Fig. 2.

Characteristics of the synthesized polypeptides and the topological morphology. a Turbidity profiles of P4–P8. P4–P6 were UCST-type ELPs, P7 was a LCST-type ELP, and P8 was a thermo-inert ELP. b Using of 4-(2-carboxypyrrolidin-1-yl)-7-(N, N-dimethylamino-sulphonyl)-2,1,3-benzoxadiazole (DBD) to monitor the collapse of P4–P6 (200 μM). DBD-labeled ELPs were hydrated and fluorescence off at 37 °C, whereas turned on due to the dehydrate and collapse of the ELPs chains at 4 °C. c Rheological characterization of ELP gels (P9 and P10). Average Gʹ and Gʺ values were recorded at a fixed frequency (0.5 Hz) and strain (5%) at 37 °C across a period of 70 min. Error bars indicate s.d. (n = 3) d Differential scanning calorimetry (DSC) thermograms for determining the phase transition temperatures. e Photographs of P4 and P7–P10 in aqueous solutions at 4 °C and 37 °C. P9 volumes at 4 and 37 °C were indicated as V ₀ and V ₁, respectively. f Confocal images of DBD-labeled P4 and P7–P10 at 4 and 37 °C. ELP aggregation was monitored by the fluorescence changes of the polarity-sensitive probe DBD. NPs represented nanoparticles; VPT represented volume phase transition. g SEM images of P4 and P7–P10 at 4 and 37 °C. Scale bars, 4 μm for P4, P7, and P8; 50 μm for P9 and P10