Determination of pepsin in human saliva using pepsin-susceptible peptide reporter and colorimetric dipstick assay: a prospective, cross-sectional study.

A simple and effective pepsin detection assay is reported based on a pepsin-susceptible peptide (PSP) reporter degradation strategy. PSP, which can be specifically cleaved by pepsin, was modified with fluorescein isothiocyanate (FITC) and biotin at the N- and C-terminals to be used as a reporter for colorimetric detection of dipsticks. A universal lateral flow dipstick consisting of a streptavidin test line for biotin binding and a sample pad immobilized with a gold-labeled polyclonal (rabbit) anti-FITC antibody was used to verify PSP-based pepsin detection.

Nanozyme based colorimetric detection of biogenic gaseous HS using Ag@Au core/shell nanoplates with peroxidase-like activity.

A highly sensitive and facile colorimetric assay is introduced for detecting biogenic gaseous HS using peroxidase (POD)-like catalytic activity of silver core/gold shell nanoplates (Ag@Au NPls). HS can react with Ag@Au NPls to form AgS or AuS on their surface, which can reduce POD-like activity of Ag@Au NPls and consequently decrease the absorbance at 650 nm due to oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (HO). For in situ and multiple detection of HS, we utilized a microplate cover with 24 polydimethylsiloxane inner wells where Ag@Au NPls reacted with HS gas followed by treatment with TMB/HO.