Hydrochloric acid (hcl)

Methanol (HPLC grade) was purchased from Fischer Chemical (Loughborough, United Kingdom). Water was obtained from a Milli-Q water purification system from Millipore (Bedford, MA, USA). Hydrochloric acid and sodium hydroxide (both analytical grade) employed for the adjustment of pH were obtained from Panreac (Barcelona, Spain). The reagents necessary for the determination of total phenolic compounds were anhydrous sodium carbonate (Panreac, Barcelona, Spain), and Folin–Ciocalteu reagent (Merck Millipore, Darmstadt, Germany). The phenolic standard (gallic acid) and the anthocyanin standard (cyanidin chloride) were purchased from Sigma-Aldrich Chemical Co. (St. Louis, MO, USA).

Chitosan, dopamine (≥98%), ascorbic acid (≥99%) and uric acid (≥99%) were purchased from Sigma-Aldrich (www.sigmaaldrich.com). Potassium ferrocyanide (≥98%) and potassium ferricyanide (≥99%) were obtained from BDH Chemicals Ltd. (www.bdhme.com). Potassium chloride (≥99%), hydrochloric acid (37%) and ammonia (30%) were purchased from Panreac (www.panreac.com). Sulphuric acid (≥36%) was purchased from Tedia Inc. (www.tedia.com). Acetic acid glacial (≥99.5%) was obtained from ADWIC (www.nasrpharma.com). d-Glucose anhydrous was purchased from Techno Pharmchem (www.technopharmchem.com).
All solutions were prepared with ultrapure water (18.2 MΩ cm) from a Milli-Q water purification system, Millipore (www.merckmillipore.com).
A screen printed three-electrode system (SPCE) from Orion High Technologies (www.orion-hitech.com) comprising a nanostructured carbon working electrode (ϕ = 4 mm), a Ag|AgCl reference electrode and a carbon counter electrode was employed in all electrochemical measurements.

All reagents were of analytical grade (PA) and used as received, except for chitosan, which was purified as described in the next section. All solutions were prepared using ultrapure H₂O obtained from a D13321 Barnsted^TM EASYpure Rodi^® system (Thermo Scientific, Dubuque, IA, USA), conductivity 18.2 Ω cm⁻¹, after pre-treatment in an OS 10LZ reverse osmosis system (Gehaka, São Paulo, Brazil).
Reagents used included glacial acetic acid and disodium hydrogen phosphate (J.T. Baker, Xalostoc, Edo. de México, Mexico); hydrochloric acid (Panreac, Castellar del Vallès, Spain); ammonium hydroxide (Exodo, Sumaré, Brazil); sodium hydroxide and potassium dihydrogen phosphate (Spectrum, New Brunswick, NJ, USA); absolute ethyl alcohol (Synth, Diadema, Brazil); acetonitrile, phosphoric acid (Mallinokrodt, Staines-upon-Thames, UK); naproxen 99.5% (Pharmanostra, Campinas, Brazil); deuterium oxide, epichlorohydrin ≥ 99.0% and chitosan low molar mass ( $\overline{M}\mathrm{v}$ = (4.3 ± 0.4) 10⁴ Da and degree of deacetylation ( $\overline{DD}$ ) of 89.9%) (Sigma Aldrich, St Louis, MO, USA).

Sodium carbonate, sodium acetate, potassium persulphate, 2,4,6-tris(2-pyridyl)-s-triazine (TPTZ) and phosphate-buffered saline (PBS) were purchased from Sigma-Aldrich (Madrid, Spain). Hydrochloric acid, ethanol, glycine, Folin reagent, and iron trichloride (FeCl₃·6H₂O) were obtained from Panreac (Barcelona, Spain). ABTS (2,2-azino-bis-(3 ethylbenzothiazolne-6-sulfonic acid) diammonium salt) and Trolox (6-hydroxy-2,5,7,8-tetramethyl-chroman-2-carboxylic acid) were purchased from Fluka (Madrid, Spain).

Three NeuroPs (4(RS)-4F_4t-NeuroP, 4-epi-4-F_3t-NeuroP, 4-F_4t-NeuroP) and three F_2t-dihomo-IsoPss (17-epi-17-F_2t-dihomo-IsoP, 17-F_2t-dihomo-IsoP, Ent-7(RS)-7F_2t-dihomo-IsoP) were synthesized by Durand’s team at the Institut des Biomolecules Max Mosseron (IBMM) (Montpellier, France). Table 1 shows the different NeuroPs and F_2t-dihomo-IsPs molecules tested in this study.
The enzyme β-glucuronidase, type H2 from Helix pomatia and BIS-TRIS (bis-(2hydroxyethyl)-amino-tris(hydroxymethyl)-tris(hydroxymethyl)-methane) were obtained from Sigma-Aldrich (St Louis, MO, USA). All LC-MS-grade solvents were obtained from J.T. Baker (Phillipsburg, NJ, USA). Hydrochloric acid, hexane, trichloroacetic acid, and ethyl acetate were obtained from Panreac (Caste3llar del Vallés, Barcelona, Spain). Strata X-AW solid-phase extraction (SPE) cartridges, 100 mg per 3 mL, were purchased from Phenomenex (Torrance, CA, USA). Water was treated in a Milli-Q water purification system from Millipore (Bedford, MA, USA).

Hydrochloric acid (HCl, 37%) was purchased from Panreac. Hydrogen tetrachloroaurate trihydrate (HAuCl₄・3H₂O, ≥99.9%), sodium citrate tribasic dihydrate (≥98%), silver nitrate (AgNO3, ≥99%), L-ascorbic acid (AA, ≥99%) were purchased from Sigma-Aldrich and O-[2-(3- mercaptopropionylamino)ethyl]-O'methylpolyethylene glycol (PEG-SH, Mw 5,000 g/mol) was purchased from RAPpolymere. Amino functionalized polystyrene beads (NP size 483 ± 3 nm) were purchased from IKERLAT Polymers (Lasarte, Spain). All glassware was washed with aqua regia, rinsed 3-fold with milli-Q water and dried before use. Milli-Q water (resistivity 18.2 MΩ·cm at 25 °C) was used in all experiments.
For the synthesis of lanthanide-doped CaF₂ the starting reagents were calcium chloride (≥ 99%, Sigma-Aldrich) and ammonium fluoride (98+%, Acros) as CaF₂ precursors, neodymium chloride (99.9%, Alpha Aesar) and yttrium chloride (99.99%, Alpha Aesar) as lanthanide sources, and sodium citrate tribasic dihydrate (Sigma-Aldrich) as a surfactant. All chemicals were used without further purification, and all experiments were carried out using nanopure water.