## 3 Results
Figure 4: PDGF release for: whole blood (WB)—no activation and bovine thrombin (BT) activation; Harvest PRP (no activation, bovine thrombin—BT-activation, and activation using electric stimulation with pulses A and F); Eclipse PRP (no activation, bovine thrombin—BT-activation, and activation using electric stimulation with pulses A and F); EmCyte PRP (no activation, bovine thrombin—BT-activation, and activation using electric stimulation with pulses A and F). Note that there is no Donor 3 data for Eclipse. Figure 3: VEGF release for: whole blood (WB)—no activation and bovine thrombin (BT) activation; Harvest PRP (no activation, bovine thrombin—BT-activation, and activation using electric stimulation with pulses A and F); Eclipse PRP (no activation, bovine thrombin—BT-activation, and activation using electric stimulation with pulses A and F); EmCyte PRP (no activation, bovine thrombin—BT-activation, and activation using electric stimulation with pulses A and F). Note that there is no Donor 3 data for Eclipse. Finally, we note that the Eclipse growth factor release data include measurements only for donors 1, 2 and 4--donor 3 measurements were not included here due to challenges with PRP separation for this donor. We next assess the correlation of the various growth factors with the donor platelet levels and each other. Figure 5 assesses the linear correlation of EGF, VEGF, and PDGF release for Harvest and EmCyte PRPs treated with either PEF A or bovine thrombin (BT) with platelet count for the four donors. We selected PEF A because Figures 2-4 show that the general trends in the growth factors are relatively similar for both PEF waveforms. We did not consider Eclipse PRPs because we only had data for three donors rather than the complete set of four donors that we had for the other two types of PRP. Table 2 reports the correlation coefficients and \(p\)-values for the growth factors with the donor platelet levels and each other. For the PEF A combinations, the strongest positive correlation is with EGF, while PDGF slightly increases and VEGF slightly decreases for Harvest and remains approximately constant for EmCyte. Particularly interesting, Table 2 suggests that PDGF and VEGF are constant with increasing donor platelet concentration for EmCyte. Table 2 also indicates that PDGF and VEGF are negatively correlated, while PDGF and EGF are positively correlated for Harvest; EGF and VEGF are negatively correlated, but less strongly than PDGF with either VEGF or EGF. For EmCyte with PEF A, the correlations are generally weaker with only EGF and donor platelet concentration and EGF and PDGF exhibiting strong positive correlation. Although there is insufficient data to make a strong conclusion, as indicated by the \(p\)-values in Table 2, this data suggests that one may be able to select a platelet concentration method to tune growth factors relative to each other and with donor platelet concentration when using PEF activation. Figure 5: Assessment of the linear correlation of EGF, VEGF, and PDGF release with platelet concentration for the four donors for (**a**) the Harvest PRP and PEF A, (**b**) the EmCyte PRP and PEF A, (**c**) the Harvest PRP and BT, and (**d**) the EmCyte PRP and BT. Generally, EGF increased more strongly with donor platelet concentration under PEF activation than with BT activation, while PDGF and VEGF exhibited more variability. For the BT treatment of the two PRPs highlighted in Figure 5, EGF appears fairly constant with increasing platelet concentration for both Harvest (a slope of 0.027 pg/mL EGF/(10\({}^{9}\) L\({}^{-1}\) platelets) and \(R^{2}\) = 0.0306) and EmCyte (0.0166 pg/mL/(10\({}^{9}\) L\({}^{-1}\) platelets) and \(R^{2}\) = 0.3122) PRPs; Table 2 shows that it has a lower positive correlation with Harvest than with EmCyte. VEGF is nearly constant for both PRP based on Figure 5 and the correlation factor in Table 2. Similarly, PDGF has slight positive correlation factors for both PRPs.