A dual lanthanide probe suitable for optical (Tb3+ luminescence) and magnetic resonance imaging (Gd3+ relaxometry)

New polyaminocarboxylate macrocycles containing phenolate binding units: synthesis, luminescent and relaxometric properties of their lanthanide complexes

The synthesis of two new polyaminocarboxylate macrocycles incorporating one or two intracyclic phenol units (H₄L¹ and H₈L², respectively) is described. The 12-membered H₄L¹ macrocycle leads to soluble and stable mononuclear Ln^III complexes of [(L¹)Ln(H₂O)₂]^- composition (Ln = Eu, Tb and Gd) in aqueous solutions. In Tris buffer (pH 7.4), the [(L¹)Tb(H₂O)₂]^- complex displays a suitable efficiency for sensitized emission (η_sens = 48%) and a high luminescence quantum yield (Φ = 22%), which is worthy of note for a bis-hydrated terbium complex. Besides, luminescence experiments show that bidentate endogenous anions (citrate, carbonate, and phosphate) do not displace the two inner-sphere water molecules of this complex. In contrast, the possible presence of LMCT states causes the europium complex to be weakly luminescent. The [(L¹)Gd(H₂O)₂]^- complex is characterized by high relaxivity (r = 7.2 s^-1 mM^-1 at 20 MHz) and a very short water residence time of the coordinated water molecules (τ = 9 ns), promising values for the realisation of macromolecular systems with high relaxivities. Thus, the Tb and Gd complexes of the H₄L¹ macrocycle exhibit several improvements in terms of luminescent (lower excitation energy, higher brightness) and relaxometric (shorter τ_M) properties compared to the corresponding LnPCTA complexes, where a phenol moiety substitutes a pyridine ring. On the other hand, the 24-membered H₈L² macrocycle including two phenol units in its structure leads to dinuclear complexes of [(L²)Ln₂]^2- composition. Its terbium complex shows a long luminescence lifetime (2 ms) and a high quantum yield (43%) in aqueous solutions, making this compound a new promising candidate for time-resolved applications.

La(III) complex involving the O,N-donor environment of quinazoline-4(3H)-one Schiff's base and their antimicrobial attributes against methicillin-resistant Staphylococcus aureus (MRSA)

The incidence of methicillin-resistant Staphylococcus aureus increased during the past few decades, so there is an urgent need of new antimicrobial agents if public health is concerned. Though the Schiff's bases and La(III) complex have enormous biological activity, but less attention was given in their synthesis. In the present investigation, we synthesized a new (E)-3-((2-hydroxynaphthalen-1-yl) methyleneamino)-2-methylquinazoline-4(3H)-one HNMAMQ Schiff's base by the condensation of 3-(2-aminophenyl) quinazolin-2-methyl-4(3H)-one and 2-hydroxy-1-naphthaldehyde. The Schiff's base HNMAMQ and its La(III) complex were characterized by elemental analyses, IR, NMR, mass spectra, and thermal studies. The newly synthesized Schiff's base HNMAMQ and its La(III) complex were evaluated for their antimicrobial activity against methicillin-resistant Staphylococcus aureus isolated from the Gulbarga region in India. The Schiff's base HNMAMQ and its La(III) complex showed good antimicrobial activity and thus represents a potential new drug of choice.

Synthesis, Characterization, and Physicochemical Studies of Mixed Ligand Complexes of Inner Transition Metals with Lansoprazole and Cytosine

Few complexes of inner transition metals [Th(IV), Ce(IV), Nd(III), Gd(III)] have been synthesized by reacting their metal salts with lansoprazole, 2-([3-methyl-4-(2,2,2-trifluoroethoxy)pyridin-2-yl]methylsulfinyl)-1H-benzoimidazole and cytosine. All the complexes were synthesized in ethanolic medium. The yield percentage rangs from 80 to 90%. The complexes are coloured solids. The complexes were characterized through elemental analyses, conductance measurements, and spectroscopic methods (FT IR, FAB Mass,1H NMR and UV). An IR spectrum indicates that the ligand behaves as bidentate ligands. The metal complexes have been screened for their antifungal activity towardsAspergillus nigerfungi. The interaction of inner transition metals with lansoprazole, in presence of cytosine, has also been investigated potentiometrically at two different temperatures26±1°C and36±1°C and at 0.1 M (KNO3) ionic strength. The stability constants of ternary complexes indicate the stability order as Th(IV) < Ce(IV) < Gd(III) < Nd(III).logKvalues obtained are positive and suggest greater stabilization of ternary complexes. The values of thermodynamic parameters (free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) are also calculated.

Lanthanide-DTPA grafted silica nanoparticles as bimodal-imaging contrast agents

The design and synthesis of a combined MRI-optical probe for bio-imaging are reported. The materials studied join the properties of lanthanide (Ln(3+)) complexes and nanoparticles (NPs), offering an excellent solution for bimodal imaging. The hybrid SiO(2)@APS/DTPA:Gd:Ln (Ln = Eu(3+) or Tb(3+)) (APS: 3-aminopropyltriethoxysilane, DTPA: diethylenetriamine pentaacetic acid) system increases the payload of the active magnetic centre (Gd(3+)) and introduces a Ln(3+) long-life excited state (Eu(3+): 0.35 ± 0.02 ms, Tb(3+): 1.87 ± 0.02 ms), with resistance to photobleaching and sharp emission bands. The Eu(3+) ions reside in a single low-symmetry site. Although the photoluminescence emission is not influenced by the simultaneous presence of Gd(3+) and Eu(3+), a moderate r(1) increase and a larger enhancement of r(2) are observed, particularly at high fields, due to susceptibility effects on r(2). The presence of Tb(3+) instead of Eu(3+) further raises r(1) but decreases r(2). These values are constant over a wide (5-13) pH range, indicating the paramagnetic NPs stability and absence of leaching. The uptake of NPs by living cells is fast and results in an intensity increase in the T(1)-weighted MRI images. The optical properties of the NPs in cellular pellets are also studied, confirming their potential as bimodal imaging agents.

Cell-permeable Ln(III) chelate-functionalized InP quantum dots as multimodal imaging agents

Quantum dots (QDs) are ideal scaffolds for the development of multimodal imaging agents, but their application in clinical diagnostics is limited by the toxicity of classical CdSe QDs. A new bimodal MRI/optical nanosized contrast agent with high gadolinium payload has been prepared through direct covalent attachment of up to 80 Gd(III) chelates on fluorescent nontoxic InP/ZnS QDs. It shows a high relaxivity of 900 mM(-1) s(-1) (13 mM(-1 )s(-1) per Gd ion) at 35 MHz (0.81 T) and 298 K, while the bright luminescence of the QDs is preserved. Eu(III) and Tb(III) chelates were also successfully grafted to the InP/ZnS QDs. The absence of energy transfer between the QD and lanthanide emitting centers results in a multicolor system. Using this convenient direct grafting strategy additional targeting ligands can be included on the QD. Here a cell-penetrating peptide has been co-grafted in a one-pot reaction to afford a cell-permeable multimodal multimeric MRI contrast agent that reports cellular localization by fluorescence and provides high relaxivity and increased tissue retention with respect to commercial contrast agents.

Rational chemical design of the next generation of molecular imaging probes based on physics and biology: mixing modalities, colors and signals

In recent years, numerous in vivo molecular imaging probes have been developed. As a consequence, much has been published on the design and synthesis of molecular imaging probes focusing on each modality, each type of material, or each target disease. More recently, second generation molecular imaging probes with unique, multi-functional, or multiplexed characteristics have been designed. This critical review focuses on (i) molecular imaging using combinations of modalities and signals that employ the full range of the electromagnetic spectra, (ii) optimized chemical design of molecular imaging probes for in vivo kinetics based on biology and physiology across a range of physical sizes, (iii) practical examples of second generation molecular imaging probes designed to extract complementary data from targets using multiple modalities, color, and comprehensive signals (277 references).

Antimicrobial Study of Newly Synthesized Lanthanide(III) Complexes of 2-[2-hydroxy-3-methoxyphenyl]-3-[2-hydroxy-3-methoxybenzylamino]-1,2-dihydroquinazolin-4(3H)-one

New lanthanide(III) complexes with 2-[2-hydroxy-3-methoxyphenyl]-3-[hydroxyl-3-methoxybenzylamino]-1,2-dihydroquin- azoline-4(3H)-one (Hmpbaq) have been synthesized and characterized by elemental analysis, conductance measurements, magnetic susceptibilities, spectroscopic (IR, NMR, UV, EPR), and thermal studies. Molar conductance studies indicate 1 : 1 electrolytic behavior for these complexes. IR spectra indicate that Hmpbaq acts as a tridentate ligand coordinating through carbonyl oxygen, benzyl amine nitrogen, and deprotonated phenolic oxygen. TG and DTA studies of La(III) and Pr(III) complexes indicate the presence of two coordinated water molecules. Based on these studies, the complexes have been formulated as [La(mpbaq)₂(H₂O)₂]·NO₃, where Ln = La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Th(III), Dy(III), and Y(III). The ligand, lanthanide(III) salts, and the corresponding complexes have been simultaneously screened for their antibacterial and antifungal activities and compared with the drugs in use.

Ultrasmall mixed ferrite colloids as multidimensional magnetic resonance imaging, cell labeling, and cell sorting agents

One area that has been overlooked in the evolution of magnetic nanoparticle technology is the possibility of introducing informational atoms into the iron oxide core of the coated colloid. Introduction of suitable atoms into the iron oxide core offers an opportunity to produce a quantifiable probe, thereby adding one or more dimensions to the magnetic colloid's informational status. Lanthanide-doped iron oxide nanoparticles have been synthesized to introduce informational atoms through the formation of colloidal mixed ferrites. These colloids are designated ultrasmall mixed ferrite iron oxides (USMIOs). USMIOs containing 5 mol % europium exhibit superparamagnetic behavior with an induced magnetization of 56 emu/g Fe at 1.5 T, a powder X-ray diffraction pattern congruent with magnetite, and R1 and R2 relaxivity values of 15.4 (mM s) (-1) and 33.9 (mM s) (-1), respectively, in aqueous solution at 37 degrees C and 0.47 T. USMIO can be detected by five physical methods, combining the magnetic resonance imaging (MRI) qualities of iron with the sensitive and quantitative detection of lanthanide metals by neutron activation analysis (NA), time-resolved fluorescence (TRF), X-ray fluorescence, along with detection by electron microscopy (EM). In addition to quantitative detection using neutron activation analysis, the presence of lanthanides in the iron oxide matrix confers attractive optical properties for long-term multilabeling studies with europium and terbium. These USMIOs offer high photostability, a narrow emission band, and a broad absorption band combining the high sensitivity of time-resolved fluorescence with the high spatial resolution of MRI. USMIO nanoparticles are prepared through modifications of traditional magnetite-based iron oxide colloid synthetic methods. A 5 mol % substitution of ferric iron with trivalent europium yielded a colloid with nearly identical magnetic, physical, and chemical characteristics to its magnetite colloid parent.