Dual-Modal Colorimetric/Fluorescence Molecular Probe for Ratiometric Sensing of pH and Its Application

As traditional pH meters cannot work well for minute regions (such as subcellular organelles) and in harsh media, molecular pH-sensitive devices for monitoring pH changes in diverse local heterogeneous environments are urgently needed. Here, we report a new dual-modal colorimetric/fluorescence merocyanine-based molecular probe (CPH) for ratiometric sensing of pH. Compared with previously reported pH probes, CPH bearing the benzyl group at the nitrogen position of the indolium group and the phenol, which is used as the acceptor for proton, could respond to pH changes immediately through both the ratiometric fluorescence signal readout and naked-eye colorimetric observation. The sensing process was highly stable and reversible. Most importantly, the suitable p<i>K</i>_a value (6.44) allows CPH to presumably accumulate in lysosomes and become a lysosome-target fluorescent probe. By using CPH, the intralysosomal pH fluctuation stimulated by antimalaria drug chloroquine was successfully tracked in live cells through the ratiometric fluorescence images. Additionally, CPH could be immobilized on test papers, which exhibited a rapid and reversible colorimetric response to acid/base vapor through the naked-eye colorimetric analysis. This proof-of-concept study presents the potential application of CPH as a molecular tool for monitoring intralysosomal pH fluctuation in live cells, as well as paves the way for developing the economic, reusable, and fast-response optical pH meters for colorimetric sensing acid/base vapor with direct naked-eye observation

Morpholine Derivative-Functionalized Carbon Dots-Based Fluorescent Probe for Highly Selective Lysosomal Imaging in Living Cells

The development of a suitable fluorescent probe for the specific labeling and imaging of lysosomes through the direct visual fluorescent signal is extremely important for understanding the dysfunction of lysosomes, which might induce various pathologies, including neurodegenerative diseases, cancer, and Alzheimer’s disease. Herein, a new carbon dot-based fluorescent probe (<b>CDs-PEI-ML</b>) was designed and synthesized for highly selective imaging of lysosomes in live cells. In this probe, PEI (polyethylenimine) is introduced to improve water solubility and provide abundant amine groups for the as-prepared <b>CDs-PEI</b>, and the morpholine group (<b>ML</b>) serves as a targeting unit for lysosomes. More importantly, passivation with PEI could dramatically increase the fluorescence quantum yield of <b>CDs-PEI-ML</b> as well as their stability in fluorescence emission under different excitation wavelength. Consequently, experimental data demonstrated that the target probe <b>CDs-PEI-ML</b> has low cytotoxicity and excellent photostability. Additionally, further live cell imaging experiment indicated that <b>CDs-PEI-ML</b> is a highly selective fluorescent probe for lysosomes. We speculate the mechanism for selective staining of lysosomes that <b>CDs-PEI-ML</b> was initially taken up by lysosomes through the endocytic pathway and then accumulated in acidic lysosomes. It is notable that there was less diffusion of <b>CDs-PEI-ML</b> into cytoplasm, which could be ascribed to the presence of lysosome target group morpholine on surface of <b>CDs-PEI-ML</b>. The blue emission wavelength combined with the high photo stability and ability of long-lasting cell imaging makes <b>CDs-PEI-ML</b> become an alternative fluorescent probe for multicolor labeling and long-term tracking of lysosomes in live cells and the potential application in super-resolution imaging. To best of our knowledge, there are still limited carbon dots-based fluorescent probes that have been studied for specific lysosomal imaging in live cells. The concept of surface functionality of carbon dots will also pave a new avenue for developing carbon dots-based fluorescent probes for subcellular labeling

Highly Sensitive Naphthalimide-Based Fluorescence Polarization Probe for Detecting Cancer Cells

Fluorescence polarization (FP)-based signal is a self-referencing fluorescence signal, and it is less dependent on dye concentration and environmental interferences, which makes FP measurement an attractive alternative sensing technology to fluorescence intensity-based detection. However, most of the fluorescence polarization probes were constructed by introducing fluorescein, rhodamine, and cyanine dyes, which have relatively shorter excited-state lifetimes compared with BODIPY and naphthalimide dyes. Herein, a first naphthalimide based fluorescence polarization probe (<b>BIO</b>) was designed and synthesized for selective and direct detection of cancer cells. The relatively longer excited-state lifetimes and high photostability of naphthalimide makes <b>BIO</b> more sensitive and accuracy in quantitative determination of HeLa cells in homogeneous solution without cell lysis and further separation steps. The detection limit of <b>BIO</b> for HeLa cells was about 85 cells mL^–1, the linear range was from 2.5 × 10² cells mL^–1 to 1 × 10⁶ cells mL^–1 and the response time is no more than 25 min. Moreover, due to the relatively high photostability of naphthalimide, <b>BIO</b> was particularly suitable for live cell imaging under continuous irradiation with confocal microscopy, and the specific interaction of <b>BIO</b> with CD44-overexpressing cell lines was clearly visualized. Importantly, this <b>BIO</b> based sensing platform offers a direct and real-time tool for cancer cell diagnosis when complemented with the use of naphthalimide-based fluorescence polarization probe

De Novo Green Fluorescent Protein Chromophore-Based Probes for Capturing Latent Fingerprints Using a Portable System

Rapid visualization of latent fingerprints, preferably at their point of origin, is essential for effective crime scene evaluation. Here, we present a new class of green fluorescent protein chromophore-based fluorescent dyes (LFP-Yellow and LFP-Red) that can be used for real-time visualization of LFPs within 10 s. Compared with traditional chemical reagents for LFPs, these fluorescent dyes are completely water-soluble, exhibit low cytotoxicity, and are harmless to users. Level 1–3 details of the LFPs could be clearly revealed through “off–on” fluorescence signal readout. Additionally, the fluorescent dyes were constructed based on an imidazolinone core and so do not contain pyridine groups or metal ions, which ensures that the DNA is not contaminated during extraction and identification after the LFPs are treated with the dyes. Combined with our as-developed portable system for capturing LFPs, LFP-Yellow and LFP-Red enabled the rapid capture of LFPs. Therefore, these green fluorescent protein chromophore-based probes provide an approach for the rapid identification of individuals who were present at a crime scene

De Novo Green Fluorescent Protein Chromophore-Based Probes for Capturing Latent Fingerprints Using a Portable System

Rapid visualization of latent fingerprints, preferably at their point of origin, is essential for effective crime scene evaluation. Here, we present a new class of green fluorescent protein chromophore-based fluorescent dyes (LFP-Yellow and LFP-Red) that can be used for real-time visualization of LFPs within 10 s. Compared with traditional chemical reagents for LFPs, these fluorescent dyes are completely water-soluble, exhibit low cytotoxicity, and are harmless to users. Level 1–3 details of the LFPs could be clearly revealed through “off–on” fluorescence signal readout. Additionally, the fluorescent dyes were constructed based on an imidazolinone core and so do not contain pyridine groups or metal ions, which ensures that the DNA is not contaminated during extraction and identification after the LFPs are treated with the dyes. Combined with our as-developed portable system for capturing LFPs, LFP-Yellow and LFP-Red enabled the rapid capture of LFPs. Therefore, these green fluorescent protein chromophore-based probes provide an approach for the rapid identification of individuals who were present at a crime scene

De Novo Green Fluorescent Protein Chromophore-Based Probes for Capturing Latent Fingerprints Using a Portable System

Rapid visualization of latent fingerprints, preferably at their point of origin, is essential for effective crime scene evaluation. Here, we present a new class of green fluorescent protein chromophore-based fluorescent dyes (LFP-Yellow and LFP-Red) that can be used for real-time visualization of LFPs within 10 s. Compared with traditional chemical reagents for LFPs, these fluorescent dyes are completely water-soluble, exhibit low cytotoxicity, and are harmless to users. Level 1–3 details of the LFPs could be clearly revealed through “off–on” fluorescence signal readout. Additionally, the fluorescent dyes were constructed based on an imidazolinone core and so do not contain pyridine groups or metal ions, which ensures that the DNA is not contaminated during extraction and identification after the LFPs are treated with the dyes. Combined with our as-developed portable system for capturing LFPs, LFP-Yellow and LFP-Red enabled the rapid capture of LFPs. Therefore, these green fluorescent protein chromophore-based probes provide an approach for the rapid identification of individuals who were present at a crime scene

De Novo Green Fluorescent Protein Chromophore-Based Probes for Capturing Latent Fingerprints Using a Portable System

Rapid visualization of latent fingerprints, preferably at their point of origin, is essential for effective crime scene evaluation. Here, we present a new class of green fluorescent protein chromophore-based fluorescent dyes (LFP-Yellow and LFP-Red) that can be used for real-time visualization of LFPs within 10 s. Compared with traditional chemical reagents for LFPs, these fluorescent dyes are completely water-soluble, exhibit low cytotoxicity, and are harmless to users. Level 1–3 details of the LFPs could be clearly revealed through “off–on” fluorescence signal readout. Additionally, the fluorescent dyes were constructed based on an imidazolinone core and so do not contain pyridine groups or metal ions, which ensures that the DNA is not contaminated during extraction and identification after the LFPs are treated with the dyes. Combined with our as-developed portable system for capturing LFPs, LFP-Yellow and LFP-Red enabled the rapid capture of LFPs. Therefore, these green fluorescent protein chromophore-based probes provide an approach for the rapid identification of individuals who were present at a crime scene

Combining Magnetic Resonance Imaging with Photothermal Therapy of CuS@BSA Nanoparticles for Cancer Theranostics

The treatment of tumors has been a wide concern by a large number of scientific researchers. Combining magnetic resonance imaging (MRI) with photothermal therapy (PTT) enables cancer theranostics to be more efficient and accurate. Herein, we synthesized CuS@BSA nanoparticles with an average grain diameter of about 16.5 nm through a facile one-pot eco-friendly and user-friendly strategy and it was found to have strong near-infrared absorption property and magnetic resonance imaging ability so that it can be utilized as a multifunctional agent for cancer theranostic. The in vitro toxicity study showed that CuS@BSA nanoparticles with low toxicity could kill cancer cells with the 980 nm NIR laser effectively. Furthermore, they exhibit a certain value of relaxivity (<i>r</i>₁ = 0.26 mM^–1·s^–1) compared to that of clinically widely used reagent Magnevist (<i>r</i>₁ = 3.13 mM^–1·s^–1). The resulting product of CuS@BSA nanoparticles with their magnetic resonance imaging (MRI) and photothermal therapeutic capabilities could represent a kind of potential candidate for cancer theranostics

Selective and Ratiometric Fluorescent Trapping and Quantification of Protein Vicinal Dithiols and in Situ Dynamic Tracing in Living Cells

Protein vicinal dithiols play fundamental roles in intracellular redox homeostasis due to their involvement in protein synthesis and function through the reversible vicinal dithiol oxidation to disulfide. To provide quantitative information about the global distribution and dynamic changes of protein vicinal dithiols in living cells, we have designed and synthesized a ratiometric fluorescent probe (<b>VTAF</b>) for trapping of vicinal dithiol-containing proteins (VDPs) in living cells. <b>VTAF</b> exhibits a ratiometric fluorescence signal upon single excitation, which enables self-calibration of the fluorescence signal and quantification of endogenous vicinal dithiols of VDPs. Its potential for in situ dynamic tracing of changes of protein vicinal dithiols under different cellular redox conditions was exemplified. <b>VTAF</b> facilitated the direct observation of subcellular distribution of endogenous VDPs via ratiometric fluorescence imaging and colocalization assay. And the results suggested that there are abundant VDPs in mitochondria. Moreover, some redox-sensitive VDPs are also present on cell surface which can respond to redox stimulus. This ratiometric fluorescence technique presents an important extension to previous fluorescence intensity-based probes for trapping and quantifying protein vicinal dithiols in living cells, as well as its visible dynamic tracing of VDPs

Unique Tri-Output Optical Probe for Specific and Ultrasensitive Detection of Hydrazine

An optical probe based on colorimetric and ratiometric as well as chemiluminometric signal outputs is developed for the specific detection of hydrazine. On the basis of a Gabriel-type reaction, hydrazinolysis of a simple probe CF (4-phtalamide-<i>N</i>-(4′-methylcoumarin) naphthalimide) produces both the fluorescence of 7-amino-4-methylcoumarin with the max emission wavelength changed from 480 to 420 nm (along with a color change from yellow to transparent) and the luminol chemiluminescence activated by H₂O₂ with a max emission wavelength at 450 nm. The experimental detection limit of hydrazine is 3.2 ppb (0.1 μM). Selectivity experiments proved CF has excellent selectivity to hydrazine over other interfering substances. Probe CF was also successfully applied in the vapor hydrazine detection over other interfering volatile analytes. Furthermore, the probe CF loaded thin-layer chromatography (TLC) plate for vapor hydrazine detection limit is 5.4 mg/m³ which is well below the half lethal dose of hydrazine gas for mice (LC₅₀(mice), 330 mg/m³) and National Institute of Occupational Safety and Health’s immediately dangerous to life or health limit (NIOSHIDLH, 66 mg/m³). With H₂O₂, only hydrazinolysis product luminol can be lighted at 450 nm, other species have no signal. Probe CF can also be used for the detection of hydrazine in HeLa cells