document: TAT-peptide conjugation procedure and analysis. The functional peptide cys-TAT was conjugated on the surface of rQβ@b-3WJ to enhance cell uptake.23 The Cys-TAT peptides (KYGRRRQRRKKRG-cys-SH) were conjugated to rQβ@b-3WJ by sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-1carboxylate (sulfo-SMCC; Sigma‒Aldrich, St. Louis, MO, USA) as a crosslinker. Briefly, 5 μL sulfo-SMCC solution (10 mg/mL in deionized (DI)-H2O) was added to a 600 μL solution of 2 μM rQβ@b-3WJ in PBS buffer (pH=7.4) for 30