Table 1. Atomic concentration (at%) of main elements estimated on the basis of the wide XPS spectra of ZnO and CuO NPs dispersed in DMEM or DMEM with FBS.

	N1s	O1s	Na1s	P2s	Cl2p	K2p	Ca2p	Zn2p3/2	Cu2p3/2
#1	2.4	45.6	9.4	1.7	0.7	0.2	2.2	19.5
#2	9.8	28.0	2.8	0.8	0.5	0.1	0.7	5.4
#3	10.3	30.1	2.6	1.0	0.5	0.1	1.8		5.9

#1, #2 and #3 represent ZnO NPs dispersed in DMEM, ZnO NPs dispersed in DMEM with FBS and CuO NPs dispersed in DMEM with FBS, respectively.