Nanoparticle tracking analysis
NTA was used to detect particles between about 50 and 1000 nm. Measurements were performed with a NanoSight LM20, equipped with a sample chamber with a 635-nm laser for illumination of the particles. Samples of 10 mg/mL adalimumab were injected into the chamber by an automatic pump (Harvard Apparatus, catalog no. 984362, Holliston, USA) using a sterile 1 ml syringe (BD Discardit II, Franklin Lakes, New Jersey). For each sample a 90 second video was captured with the shutter set at 29.9 ms and the gain at 680. Videos were analyzed using NTA 2.0 Build 127 software. The following settings were used for tracking of the particles: background extract on; brightness 0; gain 1; blur size 3x3; detection threshold 10, viscosity 0.953. All other parameters were set to the automatic adjustment mode.