K2hpo4 3h2o

The synthesis of ox-CNO was already reported elsewhere [61 (link)]. Nanocomposite films were produced using chitosan of low molecular weight (molecular weight (Mw.) 144,000 g/mol, deacetylation degree 89–90%), poly(vinyl alcohol) (PVA; hydrolysis degree 87–89%, Mw. 93,000 g/mol, Sigma-Aldrich, Palo Alto, CA, USA). CS solutions were prepared using glacial acetic acid from Merck (Burlington, MA, USA). Simulated biological fluid (SBF) was prepared using NaCl, K₂HPO₄·3H₂O, CaCl₂, Na₂SO₄, and tris-(hydroxymethyl aminomethane) ((CH₂OH)₃CNH₂) acquired from Sigma Aldrich (Palo Alto, CA, USA), a well as NaHCO₃, KCl, and MgCl₂·6H₂O from Fisher Chemical (Pittsburgh, PA, USA), and hydrochloric acid (HCl) from Merck (Burlington, MA, USA). All reagents were analytical grade and used without any purification unless otherwise stated.

α-Glucosidase (EC3.2.1.20) from S. cerevisiae, 4-nitrophenyl-α-D-glucopyranoside (PNP-G) as a synthetic substrate, alloxan, and dimethyl sulfoxide (DMSO) were purchased from Sigma (St. Louis, MO, USA), acarbose was biological reagent, and K₂HPO₄·3H₂O, NaOH, and others were of reagent grade. Norathyriol and mangiferin were provided by Research Department of Kunming Pharmaceutical Corporation (Kunming, China).

For GO synthesis, graphite flakes (99.8%) were used (Alfa Aesar, Tewksbury, MA, USA). Concentrated sulfuric acid (H₂SO₄), potassium permanganate (KMnO₄), hydrogen peroxide (H₂O₂) and isopropanol were supplied from Merck (Burlington, MA, USA). For the production of the films, CS of low molecular weight (144,000 g/mol) and a deacetylation degree between 89% and 90%, PVA with hydrolysis between 87% and 89% and viscous molecular weight of 93,000 g/mol (Sigma-Aldrich, Palo Alto, CA, USA). Glacial acetic acid was purchased from Merck. For the elaboration of the simulated biological fluid, NaCl, K₂HPO₄ ·3H₂O, CaCl₂, Na₂SO₄, tris-(hydroxymethyl aminomethane) [(CH₂OH)₃CNH₂] were acquired from Sigma-Aldrich; NaHCO₃, KCl, MgCl₂ ·6H₂O from Fisher Chemical (Pittsburgh, PA, USA) and hydrochloric acid (HCl) from Merck. All reagents used were analytical grade.

For graphene oxide synthesis, graphite flakes (99.8%) were used (Alfa Aesar, Tewksbury, MA, USA). Concentrated sulfuric acid (H₂SO₄), potassium permanganate (KMnO₄), hydrogen peroxide (H₂O₂), and isopropanol were supplied by Merck (Burlington, MA, USA). For the production of the films, chitosan of low molecular weight (Mv 144.000 g/mol) and a deacetylation degree between 89–90%, polyvinyl alcohol (PVA), with hydrolysis between 87–89% and viscous molecular weight of 93,000 g/mol was used (Sigma-Aldrich, Palo Alto, CA, USA). Glacial acetic acid comes from Merck (Burlington, MA, USA). For the elaboration of the simulated biological fluid, NaCl, K₂HPO₄ 3H₂O, CaCl₂, Na₂SO₄, and tris-(hydroxymethyl aminomethane) [(CH₂OH)₃CNH₂] were acquired from Sigma Aldrich (Palo Alto, CA, USA); NaHCO₃, KCl, and MgCl₂ 6H₂O from Fisher Chemical (Pittsburgh, PA, USA); and hydrochloric acid (HCl) from Merck (Burlington, MA, USA). All reagents used were analytical degree.

For pristine (p-)CNO synthesis, carbon nanodiamonds (Sigma-Aldrich, Palo Alto, CA, USA) of 5 nm average diameter were annealed in an oven (Nabertherm LHT 02/18, Lilienthal, Bremen, Germany) at 1600 °C for 2 h in an inert atmosphere of nitrogen; thereafter, amorphous carbon was eliminated by heating at 400 °C in air for 2 h [78 ]. For the synthesis of ox-CNO, concentrated sulfuric acid (H₂SO₄), concentrated nitric acid (HNO₃), and sodium hydroxide (NaOH) supplied by Merck (Burlington, MA, USA) were used. Nanocomposite films were produced using chitosan of low molecular weight (molecular weight (Mw.) 144,000 g/mol, deacetylation degree 89–90%), poly(vinyl alcohol) (PVA) (hydrolysis degree 87–89%, Mw. 93,000 g/mol, Sigma-Aldrich, Palo Alto, CA, USA). Glacial acetic acid from Merck (Burlington, MA, USA) was used for the preparation of CS solutions. Simulated biological fluid (FBS) was prepared using NaCl, K₂HPO₄·3H₂O, CaCl₂, Na₂SO₄, and tris-(hydroxymethyl aminomethane) ((CH₂OH)₃CNH₂) acquired from Sigma Aldrich (Palo Alto, CA, USA), a well as NaHCO₃, KCl, and MgCl₂·6H₂O from Fisher Chemical (Pittsburgh, PA, USA), and hydrochloric acid (HCl) from Merck (Burlington, MA, USA). All reagents were analytical grade.