3,3′,5,5′-Tetramethylbenzidine (TMB, 99%, CAS 54827-17-7) was purchased from Alfa Company. β-d-Glucose (β-d-Glu, 99%, CAS 28905-12-6) was purchased from TCI Company. Phosphate-buffered saline (PBS), trypsin (1 : 250, CAS 9002-07-7), Dulbecco’s modified eagle medium (DMEM), high-glucose DMEM (4500 mg L−1) and fetal bovine serum albumin (FBSA, 98%, CAS 9048-46-8) were purchased from Gibco, USA. HeLa cells were purchased from Beyotime Biotechnology Co. Ltd and Cell Counting Kit-8 (CCK8) was obtained from Beyotime Biotechnology Co. Ltd. Calcein acetoxymethyl ester (Calcein-AM, 90%, CAS 148504-34-1)/Propidium iodide (PI, 95%, CAS 25535-16-4) staining reagents were purchased from Yeasen Biotechnology (Shanghai) Co. Ltd. 5,5-Dimethyl-1-pyrroline N-oxide (DMPO, 97%, CAS 3317-61-1) was bought from J&K Scientific Company. Ferric chloride hexahydrate (FeCl3·6H2O, 98%, CAS 7705-08-0), ferrous chloride tetrahydrate (FeCl2·4H2O, 99%, CAS 13478-10-9), oleic acid (OA, 90%, CAS 112-80-1), polyoxyethylene oxypropylene ether block copolymer (Pluronic F127, MW 12600, CAS 9003-11-6), poly(d,l-lactic acid-co-glycolide) (PLGA (50 : 50), MW 7000–17000, CAS 26780-50-7) were purchased from Sigma-Aldrich Company. Glucose oxidase (GOx, 100–250 U mg−1, CAS 9001-37-0) was purchased from Shanghai Yuanye Biotechnology Co. Ltd. Ammonia (NH3·H2O, 25%, CAS 1336-21-6), acetone (C3H6O, 97%, CAS 67-64-1), n-octane (n-C8H18, 96%, CAS 111-65-9), chloroform (CHCl3, 97%, CAS 67-66-3), hydrogen peroxide (H2O2, 30%, CAS 7722-84-1), terephthalic acid (TA, 99%, CAS 100-21-0), citric acid monohydrate (CA·H2O, 99%, CAS 5949-29-1), potassium dihydrogen phosphate (KH2PO4, 99%, CAS 7778-77-0), disodium hydrogen phosphate (Na2HPO4, 99%, CAS 7558-79-4), ethanol (C2H5OH, 99.5%, CAS 64-17-5) and methanol (CH3OH, 99.5%, CAS 67-56-1), were analytically pure and obtained from Sinopharm reagent company. All reagents were analytical grade and were used directly without further purification. Throughout, Milli-Q ultrapure water was used in all needed experiments.