Cu2+-Complex of hydrophilic nitrogen-rich polymer dots applied as a new MRI contrast agent

Photothermal Carbon Dots Chelated Hydroxyapatite Filler: High Photothermal Conversion Efficiency and Enhancing Adhesion of Hydrogel

The synthesis of photothermal carbon/hydroxyapatite composites poses challenges due to the binding modes and relatively low photothermal conversion efficiency. To address these challenges, the calcium ions chelated by photothermal carbon dots (PTC-CDs) served as the calcium source for the synthesis of photothermal carbon dots chelated hydroxyapatite (PTC-HA) filler via the coprecipitation method. The coordination constant K and chelation sites of PTC-HA were 7.20 × 102 and 1.61, respectively. Compared to PTC-CDs, the coordination constant K and chelation sites of PTC-HA decreased by 88 and 35% due to chelating to hydroxyapatite, respectively. PTC-HA possesses fluorescence and photothermal performance with a 62.4% photothermal conversion efficiency. The incorporation of PTC-HA filler significantly enhances as high as 76% the adhesion performance of the adhesive hydrogel. PTC-HA with high photothermal conversion efficiency and enhancing adhesion performance holds promise for applications in high photothermal conversion efficiency, offering tissue adhesive properties and fluorescence capabilities to the hydrogel.

Liposomal MRI probes containing encapsulated or amphiphilic Fe(III) coordination complexes

Liposomes containing high-spin Fe(III) coordination complexes were prepared towards the production of T1 MRI probes with improved relaxivity. The amphiphilic Fe(III) complexes were anchored into the liposome with two alkyl chains to give a coordination sphere containing mixed amide and hydroxypropyl pendant groups. The encapsulated complex contains a macrocyclic ligand with three phosphonate pendants, [Fe(NOTP)]3-, which was chosen for its good aqueous solubility. Four types of MRI probes were prepared including those with intraliposomal Fe(III) complex (LipoA) alone, amphiphilic Fe(III) complex (LipoB), both intraliposomal and amphiphilic complex (LipoC) or micelles formed with amphiphilic complex. Water proton relaxivities r1 and r2 were measured and compared to a small molecule macrocyclic Fe(III) complex containing similar donor groups. Micelles of the amphiphilic Fe(III) complex had proton relaxivity values (r1 = 2.6 mM-1 s-1) that were four times higher than the small hydrophilic analog. Liposomes with amphiphilic Fe(III) complex (LipoB) have a per iron relaxivity of 2.6 mM-1 s-1 at pH 7.2, 34 °C at 1.4 T whereas liposomes containing both amphiphilic and intraliposomal Fe(III) complexes (lipoC) have r1 of 0.58 mM-1 s-1 on a per iron basis consistent with quenching of the interior Fe(III) complex relaxivity. Liposomes containing only encapsulated [Fe(NOTP)]3- have a lowered r1 of 0.65 mM-1 s-1 per iron complex. Studies show that the biodistribution and clearance of the different types liposomal nanoparticles differ greatly. LipoB is a blood pool agent with a long circulation time whereas lipoC is cleared more rapidly through both renal and hepatobiliary pathways. These clearance differences are consistent with lower stability of LipoC compared to LipoB.

Synergistic Effect of Oxygen- and Nitrogen-Containing Groups in Graphene Quantum Dots: Red Emitted Dual-Mode Magnetic Resonance Imaging Contrast Agents with High Relaxivity

Contrast agents (CAs) in magnetic resonance imaging generally involve the dissociative Gd³⁺. Because of the limited ligancy of Gd³⁺, the balance between Gd³⁺ coordination stability (reducing the concentration of dissociative Gd³⁺) and increases in the number of coordination water molecules (enhancing the relaxivity) becomes crucial. Herein, the key factor of the synergistic effect between the O- and N-containing groups of graphene quantum dots for the structural design of CAs with both high relaxivity and low toxicity was obtained. The nitrogen-doped graphene quantum dots (NGQDs) with an O/N ratio of 0.4 were selected to construct high-relaxivity magnetic resonance imaging (MRI)-fluorescence dual-mode CAs. The coordination stability of Gd³⁺ can be increased through the synergetic coordination of O- and N-containing groups. The synergetic coordination of O- and N-containing groups can result in the short residency time of the water ligand and achieve high relaxivity. The resulting CAs (called NGQDs-Gd) exhibit a high relaxivity of 32.04 mM^-1 s^-1 at 114 μT. Meanwhile, the NGQDs-Gd also emit red fluorescence (614 nm), which can enable the MRI-fluorescence dual-mode imaging as the CAs. Moreover, the bio-toxicity and tumor-targeting behavior of NGQDs-Gd were also evaluated, and NGQDs-Gd show potential in MRI-fluorescence imaging in vivo.

Coordination-Regulated Terpyridine-Mn(II) Complexes for Photodynamic Therapy Guided by Multiphoton Fluorescence/Magnetic Resonance Imaging

The synergy of multiphoton fluorescence imaging (MP-FI) and magnetic resonance imaging (MRI) provides an imaging platform with high resolution and unlimited penetration depth for early disease detection. Herein, two kinds of terpyridine-Mn(II) complexes (FD-Mn-O₂NO and FD-Mn-FD) possessing seven and six coordination modes, respectively, were designed rationally for photodynamic therapy (PDT) guided by MP-FI/MRI. The complexes obtain different multiphoton fluorescence/magnetic resonance properties by adjusting the number of terpyridine ligands. Among them, FD-Mn-FD exhibits the following superiorities: (1) The optimal three-photon excitation wavelength of FD-Mn-FD falls at 1450 nm (NIR-II), which brings high sensitivity and deep tissue penetration in MP-FI. (2) FD-Mn-FD has effective longitudinal relaxation efficiency (r₁ = 2.6 m M^-1 s^-1), which can be used for T₁-weighted MRI, overcoming the problems of limited tissue penetration depth and low spatial resolution. (3) FD-Mn-FD generates endogenous ¹O₂ under irradiation by 808 nm light, thereby enhancing the PDT effect in vitro and in vivo. To the best of our knowledge, the complex FD-Mn-FD is the first complex to guide PDT through MP-FI/MRI, providing a blueprint for accurate and effective early detection and timely treatment of the complex in the early stages of cancer.

Microwave-assisted synthesis of water-soluble Eu3+ hybrid carbon dots with enhanced fluorescence for the sensing of Hg2+ ions and imaging of fungal cells

Eu³⁺ ion hybrid carbon dots as a novel fluorescent probe for the assay of Hg²⁺ ions and cellular imaging of Fomitopsis sp.