Fig. 1

Characteristics of ¹³¹I-EM@ALA. 4T1 tumor cells derived drug-loaded EM and empty EM assessed by TEM (a), DLS (b) and WB (c). Scale bar = 100 nm. Size (d) and Zeta potential (e) stability test of EM@ALA and EM in PBS for 7 days. f The representative radiochemical purity of ¹³¹I-EM@ALA. Radiolabeling stability test in PBS (g) and FBS (h) during 48 h (n = 3). i UV–vis spectrum of PpIX and PBS