DiBAC4(3)

DiBAC4(3) is a negatively charged membrane potential-sensitive bis-oxonol dye with excitation maxima at approximately 490nm and its fluorescence emission is collected using a 520nm filter^[1]. DiBAC4(3) is a versatie tool in membrane potential monitoring, viability assays and antibiotic susceptibility testing.

In vitro, DiBAC4(3) was used to measure membrane potentials in HEK293 cells expressing recombinant large conductance Ca²⁺-activated K⁺ (BK) channels (HEKBKα and HEKBKβ ). Cells were incubated in KRH (Krebs-RingerHEPES) buffer containing with 100nM DiBAC4(3) for 20min at room temperature. The oscillatory membrane hyperpolarization induced in HEKBKαβ by was detected only as a slow hyperpolarization with DiBAC4(3)^[2]. B. subtilis cells incubated with membrane-targeting antimicrobials were stained with 10μM DiBAC4(3) for 17h and observed under phase contrast and fluorescence microscopy to evaluate the effects of antimicrobial compounds on membrane integrity and function^[3]. DiBAC4(3) (1μM) was used to assess cell viability and membrane potential in starved cultures of E. coli and Salmonella in seawater. Cells may maintain some membrane potential, they do not necessarily exhibit active respiration, especially in starved conditions^[4].

References:
[1] Epps D E, Wolfe M L, Groppi V. Characterization of the steady-state and dynamic fluorescence properties of the potential-sensitive dye bis-(1,3-dibutylbarbituric acid)trimethine oxonol (Dibac4(3)) in model systems and cells. Chem Phys Lipids. 1994 Feb;69(2):137-50.
[2] Yamada A, Gaja N, Ohya S,et al. Usefulness and limitation of DiBAC4(3), a voltage-sensitive fluorescent dye, for the measurement of membrane potentials regulated by recombinant large conductance Ca₂₊-activated K+ channels in HEK293 cells. Jpn J Pharmacol. 2001 Jul;86(3):342-50.
[3] Winkel J D T, Gray D A, Seistrup K H. Analysis of Antimicrobial-Triggered Membrane Depolarization Using Voltage Sensitive Dyes. Front Cell Dev Biol. 2016 Apr 13:4:29.
[4] Amorós R L, Castel S, Riu J C, Rego J V. Assessment of E. coli and Salmonella viability and starvation by confocal laser microscopy and flow cytometry using rhodamine 123, DiBAC4(3), propidium iodide, and CTC. Cytometry. 1997 Dec 1;29(4):298-305.