Az5214e photoresist

Inorganic salts (AppliChem GmbH, Darmstadt, Germany and Sigma-Aldrich, St. Louis, MO, USA) and phosphate-buffered saline (PBS) tablets (Ecoservice, Saint Petersburg, Russia) were used. The DNA oligonucleotides were synthesized by Synthol (Moscow, Russia). The sequences are provided in Table 4.
To clean the substrate surface, extra-pure acetone and isopropyl alcohol (AO Reachem, Moscow, Russia) were used. MIBK (methyl isobutyl ketone, CAS Number: 108-10-1, Sigma-Aldrich, St. Louis, MO, USA) served as a developer for the PMMA electron beam lithography resist.
Four metals for evaporation, Cr, Ag, Au (GIRMET Ltd., Moscow, Russia), and Al (RD Mathis Company, Signal Hill, CA, USA) were used. In lithography processes, AZ5214E photoresist (MicroChemicals, Ulm, Germany) and AZ 726 MIF Developer (Merck, Darmstadt, Germany) were utilized.

Standard photolithography was used to negatively pattern AZ 5214E photoresist (from Micro Chemicals) on the polymeric layer stack. After patterning the photoresist, 10 nm Cr and 50 nm Au were deposited at 0.5 Å s⁻¹ in an e-beam evaporator (Creavac). Finally, a lift-off process was performed in acetone and isopropyl alcohol to remove the photoresist and residue metal layer.

In our experiments, we used the following reagents: extra clean acetone and isopropyl alcohol (AO Reachem, Moscow, Russia); phosphate-buffered saline (PBS) tablets (Ecoservice, Saint Petersburg, Russia); fetal calf serum (FCS); the fetal bovine serum (HyClone, Logan, UT, USA); L-glutamine and penicillin/streptomycin (PanEco, Moscow, Russia); glutaric aldehyde (CAS Number: 111-30-8, AppliChem GmbH, Darmstadt, Germany).
We also used four metals for evaporation, Cr, Ag, Au (GIRMET Ltd., Moscow, Russia), and Al (RD Mathis Company, Signal Hill, CA, USA). In lithography processes, we utilized AZ5214E photoresist (MicroChemicals, Ulm, Germany) and AZ 726 MIF Developer (Merck, Darmstadt, Germany). To optimize the nanoperiodic structure, we analyzed the intensity of the SERS signal from the 4-ABT (4-Aminobenzenethiol, CAS Number: 1193-02-8, Sigma-Aldrich, St. Louis, MO, USA) test molecules.