*2.1. Materials*

Phospholipon 90G (soybean phosphatidylcholine) (P90G) was kindly donated by Lipoid (Steinhausen, Switzerland). Cholesterol and B12 (purity 95%) were purchased from Acofarma (Madrid, Spain). Tween 80, phosphate salts, and sodium chloride to prepare buffers were from Scharlab (Sentmenat, Spain). Regenerated cellulose dialysis membranes with a cut-off of 14kDa (Spectra/Por® molecular porous membrane tubing) for the in vitro release studies were acquired from Repligen (Waltham, MA, USA). HPLC-quality water obtained by Milli-Q purification (Millipore, Madrid, Spain) with resistance > 18 MΩ cm and TOC < 10 ppb was used for liposome reconstitution and HPLC analysis. Methanol for the HPLC mobile phase was purchased at VWR International (Radnor, PA, USA). For the tape-stripping studies, adhesive tape Tesafilm kristall-klar (33 mm × 19 mm, cut to 30 mm × 19 mm sections) was obtained from Tesa (Hamburg, Germany); Parafilm Sealing Film—50 mm (2") Film Width × Roll Length 75 m (Parafilm, Madrid, Spain) was used; glass beads were obtained from MERCK (Madrid, Spain). Pig ears were procured from a local slaughterhouse (Mercavalencia, Valencia, Spain).
