Tailoring elastin-like proteins towards environmental and bioanalytical applications
Peptides and proteins are emerging as novel building blocks to generate a wide range of biological materials for diverse applications. Genetic engineering provides the powerful route to create protein-based polymers with exquisite control of molecular weight and composition as well as tailored functionality. This dissertation research focused on designing a unique class of biopolymers, elastin like proteins (ELPs) as versatile building blocks for environmental and bioanalytical applications. Unlike conventional chemically synthesized polymers, ELPs consisting of the repeating pentapeptide (VPGVG) are specifically pre-programmed within a synthetic gene template. More significantly, ELP fusion proteins can be generated using recombinant DNA templates without altering the functionality of each domain. The intrinsic property of ELPs is the ability to undergo reversible phase transition based on hydrophobic interaction under a range of temperature, pH and ionic strength.
First, ELPs appended with synthetic phytochelatins (ECs) as nanoscale metal-binding biopolymers were developed. The improved selectivity and binding capacity provided by ELPEC20 were directly reflected in the enhanced cadmium extraction efficiency from contaminated soil. Beyond the creation of one-dimension functional biopolymers, block copolymers based on ELP sequences were engineered with metal binding functionality. The metal binding capability and capacity of resulting hydrogel was studied to demonstrate the functionality of polyhistidine and its environmental application for heavy metal removal.
Additionally, a new approach for fabricating protein arrays where a surface-oriented elastin-calmodulin (ELP-CalM) scaffold was developed capture recombinant proteins containing a M13 tag onto the surface. This protein-based approach provides a simple and robust platform for site-specific protein immobilization in a functionally active orientation without any covalent modification. Last, a simple platform for the direct conjugation and separation of highly luminescent CdSe-ZnS quantum dot (QD)-antibody complexes using a genetically engineered polyhistidine tagged elastin-Protein L fusion (His-ELP-PL) was developed. Simple separation of the QD-His-ELP-PL-IgG complex was achieved by thermally-triggered precipitation without any interference on the QD functionality. The utility of the biofunctionalized OD probes was demonstrated in an antibody array for the detection of carcinoembryonic antigen.