Elastin-like polymers (ELPs) are engineered repetitive polymers based on the Val-Pro-Gly-X-Gly (VPGXG) motif. ELPs are stimuli-responsive, sequence-tunable biomacromolecules used as surface coatings, linkers, or recognition scaffolds in biosensors. Their repeat architecture allows precise control of hydrophobicity, charge, thermal and ionic responsiveness, and placement of specific residues for purification or surface coupling.
For this work, two ELP variants were designed. ELP-V5 (C-sEL-V5) is a shorter polymer (155 amino acids, ~13.6 kDa) with a near-neutral isoelectric point (pI ≈ 7.23). It contains a C-terminal V5 epitope tag for specific sensing of Anti-V5 antibodies, and a His₆ tag for purification or oriented immobilization. Its design supports stable, site-specific attachment and selective antibody recognition. In contrast, ELP-TL (“tagless” – KI8) is a much longer polymer (460 amino acids, ~39.2 kDa) with high lysine content, resulting in a strongly basic pI (≈ 10.61) and substantial positive charge at physiological pH. It lacks the antibody-recognition epitope, making it an effective negative control for distinguishing specific ELP-V5–Anti-V5 sensing from non-specific polymer effects.
Carbon screen-printed electrodes (SPEs) were modified by diazonium chemistry with 4-carboxyphenyl groups, then activated using an EDC/NHS solution for covalent coupling. Following activation, one set of electrodes was capped with ethanolamine to block unreacted sites, producing the non-ELP control surface C/Carboxylphenyl/Ethanolamine (C/CP/EA). A second set was modified with ELP-TL, yielding C/Carboxylphenyl/ELP-TL (C/CP/ELP-TL). A third set was modified with ELP-V5, producing C/Carboxylphenyl/ELP-V5 (C/CP/ELP-V5).
Electrochemical impedance spectroscopy (EIS) characterized the behavior of these modified electrodes across varying salt concentrations, confirming polymer attachment and ion-sensitive surface changes. ELP-TL electrodes exhibited similar responses to ELP-V5 in salt environments, indicating comparable physicochemical behavior. Upon exposure to the Anti-V5 analyte, C/CP/EA and C/CP/ELP-TL surfaces showed negligible phase angle changes, while C/CP/ELP-V5 exhibited a distinct response, confirming that sensing arises from the specific ELP-V5:Anti-V5 interaction.
Support was provided by a National Science Foundation EPSCoR award (#2119237).