Manipulation of New Fluorescent Magnetic Nanoparticles with an Electromagnetic Needle, Allowed Determining the Viscosity of the Cytoplasm of M-HeLa Cells.

Magnetic nanoparticles (MNPs) have recently begun to be actively used in biomedicine applications, for example, for targeted drug delivery, in tissue engineering, and in magnetic resonance imaging. The study of the magnetic field effect on MNPs internalized into living cells is of particular importance since it allows a non-invasive influence on cellular activity. There is data stating the possibility to manipulate and control individual MNPs utilizing the local magnetic field gradient created by electromagnetic needles (EN). The present work aimed to demonstrate the methodological and technical approach for manipulating the local magnetic field gradient, generated by EN, novel luminescent MNPs internalized in HeLa cancer cells. The controlling of the magnetic field intensity and estimation of the attractive force of EN was demonstrated. Both designs of EN and their main characteristics are also described. Depending on the distance and applied voltage, the attractive force ENs ranged from 0.056 ± 0.002 to 37.85 ± 3.40 pN. As a practical application of the presented, the evaluation of viscous properties of the HeLa cell's cytoplasm, based on the measurement of the movement rate of MNPs inside cells under impact of a known magnetic force, was carried out; the viscosity was 1.45 ± 0.04 Pa·s.

Specific nanoarchitecture of silica nanoparticles codoped with the oppositely charged Mn2+ and Ru2+ complexes for dual paramagnetic-luminescent contrasting effects.

The silica nanoparticles (SNs) co-doped with paramagnetic ([Mn(HL)]n-,) and luminescent ([Ru(dipy)3]2+) complexes are represented. The specific distribution of [Mn(HL)]n- within the SNs allows to achieve about ten-fold enhancing in magnetic relaxivities in comparison with those of [Mn(HL)]n- in solutions. The leaching of [Mn(HL)]n- from the shell can be minimized through the co-doping of [Ru(dipy)3]2+ into the core of the SNs. The co-doped SNs exhibit colloid stability in aqueous solutions, including those modeling a blood serum. The surface of the co-doped SNs was also decorated by amino- and carboxy-groups. The cytotoxicity, hemoagglutination and hemolytic activities of the co-doped SNs are on the levels convenient for "in vivo" studies, although the amino-decorated SNs cause more noticeable agglutination and suppression of cell viability. The co-doped SNs being intravenously injected into mice allows to reveal their biodistribution in both ex vivo and in vivo conditions through confocal microscopy and magnetic resonance imaging correspondingly.

ROS-generation and cellular uptake behavior of amino-silica nanoparticles arisen from their uploading by both iron-oxides and hexamolybdenum clusters.

The present work introduces combination of superparamagnetic iron oxides (SPIONs) and hexamolybdenum cluster ([{Mo6I8}I6]2-) units within amino-decorated silica nanoparticles (SNs) as promising design of the hybrid SNs as efficient cellular contrast and therapeutic agents. The heating generated by SNs doped with SPIONs (Fe3O4@SNs) under alternating magnetic field is characterized by high specific absorption rate (SAR = 446 W/g). The cluster units deposition onto both Fe3O4@SNs and "empty" silica nanoparticles (SNs) results in Fe3O4@SNs[{Mo6I8}I6] and SNs[{Mo6I8}I6] with red cluster-centered luminescence and ability to generate reactive oxygen species (ROS) under the irradiation. The monitoring of spin-trapped ROS by ESR spectroscopy technique indicates that the ROS-generation decreases in time for SNs[{Mo6I8}I6] and [{Mo6I8}I6]2- in aqueous solutions, while it remains constant for Fe3O4@SNs[{Mo6I8}I6]. The cytotoxicity is low for both Fe3O4@SNs[{Mo6I8}I6] and SNs[{Mo6I8}I6], while the flow cytometry indicates preferable cellular uptake of the former versus the latter type of the nanoparticles. Moreover, entering into nucleus along with cytoplasm differentiates the intracellular distribution of Fe3O4@SNs[{Mo6I8}I6] from that of SNs[{Mo6I8}I6], which remain in the cell cytoplasm only. The exceptional behavior of Fe3O4@SNs[{Mo6I8}I6] is explained by residual amounts of iron ions at the silica surface.

Aptamer-Conjugated Tb(III)-Doped Silica Nanoparticles for Luminescent Detection of Leukemia Cells.

DNA aptamers have many benefits for cell imaging, such as high affinity and specificity, easiness of chemical functionalization, and low cost of production. Among known aptamers, Sgc8-aptamer was selected against acute lymphoblastic leukemia cells with a dissociation constant in a nanomolar range. The aptamer was previously used for the covalent coupling with fluorescent and magnetic nanoparticles, as well as for the fabrication of aptamer-based biosensors. Among commonly used fluorescent tags, lanthanide nanoparticles offer stable luminescence with narrow, well-resolved emission peaks and the absence of photoblinking. In other words, lanthanide nanoparticles could serve as luminescence reporters and be used in biosensing. In our study, we conjugated amino- and carboxyl-modified silica-coated terbium (III) thiacalix[4]arenesulfonate luminescent nanoparticles with Sgc8-aptamer and showed the ability of the aptamer-conjugated nanoparticles to detect leukemia cells using fluorescence microscopy. In addition, we conducted a cell viability assay and confirmed that the nanoparticles do not induce spontaneous cell apoptosis or necrosis and could be potentially used for bioimaging applications.

Fluorescent magnetic nanoparticles for modulating the level of intracellular Ca2+ in motoneurons.

This report introduces both synthesis and in vitro biological behaviour of dual magnetic-fluorescent silica nanoparticles. The amino group-decoration of 78 nm sized silica nanoparticles enables their efficient internalization into motoneurons, which is visualized by the red fluorescence arising from [Ru(dipy)3]2+ complexes encapsulated into a silica matrix. The internalized nanoparticles are predominantly located in the cell cytoplasm as revealed by confocal microscopy imaging. The magnetic function of the nanoparticles resulted from the incorporation of 17 nm sized superparamagnetic iron oxide cores into the silica matrix, enabling their responsivity to magnetic fields. Fluorescence analysis revealed the "on-off" switching of Ca2+ influx under the application and further removal of the permanent magnetic field. This result for the first time highlights the movement of the nanoparticles within the cell cytoplasm in the permanent magnetic field as a promising tool to enhance the neuronal activity of motoneurons.

Green Fluorescent Terbium (III) Complex Doped Silica Nanoparticles.

The low photostability of conventional organic dyes and the toxicity of cadmium-based luminescent quantum dots have prompted the development of novel probes for in vitro and in vivo labelling. Here, a new fluorescent lanthanide probe based on silica nanoparticles is fabricated and investigated for optically traceable in vitro translocator protein (TSPO) targeting. The targeting and detection of TSPO receptor, overexpressed in several pathological states, including neurodegenerative diseases and cancers, may provide valuable information for the early diagnosis and therapy of human disorders. Green fluorescent terbium(III)-calix[4]arene derivative complexes are encapsulated within silica nanoparticles and surface functionalized amine groups are conjugated with selective TSPO ligands based on a 2-phenylimidazo[1,2-a]pyridine acetamide structure containing derivatizable carboxylic groups. The photophysical properties of the terbium complex, promising for biological labelling, are demonstrated to be successfully conveyed to the realized nanoarchitectures. In addition, the high degree of biocompatibility, assessed by cell viability assay and the selectivity towards TSPO mitochondrial membrane receptors, proven by subcellular fractional studies, highlight targeting potential of this nanostructure for in vitro labelling of mitochondria.

Nano-architecture of silica nanoparticles as a tool to tune both electrochemical and catalytic behavior of NiII@SiO2.

The present work introduces a facile synthetic route for efficient doping of [NiII(bpy) x ] into silica nanoparticles with various sizes and architectures. Variation of the latter results in different concentrations of the NiII complexes at the interface of the composite nanoparticles. The UV-Vis analysis of the nanoparticles reveals changes in the inner-sphere environment of the NiII complexes when embedded into the nanoparticles, while the inner-sphere of NiII is invariant for the nanoparticles with different architecture. Comparative analysis of the electrochemically generated redox transformations of the NiII complexes embedded in the nanoparticles of various architectures reveals the latter as the main factor controlling the accessibility of NiII complexes to the redox transitions which, in turn, controls the electrochemical behavior of the nanoparticles. The work also highlights an impact of the nanoparticulate architecture in catalytic activity of the NiII complexes within the different nanoparticles in oxidative C-H fluoroalkylation of caffeine. Both low leakage and high concentration of the NiII complexes at the interface of the composite nanoparticles enables fluoroalkylated caffeine to be obtained in high yields under recycling of the nanocatalyst five times at least.

Silica-supported silver nanoparticles as an efficient catalyst for aromatic C-H alkylation and fluoroalkylation.

The efficient catalysis of oxidative alkylation and fluoroalkylation of aromatic C-H bonds is of paramount importance in the pharmaceutical and agrochemical industries, and requires the development of convenient Ag0-based nano-architectures with high catalytic activity and recyclability. We prepared Ag-doped silica nanoparticles (Ag0/+@SiO2) with a specific nano-architecture, where ultra-small sized silver cores are immersed in silica spheres, 40 nm in size. The nano-architecture provides an efficient electrochemical oxidation of Ag+@SiO2 without any external oxidant. In turn, Ag+@SiO2 5 mol% results in 100% conversion of arenes into their alkylated and fluoroalkylated derivatives in a single step at room temperature under nanoheterogeneous electrochemical conditions. Negligible oxidative leaching of silver from Ag0/+@SiO2 is recorded during the catalytic coupling of arenes with acetic, difluoroacetic and trifluoroacetic acids, which enables the good recyclability of the catalytic function of the Ag0/+@SiO2 nanostructure. The catalyst can be easily separated from the reaction mixture and reused a minimum of five times upon electrochemical regeneration. The use of the developed Ag0@SiO2 nano-architecture as a heterogeneous catalyst facilitates aromatic C-H bond substitution by alkyl and fluoroalkyl groups, which are privileged structural motifs in pharmaceuticals and agrochemicals.

Targeted Nanoparticles for Selective Marking of Neuromuscular Junctions and ex Vivo Monitoring of Endogenous Acetylcholine Hydrolysis.

The present work for the first time introduces nanosensors for luminescent monitoring of acetylcholinesterase (AChE)-catalyzed hydrolysis of endogenous acetylcholine (ACh) released in neuromuscular junctions of isolated muscles. The sensing function results from the quenching of Tb(III)-centered luminescence due to proton-induced degradation of luminescent Tb(III) complexes doped into silica nanoparticles (SNs, 23 nm), when acetic acid is produced from the enzymatic hydrolysis of ACh. The targeting of the silica nanoparticles by α-bungarotoxin was used for selective staining of the synaptic space in the isolated muscles by the nanosensors. The targeting procedure was optimized for the high sensing sensitivity. The measuring of the Tb(III)-centered luminescence intensity of the targeted SNs by fluorescent microscopy enables us to sense a release of endogenous ACh in neuromuscular junctions of the isolated muscles under their stimulation by a high-frequency train (20 Hz, for 3 min). The ability of the targeted SNs to sense an inhibiting effect of paraoxon on enzymatic activity of AChE in ex vivo conditions provides a way of mimicking external stimuli effects on enzymatic processes in the isolated muscles.

Silica nanoparticles with Tb(III)-centered luminescence decorated by Ag0 as efficient cellular contrast agent with anticancer effect.

The present work introduces composite luminescent nanoparticles (Ag0-Tb3+-SNs), where ultra-small nanosilver (4 ±â€¯2 nm) is deposited onto amino-modified silica nanoparticles (35±6 nm) doped by green luminescent Tb(III) complexes. Ag0-Tb3+-SNs are able to image cancer (Hep-2) cells in confocal microscopy measurements due to efficient cell internalization, which is confirmed by TEM images of the Hep-2 cells exposed by Ag0-Tb3+-SNs. Comparative analysis of the cytotoxicity of normal fibroblasts (DK-4) and cancer cells (Hep-2) incubated with various concentrations of Ag0-Tb3+-SNs revealed the concentration range where the toxic effect on the cancer cells is significant, while it is insignificant towards the nonmalignant fibroblasts cells. The obtained results reveal Ag0-Tb3+-SNs as good cellular contrast agent able to induce the cancer cells death, which makes them promising theranostic in cancer diagnostics and therapy.

Luminescent nanoparticles for rapid monitoring of endogenous acetylcholine release in mice atria.

The present work introduces for the first time a nanoparticulate approach for ex vivo monitoring of acetylcholinesterase-catalyzed hydrolysis of endogenous acetylcholine released from nerve varicosities in mice atria. Amino-modified 20-nm size silica nanoparticles (SNs) doped by luminescent Tb(III) complexes were applied as the nanosensors. Their sensing capacity results from the decreased intensity of Tb(III)-centred luminescence due to the quenching effect of acetic acid derived from acetylcholinesterase-catalyzed hydrolysis of acetylcholine. Sensitivity of the SNs in monitoring acetylcholine hydrolysis was confirmed by in vitro experiments. Isolated atria were exposed to the nanosensors for 10 min to stain cell membranes. Acetylcholine hydrolysis was monitored optically in the atria samples by measuring quenching of Tb(III)-centred luminescence by acetic acid derived from endogenous acetylcholine due to its acetylcholinesterase-catalyzed hydrolysis. The reliability of the sensing was demonstrated by the quenching effect of exogenous acetylcholine added to the bath solution. Additionally, no luminescence quenching occurred when the atria were pre-treated with the acetylcholinesterase inhibitor paraoxon.

Cellular imaging by green luminescence of Tb(III)-doped aminomodified silica nanoparticles.

The work introduces Tb(III)-centered luminescence of amino-modified silica nanoparticles doped with Tb(III) complexes for cellular imaging. For these purposes water-in-oil procedure was optimized for synthesis of 20 and 35nm luminescent nanoparticles with amino-groups embedded on the surface. The obtained results indicate an impact of the nanoparticle size in decoration, aggregation behavior and luminescent properties of the nanoparticles in protein-based buffer solutions. Formation of a protein-based corona on the nanoparticles surface was revealed through the effect of the nanoparticles on helical superstructure of BSA. This effect is evident from CD spectral data, while no any size impact on the adsorption of BSA onto aminomodified silica surface was observed. Cellular uptake of the nanoparticles studied by confocal and TEM microscopy methods indicates greater cellular uptake for the smaller nanoparticles. Cytotoxicity of the nanoparticles was found to agree well with their cellular uptake behavior, which in turn was found to be greater for the smaller nanoparticles.

Tuning the non-covalent confinement of Gd(III) complexes in silica nanoparticles for high T1-weighted MR imaging capability.

The present work introduces deliberate synthesis of Gd(III)-doped silica nanoparticles with high relaxivity at magnetic field strengths below 1.5T. Modified microemulsion water-in-oil procedure was used in order to achieve superficial localization of Gd(III) complexes within 40-55nm sized silica spheres. The relaxivities of the prepared nanoparticles were measured at 0.47, 1.41 and 1.5T with the use of both NMR analyzer and whole body NMR scanner. Longitudinal relaxivities of the obtained silica nanoparticles reveal significant dependence on the confinement mode, changing from 4.1 to 49.6mM-1s-1 at 0.47T when the localization of Gd(III) complexes changes from core to superficial zones of the silica spheres. The results highlight predominant contribution of the complexes located close to silica/water interface to the relaxivity of the nanoparticles. Low effect of blood proteins on the relaxivity in the aqueous colloids of the nanoparticles was exemplified by serum bovine albumin. T1- weighted MRI data indicate that the nanoparticles provide strong positive contrast at 1.5T, which along with low cytotoxicity effect make a good basis for their application as contrast agents.

A Ni(iii) complex stabilized by silica nanoparticles as an efficient nanoheterogeneous catalyst for oxidative C-H fluoroalkylation.

We have developed Ni(III)-doped silica nanoparticles ([(bpy)xNi(III)]@SiO2) as a recyclable, low-leaching, and efficient oxidative functionalization nanocatalyst for aromatic C-H bonds. The catalyst is obtained by doping the complex [(bpy)3Ni(II)] on silica nanoparticles along with its subsequent electrooxidation to [(bpy)xNi(III)] without an additional oxidant. The coupling reaction of arenes with perfluoroheptanoic acid occurs with 100% conversion of reactants in a single step at room temperature under nanoheterogeneous conditions. The catalyst content is only 1% with respect to the substrates under electrochemical regeneration conditions. The catalyst can be easily separated from the reaction mixture and reused a minimum of five times. The results emphasize immobilization on the silica support and the electrochemical regeneration of Ni(III) complexes as a facile route for developing an efficient nanocatalyst for oxidative functionalization.

Luminescent silica nanoparticles for sensing acetylcholinesterase-catalyzed hydrolysis of acetylcholine.

This work highlights the H-function of Tb(III)-doped silica nanoparticles in aqueous solutions of acetic acid as a route to sense acetylcholinesterase-catalyzed hydrolysis of acetylcholine (ACh). The H-function results from H(+)-induced quenching of Tb(III)-centered luminescence due to protonation of Tb(III) complexes located close to silica/water interface. The H-function can be turned on/switched off by the concentration of complexes within core or nanoparticle shell zones, by the silica surface decoration and adsorption of both organic and inorganic cations on silica surface. Results indicate the optimal synthetic procedure for making nanoparticles capable of sensing acetic acid produced by enzymatic hydrolysis of acetylcholine. The H-function of nanoparticles was determined at various concentrations of ACh and AChE. The measurements show experimental conditions for fitting the H-function to Michaelis-Menten kinetics. Results confirm that reliable fluorescent monitoring AChE-catalyzed hydrolysis of ACh is possible through the H-function properties of Tb(III)-doped silica nanoparticles.

Nanoheterogeneous catalysis in electrochemically induced olefin perfluoroalkylation.

Ni-catalyzed electroreductive olefin perfluoroalkylation affords both monomeric and dimeric products depending on the reaction media. Recycling of the catalyst can be achieved by immobilization of a (bpy)NiBr2 complex on silica nanoparticles decorated with anchoring amino-groups. Switching the homogeneous and heterogeneous catalysts is found to be one more factor to control the product ratio. This catalytic technique is both green and atom economical and combines the advantages of nanoheterogeneous catalysis and electrocatalysis.

Tb(III)-doped silica nanoparticles for sensing: effect of interfacial interactions on substrate-induced luminescent response.

The present work introduces the easy modification of the water-in-oil microemulsion procedure aimed at the doping of the Tb(III) complexes within core or shell zones of the silica nanoparticles (SNs), which are designated as "core-shell", "shell", and "core". The dye molecules, chelating ligands, and copper ions were applied as the quenchers of Tb(III)-centered luminescence through dynamic or/and static mechanisms. The binding of the quenchers at the silica/water interface results in the quenching of the Tb(III) complexes within SNs, which, in turn, is greatly dependent on the synthetic procedure. The luminescence of "core" SNs remains unchanged under the binding of the quenchers at the silica/water interface. The quenching through dynamic mechanism is more significant for "core-shell" and "shell" than for "core" SNs. Thus, both "core-shell" and "shell" SNs have enough percentage of the Tb(III) complexes located close to the interface for efficient quenching through the energy transfer. The quenching through the ion or ligand exchange is most efficient for "core-shell" SNs due to the greatest percentage of the Tb(III) complexes at the silica/water interface, which correlates with the used synthetic procedure. The highlighted regularities introduce the applicability of "core-shell" SNs used as silica beads for phosphatidylcholine bilayers in sensing their permeability toward the quenching ions.

The interfacial interactions of Tb-doped silica nanoparticles with surfactants and phospholipids revealed through the fluorescent response.

The quenching effect of dyes (phenol red and bromothymol blue) on Tb(III)-centered luminescence enables to sense the aggregation of cationic and anionic surfactants near the silica surface of Tb-doped silica nanoparticles (SN) in aqueous solutions. The Tb-centered luminescence of non-decorated SNs is diminished by the inner filter effect of both dyes. The decoration of the silica surface by cationic surfactants induces the quenching through the energy transfer between silica coated Tb(III) complexes and dye anions inserted into surfactant aggregates. Thus the distribution of surfactants aggregates at the silica/water interface and in the bulk of solution greatly affects dynamic quenching efficiency. The displacement of dye anions from the interfacial surfactant adlayer by anionic surfactants and phospholipids is accompanied by the "off-on" switching of Tb(III)-centered luminescence.

Temperature induced phase separation of luminescent silica nanoparticles in Triton X-100 solutions.

The aggregation and cloud point behavior of Tb(III)-doped silica nanoparticles has been studied in Triton X-100 (TX-100) solutions at various concentration conditions by fluorimetry, dynamic light scattering, electrophoresis and transmission electron microscopy methods. The temperature responsive behavior of nanoparticles is observed at definite concentration of TX-100, where the aggregation of TX-100 at the silica/water interface is evident from the increased size of the silica nanoparticles. The reversible dehydration of TX-100 aggregates at the silica/water interface should be assumed as the main reason of the temperature induced phase separation of silica nanoparticles. The distribution of nanoparticles between aqueous and surfactant rich phases at the phase separation conditions can be modified by the effect of additives.

Novel highly charged silica-coated Tb(III) nanoparticles with fluorescent properties sensitive to ion exchange and energy transfer processes in aqueous dispersions.

Novel silica-coated Tb(III) nanoparticles with high luminecsence were synthesized using the reverse microemulsion procedure. The quenching of luminescent properties of these nanoparticles can be achieved by ion exchange and energy transfer mechanisms. The quenching through the ion exchange of Tb(III) by H+ or La(III) is time dependent, indicating that the ion exchange is probably diffusion controlled. The quenching by Co(III) complex cations is achieved by the energy transfer mechanism and thus is not time dependent. The analysis of quenching data in Stern-Volmer cooordinates reveal the negative charge of the silica-coated Tb(III)-TCAS nanoparticles and several types of luminophoric species, located within the core and close to the surface of silica nanoparticles.