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.

pH-Driven Intracellular Nano-to-Molecular Disassembly of Heterometallic [Au2L2]{Re6Q8} Colloids (L = PNNP Ligand; Q = S2- or Se2-)

The present work introduces a simple, electrostatically driven approach to engineered nanomaterial built from the highly cytotoxic [Au₂L₂]²⁺ complex (Au₂, L = 1,5-bis(p-tolyl)-3,7-bis(pyridine-2-yl)-1,5-diaza-3,7-diphosphacyclooctane (PNNP) ligand) and the pH-sensitive red-emitting [{Re₆Q₈}(OH)₆]^4- (Re₆-Q, Q = S^2- or Se^2-) cluster units. The protonation/deprotonation of the Re₆-Q unit is a prerequisite for the pH-triggered assembly of Au₂ and Re₆-Q into Au₂Re₆-Q colloids, exhibiting disassembly in acidic (pH = 4.5) conditions modeling a lysosomal environment. The counter-ion effect of polyethylenimine causes the release of Re₆-Q units from the colloids, while the binding with lysozyme restricts their protonation in acidified conditions. The enhanced luminescence response of Re₆-S on the disassembly of Au₂Re₆-S colloids in the lysosomal environment allows us to determine their high lysosomal localization extent through the colocalization assay, while the low luminescence of Re₆-Se units in the same conditions allows us to reveal the rapture of the lysosomal membrane through the use of the Acridine Orange assay. The lysosomal pathway of the colloids, followed by their endo/lysosomal escape, correlates with their cytotoxicity being on the same level as that of Au₂ complexes, but the contribution of the apoptotic pathway differentiates the cytotoxic effect of the colloids from that of the Au₂ complex arisen from the necrotic processes.

Surface modification of silica nanoparticles by hexarhenium anionic cluster complexes for pH-sensing and staining of cell nuclei

The surface deposition of luminescent anionic cluster complex [{Re₆S₈}(OH)₆]^4- advantages to the design and synthesis of composite luminescent silica nanoparticles (SNs) for intracellular imaging and sensing, while the encapsulation of the cluster units into SNs lacks for efficient luminescence. The deposition of the Re₆ clusters resulted from their assembly at the silica surface functionalized by amino-groups provides the synthetic route for the composite SNs with bright cluster-centered luminescence invariable in pH range from 4.0 to 12.0. The pH-dependent supramolecular assembly of the cluster units with polyethyleneimine (PEI) at the silica surface is an alternative route for the synthesis of the composite SNs with high cluster-centered luminescence sensitive to pH-changes within 4.0-6.0. The sensitivity derives from the pH-driven conformational changes of PEI chains resulting in the release of the clusters from the PEI-based confinement under the acidification within pH 6.0-4.0. The potential of the composite SNs in cellular contrasting has been also revealed by the cell viability and flow cytometry measurements. It has been found that the PEI-supported embedding of the cluster units facilitates cell internalization of the composite SNs as well as results in specific intracellular distribution manifested by efficient staining of the cell nuclei in the confocal images.

Supraamphiphilic Systems Based on Metallosurfactant and Calix[4]resorcinol: Self-Assembly and Drug Delivery Potential

Metallic amphiphiles are used as building blocks in the construction of nanoscale superstructures, where the hydrophobic effects induce the self-assembly of the nanoparticles of interest. However, the influence of synergizing multiple chemical interactions on an effective design of these structures mostly remains an open question. In this regard, supraamphiphilic systems based on flexible surfactant molecules and rigid macrocycles are being actively developed, but there are few works on the interaction between metallosurfactants and macrocycles. In the present work, the self-assembly and biological properties of a metallosurfactant with calixarene were studied for the first time. The metallosurfactant, a complex between lanthanum nitrate and two 4-aza-1-hexadecylazoniabicyclo[2.2.2]octane bromide units, and calix[4]resorcinol containing sulfonate groups on the upper rim were used to form a novel supraamphiphilic composition. The system formed was studied using a variety of physicochemical methods, including spectrophotometry, NMR, XRF, and dynamic and electrophoretic light scattering. It was found that the most optimal tetraanionic calix[4]resorcinol to dicationic metallosurfactant molar ratio, leading to mixed aggregation upon ion pair complexation, is 2:3. The mixed aggregates formed in the pentamolar concentration range were able to encapsulate hydrophilic substrates, including the anticancer drug cisplatin, the pure form of which is more cytotoxic toward healthy cells than toward diseased cells. Interestingly, the drug loaded into the macrocycle-metallosurfactant particles was less cytotoxic to a healthy Chang liver cell line and more cytotoxic to tumor M-HeLa cells. This selectivity depends on the amount of cisplatin added. The more drug is added to the macrocycle-metallosurfactant composition, the greater the biological activity against cancer cells. Taking into account that the appearance of resistance of cancer cells to drugs, especially to cisplatin, is one of the most important problems in treatment, the results of this work envisage the potential application of a mixed macrocycle-metallosurfactant system for the design of therapeutic cisplatin compositions.

Synthetic Tuning of CoII-Doped Silica Nanoarchitecture Towards Electrochemical Sensing Ability

The present work introduces both synthesis of silica nanoparticles doped with CoII ions by means of differently modified microemulsion water-in-oil (w/o) and Stöber techniques and characterization of the hybrid nanoparticles (CoII@SiO2) by TEM, DLS, XRD, ICP-EOS, SAXS, UV-Vis, and UV-Vis/DR spectroscopy and electrochemical methods. The results reveal the lack of nanocrystalline dopants inside the hybrid nanoparticles, as well as no ligands, when CoII ions are added to the synthetic mixtures as CoII(bpy)3 complexes, thus pointing to coordination of CoII ions with Si-O- groups as main driving force of the doping. The UV-Vis/DR spectra of CoII@SiO2 in the range of d-d transitions indicate that Stöber synthesis in greater extent than the w/o one stabilizes tetrahedral CoII ions versus the octahedral ions. Both cobalt content and homogeneity of the CoII distribution within CoII@SiO2 are greatly influenced by the synthetic technique. The electrochemical behavior of CoII@SiO2 is manifested by one oxidation and two reduction steps, which provide the basis for electrochemical response on glyphosate and HP(O)(OEt)2 with the LOD = 0.1 μM and the linearity within 0.1-80 μM. The Stöber CoII@SiO2 are able to discriminate glyphosate from HP(O)(OEt)2, while the w/o nanoparticles are more efficient but nonselective sensors on the toxicants.

Supramolecular assembly of calix[4]resorcinarenes and chitosan for the design of drug nanocontainers with selective effects on diseased cells

Effective delivery systems for anticancer drugs were prepared through the self-assembly of calix[4]resorcinarenes and chitosan in an aqueous medium.

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.

Self-assembly of Gd3+-bound keplerate polyanions into nanoparticles as a route for the synthesis of positive MRI contrast agents. Impact of the structure on the magnetic relaxivity

The present work introduces Gd3+ complexes with giant keplerate polyanions as a promising basis for MRI contrast agents. The impact of Gd3+ binding with different building blocks of keplerates on the magnetic relaxivity of the complexes is revealed by comparative study of the keplerates [{Mo6O21}12{Mo2O4(OAc)}30]42-, [{Mo6O21}12{Mo2O4(HPO4)}30]72-, and [{Mo6O21}12{Mo2O2S2(OAc)}30]42-. Unprecedentedly high longitudinal and transverse relaxivity values (up to 250 and 300 mM-1 s-1 correspondingly) are achieved for the keplerates possessing edl{Mo2O4(OAc)} and {Mo2O4(HPO42-)} moieties under their 1 : 1 complex formation with Gd3+. The transformation of the external pores from Mo9O9 to Mo9O6S3 in the {Mo2O2S2(OAc)}-keplerate and an increase in the Gd3+-to-keplerate ratio are the factors that decrease the relaxivity. The rapid degradation of the free keplerates in aqueous solutions restricts the use of the Gd3+-bound keplerates with 1 : 1 stoichiometry as MRI contrast agents. In this work, the optimized stoichiometry of the complexes, their self-assembly into ultra-small nanoparticles and their hydrophilic coating by a triblock copolymer are highlighted as tools for increasing both the colloid and chemical stability of the keplerate complexes. Optimal keplerate compositions have been identified to achieve a compromise of low cytotoxicity and high stability; these Gd3+-bound keplerates exhibit longitudinal and transverse relaxivity values (95 and 114 mM-1 s-1, respectively), well within the region of interest for MRI techniques.

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.

Tuning magnetic relaxation properties of "hard cores" in core-shell colloids by modification of "soft shell"

The present work introduces an impact of polyelectrolyte-based hydrophilic shell on magnetic relaxivity and luminescence of hard cores built from isostructural complexes of Tb(III) and Gd(III) in the core-shell aqueous colloids. Microscopic and scattering techniques reveal "plum pudding" morphology of the colloids, where polyelectrolyte-coated ultrasmall (<5nm) hard cores form aggregates in aqueous solutions. Interaction of bovine serum albumin (BSA) with the colloids provides a tool to modify the polyelectrolyte-based shell, which is the reason for the improvement in both aggregation behavior of the colloids and their relaxivity. The modification of the hydrophilic polyelectrolyte-based shell enables to tune the longitudinal relaxivity from 5.9 to 23.3mM^-1s^-1 at 0.47T. This tendency is the reason for significant improvement of contrasting effect of the colloids in T₁- and T₂-weighted images obtained by whole body scanner at 1.5T. High contrasting effect of the colloids, together with low cytotoxicity towards Wi-38 diploid human cells makes them promising MRI contrast agents.

High performance magneto-fluorescent nanoparticles assembled from terbium and gadolinium 1,3-diketones

Polyelectrolyte-coated nanoparticles consisting of terbium and gadolinium complexes with calix[4]arene tetra-diketone ligand were first synthesized. The antenna effect of the ligand on Tb(III) green luminescence and the presence of water molecules in the coordination sphere of Gd(III) bring strong luminescent and magnetic performance to the core-shell nanoparticles. The size and the core-shell morphology of the colloids were studied using transmission electron microscopy and dynamic light scattering. The correlation between photophysical and magnetic properties of the nanoparticles and their core composition was highlighted. The core composition was optimized for the longitudinal relaxivity to be greater than that of the commercial magnetic resonance imaging (MRI) contrast agents together with high level of Tb(III)-centered luminescence. The tuning of both magnetic and luminescent output of nanoparticles is obtained via the simple variation of lanthanide chelates concentrations in the initial synthetic solution. The exposure of the pheochromocytoma 12 (PC 12) tumor cells and periphery human blood lymphocytes to nanoparticles results in negligible effect on cell viability, decreased platelet aggregation and bright coloring, indicating the nanoparticles as promising candidates for dual magneto-fluorescent bioimaging.

Nanoscale hydrophilic colloids with high relaxivity and low cytotoxicity based on Gd(iii) complexes with Keplerate polyanions

Efficient hydrophilic stabilization of Gd(iii) complexes with Keplerate polyanions for high relaxivity, colloid stability and low cytotoxicity.