Self-Assembled Nanostructures Formation in Hybrid Metal-Mesogenic Systems

This chapter reviews the methods of supramolecular chemistry and cryochemistry to study the formation, morphological and structural properties, and possible applications of hybrid nanostructures and nanosized aggregates comprising plasmonic metals (silver and copper) and several mesogenic compounds, which exhibit different liquid crystalline mesophases—nematics, smectics, and cholesterics. Low-temperature vacuum co-condensation of reagent vapors on cooled surfaces of quartz, KBr, CaF2, or polished copper was used to synthesize hybrid nanosystems including silver and copper and long-chain mesogenic derivatives of alkylcyanobiphenyls under molecular beam conditions. Controlled thermal treatment of the samples allowed the directed formation of metal nanoparticles of definite size from 2 up to 100 nm. It was shown that the procedures of temperature treatments and molecular self-organization of different liquid crystalline phases controlled the size and morphology of nanoparticles and their aggregates, which were formed in the system. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) data of the samples show the formation of orientationally ordered structures in nematic mesophases. Formation of flat 2D aggregates was found in layered smectic mesophases. Optical absorbance spectra of silver/4-pentyl-4-cyanobiphenyl (Ag/5СВ) and copper/4-pentyl-4-cyanobiphenyl (Cu/5CB) samples encapsulated in polymer poly-para-xylylene at 300 K contained characteristic bands of plasmonic absorbance of metal nanoparticles at 420–440 nm and 560–600 nm. Rising metal concentration in the sample led to the performable growth of rod-like metal particles with anisometric ratio l/d > 20 and intensive absorbance at higher wavelengths (λ ≥ 650 nm). New hybrid nanosystems based on biomolecules of cholesterol or its heteroatomic analog thiocholesterol including nanosized silver particles of d = 5.0 ± 0.5 and d = 2.5 ± 0.5 nm, respectively, were obtained. Highly ordered 1D-, 2D-, and 3D structures containing silver nanoparticles were formed from concentrated organic sols at different support surfaces by removing the inert solvent from triple metal/ligand/solvent system and by cooling the binary metal/ligand system from isotropic state to the cholesteric liquid crystalline mesophase. The microstructure and composition of the hybrid nanosystems were characterized by FTIR, UV-Vis spectroscopy, TEM, and selected area electron diffraction (SAED). It was shown that hybrid nanosystems based on silver nanoparticles covered by a stabilizing layer of mesogenic molecules of thiocholesterol display selectivity in adsorption of optical isomers of the selected compounds

Chiral Hybrid Nanosystems and Their Biosensing Applications

The presented chapter is devoted to chiral biosensing using various metal nanostructures and their hybrid nanosystems with optically active bio- and organic molecules. Plasmonic nanosystems and nanostructures provide an excellent platform for label-free detection of molecular adsorption by detecting tiny changes in the local refractive index or amplification of light-induced processes in biomolecules. Based on recent theoretical and experimental developments in plasmon-enhanced local electric fields, we consider the main types of molecular-plasmonic hybrid systems capable of generating an amplified chiroptical signal for such applications as detecting the presence of certain biomolecules and (in some cases) determination of their orientation and higher-order structure

Magnetic Nanoparticles for Biomedical Purposes: Modern Trends and Prospects

The presented paper is a review article discussing existing synthesis methods and different applications of nanosized magnetic nanoparticles. It was shown that, in addition to the spectrum of properties typical for nanomaterials (primarily a large specific surface area and a high fraction of surface atoms), magnetic nanoparticles also possess superparamagnetic properties that contribute to their formation of an important class of biomedical functional nanomaterials. This primarily concerns iron oxides magnetite and maghemite, for which in vitro and in vivo studies have shown low toxicity and high biocompatibility in comparison with other magnetic nanomaterials. Due to their exceptional chemical, biological, and physical properties, they are widely used in various areas, such as magnetic hyperthermia, targeted drug delivery, tissue engineering, magnetic separation of biological objects (cells, bacteria, viruses, DNA, and proteins), and magnetic diagnostics (they are used as agents for MRS and immunoassay). In addition to discussing the main problems and prospects of using nanoparticles of magnetic iron oxides for advanced biomedical applications, information is also reflected on their structure, production methods, and properties

Chiral Plasmonic Biosensors

Biosensing requires fast, selective, and highly sensitive real-time detection of biomolecules using efficient simple-to-use techniques. Due to a unique capability to focus light at nanoscale, plasmonic nanostructures provide an excellent platform for label-free detection of molecular adsorption by sensing tiny changes in the local refractive index or by enhancing the light-induced processes in adjacent biomolecules. This review discusses the opportunities provided by surface plasmon resonance in probing the chirality of biomolecules as well as their conformations and orientations. Various types of chiral plasmonic nanostructures and the most recent developments in the field of chiral plasmonics related to biosensing are considered

Hybrid Nanosystems of Antibiotics with Metal Nanoparticles—Novel Antibacterial Agents

The appearance and increasing number of microorganisms resistant to the action of antibiotics is one of the global problems of the 21st century. Already, the duration of therapeutic treatment and mortality from infectious diseases caused by pathogenic microorganisms have increased significantly over the last few decades. Nanoscale inorganic materials (metals and metal oxides) with antimicrobial potential are a promising solution to this problem. Here we discuss possible mechanisms of pathogenic microorganisms’ resistance to antibiotics, proposed mechanisms of action of inorganic nanoparticles on bacterial cells, and the possibilities and benefits of their combined use with antibacterial drugs. The prospects of using metal and metal oxide nanoparticles as carriers in targeted delivery systems for antibacterial compositions are also discussed

Nanoparticles of Bioactive Metals/Metal Oxides and Their Nanocomposites with Antibacterial Drugs for Biomedical Applications

The increasing appearance of new strains of microorganisms resistant to the action of existing antibiotics is a modern problem that requires urgent decision. A promising potential solution is the use of nanoparticles of bioactive metals and their oxides as new antibacterial agents, since they are capable of affecting pathogenic microorganisms by mechanisms different from the mechanisms of action of antibiotics. Inorganic nanoparticles possess a wide spectrum of antibacterial activity. These particles can be easily conjugated with drug molecules and become carriers in targeted drug-delivery systems. This paper discusses the benefits and prospects of the application of nanoparticles from metals and metal oxides and their nanocomposites with antibacterial drugs

Metal and Metal Oxides Nanoparticles and Nanosystems in Anticancer and Antiviral Theragnostic Agents

The development of antiviral treatment and anticancer theragnostic agents in recent decades has been associated with nanotechnologies, and primarily with inorganic nanoparticles (INPs) of metal and metal oxides. The large specific surface area and its high activity make it easy to functionalize INPs with various coatings (to increase their stability and reduce toxicity), specific agents (allowing retention of INPs in the affected organ or tissue), and drug molecules (for antitumor and antiviral therapy). The ability of magnetic nanoparticles (MNPs) of iron oxides and ferrites to enhance proton relaxation in specific tissues and serve as magnetic resonance imaging contrast agents is one of the most promising applications of nanomedicine. Activation of MNPs during hyperthermia by an external alternating magnetic field is a promising method for targeted cancer therapy. As therapeutic tools, INPs are promising carriers for targeted delivery of pharmaceuticals (either anticancer or antiviral) via magnetic drug targeting (in case of MNPs), passive or active (by attaching high affinity ligands) targeting. The plasmonic properties of Au nanoparticles (NPs) and their application for plasmonic photothermal and photodynamic therapies have been extensively explored recently in tumor treatment. The Ag NPs alone and in combination with antiviral medicines reveal new possibilities in antiviral therapy. The prospects and possibilities of INPs in relation to magnetic hyperthermia, plasmonic photothermal and photodynamic therapies, magnetic resonance imaging, targeted delivery in the framework of antitumor theragnostic and antiviral therapy are presented in this review

Cryochemical Production of Drug Nanoforms: Particle Size and Crystal Phase Control of the Antibacterial Medication 2,3-Quinoxalinedimethanol-1,4-dioxide (Dioxidine)

Increasing the effectiveness of known, well-tested drugs is a promising low-cost alternative to the search for new drug molecular forms. Powerful approaches to solve this problem are (a) an active drug particle size reduction down to the nanoscale and (b) thermodynamically metastable but kinetically stable crystal modifications of drug acquisition. The combined cryochemical method has been used for size and structural modifications of the antibacterial drug 2,3-quinoxalinedimethanol-1,4-dioxide (dioxidine). The main stage of the proposed technique includes the formation of a molecular vapor of the drug substance, combined with a carrier gas (CO2) flow, followed by a fast condensation of the drug substance and CO2 molecules on a cooled-by-liquid nitrogen surface of preparative cryostate. It was established that the molecular chemical structure of the drug substance remained unchanged during cryochemical modification; however, it led to a significant decrease of the drug particles’ size down to nanosizes and changes in the crystal structures of the solid drug nanoforms obtained. Varying carrier gas (CO2) flow led to changes in their solid phase composition. A higher dissolution rate and changes in antibacterial activity were demonstrated for cryomodified dioxidine samples in comparison to the properties of the initial pharmacopeia dioxidine