Table 1. Zeta potential and NMR measurements of PEG-coated particles.

For the zeta potential measurements, each particle solution was 0.1 mg/ml of particles in 1 mM KCl. Measurements were done on a Brookhaven NanoBrook ZetaPALS Potential Analyzer. Three trials were done where each trial was 10 runs and each run was 10 cycles. Values reported are the average zeta potential for the 30 runs. NMR measurements were performed as described in Materials and methods. Values are estimates of the nanomoles of polyethylene glycol (PEG) per milligrams of particles. To calculate this, we have to assume all the PEG on the surface is a single MW. It is therefore assumed all the PEG on the surface is PEG 5 kDa.

Surface modification of PS particles	Zeta potential (mV)	Nanomoles PEG/mg particles
PEG 5 kDa	−18.87 ± 1.78	5.5
PEG 5 kDa w/ mPEG 1 kDa backfill	−7.66 ± 2.12	4.6
PEG 5 kDa w/ mPEG 350 Da backfill	−9.99 ± 1.65	4.3
PEG 5 kDa w/ mPEG 5 kDa backfill	−14.56 ± 1.78	4.0
PEG 2 kDa	−39.59 ± 2.41	9.4
Carboxylate-coated (no PEG)	−61.36 ± 12.40	0.0