633 nm he ne laser

Hydrodynamic size and zeta potential analyses were performed using Brookhaven Instruments Particle Size Analyzer (90Plus) or Malvern Zetasizer Nano-ZS90 with 633 nm He-Ne laser (Malvern Instruments, Inc., Westborough, MA). Particles were diluted 1:5 in 1 mL of distilled water for these measurements. Scanning transmission electron microscopy (STEM) was performed using a Zeiss Supra 35 (Carl Zeiss Microscopy, LLC, Thornwood, NY) field emission scanning electron microscope with STEM detector. Samples were prepared by placing 10 μL of particles dispersed in DI water on Formvar/Carbon 200 mesh copper grids and allowing the samples to dry overnight. Images were captured using EHT = 20 kV. To determine whether particles aggregated in various solvents or in the presence of serum (FBS) or in complete cell culture media (RPMI+10% FBS), 500 μL aliquots of conjugated particles (OD 0.5) were incubated at room temperature with 2 mL of solvent for 5–7 days (as indicated in figure legends) and the color was recorded. Red/pink color was considered indicative of well-dispersed particles, whereas purple/blue to gray/colorless was considered to indicate increasing degrees of aggregation.

DLS measurements
were performed at 25 °C with a Malvern Zetasizer Nano ZSP apparatus
equipped with a 633 nm HeNe laser (Malvern Instruments, Malvern, UK).
The backscattering mode (scattered light is collected at an angle
of 173°) was employed for all the analyzed samples.

Particle size distribution, zeta potential (ζ), conductivity, and mobility were measured on a Nano-ZS Zetasizer with a 633 nm He–Ne laser (Malvern Instruments, Malvern, UK) and data were analyzed by Zetasizer Software Version 6.20 (Malvern Instruments, Malvern, UK). Before the measurements, all solutions were incubated for 30 min at 37 °C by shaking at 150 rpm, and were filtered through 0.2 μm syringe filter.