Sodium dodecyl sulfate sds

For the Ti, air-TNTs, and H₂-TNTs binding experiments, we used BSA (Sigma-Aldrich Co., St Louis, MO, USA), histone from calf thymus (Worthington Biochemical Co., Lakewood, NJ, USA), and fibronectin (FN; Sigma-Aldrich Co) as model proteins. A 200-μL aliquot of protein solution (2 mg/mL BSA, histone or FN) was applied to the samples, and they were incubated at 37°C for 30 minutes. After incubation, a 20-μL aliquot of the supernatant was collected to assess the quantities of unbound proteins. The TNTs/Ti substrates were washed three times with 1 mL PBS to remove weakly bound protein and then were transferred into fresh wells. Then, 200-μL 2% sodium dodecyl sulfate (SDS; Beyotime Institute of Biotechnology Co., Beijing, People’s Republic of China) was added to the protein-coated surfaces. Samples were shaken for 2 hours to elute the absorbed protein. The SDS solution with the collected proteins was used for the bound-protein assessment. The concentration of protein was determined with a BCA protein assay kit (Beyotime Institute of Biotechnology Co.). The optical density (OD) at 562 nm was measured with a precision microplate spectrophotometer (SpectraMax Paradigm). Triplicates of three independent samples were measured for each condition.