The Evaluation of Ester Functionalised TCF‐Based Fluorescent Probes for the Detection of Bacterial Species

Abstract

The ester functionality is commonly seen in the areas of chemical biology and medicinal chemistry for the design of cell‐permeable active molecules. Ester‐based pro‐drug/pro‐sensor strategies are employed to mask polar functional groups (i. e. carboxylic acids) and improve the overall cell permeability of these functional molecules. However, their use as reactive units for sensing applications, including bacterial detection, has not been fully explored. Herein, we synthesised two TCF‐based fluorescent probes, TCF‐OAc and TCF‐OBu. As expected, both TCF‐OAc and TCF‐OBu demonstrated a significant fluorescence (22‐ and 43‐fold, respectively) and colorimetric response (yellow to purple) towards porcine liver esterase (PLE) with a limit of detection of 1.18 mU/mL and 0.45 mU/mL, respectively. With these results in hand, the ability of these probes to detect planktonic suspensions of gram‐positive Staphylococcus aureus (S. aureus) and gram‐negative Pseudomonas aeruginosa (P. aeruginosa), and Escherichia coli (E. coli) were evaluated. Different fluorescence responses for gram‐positive and gram‐negative bacteria were observed between TCF‐OAc and TCF‐OBu. After 1 h incubation, TCF‐OAc proved more sensitive towards S. aureus, demonstrating a significant fluorescence “turn on” response (16‐fold); whereas, TCF‐OBu was more selective towards P. aeruginosa, with a 22‐fold increase in the fluorescence response observed. These results demonstrate the influence of the ester chain length on the selectivity for bacterial species.

Molecular Boronic Acid-Based Saccharide Sensors

“…Binding events that can change conformation or relative orientation and distance of the paired motifs can therefore be detected through resulting fluorescence modulation. , Molecular reporting systems that utilize an ICT fluorescence mechanism are often referred to as “push–pull” systems, wherein an electron donating group and electron withdrawing group are typically positioned at opposing points on a single molecule . Modulation of the distribution of electron density through analyte binding (or irreversible reaction in the case of dosimeters), , results in a shift of the spectral properties of the molecule which can be manifested as changes in fluorescence.…”

Tuning the Solid- and Solution-State Fluorescence of the Iron-Chelator Deferasirox

“…This was achieved by subjecting the iodinated deferasirox derivatives (ExMI, ExBisI, and ExTrisIsee Supporting Information for chemical structures) to Suzuki cross-coupling with thiophene-2-boronic acid pinacol ester (see Supporting Information Schemes S3 and S8 for reaction scheme). Next, in an effort to obtain long-wavelength emissive derivatives, we modified the phenol arms on the deferasirox scaffold to produce donor−π–acceptor (D−π–A) systems. , Here, Suzuki cross-coupling between ExMI and 5-formyl-2-thienylboronic afforded the aldehyde derivative ExAld (see Supporting Information Scheme S5 for reaction scheme). Appreciating that aromatic aldehydes are often used for the synthesis of near-infrared fluorophores and fluorescent probes, ExAld was then reacted with malononitrile to afford ExMC (12)Figure d (see Supporting Information Scheme S6 for reaction scheme).…”

“…Next, in an effort to obtain long-wavelength emissive derivatives, we modified the phenol arms on the deferasirox scaffold to produce donor−π−acceptor (D−π−A) systems. 21,22 Here, Suzuki cross-coupling between ExMI and 5formyl-2-thienylboronic afforded the aldehyde derivative ExAld (see Supporting Information Scheme S5 for reaction scheme). Appreciating that aromatic aldehydes are often used for the synthesis of near-infrared fluorophores and fluorescent probes, 23 ExAld was then reacted with malononitrile to afford ExMC (12)Figure 1d (see Supporting Information Scheme S6 for reaction scheme).…”

Fluorescent Chemosensors for Ion and Molecule Recognition: The Next Chapter

“…Fluorescent chemosensors have already shown great promise in real-world situations and applications, including but not limited to: the detection of environmental waste pollutants, detection of chemical warfare agents, fluorescence guided surgery, whole body diagnostic imaging, in vivo flow cytometry, and eHealth diagnostic devices (point of care (POC) testing) (Christodouleas et al, 2018;Jiao et al, 2020;Wei and Xunbin, 2021). In addition, colorimetric sensors have been established as potentially attractive sensing platforms due to their low cost as well as their capability to respond to stimuli with concurrent colour (UV-Vis) changes that could be discerned using the naked eye (López-Alled et al, 2017;Gwynne et al, 2021a;Gwynne et al, 2021b). This means colorimetric sensors are often seen as ideal diagnostic systems for non-expert users .…”