Iskanje po katalogu digitalne knjižnice

Opis: Effective microvascular tissue engineering requires fibroblasts that remain phenotypically stable and secrete extracellular matrix (ECM) proteins and growth factors relevant for vascularization. This study evaluated 3D printed hydrogels based on sodium alginate (ALG) and carboxymethyl cellulose (CMC) to assess their ability to sustain fibroblast phenotype, ECM deposition, and angiogenic growth factor secretion during long-term culture. Seven formulations – including one with nanofibrillated cellulose – were compared by encapsulating fibroblasts and crosslinking with CaCl₂ or SrCl₂. All scaffolds were printable and exhibited comparable degradation profiles. Mechanical testing indicated stable compressive response, with Sr2+-crosslinked hydrogels generally showing higher apparent compressive modulus, while Ca2+-crosslinked scaffolds supported slightly higher cell viability. Encapsulated fibroblasts retained their phenotype for 30 days, evidenced by steadily increasing collagen I/III and fibronectin deposition, alongside sustained expression of specific fibroblast markers. After 30 days, all groups produced comparable levels of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF-2), with one formulation yielding a significantly higher FGF-2 output. This multiparametric study demonstrates that scaffold composition and crosslinker chemistry influence fibroblast phenotype maintenance, ECM deposition, and growth factor secretion. To our knowledge, this is the first systematic, 30-day screening of ALG-CMC hydrogels – tuned by polymer content, NFC addition, and Ca2+/Sr2+ crosslinking – specifically for their ability to sustain fibroblast phenotype, extracellular matrix deposition, and growth factor secretion, providing design considerations to guide bioink development for microvascular models.
Ključne besede: 3D bioprinting, alginate, cellulose, skin fibroblast, microvasculature, angiogenesis
Objavljeno v DKUM: 18.12.2025; Ogledov: 0; Prenosov: 2
Celotno besedilo (10,79 MB)
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Opis: A conventional compound fabric was used to develop a modern, multifunctional material with an auxetic behaviour and a tailored open area for particle filtration. Such material was produced using traditional textile technology and laser cutting, to induce a rotating squares unit geometry. The behaviour was investigated of three different rotating unit cell sizes. The laser slit thickness and the length of the hinges were equal for all three-unit cells. The tensile properties, Poisson’s ratio and auxetic behaviour of the tested samples were investigated, especially the influence of longitudinal displacement on the fabric’s open area and the filtered particle sizes (average and maximum). Results show that the developed compound fabric possesses an average negative Poisson’s ratio of up to −1, depending on the applied auxetic geometry. The larger rotating cell size samples offer a higher average negative Poisson’s ratio and a higher breaking strength due to the induced slits. The findings highlight the usefulness of patterned cuts in conventional textile materials to develop advanced auxetic textile materials with tailored geometrical and mechanical properties.
Ključne besede: compound textile material, auxetic structure, open area, filtration, mechanical properties, Poisson’s ratio
Objavljeno v DKUM: 25.03.2025; Ogledov: 0; Prenosov: 12
Celotno besedilo (2,67 MB)
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Opis: Lower-limb prosthesis design and manufacturing still rely mostly on the workshop process of trial-and-error using expensive unrecyclable composite materials, resulting in time-consuming, material-wasting, and, ultimately, expensive prostheses. Therefore, we investigated the possibility of utilizing Fused Deposition Modeling 3D-printing technology with inexpensive bio-based and bio-degradable Polylactic Acid (PLA) material for prosthesis socket development and manufacturing. The safety and stability of the proposed 3D-printed PLA socket were analyzed using a recently developed generic transtibial numeric model, with boundary conditions of donning and newly developed realistic gait cycle phases of a heel strike and forefoot loading according to ISO 10328. The material properties of the 3D-printed PLA were determined using uniaxial tensile and compression tests on transverse and longitudinal samples. Numerical simulations with all boundary conditions were performed for the 3D-printed PLA and traditional polystyrene check and definitive composite socket. The results showed that the 3D-printed PLA socket withstands the occurring von-Mises stresses of 5.4 MPa and 10.8 MPa under heel strike and push-off gait conditions, respectively. Furthermore, the maximum deformations observed in the 3D-printed PLA socket of 0.74 mm and 2.66 mm were similar to the check socket deformations of 0.67 mm and 2.52 mm during heel strike and push-off, respectively, hence providing the same stability for the amputees. We have shown that an inexpensive, bio-based, and bio-degradable PLA material can be considered for manufacturing the lower-limb prosthesis, resulting in an environmentally friendly and inexpensive solution.
Ključne besede: 3D printing, bio-based, polylactic acid, PLA, prosthesis, prosthesis socket, numerical model, finite element method
Objavljeno v DKUM: 14.03.2024; Ogledov: 208; Prenosov: 46
Celotno besedilo (5,99 MB)
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Ključne besede: nanocelulozni materiali, nanodelci, protimikrobne lastnosti
Objavljeno v DKUM: 25.10.2022; Ogledov: 566; Prenosov: 32
Celotno besedilo (344,50 KB)

Opis: Dandanes predstavlja UV sevanje vedno večji problem, saj se zaradi tanjšanja ozonske plasti povečuje stopnja rakavih obolenj. Ploske tekstilije in oblačila, izdelana iz tekstilij, predstavljajo učinkovito zaščito kože pred UV sevanjem. Tkanine imajo sposobnost odbijanja, absorbiranja in razprševanja UV žarkov. Sposobnost zaščite tkanin pred UV sevanjem je odvisna od konstrukcije tkanin, odločilen pomen pa ima tudi barva tkanine oz. uporabljeno barvilo v fazi barvanja tkanin. Namen magistrskega dela je bil ugotoviti, katera bombažna tkanina nudi najboljšo zaščito pred UV sevanjem oz. analizirati vpliv konstrukcijskih parametrov tkanin in vpliv barve na prepustnost UV sevanja. Tkanine so se med seboj razlikovale po finosti uporabljenih niti, vezavi in gostoti niti (in posledično poroznosti) ter barvi. Rezultati vpliva konstrukcije tkanin na prepustnost UV sevanja so pokazali, da imajo vezava, finost niti in relativna ter absolutna gostota tkanin vpliv na prepustnost UV sevanja, prav tako pa tudi na poroznost tkanin, ki je premo sorazmerna prepustnosti UV sevanja. Večja volumska poroznost pomeni slabšo UV zaščito tkanin. Rezultati vpliva barve na UV prepustnost tkanin so pokazali, da ima barva tkanine oz. vsebnost barvila bistven vpliv na UV zaščito. Analiza prepustnosti UV sevanja tkanin je pokazala, da nudijo ustrezno zaščito pred UV sevanjem (kjer je povprečna vrednost UV prepustnosti nižja od 5 %) tkanine, obarvane z naravnimi barvili iz rdeče pese in orehovih listov, ne glede na finost in nivo relativne gostote, vendar samo v keper in atlas vezavi. Pri tem so izvzete tkanine, izdelane iz niti 14 in 36 tex, v keper vezavi na 1. nivoju relativne gostote. Surove oz. neobdelane tkanine, brez nanosa barvil v bež odtenku, ne dajejo zaščite pred UV sevanjem z izjemo dveh vzorcev, ki so izdelani iz finosti niti 25 tex, v vezavi atlas na 3. nivoju relativne gostote.
Ključne besede: UV sevanje, konstrukcija tkanin, poroznost, barva
Objavljeno v DKUM: 27.09.2018; Ogledov: 1605; Prenosov: 185
Celotno besedilo (2,75 MB)