Sodium phosphate monohydrate

To test the liposomes’ ability to trap free phosphate ions in solution, liposomes were incubated with phosphate solutions at increasing concentrations. To this end, phosphate solutions were prepared by a series of dilutions of sodium phosphate monohydrate (Sigma-Aldrich) dissolved in HEPES-buffered saline (10 mM HEPES, 150 mM NaCl, pH = 7.4) to yield solutions with increasing phosphate concentrations of 0.625, 1.25, 2.5, 5, 10, 20, 40, and 60 mg/dL. A dialysis tube with 1 mL FC liposomes (1.22 mg FC) was placed in 70 mL of each phosphate solution, or in HEPES with no phosphate, for 24 h at 37 °C under constant stirring. Elemental analysis of phosphorus in each solution before and after incubation with the liposomes was performed by ICP-OES. Phosphate binding efficiency was calculated by the following formula: $$\left(\left(\left[P\right] \left(t_0\right) \left(\frac{mg}{dL}\right)\right)-\left(\left[P\right] \left(t_{24}\right)\left(\frac{mg}{dL}\right)\right)\right)·\frac{ {\left[P{O}_4\right]}^{-3}Mw \left(\frac{gr}{mol}\right)}{\left[P\right] Mw \left(\frac{gr}{mo}\right)}={[P{O}_4]}^{-3} binding\left(\frac{mg}{ml FC LP}\right)$$
Equation (1). Calculation of phosphate binding efficiency (P: phosphorus, PO₄⁻³: phosphate, t₂₄: post 24 h of incubation with liposomes, FC LP: FC liposomes).

Oleic acid-capped quantum dots (QDs-OA) with alloyed (CdSe_xS_1-x) core and ZnS shell (CdSeS/ZnS), nanocrystal diameter = 6.0 nm, λ_em = 630 nm, 1 mg/mL in toluene were purchased from Cytodiagnostics Inc. (Burlington, Canada). Glutathione in reduced form (GSH) was from Acros Organics (Geel, Belgium). Tetramethylammonium hydroxide pentahydrate (TMAH) was from Alfa Aesar (Kandel, Germany). Chloroform, anhydrous ethanol, and phosphoric acid (85%) were obtained from Chempur (Piekary Śląskie, Poland). Dialysis tubing cellulose membrane (MWCO = 12 kDa), dopamine hydrochloride, L-epinephrine, L-norepinephrine, serotonin hydrochloride, γ-aminobutyric acid (GABA), acetylcholine chloride, sodium phosphate monohydrate, disodium phosphate dodecahydrate, and sodium hydroxide were supplied by Sigma-Merck (Poznań, Poland). Milli-Q water was used for preparation of all aqueous solutions. All chemicals were used as received.