## 4 Discussion  
This experimental study explored the effect of PEF treatment for three different types of PRPs. While our previous platelet activation experiments using electrical stimulation primarily focused on the Harvest PRP, with some initial results on whole blood [31], this paper introduces PEF activation of PRPs generated using commercially available separation kits from Eclipse and EmCyte. PRP from Harvest, Eclipse and EmCyte cover a relevant range of platelet concentration from 2\(\times\) to 5.8\(\times\), include both high red blood cell content (red) PRP (Harvest) and low red blood cell content (white) PRP (Eclipse, EmCyte), and scan also a sizeable range of WBC content. While the experiments described here have specific limitations, particularly the consideration of blood samples from a limited number of donors (four) and growth factors, they are the first to consider growth factor differences across these three types of PRP. A published study from our research used only one type of PRP but measured a larger number of growth factors [26]. Future investigations could consider more donors, measure additional growth factors, and consider in vivo wound healing using electrically stimulated PRP. Our previous electrical activation of PRPs induced just growth factor release with no clotting when no CaCl\({}_{2}\) or specific quantities of CaCl\({}_{2}\) were added to the PRP prior to exposure to PEFs [29]. In this study, we did not add CaCl\({}_{2}\) prior to PEFs, and we did not visually observe any clotting post PEF treatment. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **PLT** & \multicolumn{2}{c}{**VEGF**} & \multicolumn{2}{c}{**EGF**} & \multicolumn{2}{c}{**PDGF**} \\ \hline
**Harvest PRP and PEF A** & \(r\) & \(p\) & \(r\) & \(p\) & \(r\) & \(p\) & \(r\) & \(p\) \\ VEGF & \(-0.30\) & \(0.70\) & & & \(-0.40\) & \(0.60\) & \(-0.86\) & \(0.14\) \\ EGF & \(0.72\) & \(0.28\) & \(-0.40\) & \(0.60\) & & \(0.70\) & \(0.30\) \\ PDGF & \(0.29\) & \(0.72\) & \(-0.86\) & \(0.14\) & \(0.70\) & \(0.30\) & \\
**EmCyte PRP and PEF A** & & & & & & \(-0.05\) & \(0.96\) & \(-0.15\) & \(0.85\) \\ VEGF & \(0.04\) & \(0.96\) & & & & \(0.72\) & \(0.28\) \\ EGF & \(0.73\) & \(0.27\) & \(-0.05\) & \(0.96\) & & & \(0.72\) & \(0.28\) \\ PDGF & \(0.05\) & \(0.95\) & \(-0.15\) & \(0.85\) & \(0.72\) & \(0.28\) & \\
**Harvest PRP and BT** & & & & & \(-0.99\) & \(0.02\) & \(-0.69\) & \(0.1\) \\ VEGF & \(-0.01\) & \(0.99\) & & & & \(0.66\) & \(0.34\) \\ EGF & \(0.18\) & \(0.83\) & \(-0.99\) & \(0.02\) & & & \(0.66\) & \(0.34\) \\ PDGF & \(0.12\) & \(0.88\) & \(-0.69\) & \(0.1\) & \(0.66\) & \(0.34\) & \\
**EmCyte PRP and BT** & & & & & & \(-0.16\) & \(0.84\) & \(-0.80\) & \(0.20\) \\ VEGF & \(0.11\) & \(0.89\) & & & & \(0.68\) & \(0.32\) \\ EGF & \(0.56\) & \(0.44\) & \(-0.16\) & \(0.84\) & & & \(0.68\) & \(0.32\) \\ PDGF & \(0.43\) & \(0.58\) & \(-0.80\) & \(0.20\) & \(0.68\) & \(0.32\) & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Correlation matrix comparing the growth factors with donor platelet concentration and each other for the various treatments with correlation factor \(r\) and \(p\) values. PEFs A and F triggered growth factor release for all PRPs, indicating that PEFs may be used for electrical activation for any of these PRP systems. While EmCyte PRP has almost 1.5\(\times\) in platelet concentration compared to Harvest, we do not observe similar scaling of growth factor release from these two PRPs. While BT clotted all three PRPs, the PEFs used here did not trigger visible clotting in any PRP, confirming prior results that using PEFs with no added calcium facilitates only growth factor release, but without clotting [29]. This finding confirms that PEF treatment may be utilized for injectable PRP clinical applications, where non-activated PRP is largely used today. EGF release is much higher here with PEF for EmCyte and Harvest compared to BT, confirming prior results obtained in Harvest PRP activation experiments. PDGF and VEGF release for these two PRPs is more comparable between BT and PEF.