Nanoseries zetasizer zs 90

The morphology and size of PLGA-THPC nanostars were examined using a transmission electron microscope (TEM; Tecnai F20; FEI company, Hillsboro, OR, USA) at an accelerating voltage of 120 kV. A drop of 10 μL of a previously prepared PLGA-THPC nanostar suspension was pipetted onto carbon-coated copper grids (Ted Pella, Redding, CA, USA) and air-dried. The diameter of nanostars was measured using ImageJ (version 1.45S, NIH, Bethesda, MD, USA) for at least 20 particles. The size and surface charges of nanostars were measured by dynamic light scattering using a Nanoseries Zetasizer ZS 90 (Malvern Instruments Ltd., Malvern, Worcestershire, UK), with backscattering detection at 90°.

The size and surface charge of particles before and after PLL-Trolox conjugation on melatonin encapsulated PLGA nanoparticles were measured using dynamic light scattering (DLS) and zeta potential measurements, respectively using a NanoSeries Zetasizer ZS 90 (Malvern). Samples were prepared in deionized (DI) water. Encapsulation of melatonin in PolyRad nanoparticles was assessed by measuring the absorbance at 300 nm using a microplate reader (BioTek Synergy 2) and a melatonin standard curve (S.I. Figure 1). The percentage of melatonin encapsulation capacity was calculated using the following Eq. 1: $$\%encapsulationefficiency=\frac{M_0-\left(M_u-M_s\right)}{M_0}\times 100$$ where, M₀ = Initial melatonin mass, M_u = Melatonin mass in unwashed suspension and M_s = Melatonin mass in supernatant $.$