Lab‐on‐a‐chip for hydrogen sulphide detection—Part I: Sulphide separation from plasma sample

Hydrogen sulphide (H 2 S) has emerged as an important signalling molecules due to its unique physiological and pathophysiological role in biological systems. H 2 S can be used as a biomarker for various diseases such as inflammation, cancer, cardiovascular, neurological and gastrointestinal disease. In this work, we report H 2 S chip which is designed for separation of all pools of H 2 S from plasma samples. The chip has been designed, fabricated and characterized. It operates with liberation, separation and trapping of H 2 S from plasma introduced to the chip. It consists of three distinct layers of polydimethylsiloxane (PDMS) structures which were bonded using 3M™ Transfer Tape. The releasing layer provides reaction surface for the liberation of H 2 S from the plasma sample. Releasing buffers allow release of various pools of H 2 S, including free, acid‐labile and total sulphide. A silicone membrane is sandwiched between releasing and trapping layer. It worked as a H 2 S selective membrane where gas diffusion takes place from the releasing layer to the trapping layer. The trapping layer is H 2 S collection chamber. The full‐chip performance was successfully characterized by derivatization of sulphide with excess MBB and analysing fluorescent product, sulphide dibimane (SDB) using the reverse‐phase high‐performance liquid chromatography (RP‐HPLC) and fluorescence detection with eclipse XDB‐C18 column. The sulphide transfer data showed 40% free sulphide, 38% acid‐labile and 10% total sulphide transfer happens at 15 min. Performance of the chip was attributed to buffer, chip bonding technique and a silicon membrane that allows selective diffusion of hydrogen sulphide.