Atomic nanoclusters modified antibodies synthesis and characterization as biorecognition and transduction elements in DNA origami based biosensors

IntroductionIn this work, a previously reported enzyme-free methodology for labelling antibodies using atomic nanoclusters (NCs) embedded in its structure has been set up [1] [2]. The resulting antibodies still maintain the affinity for target antigens. Here we propose a non-conventional immunoassay where the nanocluster-modified antibodies act as a probe and incorporates both, the biorecognition and transduction element. The transduction is performed employing changes in SERS signal when the analyte is bound to the antibodies carrying NCs. The DNA origami will serve to incorporate the elements of the biosensor with nanometric precision, also incorporating nanoparticles (NPs) to enhance SERS signal. This approach offers important advantages over conventional immunoassays, including improved sensitivity, quick turnaround, and suitability for point-of-care (PoC) diagnostics. Results and DiscussionA secondary antibody (anti-rabbit IgG) has been selected to develop this research because it can be employed to detect any IgG from rabbit providing a broader range of application. Two different types of NCs have been synthesized within this work. On the one hand, bimetallic NCs composed by gold and platinum (Au/Pt NCs-IgG). This nanomaterial exhibit peroxidase-like activity. The affinity of these antibodies carrying NCs for target analyte has been tested with a paper-based immunoassay. The detection is performed taking advantage of the catalytic properties of the NCs with the oxidation of a non-soluble chromogenic substrate. The signal is visible by the naked eye and can be further analyse for quantitative results. In Figure 1.A. a scheme of a paper-based immunoassay for the detection of an IgG from rabbit based of Au/Pt NCs-IgG is showed. On the other hand, semiconductor NCs composed by cadmium sulfide (CdS NCs-IgG) has been synthesized. In this case the reduced size of the NCs bring them fluorescent properties. This optical property is used to detect the presence of target analyte on paper-based immunoassays and to test the affinity for target analyte after the synthesis. In this case it is necessary to illuminate with UV-light to reveal the signal. In Figure 1.B. a scheme of a paper-based immunoassay for the detection of an IgG from rabbit based on fluorescent properties of CdS NCs-IgG is showed. ConclusionsThe results of the paper-based immunoassays indicates that the antibody still have affinity for target analyte after the synthesis and can serve as a probe in DNA origami-based biosensors. The proposed strategy offers a new platform for the development of efficient POC nanobiosensores.References[1] V. Mora-Sanz, L. Saa, N. Briz, M. Möller, and V. Pavlov, “Antibody-Directed Synthesis of Catalytic Nanoclusters for Bioanalytical Assays,” ACS Appl. Mater. Interfaces, vol. 12, no. 26, pp. 28993–28999, 2020, doi: 10.1021/acsami.0c05229.[2] V. Mora-Sanz, L. Saa, N. Briz, and V. Pavlov, “Synthesis and Characterization of Antibody-Protected Bimetallic Nanoclusters with Catalytic Properties,” Chem. Mater., vol. 32, no. 19, pp. 8286–8293, 2020, doi: 10.1021/acs.chemmater.0c02096. AcknowledgementsThis project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 964248.