pH Fluctuations In Cells Research Articles

Highly efficient carbon dots for quantitatively visualizing pH fluctuations in cells, zebrafish, mice and tumors.

In vivo pH is closely related to complicated physiological and pathological processes. Quantitatively probing pH and visualizing pH variation via fluorescence (FL) imaging technique in living cells and organisms is crucial but difficult to accomplish. Herein, green fluorescent carbon dots (CDs) were synthesized, and their distinct advantages of extraordinarily high fluorescence quantum yield (FQY, 71.4%), unique photostability, high selectivity, sterling biocompatibility, appropriate pKa for biosensing, enable CDs to serve as pH-activatable probes for real time quantitative detection of continuous pH fluctuation in living cells, zebrafish, mice and tumors. We believe CDs are presently among the best-of-breed pH probes for comprehensive biomedical applications.

A fluorescent nanoprobe based on cell-penetrating peptides and quantum dots for ratiometric monitoring of pH fluctuation in lysosomes

A lysosome-targeting ratiometric fluorescent nanoprobe based on cell-penetrating peptides (CPPs) and quantum dots (QDs) has been developed for monitoring pH fluctuation in living cells. The as-prepared nanoprobe is constructed by Rhodamine B labeled R9RGD CPPs as H+ response unit and the red fluorescent QDs as reference unit to achieve ratiometric pH measurement. With the help of RhB-R9RGD CPPs, the nanoprobe efficiently stains lysosomes and enables discernment of lysosomal pH fluctuation in cells treated with different pH buffers and drug stimulation. The method of using dye labeled CPPs to realize functionalization of nanoparticle in one-step reported herein is expected to obtain wider applications in the detection of subcellular active substances by combining different small molecular probes and functional peptides.

Copper doped carbon dots as the multi-functional fluorescent sensing platform for tetracyclines and pH

Abstract The copper doped fluorescent carbon dots (Cu-CDs) with excellent biocompatibility were prepared from l -tryptophan and copper chloride as precursors through a facilely hydrothermal method. As-prepared Cu-CDs exhibited the bright blue fluorescence and excellent optical stability. In the presence of tetracyclines antibiotics (TCs), the intensely fluorescent quenching of Cu-CDs occurred from internal filtration effect (IFE), providing the foundation of TCs quantification. Meanwhile, the fluorescence intensity of Cu-CDs decreased gradually along with the increasing of pH and a sigmoidal curve was well fitted with the pKa12.49 and pKa2 6.21, respectively. The Cu-CDs as a multi-functional fluorescence sensing platform demonstrated great accuracy and selectivity for tetracyclines (TCs) and pH. On account of practical application, as-synthesized Cu-CDs not only were effectively employed for determination of TCs in antibiotic tablets and milk products, but also could trace nuclear and had been extended to sense and visualize pH fluctuations in cells due to low toxicity and biocompatibility. As a facile and effective multi-functional fluorescent sensor, the proposed Cu-CDs have a significant potential for biosensing and biomedical imaging.

Apoferritin-based tunable nano-indicator for intracellular pH sensing: Regulating response performances and minimizing effects of system fluctuations

A new class of apoferritin-based tunable nano-indicators, utilizing apoferritin (APO) as a template and the dye pair as a signal element, have been developed for intracellular pH sensing. Similar to cocktails making, the nano-indicator with a diameter of ∼10 nm can be flexibly and easily constructed just by mixing commercially available pH-sensitive and pH-insensitive dye pairs (without any derivatization) with APO in solution, based on the pH-dependent depolymerization/self-assembly properties of the bio-derived APO. By using different dye pairs (fluorescein/rhodamine B, fluorescein/RuBpy) for ratiometric design and controlling the dye feed ratio, the pH response performance of the APO-based nano-indicator including response linear range and sensitivity can be flexibly regulated. Compared with free dyes, it has lower cytotoxicity. Moreover, ratiometric signal of the nano-indicators can minimize the effect of system fluctuations, involving ambient temperature, probe local concentration and its solution environment. Furtherly, the nano-indicators have been successfully applied for intracellular pH measurement in the range of 5–7 and the detection of pH fluctuations in cells after different stimuli treatment.

A Red Emissive Two‐Photon Fluorescence Probe Based on Carbon Dots for Intracellular pH Detection

Intracellular pH is closely related with many biological processes, including cellular proliferation, apoptosis, endocytic processes, signal transduction, and enzymatic activity. The use of fluorescent probes has become an essential method for intracellular pH detection, but existing fluorescent probes have substantial limitations, such as requiring tedious synthetic preparation, suffering from an inappropriate response range and insufficiently long emission wavelength. In this work, a red emissive two-photon fluorescence probe based on carbon dots (pH-CDs) is fabricated using a facile one-pot hydrothermal method for the monitoring of intracellular pH. pH-CDs possess a variety of superior properties, including high selectivity, excellent photostability, and low cytotoxicity. Furthermore, they exhibit a pH-sensitive response in the range of 1.0-9.0 and a linear range of 3.5-6.5, which is desirable for tracking the pH value in living cells. It is demonstrated that the pH-dependent fluorescence signal is regulated via switching between aggregation and disaggregation of CDs. More importantly, pH-CDs can be successfully applied to sense and visualize pH fluctuation in cells, tissue, and zebrafish. These findings suggest that the as-prepared pH-CDs probe has significant potential for practical application in living systems.