Fig. 2

Stability studies of GNRs@PEG-Iso4. A Effect of one freeze–thaw cycle on the binding properties of GNRs@PEG-Iso4 to α5β1. The binding of GNRs@PEG-Iso4 to plates coated with or without α5β1 integrin before (0 cycle) and after one freezing (-80 °C) and thawing cycle (1 cycle), as detected with an anti-PEG rat antibody followed by HRP-labeled goat anti-rat antiserum, is shown. Mean ± SE of technical duplicates. Note that the freeze–thaw cycle does not affect the α5β1-binding properties of GNRs@PEG-Iso4. B-D Stability studies of GNRs@PEG-Iso4 and GNRs nanoparticles, performed by UV-IR absorption analysis of: i) nanoparticles before (0 cycle) and after one freezing (-80 °C) and thawing cycle (1 cycle) (B), ii) nanoparticles mixed with or without sodium chloride (5% NaCl, final concentration) (C), and iii) nanoparticles mixed with synthetic urine (90% urine, final concentration) (D). Note that the addition of sodium chloride caused a dramatic change in the UV-IR absorption spectrum of GNRs, but not of GNRs@PEG-Iso4, suggesting that the latter compound is protected from aggregation induced by high salt concentration