Following the production phase of our project, we had 10 StarCore constructs to test. We set out to characterize their antimicrobial properties and mechanism of action. We had many questions in the following categories.

We quantified StarCore activity by determining their minimum inhibitory concentrations (MIC). We also evaluated their impact on bacterial growth by treating bacterial cultures with varying concentrations of StarCores and monitoring the OD600 through time. Representative results are shown in Figure 1. As a control, we also determined the MIC of Ovispirin, a commonly used AMP with no star-shaped geometry.

StarCores displayed a range of MICs, generally similar to control values. The top performing StarCore was the Ferritin-Alyteserin fusion, with an activity almost 10 times higher than that of the control.

We performed MIC determinations for both E. coli, a Gram-negative bacterium and B. subtilis, a Gram-positive strain. In general, StarCores displayed higher antimicrobial activities than the control Ovispirin in E. coli. While some StarCores exhibited a higher activity towards one bacterial class, others were largely nonspecific.

Differences in StarCore activity may be attributed to differences in membrane lipid charge and electrostatic potential, which vary among species and are believed to mediate AMP-membrane interactions. This idea is explored in more detail in the modelling and optimization sections.