A highly sensitive acidic pH fluorescent probe and its application to E. coli cells

pH-Sensitive and Lysosome Targetable Photosensitizers Based on BODIPYs

Photodynamic therapy (PDT) is an effective and U.S. Food and Drug Administration (FDA) approved treatment for cancer and other diseases. Photosensitizer is one of the three key components that harvest the energy of light at a certain wavelength. Compared to the conventional fluorophores used as photosensitizers, boron dipyrromethene (BODIPY) derivatives have grown fast in recent years due to their low dark toxicity, versatile tunable sites, and easiness of being paired with other treatments. In this paper, two pH-sensitive BODIPY-based photosensitizers (BDC and BDBrC) were synthesized by adding carbazole moieties onto the BODIPY cores (BD and BDBr) through condensation reactions. BDBrC has two Br atoms at the BODIPY core that promote singlet oxygen generation and further red-shift the absorption maximum peak. Both compounds showed sensitivity toward pH change and generated more singlet oxygen under acidic conditions. The cellular uptake and cell imaging experiments showed that BDBrC can selectively target the lysosome organelle. The further dark cell viability and light cytotoxicity indicate the light triggered PDT treatment can be accomplished with BDBrC.

Aqua-friendly organometallic Ir-Pt complexes: pH-responsive AIPE-guided imaging of bacterial cells

In this work, the aggregation-induced photoluminescence emission (AIPE) of three water-soluble heterobimetallic Ir-Pt complexes was reported with insight into their photophysical and electrochemical properties and imaging of bacterial cells. An alkyne appended Schiff's base L, bridges bis-cyclometalated iridium(III) and platinum(II) terpyridine centre. The Schiff's base (N-N fragment) serves as the ancillary ligand to the iridium(III) centre, while the alkynyl end is coordinated to platinum(II). The pH and ionic strength influence the aggregation kinetics of the alkynylplatinum(II) fragment, leading to metal-metal and π-π interactions with the emergence of a triplet metal-metal-to-ligand charge transfer (³MMLCT) emission. The excellent reversibility and photostability of aggregation-induced emission (AIE) of these aqua-friendly complexes were tested for their ability to sense and selectively image E. coli cells at various pH values.

A ratiometric luminescence pH sensor based on YAG:V3+,V5+ nanoparticles

A new type of ratiometric luminescence-based pH sensor is described.

Challenges in Fluorescence Detection of Chemical Warfare Agent Vapors Using Solid-State Films

Organophosphorus (OP)-based nerve agents are extremely toxic and potent acetylcholinesterase inhibitors and recent attacks involving nerve agents highlight the need for fast detection and intervention. Fluorescence-based detection, where the sensing material undergoes a chemical reaction with the agent causing a measurable change in the luminescence, is one method for sensing and identifying nerve agents. Most studies use the simulants diethylchlorophosphate and di-iso-propylfluorophosphate to evaluate the performance of sensors due to their reduced toxicity relative to OP nerve agents. While detection of nerve agent simulants in solution is relatively widely reported, there are fewer reports on vapor detection using solid-state sensors. Herein, progress in organic semiconductor sensing materials developed for solid-state detection of OP-based nerve agent vapors is reviewed. The effect of acid impurities arising from the hydrolysis of simulants and nerve agents on the efficacy and selectivity of the reported sensing materials is also discussed. Indeed, in some cases it is unclear whether it is the simulant that is detected or the acid hydrolysis products. Finally, it is highlighted that while analyte diffusion into the sensing film is critical in the design of fast, responsive sensing systems, it is an area that is currently not well studied.

A lysosome specific, acidic-pH activated, near-infrared Bodipy fluorescent probe for noninvasive, long-term, in vivo tumor imaging

Long-term, in vivo, fluorescent cell tracking probes are useful for understanding complex cellular processes including tissue regeneration, communication, development, invasion, and cancer metastasis. A near-infrared fluorescent, water-soluble probe is particularly important for studying these biological events and processes. Herein, a lysosome specific, near-infrared Bodipy probe with increased fluorescent intensity in the acidic, lysosome environment is reported. This Bodipy probe is packaged in a nanoparticle using DSPE-PEG₂₀₀₀. The resulting nanoparticle is intravenously delivered to a tumor xenograft, where the fluorescent Bodipy becomes useful for non-invasive, long-term, in vivo fluorescent tumor imaging for periods greater than 36 days. These long-term, in vitro and in vitro tracking data indicate that the described Bodipy nanoparticles hold great potential for monitoring biological processes.

A near-infrared ratiometric fluorescence probe base on spiropyran derivative for pH and its application in living cells

The intracellular pH has a significant effect on several essential biological processes such as material transfer, enzymatic action, cell apoptosis et al. Thus, it is necessary to monitor pH fluctuation in living cells. Here, we designed a near-infrared ratiometric fluorescence probe for pH detection. The spectroscopic responses of probe to pH variations were investigated in CH₃OH/PBS (v/v, 1:1) mixed solution at different pH values. The experimental results showed that the probe is sensitive to acidity, and the pK_a of probe is calculated to be 4.85. When the pH was decreased from 9.0 to 1.0, the color of probe solution change from purple to yellow was found by naked eye. Moreover, the probe can be a practical tool for assessing cellular pH by cell imaging.

An unexpected dual-response pH probe based on acridine

A new pH fluorescent probe 2,8-bis(acridin-9-ylethynyl)-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine (TBN), which has two acridine moieties attached to Tröger's base, is a useful fluorescent probe for monitoring extreme acidic and alkaline pH. TBN displays an excellent pH dependent behavior and responds linearly to extreme conditions in the pH ranges of 1.4–3.4 and 12.5–15.0. TBN can represent a novel type of fluorescent probe with perfect emission properties in extreme acidic and alkaline conditions by utilizing only one functional group.

A novel pH fluorescence probe for monitoring extreme acidic and alkaline pH which responds linearly to extreme conditions in the pH ranges of 1.4–3.4 and 12.5–15.0 by utilizing only the acridine moiety.

An acidic pH fluorescent probe based on Tröger's base

A pH fluorescent probeTBPPincorporating an amine moiety and pyridine group through Tröger's base linker was designed and synthesized. The absorption and fluorescence titrations indicated that it can serve as a sensitive probe for pH measuring.