Bdpy2. Two molecular probes, one Bdpy1 (Figure ) and one Bdpy2 (Figure ) were selected and synthesized as conjugable GSH probes. Bdpy1 incorporates a) chlorine substituents for irreversible reaction with GSH and b) a propargyloxy moiety at the para position of the meso phenyl substituent for conjugation to the surface of SOµCs. Bdpy2, instead, incorporates diethyl malonate electron-withdrawing groups, connected via exocyclic double bonds, which provides a specific Michael addition reversible reaction between the vinyl group and GSH. The synthesis of Bdpy1 will be reported elsewhere. As for Bdpy2, it was synthesized as a four-step sequence (Scheme S1) starting with the condensation of diethyl 2-((1H-pyrrol-2-yl)methylene)malonate (1) and 4-(prop-2-yn-1-yloxy)benzaldehyde (2) to give dipyrromethane (3) followed by oxidation to yield dipyrromethene (4) as shown in the Supporting Information (Scheme S1). Then, reaction of (4) with boron trifluoride afforded Bdpy2. The synthesized compounds were characterized by 1 H NMR and C NMR spectroscopies, electrospray ionization mass spectrometry (ESI MS), and Fourier transform infrared (FT-IR) (Figures to S1-12 in Supporting Information). Before immobilization of GSH probes on the surface of microchips, their optical properties in solution were investigated using UV-Vis absorption and fluorescence spectroscopies experiments both in the absence and presence of GSH. As it can be seen in Figure , the maximum absorbance (Figure ) and emission (Figure ) of Bdpy1 are at λex = 508 nm and λem = 525 nm, respectively. In the presence of GSH (1 mM), the new absorbance peak at λex = 572 nm (λem = 585 nm) appears correspond to the creation of a new chromophore as the consequence of the reaction of the thiol group in GSH and Bdpy1 (Figure ). In the case of the reversible probe of Bdpy2, its absorption peak exhibits at λex = 590 nm and the emission is at λem = 608 nm. This red-shift of Bdpy2 compared with Bdpy1 is attributed to the electron-withdrawing diethyl malonate groups, connected via exocyclic double bonds at the 3,5-positions, which extend the delocalization of the pi-system, causing a shift towards longer wavelengths in the absorption band.