Graphite power and sodium borohydride of analytical grade were from Sinopharm Chemical Reagent Co. Ltd. (China). 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC), tris(2-carboxyethyl)phosphine hydrochloride (TCEP), and theophylline et al. were purchased from Sigma-Aldrich, Inc. (U.S.A.). Thioglycolic acid (TGA) and cadmium chloride hemipentahydrate (CdCl2·2.5H2O) were from Alfa Aesar China Ltd. Ultrapure water obtained from a Millipore water purification system (≥18 MΩ, Milli-Q, Millipore, Billerica, MA) was used in all runs. All other reagents were of analytical grade.
The theophylline aptamers (Shanghai Sangon, China) used in this study have the following sequences: 5′-HS-(CH2)6-CCU UGG AAG CC-3′ (RNA1), 5′-GG AUA CCA-(CH2)6-SH-3′ (RNA2). RNA hybridization buffer was Tris–HCl (100 mM NaCl, 2.5 mM Mg2+, pH 7.4). RNA was stored in Tris–HCl buffer (TB) (10 mM, pH 8.2). TB (50 mM, pH 7.4) was used for modification of QDs with RNA.
The theophylline aptamers (Shanghai Sangon, China) used in this study have the following sequences: 5′-HS-(CH2)6-CCU UGG AAG CC-3′ (RNA1), 5′-GG AUA CCA-(CH2)6-SH-3′ (RNA2). RNA hybridization buffer was Tris–HCl (100 mM NaCl, 2.5 mM Mg2+, pH 7.4). RNA was stored in Tris–HCl buffer (TB) (10 mM, pH 8.2). TB (50 mM, pH 7.4) was used for modification of QDs with RNA.