Serum albumin

The device (Cochlear Ltd., Sydney, Australia) consisted of six platinum contacts, 0.3 mm each, with 0.4 mm spacing (Figure 2). Beginning on the electrode tip, only the first and fourth contacts were linked to the connector via parylene-insulated platinum–iridium wires. The wires were embedded in a silicone matrix of about 450 µm outer diameter. The silicone matrix included a drug delivery channel (diameter: ~200 µm) with a single opening at the electrode tip. Wires and the drug channel separated in a distance of 22 mm from the tip (Figure 2A). During surgery, the silicone tube for drug delivery was connected to the flow moderator of a mini-osmotic pump with an infusion rate of 0.5 µL/h, suitable for 14 days delivery (Alzet model 2002; Durect Corp., Cupertino, CA, USA). The day before surgery, the pumps were either filled with AP with addition of 0.1% guinea pig serum albumin (Sigma-Aldrich, Steinheim, Germany) [19 (link)] or 50 ng BDNF (R&D Systems, Wiesbaden, Germany) diluted in 1 mL of serum albumin containing AP and primed in saline at 37 °C overnight.