Development of Polydiacetylene-Based Testosterone Detection as a Model Sensing Platform for Water-Insoluble Hormone Analytes

Immunodetection of Poorly Soluble Substances: Limitations and Their Overcoming

Immunoassays based on the specific antigen-antibody interactions are efficient tools to detect various compounds and estimate their content. Usually, these assays are implemented in water-saline media with composition close to physiological conditions. However, many substances are insoluble or cannot be molecularly dispersed in such media, which objectively creates problems when interacting in aquatic environments. Thus, obtaining immunoreactants and implementing immunoassays of these substances need special methodological solutions. Hydrophobicity of antigens as well as their limited ability to functionalization and conjugation are often overlooked when developing immunoassays for these compounds. The main key finding is the possibility to influence the behavior of hydrophobic compounds for immunoassays, which requires specific approaches summarized in the review. Using the examples of two groups of compounds-surfactants (alkyl- and bisphenols) and fullerenes, we systematized the existing knowledge and experience in the development of immunoassays. This review addresses the challenges of immunodetection of poorly soluble substances and proposes solutions such as the use of hydrotropes, other solubilization techniques, and alternative receptors (aptamers and molecularly imprinted polymers).

A highly sensitive fluorescence biosensor for aflatoxins B1 detection based on polydiacetylene liposomes combined with exonuclease III-assisted recycling amplification

A fluorescence biosensor for determination of aflatoxin B1 (AFB1) based on polydiacetylene (PDA) liposomes and exonuclease III (EXO III)-assisted recycling amplification was developed. The AFB1 aptamer partially hybridizes with complementary DNA (cDNA), which is released upon recognition of AFB1 by the aptamer. Subsequently, the cDNA hybridizes with hairpin H to form double-stranded DNA that undergoes digestion by EXO III, resulting in the cyclic release of cDNA and generation of capture DNA for further reaction. The capture DNA then hybridizes with probe modified on PDA liposomes, leading to aggregation of liposomes and subsequent fluorescence production. This strategy exhibited a limit of detection of 0.18 ng/mL within the linear range 1-100 ng/mL with a determination coefficient > 0.99. The recovery ranged from 92.81 to 106.45%, with relative standard deviations (RSD) between 1.73 and 4.26%, for corn, brown rice, peanut butter, and wheat samples. The stability, accuracy, and specificity of the method demonstrated the applicability for real sample analysis.

Spray-On Colorimetric Sensors for Distinguishing the Presence of Lead Ions

Sprayable stimuli-responsive material coatings represent a new class of detection system which can be quickly implemented to transform a surface into a color-responsive sensor. In this work, we describe a dipicolylamine-terminated diacetylene-containing amphiphile formulation for spray coating on to a simple paper substrate to yield disposable test strips that can be used to detect the presence of lead ions in solution. We find the response to be very selective to only lead ions and that the sensitivity can be modulated by altering the UV curing time after spraying. Sensitive detection to at least 0.1 mM revealed a clear color change from a blue to red phase. This represents the first demonstration of a spray-on sensor system capable of detection of lead ions in solution.