Low molecular weight Polyethylenimine does not stably conjugate to the surface of Gold Nanoparticles- they do not always produce a neat reversal in charge density (zeta potential measurements). My colleague and I thought that resuspending the PEI-conjugated Gold NPs in acidic medium would help with saturating the excess negative charges on the surface of the gold. We then proceeded to prepared the PEI solutions in a pH4 water prior to conjugation, but the PEI solutions consistently showed a measured pH of 10. Should we not worry about it now, and see what outcome we get after conjugation?