Sodium dihydrogen phosphate

DL-α-Lipoic acid (LA) (>99.0%) (CAS 1077-28-7) was purchased from Tokyo Chemical Industry Co., LTD (Tokyo, Japan). (±) α-Lipoamide (LPA) (96%) (CAS 940-69-2) was purchased from Toronto Research Chemicals (Toronto, ON, Canada). Tetraethoxysilane (TEOS) (ECOS, high purity grade, Moscow, Russia), ethanol (EtOH) (95%, Chimmed, analytical grade, Moscow, Russia), (3-mercaptopropyl)trimethoxysilan (MPTMOS) (95%) (CAS 4420-74-0), (Aldrich, St. Louis, MO, USA), (3-aminoporopyl)triethoxysilane (APTEOS) (99%) (CAS 919-30-2) (Aldrich, Kenilworth, NJ, USA), methyltrimetoxysilane (MTMOS) (98%+)(CAS 1185-55-3) (Acros Organics, New Jersey, NJ, USA), and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) (CAS 1898-66-4) (Tokyo Chemical Industry Co., LTD, Tokyo, Japan) were used without further purification. Sodium dihydrogen phosphate (NaH₂PO₄·2H₂O) and disodium hydrogen phosphate (Na₂HPO₄·12 H₂O) (Chimmed, analytical grade, Moscow, Russia) were used to prepare buffer solutions with pH 6.0, 6.5, 6.8, and 7.4. Citric acid (Chimmed, analytical grade, Moscow, Russia), sodium hydroxide (Chimmed, analytical grade, Moscow, Russia), and hydrochloric acid (Acros, for analysis, 37%, Geel, Belgium) (CAS 7647-01-0) were used to prepare buffer solution with pH 1.6. The buffer solutions were prepared using doubly distilled deionized water.

Hyaluronic acid sodium salt (HA)(MW 50–100kDa and 1.0–1.5 MDa) was purchased from Glentham Life Science Ltd. (Corsham, UK). Tetraethoxysilane (TEOS) (high purity grade, ECOS, Moscow, Russia) was used as a silica precursor. Hydrochloric acid (HCl) (for analysis, 37%, Acros Organics, Geel, Belgium, CAS 7647-01-0) was used as a catalyst for silica sol formation. Acetic acid (99.7%+, Acros Organics, CAS 64-19-7) and sodium hydroxide (NaOH) (analytical grade, Chimmed, Moscow, Russia) were used to prepare buffer solutions. Sodium dihydrogen phosphate (NaH₂PO₄·2H₂O) and disodium hydrogen phosphate (Na₂HPO₄·12 H₂O) (analytical grade, Chimmed, Moscow, Russia) were used to prepare a buffer solution with pH 7.4. Hyaluronidase (205.5U/mg) was isolated from the testes of cattle (Microgen, Russia). Stains-all (97%, Acros Organics, CAS 7423-31-6, NJ, USA) was used for determination of the amount of released HA. Potassium bromide (KBr), 99+%, IR grade, Acros Organics, Geel, Belgium) was dried at 250 °C before use.