PMC:4996384 / 7317-9401
Annnotations
{"target":"https://pubannotation.org/docs/sourcedb/PMC/sourceid/4996384","sourcedb":"PMC","sourceid":"4996384","source_url":"https://www.ncbi.nlm.nih.gov/pmc/4996384","text":"2.3. AuNPs-ssDNA Conjugation\nGold nanoparticles modified by ss-DNA were prepared according to the literature with some modifications [29]. In a typical experiment, to 1mL of citrate coated AuNPs solution (1.16 nM), 3 mg of BSPP was added, and the mixture was stirred at room temperature in order to allow phosphine ligands to replace the citrate ligands. Following overnight incubation, 2 mg of NaCl were added to the stirring mixture until the color change from red to cloudy purple. The solution was centrifuged at room temperature for 10 min at 16750 G to collect the precipitated AuNPs. The supernatant was removed and the pellet re-suspended in BSPP buffer (1 mg/mL of BSPP). Nanoparticle purification and concentration steps were carried out in a Sigma Laborzentrifugen 3K15 centrifuge.\nTo functionalize AuNPs with ssDNA conjugates, 10 µL of 5'-thiolated DNA at 10 µM (PBS, pH 7.4) was mixed with 70 µL of the concentrated gold colloid prepared in the first step, 10 µL of PBS (pH 7.4) and 10 µL of BSPP buffer (1 mg/20 µL of BSPP). The mixture was incubated under gentle agitation at room temperature for 24 h, then 7 µL of PEG solution at 150 µM (PBS, pH 7.4) was added and the solution was incubated with gentle agitation for a further 2 h. The solution was then centrifuged (10 min, 16750 G) to remove the excess of reagents. The supernatant was discarded and the precipitate was washed with the SPR running buffer. After a second centrifugation, the final precipitate was re‑suspended in 1 mL of SPR running buffer. UV-visible absorption spectroscopy was used for optical characterization of the AuNPs-ssDNA conjugates. The measurements were taken using a ND-1000 Nanodrop (Labtech International, Uckfield, UK) spectrometer. AuNPs and AuNPs-ssDNA conjugates were quantified by measuring the absorbance at λ = 520 nm and calculating the concentration using Beer’s law based on their extinction coefficients: ε520 (20 nm) = 8.8 × 108 M−1·cm−1. The maximum UV–Vis absorption peak of unmodified AuNPs and AuNPs-ssDNA conjugates in solution were 520 nm and 528 nm, respectively.","divisions":[{"label":"Title","span":{"begin":0,"end":28}}],"tracks":[{"project":"2_test","denotations":[{"id":"27600212-18331002-69481641","span":{"begin":134,"end":136},"obj":"18331002"}],"attributes":[{"subj":"27600212-18331002-69481641","pred":"source","obj":"2_test"}]}],"config":{"attribute types":[{"pred":"source","value type":"selection","values":[{"id":"2_test","color":"#93ecc1","default":true}]}]}}