A Perspective on Polythiophenes as Conformation Dependent Optical Reporters for Label-Free Bioanalytics

Abstract

Poly(3-alkylthiophene) (PT)-based conjugated polyelectrolytes (CPEs) constitute an important class of responsive polymers with excellent optical properties. The electrostatic interactions between PTs and target analytes trigger complexation and concomitant conformational changes of the PT backbones that produce distinct optical responses. These conformation-induced optical responses of the PTs enable them to be utilized as reporters for detection of various analytes by employing simple UV−vis spectrophotometry or the naked eye. Numerous PTs with unique pendant groups have been synthesized to tailor their interactions with analytes such as nucleotides, ions, surfactants, proteins, and bacterial and viral pathogens. In this perspective, we discuss PTtarget analyte complexation for bioanalytical applications and highlight recent advancements in point-of-care and field deployable assays. Subsequently, we highlight a few areas of critical importance for future applications of PTs as reporters, including (i) design and synthesis of specific PTs to advance the understanding of the mechanisms of interaction with target analytes, (ii) using arrays of PTs and linear discriminant analysis for selective and specific detection of target analytes, (iii) translation of conventional homogeneous solution-based assays into heterogeneous membrane-based assay formats, and finally (iv) the potential of using PT as an alternative to conjugated polymer nanoparticles and dots in bioimaging.

Self-Immolative Polythiophene for Sunlight Inactivation of Harmful Cyanobacteria

“…In the presence of algal cells, similar immolation of PT10 was also observed (Figures E, S17, and S18), which could be further confirmed by high-resolution mass spectrometry (HRMS) (Figure S19 and Table S7) and TOC evaluation (Figure S20). Compared with PT10 alone, the bleaching rate of PT10 in the presence of algae was somewhat faster, probably because of the algae adsorption-induced conformation change (Figure S8) of PT10 that resulted in less resistance to photobleaching. , Therefore, the high photosensitization activity and good stability of PT10 ensured high-performance photoinactivation of M. aeruginosa and simultaneous slow self-immolation, which could be further evidenced by the TOC change of the mixture (Figure S21).…”

Aptamers Targeting Membrane Proteins for Sensor and Diagnostic Applications

“…that effectively mediate interdisciplinary biological applications [175]. Optical reporting with aptamer-conjugated polymers is simple, cost-effective, can be fluorescence-or colorimetrybased, and is achievable in both a labeled and an unlabeled manner [176,177].…”

Binding Studies of Cationic Conjugated Polymers and DNA for Label-Free Fluorescent Biosensors

“…The conformational change of CCPs was also used for the detection of bacteria. 24 In addition, CCPs, especially polythiophene, can be trapped and aligned into polyisocyanides to form a hybrid biomimetic hydrogel with a highly ordered conformation, which was used for antiinfection wound dressings. 25 While many interesting applications based on CCPs and DNA have been demonstrated, most of them only focused on improving the sensitivity and specificity for target detection, leaving a fundamental understanding of this system largely unexplored.…”

“…Polythiophenes were believed to form a highly conjugated and planar conformation when interacting with ssDNA and returned to a less conjugated conformation after complementary DNA (cDNA) was added, which was deduced from the optical properties of the CCPs. This method was also applied to the detection of nucleases, nucleotide phosphates, and ATP due to changes in the number of negative charges or hydrophobicity of targets. − Due to conformational changes of aptamers after binding with targets, CCPs are useful for the fabrication of aptamer-based biosensors as well. − For example, aptamers for potassium and α-thrombin can form G-quadruplex structures, while thymine–Hg 2+ –thymine interactions can fold DNA into duplex regions, , both of which resulted in specific biosensors. The conformational change of CCPs was also used for the detection of bacteria .…”

“…This method was also applied to the detection of nucleases, nucleotide phosphates, and ATP due to changes in the number of negative charges or hydrophobicity of targets. − Due to conformational changes of aptamers after binding with targets, CCPs are useful for the fabrication of aptamer-based biosensors as well. − For example, aptamers for potassium and α-thrombin can form G-quadruplex structures, while thymine–Hg 2+ –thymine interactions can fold DNA into duplex regions, , both of which resulted in specific biosensors. The conformational change of CCPs was also used for the detection of bacteria . In addition, CCPs, especially polythiophene, can be trapped and aligned into polyisocyanides to form a hybrid biomimetic hydrogel with a highly ordered conformation, which was used for anti-infection wound dressings …”