Sensing with fluorescent nanoparticles

Simple and Cost-Effective Quantum Dot Chemodosimeter for Visual Detection of Biothiols in Human Blood Serum

An emission "turn-off" chemodosimeter for the naked-eye detection of biothiols using silica-overcoated cadmium selenide quantum dots is developed. Hole scavenging by the thiol group of cysteine, homocysteine, or glutathione on interaction with quantum dots resulted in an instant and permanent emission quenching under physiologically relevant conditions. Also, the emission suppression is so specific that thiols and substituted thiols (methionine and cystine) can easily be distinguished. A pilot experiment for the visual detection of serum thiols in human blood was also conducted. Densitometry analysis proved the potential of this system as a new methodology in clinical chemistry and research laboratories for routine blood and urine analyses using a simple procedure. This method enables one to visually distinguish biothiols and oxidized biothiols, whose ratio plays a crucial role in maintaining "redox thiol status" in the blood.

Naphthalene Diimide-Based Orange Emitting Luminogen: A Fluorometric Probe for Thiol Sensing through the Click Reaction

Fluorometric sensors have gained considerable attention in various fields, including environmental monitoring, biomedical research, and clinical diagnostics. This article delineates the fabrication of an orange emitting naphthalene diimide (NDI) derivative consisting of maleimide moiety (NDI-mal) for fluorometric sensing of thiols. Spherical shaped organic nanoparticles (∼100-150 nm) were constructed by NDI-mal in dimethyl sulfoxide (DMSO)/dimethylformamide (DMF)-water through J-type aggregation. NDI-mal displayed self-assembly driven aggregation-induced emission (AIE) through excimer formation at λem= 588 nm at fw = 99 vol % DMSO/DMF-water. Naphthyl residue at both terminals of NDI-mal facilitates intramolecular charge transfer (ICT) from the donor naphthyl residue to the acceptor NDI core. The fluorescence intensity of NDI-mal fluorescent organic nanoparticles (FONPs) got quenched in the presence of thiols due to thiol-maleimide adduct formation (Michael addition). NDI-mal FONPs selectively probed thiol functionalized small molecules (4-aminothiophenol), biomolecules (glutathione (GSH)), and proteins (reduced BSA) with high sensitivity having a limit of detection of 15.3 nM, 6.0 nM, and 9.2 ng/mL, respectively. Importantly, thiol sensing was selective against analogous small molecules, biomolecules, and proteins devoid of thiol moieties. Cellular imaging demonstrated selective diagnosis of cancer cells by NDI-mal FONPs through quenching of its emission upon interaction with thiols in B16F10 cells due to the high abundance of GSH in cancer cells compared to NIH3T3 cells. NDI-mal FONPs emitted their native fluorescence inside cells subjected to reactive oxygen species mediated thiol oxidation via Fenton's reaction. Notably, GSH-maleimide adduct formation by NDI-mal FONPs displayed notable therapeutic efficacy against cancer cells having ∼2.4-fold higher killing of B16F10 in comparison to NIH3T3 cells possibly through oxidative stress induced apoptosis owing to the depletion in the GSH level. Thus, NDI-mal AIE-gen successfully emerged as a selective and sensitive probe toward thiols through thiol-maleimide click chemistry with therapeutic ability against cancer cells in the absence of systematic intervention.

What makes carbon nanoparticle a potent material for biological application?

Carbon materials are generally utilized in the form of carbon allotropes and their characteristics are exploited as such or for improving the thermal, electrical, optical, and mechanical properties of other biomaterials. This has now found a broader share in conventional biomaterial space with the generation of nanodiamond, carbon dot, carbon nanoparticles (CNPs), and so forth. With properties of better biocompatibility, intrinsic optical emission, aqueous suspendability, and easier surface conjugation possibilities made CNPs as one of the fore most choice for biological applications especially for use in intracellular spaces. There are various reports available presenting methods of preparing, characterizing, and using CNPs for various biological applications but a collection of information on what makes CNP a suitable biomaterial to achieve those biological activities is yet to be provided in a significant way. Herein, a series of correlations among synthesis, characterization, and mode of utilization of CNP have been incorporated along with the variations in its use as agent for sensing, imaging, and therapy of different diseases or conditions. It is ensembled that how simplified and optimized methods of synthesis is correlated with specific characteristics of CNPs which were found to be suitable in the specific biological applications. These comparisons and correlations among various CNPs, will surely provide a platform to generate new edition of this nanomaterial with improvised applications and newer methods of evaluating structural, physical, and functional properties. This may ensure the eventual use of CNPs for human being for specific need in near future. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > Biosensing Diagnostic Tools > In Vitro Nanoparticle-Based Sensing Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Colloidal Self-Assembly Approaches to Smart Nanostructured Materials

Colloidal self-assembly refers to a solution-processed assembly of nanometer-/micrometer-sized, well-dispersed particles into secondary structures, whose collective properties are controlled by not only nanoparticle property but also the superstructure symmetry, orientation, phase, and dimension. This combination of characteristics makes colloidal superstructures highly susceptible to remote stimuli or local environmental changes, representing a prominent platform for developing stimuli-responsive materials and smart devices. Chemists are achieving even more delicate control over their active responses to various practical stimuli, setting the stage ready for fully exploiting the potential of this unique set of materials. This review addresses the assembly of colloids into stimuli-responsive or smart nanostructured materials. We first delineate the colloidal self-assembly driven by forces of different length scales. A set of concepts and equations are outlined for controlling the colloidal crystal growth, appreciating the importance of particle connectivity in creating responsive superstructures. We then present working mechanisms and practical strategies for engineering smart colloidal assemblies. The concepts underpinning separation and connectivity control are systematically introduced, allowing active tuning and precise prediction of the colloidal crystal properties in response to external stimuli. Various exciting applications of these unique materials are summarized with a specific focus on the structure-property correlation in smart materials and functional devices. We conclude this review with a summary of existing challenges in colloidal self-assembly of smart materials and provide a perspective on their further advances to the next generation.

Charge carrier pairing can impart efficient reduction efficiency to core/shell quantum dots: applications for chemical sensing

Semiconductor quantum dots (QDs) are bright fluorophores that have significant utility for imaging and sensing applications. Core QDs are often employed in chemosensing via redox processes that modulates their fluorescence in the presence of an analyte. However, such particles lack robust surface passivation and generally contain a sizable portion of nonfluorescent QDs, which is detrimental to the detection limit. We investigated an approach to "turn on" non-fluorescent core QDs by lightly overcoating them with a thin shell of a higher bandgap semiconductor. The shell augments the population of sensing chromophores and increases the emission lifetime; however, it simultaneously mollifies redox processes that are responsible for analyte sensitivity to begin with. This balancing act was successfully applied to enhance the sensitivity of CdZnS/ZnS QDs towards 2,4,6-trinitrotoluene (TNT). Unexpectedly, it was found that CdZnS/ZnS QDs with very thick shells retained substantial sensitivity to TNT. This observation may be due to close coupling of the reduced substrate with the QD hole that is enabled by the near-degeneracy of holes in the core CdZnS and ZnS shell. The ability of core/shell QDs to retain substantial reducing power may have implications for other applications that can benefit from the enhanced stability of robust core/shell nanomaterials.

Upconversion nanoparticles as intracellular pH messengers

Upconversion nanoparticles (UCNPs) should be particularly well suited for measurement inside cells because they can be imaged down to submicrometer dimensions in near real time using fluorescence microscopy, and they overcome problems, such as photobleaching, autofluorescence, and deep tissue penetration, that are commonly encountered in cellular imaging applications. In this study, the performance of an UCNP modified with a pH-sensitive dye (pHAb) is studied. The dye (emission wavelength 580 nm) was attached in a polyethylene imine (PEI) coating on the UCNP and excited via the 540-nm UCNP emission under 980-nm excitation. The UC resonance energy transfer efficiencies at different pHs ranged from 25 to 30% and a Förster distance of 2.56 nm was predicted from these results. Human neuroblastoma SH-SY5Y cells, equilibrated with nigericin H+/K+ ionophore to equalize the intra- and extracellular pH' showed uptake of the UCNP-pHAb conjugate particles and, taking the ratio of the intensity collected from the pHAb emission channel (565-630 nm) to that from the UCNP red emission channel (640-680 nm), produced a sigmoidal pH response curve with an apparent pKa for the UCNP-pHAb of ~ 5.1. The UCNP-pHAb were shown to colocalize with LysoBrite dye, a lysosome marker. Drug inhibitors such as chlorpromazine (CPZ) and nystatin (NYS) that interfere with clathrin-mediated endocytosis and caveolae-mediated endocytosis, respectively, were investigated to elucidate the mechanism of nanoparticle uptake into the cell. This preliminary study suggests that pH indicator-modified UCNPs such as UCNP-pHAb can report pH in SH-SY5Y cells and that the incorporation of the nanoparticles into the cell occurs via clathrin-mediated endocytosis. Graphical abstract.

Fabrication of Orange-Emitting Organic Nanoparticle-Protamine Conjugate: Fluorimetric Sensor of Heparin

Among the diverse sensing techniques, fluorimetric detection dominates over the other methods because of its rapid signaling, high selectivity and sensitivity, and operational simplicity. This present article delineates fabrication of a fluorescent organic nanoparticle-protamine (FONP-Pro) conjugate for selective and sensitive detection of heparin simply by exploitation of the aggregation-induced emission (AIE) property of the FONPs. Naphthalene diimide-based bola-type amphiphilic molecules (NDI-1) comprise a naphthyl residue and a 3-aminopyridyl unit at both terminals, forming organic nanoparticles in a dimethyl sulfoxide-water binary solvent mixture, and exhibited AIE through excimer formation. The presence of naphthyl residue in the molecular backbone facilitates the intramolecular charge transfer to generate orange-emitting (λ_em = 594 nm) AIE-luminogen (AIE-gen). The aminopyridine residues within NDI-1 induced negative surface charge on NDI-1 FONPs, which facilitated interaction with positively charged protamine (Pro) to construct FONP-Pro conjugates. Formation of this NDI-1 FONP-Pro conjugate through the interaction between Pro and FONP drastically reduced the orange emission intensity (fluorescence off) of the AIE-gens. Interestingly, addition of heparin to this FONP-Pro conjugate turned on the fluorescence signal of FONPs through unwinding of the Pro from the FONP surface because of a strong binding affinity between heparin and Pro. Formation of the FONP-Pro conjugate and fluorimetric sensing of heparin was investigated by monitoring the change in emission behavior of NDI-1 FONPs. Also, the heparin-sensing was found to be highly selective against many other biomolecules including proteins, enzymes, and DNA. Hence, a selective and efficient heparin sensor (FONP-Pro) was developed having a limit of detection of 12 nM simply by utilizing the fluorescence "turn-off" and "turn-on" mechanism of NDI-1 FONP.

Dual-Mode, Anisotropy-Encoded, Ratiometric Fluorescent Nanosensors: Towards Multiplexed Detection

A nanosensor with dual-mode fluorescence response to pH and an encoded identification signal, was developed by exploiting excitation energy transfer and tailored control of molecular organization in core-shell nanoparticles. Multiple signals were acquired in a simple single-excitation dual-emission channels set-up.

More Than a Light Switch: Engineering Unconventional Fluorescent Configurations for Biological Sensing

Fluorescence is a powerful and sensitive tool in biological detection, used widely for cellular imaging and in vitro molecular diagnostics. Over time, three prominent conventions have emerged in the design of fluorescent biosensors: a sensor is ideally specific for its target, only one fluorescence signal turns on or off in response to the target, and each target requires its own sensor and signal combination. These are conventions but not requirements, and sensors that break with one or more of these conventions can offer new capabilities and advantages. Here, we review "unconventional" fluorescent sensor configurations based on fluorescent dyes, proteins, and nanomaterials such as quantum dots and metal nanoclusters. These configurations include multifluorophore Förster resonance energy transfer (FRET) networks, temporal multiplexing, photonic logic, and cross-reactive arrays or "noses". The more complex but carefully engineered biorecognition and fluorescence signaling modalities in unconventional designs are richer in information, afford greater multiplexing capacity, and are potentially better suited to the analysis of complex biological samples, interactions, processes, and diseases. We conclude with a short perspective on the future of unconventional fluorescent sensors and encourage researchers to imagine sensing beyond the metaphorical light bulb and light switch combination.

A method for estimating intracellular ion concentration using optical nanosensors and ratiometric imaging

Optical nanoparticle (NP)-based sensors have been widely implemented as tools for detection of targeted ions and biomolecules. The NP sensing platform offer a modular design that can incorporate different sensing components for greater target specificity and the ability to tune the dynamic range, as well as encapsulation of multiple dyes to generate a ratiometric signal with varying spectra. Despite these advantages, demonstrating quantitative ion imaging for intracellular measurement still possess a major challenge. Here, we describe fundamentals that enable intracellular validation of this approach using ion-selective nanosensors for investigating calcium (Ca²⁺) as a model ion. While conventional indicators can improve individual aspects of indicator performance such as Kd, wavelength, and ratiometric measurements, the use of NP sensors can achieve combined benefits of addressing these issues simultaneously. The nanosensor incorporates highly calcium-selective ionophores and two fluorescence indicators that act as signal transducers to facilitate quantitative ratiometric imaging. For intracellular Ca²⁺ application, the sensors are fine-tuned to physiological sensing range, and live-cell imaging and quantification are demonstrated in HeLa cells loaded with nanosensors and their responsiveness to carbachol-evoked store release (~400 nM). The current nanosensor design thus provides a promising sensing platform for real-time detection and optical determination of intracellular ions.

Carbon-dot-based dual-emission silica nanoparticles as a ratiometric fluorescent probe for Bisphenol A

A simple and effective strategy for designing a ratiometric fluorescent nanosensor is described in this work. A carbon dots (CDs) based dual-emission nanosensor for Bisphenol A (BPA) was prepared by coating CDs on the surface of dye-doped silica nanoparticles. The fluorescence of dual-emission silica nanoparticles was quenched in hydrochloric acid by potassium bromate (KBrO₃) oxidation; BPA inhibited KBrO₃ oxidation, resulting in the ratiometric fluorescence response of dual-emission silica nanoparticles. Several important parameters affecting the performance of the nanosensor were investigated and optimized. The detection limit of this nanosensor was 0.80ng mL^-1 with a linear range from 10 to 500ng mL^-1. This was applied successfully to determine BPA in the leached solution of different plastic products with satisfactory results.

Controlled synthesis of soluble conjugated polymeric nanoparticles for fluorescence detection

Highly fluorescent soluble conjugated polymeric nanoparticles (SCPNs) were synthesized in confined nanoreactors and used for fluorescence sensing of glucose and Fe ion.

Ultrasensitive optical detection of anions by quantum dots

Quantum dots (QDs) have received great interest for diverse applications over the past few decades due to their unique photophysical properties like their tunable band gap, facile solution processability and versatile surface functionalization with different ligands. Quantum dot based optical analysis techniques with high sensitivity and selectivity have been developed to detect anions in aqueous solution for environmental monitoring, medicinal diagnostics, and the analysis of biological samples and industrial processes. Here we review the latest research progress of semiconductor QDs for sensing of anions in aqueous solution or in vivo, and discuss the photophysical mechanisms and outlook for the potential development in QD based optical sensing for anions.

Silica nanoparticles functionalized with polyamidoamine (PAMAM) dendrimers as platforms for photoluminescence (PL) sensing of copper and cyanide ions

Functionalized nanoparticles for photoluminescence (PL) applications are a promising technology for biomedical imaging and as sensors for small molecules. This work presents a new method to modify silica nanoparticles (SNP) using the bifunctional linker 1,1'-carbonyldiimidazole (CDI) with a series of polyamidoamine (PAMAM) dendrimer molecules followed by grafting of fluorescein isothiocyanate (FITC) or rhodamine B isothiocyanate (RITC) to create platforms for photoluminescence (PL) sensors. A dendrimer size and charge-variable response to only copper(II) ions confirmed the prediction of a selective turn-off sensor via proximity quenching. Both dye density and Cu(2+) quenching efficiency peaked with SNP-dendrimer generation 4 (64 terminal amines). In addition, changing the terminal dendrimer arms to carboxylic acid end groups increased the copper quenching suggesting that more metal ion binding sites were created in close proximity to the dyes. Of the small anions tested for a turn-off sensor, only cyanide ion fully restored the PL when reaching a 2:1 CN(-):Cu(2+) ratio, while EDTA was not as effective at the same ratio. Therefore, dendrimer size and surface charge on the nanoparticles controlled the dye loading and copper quenching efficiency, while creating multiple binding sites for cyanide over other metal binding anions.

Graphene: The Missing Piece for Cancer Diagnosis?

This paper reviews recent advances in graphene-based biosensors development in order to obtain smaller and more portable devices with better performance for earlier cancer detection. In fact, the potential of Graphene for sensitive detection and chemical/biological free-label applications results from its exceptional physicochemical properties such as high electrical and thermal conductivity, aspect-ratio, optical transparency and remarkable mechanical and chemical stability. Herein we start by providing a general overview of the types of graphene and its derivatives, briefly describing the synthesis procedure and main properties. It follows the reference to different routes to engineer the graphene surface for sensing applications with organic biomolecules and nanoparticles for the development of advanced biosensing platforms able to detect/quantify the characteristic cancer biomolecules in biological fluids or overexpressed on cancerous cells surface with elevated sensitivity, selectivity and stability. We then describe the application of graphene in optical imaging methods such as photoluminescence and Raman imaging, electrochemical sensors for enzymatic biosensing, DNA sensing, and immunosensing. The bioquantification of cancer biomarkers and cells is finally discussed, particularly electrochemical methods such as voltammetry and amperometry which are generally adopted transducing techniques for the development of graphene based sensors for biosensing due to their simplicity, high sensitivity and low-cost. To close, we discuss the major challenges that graphene based biosensors must overcome in order to reach the necessary standards for the early detection of cancer biomarkers by providing reliable information about the patient disease stage.

Selective molecular recognition on calixarene-functionalized 3D surfaces

Calixarene based various 3D surface materials with unique signal amplification in molecular recognition are presented, including quantum dots (QDs), metal nanoparticles (NPs), nanotubes, and mesoporous silica.

Fabrication of hybridized nanoparticles with aggregation-induced emission characteristics and application for cell imaging

More TPE-CS/HA nanoparticles are endocytosed by culture for a long time, resulting in a much stronger fluorescence emission.

Preparation of ORMOSIL nanoparticles conjugated with vitamin D3analogues and their biological evaluation

Dye-doped multifunctional organically modified silica (ORMOSIL) nanoparticles were prepared within surfactant stabilized microemulsions and conjugated with several vitamin D₃derivatives.

Aptamer/Polydopamine Nanospheres Nanocomplex for in Situ Molecular Sensing in Living Cells

A nanocomplex was developed for molecular sensing in living cells, based on the fluorophore-labeled aptamer and the polydopamine nanospheres (PDANS). Due to the interaction between ssDNA and PDANS, the aptamer was adsorbed onto the surface of PDANS forming the aptamer/PDANS nanocomplex, and the fluorescence was quenched by PDANS through Förster resonance energy transfer (FRET). In vitro assay, the introduction of adenosine triphosphate (ATP) led to the dissociation of the aptamer from the PDANS and the recovery of the fluorescence. The retained fluorescence of the nanocomplex was found to be linear with the concentration of ATP in the range of 0.01-2 mM, and the nanocomplex was highly selective toward ATP. For the strong protecting capability to nucleic acids from enzymatic cleavage and the excellent biocompatibility of PDANS, the nanocomplex was transported into cells and successfully realized "signal on" sensing of ATP in living cells; moreover, the nanocomplex could be employed for ATP semiquantification. This design provides a strategy to develop biosensors based on the polydopamine nanomaterials for intracellular molecules analysis. For the advantages of polydopamine, it would be an excellent candidate for many biological applications, such as gene and drug delivery, intracellular imaging, and in vivo monitoring.

Selective chemosensing of spermidine based on fluorescent organic nanoparticles in aqueous media via a Fe3+ displacement assay

An organic–inorganic nanohybrid complex of a tripodal complex was used for the selective determination of spermidine and its use in real sample analysis.

Intramolecular charge-transfer emission from conjugated polymer nanoparticles: the terminal group effect on electronic and optical properties

Efficient tuning of electronic and optical properties of conjugated polymer nanoparticles by intramolecular charge transfer between the core and the terminal groups is demonstrated for the first time.

Dye-doped silica nanoparticles as luminescent organized systems for nanomedicine

This review summarizes developments and applications of luminescent dye doped silica nanoparticles as versatile organized systems for nanomedicine.

Silica nanoparticles for cell imaging and intracellular sensing

There is increasing interest in the use of nanoparticles (NPs) for biomedical applications. In particular, nanobiophotonic approaches using fluorescence offers the potential of high sensitivity and selectivity in applications such as cell imaging and intracellular sensing. In this review, we focus primarily on the use of fluorescent silica NPs for these applications and, in so doing, aim to enhance and complement the key recent review articles on these topics. We summarize the main synthetic approaches, namely the Stöber and microemulsion processes, and, in this context, we deal with issues in relation to both covalent and physical incorporation of different types of dyes in the particles. The important issue of NP functionalization for conjugation to biomolecules is discussed and strategies published in the recent literature are highlighted and evaluated. We cite recent examples of the use of fluorescent silica NPs for cell imaging in the areas of cancer, stem cell and infectious disease research, and we review the current literature on the use of silica NPs for intracellular sensing of oxygen, pH and ionic species. We include a short final section which seeks to identify the main challenges and obstacles in relation to the potential widespread use of these particles for in vivo diagnostics and therapeutics.

Thermal and photic stimuli-responsive polydiacetylene liposomes with reversible fluorescence

A novel reversible fluorescent switch of a polydiacetylene liposome (PDA liposome) was realized by alternating heating and UV irradiation processes. The reversible fluorescence switching of the PDA liposome was mainly caused by the microstructural changes of the PDA backbone in the PDA liposomes under the alternating conditions of heating and UV irradiation.

Targeted delivery of photosensitizers: efficacy and selectivity issues revealed by multifunctional ORMOSIL nanovectors in cellular systems

PEGylated and non-PEGylated ORMOSIL nanoparticles prepared by microemulsion condensation of vinyltriethoxy-silane (VTES) were investigated in detail for their micro-structure and ability to deliver photoactive agents. With respect to pure silica nanoparticles, organic modification substantially changes the microstructure and the surface properties. This in turn leads to a modulation of both the photophysical properties of embedded photosensitizers and the interaction of the nanoparticles with biological entities such as serum proteins. The flexibility of the synthetic procedure allows the rapid preparation and screening of multifunctional nanosystems for photodynamic therapy (PDT). Selective targeting of model cancer cells was tested by using folate, an integrin specific RGD peptide and anti-EGFR antibodies. Data suggest the interference of the stealth-conferring layer (PEG) with small targeting agents, but not with bulky antibodies. Moreover, we showed that selective photokilling of tumour cells may be limited even in the case of efficient targeting because of intrinsic transport limitations of active cellular uptake mechanisms or suboptimum localization.

Silver-pyrazole complexes as hybrid multifunctional materials with metallomesogenic and photoluminescent behaviour

New pyridine-functionalised pyrazole compounds [Hpz(R(n)py)] (R(n) = C(6)H(4)OC(n)H(2n+1); n = 12, 14, 16, 18; 1-4) and their corresponding silver complexes [Ag(Hpz(R(n)py))(2)][A] ([A] = NO(3)(-), BF(4)(-); ) have been synthesised and characterised. All of them, with the exception of 1, are liquid crystal materials exhibiting monotropic or enantiotropic SmA mesophases, in contrast to the non-mesomorphic related R(n)-monosubstituted compounds. Because the molecular shape is a factor determinant in the organisation of molecules in the liquid crystal phase, we were interested in solving the crystal structure of representative examples of the mentioned compounds, such as 1 and 6. So, the X-ray crystal structure of [Hpz(R(12)py)] 1 shows the presence of dimeric units through N-H···N hydrogen bonds, which conform to an elongated molecular shape containing a double chain length. On the other hand, the structure of [Ag(Hpz(R(14)py))(2)][NO(3)] 6 also evidenced Ag-Ag bonded dimers from 'U'-shaped cationic entities. These dimers exhibit four chains, two by two alternated, so giving rise to a longer molecular length. Of particular interest was to observe that in both structures, the dimers are layer-like packed, their lamellar structures being related to that of the mesophases found in both kinds of compounds. Furthermore, the analysis of the optical data of the compounds 2 and 4 and the silver compounds 5, 6, 9 and 10 as representative examples pointed out their luminescent behaviour as well as their good ability to act as fluorescent probes for Zn(2+), Cu(2+) and Ag(+). An increase in the fluorescence quantum yields is observed in the final complexes produced in the titrations, this fact being specially notable when 9 was used as the starting compound.

Cytochrome c conjugated to ZnO-MAA nanoparticles: the study of interaction and influence on protein structure

Nanoparticle-protein conjugates have potential for numerous applications due to the combination of the properties of both components. In this paper we studied the conjugation of horse heart cytochrome c with ZnO nanoparticles modified by mercaptoacetic acid (MAA) which may be a material with great potential in anticancer therapy as a consequence of synergic effect of both components. Cyt c adsorption to the ZnO-MAA NPs surface was studied by UV-vis spectroscopy and by a dynamic light scattering in various pH. The results indicate that the optimal pH for the association of protein with modified nanoparticles is in range 5.8-8.5 where 90-96% of cytochrome c was assembled on ZnO-MAA nanoparticles. The interaction of proteins with nanoparticles often results in denaturation or loss of protein function. Our observations from UV-vis spectroscopy and circular dichroism performed preserved protein structure after the interaction with modified nanoparticles.

Room-temperature reactions for self-cleaning molecular nanosensors

New sensing techniques for detecting molecules, especially self-cleaning sensors, are in demand. Here we describe a room-temperature process in which a nanostructured substrate catalyzes the reaction of a target molecule with atmospheric oxygen and the reaction energy is absorbed by the substrate, where it can in principle be detected. Specifically, we report first-principles calculations describing a reaction between 2,4-dinitrotoluene (DNT) and atmospheric O(2) catalyzed by Fe-porphyrin at room temperature, incorporating an oxygen into the methyl group of DNT and releasing 1.9 eV per reaction. The atomic oxygen left on the Fe site can be removed by reacting with another DNT molecule, restoring the Fe catalyst.

Electrospinning of poly(L-lactide) nanofibers encapsulated with water-soluble fullerenes for bioimaging application

Photoluminescent fullerene nanoparticles/nanofibers have potential applications in bioimaging. A novel fluorescent nanofibrous material, consisting of fullerene nanoparticles and poly(L-lactide) (PLLA), was fabricated via a simple electrospinning method, and the composite nanofibers were characterized by various techniques such as scanning electron microscopy (SEM), laser scanning confocal microscopy (LSCM), and transmission electron microscopy (TEM). The nanofibers were uniform, and their surfaces were reasonably smooth, with the average diameters of fibers ranging from 300 to 600 nm. The fullerene nanoparticles were encapsulated within the composite nanofibers, forming a core-shell structure. The nanofiber scaffolds showed excellent hydrophilic surface due to the addition of water-soluble fullerene nanoparticles. The composite nanofibers used as substrates for bioimaging in vitro were evaluated with human liver carcinoma HepG2 cells, the fullerene nanoparticles signal almost displayed in every cell, implying the potential of fluorescent fullerene nanoparticles/PLLA nanofibers to be used as scaffolds for bioimaging application.