Slide a lyzer 2000 mwco

SWNT sensors were encapsulated within alginate as previously described.^{[1 , 9 (link)]} Briefly, d(AT)₁₅–SWNT suspension (10 mg L⁻¹) was added to alginate (Nova-Matrix, PRONOVA SLM 20, 3% w/v) to form a final 2% w/v alginate solution. Alginate-SWNT suspension was crosslinked by BaCl₂ in nanopure water (0.1 m) (BaCl₂ solution) in dialysis tubes (Thermo Scientific, Slide-A-Lyzer 2000 MWCO). Hydrogels were stored in normal saline at 37 °C.

A previously published procedure by Sultzbaugh and Speaker^{[10 (link)]} was altered to tether the SWNT sensors externally to an alginate gel. Alginate was crosslinked for 24 hours with spermine (1% w/v) in HCl solution (0.2 m) (Sigma-Aldrich) using dialysis tubes (Thermo Scientific, Slide-A-Lyzer 2000 MWCO). Hydrogels were placed in an EDC/NHSS/Avidin (Sigma-Aldrich, N-(3-Dimethylaminopropyl)-N’-ethylcarbodiimide, N-Hydroxysuccinimide, Avidin from egg white, 4 μm) bath for 16 hours at 37 °C followed by a 16 hour biotinylated SWNT-d(AT)₁₅ (10 mg L⁻¹) bath at 37 °C. Ratios of 1:0, 2:1, and 1:1 biotin-modified d(AT)₁₅ to d(AT)₁₅ were used for the SWNT bath. Hydrogels were stored in normal saline at 37 °C.