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The dopaminergic neural system is a crucial part of the brain responsible for many of its functions including mood, arousal, and other roles. Dopamine is the key neurotransmitter of this system, and a determination of its level presents a demanding task needed for a deeper understanding of the processes, even pathological, involving this brain part. In this work, we present a method for a fast analysis of dopamine levels in samples of cerebrospinal fluid and mouse striatum. The method is based on a nanocomposite composed of magnetite and silver nanoparticles, whose surface is modified with iron nitriloacetic acid (Fe-NTA)-a dopamine-selective compound. The magnetic properties of this nanocomposite enable simple separation of targeted molecules from a complex matrix while the silver acts as a platform for surface-enhanced Raman scattering (SERS). Silver and magnetite nanoparticles are joined by carboxymethyl chitosan, useful in biological environments and enhancing the sensitivity due to the presence of carboxyl groups. This system reveals a good stability and reproducibility. Moreover, rapid and simple quantitative experiments show an improvement in the detection of dopamine levels in biological assays at low femtomolar concentrations. The comparative data performed with clinical samples of mouse striatum show that the developed magnetic SERS is a strong alternative to conventional high-performance liquid chromatography-mass spectrometry (HPLC-MS) with even several superior aspects including faster and cheaper analysis and no necessity of sample preconcentration or derivatization.

There are several green methods available to synthesize iron-based nanoparticles using different bio-based reducing agents. Although their useful properties in degradation of organic dyes, chlorinated organics, or arsenic have been described earlier, their characterization has been ambiguous, and further research is needed in this area. Synthesis and characterization details on iron-based nanoparticles produced by green tea extract are described in detail; characterization was carried out by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and UV−vis spectrometry followed by ecotoxicological assay. XRD and TEM analyses revealed that iron forms amorphous nanosized particles with size depending on reaction time. Moreover, low-temperature Mossbauer spectroscopy confirmed progressive reduction of Fe 3+ to Fe 2+ during the reaction. Finally, the iron(II,III) nanoparticles prepared by green tea extract (GT−Fe nanoparticles) were found to have negative ecotoxicological impacts on important aquatic organisms such as cyanobacterium (Synechococcus nidulans), alga (Pseudokirchneriella subcapitata), and even invertebrate organisms (Daphnia magna). The EC 50 values are 6.1 ± 0.5 (72 h), 7.4 ± 1.6 (72 h), and 21.9 ± 4.3 (24 h) mg of Fe per L, respectively.

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We report on new magnetic bimetallic Fe-Ag nanoparticles (NPs) which exhibit significant antibacterial and antifungal activities against a variety of microorganisms including disease causing pathogens, as well as prolonged action and high efficiency of phosphorus removal. The preparation of these multifunctional hybrids, based on direct reduction of silver ions by commercially available zerovalent iron nanoparticles (nZVI) is fast, simple, feasible in a large scale with a controllable silver NP content and size. The microscopic observations (transmission electron microscopy, scanning electron microscopy/electron diffraction spectroscopy) and phase analyses (X-ray diffraction, Mössbauer spectroscopy) reveal the formation of Fe₃O₄/γ-FeOOH double shell on a "redox" active nZVI surface. This shell is probably responsible for high stability of magnetic bimetallic Fe-Ag NPs during storage in air. Silver NPs, ranging between 10 and 30 nm depending on the initial concentration of AgNO₃, are firmly bound to Fe NPs, which prevents their release even during a long-term sonication. Taking into account the possibility of easy magnetic separation of the novel bimetallic Fe-Ag NPs, they represent a highly promising material for advanced antimicrobial and reductive water treatment technologies.

Development of methods allowing determination of even ultralow levels of immunoglobulins in various clinical samples including whole human blood and plasma is a particular scientific challenge, especially due to many essential discoveries in the fields of immunology and medicine in the past few decades. The determination of IgG is usually performed using an enzymatic approach, followed by colorimetric or fluorimetric detection. However, limitations of these methods relate to their complicated setup and stringent requirements concerning the sample purity. Here, we present a novel approach based on magnetically assisted surface enhanced Raman spectroscopy (MA/SERS), which utilizes a Fe3O4@Ag@streptavidin@anti-IgG nanocomposite with strong magnetic properties and an efficient SERS enhancement factor conferred by the Fe3O4 particles and silver nanoparticles, respectively. Such a nanocomposite offers the possibility of separating a target efficiently from a complex matrix by simple application of an external magnetic force, followed by direct determination using SERS. High selectivity was achieved by the presence of anti-IgG on the surface of silver nanoparticles coupled with their further inactivation by ethylamine. Compared to many recently developed sandwich methods, application of single nanocomposites showed many advantages, including simplicity of use, direct control of the analytic process, and elimination of errors caused by possible nonspecific interactions. Moreover, incorporation of advanced spectral processing methods led to a considerable decrease in the relative error of determination to below 5%.

Fluorescent core-shell nanohybrids with the shells derived from carbon dots and cores differing in the chemical nature and morphology were synthesized. Hybrid nanoparticles combine fluorescence with other functionalities such as magnetic response on a single platform. These hybrids can be used in various bioapplications as demonstrated with labeling of stem cells.

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