Rapid and sensitive detection of bacteria via platinum-labeled antibodies and on-particle ionization and enrichment prior to MALDI-TOF mass spectrometry Faheem Ahmad and Hui-Fen Wu* *Corresponding author, Phone: ; Fax: Supplementary material

Scheme S1. Schematic Illustration of Synthesis of Pt NPs according to mentioned procedure.

Fig. S1UV-visible spectrum of unmodified Pt NPs (solid line) and supernatant of IgG-Pt NPs solution (dotted line).

Fig. S2TEM image of the unmodified platinum nanoparticles (Pt NPs).

Fig. S3MALDI mass spectra obtained as direct analysis to selectively concentrate S. marcescens from aqueous solutions at concentrations of (a) 2.80 × 10 5, (b) 2.80 ×10 6, and (c) 2.80 ×10 7 cfu/mL.

Fig. S4 MALDI mass spectra obtained as direct analysis to selectively concentrate E. coli from aqueous solutions at concentrations of (a) 2.99 ×10 5, (b) 2.99 ×10 6, and (c) 2.99 ×10 7 cfu/mL.

Fig S5 MALDI mass spectra obtained after using antibody IgG modified platinum nanoparticles to process the mixed bacterial cells suspension of S. marcescens at concentrations of (a) 2.80 × 105, (b) 2.80 ×106, (c) 2.80 ×107cfu/mL, and E. coli at concentrations of (a) 2.99 ×105, (b) 2.99 ×106, (c) 2.99 ×107 cfu/mL.