Carbon Dioxide-Controlled Assembly of Water-Soluble Conjugated Polymers Catalyzed by Carbonic Anhydrase.

The CO2 -responsive and biocatalytic assembly based on conjugated polymers has been demonstrated by combining the signal amplification property of the polythiophene derivative (PTP) and the catalytic actions of carbonic anhydrase (CA). CO2 is applied as a new trigger mode to construct the smart assembly by controlling the electrostatic and hydrophobic interactions between the PTP molecules in aqueous solution, leading to the visible fluorescence changes. Importantly, the assembly transformation of PTP can be specifically and highly accelerated by CA based on the efficient catalytic activity of CA for the inter-conversion between CO2 and HCO3- , mimicking the CO2 -associated biological processes that occurred naturally in living organisms. Moreover, the PTP-based assembly can be applied for biomimetic CO2 sequestration with fluorescence monitoring in the presence of CA and calcium.

Conjugated Polymer-Based Hybrid Materials for Turn-On Detection of CO2 in Plant Photosynthesis.

Detection of carbon dioxide (CO2) is of fundamental importance in diverse applications ranging from environmental analysis to agricultural production. In this work, a hybrid probe based on guanidinium-pendent oligofluorene (G-OF) and water-soluble conjugated polythiophene (PTP) has been developed for the turn on detection of CO2 with low background signal, taking advantage of the efficient fluorescence quenching of the tight aggregate of G-OF/PTP. In the presence of CO2, the electrostatic repulsion between G-OF and PTP can be effectively enhanced through protonation of the side chains, leading to the disaggregation and thus the "turn-on" fluorescence. The strategy allows for the light-up visible detection of CO2 with high sensitivity. Importantly, this system is capable of sensitively monitoring the concentration changes of CO2 in the process of the photosynthesis, which represents a concept to monitor the photosynthesis based on water-soluble conjugated polymers.

Conjugated Polythiophene for Rapid, Simple, and High-Throughput Screening of Antimicrobial Photosensitizers.

The cationic conjugated poly[3-(3'-N,N,N-triethylamino-1'-propyloxy)-4-methyl-2,5-thiophene hydrochloride] (PMNT) has been developed for high-throughput screening of photodynamic antimicrobial chemotherapy photosensitizers (PSs). The bacterial number can be detected quantitatively by PMNT via various fluorescence quenching efficiencies. The photosensitized inactivation of bacteria is not efficient with ineffective PSs, and thus the bacteria grow exponentially and can be coated tightly by PMNT through electrostatic and hydrophobic interactions, resulting in aggregates and fluorescence quenching of PMNT, whereas, conversely, effective PSs lead to original and strong fluorescence of PMNT. This new platform of high-throughput screening is promising for discovering new PSs.

Ca2+-controlled assembly for visualized detection of conformation changes of calmodulin.

A new strategy has been designed for visualized detection of the conformation changes of calmodulin bound to target peptide (CaM-M13) based on the conformation sensitive property of a water-soluble conjugated polythiophene derivative (PMNT) and the electrostatic interactions of PMNT/CaM-M13. Interestingly, the direct visualized PMNT color changes under UV irradiation and the turbidity changes of samples in aqueous medium can be applied to detect the conformation changes as well as the controllable assembly of PMNT/CaM-M13 with Ca(2+) in aqueous medium. Because of the specific binding of Ca(2+), the assembly of PMNT/CaM-M13 can be applied to sense calcium as well.

Nucleobase-functionalized conjugated polymer for detection of copper(II).

In recent years, supramolecular organization of thiophene derivatives, oligo- and polythiophene, have been developed with various designs to achieve complex functions. Here, we describe the synthesis and characterization of a conjugated polymer with thymidine side chain bases and polythiophene backbones (PTT) instead of phosphate bonds in DNA, and the PTT exhibits exceptional fluorescence quenching efficiency upon binding of Cu(2+) ions in aqueous medium, which is suggested to be electron transfer from the π* orbit at the excited state of PTT to the 3d orbit of Cu(2+) ions and subsequent Cu(2+)-mediated interpolymer π-stacking aggregation. Furthermore, Cu(2+) ions can be selectively and easily monitored by the fluorescence quenching of PTT, which can be used for detection of Cu(2+) ions with good selectivity and high sensitivity in aqueous medium. Both experimental and theoretical methods have been devoted to demonstrate the strong affinity and steric interaction of PTT toward Cu(2+). These findings will illustrate new directions for the design of nucleobase-functionalized materials with transition metals responsive activity.