Designed hybrid aerogels (silica & gelatin) for immediate and sustained release of hydrophobic acid drugs.
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A comprehensive study of 14 hybrid aerogels of different composition with ...applications in drug delivery has been carried out. The overall objective was to modulate the release behavior of drug-impregnated aerogels, from an almost instantaneous release to a semi-retarded delivery prolonged during several hours, through internal surface functionalization. The designed hybrid aerogels were composed of silica and gelatin and functionalized with either phenyl, long (16) hydrocarbon chain or methyl moiety. As model systems, three class II active agents (pKa<5.5), ibuprofen, ketoprofen and triflusal, were chosen to impregnate the aerogels. The work relied on the use of supercritical fluid technology for both the synthesis and functionalization of the hybrid aerogels, as well as for the impregnation with an active agent using supercritical CO2 as a solvent. For the impregnated aerogels, in vitro release profiles were recorded under gastric and intestinal pH-conditions using HPLC techniques. The release behavior observed for the three studied drugs was explained considering the measured dissolution profiles of the crystalline drugs, the aerogel composition and its functionalization. Such features are considered of great interest to tailor the bioavailability of drugs with low water solubility.
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•Sol-gel synthesis of crack free monoliths of silica-casein hybrid aerogels.•Characterization of dry aerogels by SEM, N2 gas porosimetry and SANS.•Hydration mechanism by NMR ...cryoporometry, relaxometry, diffusiometry and SANS.•Non-conventional hydration mechanism of hybrids explained by backbone rigidity.•Biocompatibility of silica-casein aerogels proved by in vitro tests.
Starting from TMOS and implementing co-gelation in the sol-gel method, silica was hybridized with an industrial formulation of bovine casein. The hybrid alcogels were dried in supercritical CO2 to yield crack-free silica-casein aerogel monoliths of casein contents ranging from 4.7 wt% to 28 wt%. Cross-linked hybrid aerogels were produced from formaldehyde treated alcogels. The microstructures and the morphologies of the silica-casein aerogels highly resemble to that of pristine silica aerogels. The primary building blocks are spherical particles that interconnect into mesoporous networks (average dpore = 20 nm and SBET = 700 nm2/g), as shown by SEM, small-angle neutron scattering (SANS) and N2 adsorption-desorption porosimetry. Contrast variation SANS experiments show that silica and casein form homogeneous nanocomposite backbones. The interaction of water with silica-casein aerogels was investigated by SANS, and by NMR cryoporometry, relaxometry and diffusiometry. Even when fully saturated with water, the hybrid silica-casein aerogels retain their original, highly permeable, open mesoporous structures that formed under supercritical drying. This represents a unique and advantageous wetting mechanism among hybrid inorganic-biopolymer materials, since the strong hydration of the biopolymer component often causes the deformation of the backbone and the consequent collapse of the porous structure. Silica-casein aerogels are biocompatible and inert for CHO-K1 cells.
Electrospinning has recently been recognized as a potential method for use in biomedical applications such as nanofiber-based drug delivery or tissue engineering scaffolds. The present study aimed to ...demonstrate the electrospinning preparation and suitability of β-tricalcium phosphate-modified aerogel containing polyvinyl alcohol/chitosan fibrous meshes (BTCP-AE-FMs) for bone regeneration under in vitro and in vivo conditions. The mesh physicochemical properties included a 147 ± 50 nm fibrous structure, in aqueous media the contact angles were 64.1 ± 1.7°, and it released Ca, P, and Si. The viability of dental pulp stem cells on the BTCP-AE-FM was proven by an alamarBlue assay and with a scanning electron microscope. Critical-size calvarial defects in rats were performed as in vivo experiments to investigate the influence of meshes on bone regeneration. PET imaging using
F-sodium fluoride standardized uptake values (SUVs) detected 7.40 ± 1.03 using polyvinyl alcohol/chitosan fibrous meshes (FMs) while 10.72 ± 1.11 with BTCP-AE-FMs after 6 months. New bone formations were confirmed by histological analysis. Despite a slight change in the morphology of the mesh because of cross-linking, the BTCP-AE-FM basically retained its fibrous, porous structure and hydrophilic and biocompatible character. Our experiments proved that hybrid nanospun scaffold composite mesh could be a new experimental bone substitute bioactive material in future medical practice.
The study introduces the current situation of electric vehicle technologies, the possibilities and possible directions of their market, as well as the economic and environmental aspects in the ...eastern region of the EU, with special regard to Hungary. Our calculations show that despite the higher costs of ownership, in the case of 7 years of use (among Hungarian conditions), the total cost of the Battery Electric Vehicles (BEV) is lower than that of the Internal Combustion Engine Vehicles (ICEV) in each of the four segments analysed. The purchasing power of the population in the eastern regions of the EU is clearly lower compared to the western regions, yet people in this region spend beyond their financial means on motorization. Despite its unfavourable position, Hungary is in a particularly advantageous position compared to other countries in the region per vehicle and per capita in terms of the spread of BEVs. In the long run, even taking higher prices into account, the use of electric cars, in general, has significant advantages from an economic point of view; lower maintenance costs and fuel prices (especially with increased use) make EVs more cost-effective overall.
Replacement of damaged or missing bone tissue is a serious problem in orthopedic surgery. Although various artificial materials are available, none of them fulfil the requirements completely. In this ...study, new bone substitute materials, silica aerogel-based β-tricalcium phosphate, and hydroxyapatite composite ceramics, along with a control sample were synthesized and tested. Porosities and pore size distribution curves were determined by nitrogen gas adsorption/desorption porosimetry, and surface morphology changes were studied by scanning electron microscopy. Bioactivities were tested in vitro by soaking the samples in simulated body fluids (SBF). Three new advanced SBFs containing eight essential amino acids and bovine serum albumin were developed, extending the complexity of the original simulated body fluid in order to approximate the human blood plasma’s composition more accurately. Each sample was treated with SBF1–SBF4 for two weeks. According to our results, it seems to be necessary to re-evaluate hydroxyapatite deposition as proof of bioactivity of artificial bone substitutes when synthetic body fluids analogous in their composition to human blood plasma are used in studies.
Silica-gelatin hybrid aerogels, introduced recently as drug delivery devices, were investigated for biocompatibility with SCC tumor cells by a time-lapse video-microscopy technique. The particles ...proved to be not only non-toxic in nature, but the cells migrated towards them. Fluorescently labeled hybrid aerogels were synthesized by covalently binding fluorescein isothiocyanate either to the amino groups of gelatin molecules, or to the amine-functionalized silica backbone prior to sol-gel polycondensation and co-gelation steps. Scanning electron microscopy and fluorescence spectroscopy characterization of pristine and labeled aerogels showed identical structures and spectra, while fluorescence lifetimes were 10% shorter than that of the free fluorescein, due to covalent attachment. Migration plots based on time-lapse video recordings showed that the cells exhibited a directive migration nearby the aerogel particles. No signs of apoptosis or necrosis were observed at any phases of the cell cycle in the presence of the silica-gelatin aerogel particles, indicating that the hybrid aerogels are biocompatible materials, and may be used as drug delivery matrices in living organisms.
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•Biocompatibility with SCC tumor cells by time-lapse video-microscopy•Covalently binding fluorescein isothiocyanate to either gelatin or silica•Steady-state and time-resolved fluorescence spectroscopy
Meteorologists keep searching and running models to provide the most accurate forecast of wind speed in addition to gaining a more detailed understanding of the wind conditions in Hungary. Wind speed ...and wind energy estimates, forecasts, and their verification are based on wind statistics from a longer or shorter previous period. Consequently, in addition to dynamic methods, purely statistical models also play an important role, i.e., findings that can be obtained from the statistical analysis of the existing database of measured data. The successive phases of the statistical method for producing scientific or operational information that can be extracted from measured, corrected, and stored meteorological data are generally: statistical analysis/processing, creating, verification, and application of the model, recording of the required information. The targeted information in this paper is the daily average of hourly wind speeds. The exact average of this time series can only be determined after the last measurement. To estimate this average during the day, however, the so-called sliding average model has been developed, which can be applied to any climatic element if its measured values are recorded at regular times over a certain period of time. The results presented in this paper are recommended for the preparation of the so-called "timetable", which is one of the most difficult problems for wind farm operators. This is basically the estimation of the amount of electricity produced the following day over short periods. It would be a significant help in the above if we can determine the probability of a decrease or increase in the average wind speed on the next day (and with it, the average daily wind power), or which of these two probabilities is greater. This requires an estimate of average wind speed of the next day. In addition, the results of one of our previous studies on the statistical structure of dayto-day changes in average daily wind speeds were also used. According to the results of the monthly testing of the model over a given period, the frequency of good estimates is between 80.6 % and 54.8%.
Fenton reactions with metal complexes of substituted porphyrins and hydrogen peroxide are useful tools for the mineralization of environmentally dangerous substances. In the homogeneous phase, ...autooxidation of the prophyrin ring may also occur. Covalent binding of porphyrins to a solid support may increase the lifetime of the catalysts and might change its activity. In this study, highly water-insoluble copper and iron complexes of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin were synthesized and bonded covalently to a very hydrophilic silica aerogel matrix prepared by co-gelation of the propyl triethoxysilyl-functionalized porphyrin complex precursors with tetramethoxysilane, followed by a supercritical carbon dioxide drying. In contrast to the insoluble nature of the porphyrin complexes, the as-prepared aerogel catalysts were highly compatible with the aqueous phase. Their catalytic activities were tested in the mineralization reaction of phenol, 3-chlorophenol, and 2,4-dichlorophenol with hydrogen peroxide. The results show that both aerogels catalyzed the oxidation of phenol and chlorophenols to harmless short-chained carboxylic acids under neutral conditions. In batch experiments, and also in a miniature continuous-flow tubular reactor, the aerogel catalysts gradually reduced their activity, due to the slow oxidation of the porphyrin ring. However, the rate and extent of the degradation was moderate and did not exclude the possibility that the as-prepared catalysts, as well as their more stable derivatives, might find practical applications in environment protection.
Mesoporous silica aerogels covalently functionalized with Cu(II) complexes of cyclen (1,4,7,10-tetraazacyclododecane) and cyclam (1,4,8,11-tetraazacyclotetradecane), denoted as CuAM12 and CuAM14, ...respectively, have been first prepared. Monolithic materials were synthesized from alkoxysilane-anchored macrocyclic complexes and TMOS through the base catalyzed sol-gel method followed by a supercritical CO2 drying. Presence of organic moieties in the silica structure was confirmed by FT-IR measurements, the amount of incorporated copper was determined by ICP-OES technique, resulting in 1.310 ± 0.028 and 2.060 ± 0.025 wt% copper for CuAM12 and CuAM14, respectively). Surface morphology was characterized by nitrogen adsorption/desorption porosimetry and scanning electron microscopy. Catalytic activities of the aerogels CuAM12 and CuAM14 were evaluated by oxidation of phenol with eco-friendly reagent hydrogen peroxide, without buffering or using organic co-solvents. Control experiments using unbound macrocyclic complexes in the homogenous phase were also conducted. Surprisingly, results revealed that the functionalized aerogels' turnover frequencies (TOF) were approximately 7–15 times higher than that of the free complexes in the homogeneous phase. The increase was attributed to the confinement effect. Reusability studies showed that the catalysts remained active even after four cycles completed. Certain reduction of catalytic activity was observed in the repeated cycles, which was the combined effect of poor mechanical properties of the aerogel, splitting-off and leaching of the less-bound surface macrocycles, and extensive adsorption of the oxidation products.
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•New covalently functionalized silica aerogels were prepared by the sol-gel method.•Catalytic activities were evaluated by the oxidation of phenol with H2O2 solution.•Phenol was mineralized to environment-friendly carboxylic acids in 4 h.•Confinement effect in mesopores resulted in 7–15 times higher catalytic affinities.•Aerogel catalysts remain active even after four cycles completed.
A micrometeorological fog experiment was carried out in Budapest, Hungary during the winter half year of 2020–2021. The field observation involved (i) standard meteorological and radiosonde ...measurements; (ii) surface radiation balance and energy budget components, and (iii) ceilometer measurements. 23 fog events occurred during the whole campaign. Foggy events were categorized based on two different methods suggested by Tardif and Rasmussen (2007) and Lin et al. (2022). Using the Present Weather Detector and Visibility sensor (PWD12), duration of foggy periods are approximately shorter (~ 9%) compared to ceilometer measurements. The categorization of fog based on two different methods suggests that duration of radiation fogs is lower compared to that of cloud base lowering (CBL) fogs. The results of analysis of observed data about the longest fog event suggest that (i) it was a radiation fog that developed from the surface upwards with condition of a near neutral temperature profile. Near the surface the turbulent kinetic energy and turbulent momentum fluxes remained smaller than 0.4 m
2
s
–2
and 0.06 kg m
–1
s
–2
, respectively. In the surface layer the vertical profile of the sensible heat flux was near constant (it changes with height ~ 10%), and during the evolution of the fog, its maximum value was smaller than 25 W m
–2
, (ii) the dissipation of the fog occurred due to increase of turbulence, (iii) longwave energy budget was close to zero during fog, and a significant increase of virtual potential temperature with height was observed before fog onset. The complete dataset gives an opportunity to quantify local effects, such as tracking the effect of strengthening of wind for modification of stability, surface layer profiles and visibility. Fog formation, development and dissipation are quantified based on the micrometeorological observations performed in suburb area of Budapest, providing a processing algorithm for investigating various fog events for synoptic analysis and for optimization of numerical model parameterizations.
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