Polydimethylsiloxane permeability-based method for the continuous and specific detection of hydrogen sulfide

Area of Science:

• Biochemistry
• Analytical Chemistry
• Physiology

Background:

• Hydrogen sulfide (H2S) is a vital signaling molecule involved in numerous physiological processes, including vasodilation, vascular tone, neurotransmission, and immune responses.
• The diverse physiological functions of H2S necessitate the development of accurate and reliable detection methods.

Purpose of the Study:

• To introduce a novel, simple, and continuous method for detecting hydrogen sulfide (H2S).
• To exploit the selective permeability of polydimethylsiloxane (PDMS) for H2S detection, minimizing interference from other thiols.
• To quantify kinetic parameters (Km and Vmax) for cystathionine γ-lyase (CSE) and investigate H2S interactions with nitric oxide (NO).

Main Methods:

• Utilized 96-well inserts made of PDMS as a selective membrane for H2S permeation.
• Employed a thiol-specific probe (Ellman's reagent) to detect H2S after it crossed the PDMS membrane.
• Assessed the kinetic parameters of cystathionine γ-lyase (CSE) for its natural substrates, cysteine and homocysteine.
• Investigated the interaction between H2S and NO under normoxic and anoxic conditions.

Main Results:

• Achieved a sensitive H2S detection limit of 9.2 ± 1.9 ppb(m) (~0.51 μM).
• Determined the Michaelis constant (Km) and maximum velocity (Vmax) for CSE with cysteine (Km: 3.79 ± 2.07 mM, Vmax: 0.37 ± 0.02 nmol H2S/min) and homocysteine (Km: 6.90 ± 1.78 mM, Vmax: 1.10 ± 0.19 nmol H2S/min).
• Observed a decrease in H2S levels in the presence of NO under normoxia, suggesting reaction with N2O3 rather than NO directly.

Conclusions:

• The developed PDMS-based method offers a selective and sensitive approach for continuous H2S detection.
• The assay enables accurate determination of enzyme kinetics for H2S-producing enzymes like CSE.
• The findings provide insights into the interaction of H2S with NO, indicating a reaction with N2O3 under specific conditions.