ABSTRACT
Devising carbon dots with long wavelength emission (red light or near infrared), high selectivity and good bio-compatibility is critical in fluorescence detection and imaging, but achieving this goal remains a great challenge. Herein, near-infrared emissive carbon dots (NIR-CDs) with obvious emission characteristic of 653 nm were synthesized through hydrothermally treatment of toluidine bule and gallic acid. Noticeably, the NIR-CDs exhibited excellent selectivity and sensitivity to hypochlorite (ClO-), and the limit of detection is as low as 42.7 nM. The selective recognition reaction between ClO- and the surface functional groups of NIR-CDs inhibits the fluorescence from NIR-CDs. The quenching mechanism was confirmed by fluorescence lifetime decays, FT-IR spectroscopy and UV-vis absorption spectra. More remarkably, the NIR-CDs have rich hydrophilic groups showed lower cytotoxicity, excellent bio-compatibility and specific cell membrane localization ability. The established spectrofluorometric method based on NIR-CDs has been used to determination of ClO- level in tap water sample, the recoveries were 97.7 %-103.3 %. In addition, the NIR-CDs also has been successfully applied for the imaging of cell membrane. The study provides a novel idea for developing NIR ClO- probe as well as cell membrane localization probe based on CDs, which present bright prospects in real water samples monitoring and cell membrane imaging.
Subject(s)
Carbon , Cell Membrane , Hypochlorous Acid , Quantum Dots , Hypochlorous Acid/analysis , Quantum Dots/chemistry , Carbon/chemistry , Humans , Cell Membrane/chemistry , Spectrometry, Fluorescence , Limit of Detection , Spectroscopy, Fourier Transform Infrared , Spectroscopy, Near-Infrared/methods , Fluorescent Dyes/chemistry , Fluorescent Dyes/chemical synthesis , HeLa CellsABSTRACT
Yellow fluorescent silicon quantum dots (y-SiQDs) with 22.2% fluorescence quantum yield were synthesized by a simple hydrothermal method using 3-glycidoxypropyl triethoxysilane (GOTS) and m-aminophenol. The excitation wavelength is 550 nm with an emission wavelength of 574 nm, which effectively avoids the interference of biological autofluorescence. Notably, the synthesis approach does not require any post-modification and the y-SiQDs can be directly used for hydrogen sulfide (H2S) quantification due to static quenching. It exhibits high sensitivity and excellent selectivity for H2S with a 0.2-10 µM (R2 = 0.9953) linear range and detection limit of 54 nM. y-SiQDs have excellent stability and biocompatibility and can be used for H2S imaging in living cells and onion tissues.
Subject(s)
Hydrogen Sulfide , Quantum Dots , Silicon , Onions , Limit of Detection , Fluorescent DyesABSTRACT
Fluorescence resonance energy transfer (FRET) is often applied to construct fluorescent probes for acquiring high selectivity and sensitivity. According to the FRET theory, a homodimer composed of two identical fluorophores with a small Stokes shift has only weak fluorescence due to homo-FRET between fluorophores, and the fluorescence could be recovered after the destruction of the homodimer. In this study, we designed and synthesized a homodimer fluorescent probe, namely 1,3,5,7-tetramethyl-8-(4'-phenylthiophenol)-boron difluoride-dipyrrole methane dimer (D-TMSPB), based on this turn-on strategy. In D-TMSPB, the disulfide moiety was selected as the response moiety of biothiols, and BODIPY fluorophore was chosen as both donor and acceptor in FRET due to the ultra-small Stokes shifts and obvious overlap of its excitation/emission peak. D-TMSPB exhibited only weak fluorescence. After selective reaction with biothiols, FRET was destroyed and the derivative exhibited strong fluorescence at 514 nm with the limit of detection of about 0.15 µM for GSH. Notably, the derivative of biothiols shows remarkable fluorescence only in acidic conditions, which accords with the internal environment of lysosome. Thus, D-TMSPB was applied to image the biothiols of lysosome in living cells. The turn-on fluorescence of D-TMSPB indicated that homo-FRET is a practical strategy to design turn-on fluorescent probes, particularly for the sensing mechanism based on leaving groups.
ABSTRACT
Pd0-mediated Tsuji-Trost reaction is a practical strategy to design fluorescent probes for carbon monoxide (CO) sensing, and in such reaction CO can reduce Pd2+ to Pd0 in-situ and remove allyl groups on fluorophores. In most of these probes, esters are commonly used to link allyl on fluorophores. We found that the ester groups could be hydrolyzed by esterase activity of fetal bovine serum (FBS), while FBS is a requisite in cell culture, and the hydrolysis could interfere the Pd0-mediated Tsuji-Trost reaction. In this study, we synthesized a fluorescent probe (Cou-CO) using allyl ether as reaction site rather than allyl ester. Cou-CO is non-fluorescence, and could react with CO under the presence of Pd0 to form Cou with strong fluorescence, and the maximum excitation and emission wavelengths of Cou are 464â¯nm and 495â¯nm respectively. Cou-CO shows excellent selectivity to CO and could avoid the effect of FBS with the limit of detection for CO is 78â¯nm. Finally, Cou-CO was successfully applied for imaging of CO in living cells.
Subject(s)
Allyl Compounds/chemistry , Carbon Monoxide/analysis , Esters/chemistry , Ethers/chemistry , Fluorescent Dyes/chemistry , Molecular Imaging/methods , Allyl Compounds/chemical synthesis , Allyl Compounds/toxicity , Carbon Monoxide/chemistry , Fluorescent Dyes/chemical synthesis , Fluorescent Dyes/toxicity , HeLa Cells , Humans , Limit of Detection , Onions/chemistry , Sensitivity and Specificity , Serum Albumin, Bovine/chemistryABSTRACT
Carbonyl compounds are widely distributed in organisms, and the commonly used methods for determination of them like UV/fluorescence/mass spectrometry always require derivatization reagents. However, the reported derivatization reagents have significant difference in reactivity, which is very unfavorable for developing highly reactive reagent. In this study, we theoretically investigated the factors affecting the reactivity of hydrazine-based derivatization reagents, and proposed a strategy for filtering highly reactive reagents by quantum chemical calculation. With this strategy, N-propyl-4-hydrazino-1,8-naphthalimide (NPHNA) was filtered out as a fluorescent derivatization reagent. Taking aliphatic aldehydes as representatives, we evaluated the reactivity of NPHNA for carbonyl compounds. The derivatization of NPHNA with aliphatic aldehydes could be finished at room temperature within 60â¯min or 35⯰C within 35â¯min, which showed higher reactivity than the most popular UV/MS reagent, 2,4-dinitrophenylhydrazine (DNPH). We believe that the strategy we proposed in this work is of great potential to design highly reactive UV/fluorescent/MS labeling reagents for carbonyl compounds and even other analytes.