Labelling of cells with quantum dots

Aqueous synthesized quantum dots interfere with the NF-κB pathway and confer anti-tumor, anti-viral and anti-inflammatory effects

The NF-κB pathway plays crucial roles in inflammatory responses and cell survival. Aberrant constitutive NF-κB activation is associated with various human diseases including cancer and inflammatory and auto-immune diseases. Consequently, it is highly desirable to develop new kinds of inhibitors, which are highly efficacious for blocking the NF-κB pathway. In this study, by using a typical kind of aqueous synthesized quantum dots (QDs), i.e., CdTe QDs, as a model, we for the first time demonstrated that the QDs could selectively affect the cellular nuclear factor-κB (NF-κB) signaling pathway, but do not affect the AKT or ERK pathways. Typically, the QDs efficiently inhibited the activation of IKKα and IKKβ, resulting in the suppression of both the canonical and the non-canonical NF-κB signaling pathways. Inhibition of NF-κB by QDs downregulates anti-apoptotic genes and promotes apoptosis in cancer cells. The QDs induced NF-κB inhibition and cytotoxicity could be blocked by N-acetylcysteine due to the reduced cellular uptake of QDs. Importantly, inhibition of NF-κB by QDs displayed promising effects against the viral replication and in vivo bacterial endotoxin-induced inflammatory responses. These data suggest the QDs as potent inhibitors of the NF-κB signaling pathway, both in vitro and in vivo. Our findings highlight the potential of using QDs in the development of anti-cancer, anti-viral, and anti-inflammatory approaches, and also facilitate better understanding of QDs-related cellular behavior under the molecular level.

Toxicological impact of cadmium-based quantum dots towards aquatic biota: Effect of natural sunlight exposure

Cadmium-based quantum dots (QDs) are increasingly applied in existent and emerging technologies, especially in biological applications due to their exceptional photophysical and functionalization properties. However, they are very toxic compounds due to the high reactive and toxic cadmium core. The present study aimed to determine the toxicity of three different QDs (CdS 380, CdS 480 and CdSeS/ZnS) before and after the exposure of suspensions to sunlight, in order to assess the effect of environmentally relevant irradiation levels in their toxicity, which will act after their release to the environment. Therefore, a battery of ecotoxicological tests was performed with organisms that cover different functional and trophic levels, such as Vibrio fischeri, Raphidocelis subcapitata, Chlorella vulgaris and Daphnia magna. The results showed that core-shell type QDs showed lower toxic effects to V. fischeri in comparison to core type QDs before sunlight exposure. However, after sunlight exposure, there was a decrease of CdS 380 and CdS 480 QD toxicity to bacterium. Also, after sunlight exposure, an effective decrease of CdSeS/ZnS and CdS 480 toxicity for D. magna and R. subcapitata, and an evident increase in CdS 380 QD toxicity, at least for D. magna, were observed. The results of this study suggest that sunlight exposure has an effect in the aggregation and precipitation reactions of larger QDs, causing the degradation of functional groups and formation of larger bulks which may be less prone to photo-oxidation due to their diminished surface area. The same aggregation behaviour after sunlight exposure was observed for bare QDs. These results further emphasize that the shell of QDs seems to make them less harmful to aquatic biota, both under standard environmental conditions and after the exposure to a relevant abiotic factor like sunlight.

Metal-based quantum dots: synthesis, surface modification, transport and fate in aquatic environments and toxicity to microorganisms

The intense interest in metal-based QDs is diluted by the fact that they cause risks to aquatic environments.

Fabrication of highly photoluminescent quantum dot-polymer composite micropatterned surface using thiol-ene chemistry

The fabrication of a micropatterned QD composite with superior PL properties in that the presence of a positive charge on the QDs enhances the dispersion interaction between the QDs, and the allylic group enables the QDs to form strong chemical binding to the polymer matrix.

A hydrothermal reaction of an aqueous solution of BSA yields highly fluorescent N doped C-dots used for imaging of live mammalian cells

In the current study, we present a new and facile synthesis of N doped C-dots (N@C-dots) by hydrothermally reacting an aqueous solution of Bovine Serum Albumin (BSA) for imaging of live mammalian cells.

Highly luminescent and photostable near-infrared fluorescent polymer dots for long-term tumor cell tracking in vivo

Near-infrared-emitting polymer dots were prepared and used as fluorescent nanoprobes for in vitro HeLa cell labeling and in vivo long-term HeLa tumor tracking. The prepared NIR polymer dots showed no obvious effect on the tumor growth, and exhibited durable brightness, long-term photostability and high sensitivity.

Random Lasing with Systematic Threshold Behavior in Films of CdSe/CdS Core/Thick-Shell Colloidal Quantum Dots

While over the past years the syntheses of colloidal quantum dots (CQDs) with core/shell structures were continuously improved to obtain highly efficient emission, it has remained a challenge to use them as active materials in laser devices. Here, we report random lasing at room temperature in films of CdSe/CdS CQDs with different core/shell band alignments and extra thick shells. Even though the lasing process is based on random scattering, we find systematic dependencies of the laser thresholds on morphology and laser spot size. To minimize laser thresholds, optimizing the film-forming properties of the CQDs, proven by small-angle X-ray scattering, was found to be more important than the optical parameters of the CQDs, such as biexciton lifetime and binding energy or fluorescence decay time. Furthermore, the observed systematic behavior turned out to be highly reproducible after storing the samples in air for more than 1 year. These highly reproducible systematic dependencies suggest that random lasing experiments are a valuable tool for testing nanocrystal materials, providing a direct and simple feedback for further development of colloidal gain materials toward lasing in continuous wave operation.

Optical characterization of core-shell quantum dots embedded in synthetic saliva: Temporal dynamics

The present work reports the spectroscopic and thermo-optical properties of CdSe/ZnS and CdSe/CdS core-shell quantum dots (QDs) embedded in synthetic saliva. Spectroscopy studies were performed applying nonfunctionalized CdSe/ZnS QDs (3.4, 3.9 and 5.1 nm cores) and hydroxyl group-functionalized ultrasmall CdSe/CdS core-shell quantum dots (1.6 nm core) suspended in artificial saliva at different potential of hydrogen (pH) values. Saliva was chosen because it is important in a variety of functions such as protecting teeth through the buffering capacity of the formed biofilm, hydration, and dental remineralization. Thermo-optical characterizations using the thermal lens (TL) technique were performed in QD-biofluids for different QD sizes and pH values (3.9-8.3) of the synthetic oral fluids. Transient TL measurements were applied to determine the fluorescence quantum efficiency (η) in QD-biomaterial systems. High η value was obtained for ultrasmall CdSe/CdS QDs. Fluorescence spectral measurements of the biomaterials support the TL results. In addition, for nonfunctionalized (3.4 and 5.1 nm) and hydroxyl group-functionalized QDs, the temporal behavior of the fluorescence spectra was accomplished about approximately 1200 h at two different biofluid pH values (3.9 and 8.3). The temporal fluorescence intensity result is dependent on the pH of the saliva in which the QDs were embedded, QD functionalization and QD sizes. The time for an approximately 50% decrease in the peak intensity fluorescence of CdSe/ZnS QDs (3.4 nm core) and ultrasmall CdSe/CdS QDs is respectively 25 h and 312 h at pH 3.9 and 48 h and 360 h at pH 8.3.

Quantum dots and ionic liquid-sensitized effect as an efficient and green catalyst for the sensitive determination of glucose

A novel fluorescence (FL) method using water-soluble CdSe quantum dots (QDs) is proposed for the fluorometric determination of hydrogen peroxide and glucose. Water-soluble CdSe QDs were synthesized by using thioglycolic acid as stabilizer in aqueous solutions. The nanoparticles were structurally and optically characterized by X-ray powder diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), UV-Vis absorption spectroscopy, photoluminescence (PL) emission spectroscopy and transmission electron microscope (TEM). Ionic liquid-sensitized effect in aqueous solution was then investigated. In the presence of ionic liquid as catalyst, H2O2 was decomposed into radical that could quench the fluorescence of CdSe QDs more efficiently and rapidly. Then the oxidization of glucose by glucose oxidase was coupled with the fluorescence quenching of CdSe QDs by H2O2 producer with ionic liquid catalyst, which can be used to detect glucose. Therefore, a new FL analysis system was developed for the determination of glucose. Under the optimum conditions, there is a good linear relationship between the relative PL emission intensity and the concentration of glucose in the range of 5.0×10(-7)-1.0×10(-4) M of glucose with a correlation coefficient (R(2)) of 0.9973. The limit of detection of this system was found to be 1.0×10(-7) M. This method is not only simple, sensitive and low cost, but also reliable for practical applications.

Plasmid transfection in mammalian cells spatiotemporally tracked by a gold nanoparticle

Recent advances in cell transfection have suggested that delivery of a gene on a gold nanoparticle (AuNP) can enhance transfection efficiency. The mechanism of transfection is poorly understood, particularly when the gene is appended to a AuNP, as expression of the desired exogenous protein is dependent not only on the efficiency of the gene being taken into the cell but also on efficient endosomal escape and cellular processing of the nucleic acid. Design of a multicolor surface energy transfer (McSET) molecular beacon by independently dye labeling a linearized plasmid and short duplex DNA (sdDNA) appended to a AuNP allows spatiotemporal profiling of the transfection events, providing insight into package uptake, disassembly, and final plasmid expression. Delivery of the AuNP construct encapsulated in Lipofectamine2000 is monitored in Chinese hamster ovary cells using live-cell confocal microscopy. The McSET beacon signals the location and timing of the AuNP release and endosomal escape events for the plasmid and the sdDNA discretely, which are correlated with plasmid transcription by fluorescent protein expression within the cell. It is observed that delivery of the construct leads to endosomal release of the plasmid and sdDNA from the AuNP surface at different rates, prior to endosomal escape. Slow cytosolic diffusion of the nucleic acids is believed to be the limiting step for transfection, impacting the time-dependent expression of protein. The overall protein expression yield is enhanced when delivered on a AuNP, possibly due to better endosomal escape or lower degradation prior to endosomal escape.

Color-tunable luminescent CdTe quantum dot membranes based on bacterial cellulose (BC) and application in ion detection

Color-tunable luminescent membranes of CdTe QDs on bacterial cellulose (BC) nanofibers were successfully fabricated by in situ synthesis in aqueous solution.

Aqueous phase one-pot green synthesis of SnSe nanosheets in a protein matrix: negligible cytotoxicity and room temperature emission in the visible region

A rapid, facile, reproducible and green method for synthesizing SnSe nanosheets in aqueous media is reported. Cyclic voltammetry studies indicate better thermodynamic feasibility for reducing SnSe, while the nanomaterial is nontoxic up to a 100 μM concentration in CHO cells.

Nanoparticle vesicle encoding for imaging and tracking cell populations

For phenotypic behavior to be understood in the context of cell lineage and local environment, properties of individual cells must be measured relative to population-wide traits. However, the inability to accurately identify, track and measure thousands of single cells via high-throughput microscopy has impeded dynamic studies of cell populations. We demonstrate unique labeling of cells, driven by the heterogeneous random uptake of fluorescent nanoparticles of different emission colors. By sequentially exposing a cell population to different particles, we generated a large number of unique digital codes, which corresponded to the cell-specific number of nanoparticle-loaded vesicles and were visible within a given fluorescence channel. When three colors are used, the assay can self-generate over 17,000 individual codes identifiable using a typical fluorescence microscope. The color-codes provided immediate visualization of cell identity and allowed us to track human cells with a success rate of 78% across image frames separated by 8 h.

Fluorescence lifetime imaging microscopy in the medical sciences

The steady improvement in the imaging of cellular processes in living tissue over the last 10-15 years through the use of various fluorophores including organic dyes, fluorescent proteins and quantum dots, has made observing biological events common practice. Advances in imaging and recording technology have made it possible to exploit a fluorophore's fluorescence lifetime. The fluorescence lifetime is an intrinsic parameter that is unique for each fluorophore, and that is highly sensitive to its immediate environment and/or the photophysical coupling to other fluorophores by the phenomenon Förster resonance energy transfer (FRET). The fluorescence lifetime has become an important tool in the construction of optical bioassays for various cellular activities and reactions. The measurement of the fluorescence lifetime is possible in two formats; time domain or frequency domain, each with their own advantages. Fluorescence lifetime imaging applications have now progressed to a state where, besides their utility in cell biological research, they can be employed as clinical diagnostic tools. This review highlights the multitude of fluorophores, techniques and clinical applications that make use of fluorescence lifetime imaging microscopy (FLIM).

Use of CdTe quantum dots for high temperature thermal sensing

Thermal sensitive photoluminescence of CdTe quantum dots was used for micro-electromechanical systems temperature measurements in the high temperature range.

Silicon quantum dots for biological applications

Semiconductor nanoparticles (or quantum dots, QDs) exhibit unique optical and electronic properties such as size-controlled fluorescence, high quantum yields, and stability against photobleaching. These properties allow QDs to be used as optical labels for multiplexed imaging and in drug delivery detection systems. Luminescent silicon QDs and surface-modified silicon QDs have also been developed as potential minimally toxic fluorescent probes for bioapplications. Silicon, a well-known power electronic semiconductor material, is considered an extremely biocompatible material, in particular with respect to blood. This review article summarizes existing knowledge related to and recent research progress made in the methods for synthesizing silicon QDs, as well as their optical properties and surface-modification processes. In addition, drug delivery systems and in vitro and in vivo imaging applications that use silicon QDs are also discussed.

Amine-terminated nanoparticle films: pattern deposition by a simple nanostencilling technique and stability studies under X-ray irradiation

Exploring the surface chemistry of nanopatterned amine-terminated nanoparticle films.

Quantum dots for fluorescent biosensing and bio-imaging applications

Quantum dots (QDs) have been facilitating the development of sensitive fluorescence biosensors over the past two decades due to their high quantum yield, narrow and tunable emission spectrum and good photostability. The new emerging QDs with improved biocompatibility further promote their biological applications. In this review, we first briefly introduce the prevalently used QDs and their preparation and bioconjugation approaches. Then we summarize QDs-based fluorescent biosensing for proteins and nucleic acids, and QDs-based applications in cellular and in vivo targeting and imaging. Last but not the least, we envision the potential QDs-based applications in future perspectives.

Magnetic nanoparticles as mediators of ligand-free activation of EGFR signaling

BACKGROUND

Magnetic nanoparticles (NPs) are of particular interest in biomedical research, and have been exploited for molecular separation, gene/drug delivery, magnetic resonance imaging, and hyperthermic cancer therapy. In the case of cultured cells, magnetic manipulation of NPs provides the means for studying processes induced by mechanotransduction or by local clustering of targeted macromolecules, e.g. cell surface receptors. The latter are normally activated by binding of their natural ligands mediating key signaling pathways such as those associated with the epidermal growth factor (EGFR). However, it has been reported that EGFR may be dimerized and activated even in the absence of ligands. The present study assessed whether receptor clustering induced by physical means alone suffices for activating EGFR in quiescent cells.

METHODOLOGY/PRINCIPAL FINDINGS

The EGFR on A431 cells was specifically targeted by superparamagnetic iron oxide NPs (SPIONs) carrying either a ligand-blocking monoclonal anti-EGFR antibody or a streptavidin molecule for targeting a chimeric EGFR incorporating a biotinylated amino-terminal acyl carrier peptide moiety. Application of a magnetic field led to SPION magnetization and clustering, resulting in activation of the EGFR, a process manifested by auto and transphosphorylation and downstream signaling. The magnetically-induced early signaling events were similar to those inherent to the ligand dependent EGFR pathways. Magnetization studies indicated that the NPs exerted magnetic dipolar forces in the sub-piconewton range with clustering dependent on Brownian motion of the receptor-SPION complex and magnetic field strength.

CONCLUSIONS/SIGNIFICANCE

We demonstrate that EGFR on the cell surface that have their ligand binding-pocket blocked by an antibody are still capable of transphosphorylation and initiation of signaling cascades if they are clustered by SPIONs either attached locally or targeted to another site of the receptor ectodomain. The results suggest that activation of growth factor receptors may be triggered by ligand-independent molecular crowding resulting from overexpression and/or sequestration in membrane microdomains.

Nanotoxicology using the sea anemone Nematostella vectensis: from developmental toxicity to genotoxicology

Concomitant with the fast-growing advances in the synthesis and engineering of colloidal nanocrystals, an urgent evaluation of their toxicity on human beings and environment is strongly encouraged by public health organisations. Despite the in vitro approaches employed for toxicological screening of hazardous compounds, the use of simple and cost-effective living organisms may enormously contribute to solve unanswered questions related to embryotoxic and teratogenic effects of nanomaterials. Here, the sea anemone Nematostella vectensis (Cnidaria, Anthozoa) is presented as a novel model organism to profile bio/non-bio interactions and to show a comprehensive toxicological analysis performed on embryos, larvae and adults treated with fluorescent cadmium-based nanocrystals. Spanning from in vivo biodistribution to molecular investigations, different behaviours and effects depending on the composition and surface coatings are showed. Rod-shaped cadmium selenide/cadmium sulfide (CdSe/CdS) nanocrystals resulted in excellent imaging probes to track N. vectensis development with negligible adverse effects, while spherical CdTe nanocrystals severely impaired embryogenesis, resulting in aberrant phenotypes and deregulation of developmental genes, which raise severe worries for a safe use of this type of nanoparticles for human purposes and environmental contamination.

Temporal techniques: dynamic tracking of nanomaterials in live cells

Temporal analytical techniques to track nanoparticles in live cell would provide rich information to well understand the biologic properties of nanoparticles in molecular level. Significant advances in fluorescence microscopy techniques with high temporal and spatial resolution allow single nanoparticles to label biomolecules, ions, and microstructures in live cells, which will address many fundamental questions in cell biology. This review highlights the real time tracking techniques for monitoring the movement of nanomaterials such as carbon nanotubes (CNTs), quantum dots (QDs), metal clusters, upconver-sional nanomaterials, and polystyrene (PS) nanoparticles etc. in live cells. The biological properties of nanoparticles in live cells are also briefly summarized according to fluorescence microscopy studies.

An ultrasensitive electrochemiluminescence immunoassay for carbohydrate antigen 19-9 in serum based on antibody labeled Fe3O4 nanoparticles as capture probes and graphene/CdTe quantum dot bionanoconjugates as signal amplifiers

The CdTe quantum dots (QDs), graphene nanocomposite (CdTe-G) and dextran–Fe₃O₄ magnetic nanoparticles have been synthesized for developing an ultrasensitive electrochemiluminescence (ECL) immunoassay for Carcinoembryonic antigen 19-9 (CA 19-9) in serums. Firstly, the capture probes (CA 19-9 Ab1/Fe₃O₄) for enriching CA 19-9 were synthesized by immobilizing the CA 19-9’s first antibody (CA 19-9 Ab1) on magnetic nanoparticles (dextran-Fe₃O₄). Secondly, the signal probes (CA 19-9 Ab2/CdTe-G), which can emit an ECL signal, were formed by attaching the secondary CA 19-9 antibody (CA 19-9 Ab2) to the surface of the CdTe-G. Thirdly, the above two probes were used for conjugating with a serial of CA 19-9 concentrations. Graphene can immobilize dozens of CdTe QDs on their surface, which can emit stronger ECL intensity than CdTe QDs. Based on the amplified signal, ultrasensitive antigen detection can be realized. Under the optimal conditions, the ECL signal depended linearly on the logarithm of CA 19-9 concentration from 0.005 to 100 pg/mL, and the detection limit was 0.002 pg/mL. Finally, five samples of human serum were tested, and the results were compared with a time-resolved fluorescence assay (TRFA). The novel immunoassay provides a stable, specific and highly sensitive immunoassay protocol for tumor marker detection at very low levels, which can be applied in early diagnosis of tumor.

Quantum-dot-based photoelectrochemical sensors for chemical and biological detection

Quantum-dot-based photoelectrochemical sensors are powerful alternatives for the detection of chemicals and biochemical molecules compared to other sensor types, which is the primary reason as to why they have become a hot topic in nanotechnology-related analytical methods. These sensors basically consist of QDs immobilized by a linking molecule (linker) to an electrode, so that upon their illumination, a photocurrent is generated which depends on the type and concentration of the respective analyte in the immediate environment of the electrode. The present review provides an overview of recent developments in the fabrication methods and sensing concepts concerning direct and indirect interactions of the analyte with quantum dot modified electrodes. Furthermore, it describes in detail the broad range of different sensing applications of such quantum-dot-based photoelectrochemical sensors for inorganic and organic (small and macro-) molecules that have arisen in recent years. Finally, a number of aspects concerning current challenges on the way to achieving real-life applications of QD-based photochemical sensing are addressed.

Quantum dots in bioanalysis: a review of applications across various platforms for fluorescence spectroscopy and imaging

Semiconductor quantum dots (QDs) are brightly luminescent nanoparticles that have found numerous applications in bioanalysis and bioimaging. In this review, we highlight recent developments in these areas in the context of specific methods for fluorescence spectroscopy and imaging. Following a primer on the structure, properties, and biofunctionalization of QDs, we describe select examples of how QDs have been used in combination with steady-state or time-resolved spectroscopic techniques to develop a variety of assays, bioprobes, and biosensors that function via changes in QD photoluminescence intensity, polarization, or lifetime. Some special attention is paid to the use of Förster resonance energy transfer-type methods in bioanalysis, including those based on bioluminescence and chemiluminescence. Direct chemiluminescence, electrochemiluminescence, and charge transfer quenching are similarly discussed. We further describe the combination of QDs and flow cytometry, including traditional cellular analyses and spectrally encoded barcode-based assay technologies, before turning our attention to enhanced fluorescence techniques based on photonic crystals or plasmon coupling. Finally, we survey the use of QDs across different platforms for biological fluorescence imaging, including epifluorescence, confocal, and two-photon excitation microscopy; single particle tracking and fluorescence correlation spectroscopy; super-resolution imaging; near-field scanning optical microscopy; and fluorescence lifetime imaging microscopy. In each of the above-mentioned platforms, QDs provide the brightness needed for highly sensitive detection, the photostability needed for tracking dynamic processes, or the multiplexing capacity needed to elucidate complex systems. There is a clear synergy between advances in QD materials and spectroscopy and imaging techniques, as both must be applied in concert to achieve their full potential.

Intracellular distribution of nontargeted quantum dots after natural uptake and microinjection

Background:

The purpose of this study was to elucidate the mechanism of natural uptake of nonfunctionalized quantum dots in comparison with microinjected quantum dots by focusing on their time-dependent accumulation and intracellular localization in different cell lines.

Methods:

The accumulation dynamics of nontargeted CdSe/ZnS carboxyl-coated quantum dots (emission peak 625 nm) was analyzed in NIH3T3, MCF-7, and HepG2 cells by applying the methods of confocal and steady-state fluorescence spectroscopy. Intracellular colocalization of the quantum dots was investigated by staining with Lysotracker^®.

Results:

The uptake of quantum dots into cells was dramatically reduced at a low temperature (4°C), indicating that the process is energy-dependent. The uptake kinetics and imaging of intracellular localization of quantum dots revealed three accumulation stages of carboxyl-coated quantum dots at 37°C, ie, a plateau stage, growth stage, and a saturation stage, which comprised four morphological phases: adherence to the cell membrane; formation of granulated clusters spread throughout the cytoplasm; localization of granulated clusters in the perinuclear region; and formation of multivesicular body-like structures and their redistribution in the cytoplasm. Diverse quantum dots containing intracellular vesicles in the range of approximately 0.5–8 μm in diameter were observed in the cytoplasm, but none were found in the nucleus. Vesicles containing quantum dots formed multivesicular body-like structures in NIH3T3 cells after 24 hours of incubation, which were Lysotracker-negative in serum-free medium and Lysotracker-positive in complete medium. The microinjected quantum dots remained uniformly distributed in the cytosol for at least 24 hours.

Conclusion:

Natural uptake of quantum dots in cells occurs through three accumulation stages via a mechanism requiring energy. The sharp contrast of the intracellular distribution after microinjection of quantum dots in comparison with incubation as well as the limited transfer of quantum dots from vesicles into the cytosol and vice versa support the endocytotic origin of the natural uptake of quantum dots. Quantum dots with proteins adsorbed from the culture medium had a different fate in the final stage of accumulation from that of the protein-free quantum dots, implying different internalization pathways.

Individual inorganic nanoparticles: preparation, functionalization and in vitro biomedical diagnostic applications

Inorganic nanoparticles have become the focus of modern materials science due to their potential technological importance, particularly in bionanotechnology, which stems from their unique physical properties including size-dependent optical, magnetic, electronic, and catalytic properties. The present article provides an overview on the currently used individual inorganic nanoparticles for in vitro biomedical domains. These inorganic nanoparticles include iron oxides, gold, silver, silica, quantum dots (QDs) and second harmonic generation (SHG) particles. For each of these interesting nanoparticles, the main issues starting from preparation up to bio-related applications are presented.

Adsorption-desorption study of BSA conjugated silver nanoparticles (Ag/BSA NPs) on collagen immobilized substrates

There has been a growing interest in the use of protein conjugated nanoparticles for applications in biomedical, sensing, and advanced imaging. The objective of this study was to understand the interaction of protein conjugated silver nanoparticles (Ag/BSA NPs) with biological substrate (collagen layer). The adsorption behavior of synthesized Ag/BSA NPs on collagen immobilized silanized surface was followed by UV-vis spectroscopy by initially studying the formation of collagen layer and subsequent adsorption of Ag/BSA NPs to the immobilized layer. Surface plasmon resonance (SPR) data provided the real time profile of adsorption of Ag/BSA NPs from solution onto collagen immobilized and control substrates as well as desorption of nanoparticles from the substrates. The retention of NPs to substrate is sensitive to chemistry of the underlying substrate and on the external environment. UV-vis and atomic absorption spectrometric analysis of Ag/BSA NPs desorption performed under different pH conditions showed more NPs retained at physiological pH than the acidic and basic conditions. Nanoparticles retention on collagen immobilized substrate at physiological pH could influence properties of biological interest such as circulation lifetime and biodistribution of nanoparticles in the body.

Spectroscopic investigations of Fe3+ doped poly vinyl alcohol (PVA) capped ZnSe nanoparticles

Fe(3+) doped poly vinyl alcohol (PVA) capped ZnSe nanoparticles have been synthesized by using chemical method at room temperature. The prepared sample is characterized by X-ray diffraction, optical, photoluminescence (PL), electron paramagnetic resonance (EPR) and FT-IR techniques. Different physical parameters are evaluated by using measured values of refractive index and density. From the X-ray diffraction pattern, the average crystallite size is calculated by using Scherrer's formula and it is about 9 nm. Optical absorption spectrum reveals that the Fe(3+) ion enter into the lattice as octahedral symmetry. Crystal field (Dq) and inter-electronic repulsion parameters (B, C) are evaluated for Fe(3+) doped ZnSe nanoparticles as Dq=720, B=720 and C=2500 cm(-1). Photoluminescence spectrum of Fe(3+) doped ZnSe exhibits emission bands in UV and yellow regions. EPR spectrum showed various resonance signals at g=7.3, 3.5 and 2.0. FT-IR spectrum of Fe(3+) doped PVA capped ZnSe indicates the presence of O-H, C-H, C=C and C=O molecular groups.

Quantum dots-based immunofluorescent imaging of stromal fibroblasts Caveolin-1 and light chain 3B expression and identification of their clinical significance in human gastric cancer

Caveolin-1 (Cav-1) expression deficiency and autophagy in tumor stromal fibroblasts (hereafter fibroblasts) are involved in tumor proliferation and progression, particularly in breast and prostate cancer. The aim of this study was to detect the expression of fibroblastic Cav-1 and LC3B, markers of autophagy, in gastric cancer (GC) and to analyze their clinical significances. Furthermore, because Epstein-Barr virus (EBV)-associated GC (EBVaGC) is a unique subtype of GC; we compared the differential expression of fibroblastic Cav-1 and LC3B in EBVaGC and non-EBVaGC. Quantum dots (QDs)-based immunofluorescence histochemistry was used to examine the expression of fibroblastic Cav-1 and LC3B in 118 cases of GC with adequate stroma. QDs-based double immunofluorescence labeling was performed to detect the coexpression of Cav-1 and LC3B proteins. EBV-encoded small RNA was detected by QDs-based fluorescence in situ hybridization to identify EBVaGC. Multivariate analysis indicated that low fibroblastic Cav-1 level was an independent prognosticator (p = 0.029) that predicted poorer survival of GC patients. Positive fibroblastic LC3B was correlated with lower invasion (p = 0.032) and was positively associated with Cav-1 expression (r = 0.432, p < 0.001). EBV infection did not affect fibroblastic Cav-1 and LC3B expression. In conclusion, positive fibroblastic LC3B correlates with lower invasion, and low expression of fibroblastic Cav-1 is a novel predictor of poor GC prognosis.