Enhanced cellular internalization of near-infrared fluorescent single-walled carbon nanotubes facilitated by a transfection reagent

Functionalized single-walled carbon nanotubes (SWCNTs) hold immense potential for diverse biomedical applications due to their biocompatibility and optical properties, including near-infrared fluorescence. Specifically, SWCNTs have been utilized to target cells as a vehicle for drug delivery and gene therapy, and as sensors for various intracellular biomarkers. While the main internalization route of SWCNTs into cells is endocytosis, methods for enhancing the cellular uptake of SWCNTs are of great importance. In this research, we demonstrate the use of a transfecting reagent for promoting cell internalization of functionalized SWCNTs. We explore different types of SWCNT functionalization, namely single-stranded DNA (ssDNA) or polyethylene glycol (PEG)-lipids, and two different cell types, embryonic kidney cells and adenocarcinoma cells. We show that internalizing PEGylated functionalized SWCNTs is enhanced in the presence of the transfecting reagent, where the effect is more pronounced for negatively charged PEG-lipid. However, ssDNA-SWCNTs tend to form aggregates in the presence of the transfecting reagent, rendering it unsuitable for promoting internalization. For all cases, cellular uptake is visualized by near-infrared fluorescence microscopy, showing that the SWCNTs are typically localized within the lysosome. Generally, cellular internalization was higher in the adenocarcinoma cells, thereby paving new avenues for drug delivery and sensing in malignant cells.

A novel nanoparticle-based fluorescent sandwich immunoassay for specific detection of Salmonella Typhimurium

The diseases caused by foodborne pathogens have a serious impact on human health and social stability. Conventional detection methods can involve long assay times and complex pretreatment steps, making them unsuitable for rapid, large-scale analysis of food samples. We constructed a novel nano-fluorescence sandwich immunosorbent immunoassay (nano-FSIA) to rapidly detect Salmonella Typhimurium in food, based on strong covalent binding between streptavidin and biotin. We used antibodies coupled to large particle-size fluorescent microspheres as fluorescent probes for direct quantitative analysis of S. typhimurium in milk. The optimized parameters were determined, and specificity and sensitivity were validated in phosphate-buffered saline (PBS) and milk. The results demonstrated a wide dynamic detection range for S. typhimurium (103-108 colony forming units [CFU]/mL), with the limit of detection in PBS and milk at 234 and 346 CFU/mL, respectively. The results of nano-FSIA were consistent with those of plate counts and enzyme-linked immunosorbent assays, providing an effective and promising single-bacterium counting method for the rapid detection of Salmonella.

Construct Fluorescent Solid Lipid Nanoparticles from Bacterial Outer Membrane Vesicles to Study their Properties and Potential Applications as In Vivo and Invitro Imaging Agents

In this study, the new solid lipid nanoparticles were created by combining fluorescent dye, fatty acid, lipid, and bacterial outer membranes. The synthesised particles were roughly 95-100 nm in size. Vero cells cultivated with these nanoparticles showed no cytotoxicity in 5-dimethylthiazol-2-yl-2, 5-diphenyltetrazolium bromide (MTT) assay. In the cell uptake studies, the vero cell line was employed. Cell lines absorbed fluorescent solid lipid nanoparticles (FSL NPs) better, according to the findings. The confocal microscopy results revealed a significant accumulation of FSL NPs in the cytoplasm over time. The results of small animal imaging employing BALB/c mice revealed that the nanoparticles generated provided high contrast signals. Overall, the OMVs-based FSL NPs system offers a unique imaging tool for studying intracellular interactions as well as a viable tool for drug delivery.

An ultrasensitive NIR-IIa' fluorescence-based multiplex immunochromatographic strip test platform for antibiotic residues detection in milk samples

INTRODUCTION

Widely used in livestock breeding, residues of antibiotic drugs in milk have become a threat to food safety and human health. Current rapid detection technologies using colorimetric immunochromatographic strip tests (IST) lack the necessary sensitivity for on-site trace monitoring. Fluorescence-based detection in the near-infrared IIa' (NIR-IIa') region (1000 ∼ 1300 nm) has enormous potential due to greatly minimized auto-fluorescence and light scattering.

OBJECTIVES

The aim of this work is to develop an ultrasensitive IST platform using NIR-IIa' fluorescent nanoparticles as labels for multiplex antibiotic residues detection in milk.

METHODS

NIR-IIa' fluorescent nanoparticles were assembled by encapsulating synthesized NIR-IIa' fluorophores into carboxyl - modified polystyrene nanoparticles. The NIR-IIa' nanoparticles were subsequently used as labels in an IST platform to detect sulfonamides, quinolones, and lincomycin simultaneously in milk. A portable fluorescent reader was fabricated to provide on-site detection. To further validate the developed IST platform, the detection was compared with LC-MS/MS in 22 real milk samples.

RESULTS

Fluorescent nanoparticles were synthesized with low energy emission (1030 nm) and large Stokes shift (>250 nm) showing a much higher signal-to-noise ratio compared with fluorophores emitting in the NIR-I region. The developed IST platform yielded a highly sensitive, simultaneous quantification of sulfonamides, quinolones, and lincomycin in milk with detection limits of 46.7, 27.6 and 51.4 pg/mL, respectively, achieving a wide detection range (up to 50 ng/mL). The IST platform showed good accuracy, reproducibility, and specificity with the portable fluorescent reader which could rapidly quantify in 10 s. These results were better than reported immunochromatographic assays using fluorescent labels, and remarkably, showed a higher recognition ability than LC-MS/MS for real samples.

CONCLUSION

The utility of NIR-IIa' fluorescence-based IST platform for the fast, sensitive, and accurate detection of antibiotics in milk was demonstrated, successfully verifying the potential of this platform in detecting trace materials in complex matrices.

High-performance green-emitting AIE nanoparticles for lateral flow immunoassay applications

Ultrabright green-emissive AIE nanoparticles (AIENPs) were used as signal-amplification probes to enhance the detectability of lateral flow immunoassay (LFIA). The detection performances of the green-emissive AIENP probes in both sandwich and competitive LFIA formats were systematically evaluated. Benefiting from its remarkable fluorescent brightness, the developed AIENP-LFIA showed versatile applicability for the detection of small molecules and macromolecules by using ochratoxin A (OTA) and procalcitonin (PCT) as model analytes, respectively. Under the optimum conditions, the detection limits (LODs) of the fabricated AIENP-LFIA for OTA and PCT were 0.043 ng mL^-1 and 0.019 ng mL^-1, respectively. These LOD values are significantly lower than those of conventional LFIA methods using gold nanoparticles as signal reporters. In addition, we demonstrated the practical application potential of AIENP-LFIA for the detection of OTA in real maize samples and PCT in real serum samples. These results indicated that the ultrabright green-emissive AIENPs were promising as signal output materials for building high-performance LFIA platform and broadening the application scenarios of LFIA.

FRET-mediated quenching of BODIPY fluorescent nanoparticles by methylene blue and its application to bacterial imaging

High resolution and a good signal to noise ratio are a requirement in cell imaging. However, after labelling with fluorescent entities, and after several washing steps, there is often an unwanted fluorescent background that reduces the images resolution. For this purpose, we developed an approach to remove the signal from extra-cellular fluorescent nanoparticles (FNPs) during bacteria imaging, without the need for any washing steps. Our idea is to use methylene blue to quench > 90% of the emission of BODIPY-based fluorescent polymer nanoparticle by a FRET process. This "Hide-and-Seek Game" approach offers a novel strategy to apply fluorescence quenching in bioimaging to improve image accuracy.

Ex-vivo Skin Permeability Tests of Nanoparticles for Microscopy Imaging

Delivery of drugs through the skin is a major challenge in the field of drug delivery systems. Quantification of materials, and specifically nanoparticles, within the skin layers is essential for the development of advanced topical and transdermal delivery systems. We have developed a technique for ex-vivo segmentation and evaluation of human skin samples treated with fluorescent nanoparticles. The method is based on horizontal cryosections of skin samples, followed by confocal microscopy and image analysis. This protocol is relatively simple to perform with basic histological tools, thus it can serve for various dermatology assays.

The Fluorescent Effect of Withania Somnifera Chitosan Nanocomposite as an Effective Contrast Agent for Cancer Theragnostic: Experimental Study in Vitro

Nanomedicine and fluorescent optical imaging are effective in early cancer detection. The current study synthesized biocompatible nanocomposites from natural biomaterials towards inexpensive and safe cancer theragnostic. Two forms of nanocomposites were synthesized using the ionic gelation method: 1. Chitosan/ Withania Somnifera /tripolyphosphate nanocomposites, 2. Withania Somnifera/Chitosan nanocomposites. The nanocomposites were characterized by dynamic light scattering, zeta potential, and the transmission electron microscope. Fourier transform infrared spectroscopy analyzed the Withania Somnifera root water extract, Chitosan, and the synthesized nanocomposites. The cytotoxicity of the nanocomposites was investigated against the colon cancer cells (Caco2 cells) in the absence and the presence of laser (665 nm, 5 mW) irradiation. MTT assay evaluated the cytotoxicity, and Trypan blue assay assessed the cell viability. Cancerous cells were photographed under the inverted microscope in the presence and the absence of laser irradiation. Results were analyzed statistically using one-way variance (ANOVA) analysis with Bonferroni post-Hoc multiple two-group comparisons. The characterization results ensured the successful synthesis of Withania Somnifera/Chitosan nanocomposites. The results showed an increase in the cytotoxicity against colon carcinoma and a decrease in cell viability in the presence and absence of Near-infrared laser irradiation under the action of nanocomposites. The cytotoxicity of the synthesized nanocomposites increased by exposing the cells to the laser. The shining light of the nanocomposites appeared on the cells photographed under the inverted microscope. The synthesized natural nanocomposites promise systemic cytotoxicity will be efficient in molecular imaging in vivo applications.

Protein-like particles through nanoprecipitation of mixtures of polymers of opposite charge

HYPOTHESIS

Polymer nanoparticles (NPs) have a very high potential for applications notably in the biomedical field. However, synthetic polymer NPs cannot yet concurrence the functionalities of proteins, their natural counterparts, notably in terms of size, control over internal structure and interactions with biological environments. We hypothesize that kinetic trapping of polymers bearing oppositely charged groups in NPs could bring a new level of control and allow mimicking the surfaces of proteins.

EXPERIMENTS

Here, the assembly of mixed-charge polymer NPs through nanoprecipitation of mixtures of oppositely charged polymers is studied. Two series of copolymers made of ethyl methacrylate and 1 to 25 mol% of either methacrylic acid or a trimethylammonium bearing methacrylate are synthesized. These carboxylic acid or trimethylammonium bearing polymers are then mixed in different ratios and nanoprecipitated. The influence of the charge fraction, mixing ratio of the polymers, and precipitation conditions on NP size and surface charge is studied.

FINDINGS

Using this approach, NPs of less than 25 nm with tunable surface charge from +40 mV to -40 mV are assembled. The resulting NPs are sensitive to pH and certain NP formulations have an isoelectric point allowing repeated charge reversal. Encapsulation of fluorescent dyes yields very bright fluorescent NPs, whose interactions with cells are studied through fluorescence microscopy. The obtained results show the potential of nanoprecipitation of oppositely charged polymers for the design of NPs with precisely tuned surface properties.

Subcellular imaging and diagnosis of cancer using engineered nanoparticles

The advances in the synthesis of nanoparticles with engineered properties are reported to have profound applications in oncological disease detection via optical and multimodal imaging and therapy. Among various nanoparticle-assisted imaging techniques, engineered fluorescent nanoparticles show great promise from high contrast images and localized therapeutic applications. Of all the fluorescent nanoparticles available, the gold nanoparticles, carbon dots, and upconversion nanoparticles are emerging recently as the most promising candidates for diagnosis, treatment, and cancer monitoring. This review addresses the recent progress in engineering the properties of these emerging nanoparticles and their application for cancer diagnosis and therapy. In addition, the potential of these particles for subcellular imaging is also reviewed here.

Organic J-Aggregate Nanodots with Enhanced Light Absorption and Near-Unity Fluorescence Quantum Yield

Development of biocompatible fluorophores with small size, bright fluorescence, and narrow spectrum translate directly into major advances in fluorescence imaging and related techniques. Here, we discover that a small donor-acceptor-donor-type organic molecule consisting of a carbazole (Cz) donor and benzothiazole (BT) acceptor (CzBTCz) assembles into quasi-crystalline J-aggregates upon a formation of ultrasmall nanoparticles. The 3.5 nm CzBTCz Jdots show a narrow absorption spectrum (fwhm = 27 nm), near-unity fluorescence quantum yield (ϕ_fl = 0.95), and enhanced peak molar extinction coefficient. The superior spectroscopic characteristics of the CzBTCz Jdots result in two orders of magnitude brighter photoluminescence of the Jdots compared with semiconductor quantum dots, which enables continuous single-Jdots imaging over a 1 h period. Comparison with structurally similar CzBT nanoparticles demonstrates a critical role played by the shape of CzBTCz on the formation of the Jdots. Our findings open an avenue for the development of a new class of fluorescent nanoparticles based on J-aggregates.

Light-Interacting iron-based nanomaterials for localized cancer detection and treatment

To improve the prognosis of cancer patients, methods of local cancer detection and treatment could be implemented. For that, iron-based nanomaterials (IBN) are particularly well-suited due to their biocompatibility and the various ways in which they can specifically target a tumor, i.e. through passive, active or magnetic targeting. Furthermore, when it is needed, IBN can be associated with well-known fluorescent compounds, such as dyes, clinically approved ICG, fluorescent proteins, or quantum dots. They may also be excited and detected using well-established optical methods, relying on scattering or fluorescent mechanisms, depending on whether IBN are associated with a fluorescent compound or not. Systems combining IBN with optical methods are diverse, thus enabling tumor detection in various ways. In addition, these systems provide a wealth of information, which is inaccessible with more standard diagnostic tools, such as single tumor cell detection, in particular by combining IBN with near-field scanning optical microscopy, dark-field microscopy, confocal microscopy or super-resolution microscopy, or the highlighting of certain dynamic phenomena such as the diffusion of a fluorescent compound in an organism, e.g. using fluorescence lifetime imaging, fluorescence resonance energy transfer, fluorescence anisotropy, or fluorescence tomography. Furthermore, they can in some cases be complemented by a therapeutic approach to destroy tumors, e.g. when the fluorescent compound is a drug, or when a technique such as photo-thermal or photodynamic therapy is employed. This review brings forward the idea that iron-based nanomaterials may be associated with various optical techniques to form a commercially available toolbox, which can serve to locally detect or treat cancer with a better efficacy than more standard medical approaches. STATEMENT OF SIGNIFICANCE: New tools should be developed to improve cancer treatment outcome. For that, two closely-related aspects deserve to be considered, i.e. early tumor detection and local tumor treatment. Here, I present various types of iron-based nanomaterials, which can achieve this double objective when they interact with a beam of light under specific and accurately chosen conditions. Indeed, these materials are biocompatible and can be used/combined with most standard microscopic/optical methods. Thus, these systems enable on the one hand tumor cell detection with a high sensitivity, i.e. down to single tumor cell level, and on the other hand tumor destruction through various mechanisms in a controlled and localized manner by deciding whether or not to apply a beam of light and by having these nanomaterials specifically target tumor cells.

Electron spectroscopies of 3-hydroxyflavone and 7-hydroxyflavone in MCM-41 silica nanoparticles and in acetonitrile solutions. Experimental data and DFT/TD-DFT calculations

The data presented here concern the photophysical characterization of luminescent MCM-41 nanoparticles doped with 3-hydroxyflavone and 7-hydroxyflavone, two fluorescent flavonoids. UV-Vis and fluorescence spectra obtained on freshly-prepared samples and aged (2 months exposed to air) samples are shown. The effect of light exposure is also studied. In parallel, experiments have been carried out in acetonitrile solutions of the two flavonoids as a term of comparison. Time-dependent density functional theory calculations have also been used to simulate UV-Vis and emission spectra of different species for both flavonoids (neutral molecule, tautomers, cationic and anionic forms), taking into account the effect of the surrounding medium (solvent). Density functional theory calculations of vibrational spectra (IR, Raman) of neutral and tautomeric species of 3HF and 7HF are also provided.

Development and application of photoconversion fluoropolymer films for greenhouses located at high or polar latitudes

To convert and store energy in the process of photosynthesis, plants primarily use quanta of the red and blue parts of the spectrum. At high latitudes, the average daily intensity of red and blue parts of the spectrum is not very high; for many crops cultivated under greenhouse conditions, it reaches the sufficient level only on clear summer days. The problem of insufficient illumination in greenhouses is usually solved with artificial light sources. This article describes a technology for the manufacture of photoconversion fluoropolymer films for greenhouses. The fluoropolymer films described in the paper make use of original gold nanoparticles and nanoparticles with fluorescence in the blue or red region of the spectrum. In the polymer film, nanoparticles aggregate in the form of "beads", which enhances the field of the optical wave. The film photoconverts UV and violet light into blue and red light. Gold nanoparticles also partially convert energy in the green region of the spectrum (not used by plants) into heat, which is also important for agriculture at high latitudes. In addition, impregnation of gold nanoparticles into fluoropolymer significantly increases the lifetime of the film. The films described in the paper can significantly increase the productivity of greenhouses located at high latitudes. Plants cultivated under the films have more chlorophyll and a higher intensity of photosynthesis - although their system of distance stress signals is, to a certain degree, suppressed.

vB_EcoS_NBD2 bacteriophage-originated polytubes as a carrier for the presentation of foreign sequences

Virus-based nanoparticles constitute a promising platform for the creation of efficient vaccines and nanomaterials. Previously we demonstrated, that the recombinant tail tube protein gp39 of vB_EcoS_NBD2 bacteriophage self-assembles into extremely long (from 0.1 to >3.95 μm), flexible, and stable polytubes when produced in Saccharomyces cerevisiae. To develop a tubular platform for multivalent display of foreign antigens, yeast-derived recombinant tail tube protein gp39 was chosen as a scaffold. The carboxy-terminal fusions of gp39 with various antigens up to 238 amino acids in length resulted in different synthesis efficiency and self-assembly capacity. Recombinant gp39 fused with green fluorescent protein (eGFP) comprising 238 amino acid residues was capable to self-assemble into short fluorescent polytubes with retained eGFP functional activity. By demonstrating the display of active foreign antigens on the exterior surface of polytubes, these structures may provide a promising tool for diverse applications in nanotechnology.

Nanomedicine and Early Cancer Diagnosis: Molecular Imaging using Fluorescence Nanoparticles

Incorporating nanotechnology into fluorescent imaging and magnetic resonance imaging (MRI) has shown promising potential for accurate diagnosis of cancer at an earlier stage than the conventional imaging modalities. Molecular imaging (MI) aims to quantitatively characterize, visualize, and measure the biological processes or living cells at molecular and genetic levels. MI modalities have been exploited in different applications including noninvasive determination and visualization of diseased tissues, cell trafficking visualization, early detection, treatment response monitoring, and in vivo visualization of living cells. High-affinity molecular probe and imaging modality to detect the probe are the two main requirements of MI. Recent advances in nanotechnology and allied modalities have facilitated the use of nanoparticles (NPs) as MI probes. Within the extensive group of NPs, fluorescent NPs play a prominent role in optical molecular imaging. The fluorescent NPs used in molecular and cellular imaging can be categorized into three main groups including quantum dots (QDs), upconversion, and dyedoped NPs. Fluorescent NPs have great potential in targeted theranostics including cancer imaging, immunoassay- based cells, proteins and bacteria detections, imaging-guided surgery, and therapy. Fluorescent NPs have shown promising potentials for drug and gene delivery, detection of the chromosomal abnormalities, labeling of DNA, and visualizing DNA replication dynamics. Multifunctional NPs have been successfully used in a single theranostic modality integrating diagnosis and therapy. The unique characteristics of multifunctional NPs make them potential theranostic agents that can be utilized concurrently for diagnosis and therapy. This review provides the state of the art of the applications of nanotechnologies in early cancer diagnosis focusing on fluorescent NPs, their synthesis methods, and perspectives in clinical theranostics.

Fluorescent nanoparticles with ultralow chromophore loading for long-term tumor-targeted imaging

Recently, organic dyes with aggregation-induced emission (AIE) have attracted much attention in bioimaging and diagnostics. Relatively, the application of traditional dyes has diminished because of aggregation-caused quenching (ACQ). In this work, we compare the imaging ability of nanoparticle formulations of these two kinds of dyes. Boron dipyrromethene (BODIPY) was chosen as a representative of the ACQ dyes, and an aggregation-induced emission (AIE) dye BPMT was used for comparison. BODIPY and BPMT were entrapped into PEG_5k-PLA_10k to form BODIPY-loaded NPs (BNPs) and BPMT-loaded NPs (ANPs), respectively. In vivo and ex vivo imaging demonstrated that BNP1 with ultralow BODIPY load (0.07%) can effectively accumulate in tumor tissues and enable long-term noninvasive imaging. In contrast, ANP4 with high BPMT load (1.6%) has poor bioimaging ability. In general, our work has certain reference significance for the application of ACQ dyes and AIEgens in bioimaging, diagnostics, and theranostics. STATEMENT OF SIGNIFICANCE: In this work, Boron dipyrromethene (BODIPY) was chosen as a representative of ACQ dyes. As a control, (Z)-2-(4'-(9H-carbazol-9-yl)-[1,1'-biphenyl]-4-yl)-3-(7-(4-(bis(4methoxyphenyl)amino) phenyl) benzo[c] [1,2,5] thiadiazol-4-yl) acrylonitrile (BPMT) was selected as an aggregation-induced emission (AIE) dye. BODIPY and BPMT was entrapped into PEG5k-PLA10k to form BODIPY-loaded NPs (BNPs) and BPMT-loaded NPs (ANPs), respectively. In vivo and ex vivo imaging demonstrated that BNP1 with ultralow BODIPY load (0.07%) can effectively accumulate in tumor tissues and realize long-term noninvasive imaging. The weaknesses of ACQ effect can be converted into advantages by skillful use of nanotechnology, which can not only save the cost but also realize high efficiency targeted cancer imaging.

Dual-functional supramolecular nanohybrids of quantum dot/biopolymer/chemotherapeutic drug for bioimaging and killing brain cancer cells in vitro

Glioblastoma (GBM) is the utmost aggressive and lethal primary brain cancer, which has a poor prognosis and remains virtually incurable. Nanomedicine with emerging disruptive nanotechnology alternatives, including designed supramolecular nanohybrids has excellent potential as multimodal tools against cancer by combining nanomaterials, biomacromolecules, and drugs. Thus, we developed and constructed for the first time quantum dot-biopolymer-drug nanohybrids based on host-guest chemistry for simultaneous bioimaging, targeting, and anti-cancer drug delivery against GBM cells in vitro. ZnS fluorescent quantum dots (ZnS-QDs) were produced using chemically modified polysaccharide, carboxymethylcellulose (CMC), as water-soluble capping ligand and biofunctional layer via a facile one-step eco-friendly aqueous colloidal process at room temperature and physiological pH. These hybrid inorganic-organic nanocolloids (ZnS@CMC) were electrostatically conjugated with doxorubicin (DOX) anti-cancer drug forming innovative supramolecular complexes (ZnS@CMC-DOX) for amalgamating bioimaging and killing cancer cells. These nanoconjugates were characterized regarding their optical and physicochemical properties combined with morphological and structural features. The cytocompatibility was evaluated by MTT assay using healthy and GBM cells. The results showed that ultra-small ZnS-QDs were expertly produced uniform nanocolloids (average size = 3.6 nm). They demonstrated photoluminescence emission within the visible range of spectra. The cell viability results in vitro showed no cytotoxicity of ZnS@CMC nanohybrids towards both cell types. In summary, the novelty of this research relies on using a nanotheranostic strategy for developing ZnS@CMC-DOX nanohybrids with supramolecular vesicle-like structures. They behaved simultaneously as active fluorescent nanoprobes and nanocarriers with modulated drug release for bioimaging and killing malignant glioma cells proving the high potential for applications in cancer nanomedicine.

Fluorescent Carbon Dots from Nerium oleander: Effects of Physical Conditions and the Extract Types

In this original research, the synthesis of carbon nanodots (CDs) from two different solvent extracts of Nerium oleander by the thermal method was investigated under various physical conditions such as pH, reaction temperature, ionic strength, and surface passivation agent (polyethylene glycol, PEG) presence in the reaction media. The effects of extract types and physical conditions on CDs formation were characterized by UV-Visible spectrophotometry, fluorescence spectrophotometry, Fourier transform infrared spectroscopy and dynamic light scattering analysis. Fluorescent CDs were obtained from PEG included reaction media. Additionally, the enhanced fluorescence intensity correlated with ascending reaction temperature was reported. The hydrodynamic particle size of CDs in aqueous solution was determined between ~1 and 235 nm with negative surface potential in the range of -6 mV and -28 mV. Moreover, CDs synthesized from aqueous extract mostly resulted in smaller size than that of ethanol extract based ones. The impact of surface passivation with PEG on the fluorescence feature of CDs was verified. For the relevant extracts of Oleander, CDs synthesized from PEG included formulations at pH 5 and NaCl free reaction media found as better alternatives than CDs synthesized under other conditions taking account their effect on fluorescence feature, hydrodynamic size and etc. Graphical Abstract.

Long-term live cells observation of internalized fluorescent Fe@C nanoparticles in constant magnetic field

BACKGROUND

Theranostics application of superparamagnetic nanoparticles based on magnetite and maghemite is impeded by their toxicity. The use of additional protective shells significantly reduced the magnetic properties of the nanoparticles. Therefore, iron carbides and pure iron nanoparticles coated with multiple layers of onion-like carbon sheath seem to be optimal for biomedicine. Fluorescent markers associated with magnetic nanoparticles provide reliable means for their multimodal visualization. Here, biocompatibility of iron nanoparticles coated with graphite-like shell and labeled with Alexa 647 fluorescent marker has been investigated.

METHODS

Iron core nanoparticles with intact carbon shells were purified by magnetoseparation after hydrochloric acid treatment. The structure of the NPs (nanoparticles) was examined with a high resolution electron microscopy. The surface of the NPs was alkylcarboxylated and further aminated for covalent linking with Alexa Fluor 647 fluorochrome to produce modified fluorescent magnetic nanoparticles (MFMNPs). Live fluorescent imaging and correlative light-electron microscopy were used to study the NPs intracellular distribution and the effects of constant magnetic field on internalized NPs in the cell culture were analyzed. Cell viability was assayed by measuring a proliferative pool with Click-IT labeling.

RESULTS

The microstructure and magnetic properties of superparamagnetic Fe@C core-shell NPs as well as their endocytosis by living tumor cells, and behavior inside the cells in constant magnetic field (150 mT) were studied. Correlative light-electron microscopy demonstrated that NPs retained their microstructure after internalization by the living cells. Application of constant magnetic field caused orientation of internalized NPs along power lines thus demonstrating their magnetocontrollability. Carbon onion-like shells make these NPs biocompatible and enable long-term observation with confocal microscope. It was found that iron core of NPs shows no toxic effect on the cell physiology, does not inhibit the cell proliferation and also does not induce apoptosis.

CONCLUSIONS

Non-toxic, biologically compatible superparamagnetic fluorescent MFMNPs can be further used for biological application such as delivery of biologically active compounds both inside the cell and inside the whole organism, magnetic separation, and magnetic resonance imaging (MRI) diagnostics.

A paper-based competitive lateral flow immunoassay for multi β-agonist residues by using a single monoclonal antibody labelled with red fluorescent nanoparticles

An ultrasensitive paper based lateral flow assay is described for rapid and simultaneous fluorometric detection of several β-agonists including clenbuterol and its chemical analogues (mabuterol, brombuterol, cimaterol, cimbuterol, bromchlorbuterol and banbuterol). A nonspecific monoclonal antibody (mAb) against clenbuterol and its analogues was prepared and employed in a competitive immunoassay where mAb conjugated to fluorescent nanoparticles and free β-agonists compete for the binding sites. This enables rapid screening for the 7 β-agonists in a single run that takes about 8 min. Detection limits for the seven β-agonists are <50 pg g⁻¹ of pork. Recoveries ranged from 69.5% to 102.4%, and relative standard deviations were ±15%. The assay was applied to the analysis of both using spiked and unspiked pork for β-agonists, and the results compare well to those obtained by HPLC-MS.

Graphical abstract

Aptamer Combined with Fluorescent Silica Nanoparticles for Detection of Hepatoma Cells

PURPOSE

The purpose of this study is to develop a simple, effective method to label hepatoma cells with aptamers and then detect them using fluorescent silica nanoparticles (FSNPs).

METHOD

Streptavidin was conjugated to carboxyl-modified fluorescein isothiocyanate (FITC)-doped silica nanoparticles which were prepared by the reverse microemulsion method. The resulting streptavidin-conjugated fluorescent silica nanoparticles (SA-FSNPs) were mixed with hepatoma cells that had been labeled with biotin-conjugated aptamer TLS11a (Bio-TLS11a). The specificity and sensitivity of the nanoprobes were assessed using flow cytometry and fluorescence microscopy. Their toxicity was assessed in normal human liver cell cultures using the MTT assay, as well as in nude mice using immunohistochemistry.

RESULTS

SA-FSNPs showed uniform size and shape, and fluorescence properties of them was similar to the free FITC dye. SA-FSNPs were able to detect aptamer-labeled hepatoma cells with excellent specificity and good sensitivity, and they emitted strong, photobleach-resistant fluorescent signal. SA-FSNPs showed no significant toxic effects in vitro or in vivo.

CONCLUSION

The combination of biotin-conjugated aptamers and SA-FSNPs shows promise for sensitive detection of hepatoma cells, and potentially of other tumor cell types as well.

Construction of protein-functionalized virus-like particles of parvovirus B19

Decoration of virus-like particles (VLPs) expands the repertory of functions these particles can display. In the last years, VLPs have successfully been used as scaffolds to present different molecules, frequently through the specific reaction of chemical groups on the surface of the particles, or by protein engineering when the presentation of peptides or proteins is the primary goal. VLPs of parvovirus B19 (B19V), have been previously produced in vitro and its stability and ability to assemble into hybrid particles composed of wild-type and chimeric proteins evidenced their potential as research tools. Herein, we report the presentation of functional proteins on the surface of B19V VLPs, through the fusion of the gene coding for the heterologous protein within the gene coding for the structural protein VP2. Two model proteins were used for the construction of chimeras, a lipase from Bacillus pumilus (BplA) and the enhanced green fluorescent protein (EGFP). Both chimeras were folded and successfully assembled in vitro into VLPs. While the BplA chimera exhibited esterase activity, the chimera of EGFP showed no fluorescence. We replaced the EGFP by its fast-folding derivative "super folder GFP" (sfGFP) flanked by larger linkers to increase its movement freedom, which resulted in fluorescent protein able to assemble fluorescent VLPs. These results expand the toolbox for VLP decoration as well as for the construction of new nanobiomaterials.

Covalently bound DNA on naked iron oxide nanoparticles: Intelligent colloidal nano-vector for cell transfection

BACKGROUND

Conversely to common coated iron oxide nanoparticles, novel naked surface active maghemite nanoparticles (SAMNs) can covalently bind DNA. Plasmid (pDNA) harboring the coding gene for GFP was directly chemisorbed onto SAMNs, leading to a novel DNA nanovector (SAMN@pDNA). The spontaneous internalization of SAMN@pDNA into cells was compared with an extensively studied fluorescent SAMN derivative (SAMN@RITC). Moreover, the transfection efficiency of SAMN@pDNA was evaluated and explained by computational model.

METHODS

SAMN@pDNA was prepared and characterized by spectroscopic and computational methods, and molecular dynamic simulation. The size and hydrodynamic properties of SAMN@pDNA and SAMN@RITC were studied by electron transmission microscopy, light scattering and zeta-potential. The two nanomaterials were tested by confocal scanning microscopy on equine peripheral blood-derived mesenchymal stem cells (ePB-MSCs) and GFP expression by SAMN@pDNA was determined.

RESULTS

Nanomaterials characterized by similar hydrodynamic properties were successfully internalized and stored into mesenchymal stem cells. Transfection by SAMN@pDNA occurred and GFP expression was higher than lipofectamine procedure, even in the absence of an external magnetic field. A computational model clarified that transfection efficiency can be ascribed to DNA availability inside cells.

CONCLUSIONS

Direct covalent binding of DNA on naked magnetic nanoparticles led to an extremely robust gene delivery tool. Hydrodynamic and chemical-physical properties of SAMN@pDNA were responsible of the successful uptake by cells and of the efficiency of GFP gene transfection.

GENERAL SIGNIFICANCE

SAMNs are characterized by colloidal stability, excellent cell uptake, persistence in the host cells, low toxicity and are proposed as novel intelligent DNA nanovectors for efficient cell transfection.

Biological synthesis of fluorescent nanoparticles by cadmium and tellurite resistant Antarctic bacteria: exploring novel natural nanofactories

Background

Fluorescent nanoparticles or quantum dots (QDs) have been intensely studied for basic and applied research due to their unique size-dependent properties. There is an increasing interest in developing ecofriendly methods to synthesize these nanoparticles since they improve biocompatibility and avoid the generation of toxic byproducts. The use of biological systems, particularly prokaryotes, has emerged as a promising alternative. Recent studies indicate that QDs biosynthesis is related to factors such as cellular redox status and antioxidant defenses. Based on this, the mixture of extreme conditions of Antarctica would allow the development of natural QDs producing bacteria.

Results

In this study we isolated and characterized cadmium and tellurite resistant Antarctic bacteria capable of synthesizing CdS and CdTe QDs when exposed to these oxidizing heavy metals. A time dependent change in fluorescence emission color, moving from green to red, was determined on bacterial cells exposed to metals. Biosynthesis was observed in cells grown at different temperatures and high metal concentrations. Electron microscopy analysis of treated cells revealed nanometric electron-dense elements and structures resembling membrane vesicles mostly associated to periplasmic space. Purified biosynthesized QDs displayed broad absorption and emission spectra characteristic of biogenic Cd nanoparticles.

Conclusions

Our work presents a novel and simple biological approach to produce QDs at room temperature by using heavy metal resistant Antarctic bacteria, highlighting the unique properties of these microorganisms as potent natural producers of nano-scale materials and promising candidates for bioremediation purposes.

Bioengineered quantum dot/chitosan-tripeptide nanoconjugates for targeting the receptors of cancer cells

Nanobiomaterials can be engineered to recognize cancer-specific receptors at the cellular level for diagnostic and therapeutic purposes. In this work, we report the synthesis of novel multifunctional nanoconjugates composed of fluorescent inorganic semiconductor quantum dot (QD) cores and tripeptide-modified polysaccharide organic shells. These structures were designed for targeting and imaging the αvβ3 integrin receptors of cancer cells. Initially, chitosan was covalently bound with the RGD peptide using a crosslinker to form bioconjugates (RGD-chitosan), which were later utilized as capping ligands for the production of surface-functionalized CdS QDs via a single-step process in aqueous media at room temperature. These core-shell nanostructures were extensively characterized by UV-vis spectroscopy, photoluminescence (PL) spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), zeta potential (ZP) and dynamic light scattering (DLS). The TEM images and the UV-vis absorption results indicated the formation of ultra-small CdS QD nanocrystals with average diameters between 2.0 and 3.0 nm. In addition, the PL results demonstrated that the nanobioconjugates exhibited intense green fluorescence under excitation. The CdS-RGD-chitosan systems were effective at specific targeting integrin when assayed in vitro using two model cell cultures, HEK 293 (non-cancerous human embryonic kidney cell) and SAOS (cancerous sarcoma osteogenic-derived cells) imaged using fluorescence microscopy.

Live fluorescent RNA-based detection of pluripotency gene expression in embryonic and induced pluripotent stem cells of different species

The generation of induced pluripotent stem (iPS) cells has successfully been achieved in many species. However, the identification of truly reprogrammed iPS cells still remains laborious and the detection of pluripotency markers requires fixation of cells in most cases. Here, we report an approach with nanoparticles carrying Cy3-labeled sense oligonucleotide reporter strands coupled to gold-particles. These molecules are directly added to cultured cells without any manipulation and gene expression is evaluated microscopically after overnight incubation. To simultaneously detect gene expression in different species, probe sequences were chosen according to interspecies homology. With a common target-specific probe we could successfully demonstrate expression of the GAPDH house-keeping gene in somatic cells and expression of the pluripotency markers NANOG and GDF3 in embryonic stem cells and iPS cells of murine, human, and porcine origin. The population of target gene positive cells could be purified by fluorescence-activated cell sorting. After lentiviral transduction of murine tail-tip fibroblasts Nanog-specific probes identified truly reprogrammed murine iPS cells in situ during development based on their Cy3-fluorescence. The intensity of Nanog-specific fluorescence correlated positively with an increased capacity of individual clones to differentiate into cells of all three germ layers. Our approach offers a universal tool to detect intracellular gene expression directly in live cells of any desired origin without the need for manipulation, thus allowing conservation of the genetic background of the target cell. Furthermore, it represents an easy, scalable method for efficient screening of pluripotency which is highly desirable during high-throughput cell reprogramming and after genomic editing of pluripotent stem cells.

Live fluorescent RNA-based detection of pluripotency gene expression in embryonic and induced pluripotent stem cells of different species

The generation of induced pluripotent stem (iPS) cells has successfully been achieved in many species. However, the identification of truly reprogrammed iPS cells still remains laborious and the detection of pluripotency markers requires fixation of cells in most cases. Here, we report an approach with nanoparticles carrying Cy3-labeled sense oligonucleotide reporter strands coupled to gold-particles. These molecules are directly added to cultured cells without any manipulation and gene expression is evaluated microscopically after overnight incubation. To simultaneously detect gene expression in different species, probe sequences were chosen according to interspecies homology. With a common target-specific probe we could successfully demonstrate expression of the GAPDH house-keeping gene in somatic cells and expression of the pluripotency markers NANOG and GDF3 in embryonic stem cells and iPS cells of murine, human, and porcine origin. The population of target gene positive cells could be purified by fluorescence-activated cell sorting. After lentiviral transduction of murine tail-tip fibroblasts Nanog-specific probes identified truly reprogrammed murine iPS cells in situ during development based on their Cy3-fluorescence. The intensity of Nanog-specific fluorescence correlated positively with an increased capacity of individual clones to differentiate into cells of all three germ layers. Our approach offers a universal tool to detect intracellular gene expression directly in live cells of any desired origin without the need for manipulation, thus allowing conservation of the genetic background of the target cell. Furthermore, it represents an easy, scalable method for efficient screening of pluripotency which is highly desirable during high-throughput cell reprogramming and after genomic editing of pluripotent stem cells.

Indirect immunofluorescence detection of E. coli O157:H7 with fluorescent silica nanoparticles

A method of fluorescent nanoparticle-based indirect immunofluorescence assay using either fluorescence microscopy or flow cytometry for the rapid detection of pathogenic Escherichia coli O157:H7 was developed. The dye-doped silica nanoparticles (NPs) were synthesized using W/O microemulsion methods with the combination of 3-aminopropyltriethoxysilane (APTES) and fluorescein isothiocyanate (FITC) and polymerization reaction with carboxyethylsilanetriol sodium salt (CEOS). Protein A was immobilized at the surface of the NPs by covalent binding to the carboxyl linkers and the surface coverage of Protein A on NPs was determined by the Bradford method. Rabbit anti-E. Coli O157:H7 antibody was used as primary antibody to recognize E. coli O157:H7 and then antibody binding protein (Protein A) labeled with FITC-doped silica NPs (FSiNPs) was used to generate fluorescent signal. With this method, E. Coli O157:H7 in buffer and bacterial mixture was detected. In addition, E. coli O157:H7 in several spiked background beef samples were measured with satisfactory results. Therefore, the FSiNPs are applicable in signal-amplified bioassay of pathogens due to their excellent capabilities such as brighter fluorescence and higher photostability than the direct use of conventional fluorescent dyes.

Trypsinization-dependent cell labeling with fluorescent nanoparticles

Trypsin is often used to detach adhered cell subculture from a substrate. However, the proteolytic activity of trypsin may harm cells by cleaving the cell membrane proteins. The present study shows that cellular uptake of fluorescent nanoparticles is remarkably increased within 24 h after trypsinization. These results highlight the trypsin-induced protein digestion, provoking leaky cell plasma membrane which leads to the strongly enhanced cellular uptake of the nanoparticles. To prevent this effect, one should expose cells to the nanoparticle (NP)-based fluorescent labels at least 48 h after trypsinization.

Polymer-coated fluorescent CdSe-based quantum dots for application in immunoassay

The paper describes all stages of synthesis and characterization of biocompatible CdSe-based core/shell quantum dots (QDs) and their application as fluorescent label for immunoassay. Special attention was focused on development of maleic anhydride-based amphiphilic polymers for QDs solubilization in aqueous media. In this work two PEG-amines were tried for polymer modification: monoamine Jeffamine M 1000 used previously in some researches and diamine Jeffamine ED-2003 applied for the first time for QDs solubilization. The use of different Jeffamines allows us to obtain QDs with carboxyl or amine functional groups available for conjugation. The influence of polymer composition on optical properties of the nanocrystals and their stability in aqueous solutions as well as on their conjugation with biomolecules was studied. QDs with different coatings were used as biolabels in quantitative fluorescence microtiter plate immunoassay and qualitative on-site column test. It was found that quantum dots covered with amphiphilic polymer prepared from poly(maleic anhydride-alt-1-octadecene) and Jeffamine ED-2003 retained up to 90% of their initial brightness, easily conjugated with protein and showed low non-specific adsorption. In optimized conditions the obtained QDs were successfully used for determination of mycotoxin deoxynivalenol in wheat and maize samples by fluorescence microtiter plate immunoassay with an IC50 of 220 μg kg(-1) and by on-site column test with cut-off of 500 μg kg(-1).