Pt (Ⅱ) complexes-based assays for small biomolecules detection in aqueous media
Creators: name: Kang, Rui
Publisher: name: Karlsruher Institut für Technologie (KIT)
Year: 2022
Subjects: Pt(II) complex
biomolecules sensing
photophysics
supramolecular self-assembling

description: Supramolecular principles such as self-assembly, stimuli-responsiveness, and adaptiveness are widely utilized concepts for developing advanced functional materials. Particularly, they have also significantly impacted analytical science development. In the last two decades, countless supramolecular binders, molecular probes, and chemosensors combined with innovative assays have led to a revolution in molecular sensing and medical diagnostics. Nevertheless, most of these molecular sensing systems are still suffering from either low-binding affinity or low-selectivity or decomposition in complex media such as biofluids, which are the main obstacles limiting their further practical applications. Therefore, the development of new molecular sensing systems that can reach practical requirements is still one of the frontiers in supramolecular chemistry. So far, traditional chromatography-based techniques, e.g., HPLC-MS, are often used for molecular sensing, which are reliable but usually time- and cost-intensive, difficult to do parallel analysis, and require trained personnel. Spectroscopic method-based chemosensors and probes may thus become more suitable for practical applications because of cost-effectiveness, ease of handling, and high-throughput screening ability. Herein, the self-assembling probe (SAP)-based molecular sensing concept is described. By combining molecular reactions and supramolecular interactions, both the high-selective and the high-binding affinity are achieved for the identification and quantification of analytes by utilizing SAP. Beginning with fundamental photophysical knowledge in luminescence, a general introduction of this thesis is given in Chapter 1. As primary candidates for constructing the self-assembling probes (SAPs), transition metal complexes, particularly platinum(II) complexes, are briefly reviewed, including their basic photophysics and applications. In addition, current molecular sensing concepts are introduced and discussed, providing the essential background for the proposed sensing concept in the following text. Small-emitting water-soluble fluorophores are in demand in many application fields, such as fluorescent labels in in-vivo research, indicator dyes in molecular sensing systems, and test cases for theoretical computation studies. In this context, a size-record breaking green-emissive fluorophore 3-hydroxy-isonicotinic aldehyde (HINA, 128 g/mol, λex = 525 nm) is investigated in Chapter 2. Furthermore, HINA also serves as the model case for demonstrating problems that molecular probes face, and it functions as a suitable indicator moiety in the construction of the SAPs. In Chapter 3, the self-assembling probe (SAP)-based molecular sensing concept is described, where time- and spectra-resolved information is observed for the distinction and quantification of target analytes. Due to the combination of the supramolecular and molecular interactions, thirteen tested structural similar analytes can be distinguished by merely using one probe, which overcame the low-selectivity problem of other current molecular sensing concepts. In addition, the potential application of SAPs in human biofluids is explored. As an extension of Chapter 3, Chapter 4 explores the mechanism of the high-selective SAP systems, which is essentially the supramolecular self-assembling of the SAP-analyte conjugates driven by the non-covalent interactions between the adjacent molecules. Therefore, the SAP concept was also applied for chirality sensing as the chiral analyte created a chiral environment and enhanced the chiral signal of the SAP-analyte conjugate. Finally, the conclusion of this thesis is given in Chapter 5. Outlook and suggestions regarding the further investigation of the SAP concepts are included as well.