As shown in
Fig. 2a, Se nanoparticles loaded with coumarin-6 (SeNPs) were synthesized using Na
2SeO
3 as the Se source and ascorbic acid (Vc) as the reducing agent, according to previously described methods [
28]. Chitosan (Cs) connected RGD polypeptide and Cs connected S2.2 aptamer were then decorated to the SeNPs
via electrostatic interactions to synthesize an ovarian cancer-target diagnostic system (Se@RGD/S2.2). Following preparation, the morphology and composition of Se nanosystem was characterized by atomic force microscopy (AFM) and transmission electron microscopy (TEM). As shown in
Figs. 2b and
c and Fig. S2 (Supporting information), SeNPs and Se@RGD/S2.2 exhibited uniform nanospheres with an average size of approximately 50 nm and 70 nm, respectively. Meanwhile, EDS elemental mapping analysis showed that elemental Se was present in the Se@RGD/S2.2 nanosystem (
Figs. 2d and
g). Moreover, AFM images showed that Se@RGD/S2.2 was evenly distributed with an average height of approximately 30 nm (
Figs. 2e and
f). As shown in
Figs. 2h–
j, the hydrodynamic diameters and zeta potential of free SeNPs were 46.1 nm and −3.2 mV, respectively. After the surface of SeNPs was connected with RGD polypeptide/aptamer S2.2/RGD and S2.2 mixed peptides, the nanoparticle size was increased to 150–183 nm, and the zeta potential was reversed to positive charged, demonstrating the successful delivery of targeted peptides to the SeNPs. The fluorescence spectra of coumarin 6 showed that coumarin 6 exhibited green fluorescence at 530 nm when excited with at 334 nm wavelength (Fig. S3 in Supporting information). In addition, the fluorescence spectra of Se@RGD/S2.2 showed that Se@RGD/S2.2 exhibited green fluorescence at 530 nm when excited with at 460 nm wavelength, implying that Se@RGD/S2.2 successfully loaded coumarin-6 (
Fig. 2k). Furthermore, Se@RGD/S2.2 and free SeNPs showed the same ultraviolet (UV) absorption peak, confirming that the structure of the Se nanosystem remained intact (
Fig. 2l). Taken together, these results demonstrate that the Se@RGD/S2.2 nanosystem was successfully prepared.