1. Solidification of gelatine hydrogels by using a cryoplatform and its validation through CFD approachesYasir Beeran Potta Thara, Miha Jordan, Timi Gomboc, Blaž Kamenik, Boštjan Vihar, Vanja Kokol, Matej Zadravec, 2022, izvirni znanstveni članek Opis: In this work, we developed a numerical approach based on an experimental platform
to determine the working conditions on a cryoplatform and to predict and evaluate the cryogenic
printing of hydrogels. Although hydrogels have good biocompatibility, their material properties
make it difficult to print them with high precision and shape fidelity. To overcome these problems, a
cryogenic cooling platform was introduced to accelerate the physical stabilisation of each deposited
layer during the printing process. By precisely controlling solidification (crystallisation), each printed
material can withstand its own weight to maintain shape fidelity, and the porosity of the scaffolds
can also be controlled more selectively. The thermophysical properties of gelatine hydrogels were
investigated to gain a better understanding of the phase change upon freezing. The corresponding
material properties and experimental observations of gelatine solidification served as the basis for
developing a computational fluid model (CFD) to mimic the solidification of gelatine hydrogels
using a cryoplatform at different process conditions and extruder speeds. The goal was to develop a
tool simple enough to predict acceptable process conditions for printing gelatine hydrogels using
a cryoplatform.
Ključne besede: gelatine, hydrogel, cryoprinting, CFD simulation, solidification modelling
Objavljeno v DKUM: 20.03.2025; Ogledov: 0; Prenosov: 7
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2. Effect of peptides' binding on the antimicrobial activity and biocompatibility of protein-based substrates Maja Kaisersberger Vincek, 2017, doktorska disertacija Opis: This work reveals the effect of coupling approach (chemical by using carbodiimide chemistry and grafting-to vs. grafting-from synthesis routes, and enzymatic by using transglutaminase) of a hydrophilic ε-poly-L-lysine (εPL) and an amphiphilic oligo-acyl-lysyl (OAK) derivative (K-7α12-OH) to wool fibers and gelatine (GEL) macromolecules, respectively, and substrates antibacterial activity against Gram-negative E. coli and Gram-positive S. aureus bacteria after 1–24 h of exposure, as well as their cytotoxicity. Different spectroscopic (ultraviolet-visible, infrared, fluorescence and electron paramagnetic resonance) and separation techniques (size-exclusion chromatography and capillary zone electrophoresis) as well as zeta potential and potentiometric titration analysis, were performed to confirm the covalent coupling of εPL/OAK, and to determine the amount and orientation of its immobilisation.
The highest and kinetically the fastest level of bacterial reduction was achieved with wool/GEL functionalised with εPL/OAK by chemical grafting-to approach. This effect correlated with both the highest grafting yield and conformationally the highly-flexible (brush-like) orientation linkage of εPL/OAK, implicating on the highest amount of accessible amino groups interacting with bacterial membrane. However, OAK`s amphipathic structure, the cationic charge and the hydrophobic moieties, resulted to relatively high reduction of S. aureus for grafting-from and the enzymatic coupling approaches using OAK-functionalised GEL.
The εPL/OAK-functionalised GEL did not induce toxicity in human osteoblast cells, even at ~25-fold higher concentration than bacterial minimum inhibitory (MIC) concentration of εPL/OAK, supporting their potential usage in biomedical applications.
It was also shown that non-ionic surfactant adsorbs strongly onto the wool surface during the process of washing, thereby blocking the functional sites of immobilized εPL and decreases its antibacterial efficiency.
Ključne besede: wool, gelatine, antimicrobial peptides, ε-poly-L-lysine, oligo-acyl-lysyl, grafting chemistry, grafting approach, peptide orientation, antibacterial activity, cytotoxicity
Objavljeno v DKUM: 17.08.2017; Ogledov: 1931; Prenosov: 180
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3. Water sorption characteristics of a new type of gelatine powder, produced by a new high-pressure micronisation processChristian Reibe, Željko Knez, 2010, izvirni znanstveni članek Opis: A new high-pressure micronisation process for Gelatine has been developed. By applying this process to gelatine, a new type of Gelatine was produced: Dry and pure Gelatine powder of high molecular mass. This powder was investigated,regarding its sorption behaviour and compared to its feedstock material. The feedstock Gelatine was of type B 200 Bloom, 6 mesh, having a molecular mass of 150,000 g $mol^{-1}$. The produced Gelatine powder's molecular mass was around 130,000 g $mol^{-1}$, while its mean particle size was 300 μm. Their sorption isotherms were investigated at 30 °C, 40 °C and 60 °C and water activities in the range from 0.055 to 0.836. At given water activities the Equilibrium Moisture Contents (EMC) decreases with increasing temperature.The measured sorption isotherms were fit with the Brunauer- Emmet-Teller (BET)- model and the Guggenheim- Anderson- deBoer (GAB)- model. Both models described the adsorption behaviour well in their range of validity, while only the GAB-model was adequate for describing the desorption behaviour. Hysteresis effect occurred in each adsorption-desorption pair. The isosteric heat of sorption of both substances was determined for adsorption, desorption respectively. Slight differences in the sorption behaviour occurred due to processing, while quality of the gelatine was not affected.
Ključne besede: $CO_2$ spray drying, gelatine powder, sorption isotherms, isosteric heat of sorption, Guggenheim-Anderson-deBoer model, Brunauer-Emmet-Teller model
Objavljeno v DKUM: 10.07.2015; Ogledov: 1887; Prenosov: 84
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5. The development of a new process for gentle drying, micronisation and formulation of a high viscous biopoymerChristian Reibe, 2011, doktorska disertacija Opis: Biopolymers are characterised by their biodegradable behaviour in certain environments. Especially the development of natural biopolymers from renewable resources is gathering increasing interest in the scientific as well as in the industrial sectors . Since Biopolymers may be tailored to specific requirements, the encapsulation of pharmaceutical compounds or flavours in biopolymers would open wide avenues for the production of controlled- release systems. Most common mechanical pulverisation processes are milling and grinding. With these processes it is not possible to produce specific morphologies like foams or hollow spheres, but always splintered edges. Encapsulation is carried out by common precipitation techniques.
Gelatine, as a widely applied biopolymer, represents one example of those substances of large interest, but it is difficult to process. Especially gelatines with high molecular mass are difficult or almost impossible to be pulverized by spray drying techniques, due to their high viscosity.
In the frame of this research work, an integrated high-pressure spraying, drying and pulverization process for high viscous gelatine was developed, based on a combination of the water removing effects "Evaporation" and "Gas-solubility". The resulting products were dry, free-flowing gelatine powders, still exhibiting high molecular masses. Due to the new, gentle method of processing, a completely new gelatine product with unique properties was obtained. Even the encapsulation of edible oil in high ratios was found to be possible with this new process. The characterisation was carried out by standard methods for gelatine on the one hand side, and standard procedures for characterising powders on the other hand side.
The developed process was patented under the identifier "WO 002009135601 A1".
Ključne besede: High Pressure Process, Supercritical Fluids, High molecular mass Gelatine, Micronisation, CO-2 - spray drying, Encapsulation, Gelatine Powder
Objavljeno v DKUM: 26.01.2011; Ogledov: 3525; Prenosov: 268
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