Cm100

Magnetic NCs were characterized from a morphological point of view (size, shape, and surface morphology) by SEM (Vega Tescan) and TEM. For TEM observation, a droplet of the capsule suspension in acetone was deposited onto a formvar-coated copper grid. The samples were analyzed with a Philips CM100 microscope equipped with an Olympus camera and transferred to a computer equipped with a Megaview system. The mean diameter, size distribution, and zeta-potential were determined in triplicate at 25 °C at a concentration of 1% (w/v). The mean diameters were determined by dynamic light scattering (DLS) (Zeta Nanosizer Malvern) on samples dispersed in anhydrous acetone in order to avoid the swelling of the NCs. A droplet of Span 80 was added in order to avoid aggregation of the NCs. The zeta-potential was determined by electrophoresis in phosphate-buffered solution (PBS; pH = 7.4).

Cells were grown on hanging polyethylene terephthalate filters with pore size 0.4 µm (Cat No PIHT12R48, Milipore, Merck, Germany) and seeded in different densities allowing them to become a confluent monolayer at days 1, 2 and 4. When confluent, cells were washed in 5% bovine serum albumin (BSA, Cat No A8022, Sigma Aldrich) and incubated with 0.5 mg/ml cationized ferritin (Cat No F7879, Sigma Aldrich) in 5% BSA for 30 min at room temperature. Cells were initially washed in 5% BSA then in 0.2 M cacodylate buffer [Cat No 11653, electron microscopy sciences (EMS)]. Cells were fixed ON in 2.5% glutaraldehyde (Cat No 16210, EMS) in 0.05 M cacodylate buffer and dehydrated according to standard methods [23 (link)]. Cells were osmificated at 1% for 60 min. (Cat No AGR1017, Agar Scientific) and infiltrated with an epoxy resin (Cat No T031, Embed 812 Medium, TAAB) by using propylene oxide as an intermediate (Cat No 20401, EMS). Cells were initially cut as semi thin sections at 1 µm and stained with toluidine blue. Then cut for TEM at 50 nm thickness and stained with uranyl acetate and lead citrate (EMS) as previously described [23 (link)]. All TEM was performed by using a Philips CM100 equipped with an Olympus Veleta camera connected to a workstation with SIS Analysis software (iTEM).