Kh2po4

Dimethyl sulfoxide (DMSO), 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, EZ-Link™ NHS-PEG4 Biotinylation Kit, and NHS were acquired from Merck KGaA, Darmstadt, Germany. Albumin Fraction V (biotin-free), KCl, KH₂PO₄, NaCl, Na₂(CO₃), NaHCO₃, Na₂HPO₄ × 12 H₂O and Tween-20 were purchased from Carl Roth, Karlsruhe, Germany. Immuno-filtration columns (ABICAP HP columns) were purchased from Senova Gesellschaft für Biowissenschaft und Technik mbH, Weimar, Germany. Anti-Penicillin G monoclonal antibody was kindly provided by the Milchprüfring Bayern e.V. (MPR), Wolnzach, Germany. Anti-kanamycin monoclonal antibody (article number CSB-MA000511I0m) was purchased from Cusabio, Wuhan, China. Detection antibody goat anti-mouse IgG coupled to HRPO (article number 115-035-008) was purchased from Jackson ImmunoResearch Europe Ltd., Ely, UK. Penicillin G and kanamycin A were acquired from Duchefa Biochemie, Haarlem, Netherlands. Magnetic particles with streptavidin-functionalized shell and a hydrodynamic diameter of 70 nm [synomag^®-D, article number 104-19-701] were purchased from micromod Partikeltechnologie GmbH, Rostock, Germany.
Coupling buffer, phosphate buffered saline (PBS), PBS-Tween (PBS-T) as well as blocking solutions for ELISA and magnetic immunodetection were prepared as described in [23 (link)].

Methanol (MeOH), acetonitrile (ACN), and toluene were obtained in gradient grade from Fisher Scientific (Schwerte, Germany). NaCl, formic acid, hexane, and Na₂HCO₃ were in pro analysi (p.a.) quality from Merck KGaA (Darmstadt, Germany). Potato dextrose agar (PDA), potato dextrose broth, and KH₂PO₄ were from Carl Roth (Karlsruhe, Germany), Xylene in p.a. quality was obtained from Honeywell (Seelze, Germany), NaHCO₃ in p.a. quality was obtained from Grüssing (Filsum, Germany), and KCl in p.a. quality was obtained from VWR (Langenfeld, Germany). Purified water of ASTM type 1 quality was prepared with a Purelab Flex 2 system from Veolia Water Technologies (Celle, Germany).

Neisseria gonorrhoeae was grown overnight at 37°C and 5% CO₂ on agar plates containing gonococcal base (GC) agar [10 g/l Bacto agar (BD Biosciences, Bedford, MA, United States), 5 g/l NaCl (Roth, Darmstadt, Germany), 4 g/l K₂HPO₄ (Roth), 1 g/l KH₂PO₄ (Roth), 15 g/l Proteose Peptone No. 3 (BD), 0.5 g/l soluble starch (Sigma-Aldrich, St. Louis, MO, United States)] supplemented with IsoVitaleX (IVX): 1 g/l D-Glucose (Roth), 0.1 g/l L-glutamine (Roth), 0.289 g/l L-cysteine-HCL × H₂0 (Roth), 1 mg/l thiamine pyrophosphate (Sigma-Aldrich), 0.2 mg/l Fe(NO₃)₃ (Sigma-Aldrich), 0.03 mg/l thiamine HCl (Roth), 0.13 mg/l 4-aminobenzoic acid (Sigma-Aldrich), 2.5 mg/l β-nicotinamide adenine dinucleotide (Roth) and 0.1 mg/l vitamin B₁₂ (Sigma-Aldrich). GC medium is identical to the base agar composition but lacks agar and starch.
E. coli was grown in LB (Lysogeny Broth, Roth) medium or on LB agar plates (15 g/l Bacto agar (BD Biosciences, Bedford, MA, United States) at 37°C.
For N. gonorrhoeae antibiotics were used at the following concentrations: 2.5–5 μg/ml erythromycin (Thermo-Fisher), 100 μg/ml streptomycin (Sigma-Aldrich), 10 μg/ml chloramphenicol (Sigma-Aldrich). For E. coli antibiotics were used at the following concentrations: 50 μg/mL kanamycin (Roth).

Culture medium (CM) was prepared using RPMI 1640 supplemented with 100 U/mL of penicillin, 100 μg/mg streptomycin (both from Sigma, Steinheim, Germany), and 2 mM L-glutamine (Biochrom, Berlin, Germany). Concanavalin A (ConA) (Sigma) was diluted in CM to a concentration of 600 μg/mL and stored at −70°C. Antibodies were purchased from Becton Dickinson (BD, Heidelberg, Germany). Phosphate buffered saline (PBS) was made by dissolving 7.013 g NaCl, 0.2 g KCl, 1.513 g Na₂HPO4, and 0.2 g KH₂PO4 (all purchased from Roth) in 1 liter distilled water and by adjusting the pH to 7.4. Red blood cell (RBC) lysing solution was purchased from Becton Dickinson and diluted 1 : 10 in distilled water before use. Washing buffer was obtained from BD Biosciences (San Diego, USA). Formaldehyde solution and absolute methanol was purchased from Merck (Darmstadt, Germany).

Gonococcal base agar was made from 10 g/l dehydrated agar (BD Biosciences, Bedford, MA), 5 g/l NaCl (Roth, Darmstadt, Germany), 4 g/l K₂HPO₄ (Roth), 1 g/l KH₂PO₄ (Roth), 15 g/l Proteose Peptone No. 3 (BD Biosciences), 0.5 g/l soluble starch (Sigma-Aldrich, St. Louis, MO), and supplemented with 1% IsoVitaleX (IVX): 1 g/l D-glucose (Roth), 0.1 g/l L-glutamine (Roth), 0.289 g/l L-cysteine-HCL x H₂O (Roth), 1 mg/l thiamine pyrophosphate (Sigma-Aldrich), 0.2 mg/l Fe(NO₃)₃ (Sigma-Aldrich), 0.03 mg/l thiamine HCl (Roth), 0.13 mg/l 4-aminobenzoic acid (Sigma-Aldrich), 2.5 mg/l β-nicotinamide adenine dinucleotide (Roth), and 0.1 mg/l vitamin B12 (Sigma-Aldrich). GC medium is identical to the base agar composition but lacks agar and starch.

Alpha-amylase, CaCl₂ ∙ 2H₂O, 4′,6′-diamidino-2-phenylindole (DAPI), 2′,7′-dichlorofluorescin-diacetate (DCFH-DA), MgCl₂ ∙ 6H₂O, mucin, ox bile, pancreatin, paraformaldehyde, pepsin, trypsin and ZnO nanopowder (#677450 and #544906) were purchased from Sigma-Aldrich Chemie GmbH, Taufkirchen, Germany. Dulbecco’s Modified Eagle Medium (DMEM), foetal bovine serum (FBS), non-essential amino acids, penicillin/streptomycin, and trypsin/EDTA were obtained from PAN-Biotech GmbH, Aidenbach, Germany. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), dimethyl sulfoxide, fluorescein isothiocyanate (FITC)-dextran, hydrogen peroxide (30%), nitric acid (Suprapur), and triton X-100 were acquired from Merck KGaA, Darmstadt, Germany. 2-((3-Chlorophenyl) hydrazinylidene) propanedinitrile (CCCP) and ZnCl₂ were procured from Thermo Fisher Scientific Inc., Waltham, MA, USA. Carbamide, ethylene glycol tetraacetic acid (EGTA), KCl, KH₂PO₄, NaCl, NaHCO₃, and Na₂HPO₄ ∙ 2H₂O were purchased from Carl Roth GmbH & Co. KG, Karlsruhe, Germany. Cacodylic acid and glutaraldehyde were bought from Serva Electrophoresis GmbH, Heidelberg, Germany. 5,5′,6,6′-Tetrachloro-1,1′,3,3′-tetraethylbenzimidazolylcarbocyanine iodide (JC-1) was obtained from Enzo Life Sciences GmbH, Lörrach, Germany. Phalloidin-iFlour 488 reagent was acquired from Abcam plc., Cambridge, UK.