Preparation and fluorescence properties of fluorophore-labeled avidin–biotin system immobilized on Fe3O4 nanoparticles through functional indolequinone linker

Two Color Imaging of Different Hypoxia Levels in Cancer Cells

Hypoxia (low oxygen levels) occurs in a range of biological contexts, including plants, bacterial biofilms, and solid tumors; it elicits responses from these biological systems that impact their survival. For example, conditions of low oxygen make treating tumors more difficult and have a negative impact on patient prognosis. Therefore, chemical probes that enable the study of biological hypoxia are valuable tools to increase the understanding of disease-related conditions that involve low oxygen levels, ultimately leading to improved diagnosis and treatment. While small-molecule hypoxia-sensing probes exist, the majority of these image only very severe hypoxia (<1% O₂) and therefore do not give a full picture of heterogeneous biological hypoxia. Commonly used antibody-based imaging tools for hypoxia are less convenient than small molecules, as secondary detection steps involving immunostaining are required. Here, we report the synthesis, electrochemical properties, photophysical analysis, and biological validation of a range of indolequinone-based bioreductive fluorescent probes. We show that these compounds image different levels of hypoxia in 2D and 3D cell cultures. The resorufin-based probe 2 was activated in conditions of 4% O₂ and lower, while the Me-Tokyo Green-based probe 4 was only activated in severe hypoxia─0.5% O₂ and less. Simultaneous application of these compounds in spheroids revealed that compound 2 images similar levels of hypoxia to pimonidazole, while compound 4 images more extreme hypoxia in a manner analogous to EF5. Compounds 2 and 4 are therefore useful tools to study hypoxia in a cellular setting and represent convenient alternatives to antibody-based imaging approaches.

An Innovative Sandwich Type Biosensor towards Sensitive and Selective Monitoring of 2-Arachidonoylglycerol in Human Plasma Samples Using P(β-CD)-AuNPs-DDT as Amplificant Agent: A New Immuno-Platform for the Recognition of Endocannabinoids in Real Samples

In this work, 2-AG was successfully detected in human plasma samples using a new sandwich-type electrochemical immune device based on poly-β-cyclodextrin P(β-CD) functionalized with AuNPs-DDT and toluidine blue. The P(β-CD) ensured the bioactivity and stability of the immobilized 2-AG antibody by providing a broad surface for the efficient immobilization of the biotinylated antibody. To complete the top section of the immunosensor (reporter), an HRP-conjugated antibody of 2-AG (secondary antibody (Ab2)) was attached to the surface of a glassy carbon electrode (GCE) modified by P(β-CD), as well as a primarily biotinylated antibody (Ab1). The biosensor fabrication process was monitored using field-emission scanning electron microscope (FE-SEM) and EDS methods. Using the differential pulse voltammetry technique, the immunosensor was utilized for detection of 2-AG in real samples. The suggested interface increased the surface area, which allowed for the immobilization of a large quantity of anti-2-AG antibody while also improving biocompatibility, stability, and electrical conductivity. Finally, the suggested immunosensor’s limit of quantitation was determined to be 0.0078 ng/L, with a linear range of 0.0078 to 1.0 ng/L. The results showed that the suggested bioassay can be utilized for diagnosis of 2-AG in clinical samples as a unique and ultrasensitive electrochemical biodevice.

Pharmacokinetics of magnetic iron oxide nanoparticles for medical applications

Magnetic iron oxide nanoparticles (MNPs) have been under intense investigation for at least the last five decades as they show enormous potential for many biomedical applications, such as biomolecule separation, MRI imaging and hyperthermia. Moreover, a large area of research on these nanostructures is concerned with their use as carriers of drugs, nucleic acids, peptides and other biologically active compounds, often leading to the development of targeted therapies. The uniqueness of MNPs is due to their nanometric size and unique magnetic properties. In addition, iron ions, which, along with oxygen, are a part of the MNPs, belong to the trace elements in the body. Therefore, after digesting MNPs in lysosomes, iron ions are incorporated into the natural circulation of this element in the body, which reduces the risk of excessive storage of nanoparticles. Still, one of the key issues for the therapeutic applications of magnetic nanoparticles is their pharmacokinetics which is reflected in the circulation time of MNPs in the bloodstream. These characteristics depend on many factors, such as the size and charge of MNPs, the nature of the polymers and any molecules attached to their surface, and other. Since the pharmacokinetics depends on the resultant of the physicochemical properties of nanoparticles, research should be carried out individually for all the nanostructures designed. Almost every year there are new reports on the results of studies on the pharmacokinetics of specific magnetic nanoparticles, thus it is very important to follow the achievements on this matter. This paper reviews the latest findings in this field. The mechanism of action of the mononuclear phagocytic system and the half-lives of a wide range of nanostructures are presented. Moreover, factors affecting clearance such as hydrodynamic and core size, core morphology and coatings molecules, surface charge and technical aspects have been described.

Review on the recent progress in the development of fluorescent probes targeting enzymes

Enzymes are very important for biological processes in a living being, performing similar or multiple tasks in and out of cells, tissues and other organisms at a particular location. The abnormal activity of particular enzyme usually caused serious diseases such as Alzheimer's disease, Parkinson's disease, cancers, diabetes, cardiovascular diseases, arthritis etc. Hence, nondestructive and real-time visualization for certain enzyme is very important for understanding the biological issues, as well as the drug administration and drug metabolism. Fluorescent cellular probe-based enzyme detectionin vitroandin vivohas become broad interest for human disease diagnostics and therapeutics. This review highlights the recent findings and designs of highly sensitive and selective fluorescent cellular probes targeting enzymes for quantitative analysis and bioimaging.

In Vitro and in Vivo Visualization and Trapping of Fluorescent Magnetic Microcapsules in a Bloodstream

Remote navigation and targeted delivery of biologically active compounds is one of the current challenges in the development of drug delivery systems. Modern methods of micro- and nanofabrication give us new opportunities to produce particles and capsules bearing cargo to deploy and possess magnetic properties to be externally navigated. In this work we explore multilayer composite magnetic microcapsules as targeted delivery systems in vitro and in vivo studies under natural conditions of living organism. Herein, we demonstrate magnetic addressing of fluorescent composite microcapsules with embedded magnetite nanoparticles in blood flow environment. First, the visualization and capture of the capsules at the defined blood flow by the magnetic field are shown in vitro in an artificial glass capillary employing a wide-field fluorescence microscope. Afterward, the capsules are visualized and successfully trapped in vivo into externally exposed rat mesentery microvessels. Histological analysis shows that capsules infiltrate small mesenteric vessels whereas large vessels preserve the blood microcirculation. The effect of the magnetic field on capsule preferential localization in bifurcation areas of vasculature, including capsule retention at the site once external magnet is switched off is discussed. The research outcome demonstrates that microcapsules can be effectively addressed in a blood flow, which makes them a promising delivery system with remote navigation by the magnetic field.

A coiled-coil strategy for the directional display of multiple proteins on the surface of iron oxide nanoparticles

Utilization of a coiled-coil strategy for the display of multiple proteins on nanoparticles under physiological conditions.

Microwave-driven enzyme deactivation using imidazolium salt-presenting silica nanoparticles

Thermal enzyme deactivation by the imidazolium-presenting silica nanoparticles with the microwave irradiation is presented in this manuscript. The modified nanoparticles were synthesized, and it was observed that the modified nanoparticles can be a heat source in the buffer under the weak-power microwave irradiation. Finally, based on the heat-generating ability of these nanoparticles, deactivation of glutathione reductase and alkaline phosphatase with the modified nanoparticles were demonstrated.

Regulation of responsiveness of phosphorescence toward dissolved oxygen concentration by modulating polymer contents in organic-inorganic hybrid materials

Platinum(II) octaethylporphyrin (PtOEP)-loaded organic-inorganic hybrids were obtained via the microwave-assisted sol-gel condensation with methyltrimethoxysilane and poly(vinylpyrrolidone). From transparent and homogeneous hybrid films, the strong phosphorescence from PtOEP was observed. Next, the resulting hybrids were immersed in the aqueous buffer, and the emission intensity was monitored by changing the dissolved oxygen level in the buffer. When the hybrid with relatively-higher amount of the silica element, the strong phosphorescence was observed even under the aerobic conditions. In contrast, the emission from the hybrids with lower amounts of the silica element was quenched under the hypoxic conditions. This is, to the best of our knowledge, the first example to demonstrate that the responsiveness of the phosphorescence intensity of PtOEP in hybrid films to the dissolved oxygen concentration in water can be modulated by changing the percentage of the contents in the material.

Multifunctional nanoparticles for dual imaging

For imaging with different modalities, labels, which provide contrast for all modalities, are required. Colloidal nanoparticles composed out of an inorganic core and a polymer shell offer progress in this direction. Both, the core and the polymer shell, can be synthesized to be fluorescent, magnetic, or radioactive. When different cores are combined with different polymer shells, different types of particles for dual imaging can be obtained, as for example, fluorescent cores with radioactive polymer shells. Properties and perspectives of such nanoparticles for multimodal imaging are discussed.

Preparation of highly fluorescent magnetic nanoparticles for analytes-enrichment and subsequent biodetection

Bifunctional nanoparticles with highly fluorescence and decent magnetic properties have been widely used in biomedical application. In this study, highly fluorescent magnetic nanoparticles (FMNPs) with uniform size of ca. 40 nm are prepared by encapsulation of both magnetic nanoparticles (MNPs) and shell/core quantum dots (QDs) with well-designed shell structure/compositions into silica matrix via a one-pot reverse microemulsion approach. The spectral analysis shows that the FMNPs hold high fluorescent quantum yield (QY). The QYs and saturation magnetization of the FMNPs can be regulated by varying the ratio of the encapsulated QDs to MNPs. Moreover, the surface of the FMNPs can be modified to offer chemical groups for antibody conjugation for following use in target-enrichment and subsequent fluorescent detection. The in vitro immunofluorescence assay and flow cytometric analysis indicate that the bifunctional FMNPs-antibody bioconjugates are capable of target-enrichment, magnetic separation and can also be used as alternative fluorescent probes on flow cytometry for biodetection.