Aunps

A solution of 33 iM TiBP-AuBP in phosphate buffered saline was pipetted onto a titanium disc and incubated at room temperature for 1 h. Discs were washed once with DI H₂O, then dried at room temperature. A solution of 50-nm gold nanoparticles (AuNPs; Ted Pella Inc, USA) was incubated at room temperature on the peptide-functionalized disc for 20 min. The discs were washed once with DI H₂O and dried at room temperature. Next, a solution of 8 μM green fluorescent protein-gold binding peptide fusion (GFP_uv-AuBP) was incubated on the surface for 20 min, washed, dried, and imaged using a fluorescence microscope (Zeiss AxioPlus). The same procedure was applied for four repetitions of fouling/cleansing. All images were analyzed using ImageJ software (version 1.52a).

All materials were purchased from Sigma Aldrich unless otherwise noted. AuNS were synthesized by reducing HAuCl₄ with HEPES buffer (Atlanta Biologicals, pH 7.3. To prepare a 20-mL batch of AuNS, HAuCl₄ was added to the HEPES buffer, with the final concentration being 100 mM HEPES and 0.2 mM HAuCl₄, and the solution was immediately vortexed for 1 minute. To identify the same particles under optical microscopy and EM, an alpha-numeric reference grid (Ted Pella, Inc.) was patterned on a clean No. 1.5 coverslip (Figure S12). The coverslips were then coated with poly-L-lysine (PLL, 0.01%) to create a positively charged surface. Spherical Au NPs (80-nm, Ted Pella, Inc., 1 pM) – used as additional location markers – and AuNS (1 pM) were drop-cast on the glass.

AuNPs (80 × 10⁻⁹ M, 5 ± 0.75 nm, in aqueous solution) came from Ted Pella, Inc. DPPTE (> 99 %), PDP PE (> 99 %) and DPPC (> 99 %) were purchased from Avanti Polar Lipids. Apo AI came from MyBioSource. HCl (> 95 %), NaNO₂ (99.999 %), pentatonic acid (DPTA) (> 99 %), glutathione (> 98 %), 5,5’-Dithiobis(2-nitrobenzoic acid) (DNTB, > 98 %), and pure ethanol were from Sigma Aldrich. DAF FM was obtained from Thermo Fisher Scientific.

AuNPs (Ted Pella) 10 nm in diameter were functionalized with thiolated DNA oligonucleotides via salt-aging. First, 62 nmol DNA was incubated in 100 mM dithiothereitol (DTT, pH 8) for 1 h to reduce the disulfides and purified using Nap-5 exclusion columns (Cytivia). The purified DNA was added to 10 mL 7.7 nM 10-nm AuNP suspension and incubated with shaking for 30 min at room temperature. Then, 0.05% Tween-20 was added to the solution, which was then vortexed thoroughly. The salt concentration was gradually increased to 0.5 M by adding NaCl, sonicating, and vortexing every 15 min while shaking, followed by an overnight incubation. Unattached oligonucleotides were removed by washing with 1% Tween-20 2 times, then 1X DPBS 3 times in Amicon Ultra 50K molecular weight cutoff spin filters (MilliporeSigma). SNAs were stored at 4 °C for up to 3 months.