Peroxidase type 2 from horseradish p8250 50ku

Carboxylated polystyrene NPs of different sizes were purchased from Life Technologies (Carlsbad, CA, USA). Specifically, the materials (with catalog numbers) used were 20 nm (F8783), 40 nm (F8793), 100 nm (F8797) and 500 nm (F8813) NPs with dark red (λ_ex/λ_em = 660 nm/680 nm), red (λ_ex/λ_em = 580 nm/605 nm), blue (λ_ex/λ_em = 350 nm/440 nm) and yellow-green (λ_ex/λ_em = 505 nm/515 nm) fluorescence, respectively. Methoxypolyethylene glycol amine 2000 (mPE-Gamine 2KDa) (06676), methoxypolyethylene glycol amine 750 (mPEGamine 750 Da) (07966), n-[3-dimethylaminopropyl]-n-ethyl, n-[3-dimethylaminopropyl]-n-ethyl [EDC] (E1769), MES hemisodium buffer (M8902), N-Hydroxysuccinimide (NHS) (56405), and Peroxidase type II from horseradish (P8250–50KU) were purchased from Sigma Aldrich (St. Louis, MO, USA). ImmPACT DAB peroxidase (HRP) substrate (SK-4105) was purchased from Vector laboratories (Burlingame, CA, USA). Slide-A-Lyzer Cassettes (20 K) (66003) and Kimwipes (06–666) were purchased from ThermoFisher scientific (Waltham, MA, USA). Vectashield antifade mounting medium (H-1000) from Vector Labs (Burlingame, Ca, USA) and Anti-mouse IgG antibody 488 (ab150105) from Abcam (Cambridge, UK) were purchased.