Investigation of Gelation Techniques for the Fabrication of Cellulose Aerogels

Because of the pronounced degradation of the environment, there has been an escalated demand for the fabrication of eco-friendly and highly efficient products derived from renewable sources. Cellulose aerogels have attracted significant interest attributable to their structural characteristics coupled with biodegradability and biocompatibility. The features of the molecular structure of cellulose allow for the use of various methods in the production of gels. For instance, the presence of hydroxyl groups on the cellulose surface allows for chemical crosslinking via etherification reactions. On the other hand, cellulose gel can be procured by modulating the solvent power of the solvent. In this study, we investigate the impact of the gelation methodology on the structural attributes of aerogels. We present methodologies for aerogel synthesis employing three distinct gelation techniques: chemical crosslinking, cryotropic gelation, and CO2-induced gelation. The outcomes encompass data derived from helium pycnometry, Fourier-transform infrared spectroscopy, nitrogen porosimetry, and scanning electron microscopy. The resultant specimens exhibited a mesoporous fibrous structure. It was discerned that specimens generated through cryotropic gelation and CO2-induced gelation manifested higher porosity (93-95%) and specific surface areas (199-413 m2/g) in contrast to those produced via chemical crosslinking (porosity 72-95% and specific surface area 25-133 m2/g). Hence, this research underscores the feasibility of producing cellulose-based aerogels with enhanced characteristics, circumventing the necessity of employing toxic cross-linking agents. The process of gel formation through chemical crosslinking enables the creation of gels with enhanced mechanical properties and a more resilient structure. Two alternative methodologies prove particularly advantageous in applications necessitating biocompatibility and high porosity. Notably, CO2-induced gelation has not been hitherto addressed in the literature as a means to produce cellulose gels. The distinctive feature of this approach resides in the ability to combine the stages of obtaining an aerogel in one apparatus.

Investigation of the 3D Printing Process Utilizing a Heterophase System

Direct ink writing (DIW) requires careful selection of ink composition with specific rheological properties, and it has limitations, such as the inability to create overhanging parts or branched geometries. This study presents an investigation into enhancing the 3D printing process through the use of a heterophase system, aiming to overcome these limitations. A modification was carried out in the 3D printer construction, involving adjustments to the structural elements responsible for the extrusion device's movement. Additionally, a method for obtaining a heterophase system based on gelatin microparticles was developed to enable the 3D printing process with the upgraded printer. The structure and rheological properties of the heterophase system, varying in gelatin concentration, were thoroughly examined. The material's viscosity ranged from 5.4 to 32.8 kPa·s, exhibiting thixotropic properties, pseudoplastic behavior, and long-term stability at 20 °C. The developed 3D printing technology was successfully implemented using a heterophase system based on different gelatin concentrations. The highest product quality was achieved with a heterophase system consisting of 4.5 wt.% gelatin, which exhibited a viscosity of 22.4 kPa·s, enabling the production of products without spreading or compromising geometrical integrity.

Chitosan Aerogel Particles as Nasal Drug Delivery Systems

The nasal drug delivery route has distinct advantages, such as high bioavailability, a rapid therapeutic effect, non-invasiveness, and ease of administration. This article presents the results of a study of the processes for obtaining chitosan aerogel particles that are promising as nasal or inhalation drug delivery systems. Obtaining chitosan aerogel particles includes the following steps: the preparation of a chitosan solution, gelation, solvent replacement, and supercritical drying. Particles of chitosan gels were obtained by spraying and homogenization. The produced chitosan aerogel particles had specific surface areas of up to 254 m²/g, pore volumes of up to 1.53 cm³/g, and porosities of up to 99%. The aerodynamic diameters of the obtained chitosan aerogel particles were calculated, the values of which ranged from 13 to 59 µm. According to the calculation results, a CS1 sample was used as a matrix for obtaining the pharmaceutical composition "chitosan aerogel-clomipramine". X-ray diffraction (XRD) analysis of the pharmaceutical composition determined the presence of clomipramine, predominantly in an amorphous form. Analysis of the high-performance liquid chromatography (HPLC) data showed that the mass loading of clomipramine was 35%. Experiments in vivo demonstrated the effectiveness of the pharmaceutical composition "chitosan aerogel-clomipramine" as carrier matrices for the targeted delivery of clomipramine by the "Nose-to-brain" mechanism of nasal administration. The maximum concentration of clomipramine in the frontal cortex and hippocampus was reached 30 min after administration.

Luminescent Hybrid Material Based on Boron Organic Phosphor and Silica Aerogel Matrix

A new luminescent hybrid material based on silica aerogel and a boron-containing coordination compound with 8-hydroxyquinoline was created, and its physicochemical and spectral-luminescent characteristics were studied. A simple scheme for the synthesis of a hybrid luminescent material was developed. Simultaneously with the synthesis of the aerogel, the formation of a boron-containing phosphor was carried out using an isopropanol solution of boric acid and 8-hydroxyquinoline. Using in situ luminescent measurements, the mechanisms of the formation of boron-based luminescent complexes in isopropanol and tetrahydrofuran media were established. Both hydrophilic and hydrophobic silica aerogels were tested as matrices for the hybrid material. The formation of a thin layer of a boron-containing coordination luminescent compound on the highly developed surface of the SiO₂ aerogel made it possible to strongly stabilize the aerogel structure and noticeably increase the thermal stability of the synthesized hybrid material.

Composites Composed of Hydrophilic and Hydrophobic Polymers, and Hydroxyapatite Nanoparticles: Synthesis, Characterization, and Study of Their Biocompatible Properties

The creation of artificial biocomposites consisting of biocompatible materials in combination with bioactive molecules is one of the main tasks of tissue engineering. The development of new materials, which are biocompatible, functional, and also biodegradable in vivo, is a specific problem. Two types of products can be formed from these materials in the processes of biodegradation. The first types of substances are natural for a living organism and are included in the metabolism of cells, for example, sugars, lactic, glycolic, and β-hydroxybutyric acids. Substances that are not metabolized by cells represent the other type. In the latter case, such products should not be toxic, and their concentration when entering the bloodstream should not exceed the established maximum permissible level. The composite materials based on a mixture of biodegradable synthetic and natural polymers with the addition of hydroxyapatite nanoparticles, which acts as a stabilizer of the dispersed system during production of the composite, and which is a biologically active component of the resulting matrix, were obtained and studied. The indirect effect of the shape, size, and surface charge of hydroxyapatite nanoparticles on the structure and porosity of the formed matrix was shown. An in vivo study showed the absence of acute toxicity of the developed composites.

Cellular Automata Modeling of Three-Dimensional Chitosan-Based Aerogels Fiberous Structures with Bezier Curves

In this work, a cellular automata approach was investigated for modeling three-dimensional fibrous nanoporous aerogel structures. A model for the generation of fibrous structures using the Bezier curves is proposed. Experimental chitosan-based aerogel particles were obtained for which analytical studies of the structural characteristics were carried out. The data obtained were used to generate digital copies of chitosan-based aerogel structures and to assess the accuracy of the developed model. The obtained digital copies of chitosan-based aerogel structures will be used to create digital copies of aerogel structures with embedded active pharmaceutical ingredients (APIs) and further predict the release of APIs from these structures.

Extrusion-Based 3D Printing for Highly Porous Alginate Materials Production

Three-dimensional (3D) printing is a promising technology for solving a wide range of problems: regenerative medicine, tissue engineering, chemistry, etc. One of the potential applications of additive technologies is the production of highly porous structures with complex geometries, while printing is carried out using gel-like materials. However, the implementation of precise gel printing is a difficult task due to the high requirements for “ink”. In this paper, we propose the use of gel-like materials based on sodium alginate as “ink” for the implementation of the developed technology of extrusion-based 3D printing. Rheological studies were carried out for the developed alginate ink compositions. The optimal rheological properties are gel-like materials based on 2 wt% sodium alginate and 0.2 wt% calcium chloride. The 3D-printed structures with complex geometry were successfully dried using supercritical drying. The resulting aerogels have a high specific surface area (from 350 to 422 m²/g) and a high pore volume (from 3 to 3.78 cm³/g).

A Cellular Automata Approach for the Modeling of a Polyamide and Carbon Aerogel Structure and Its Properties

In this work, a cellular automata (CA) approach was used to generate 3D structures of polyamide and carbon aerogels. Experimental results are used as initial data for materials’ digital representations and to verify the developed CA models. Based on the generated digital structures, a computer study of aerogels’ mechanical properties was conducted. The offered CA models can be applied for the development of new nanoporous materials such as aerogels of different nature and allow for a reduction in the amount of required full-scale experiments, consequently decreasing development time and costs of new material formulations.

Chitosan-Based Aerogel Particles as Highly Effective Local Hemostatic Agents. Production Process and In Vivo Evaluations

Chitosan aerogels with potential applications as effective local hemostatic agents were prepared using supercritical carbon dioxide drying to preserve the chitosan network structure featuring high internal surfaces and porosities of up to 300 m²/g and 98%, respectively. For the first time, hemostatic efficacy of chitosan-based aerogel particles was studied in vivo on a model of damage of a large vessel in the deep wound. Pigs were used as test animals. It was shown that primary hemostasis was achieved, there were no signs of rebleeding and aerogel particles were tightly fixed to the walls of the wound canal. A dense clot was formed inside the wound (at the femoral artery), which indicates stable hemostasis. This study demonstrated that chitosan-based aerogel particles have a high sorption capacity and are highly effective as local hemostatic agents which can be used to stop massive bleeding.

Experimental Investigation and CFD Modeling of Supercritical Adsorption Process

The kinetics of the supercritical adsorption process was experimentally studied by the example of ”ibuprofen-silica aerogel” composition obtainment at various parameters: Pressure 120–200 bar and temperature 40–60 °C. Computational Fluid Dynamics (CFD) model of the supercritical adsorption process in a high-pressure apparatus based on the provisions of continuum mechanics is proposed. Using supercritical adsorption process kinetics experimental data, the dependences of the effective diffusion coefficient of active substance in the aerogel, and the maximum amount of the adsorbed active substance into the aerogel on temperature and pressure are revealed. Adequacy of the proposed model is confirmed. The proposed mathematical model allows predicting the behavior of system (fields of velocity, temperature, pressure, composition, density, etc.) at each point of the studied medium. It makes possible to predict mass transport rate of the active substance inside the porous body depending on the geometry of the apparatus, structure of flow, temperature, and pressure.

Alginate-Based Aerogel Particles as Drug Delivery Systems: Investigation of the Supercritical Adsorption and In Vitro Evaluations

The present work focuses on the preparation of alginate-based aerogels in the form of particles for their further study as potential drug delivery systems (solid dosage forms). The dripping method was used to prepare certain gel particles, and supercritical drying was used to obtain final alginate-based aerogel particles. Three model active substances (ketoprofen, nimesulide, loratadine) were impregnated into the obtained aerogels using the supercritical adsorption process. Using the method of X-ray analysis, it was shown that the in the obtained drug-loaded aerogels the corresponding active substances are in an amorphous state, and the stability of this state after six months of storage is confirmed. In vitro dissolution tests for obtained drug-loaded aerogels was performed. For each sample, an appropriate dissolution medium (with certain pH) was determined. In vitro investigations showed the increasing of the release rate for all model active substances. Time was required to release and dissolve 50% of the active drug from drug-loaded aerogels (T1/2), reduced in comparison with pure active drugs in crystalline form. Obtained results provide insight into the application of alginate-based aerogel particles as a drug delivery system to improve pharmacokinetic properties of certain active drugs.

E-Learning and Development of New Courses and Scientific Work in the Field of Pharmaceutical Technology

Since 2001, the Institute of Pharmaceutical Technology (IPT) at the University of Basel and the Mendeleyev University of Chemical Technology of Russia (MUCTR) have established an institutional partnership (IP), which is supported by the Swiss National Science Foundation (SNF) in the framework of the SCOPES (Scientific Cooperation between Eastern Europe and Switzerland) project. The results of this collaboration are the new teaching technologies that were introduced at the MUCTR and the IPT. The former include multimedia lectures in pharmaceutical technology, which are held in parallel at University of Basel and MUCTR, and the educational web-portal 'Pharmacy online', which was awarded a medal at the 4th Moscow International Salon of Innovations. The multimedia lectures are popular with and helpful for MUCTR students, because they can compensate to a certain extent the lack of equipment at the MUCTR. However, multimedia lectures can never replace hands-on training and therefore the continuation of the collaboration is ongoing. In this respect SNF decided in 2005 to give continuous support for this cooperation through the grant entitled 'New Concepts in Training Industrial Pharmacists and Pharmaceutical Engineers to Be Developed and Implemented at the Russian-Swiss Scientific and Education Centre in MUCTR'. This centre was established as a result of the previous grant. The development and implementation of a unique and innovative learning concept on the basis of the Russian-Swiss scientific and educational centre involving the Russian pharmaceutical and biotechnological industry, is an ongoing activity.

In vivo comparison of various liposome formulations for cosmetic application☆

The interaction of liposome formulations, prepared with phospholipids of different origins (egg and soya), with skin were compared in terms of their effects on skin water content, skin barrier function, and skin elasticity. Short-term effect of four different liposome formulations and two references during 3.5 h was investigated non-occlusively on the volar side of the forearm of 10 volunteers, ranging in age from 24 to 32 years. Liposomes composed of different phospholipids showed differing effects on skin humidity. The maximal effect was achieved within 30 min and constant values were reached after 1.5 h for all formulations, however values remained significantly higher than without treatment (p<0.05) during the whole application time. The best results were obtained with liposome formulations prepared from egg phospholipids, which exhibited a 1.5-fold increase in skin water content (p<0.05), whereas liposome formulations prepared from soya phospholipids showed no advantage compared to the references. Skin barrier function showed greatest influence within 30 min after application and remained constant after 1.5 h for all formulations. Within the liposome formulations, egg phospholipids showed the highest transepidermal water loss values during the first 30 min, representing the strongest interactions with the skin barrier function, whereas for the other liposome formulations lower transepidermal water loss values were measured. Skin elasticity and tiring effect of the skin was not influenced by any of the formulations, due to the young skin tested. Long-term effect of two different liposome formulations mixed with base cream DAC in two different concentrations during 14 days was investigated non-occlusively on the volar side of the forearm of 10 volunteers, ranging in age from 20 to 25 years. Skin water content was measured daily and the results showed that skin humidity was increased significantly (p<0.05) for the formulation containing 20% egg phospholipids during 6 days. Liposome formulations prepared with egg phospholipids showed significantly higher (p<0.01) hydration effects during 3.5 h of application on human skin compared with liposome formulations prepared with soya phospholipids.