Metoprolol met

[Arg8]-vasopressin acetate salt (AVP) (Catalog number V9879) and metoprolol (Met) (Catalog number M1830000) were purchased from Sigma Aldrich (St. Louis, MO, USA). High-glucose DMEM (Catalog number SH30243.01), phosphate-buffered saline (PBS) (Catalog number SH30256.01) and trypsin (Catalog number SH30042.01) were purchased from GE Healthcare (Logan, UT, USA), and fetal bovine serum (FBS) (Catalog number 10270106) and Fluo-3/AM (Catalog number F1241) were obtained from Thermo Fisher Scientific (Waltham, MA, USA). Culture dishes (Catalog numbers 430166 and 430167) were purchased from Corning Costar Company (Cambridge, MA, USA). Confocal Petri dishes (Catalog number 801002) were obtained from NEST (Wuxi, Jiangsu, China).

All chemical compounds employed in this paper were of analytical grade. Silver nitrate ( ${\mathrm{AgNO}}_3$ ) and trisodium citrate were purchased from Roth (Karlsruhe, Germany) and Merck (Darmstadt, Germany), respectively. The aqueous solutions were prepared in Milli-Q water (Milli-Q® Direct Water Purification System, Darmstadt, Germany). ${\mathrm{MgF}}_2$ polished glasses (Crystran Ltd., Poole, UK), having a diameter of 20 mm, were used as port probes for the creation of the solid SERS substrates. The analytes and the pharmaceutical compounds used for SERS measurements (methylene blue MB, doxorubicin DOX, atenolol ATE, metoprolol MET, cysteine Cys and methionine Met) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Cell culture products: Roswell Park Memorial Institute (RPMI 1640) cell culture medium, Fetal Bovine Serum (FBS), Glutamine, Penicillin/Streptomycin and Phosphate Buffered Saline solution (PBS 1X) were purchased from Gibco (Grand Island, NY, USA).