Biocompatible Fluorescent Probes Research Articles

Fe (III) ion modulated l-DOPA protected gold nanocluster probe for fluorescence turn on sensing of ascorbic acid

The design of biocompatible fluorescent probes for targeting vital molecules in brain is highly desirable in recent years since various statistical studies conducted by World Health Organization point out the upcoming risk of neurodegenerative diseases like Alzheimer’s disease and Parkinson’s disease. In this circumstance, we synthesized water soluble fluorescent 3, 4-dihydroxy-l-phenyl alanine (l-DOPA) protected gold nanocluster (l-DOPA-AuNC) as l-DOPA can be effectively transmitted through blood-brain barrier. The as prepared l-DOPA-AuNCs exhibited fluorescence emission at 545nm. Interestingly, no obvious change in fluorescence emission of l-DOPA-AuNC was observed over a broad pH range (3 to 10), in various buffer solutions (10mM phosphate buffer), or in solutions with high ionic strength(2M KCl). However, the unique co-ordination of Fe(III) ions with catechol group on the surface of l-DOPA-AuNCs induce fluorescence quenching. Moreover, the fluorescence of l-DOPA-AuNCs can be regained completely by antioxidants (biological reducing agents) like Ascorbic Acid (AA) with high selectivity over other antioxidants, amino acids and neurotransmitters. The Limit of Detection (LOD) for Fe (III) ion and AA were found to be 25.5zM and 18.4pM respectively. Furthermore, human serum spiked with Fe (III) ions and AA is analyzed using this sensor and show good recovery percentage.

Assembly of a Highly Stable Luminescent Zn5 Cluster and Application to Bio-Imaging.

The assembly sequence of the coordination cluster [Zn5 (H2 L(n) )6 ](NO3 )4 ]⋅8 H2 O⋅2 CH3 OH (Zn5 , H3 L(n) =(1,2-bis(benzo[d]imidazol-2-yl)-ethenol) involves in situ dehydration of 1,2-bis(benzo[d]imidazol-2-yl)-1,2-ethanediol (H4 L) through the formation of the [Zn(H3 L)2 ](+) monomer, dimerization to [Zn2 (H3 L)2 ](+) , dehydration of the ligand to [Zn2 (H2 L(n) )2 ](+) , and the final formation of the pentanuclear cluster. The cluster has the following special characteristics: 1) high stability in both refluxing 37 % HCl and 27 % NH3 , 2) low cytotoxicity, and 3) pH-sensitive fluorescence in the visible-to-near-infrared (Vis/NIR) region in the solid state and in solution. We have applied it as a fluorescent probe both in vivo and in vitro. Its H-bonding ability is the key to its affinity and selectivity for imaging lysosomes in HeLa cells and tumors in male BALB/C mice. It provides a new type of sensitive and biocompatible fluorescent probe for detecting small tumors (13.5 mm(3) ).

Assembly of a Highly Stable Luminescent Zn5 Cluster and Application to Bio‐Imaging

AbstractThe assembly sequence of the coordination cluster [Zn5(H2Ln)6](NO3)4]⋅8 H2O⋅2 CH3OH (Zn5, H3Ln=(1,2‐bis(benzo[d]imidazol‐2‐yl)‐ethenol) involves in situ dehydration of 1,2‐bis(benzo[d]imidazol‐2‐yl)‐1,2‐ethanediol (H4L) through the formation of the [Zn(H3L)2]+ monomer, dimerization to [Zn2(H3L)2]+, dehydration of the ligand to [Zn2(H2Ln)2]+, and the final formation of the pentanuclear cluster. The cluster has the following special characteristics: 1) high stability in both refluxing 37 % HCl and 27 % NH3, 2) low cytotoxicity, and 3) pH‐sensitive fluorescence in the visible‐to‐near‐infrared (Vis/NIR) region in the solid state and in solution. We have applied it as a fluorescent probe both in vivo and in vitro. Its H‐bonding ability is the key to its affinity and selectivity for imaging lysosomes in HeLa cells and tumors in male BALB/C mice. It provides a new type of sensitive and biocompatible fluorescent probe for detecting small tumors (13.5 mm3).

Biocompatible Fluorescent Probe with the Aggregation-induced Emission Characteristic for Live Cell Imaging

A new kind of biocompatible probe (PEG-TPEFE) with aggregation-induced emission (AIE) characteristic was reported, which was synthesized from fluorene, tetraphenylethylene (TPE) and polyethylene glycol monomethyle ether 1000 (PEG1000). PEG- TPEFE can aggregate into nanosphere and emit strong blue fluorescence in aqueous media. Cytotoxicity assay reveals low cytotoxicity and excellent biocompatibility of this nanoprobe. This nanoprobe was internalized and accumulated by live cells and shown high photostability. Keywords: Fluorescent probe, aggregation-induced emission (AIE), photophysical properties, cellular imaging

A new type of biocompatible fluorescent probe AFN for fixed and live cell imaging of intracellular lipid droplets.

We discovered a new class of nontoxic, highly fluorogenic and biocompatible probe AFN for selective staining of intracellular Lipid Droplets (LDs) in both fixed and live human cervical cancer cells (HeLa) and 3T3-L1 pre-adipocytes without any background artifacts. The salient features of the probe are its visible excitation maximum, aqueous compatibility, selectivity and remarkable stability (for more than a week) in live cells, even better than commercially available Nile red.

A retrievable, water-soluble and biocompatible fluorescent probe for recognition of Cu(II) and sulfide based on a peptide receptor

A novel fluorescent probe C–GGH for recognition of Cu2+ and S2− was designed and synthesized by incorporation a natural tripeptide GGH (Gly-Gly-His) moiety, which acts as a recognition unit for Cu2+, to a coumarin fluorophore. C–GGH displayed ON–OFF type fluorescence response towards Cu2+ with high selectivity in 100% aqueous solution. Furthermore, the in situ generated non-fluorescent C–GGH–Cu2+ complex can serve as an effective OFF–ON type fluorescent probe for selective sensing sulfide anion. Due to the strong binding affinity of S2− to Cu2+, sulfide anion can extract Cu2+ from C–GGH–Cu2+ complex, resulting the release of C–GGH and the revival of fluorescent emission of the system. Techniques of emission spectrometry, NMR, mass spectrometry, and HPLC were used to confirm the displacement mechanism of C–GGH–Cu2+ for sensing sulfide anion. The probe C–GGH–Cu2+ allowed detection of S2− in aqueous buffer solution with a LOD (limit of detection) of 0.44μM. By taking advantages of the natural tripeptide GGH, the sensor exhibits excellent biocompatibility and water solubility. Moreover, the cell imaging study demonstrated that the probe can be exploited to detect sulfur anion in biological systems.

One-step hydrothermal approach to fabricate carbon dots from apple juice for imaging of mycobacterium and fungal cells

A facile green hydrothermal method was developed for the preparation of fluorescent carbon dots (CDs) using apple juice as a raw material. The synthesized fluorescent CDs were characterized by UV–vis, fluorescence, Fourier transform infrared (FT-IR), dynamic light scattering (DLS), high resolution transmission electron microscopic (HR-TEM), life-time measurement and laser scanning confocal microscopic techniques. The CDs showed bright blue emission under UV-light (λex=365nm). The CDs were used as alternative biocompatible fluorescent probes for imaging of bacteria (Mycobacterium tuberculosis and Pseudomonas aeruginosa) and fungal (Magnaporthe oryzae). It was shown that the prepared CDs had no toxic effect on the both cells lines (bacteria and fungal), indicating that the CDs did not inhibit growth of bacterial and fungal cells, which confirms that the CDs exhibit good biocompatibility.

Azide-based fluorescent probes: imaging hydrogen sulfide in living systems.

Hydrogen sulfide is a redox active sulfur species that is endogenously generated in mammalian systems as an antioxidant and signaling molecule to support cellular function. The fundamental and ubiquitous actions of hydrogen sulfide demand sensitive and specific methods to track this biomolecule as it is produced within living organisms with temporal and spatial regulation. In this context, the hydrogen sulfide-mediated reduction of an azide to an amine is a useful method for organic synthesis, and this reaction has successfully been exploited to yield biocompatible fluorescent probes for hydrogen sulfide detection in vitro and in cells. This chapter provides protocols and guidelines for applying azide-based fluorescence probes to detecting hydrogen sulfide in living systems, including a protocol that was used to detect endogenous hydrogen sulfide in living single cells using a confocal microscope.

Oligo(phenylene ethynylene) glucosides: modulation of cellular uptake capacity preserving light ON.

A new family of oligo(phenylene ethynylene) (OPE) glucosides has been prepared and characterized. Our results demonstrate that fine-tuning of their photophysical properties can be obtained by acting on the electronics of the core and molecular skeleton. Modulation of the hydrophobic chain length and substituents on the central moieties influences the bioaffinity too. In particular, introducing a NMe2 group on the aromatic central core affords a highly efficient biocompatible fluorescent probe that can be taken up in cytoplasmic vesicles of HEp-2 cells (cells from epidermoid carcinoma larynx tissue). The photophysical behavior, high quantum yield, and stability open the way to the use of the OPE family as stains for cellular imaging analysis by fluorescence microscopy.

Lanthanum-Doped Hydroxyapatite Nanoparticles as Biocompatible Fluorescent Probes for Cellular Internalization and Biolabeling

Rod-shaped nanoparticles of lanthanum-doped hydroxyapatite (LA-HAp) were synthesized by a modified sol– gel method at a low temperature of 100 C. The (La+Ca):P ratio was maintained at 1.67 and the La/Ca+La ratio was varied as x= 0.02, 0.06 and 0.1. XRD, FTIR, EDAX and TEM analysis indicated that pure, crystalline La-incorporated HAp rod-shaped nanoparticles of 15–25 nm diameter and 100–120 nm length, were obtained. On increasing the concentration of La, from x= 0.02 to 0.1, an increase in crystallinity and crystallite size was achieved. These particles were internalized by human embryonic kidney and human adenocarcinoma cells and exhibited fluorescence when observed under TRITC and FITC filters using epifluorescence microscopy. La-HAp nanoparticles with x = 0.02 exhibited the highest internalization, maximum intracellular fluorescence and no cytotoxicity. The cell viability and internalization decreased with increases in La concentration. Nanoparticles corresponding to x= 0.1 exhibited spindle-shaped morphology with filopodia and the presence of stress granules.

Biocompatible fluorescent UV-VIS and NIR probes for the detection of ß-Amyloid Plaques and Tau fibrils

Biocompatible fluorescent UV-VIS and NIR probes for the detection of ß-Amyloid Plaques and Tau fibrils

Shining a light into live cells

A new biocompatible near-infrared fluorescent probe enables super-resolution imaging of cellular proteins in live cells using a range of different labelling techniques.

In vitro cytotoxicity of fluorescent silica nanoparticles hybridized with aggregation-induced emission luminogens for living cell imaging.

Fluorescent silica nanoparticles (FSNPs) can provide high-intensity and photostable fluorescent signals as a probe for biomedical analysis. In this study, FSNPs hybridized with aggregation-induced emission (AIE) luminogens (namely FSNP-SD) were successfully fabricated by a surfactant-free sol-gel method. The FSNP-SD were spherical, monodisperse and uniform in size, with an average diameter of approximately 100 nm, and emitted strong fluorescence at the peak of 490 nm. The FSNP-SD selectively stained the cytoplasmic regions and were distributed in the cytoplasm. Moreover, they can stay inside cells, enabling the tacking of cells over a long period of time. The intracellular vesicles and multinucleated cells were increase gradually with the rise of FSNP-SD concentration. Both cell viability and survival only lost less than 20% when the cells were exposed to the high concentration of 100 μg/mL FSNP-SD. Additionally, the cell apoptosis and intracellular ROS assay indicated that FSNP-SD had no significant toxic effects at the maximum working concentration of 80 μg/mL. This study demonstrated that the FSNP-SD are promising biocompatible fluorescent probes for living cell imaging.

Synthesis of chemically pure, luminescent Eu3+ doped HAp nanoparticles: a promising fluorescent probe for in vivo imaging applications

The poor solubility, poor biocompatibility and disposal issues make fluorescent quantum dots such as CdSe, CdS, ZnS, InP, InAs, etc. impractical for imaging tissues or intercellular structures. As calcium phosphate is the main inorganic component of human bone and teeth, hydroxyapatite (Ca10(PO4)6(OH)2, HAp) is highly biocompatible and bioactive. Since HAp nanoparticles are not luminescent, a novel inorganic biocompatible fluorescent probe was suggested by doping HAp with lanthanides. Here we report the growth of chemically pure fluorescent HAp nanoparticles synthesized by a new methodology, liquid phase pulsed laser ablation using third harmonics (355 nm) of Nd-YAG laser. Europium doped HAp nanoparticles show emission with prominent peaks at 531 nm, 572 nm, 601 nm and 627 nm upon excitation at a wavelength of 325 nm. The red luminescence could also be observed under visible excitation at 459 nm and is suitable for living cell applications.

Fluorescent Gold Nanoclusters as a Biocompatible Marker for In Vitro and In Vivo Tracking of Endothelial Cells

We have been investigating the fluorescent property and biocompatibility of novel fluorescent gold nanoclusters (FANC) in human aortic endothelial cells (HAEC) and endothelial progenitor cells (EPC). FANC (50-1000 nmol/L) was delivered into cells via the liposome complex. The fluorescence lasted for at least 28 days with a half-life of 9 days in vitro. Examination of 12 transcripts regulating the essential function of endothelial cells after a 72 h delivery showed that only the vascular cell adhesion molecule 1 and the vascular endothelial cadherin were down-regulated at high concentration (500 nmol/L). In addition, no activation of caspase 3 or proliferating cell nuclear antigens was detected. 3-[4,5-Dimethylthiazol-2-yl]-2,5- diphenyltetrazolium bromide (MTT) assay demonstrated that, unlike the markedly suppressed viability in cells treated with quantum dots, FANC had minimal effect on the viability, unless above 500 nmol/L, at which level a minor reduction of viability mainly caused by liposome was found. Tube formation assay showed no impaired angiogenesis in the EPC treated with FANC. In vivo study using hindlimb ischemic mice with an intramuscular injection of FANC-labeled human EPC showed that the cells preserved an angiogenic potential and exhibited traceable signals after 21 days. These findings demonstrated that FANC is a promising biocompatible fluorescent probe.

Surface Modification of Hydroxyapatite Nanocrystallite by a Small Amount of Terbium Provides a Biocompatible Fluorescent Probe

As the main inorganic component of biological bone and tooth enamel, hydroxyapatite (HAP) is highly biocompatible and bioactive. Our recent work has shown that 20 nm HAP can be readily internalized by living cells. However, HAP nanoparticles are not luminescent so that they are difficult to measure in living cells during in vitro experiments. A novel inorganic biological probe was suggested by doping 20 nm HAP with terbium. The calcium ions on the HAP particle surface could be partially replaced by Tb, which resulted in the 20 nm Tb-HAP particles. The Tb-doped HAP became luminescent and could be observed under a visible excitation of 488 nm. Compared with the usual probes, the modified HAP nanoparticles were more photostable and were almost nontoxic. It was important that the HAP characteristics remained after the surface modification with a small amount of Tb. After incubating with rabbit bone marrow mesenchymal stem cells (MSCs) in culture, the luminescence of the internalized HAP in the living cells wa...

Colloidal and monocrystalline Ln3+ doped apatite calcium phosphate as biocompatible fluorescent probes

Ultrafine individualised mono crystalline Ca(10-x)(PO4)(6-x)(HPO4)x(OH)(2-x) deficient calcium hydroxyapatite nanocrystals displaying fluorescence under visible excitation are proposed for utilisation as biocompatible biological probes.