Figure 4.

(a) Normalized fluorescence intensity as a function of pH for Cy5-conjugated P(DPA_x-DBA_y) nanoprobes. (b) Derivative fluorescence plot (d_F/d_pH, data from a) as a function of pH for P(DPA_x-DBA_y) vs P(DEA₄₀-D5A₄₀) nanoprobes. Use of methacrylate monomers with close hydrophobicity (i.e., DPA/DBA vs DEA/D5A) resulted in much sharper pH transitions. (c) Linear relationships of the nanoprobe pH_t vs molar fraction of the less hydrophobic monomer for different copolymer compositions. These correlations serve as the standard curves for selecting the optimal copolymer composition to achieve an operator-predetermined pH_t. (d) Representative library of UPS nanoprobes with 0.3 pH increment covering the physiologic range of pH 4–7.4. All nanoprobes were conjugated with the Cy5 dye. Polymer concentrations were at 0.1 mg/mL.