Riboflavin Crystals with Extremely High Water Solubility.

New insights into the unique biochemical properties of riboflavin (Rf), also known as vitamin B2, are leading to the development of its use not only as a vitamin supplement but also as a potential anti-inflammatory, immunomodulatory, antioxidant, anticancer, and antiviral agent, where it may play a role as an inhibitor of viral proteinases. At the same time, the comparison of the pharmacoactivity of Rf with its known metabolites, namely, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), is very complicated due to its poor water solubility: 0.1-0.3 g/L versus 67 g/L for FMN and 50 g/L for FAD, which is the limiting factor for its administration in clinical practice. In this study, we report the recrystallization procedure of the type A Rf crystals into the slightly hydrophobic type B/C and a new hydrophilic crystal form that has been termed the P type. Our method of Rf crystal modification based on recrystallization from dilute alkaline solution provides an unprecedented extremely high water solubility of Rf, reaching 23.5 g/L. A comprehensive study of the physicochemical properties of type P riboflavin showed increased photodynamic therapeutic activity compared to the known types A and B/C against clinical isolates of Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Salmonella typhimurium. Importantly, our work not only demonstrates a simple and inexpensive method for the synthesis of riboflavin with high solubility, which should lead to increased bioactivity, but also opens up opportunities for improving both known and new therapeutic applications of vitamin B2.

Development of Submicrocapsules Based on Co-Assembled Like-Charged Silica Nanoparticles and Detonation Nanodiamonds and Polyelectrolyte Layers.

Capsules with shells based on nanoparticles of different nature co-assembled at the interface of liquid phases of emulsion are promising carriers of lipophilic drugs. To obtain such capsules, theoretically using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and experimentally using dynamic light-scattering (DLS) and transmission electron microscopy (TEM) methods, the interaction of like-charged silica nanoparticles and detonation nanodiamonds in an aqueous solution was studied and their ratios selected for the formation of submicron-sized colloidosomes. The resulting colloidosomes were modified with additional layers of nanoparticles and polyelectrolytes, applying LbL technology. As a model anti-cancer drug, thymoquinone was loaded into the developed capsules, demonstrating a significant delay of the release as a result of colloidosome surface modification. Fluorescence flow cytometry and confocal laser scanning microscopy showed efficient internalization of the capsules by MCF7 cancer cells. The obtained results demonstrated a high potential for nanomedicine application in the field of the drug-delivery system development.

Permeability of the Composite Magnetic Microcapsules Triggered by a Non-Heating Low-Frequency Magnetic Field.

Nanosystems for targeted delivery and remote-controlled release of therapeutic agents has become a top priority in pharmaceutical science and drug development in recent decades. Application of a low frequency magnetic field (LFMF) as an external stimulus opens up opportunities to trigger release of the encapsulated bioactive substances with high locality and penetration ability without heating of biological tissue in vivo. Therefore, the development of novel microencapsulated drug formulations sensitive to LFMF is of paramount importance. Here, we report the result of LFMF-triggered release of the fluorescently labeled dextran from polyelectrolyte microcapsules modified with magnetic iron oxide nanoparticles. Polyelectrolyte microcapsules were obtained by a method of sequential deposition of oppositely charged poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrenesulfonate) (PSS) on the surface of colloidal vaterite particles. The synthesized single domain maghemite nanoparticles integrated into the polymer multilayers serve as magneto-mechanical actuators. We report the first systematic study of the effect of magnetic field with different frequencies on the permeability of the microcapsules. The in situ measurements of the optical density curves upon the 100 mT LFMF treatment were carried out for a range of frequencies from 30 to 150 Hz. Such fields do not cause any considerable heating of the magnetic nanoparticles but promote their rotating-oscillating mechanical motion that produces mechanical forces and deformations of the adjacent materials. We observed the changes in release of the encapsulated TRITC-dextran molecules from the PAH/PSS microcapsules upon application of the 50 Hz alternating magnetic field. The obtained results open new horizons for the design of polymer systems for triggered drug release without dangerous heating and overheating of tissues.

Fabrication and evaluation of nanocontainers for lipophilic anticancer drug delivery in 3D in vitro model.

Presently, most of anticancer drugs are high toxic for normal cells and, and as a result, they have severe side effects. Moreover, most of the formulations are lipophilic and have poor selectivity. To overcome these limitations, various drug delivery systems could be proposed. The aim of the current study was to fabricate novel polysaccharide nanocontainers (NC) by one-step ultrasonication technique and to evaluate their accumulation efficacy and cytotoxicity in 2D (monolayer culture) and 3D (tumor spheroids) in vitro models. NC with mean sizes in a range of 340-420 nm with the core-shell structure are synthetized and characterized. The NC shell is composed from diethylaminoethyl dextran/xanthan gum polyelectrolyte complex, while the hydrophobic core was loaded with the lipophilic anticancer drug thymoquinone. To enhance NC accumulation in human breast adenocarcinoma MCF-7 cells, the NC surface was modified with poly-L-lysine (PLL) or polyethylene glycol. Cell uptake of the NC loaded with Nile Red into the tumor cells was investigated by laser scanning confocal microscopy, fluorescent flow cytometry and fluorimetry. Modification of the NC with PLL allowed to obtain the optimal drug delivery system with maximal cytotoxicity, which was tested by MTT-test. The developed NC are promising for lipophilic anticancer drug delivery.

Freezing-Induced Loading of TiO2 into Porous Vaterite Microparticles: Preparation of CaCO3/TiO2 Composites as Templates To Assemble UV-Responsive Microcapsules for Wastewater Treatment.

The photocatalytic degradation of organic molecules is one of the effective ways for water purification. At this point, photocatalytic microreactor systems seem to be promising to enhance the versatility of the photoassisted degradation approach. Herein, we propose photoresponsive microcapsules prepared via layer-by-layer assembly of polyelectrolytes on the novel CaCO3/TiO2 composite template cores. The preparation of CaCO3/TiO2 composite particles is challenging because of the poor compatibility of TiO2 and CaCO3 in an aqueous medium. To prepare stable CaCO3/TiO2 composites, TiO2 nanoparticles were loaded into mesoporous CaCO3 microparticles with a freezing-induced loading technique. The inclusion of TiO2 nanoparticles into CaCO3 templates was evaluated with scanning electron microscopy and elemental analysis with respect to their type, concentration, and number of loading iterations. Upon polyelectrolyte shell assembly, the CaCO3 matrix was dissolved, resulting in microreactor capsules loaded with TiO2 nanoparticles. The photoresponsive properties of the resulted capsules were tested by photoinduced degradation of the low-molecule dye rhodamine B in aqueous solution and fluorescently labeled polymer molecules absorbed on the capsule surface under UV light. The exposure of the capsules to UV light resulted in a pronounced degradation of rhodamine B in capsule microvolume and fluorescent molecules on the capsule surface. Finally, the versatility of preparation of multifunctional photocatalytic and magnetically responsive capsules was demonstrated by iterative freezing-induced loading of TiO2 and magnetite Fe3O4 nanoparticles into CaCO3 templates.

Enzymatic degradation of the polymer capsules with a hydrophobic core in the presence of Langmuir lipid monolayer as a model of the cellular membrane.

Submicrocapsules were prepared from diethylaminoethyl dextran (DEAE-D), xanthan gum (XG) and bovine serum albumin (BSA) on oil cores by ultrasonic treatment. These capsules were modified with poly-L-lysine (PLL) via electrostatic adsorption. The behavior of the capsules was investigated at an air-water interface after their introduction into an aqueous subphase. The interaction of the capsules with 1,2-Dimyristoyl-sn-glycero-3-phosphocholine (DMPC) monolayer formed on the water surface (model cellular membrane) was studied both upon their introduction under the condensed monolayer and with the use of a dilute colloidal solution of the capsules as a subphase. Biodegradation of the proteinaceous capsules with subsequent oil-core release was demonstrated by influence of pronase. The Langmuir lipid monolayer was found to be a good model for investigation of drug release from the capsules in the presence of the cellular membrane.

Composite materials based on Ag nanoparticles in situ synthesized on the vaterite porous matrices.

We have designed sensors based on Ag nanoparticles synthesized in situ on the vaterite beads. In this article we demonstrate an approach to produce size controllable spherical and elliptical vaterite particles and discuss time-dependent in situ Ag nanoparticles synthesis and its potential effect on surface-enhanced Raman scattering. The time dependent silver reduction synthesis in inorganic porous particles allows to regulate the number and size of Ag nanoparticles. It is shown that the irregular surface and high porosity of vaterite particles and large amount (surface filling factor) of the Ag nanoparticles are the critical parameters to increase the SERS signal to 104 times. Such inorganic composites have a huge potential in medical applications; soon they provide an opportunity to study intracellular processes in vivo. The detailed characterization of the microstructure of these composites was studied by scanning and transmission electron microscopy, including 3D visualization and energy dispersive x-ray microanalysis.

A novel formulation of zolpidem for direct nose-to-brain delivery: synthesis, encapsulation and intranasal administration to mice.

OBJECTIVES: Anxiolytic drug zolpidem was incorporated into the microcontainers based on mesoporous calcium carbonate particles modified by diethylaminoethyl-dextran/hyaluronic acid shell. The release of zolpidem in saline solution and in polymer film modelling nasal mucosa was investigated. The anxiolytic effect of zolpidem upon intranasal administration of microcontainers and free medicine was determined by in vivo experiments on mice. METHODS: The structures of all compounds during zolpidem synthesis were established using nuclear magnetic resonance spectroscopy. The loading efficacy and release kinetics of zolpidem were analysed by spectrophotometry. Surface morphology of formulation was investigated by scanning electron microscopy. To determine the effect of zolpidem-loaded containers administration by the intranasal route in vivo experiments was carried out applying the open field test. KEY FINDINGS: Nasal administration of zolpidem in the form of the microcontainers based on mesoporous calcium carbonate particles modified by diethylaminoethyl-dextran/hyaluronic acid shell has a pronounced anxiolytic effect on the behaviour of the animals in the open field test. CONCLUSIONS: The polyelectrolyte shell deposited together with zolpidem enhances the loading efficacy of the microcontainers. In vivo experiments on mice demonstrate increase in anxiolytic effect of zolpidem in microcontainers compared with upon intranasal administration of free medicine.

Heat-driven size reduction of biodegradable polyelectrolyte multilayer hollow capsules assembled on CaCO3 template.

Aiming to explore elevated temperatures as a tool for miniaturization of biodegradable polymer multilayer capsules, assembled on spherical vaterite micron- and submicron-sized particles, we subject the shells composed of dextran sulfate (DS) and poly-L-arginine (Parg) to a heat treatment. Changes of the capsule size are studied at various temperatures and ionic strengths of the continuous phase. Unlike some synthetic polymer multilayer shells (their response to heat treatment depends on the number of layers and their arrangement), the biodegradable Parg/DS capsules exhibit size reduction and profound compaction regardless of their initial size, number of polymer layers and polymer layer sequence. The capsule response to heat is stable at ionic strengths of the continuous phase not exceeding 0.1 M NaCl.

Mesoporous particle-based microcontainers for intranasal delivery of imidazopyridine drugs.

The aim of this study was to develop mesoporous containers for entrapment of imidazopyridines, such as sedative-hypnotic medicine zolpidem, anxiolytic agent alpidem and their derivatives. For this purpose, calcium carbonate (size 1.2 µm (PDI: 0.6), zeta potential: -10 mV), manganese carbonate (2.5 µm (PDI: 0.5), zeta potential: -12 mV) and titanium dioxide particles (3.7 µm (PDI: 0.4), zeta potential: -15 mV) were used. The compounds were encapsulated applying two techniques: adsorption on the preformed particles and co-precipitation during the synthesis of the particles. The polymer shell of the containers was formed by electrostatic adsorption of polyelectrolytes on the surface of the particles. The best encapsulation efficacy was shown for zolpidem incorporated into calcium carbonate (5.4%) and manganese carbonate (4.6%) by adsorption. Release of the compounds from the containers based on the proposed particles were characterised by the short time burst effect (<10 min) followed by desorption prolongation by formation of polymer shell. X-ray microtomography results demonstrate the prolonged retention of the containers with the mucoadhesive shell in the nasal cavity.

Ultrasonically Assisted Polysaccharide Microcontainers for Delivery of Lipophilic Antitumor Drugs: Preparation and in Vitro Evaluation.

High toxicity, poor selectivity, and severe side effects are major drawbacks of anticancer drugs. Various drug delivery systems could be proposed to overcome these limitations. The aim of this study was to fabricate polysaccharide microcontainers (MCs) loaded with thymoquinone (TQ) by a one-step ultrasonication technique and to study their cellular uptake and cytotoxicity in vitro. Two MC fractions with a mean size of 500 nm (MC-0.5) and 2 µM (MC-2) were prepared and characterized. Uptake of the MCs by mouse melanoma M-3 cells was evaluated in both 2D (monolayer culture) and 3D (multicellular tumor spheroids) models by confocal microscopy, flow cytometry, and fluorimetry. The higher cytotoxicity of the TQ-MC-0.5 sample than the TQ-MC-2 fraction was in good correlation with higher MC-0.5 accumulation in the cells. The MC-0.5 beads were more promising than the MC-2 particles because of a higher cellular uptake in both 2D and 3D models, an enhanced antitumor effect, and a lower nonspecific toxicity.

CaCO3 vaterite microparticles for biomedical and personal care applications.

Among the polymorph modifications of calcium carbonate, the metastable vaterite is the most practically important. Vaterite particles are applied in regenerative medicine, drug delivery and a broad range of personal care products. This manuscript scopes to review the mechanism of the calcium carbonate crystal growth highlighting the factors stabilizing the vaterite polymorph in the most cost efficient synthesis routine. The size of vaterite particles is a crucial parameter for practical applications. The options for tuning the particle size are also discussed.

Controlled enzyme-catalyzed degradation of polymeric capsules templated on CaCO3: influence of the number of LbL layers, conditions of degradation, and disassembly of multicompartments.

Enzyme-catalyzed degradation of CaCO3-templated capsules is presented. We investigate a) biodegradable, b) mixed biodegradable/synthetic, and c) multicompartment polyelectrolyte multilayer capsules with different numbers of polymer layers. Using confocal laser scanning microscopy we observed the kinetics of the non-specific protease Pronase-induced degradation of capsules is slowed down on the order of hours by either increasing the number of layers in the wall of biodegradable capsules, or by inserting synthetic polyelectrolyte multilayers into the shell comprised of biodegradable polymers. The degradation rate increases with the concentration of Pronase. Controlled detachment of subcompartments of multicompartment capsules, with potential for intracellular delivery or in-vivo applications, is also shown.