Development and molecular recognition of Calixcrownchip as an electrochemical ALT immunosensor

Resorc[4]arene-Modified Gold-Decorated Magnetic Nanoparticles for Immunosensor Development

In recent years, several efforts have been made to develop selective, sensitive, fast response, and miniaturized immunosensors with improved performance for the monitoring and screening of analytes in several matrices, significantly expanding the use of this technology in a broad range of applications. However, one of the main technical challenges in developing immunosensors is overcoming the complexity of binding antibodies (Abs) to the sensor surface. Most immobilizing approaches lead to a random orientation of Abs, resulting in lower binding site density and immunoaffinity. In this context, supramolecular chemistry has emerged as a suitable surface modification tool to achieve the preorganization of artificial receptors and to improve the functional properties of self-assembled monolayers. Herein, a supramolecular chemistry/nanotechnology-based platform was conceived to develop sensitive label-free electrochemical immunosensors, by using a resorcarene macrocycle as an artificial linker for the oriented antibody immobilization. To this aim, a water-soluble bifunctional resorc[4]arene architecture (RW) was rationally designed and synthesized to anchor gold-coated magnetic nanoparticles (Au@MNPs) and to maximize the amount of the active immobilized antibody (Ab) in the proper "end-on" orientation. The resulting supramolecular chemistry-modified nanoparticles, RW@Au@MNPs, were deposited onto graphite screen printed electrodes which were then employed to immobilize three different Abs. Furthermore, an immunosensor for atrazine (ATZ) analysis was realized and characterized by the differential pulse voltammetry technique to demonstrate the validity of the developed biosensing platform as a proof of concept for electrochemical immunosensors. The RW-based immunosensor improved Ab_ATZ loading on Au@MNPs and sensitivity toward ATZ by almost 1.5 times compared to the random platform. Particularly, the electrochemical characterization of the developed immunosensor displays a linearity range toward ATZ within 0.05-1.5 ng/mL, a limit of detection of 0.011 ng/ml, and good reproducibility and stability. The immunosensor was tested by analyzing spiked fortified water samples with a mean recovery ranging from 95.7 to 108.4%. The overall good analytical performances of this immunodevice suggest its application for the screening and monitoring of ATZ in real matrices. Therefore, the results highlighted the successful application of the resorc[4]arene-based sensor design strategy for developing sensitive electrochemical immunosensors with improved analytical performance and simplifying the Ab immobilization procedure.

Tailored calix[4]arene-gold nanoconjugate as a ultra-sensitive immunosensing nanolabel

The construction of highly sensitive and specific immunosensing nanolabels have attracted tremendous attention in the development of reliable point-of-care disease diagnostics. However, there are still challenges with traditional immunoassays, such as complicated and time-consuming procedure, the use of enzyme label, non-specificity, and require readers for detection. Therefore, we have designed and developed site-directed antibody-immobilized calix[4]arene-gold nanoconjugate based colorimetric immunosensing nanolabel to offer high sensitivity. The prepared nanolabel enabled oriented binding of the antibodies by providing full accessibility of Fab domain for antigen binding. The improved sensitivity of the developed nanolabel was evaluated using vertical flow immunoassay (VFIA) for detecting C-reactive protein (CRP) with a lower detection limit up to 1 ng/ml. Our developed nanolabel was found to be highly specific, easy, quick, and appropriate for onsite detection. The nanolabel is validated with spiked blood samples which exhibited ~90% recovery having a relative error of ~2%. Furthermore, the nanolabel was also used for screening of human blood real samples which showed relative error of ~0.6%. The developed nanolabel can be utilized as a potential nanolabel for the quantitative detection of various biomolecules in clinical samples.