The T7 Riboregulation System works by a “three-lock system.” The first lock is the cis- repressing RNA (crRNA), which is induced bysopropyl β-D-1-thiogalactopyranoside (IPTG). The second lock is the trans-activating RNA (taRNA), which is induced by anhydrous tetracycline (ATC). If the taRNA is unlocked, it will bind to the crRNA, removing the hairpin and making the ribosomal binding site accessible for ribosomal binding, leading to translation of a specific protein, in this case, T7 RNA Polymerase. This system was initially developed by Dr. Farren Isaacs, and has been shown to work with chloramphenicol resistance (chloramphenical acetyl transferase gene) in place of the T7 gene. The plasmid was synthesized via Gibson assembly, and confirmed by sequencing.

Currently the riboregulation system may have an issue with the internal T7 sequence, and while sequencing has been done, no successful data has been obtained.

Experimental plan for the GFP fluorescence assay testing the efficacy of the T7 riboregulation system. The T7 riboregulation system, pZE21_A12C_T7RNA, would express sfGFP behind a T7 promoter, in the plasmid pZA21. Either plasmid, and both plasmids together, were transformed into ECNR2 and induced with either IPTG and ATC. ECNR2 is the ancestral strain. A positive control was the same pZA21_T7sfGFP plasmid in ECNR2, and the same T7 RNA polymerase gene inserted in a regular pZE21 plasmid with a pLtetO promoter, and a negative control with the pZA21_T7sfGFP in ECNR2 without any plasmid that contains T7 RNA.

Preliminary proof of concept testing was conducted on a commercially available MAP-based product known as Cell-Tak ^TM. Cell-Tak^TM is designed to facilitate cell adhesion to normally non-biocompatible surfaces such as microscope slides and petri dishes. We deposited ~20 µg films of Cell-Tak onto borosilicate substrates and proceeded to erode them under deionized H₂O and 5% acetic acid. The results from this experiment are presented below and illustrate the design of our assay to test a variety of solvent and erosion conditions on MAP films. A balance that can read to uncertainties of 1 µg was used to determine the mass of protein remaining after subjecting the substrate to erosion. An exponential decay curve was fitted to these experiments giving decay rates of 0.002 µg/pass and 0.046 µg/pass for deionized H₂O and 5% acetic acid, respectively. As lower pH reverses the coordination of L-DOPA, it is expected that the acidic conditions engender the higher rate of decay. This experiment presents a preliminary result that validates our ability to apply erosion onto MAP-coated surfaces. We intend to apply a similar protocol to metal and plastic surfaces as well as erode surfaces under different pH conditions to provide a more comprehensive picture of the optimal conditions for mussel adhesion.

A contact angle measurement of a Cell-Tak^TM was recorded and served as an indication for presence of peptide on surfaces. The contact angle is measured between the surface of the drop and the table-top. Larger contact angles are indicative of more hydrophobic surfaces while shallower contact angles correspond to more wettable surfaces. A contact angle of 25.053º was obtained between an untreated silica substrate and a 2 µL drop of DI H₂O. However, when surfaces were treated with the MAP, the contact angle increased to 62.007º, indicative of an increase in the hydrophobicity of our substrate. This result validates the evolutionary need for mussels to secrete proteins that are resistant to water in order to survive and anchor themselves in constantly wet environments.