Manganese ferrite nanoparticles display interesting features in bioimaging and catalytic therapies. They have been recently used in theranostics as contrast agents in magnetic resonance imaging (MRI), and as catalase‐mimicking nanozymes for hypoxia alleviation. These promising applications encourage the development of novel synthetic procedures to enhance the bioimaging and catalytic properties of these nanomaterials simultaneously. Herein, a cost‐efficient synthetic microwave method is developed to manufacture ultrasmall manganese ferrite nanoparticles as advanced multimodal contrast agents in MRI and positron emission tomography (PET), and improved nanozymes. Such a synthetic method allows doping ferrites with Mn in a wide stoichiometric range (MnxFe3‐xO4, 0.1 ≤ x ≤ 2.4), affording a library of nanoparticles with different magnetic relaxivities and catalytic properties. These tuned magnetic properties give rise to either positive or dual‐mode MRI contrast agents. On the other hand, higher levels of Mn doping enhance the catalytic efficiency of the resulting nanozymes. Finally, through their intracellular catalase‐mimicking activity, these ultrasmall manganese ferrite nanoparticles induce an unprecedented tumor growth inhibition in a breast cancer murine model. All of these results show the robust characteristics of these nanoparticles for nanobiotechnological applications.
Lanthanide-doped upconverting nanoparticles (UCNPs) transform near infrared light (NIR) into higher-energy UV and visible light by multiphotonic processes. Owing to such unique feature, UCNPs have found application in optical imaging and have been investigated for the NIR light activation of prodrugs, including transition metal complexes of interest in photochemotherapy. Besides, UCNPs also function as magnetic resonance imaging (MRI) contrast agents and positron emission tomography (PET) probes when labelled with radionuclides such as 18F. In this contribution, we report on a new series of phosphonate-functionalized NaGdF4:Yb,Er UCNPs that show affinity for hydroxyapatite (inorganic constituent of bones), and we discuss their potential as bone targeting multimodal (MRI/PET) imaging agents. In vivo biodistribution studies of 18F-labelled NaGdF4:Yb,Er UCNPs in rats indicate that surface functionalization with phosphonates favours the accumulation of nanoparticles in bones over time. PET results reveal leakage of 18F− for phosphonate-functionalized NaGdF4:Yb,Er and control nanomaterials. However, Gd was detected in the femur for phosphonate-capped UCNPs by ex vivo analysis using ICP-MS, corresponding to 6–7% of the injected dose.
An undecamer oligonucleotide probe
based on a pair of deoxythymidines
flanked by several modified nucleotides is a specific and highly efficient
biosensor for micrococcal nuclease (MNase), an endonuclease produced
by
Staphylococcus aureus
. Herein, the
interaction mode and cleavage process on such oligonucleotide probes
are identified and described for the first time. Also, we designed
truncated pentamer probes as the minimum-length substrates required
for specific and efficient biosensing. By means of computational (virtual
docking) and experimental (ultra-performance liquid chromatography–mass
spectrometry and matrix-assisted laser desorption ionization time-of-flight)
techniques, we perform a sequence/structure–activity relationship
analysis, propose a catalytically active substrate–enzyme complex,
and elucidate a novel two-step phosphodiester bond hydrolysis mechanism,
identifying the cleavage sites and detecting and quantifying the resulting
probe fragments. Our results unravel a picture of both the enzyme–biosensor
complex and a two-step cleavage/biosensing mechanism, key to the rational
oligonucleotide design process.
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