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Hybrid polylactic-acid–pectin aerogels : synthesis, structural properties, and drug release
Gabrijela Horvat, Klara Žvab, Željko Knez, Zoran Novak, 2023, izvirni znanstveni članek

Opis: Wound-dressing materials often include other materials stimulating wound healing. This research describes the first formulation of biodegradable hybrid aerogels composed of polylactic acid and pectin. The prepared hybrid material showed a highly porous structure with a surface area of 166 +/- 22.6 m(2)center dot g(-1). The addition of polylactic acid may have decreased the surface area of the pure pectin aerogel, but it improved the stability of the material in simulated body fluid (SBF). The pure pectin aerogel showed a high swelling and degradation ratio after 3 h. The addition of the polylactic acid prolonged its stability in the simulated body fluid from 24 h to more than one week, depending on the amount of polylactic acid. Biodegradable aerogels were loaded with indomethacin and diclofenac sodium as model drugs. The entrapment efficiencies were 63.4% and 62.6% for indomethacin and diclofenac sodium, respectively. Dissolution of both drugs was prolonged up to 2 days. Finally, sodium percarbonate and calcium peroxide were incorporated into the bioaerogels as chemical oxygen sources, to evaluate oxygen generation for potential wound healing applications.
Ključne besede: hybrid aerogels, bioaerogel, pectin, polylactic acid, wound healing
Objavljeno v DKUM: 20.02.2024; Ogledov: 257; Prenosov: 15
.pdf Celotno besedilo (2,62 MB)
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Green Processing of Neat Poly(lactic acid) Using Carbon Dioxide under Elevated Pressure for Preparation of Advanced Materials : A Review (2012–2022)
Stoja L. Milovanović, Ivana Lukic, Gabrijela Horvat, Zoran Novak, Sulamith Frerich, Marcus Petermann, Carlos A. García-González, 2023, pregledni znanstveni članek

Opis: This review provides a concise overview of up-to-date developments in the processing of neat poly(lactic acid) (PLA), improvement in its properties, and preparation of advanced materials using a green medium (CO2 under elevated pressure). Pressurized CO2 in the dense and supercritical state is a superior alternative medium to organic solvents, as it is easily available, fully recyclable, has easily tunable properties, and can be completely removed from the final material without post-processing steps. This review summarizes the state of the art on PLA drying, impregnation, foaming, and particle generation by the employment of dense and supercritical CO2 for the development of new materials. An analysis of the effect of processing methods on the final material properties was focused on neat PLA and PLA with an addition of natural bioactive components. It was demonstrated that CO2-assisted processes enable the control of PLA properties, reduce operating times, and require less energy compared to conventional ones. The described environmentally friendly processing techniques and the versatility of PLA were employed for the preparation of foams, aerogels, scaffolds, microparticles, and nanoparticles, as well as bioactive materials. These PLA-based materials can find application in tissue engineering, drug delivery, active food packaging, compostable packaging, wastewater treatment, or thermal insulation, among others.
Ključne besede: aerogels, drying, foaming, impregnation, particle generation, PLA
Objavljeno v DKUM: 06.02.2024; Ogledov: 246; Prenosov: 16
.pdf Celotno besedilo (5,02 MB)
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3rd International Conference on Aerogels for Biomedical and Environmental Applications : book of abstracts

Opis: The 3rd lnternational Conference on Aerogels for Biomedical and Environmental Applications, organized by the Faculty of Chemistry and Chemical Engineering University of Maribor and the AERoGELS COST Action, presented the latest research results and applications of aerogels. This publication compiles the abstracts of the conference and highlights the main results and innovations. The abstracts address the use of aerogels in medical, pharmaceutical, and food applications, including drug delivery systems, scaffolds tor tissue engineering, and bioactive coatings. They also explore aerogels as catalysts, insulators, and environmental solutions and investigate improved catalytic activity and thermal insulation properties. The abstracts emphasize interdisciplinary collaboration and provide ideas tor future research directions. This publication provides valuable insights tor researchers and industry professionals interested in harnessing the remarkable properties of aerogels for biomedical and environmental purposes.
Ključne besede: aerogels, advanced materials, environmental applications, biomedical applications, research and development
Objavljeno v DKUM: 11.08.2023; Ogledov: 406; Prenosov: 62
.pdf Celotno besedilo (12,27 MB)
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Formation, characterization and application of polysaccharide aerogels
Gabrijela Horvat, 2018, doktorska disertacija

Opis: The aim of this PhD dissertation was to describe and analyze the preparation and characterization of polysaccharide aerogels and their future pharmaceutical and medical application. For the research, we used four types of polysaccharides: pectin, alginate, xanthan and guar. We used two types of pectin, high-methoxyl and low-methoxyl pectin, because of their different gelation mechanisms. The first part of the dissertation describes the preparation and characterization of pure polysaccharide aerogels. First, we prepared pectin spherical aerogels, cross-linked with three different ions, and we investigated their final properties. Later, we developed a new method for the preparation of alginate, pectin, xanthan and guar aerogels. We used only ethanol and no other cross-linkers. Ethanol was removed in the later processes of supercritical drying, and the remaining final material was thus only porous polysaccharide. By this method, we were able to prepare pure xanthan and guar aerogels. Prior to this study, xanthan and guar aerogels were prepared only as composites. Pectin aerogels prepared by the new method have amazing properties. On the other hand, alginate aerogels show poor characteristics, and thus the methods need to be optimised. We tried different alginate viscosities, different alcohols (methanol, ethanol, 1-propanol and 1-butanol), and we investigated longer (24h) and shorter (1h) gel setting times. The second part of this dissertation describes the pharmaceutical and medical applications of prepared aerogels. The release of diclofenac sodium from spherical pectin aerogels was investigated in vitro. Calcium cross-linked aerogels were not able to retain the drug, and its release was immediate. In order to achieve controlled release of diclofenac sodium, zinc ions had to be used as cross-linkers. Later, a low water-soluble drug, nifedipine, was used as a model drug for the monolithic aerogels prepared by the new method. The release of nifedipine from pectin and alginate aerogels was highly increased, compared to the crystalline drug. This result is promising for future evaluation of these materials for increasing the bioavailability of poorly water-soluble drugs. Nifedipine release from xanthan and guar aerogels was prolonged up to two weeks. This result reveals a new perspective on such materials for their potential use in medicine as implants and local drug delivery. According to these results, we then developed a new coating material for medical-grade stainless steel from xanthan and pectin. An aerogel coating was loaded with diclofenac sodium and indomethacin, and their release profiles were investigated in vitro. Electrochemical analysis and cell tests proved the safety of such materials for use in medicine. Using aerogel coatings, the drug can be introduced locally into the body; therefore, the need for intravenous, post-operational treatment is greatly reduced.
Ključne besede: polysaccharides, aerogels, supercritical drying, drug carriers
Objavljeno v DKUM: 09.04.2018; Ogledov: 1976; Prenosov: 274
.pdf Celotno besedilo (5,84 MB)

Preparation of WO[sub]3 aerogel catalysts using supercritical CO[sub]2
Zoran Novak, Petra Kotnik, Željko Knez, 2004, izvirni znanstveni članek

Opis: Single tungsten oxide aerogels (WO3), binary oxide aerogels (WO3-Al2O3) and ternary oxide aerogels (WO3-SiO2-Al2O3) were prepared using standard sol-gel route. Tungsten oxide tetraethoxide (WO(OCH2CH3)4) was used as the sol-gel precursor. The excellent properties of the gels obtained by the sol-gel synthesis were preserved upon supercritical drying with CO2. After supercritical drying at 40 °C and 100 bar, all aerogels were calcined to 800 °C. The influence of the synthesis parameters on the catalytic activity of WO3as supported on silica andžor alumina aerogels was investigated through thetransformation of N-(phosphonomethyl)iminodiacetic acid to N-(phosphonomethyl)glycine. Despite including WO3 into single and mixed silicaand alumina aerogels, high specific surface areas (284-653 m2 g-1) were preserved. Higher conversion was obtained for catalysts with higher ratios of WO3 in the mixed silica-alumina aerogels that were calcined at 800 °C.
Ključne besede: chemical processing, aerogels, catalysts, tungsten oxides, preparation of aerogels, characterisation of aerogels, supercritical CO2, supercritical drying, high pressure technology
Objavljeno v DKUM: 01.06.2012; Ogledov: 2023; Prenosov: 45
URL Povezava na celotno besedilo

Synthesis and use of organic biodegradable aerogels as drug carriers
Anja Veronovski, Zoran Novak, Željko Knez, 2012, izvirni znanstveni članek

Opis: Aerogels of natural polysaccharides possess both biocharacteristics of polysaccharides, such as good biological compatibility and cell or enzyme-controlled degradability, and aerogel characteristics, such as very high porosity and specific surface areas that makes them highly attractive in drug delivery. Biodegradable alginate aerogels were synthesized via a sol-gel process. In the present work two methods of ionic cross-linking were used to prepare alginate hydrogels as monoliths and spheres, which can be further easily converted to high surface area aerogels. The aerogels obtained were further used as drug carriers. We investigated the effect of process parameters, such as starting concentration and viscosity of alginate solution, on synthesis products and on model drug (nicotinic acid) release. The results indicate that by using the internal setting cross-linking method for obtaining monolithic aerogels nicotinic acid was released in a more controlled manner. The aerogels thus obtained also exhibited smaller volume shrinkage than the ones described in other publications. However, with increasing alginate concentration in both types of synthesis more compact and cross-linked aerogels were formed.
Ključne besede: organic biodegradable gels, natural polysaccharides, aerogels, drug cariers
Objavljeno v DKUM: 01.06.2012; Ogledov: 2314; Prenosov: 108
URL Povezava na celotno besedilo

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