Polyamine-Functionalized Polydiacetylene (PDA) Vesicles for Colorimetric Sensing of Carbon Dioxide

Emerging Designs and Applications for Biomembrane Biosensors

Nature has inspired the development of biomimetic membrane sensors in which the functionalities of biological molecules, such as proteins and lipids, are harnessed for sensing applications. This review provides an overview of the recent developments for biomembrane sensors compatible with either bulk or planar sensing applications, namely using lipid vesicles or supported lipid bilayers, respectively. We first describe the individual components required for these sensing platforms and the design principles that are considered when constructing them, and we segue into recent applications being implemented across multiple fields. Our goal for this review is to illustrate the versatility of nature's biomembrane toolbox and simultaneously highlight how biosensor platforms can be enhanced by harnessing it.

Polydiacetylene vesicles acting as colorimetric sensor for the detection of plantaricin LD1

The interaction of antimicrobial peptides with membrane lipids plays a major role in numerous physiological processes. In this study, polydiacetylene (PDA) vesicles were synthesized using 10, 12-tricosadiynoic acid (TRCDA) and 1, 2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). These vesicles were applied as artificial membrane biosensor for the detection of plantaricin LD1 purified from Lactobacillus plantarum LD1. Plantaricin LD1 (200 μg/mL) was able to interact with PDA vesicles by changing the color from blue to red with colorimetric response 30.26 ± 0.59. Nisin (200 μg/mL), used as control, also changed the color of the vesicles with CR% 50.56 ± 0.98 validating the assay. The vesicles treated with nisin and plantaricin LD1 showed increased infrared absorbance at 1411.46 and 1000-1150 cm^-1 indicated the interaction of bacteriocins with phospholipids and fatty acids, respectively suggesting membrane-acting nature of these bacteriocins. Further, microscopic observation of bacteriocin-treated vesicles showed several damages indicating the interaction of bacteriocins. These findings suggest that the PDA vesicles may be used as bio-mimetic sensor for the detection of bacteriocins produced by several probiotics in food and therapeutic applications.

Modifying Polydiacetylene Vesicle Compositions to Reduce Non-Specific Interactions

Polydiacetylene (PDA) vesicles provide useful stimuli-responsive behavior as well as by the modular structure afford a means for the design of sensing and delivery systems with tunable target specificity. To reduce inherent non-specific interaction with either anionic or cationic formulations of polydiacetylene vesicles, we explored the use of various lengths of poly(ethylene glycol) (PEG) amphiphiles for integration and polymerization within PDA vesicles. Our results established that as little as 1% of polyethylene glycol amphiphile integration into anionic vesicles was sufficient to significantly reduce non-specific association with mammalian cells. Similarly integrating a low percent of PEG amphiphile content within cationic vesicles could also significantly reduce non-specific cell association, and moreover reduced cytotoxicity. These results may be prove useful in augmenting PDA vesicles formulations for reduced non-specific interaction which is of particularly interest to enhancing selectivity in vesicles designed with integrated targeting moieties for sensing and drug delivery applications.

Naked-Eye Detection of Ethylene Using Thiol-Functionalized Polydiacetylene-Based Flexible Sensors

Ethylene is a hormone that plays a critical role in many phases of plant growth and fruit ripening. Currently, detection of ethylene heavily relies on sophisticated and time-consuming conventional assays such as chromatography, spectroscopy, and electrochemical methods. Herein, we develop a polydiacetylene-based sensor for the detection of ethylene via color change. The sensors are prepared through the reaction between polydiacetylene and Lawesson's reagent that results in decorating polydiacetylene with terminal thiol groups. Upon exposure to ethylene, the sensor changes color from blue to red which is visible to the naked eye. Our device shows a limit of detection for ethylene at 600 ppm in air and can be applied for monitoring ethylene released during the fruit-ripening process. Such easy-to-use ethylene sensors may find applications in plant biology, agriculture, and food industry.