Lysosomal ATP imaging in living cells by a water-soluble cationic polythiophene derivative

Dual-emission red carbon dots for ATP real-time monitoring and quantification to reveal drug and cancer effects on lysosomes

Monitoring and quantifying ATP levels in vivo is essential to understanding its role as a signaling molecule in tumor progression and therapy. Nevertheless, the real-time monitoring and quantitative assessment of lysosomal ATP remains challenging due to the lack of accurate tools in deep tissues. In this study, based on the crosslinking enhanced emission (CEE) effect, we successfully synthesized red carbon dots (R-CDs) with dual emission properties for efficient quantification of intracellular ATP. The R-CDs emit in the near-infrared range and target lysosomes with rapid detection capabilities, rendering them exceptionally well-suited for directly observing and analyzing the dynamics of lysosomal ATP through live cell imaging techniques. Importantly, R-CDs have proven their efficacy in real-time monitoring of drug stimulus-induced fluctuations in endogenous lysosomal ATP concentration and have also been employed for quantifying and distinguishing lysosomal ATP levels among normal and cancer cell lines. These noteworthy findings emphasize the versatility of the R-CD as a valuable imaging tool for elucidating the functional role of lysosomal ATP in drug screening and cancer diagnostics and hold the promise of becoming a reference tool for deepening our understanding of drug mechanisms of action.

A Microfluidic Chip-Based Automated System for Whole-Course Monitoring the Drug Responses of Organoids

Tumor patients-derived organoids, as a promising preclinical prediction model, have been utilized to evaluate ex vivo drug responses for formulating optimal therapeutic strategies. Detecting adenosine triphosphate (ATP) has been widely used in existing organoid-based drug response tests. However, all commercial ATP detection kits containing the cell lysis procedure can only be applied for single time point ATP detection, resulting in the neglect of dynamic ATP variations in living cells. Meanwhile, due to the limited number of viable organoids from a single patient, it is impractical to exhaustively test all potential time points in search of optimal ones. In this work, a multifunctional microfluidic chip was developed to perform all procedures of organoid-based drug response tests, including establishment, culturing, drug treatment, and ATP monitoring of organoids. An ATP sensor was developed to facilitate the first successful attempt on whole-course monitoring the growth status of fragile organoids. To realize a clinically applicable automatic system for the drug testing of lung cancer, a microfluidic chip based automated system was developed to perform entire organoid-based drug response test, bridging the gap between laboratorial manipulation and clinical practices, as it outperformed previous methods by improving data repeatability, eliminating human error/sample loss, and more importantly, providing a more accurate and comprehensive evaluation of drug effects.

A novel nanoparticle fluorescent probe based on a water-soluble conjugated polymer for real-time monitoring of ATP fluctuation and configuration of the Golgi apparatus during the inhibition of glycolysis

BACKGROUND

Adenosine 5'-triphosphate (ATP) plays an important role in cell metabolism and has been regarded as an indicator of cell survival and damage. Golgi apparatus participates in the signal transduction processes of substance transport, ion homeostasis and stress when extracellular substances enter cells. Till now, there is no fluorescent probe for monitoring Golgi ATP level fluctuation and visualizing the configuration change of the Golgi apparatus during the inhibition of glycolysis.

RESULTS

Herein, we report the synthesis of a novel water-soluble cationic polythiophene derivative (PEMTEA) that can be employed as a fluorescent sensor for measuring ATP in the Golgi apparatus. PEMTEA self-assembles into PT-NP nanoparticles in aqueous solution with a diameter of approximately 2 nm. PT-NP displays high sensitivity and superb selectivity towards ATP with a detection limit of 90 nM and a linear detection range from 0 to 3.0 μM. The nanoparticles show low toxicity to HepG2 cells and good photostability in the Golgi apparatus. With the stimulation of Ca2+, PT-NP was practically applied to real-time monitor of endogenous ATP levels in the Golgi apparatus through fluorescence microscopy. Finally, we studied the relationship between the concentration of ATP and configuration of the Golgi apparatus during the inhibition of glycolysis using PT-NP.

SIGNIFICANCE

We have demonstrated that PT-NP can not only indicate the fluctuation and distribution of ATP in the Golgi apparatus, but also give the information of the configuration change of the Golgi apparatus at the single-cell level during the inhibition of glycolysis.

Highly-ordered assembled organic fluorescent materials for high-resolution bio-sensing: a review

Organic fluorescent materials (OFMs) play a crucial role in the development of biosensors, enabling the extraction of biochemical information within cells and organisms, extending to the human body. Concurrently, OFM biosensors contribute significantly to the progress of modern medical and biological research. However, the practical applications of OFM biosensors face challenges, including issues related to low resolution, dispersivity, and stability. To overcome these challenges, scientists have introduced interactive elements to enhance the order of OFMs. Highly-ordered assembled OFMs represent a novel material type applied to biosensors. In comparison to conventional fluorescent materials, highly-ordered assembled OFMs typically exhibit robust anti-diffusion properties, high imaging contrast, and excellent stability. This approach has emerged as a promising method for effectively tracking bio-signals, particularly in the non-invasive monitoring of chronic diseases. This review introduces several highly-ordered assembled OFMs used in biosensors and also discusses various interactions that are responsible for their assembly, such as hydrogen bonding, π-π interaction, dipole-dipole interaction, and ion electrostatic interaction. Furthermore, it delves into the various applications of these biosensors while addressing the drawbacks that currently limit their commercial application. This review aims to provide a theoretical foundation for designing high-performance, highly-ordered assembled OFM biosensors suitable for practical applications. Additionally, it sheds light on the evolving trends in OFM biosensors and their application fields, offering valuable insights into the future of this dynamic research area.

A dual-functional microfluidic chip for guiding personalized lung cancer medicine: combining EGFR mutation detection and organoid-based drug response test

Many efforts have been paid to advance the effectiveness of personalized medicine for lung cancer patients. Sequencing-based molecular diagnosis of EGFR mutations has been widely used to guide the selection of anti-lung-cancer drugs. Organoid-based assays have also been developed to ex vivo test individual responses to anti-lung-cancer drugs. After addressing several technical difficulties, a new combined strategy, in which anti-cancer medicines are first selected based on molecular diagnosis and then ex vivo tested on organoids, has been realized in a single dual-functional microfluidic chip. A DNA-based nanoruler has been developed to detect the existence of EGFR mutations and shrink the detection period from weeks to hours, compared with sequencing. The employment of the DNA-based nanoruler creates a possibility to purposively test anti-cancer drugs, either EGFR-TKIs or chemotherapy drugs, not both, on limited amounts of organoids. Moreover, a DNA-based nanosensor has been developed to recognize intracellular ATP variation without harming cell viability, realizing in situ monitoring of the whole course growth status of organoids for on-chip drug response test. The dual-functional microfluidic chip was validated by both cell lines and clinical samples from lung cancer patients. Furthermore, based on the dual-functional microfluidic chip, a fully automated system has been developed to span the divide between experimental procedures and therapeutic approaches. This study constitutes a novel way of combining EGFR mutation detection and organoid-based drug response test on an individual patient for guiding personalized lung cancer medicine.

Real-time monitoring ATP variation in human cancer organoids for a long term by DNA-based nanosensor

Cancer organoids have become promising tools for predicting drug responses on many different types of cancer. Detecting the adenosine triphosphate (ATP) has currently been considered as a decisive test to profile the growth status and drug responses of organoids. ATP profiling using commercial ATP detection kits, which involve cell lysis, can be performed at a single time spot, causing a clinical dilemma of selecting the optimal time spot to adopt diverse cancer types and patients. This study provides a feasible solution to this dilemma by developing a DNA-based ATP nanosensor to realize real-time ATP monitoring in organoids for a long term. The employment of DNA materials ensures high biocompatibility and low cytotoxicity, which are crucial for fragile organoids; The usage of tetrahedral DNA framework ensures cell permeability and intracellular ATP detection; The introduction of ATP-mediated molecular replacement ensures the high sensitivity and selectivity of ATP recognition. These features result in the first successful attempt on real-time monitoring ATP in organoids for up to 26 days and gaining growth status curves for the whole duration of a drug sensitivity test on human lung cancer organoids.

Amino-Functionalized Perylenediimide Derivative with Dual Fluorescence Emission for the Detection of Ascorbic Acid in Vivo and Vitro

The rapid, sensitive, and selective detection of ascorbic acid (AA) is of significance in medical assays and diagnostics. In this work, a new amino perylenediimide derived (APDI) ratiometric fluorescent probe based on the specific redox reaction of cobalt oxyhydroxide (CoOOH) and AA was constructed. APDI exhibited dual fluorescence emission peaks at 549 and 596 nm with an excitation wavelength of 494 nm. In the presence of CoOOH, the dual fluorescence could be quenched. The dominant fluorescence quenching mechanism was caused by the inner filter effect. Using the red emission as a reference, the fluorescence intensity ratio (F₅₄₉ /F₅₉₆ ) was linearly correlated with the concentration of AA over a range of 0.05 to 1 μM. The limit of detection for AA was found to be 17 nM. Importantly, the probe was successfully used to detect AA in living cells. Therefore, this high sensitivity and selectivity strategy could directly survey the AA levels in real samples.

Cell-membrane-targeted near-infrared fluorescent probe for detecting extracellular ATP

A fluorescent probe for detecting extracellular ATP.

DNA Logic Nanodevices for Real-Time Monitoring of ATP in Lysosomes

DNA logic nanodevices have prospects in molecular recognitions but still face challenges in achieving DNA computation-controlled regulation in specific compartments of living cells. By incorporating the i-motif sequence and ATP aptamers into a Y-shaped DNA (Y-DNA) structure, and applying gold nanoparticles (AuNPs) as the transporting carrier, herein we present a new type of DNA logic nanodevices to monitor the ATP levels in lysosomes of living cells. Triple energy transfers including dual fluorescent resonance energy transfers (FRETs) and a nanometal surface energy transfer (NSET) occurred in the DNA logic nanodevices. It was identified that the proposed nanodevices perform an AND logic operation to output FRET signals only when an endogenous proton and ATP simultaneously exist in the cellular microenvironment. Owing to the use of the i-motif sequence, the nanodevices have lysosome-recognizing capacity without causing alkalization of the acidic organelle, making DNA computation-controlled regulation at the level of cellular organelles achievable. These DNA logic nanodevices show high application prospects in lysosome-related cellular function and disease treatment.

ATP-responsive near-infrared fluorescence MOF nanoprobe for the controlled release of anticancer drug

A near-infrared (NIR) fluorescence nanoprobe named RhI-DOX@ZIF-90 has been synthesized by wrapping the guest molecule (RhI and DOX) into ZIF-90 framework. The nanoprobe itself is non-fluorescent and the drug (DOX) is inactive. Upon the addition of ATP, the structure of RhI-DOX@ZIF-90 is degraded. The fluorescence of RhI is recovered and DOX is released. The nanoprobe can detect ATP with high sensitivity and selectivity. There is good linear relationship between the nanoprobe and ATP concentration from 0.25 to 10 mM and the detection limit is 0.10 mM. The nanoprobe has the ability to monitor the change of ATP level in living cells and DOX is released inducing apoptosis of cancer cells. RhI-DOX@ZIF-90 is capable of targeting mitochondria, which provides a basis for improving the efficiency of drug delivery by mitochondrial administration. In particular, the nanoprobe is preferentially accumulated in the tumor sites and detect ATP in tumor mice by fluorescence imaging using near-infrared fluorescence. At the same time, DOX can be released accurately in tumor sites and have good anti-tumor efficiency. So, this nanoprobe is a reliable tool to realize early diagnosis of cancer and improve effect of anticancer drug.

Recent progress in developing fluorescent probes for imaging cell metabolites

Cellular metabolites play a crucial role in promoting and regulating cellular activities, but it has been difficult to monitor these cellular metabolites in living cells and in real time. Over the past decades, iterative development and improvements of fluorescent probes have been made, resulting in the effective monitoring of metabolites. In this review, we highlight recent progress in the use of fluorescent probes for tracking some key metabolites, such as adenosine triphosphate, cyclic adenosine monophosphate, cyclic guanosine 5'-monophosphate, Nicotinamide adenine dinucleotide (NADH), reactive oxygen species, sugar, carbon monoxide, and nitric oxide for both whole cell and subcellular imaging.

Development of a fluorescent probe for detecting Al3+ in cooked wheaten food based on phosphonic acid group functionalized polythiophene derivatives

As an unnecessary trace element, the content of aluminium in biological systems should be strictly controlled. Therefore, it was necessary to develop a convenient method for detection of aluminium ions. In this study, a fluorescent probe based on polythiophene derivatives was developed and used to detect Al³⁺ in Chinese traditional pasta. The fluorescence of this probe showed a significant decrease in hexamethylenetetramine-HCl buffer solution (pH 5) when Al³⁺ was present. In addition, the probe exhibited good sensitivity and selectivity to Al³⁺ over other metal ions when EDTA was used as the masking agent. Fluorescence intensity had a good linear relationship with the Al³⁺ concentration in the range 0.1-10 μM and the limit of detection for Al³⁺ was 39 nM. Furthermore, the probe was successfully applied to detect Al³⁺ in food samples and the results were consistent with ICP-AES.

AIEgen-based nanoprobe for the ATP sensing and imaging in cancer cells and embryonic stem cells

A turn-on fluorescent nanoprobe (named AAP-1), based on an aggregation-induced emission luminogen (AIEgen), is disclosed for the detection of adenosine triphosphate (ATP), which is an essential element in the biological system. Organic fluorophore (named TPE-TA) consists of tetraphenylethylene (TPE, sensing and signaling moiety) and mono-triamine (TA, sensing moiety), and it forms an aggregated form in aqueous media as a nanoprobe AAP-1. The nanoprobe AAP-1 has multiple electrostatic interactions as well as hydrophobic interactions with ATP, and it displays superior selectivity toward ATP, reliable sensitivity, with a detection limit around 0.275 ppb, and fast responsive (signal within 10 s). Such a fluorescent probe to monitor ATP has been actively pursued throughout fundamental and translational research areas. In vitro assay and a successful cellular ATP imaging application was demonstrated in cancer cells and embryonic stem cells. We expect that our work warrants further ATP-related studies throughout a variety of fields.

Revisiting imidazolium receptors for the recognition of anions: highlighted research during 2010-2019

Imidazolium based receptors selectively recognize anions, and have received more and more attention. In 2006 and 2010, we reviewed the mechanism and progress of imidazolium salt recognition of anions, respectively. In the past ten years, new developments have emerged in this area, including some new imidazolium motifs and the identification of a wider variety of biological anions. In this review, we discuss the progress of imidazolium receptors for the recognition of anions in the period of 2010-2019 and highlight the trends in this area. We first classify receptors based on motifs, including some newly emerging receptors, as well as new advances in existing receptor types at this stage. Then we discuss separately according to the types of anions, including ATP, GTP, DNA and RNA.

Fluorescent Carbon Dots for in Situ Monitoring of Lysosomal ATP Levels

Monitoring the ATP levels in lysosomes in situ is crucial for understanding their involvement in various biological processes but remains difficult due to the interference of ATP in other organelles or the cytoplasm. Here, we report a lysosome-specific fluorescent carbon dot (CD), which can be used to detect ATP in acidic lysosomes with "off-on" changes of yellow fluorescence. These CDs were successfully applied in real-time monitoring of the fluctuating concentration of lysosomal ATP induced by drug stimulation (e.g., chloroquine, etoposide, and oligomycin). Because of the excellent specificity, these CDs are promising agents for drug screening and medical diagnostics through lysosomal ATP monitoring.

Highly Selective Fluorescence Sensing and Imaging of ATP Using a Boronic Acid Groups-Bearing Polythiophene Derivate

A boronic acid groups-bearing polythiophene derivate (L) was designed and synthesized for highly sensitive fluorescence detection of ATP based on a multisite-binding coupled with analyte-induced aggregation strategy. L has a polythiophene backbone as fluorophores and two functional side groups, i.e., quaternary ammonium group and boronic acid group, as multibinding sites for ATP. When various structural analogues such as ADP, AMP, and various inorganic phosphates were added into the aqueous solution of L, only ATP caused a remarkable fluorescence quenching of about 60-fold accompanied by obvious color changes of solution from yellow to purple. The detection limit is estimated to be 2 nM based on 3σ/slope. With the advantage of good water solubility, low toxicity, and highly selective response to ATP, L was successfully utilized as a probe to real-time assay activity of adenylate kinase (ADK) and map fluorescent imaging of ATP in living cells.

Insights into the role of nanostructure in the sensing properties of carbon nanodots for improved sensitivity to reactive oxygen species in living cells

The surface states of carbon nanodots (CDs) were engineered by controlling the chemical structure on the surface of the CDs, which play an important role in the chemiluminescence sensing properties of CDs towards peroxynitrite. Their application in monitoring exogenous and endogenous release of peroxynitrite in living cells is demonstrated.

A new water-soluble polythiophene derivative as a probe for real-time monitoring adenosine 5'-triphosphatase activity in lysosome of living cells

Detection of the adenosine 5'-triphosphatase (ATPase) activity in lysosome of living cells is of great importance for clinical diagnosis of many related diseases, including cancer. In this work, a new water-soluble polythiophene derivative named ZnPT bearing both quaternary ammonium salt groups and dipicolylamine-Zn²⁺ (DPA-Zn²⁺) complexes in its side chain, was designed and synthesized for this propose. The probe mainly localized to lysosome with good biocompatibility and membrane penetration. The real-time, continuous, direct, and label-free assays were achieved through a fluorescence "turn-on" mode by taking advantages of the reaction specificity of ATPase with ATP and the high binding selectivity of ZnPT toward ATP substrate over its hydrolysis product (ADP). This well designed strategy should provide a facile and effective way for investigating ATPase-relevant biological processes.

Water-Soluble Conjugated Polymer as a Fluorescent Probe for Monitoring Adenosine Triphosphate Level Fluctuation in Cell Membranes during Cell Apoptosis and in Vivo

Adenosine triphosphate (ATP) is used as the energy source in cells and plays crucial roles in various cellular events. The cellular membrane is the protective barrier for the cytoplasm of living cells and involved in many essential biological processes. Many fluorescent probes for ATP have been successfully developed, but few of these probes were appropriate for visualizing ATP level fluctuation in cell membranes during the apoptotic cell death process. Herein, we report the synthesis of a new water-soluble cationic polythiophene derivative that can be utilized as a fluorescent sensor for detecting ATP in cell membranes. Poly((3-((4-methylthiophen-3-yl)oxy)propyl)triphenylphosphonium chloride) (PMTPP) exhibits high sensitivity and good selectivity to ATP, and the detection limit is 27 nM. The polymer shows low toxicity to live cells and excellent photostability in cell membranes. PMTPP was practically utilized for real-time monitoring of ATP levels in the cell membrane through fluorescence microscopy. We have demonstrated that the ATP levels in cell membranes increased during the apoptotic cell death process. The probe was also capable of imaging ATP levels in living mice.

A self-assembled amphiphilic imidazolium-based ATP probe

A novel amphiphilic imidazolium-based probe containing a dansyl fluorophore and a long cetyl chain has been developed for ATP recognition. The probe forms self-assembled micelle-like aggregates at low concentration in its aqueous solution and can selectively recognize ATP among other bioactive anions with a significant enhancement in fluorescence emission.

A new FRET-based ratiometric probe for fluorescence and colorimetric analyses of adenosine 5′-triphosphate

A new ratiometric probe for ATP was designed based on the binding-induced modulation of FRET coupled with the ACQ sensing mechanism.

Lysosome-Targeted Turn-On Fluorescent Probe for Endogenous Formaldehyde in Living Cells

As one of the simplest reactive carbonyl species, formaldehyde is implicated in nervous system diseases and cancer. Organelles play crucial roles in various physiological processes in living cells. Accordingly, the detection of endogenous formaldehyde at the subcellular level is of high interest. We herein describe the development of the first organelle-targeted fluorescent formaldehyde probe (Na-FA-Lyso). The new probe exhibits favorable features including a large fluorescence enhancement (about 350-fold) and a fast response to formaldehyde. Significantly, the novel probe Na-FA-Lyso was employed to visualize the endogenous formaldehyde in the lysosomes in living cells for the first time.