Individual Au-nanocube based Plasmonic nanoprobe for cancer relevant microrna biomarker detection

Transcription

1 Supporting Information Individual Au-nanocube based Plasmonic nanoprobe for cancer relevant microrna biomarker detection Lei Zhang, Jinghui Wang, Junxia Zhang, Yuqi Liu, Lingzhi Wu,,* Jingjing Shen, Ying Zhang, Yanling Hu, Quli Fan, Wei Huang,, and Lianhui Wang,* Key Laboratory for Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), National Synergistic Innovation Center for Advanced Materials (SICAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing , China. Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), National Synergistic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (Nanjing Tech), 30 South Puzhu Road, Nanjing , China. College of geographic and biologic information, Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing , China.

2 Experimental materials and apparatus. Hexadecyltrimethylammonium bromide (CTAB) and ascorbic acid were purchased from Sigma Company (China). HAuCl4 3H2O and NaBH4 were purchased from Aladdin Company (China). All reagents were used without any further purification. Ultrapure water was obtained from a Milli-Q water purification system (Millipore Corp., Bedford, MA) with resistivity of 18.2 MΩ cm and used for all procedures. HPLC-purified DNA and mirnas were purchased from Takara Biotechnology Co. Ltd. (Dalian, China) and used without any purification. The sequences of these oligonucleotides are shown as follows, probe ssdna: 5 - CA GAC TCC GGT GGA ATG AAG GAT TTT TTT TTT-SH-3 ; random DNA: 5 -GCT ATG TAA CTA TGC TAG GCA C-3 ; mir-205: 5 -UCC UUC AUU CCA CCG GAG UCU G-3 ; single base mismatch mirna: 5 -UCC UUC AUU CCG CCG GAG UCU G-3 ; The underlined base is the mismatched base. The UV-Vis absorption experiments were captured by a Shimadzu UV3600 spectrophotometer. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images were captured by S-4800 instrument (Japan) and JEM 2010 instrument (Japan) respectively. All the measurements were performed at room temperature of 25 C. The details of preparation of gold nanocubes, substrate preparation, modification of single strand DNA probes on AuNCs, real-time monitoring and detection of DNA-RNA hybridization and SPRS instrumental asset could be found in the supporting information section. Experimental methods

3 Preparation of gold nanocubes. The gold nanocubes (AuNCs) of edge length ~50 nm were prepared following a seed-mediated growth approach in aqueous solution referred to the Au nanostructures synthesis experiments of Sau and Murphy. 28 Generally, the synthesis involves two steps including a seeding process and a growth process Specifically, the seeds were prepared by the rapid injecting of freshly prepared, ice-cold NaBH4 solution (0.3 ml, 0.01 M) into a mixture solution composed of HAuCl4 (0.125 ml, 0.01 M) and CTAB(3.75 ml, 0.1 M), followed by the rapid inversion mixing for 2 min. This seed solution was kept at 25 C for 2 h before use. The growth solution was made by the sequential addition of ultrapure water (8 ml), CTAB (1.6 ml, 0.1 M), HAuCl4 (0.2 ml, 0.01M), and ascorbic acid (0.95 ml, 0.1 M). Next, 0.01mL of the CTAB-stabilized seed solution diluted 25 times with water were then added into the growth solution. The resultant solution was mixed and allowed to sit at 25 C overnight. AuNCs aqueous solution was purified by centrifugation at 4000 rpm for 15 min twice, and redispersed in a suitable amount of ultrapure water. The final AuNCs aqueous solution was in the color of pink-red and the specific morphology was characterized by TEM and SEM measurements, respectively. Substrate preparation. Indium tin oxide (ITO) glass slides as substrate were prepared by cleaning with detergent, acetone, ethanol and water orderly in an ultrasonic water bath for 1 h, respectively, then washed with ultrapure water and dried with a stream of nitrogen. Next, the cleaned ITO glasses were immersed in a 5 times diluted AuNCs aqueous

4 solution for 20 seconds. The AuNCs can be absorbed on the surface of the ITO slide physically. After the absorption, we should wash the slide with water and dried with nitrogen. The immobilized AuNCs on the ITO chip without spraying gold film can be observed directly by SEM due to its good electro-conductibility. Modification of single strand DNA probes on AuNCs. DNA probes were designed to be modified with a thiol group at 3 ends for the better combination with AuNCs. 200 µl of 1 µm ssdna solution was pipetted onto the surface of the AuNCs modified ITO glass slide and incubated in the shaker with 30 rpm at room temperature for 2 hours. DNA-RNA hybridization and SPRS instrumental asset. Single AuNC SPRS spectra were taken by the dark-field measurement carried out on an inverted microscope (eclipse Ti-U, Nikon, Japan) equipped with a dark-field condenser (0.8 < NA < 0.95), a 60X objective lens, a 100 W halogen lamp to excite the AuNCs and generate plasmon resonance scattering light, a true-color digital camera (Nikon DS-fi2) to capture the true color scattering images of AuNCs, and a monochromator (Acton SP2300i) equipped with a spectrograph CCD (PIXIS 400BR: excelon, Princeton Instruments) to obtain the scattering spectra and a grating (grating density: 300 L/mm; blazed wavelength: 500 nm). The true color images of AuNCs were taken using a 60X objective lens. For the SPRS signal taken procedure, firstly, the functionalized slide was put on the automatic stage, and then 100 µl of target oligonucleotide solution were pipetted on the surface of the slide. The scattering spectra of the individual nanocubes were continually collected for 30 seconds and

5 corrected by subtracting the background spectra and then divided with the calibrated response curve of the entire optical system. Figure S1. UV-vis spectra of AuNCs plasmonic probe with presents of different concentration of mir-205 (a: 0 pm, b: 10 pm, c: 100 pm, d: 10 nm, e: 1 µm).

6 Figure S2. Calibration curve corresponding to the peak shift of the UV-vis spectra with presents of different concentrations of mir-205.

7 Figure S3. The original LSPR scattering spectra of individual Au-nanocube before and after microrna (1 μm) sensing detection.