanoparticle to undergo a programmed morphological switch. References: Kalafatovic D, Nobis M, Javid N, Frederix PW, Anderson KI, Saunders BR, Ulijn RV. MMP-9 triggered micelle-to-fibre transitions for slow release of doxorubicin. Biomaterials science. 2015;3(2):246-9. Son J, Kalafatovic D, Kumar M, Yoo B, Cornejo MA, Contel M, Ulijn RV. (2019) Customizing Morphology, Size, and Response Kinetics of Matrix Metalloproteinase- Responsive Nanostructures by Systematic Peptide Design. ACS Nano. 13 (2), pp 1555? 1562.
Funder Acknowledgement(s): This work is supported by the National Science Foundation CREST Center for Interface Design and Engineered Assembly of Low Dimensional systems (IDEALS), NSF grant number HRD-1547830.
Faculty Advisor: Rein Ulijn, email@example.com
Role: While the experimental design builds on the work of previous students, I am responsible for the data produced through the experimental techniques mentioned above. Specifically, atomic force microscopy, liquid chromatography-mass spectrometry of the enzymatic reactions, encapsulation of fluorescent molecules within peptide aggregates and analysis with a fluorimeter. We also have some limited Fourier transform Infared Spectroscopy data to evaluate secondary structures of the peptides. This is in addition to solid phase peptide synthesis to make some of the studied peptides.