ELP purity was determined using SDS-PAGE gel analysis. A total of 10 μg of protein was mixed with SDS Laemmli loading buffer (1610747, Bio-Rad, Hercules, CA) containing 10% v/v β-mercaptoethanol, heated at 90 °C for 5 min and loaded onto 4–20% gradient Tris–glycine–SDS-PAGE gel (58505, Lonza, Walkersville, MD). The gel was stained using 10% w/v copper chloride and imaged using a ChemiDoc Touch Imaging system (Bio-Rad; Figure 2a ). Peak areas in each lane were calculated using ImageJ (National Institutes of Health, Bethesda, MD), and purity was estimated using the following equation:
where Apeak is the area of the protein band peak, and Atot is the total area under all the peaks per lane. The ELP critical micelle temperature was determined using a DU800 UV–vis spectrophotometer (Beckman Coulter) by performing temperature ramps at 1 °C/min and measuring OD at 350 nm. The temperature at the maximum first derivative of OD 350 nm was defined as the CMT (Figure 2b ). DLS was utilized to estimate the hydrodynamic radii of ELP nanoparticles (Figure 2c ). ELP samples (25 μM) in PBS were filtered at 4 °C (Whatman Anotop 0.02 μm, Sigma-Aldrich, St. Louis, MO) and monitored from 18 to 37 °C at the rate of 1 °C/min on a Wyatt Dynapro plate reader (Santa Barbara, CA) in a pre-chilled 384 black well plate.
where Apeak is the area of the protein band peak, and Atot is the total area under all the peaks per lane. The ELP critical micelle temperature was determined using a DU800 UV–vis spectrophotometer (Beckman Coulter) by performing temperature ramps at 1 °C/min and measuring OD at 350 nm. The temperature at the maximum first derivative of OD 350 nm was defined as the CMT (