## 2 Materials and Methods
### Analytical Set-Up for the Detection of Released Nanomaterials in the Abrasion  
* Silver nanocomposites  
Silver is an element that can be measured at very low detection limits by inductively-coupled plasma mass spectrometry (ICP-MS). For the detection of silver in samples taken from the abrasion test the instrument was calibrated using Merck VI ICP Multielement standard solution (Merck KGaA, Darmstadt, Germany). From this stock solution a serial dilution with 0.0 (3% nitric acid blank),0.5, 1.0, 1.5, 2.0, 2.5, 5.0, 10.0, and 25.0 ng/mL silver in 3% nitric acid was prepared. The standard with the lowest concentration of silver (0.5 ng/mL) could still be distinguished from the blank and standards with higher silver concentrations. Thus, 0.5 ng/mL was set as the limit of detection of the device for silver. Quartz sand was used as an abrasive substance for silver nanocomposites because no interferences between solubilized silver particles and other ions can be expected. Stability tests were performed to evaluate whether loss of sample might adhere due to adsorption of silver on the surface of the sand particles. For this 1.0 g quartz sand was given to 20 mL of 10.0 ng/mL silver in 3% nitric acid solution and shaken for 5 min. The supernatant was analyzed by ICP-MS and compared to a 10.0 ng/mL silver standard without sand. With a stability rate of 102.7% silver could be fully recovered. * TiN nanocomposites  
Proof of TiN NPs in the abrasion was intended to be performed by ICP-MS measurements of Ti. For this the ICP-MS was calibrated externally using a Ti standard solution (Merck KGaA, Darmstadt, Germany, Matrix: 3% nitric acid (HNO\({}_{3}\))). From this stock solution a serial dilution with 0.0 (3% nitric acid blank), 1.0, 5.0, 10.0, 15.0, and 20.0 ng/mL titanium in 3% nitric acid was prepared and used for calibration of the ICP-MS. The standard with the lowest concentration of titanium (1.0 ng/mL) could still be distinguished from the blank and standards with higher titanium concentrations. Thus, 1.0 ng/mL was set as the limit of detection of the device for titanium. NaCl was tested on its suitability as a dry abrasive simulant in the abrasion test. For this, NaCl was tested on impacts of the Ti recovery rate. The Ti standards (5 ng/mL) in a NaCl/HNO\({}_{3}\) matrix (1.0 g NaCl per 20 mL HNO\({}_{3}\) (3%)) were compared to a 5 ng/mL Ti standard in 3% HNO\({}_{3}\) matrix without NaCl. It turned out that 79.6% (average value from samples prepared in triplicate) of Ti could be recovered. * Laponite nanocomposites  
In a previous study [3] it was demonstrated that AF4/MALLS was suitable for the characterization and quantification of laponite particles dispersed in an aqueous surfactant solution (2000 mg/L NovaChem). However, AF4/MALLS showed limitations caused by superimpositions in the fractogram when the sample matrix became too complex. With the empiric formula Na\({}_{0.7}\)[(Si\({}_{8}\)Mg\({}_{5.5}\)Li\({}_{0.3}\))O\({}_{20}\)(OH)\({}_{4}\)]\({}^{-0.7}\) laponite is mainly composed of ubiquitous elements that do not allow sensitive detection via element-specific ICP-MS measurements, due to an already high background of laponite relevant elements. However, a combination of both techniques (i.e., AF4 with MALLS and ICP-MS as detection system) would allow simultaneous screening for particulate structures with an elemental composition typical for laponite. For calibration of the AF4/MALLS system laponite reference dispersions in NovaChem surfactant solution at concentrations 0.0 (NovaChem blank), 250, 500, 1000, 2000, and 2500 ng/mL were prepared. The standard with the lowest concentration of laponite (250.0 ng/mL) could still be distinguished from the blank and standards with higher laponite concentrations. Thus, 250.0 ng/mL was set as the limit of detection of the device for laponite. To determine a suitable dry food simulant test with quartz sand and NaCl in the surfactant solution were performed.