Fig. 2.

The different interactions of free SNARF-5F and SNARF-PAA NP with human serum albumin (HSA). a Direct observations of the free SNARF-5F buffered at different pH of 6, 7, 7.4 and 8. The differences in color can be seen for solutions with and without HSA (4 mg ml⁻¹). b Direct observations of SNARF-PAA NPs buffered at different pH of 6.0, 7.0, 7.4 and 8.0. No obvious difference in color can be seen for solutions with and without HSA (4 mg ml⁻¹). c pH calibration curves (absorbance at 600 nm divided by absorbance at 565 nm) of free SNARF-5F with (blue) and without (red) HSA. Significant changes caused by the interaction of SNARF-5F with HSA can be noticed. d pH calibration curves of SNARF-PAA NPs with (blue) and without (red) HSA. No noticeable changes can be noticed, demonstrating the advantages of having the dye encapsulated in the PAA matrix