a Comparison of the heat response of a protein (red) anda PNIPAm-based polymer nanoparticle (blue). Proteins denature (unfold) in response to heat, whereas the nanoparticles contract into a collapsed state. b Illustration of the “auto-nomous affinity switching” property of nanoparticels. c Effect of different polymer nanoparticles (2.0 mgmL−1) on the activity of lysozyme after heating. d Effect of NP1 and NP2 (2.0 mg mL−1) on the activity of different concentrations of lysozyme after heating.