Figure 6a: GHK and GHK-PEG did not induce cytotoxicity in SH-SY5Y cells. To test the effects of GHK and GHK-PEG on cytotoxicity in SH-SY5Y cells, cells were plated in 96 well plates at 5000 cells per well and incubated for 24 hrs. Cells were either not treated or treated with GHK or GHK-PEG at 1 or 10 nM for 24 hrs. The effect of each treatment on cytotoxicity was assessed by measuring protease activity using the non-cell permeant substrate bis-AAF-R110 using the ApoTox-Glo Triplex Assay. The results for each treatment were expressed as fold control and compared between control and treated cells using analysis of variance (ANOVA). n=3; *p≤0.05. GHK and GHK-PEG did not induce cytotoxicity in SH-SY5Y cells. To test the effects of GHK and GHK-PEG on cytotoxicity in SH-SY5Y cells, cells were plated in 96 well plates at 5000 cells per well and incubated for 24 hrs. Cells were either not treated or treated with GHK or GHK-PEG at 1 or 10 nM for 24 hrs. The effect of each treatment on cytotoxicity was assessed by measuring protease activity using the non-cell permeant substrate bis-AAF-R110 using the ApoTox-Glo Triplex Assay. The results for each treatment were expressed as fold control and compared between control and treated cells using analysis of variance (ANOVA). n=3; *p≤0.05.