Sodium dihydrogen phosphate dehydrate

Ferric chloride hexahydrate (FeCl₃·6H₂O), sodium dihydrogen phosphate dehydrate (NaH₂PO₄), sodium chloride (NaCl), sodium borohydride (NaBH₄) and 30% hydrogen peroxide aqueous solution (H₂O₂) were purchased from Sinopharm Chemical Reagent Co., Ltd. mPEG-SH was obtained from Macklin. Singlet oxygen sensor green (SOSG) and CCK-8 were obtained from Dalian Meilun Biotechnology Co. Ltd. Chloroplatinic acid hexahydrate (H₂PtCl₆·6H₂O) and 1, 3-Diphenylisobenzofuran (DPBF) were purchased from Aladdin Co., Ltd. 2′,7′-Dichlorodihydrofluorescein diacetate (DCFH-DA, ≥ 97%) was purchased from Sigma-Aldrich. All regents were of analytical grade and used as received.

Four prepacked columns with Proteomix SCX‐NP10 resin were provided by Sepax Technologies, Inc. (Suzhou, China) with different sizes (i.e. 4.6 mm diameter and 250 mm length, 10 mm diameter and 250 mm length, 21.2 mm diameter and 250 mm length, 10 mm diameter and 50 mm length). Human IgG1 mAb sample with 8.71% acidic variants and 47.49% basic variants was kindly provided by a local biopharmaceutical company. The mAb mass weight is around 148 kDa and the pI is about 8.7. The CPB treatment was used to remove the C‐terminal Lys [7, 31‐32]. 15 μL CPB were added into 1 mL mAb sample with 1 g/L and kept for 30 min under 37℃. The proportion of main mAb and acidic variants was 88.47% and 11.53%, respectively after CPB treatment.
Antibodix WCX‐NP5 analytical column (4.6 mm diameter × 250 mm length) was purchased from Sepax Technologies, Inc. (Suzhou, China). Sodium chloride, sodium dihydrogen phosphate dehydrate and disodium hydrogen phosphate dodecahydrate were purchased from Sinopharm Chemical Reagent Co., Ltd (Shanghai, China). 2‐Morpholinoethanesulfonic acid monohydrate (MES) was acquired from Sigma‐Aldrich. Recombinant carboxypeptidase B (CPB) was obtained from Shanghai Yaxin Biotechnology Company (Shanghai, China). All other chemicals used in this study were of analytical grade.