Directional growth of iron oxide nanowires on a vicinal copper surface.

Single-crystal magnetic nanostructures with well-defined shapes attract lots of interest due to their potential applications in magnetic and spintronic devices. However, development of methods allowing controlling their mutual crystallographic and geometric orientation constitutes a significant scientific challenge. One of the routes for obtaining such structures is to grow the materials epitaxially on naturally-structured supports, such as vicinal surfaces of single-crystal substrates. Iron oxides are among the most well-known magnetic materials which, depending on the phase, may exhibit ferro/ferri- or antiferromagnetic ordering. We have grown iron oxide nanowires on a Cu(410) single-crystal substrate faceted with molecular oxygen. Scanning tunneling microscopy and low energy electron diffraction revealed that the oxide grows in the [111] direction, along the step edges of the substrate and rotated by ±15° with respect to the [010] direction of copper atomic terraces (so that the the growing elongated structures are orientated parallel to each other). Notably, x-ray photoelectron spectroscopy confirmed that the nanowires represent the ferrimagneticγ-Fe2O3(maghemite) iron oxide phase, while micromagnetic simulations indicated that the wires are single-domain, with the easy magnetization axis orientated in-plane and along the long axis of the wire.

SARS-CoV-2 Virus-like Particles with Plasmonic Au Cores and S1-Spike Protein Coronas.

The COVID-19 pandemic has stimulated the scientific world to intensify virus-related studies aimed at the development of quick and safe ways of detecting viruses in the human body, studying the virus-antibody and virus-cell interactions, and designing nanocarriers for targeted antiviral therapies. However, research on dangerous viruses can only be performed in certified laboratories that follow strict safety procedures. Thus, developing deactivated virus constructs or safe-to-use virus-like objects, which imitate real viruses and allow performing virus-related studies in any research laboratory, constitutes an important scientific challenge. Such species, called virus-like particles (VLPs), contain instead of capsids with viral DNA/RNA empty or synthetic cores with real virus proteins attached to them. We have developed a method for the preparation of VLPs imitating the virus responsible for the COVID-19 disease: the SARS-CoV-2. The particles have Au cores surrounded by "coronas" of S1 domains of the virus's spike protein. Importantly, they are safe to use and specifically interact with SARS-CoV-2 antibodies. Moreover, Au cores exhibit localized surface plasmon resonance (LSPR), which makes the synthesized VLPs suitable for biosensing applications. During the studies, the effect allowed us to visualize the interaction between the VLPs and the antibodies and identify the characteristic vibrational signals. What is more, additional functionalization of the particles with a fluorescent label revealed their potential in studying specific virus-related interactions. Notably, the universal character of the developed synthesis method makes it potentially applicable for fabricating VLPs imitating other life-threatening viruses.

Magnetic patterning of Co/Ni layered systems by plasma oxidation.

We studied the structural, chemical, and magnetic properties of Ti/Au/Co/Ni layered systems subjected to plasma oxidation. The process results in the formation of NiO at the expense of metallic Ni, as clearly evidenced by X-ray photoelectron spectroscopy, while not affecting the surface roughness and grain size of the Co/Ni bilayers. Since the decrease of the thickness of the Ni layer and the formation of NiO increase the perpendicular magnetic anisotropy, oxidation may be locally applied for magnetic patterning. Using this approach, we created 2D heterostructures characterized by different combinations of magnetic properties in areas modified by plasma oxidation and in the regions protected from oxidation. As plasma oxidation is an easy to use, low cost, and commonly utilized technique in industrial applications, it may constitute an improvement over other magnetic patterning methods.

Ammonium Gemini Surfactants Form Complexes with Model Oligomers of siRNA and dsDNA.

Dimeric cationic surfactants (gemini-type) are a group of amphiphilic compounds with potential use in gene therapy as effective carriers for nucleic acid transfection (i.e., siRNA, DNA, and plasmid DNA). Our studies have shown the formation of lipoplexes composed of alkanediyl-α,ω-bis[(oxymethyl)dimethyldodecylammonium] chlorides and selected 21-base-pair nucleic acid (dsDNA and siRNA) oligomers. To examine the structure and physicochemical properties of these systems, optical microscopy, circular dichroism spectroscopy (CD), small-angle X-ray scattering of synchrotron radiation (SR-SAXS), and agarose gel electrophoresis (AGE) were used. The lengths of spacer groups of the studied surfactants had a significant influence on the surfactants' complexing properties. The lowest charge ratio (p/n) at which stable lipoplexes were observed was 1.5 and the most frequently occurring microstructure of these lipoplexes were cubic and micellar phases for dsDNA and siRNA, respectively. The cytotoxicity tests on HeLa cells indicated the non-toxic concentration of surfactants to be at approximately 10 µM. The dicationic gemini surfactants studied form complexes with siRNA and dsDNA oligomers; however, the complexation process is more effective towards siRNA. Therefore these systems could be applied as transfection systems for therapeutic nucleic acids.

Structural characterization of transfection nanosystems based on tricationic surfactants and short double stranded oligonucleotides.

For several years cationic surfactants have been the subjects of extensive studies as potential transgene carriers to be used in gene therapy. We report the formation of stable complexes between 21 base pairs oligonucleotides - siRNA, enhancing DMPK gene, and dsDNA and two tricationic surfactants (1,2,3-propanetri[oxymethyl-3-(1-dodecylimidazolium)]chloride and 1,2,3-propanetri[(oxymethyl)dimethyldodecylammonium]chloride. Structural studies by SAXS and TEM have shown that the dominant structure of the obtained lipoplexes is based on hexagonal, lamellar and cubic phases, packed in highly ordered aggregates. It has been established that tricationic surfactants can be used as siRNA carriers in gene therapy.

Structure and conformational dynamics of DMPC/dicationic surfactant and DMPC/dicationic surfactant/DNA systems.

Amphiphilic dicationic surfactants, known as gemini surfactants, are currently studied for gene delivery purposes. The gemini surfactant molecule is composed of two hydrophilic "head" groups attached to hydrophobic chains and connected via molecular linker between them. The influence of different concentrations of 1,5-bis (1-imidazolilo-3-decyloxymethyl) pentane chloride (gemini surfactant) on the thermotropic phase behaviour of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayers with and without the presence of DNA was investigated using Fourier transformed infrared (FTIR) and circular dichroism (CD) spectroscopies, small angle scattering of synchrotron radiation and differential scanning calorimetry. With increasing concentration of surfactant in DMPC/DNA systems, a disappearance of pretransition and a decrease in the main phase transition enthalpy and temperature were observed. The increasing intensity of diffraction peaks as a function of surfactant concentration also clearly shows the ability of the surfactant to promote the organisation of lipid bilayers in the multilayer lamellar phase.