Micro-capillary sensor for imaging trypsin activity using confined nematic liquid crystals

Abstract

In this study, a simple and sensitive micro-capillary sensor for monitoring trypsin reactions using confined nematic liquid crystals (LCs) was developed. The confined LC droplet was formed through sequential injection of a LC and aqueous solution into an octyltrichlorosilane-pretreated capillary. When the confined LC droplet made contact with an aqueous mixture of phospholipids and poly-L-lysine (PLL) solutions, the electrostatic interaction between the phospholipid and PLL induced realignment of the phospholipid monolayer and produced an optical LC droplet texture of two bright lines. Trypsin can cleave peptides specifically on the carboxyl side of lysine, and in this case, trypsin activity is manifested as removal of this electrostatic interaction, leading to a change in the ordering of LC droplets confined in the capillary. Thus, the orientational transition of LC droplets results in a change in their optical response from two bright lines to a four-petal shape. Control experiments with deactivated trypsin or chymotrypsin confirmed the feasibility of this trypsin detection approach. Using the LC based capillary sensing technique, trypsin levels as low as similar to 0.1 mu g/mL could be detected. This research proposes that LC-based micro-capillary sensing systems can be utilized in the development of highly sensitive and simple sensors for detecting various enzymes. (C) 2016 Elsevier B.V. All rights reserved.