Kimwipe absorbent paper

Concentrated EV samples were diluted 1:20 with Milli-Q water. 10 -20 μL of dilute EV samples were drop-cast onto nanohole arrays and subsequently removed using cohesive properties allowed by a Kimwipe absorbent paper (Kimberly-Clark Inc.).
The edge of the absorbent paper was placed on the corner of the solution droplet, allowing for solution removal via capillary action. EV solutions were allowed to dry for 15 -30 minutes prior to SERS measurements. EVs were located in nanoholes by SERS mapping, and spectra were extracted from these maps. SERS spectra were acquired with an XploRA TM PLUS spectrometer (Horiba Scientific) using a 785 nm excitation laser source, 600 grooves/mm grating, 100 × objective (N.A. = 0.9), and 100 μm pinhole. Laser power was set to 5 mW with an acquisition time of 4 seconds per spectrum.

Concentrated EV samples were diluted 1:20 with Milli-Q water. 10 -20 μL of dilute EV samples were drop-cast onto nanohole arrays. EV-water solution was removed from the array using cohesive properties allowed by a Kimwipe absorbent paper (Kimberly-Clark Inc.). The edge of the absorbent paper was placed on the corner of the solution droplet, allowing solution removal via capillary action. This capillary flow also induces EVs to locate and stay in the nanoholes. Lastly, EV solutions were allowed to dry for 15 -30 minutes prior to SERS measurements. SERS spectra presented in Fig. 4 were acquired with a LabRAM HR spectrometer (Horiba Scientific) using a 632.8 nm excitation laser source, 600 grooves/mm grating, 100 × objective (N.A. = 0.9), and 200 μm pinhole. Laser power was set to 2.5 mW with an acquisition time of 60 seconds per spectrum. SERS spectra presented in Fig. 5 and Fig. S2 were extracted from SERS maps that were acquired with an XploRA TM PLUS spectrometer (Horiba Scientific) using a 785 nm excitation laser source, 600 grooves/mm grating, 100 × objective (N.A. = 0.9), and 100 μm pinhole. Laser power was set to 5 mW with an acquisition time of 4 seconds per spectrum.