Cellular Imaging Applications Research Articles

One-pot microwave-assisted in situ reduction of Ag+and Au3+ions by Citrus limon extract and their carbon-dots based nanohybrids: a potential nano-bioprobe for cancer cellular imaging

In situreduction and microwave-assisted synthesis of Ag/C-dot and Au/C-dot nanohybrids using natural lemon extract for cancer cellular imaging applications.

Blue-emitting and amphibious metal (Cu, Ni, Pt, Pd) nanodots prepared within supramolecular polymeric micellesfor cellular imaging applications

We propose a new method for the preparation of blue-emitting and amphibious metal (Cu, Ni, Pt, Pd) nanodots using supramolecular polymeric micelle nanoreactors ​for cellular imaging applications.

Lipoprotein Nanoplatelets: Brightly Fluorescent, Zwitterionic Probes with Rapid Cellular Entry.

Semiconductor nanoplatelets (NPLs) are planar nanocrystals that have recently attracted considerable attention due to their quantum-well-like physics, atomically precise thickness, and unique photophysical properties such as narrow-band fluorescence emission. These attributes are of potential interest for applications in biomolecular and cellular imaging, but it has been challenging to colloidally stabilize these nanocrystals in biological media due to their large dimensions and tendency to aggregate. Here we introduce a new colloidal material that is a hybrid between a NPL and an organic nanodisc composed of phospholipids and lipoproteins. The phospholipids adsorb to flat surfaces on the NPL, and lipoproteins bind to sharp edges to enable monodisperse NPL encapsulation with long-term stability in biological buffers and high-salt solutions. The lipoprotein NPLs (L-NPLs) are highly fluorescent, with brightness comparable to that of wavelength-matched quantum dots at both the ensemble and single-molecule levels. They also exhibit a unique feature of rapid internalization into living cells, after which they retain their fluorescence. These unique properties suggest that L-NPLs are particularly well suited for applications in live-cell single-molecule imaging and multiplexed cellular labeling.

Highly Stable Near-Infrared Fluorescent Organic Nanoparticles with a Large Stokes Shift for Noninvasive Long-Term Cellular Imaging.

Fluorescent organic nanoparticles based on small molecules have been regarded as promising candidates for bioimaging in recent years. In this study, we report a highly stable near-infrared (NIR) fluorescent organic nanoprobes based on nanoparticles of an anthraquinone derivate with strong aggregation-induced emission (AIE) characteristics and a large Stokes shift (>175 nm). These endow the nanoprobe with high fluorescent brightness and high signal-to-noise ratio. On the other hand, the nanoprobe also shows low cytotoxicity, good stability over a wide pH range, superior resistance against photodegradation and photobleaching comparing to typical commercial fluorescent organic dyes such as fluorescein sodium. Endowed with such merits in term of optical performance, biocompatibility, and stability, the nanoprobe is demonstrated to be an ideal fluorescent probe for noninvasive long-term cellular tracing and imaging applications. As an example, it is shown that strong red fluorescence from the nanoprobe can still be clearly observed in A549 human lung cancer cells after incubation for six generations over 15 days.

Fluorescent Biotin Analogues for Microstructure Patterning and Selective Protein Immobilization.

Benzyl substitution on ureido nitrogens of biotin led to manifestation of aggregation-induced emission, which was studied by steady-state fluorescence, microscopy, and TD-DFT, providing a rationale into the observed photophysical behavior. Besides exhibiting solvatochromism, the biotin derivatives revealed emission peaks centered at ∼430 and 545 nm, which has been attributed to the π-π stacking interactions. Our TD-DFT results also correlate the spectroscopic data and quantify the nature of transitions involved. The isothermal titration calorimetry data substantiates that the binding of the biotin derivatives with avidin are pretty strong. These derivatives on lithographic patterning present a platform for site specific strept(avidin) immobilization, thus opening avenues for potential applications exploiting these interactions. The fluorescent biotin derivatives can thus find applications in cellular biology and imaging.

Multifunctional Logic in a Photosensitizer with Triple-Mode Fluorescent and Photodynamic Activity.

Herein we describe a photosensitizer (PS) with the capacity to perform multiple logic operations based on a pyrene-containing phthalocyanine (Pc) derivative. The system presents three output signals (fluorescence at 377 and 683 nm, and singlet oxygen ((1)O2) production), which are dependent on three inputs: two chemical (concentration of dithiothreitol (DTT) and acidic pH) and one physical (visible light above 530 nm for (1)O2 sensitization). The multi-input/multioutput nature of this PS leads to single-, double-, and triple-mode activation pathways of its fluorescent and photodynamic functions, through the interplay of various interrelated AND, ID, and INHIBIT gates. Dual fluorescence emissions are potentially useful for orthogonal optical imaging protocols while (1)O2 is the main reactive species in photodynamic therapy (PDT). We thus expect that this kind of PS logic system will be of great interest for multimodal cellular imaging and therapeutic applications.

Development of an Optical Nanosensor Incorporating a pH-Sensitive Quencher Dye for Potassium Imaging.

One of the key challenges in the design of a sensor for measuring extracellular changes in potassium concentration is selectivity against the competing cation, sodium. Here, we present an optode-based nanosensor selective to potassium ions, owing to the addition of a pH-sensitive quencher molecule paired with a static fluorophore. The nanosensor was fabricated using emulsification and characterized in solution by absorbance and fluorescence spectroscopy. The resulting nanosensor detected potassium with nearly 1 order of magnitude higher selectivity compared to our chromoionophore-based optode nanosensors. In addition to the improved selectivity, the nanosensor has the following properties required for measurements in a biological environment: (1) a physiologically relevant dynamic range, (2) response to potassium ions at a physiological ionic strength, and (3) response to serum potassium in the presence of fouling biological components. The potassium nanosensor described in this study is envisioned to have application in cellular imaging and drug screening.

Preparation of biocompatible fluorescent core–shell nanoparticles for cellular imaging

Abstract In this work, we report a facile method to prepare biocompatible fluorescent core–shell structured nanoparticles. The as-prepared nanoparticle was composed of a gold core enclosed in a protein shell. An amine-reactive fluorophore, 5-(and-6)-carboxyfluorescein-succinimidyl ester, was assembled onto the outer shell completing the fluorescent nanoparticle. Fluorescence quenching of the fluorophore was efficiently avoided because of the presence of the shell, which served as a spacer layer between the fluorophore and the gold core. There was an increase in fluorescence intensity, when compared to the fluorophore in its free state that can be attributed to the metal-enhanced fluorescence effect of the gold core. Well-dispersed green fluorescent faculae were observed when the as-prepared nanoparticles were studied by the confocal laser scanning microscope, demonstrating the successful assembly of the fluorophores. The nanoparticles were readily uptaken by A549 cancer cells and the results of cell viability assays evidenced their good biocompatibility. Cumulatively, these findings indicate their potential application for cellular imaging.

Facile Microwave-Assisted Solid-Phase Synthesis of Highly Fluorescent Nitrogen-Sulfur-Codoped Carbon Quantum Dots for Cellular Imaging Applications.

Carbon quantum dots (CQDs) have recently attracted significant attention for both their fundamental science and technological applications as a new class of fluorescent zero-dimensional nanomaterials with a size below 10 nm. However, the reported methods of synthesis were generally less suitable for the large-scale production of the CQDs with high-fluorescent quantum yield (QY). In the paper, a novel one-pot microwave-assisted drying synthesis approach was presented to prepare CQDs with high QY of 61.3 % for the first time. The production yield of CQDs was 35±3 % in weight. The as-prepared CQDs were characterized by various techniques such as TEM, AFM, XRD, XPS, FTIR spectroscopy, UV/Vis absorption spectroscopy, and fluorescence spectroscopy. The results showed that the high QY of CQDs was largely attributed to the dual doping of nitrogen and sulphur into CQDs. Such CQDs were then used as live-cell imaging reagents due to their high QY, good water dispersibility, fine biocompatibility, high photostability, and low cytotoxicity.

Facile, Large-Quantity Synthesis of Stable, Tunable-Color Silicon Nanoparticles and Their Application for Long-Term Cellular Imaging.

We herein introduce a facile, low-cost photochemical method capable of rapid (<40 min) and large-quantity (∼10 g) production of highly fluorescent (quantum yield: 25%) silicon nanoparticles (SiNPs) of tunable optical properties (peak emission wavelength in the range of 470-560 nm) under ambient air conditions, by introducing 1,8-naphthalimide as a reducing agent and surface ligands. The as-prepared SiNPs feature robust storage stability and photostability preserving strong and stable fluorescent during long-term (>3 h) high-power UV irradiation, in contrast to the rapid fluorescence quenching within 2 h of conventional organic dyes and II-VI quantum dots under the same conditions. The as-prepared SiNPs serving as photostable nanoprobes are workable for cellular imaging in long-term manners. Our findings provide a powerful method for mild-condition and low-cost, large-quantity production of highly fluorescent and photostable SiNPs for various promising applications.

Multifunctional hydroxyapatite nanoparticles for drug delivery and multimodal molecular imaging

Hydroxyapatite (HAp) is the most important constituent of biological tissues such as bone and teeth and exhibits several characteristic features. HAp nanoparticles (NPs) are good host materials and can be functionalized with various kinds of dopants and substrates. By endowing HAp NPs with desired properties in order to render them suitable for biomedical applications including cellular imaging, non-invasive and quantitative visualisation of molecular process occurring at cellular and subcellular levels becomes possible. Depending on their functional properties, HAp based nanoprobes can be divided into three classes, i.e., luminescent HAp NPs (for both downconversion and upconversion luminescence), magnetic HAp NPs, and luminomagnetic HAp NPs. Luminomagnetic HAp NPs are particularly attractive in terms of bimodal imaging and even multimodal imaging by virtue of their luminescence and magnetism. Functionalised HAp NPs are potential candidates for targeted drug delivery applications. This review (with 166 references) spotlights the cellular imaging applications of three types of HAp NPs. Specific sections cover aspects of molecular imaging and the various imaging modes, a comparison of the common types of nanoprobes for bioimaging, synthetic methods for making the various kinds of HAp NPs, followed by overviews on fluorescent NPs for bioimaging (such as quantum dots, gold nanoclusters, lanthanide-doped or fluorophore-doped NPs), magnetic HAp NPs for use in magnetic resonance imaging (MRI), luminomagnetic HAp NPs for bimodal imaging, and sections on drug delivery as well as cellular imaging applications of HAp based nanoprobes (including targeted imaging).

Scale-Up Synthesis of Fragrant Nitrogen-Doped Carbon Dots from Bee Pollens for Bioimaging and Catalysis.

Fragrant nitrogen-doped carbon dots of gram scale can be prepared from commercial bee pollens by a hydrothermal process. These carbon dots of 1-2 nm in size show promising applications in cellular imaging and catalysis/photocatalysis.

Rational design of a split-Cas9 enzyme complex

Cas9, an RNA-guided DNA endonuclease found in clustered regularly interspaced short palindromic repeats (CRISPR) bacterial immune systems, is a versatile tool for genome editing, transcriptional regulation, and cellular imaging applications. Structures of Streptococcus pyogenes Cas9 alone or bound to single-guide RNA (sgRNA) and target DNA revealed a bilobed protein architecture that undergoes major conformational changes upon guide RNA and DNA binding. To investigate the molecular determinants and relevance of the interlobe rearrangement for target recognition and cleavage, we designed a split-Cas9 enzyme in which the nuclease lobe and α-helical lobe are expressed as separate polypeptides. Although the lobes do not interact on their own, the sgRNA recruits them into a ternary complex that recapitulates the activity of full-length Cas9 and catalyzes site-specific DNA cleavage. The use of a modified sgRNA abrogates split-Cas9 activity by preventing dimerization, allowing for the development of an inducible dimerization system. We propose that split-Cas9 can act as a highly regulatable platform for genome-engineering applications.

Colloidal Quantum Dot-Based Light Emitting Diodes With Solution Processed Electron Transporting Layer for Cellular Imaging

We report a quantum dot (QD)-based light emitting diode (LED) structure with a solution processed zinc oxide electron transporting layer, with patterning of anode and cathode on the substrate toward cellular imaging applications. Compared with the use of sputtered thin films, solution processed electron transporting layer improves robustness of the device, as crystalline ZnO shows low CB and VB edge energy levels, efficiently suppressing hole leakage current resulting in LEDs with longer lifetimes. We demonstrate a working lifetime of more than 12 h and a shelf-life of more than 180 days for the devices. Our solution-based process is applicable to microcontact printed and also spin-coated QD films. Further, we demonstrate electroluminescence of QD LEDs at 580and 600-nm emission wavelengths, with typical turn-ON voltage of 12 V. We compare operating characteristics of an array of individually addressable LEDs fabricated on a single substrate, with average size of each element being 800 μm × 200 μm. The LEDs with spin-coated ETL show a lifetime increase of more than three orders of magnitude compared with devices made using sputtered ETL layer. We find marginal increases in the intensity and uniformity of devices fabricated using a spin-coated ZnO layer. Finally, we demonstrate a compact multicolor light source for cell characterizations by imaging HEMA 3 stained MDA-MB 231 breast cancer cells on-chip. We demonstrate the capability of the devices as a light source by measuring intensity across stained cells with QDLEDs of two different wavelengths and show the correlation as expected with the absorption profile of the fluorescent dye.

Preparation of emissive glucose-containing polymer nanoparticles and their cell imaging applications

Water dispersible, bright and biocompatible fluorescent glycopolymer nanoparticles were facilely fabricated, and their cellular imaging application was successfully demonstrated.

Preparation of biocompatible and photostable PEGylated red fluorescent nanoparticles for cellular imaging

Biocompatible and photostable PEGylated red fluorescent nanoparticles were preparedviasurface-initiated ATRP and their cellular imaging application was successfully demonstrated.

Oxygen-driven, high-efficiency production of nitrogen-doped carbon dots from alkanolamines and their application for two-photon cellular imaging

A novel oxygen-driven method has been developed for low-cost, large-scale, and high-efficiency production of nitrogen-doped carbon dots (N-C-dots) using various alkanolamines as both precursors and solvents.

Luminogenic iridium azide complexes.

The synthesis and characterization of luminogenic, bioorthogonal iridium probes is described. These probes exhibit long photoluminescence lifetimes amenable to time-resolved applications. A simple, modular synthesis via 5-azidophenanthroline allows structural variation and allows optimization of cell labeling.

Squaraine-based polymer dots with narrow, bright near-infrared fluorescence for biological applications.

This article describes the design and development of squaraine-based semiconducting polymer dots (Pdots) that show large Stokes shifts and narrow-band emissions in the near-infrared (NIR) region. Fluorescent copolymers containing fluorene and squaraine units were synthesized and used as precursors for preparing the Pdots, where exciton diffusion and likely through-bond energy transfer led to highly bright and narrow-band NIR emissions. The resulting Pdots exhibit the emission full width at half-maximum of ∼36 nm, which is ∼2 times narrower than those of inorganic quantum dots in the same wavelength region (∼66 nm for Qdot705). The squaraine-based Pdots show a high fluorescence quantum yield (QY) of 0.30 and a large Stokes shift of ∼340 nm. Single-particle analysis indicates that the average per-particle brightness of the Pdots is ∼6 times higher than that of Qdot705. We demonstrate bioconjugation of the squaraine Pdots and employ the Pdot bioconjugates in flow cytometry and cellular imaging applications. Our results suggest that the narrow bandwidth, high QY, and large Stokes shift are promising for multiplexed biological detections.

Controlling self-assembly of DNA-polymer conjugates for applications in imaging and drug delivery.

Amphiphilic supramolecular structures such as micelles and vesicles can be formed through phase-driven self-assembly of monomer units having discrete hydrophilic and hydrophobic blocks. These structures show great promise for use in medical and biological applications, and incorporating DNA as the hydrophilic block of the amphiphilic monomers enables the creation of assemblies that also take advantage of the unique information storage and molecular recognition capabilities of DNA. Recently, significant advances have been made in the synthesis of DNA-polymer conjugates (DPCs), controlling the morphology of DPC assemblies by altering monomer structure, and probing the effect of assembly on DNA stability and hybridization. Together, these investigations have laid the framework for using DPCs in drug delivery, cellular imaging, and other applications in materials science and chemistry.