NP cross-linker Diameter (nm) Polydispersity Index Zeta potential (mV) Ce6 loading (Ce6/HSA molar ratio) Glutaraldehyde 298 ± 6 0.13 ± 0.01 -12.6 ± 0.3 9.6 ± 0.9 DSP 295 ± 5 0.24 ± 0.02 -18.0 ± 0.6 9.1 ± 0.7

Table 1: Characteristics of Ce6-HSA NP cross-linked with glutaraldehyde or DSP.