Sialic acid quantification kit

RBC-NPs were first prepared with 100 nm PLGA cores and RBC membrane vesicles. For glycoprotein quantification, proteins exposed on the RBC-NP surfaces were trypsinized by incubating 1 mL of 1 mg mL⁻¹ RBC-NPs with 5 μg of trypsin (G-Biosciences, St. Louis, MO) at room temperature for 2 h. Sialic acid removal from RBC-NPs was performed by incubating 1 mL of 1 mg mL⁻¹ of RBC-NPs in water with 100 units of sialidase (Roche Diagnostics, Indianapolis, IN) at room temperature for 2 h. The samples were then centrifuged at 200,000 × g for 45 min using an Optima L-90K Ultracentrifuge (Beckman Coulter, Brea, CA), and the supernatant was collected and examined for glycoprotein and sialic acid content. To quantify glycoprotein, the supernatant was examined using Glycoprotein Detection Reagent (Thermo Scientific) following manufacturer’s instructions. To quantify sialic acid, the supernatant was examined using Sialic Acid Quantification Kit (Sigma-Aldrich, St. Louis, MO) following the manufacturer’s instructions. Equivalent amounts of RBC ghosts and bare PLGA cores were used as a positive and a negative control, respectively.