96 research outputs found
Preclinical biological and physicochemical evaluation of two-photon engineered 3D biomimetic copolymer scaffolds for bone healing
No full textA major challenge in orthopedics is the repair of large non-union bone fractures. A promising therapy for this indication is the use of biodegradable bioinspired biomaterials that stabilize the fracture site, relieve pain and initiate bone formation and healing. This study uses a multidisciplinary evaluation strategy to assess immunogenicity, allergenicity, bone responses and physicochemical properties of a novel biomaterial scaffold. Two-photon stereolithography generated personalized custom-built scaffolds with a repeating 3D structure of Schwarz Primitive minimal surface unit cell with a specific pore size of ∼400 μm from three different methacrylated poly(D,L-lactide-co-ε-caprolactone) copolymers with lactide to caprolactone monomer ratios of 16 : 4, 18 : 2 and 9 : 1. Using in vitro and in vivo assays for bone responses, immunological reactions and degradation dynamics, we found that copolymer composition influenced the scaffold physicochemical and biological properties. The scaffolds with the fastest degradation rate correlated with adverse cellular effects and mechanical stiffness correlated with in vitro osteoblast mineralization. The physicochemical properties also correlated with in vivo bone healing and immune responses. Overall these observations provide compelling support for these scaffolds for bone repair and illustrate the effectiveness of a promising multidisciplinary strategy with great potential for the preclinical evaluation of biomaterials
Functional performance of a bi-layered chitosan-nano-hydroxyapatite osteochondral scaffold: a pre-clinical <i>in vitro</i> tribological study
No full textOsteochondral grafts are used for repair of focal osteochondral lesions. Autologous grafts are the gold standard treatment; however, limited graft availability and donor site morbidity restrict use. Therefore, there is a clinical need for different graft sources/materials which replicate natural cartilage function. Chitosan has been proposed for this application. The aim of this study was to assess the biomechanics and biotribology of a bioresorbable chitosan/chitosan-nano-hydroxyapatite osteochondral construct (OCC), implanted in an in vitro porcine knee experimental simulation model. The OCC implanted in different surgical positions (flush, proud and inverted) was compared to predicate grafts in current clinical use and a positive control consisting of a stainless steel graft implanted proud of the cartilage surface. After 3 h (10 800 cycles) wear simulation under a walking gait, subsidence occurred in all OCC samples irrespective of surgical positioning, but with no apparent loss of material and low meniscus wear. Half the predicate grafts exhibited delamination and scratching of the cartilage surfaces. No graft subsidence occurred in the positive controls but wear and deformation of the meniscus were apparent. Implanting a new chitosan-based OCC either optimally (flush), inverted or proud of the cartilage surface resulted in minimal wear, damage and deformation of the meniscus
Tubular Scaffold with Shape Recovery Effect for Cell Guide Applications
No full textTubular scaffolds with aligned polylactic acid (PLA) fibres were fabricated for cell guide applications by immersing rolled PLA fibre mats into a polyvinyl acetate (PVAc) solution to bind the mats. The PVAc solution was also mixed with up to 30 wt % β-tricalcium phosphate (β-TCP) content. Cross-sectional images of the scaffold materials obtained via scanning electron microscopy (SEM) revealed the aligned fibre morphology along with a significant number of voids in between the bundles of fibres. The addition of β-TCP into the scaffolds played an important role in increasing the void content from 17.1% to 25.3% for the 30 wt % β-TCP loading, which was measured via micro-CT (µCT) analysis. Furthermore, µCT analyses revealed the distribution of aggregated β-TCP particles in between the various PLA fibre layers of the scaffold. The compressive modulus properties of the scaffolds increased from 66 MPa to 83 MPa and the compressive strength properties decreased from 67 MPa to 41 MPa for the 30 wt % β-TCP content scaffold. The scaffolds produced were observed to change into a soft and flexible form which demonstrated shape recovery properties after immersion in phosphate buffered saline (PBS) media at 37 °C for 24 h. The cytocompatibility studies (using MG-63 human osteosarcoma cell line) revealed preferential cell proliferation along the longitudinal direction of the fibres as compared to the control tissue culture plastic. The manufacturing process highlighted above reveals a simple process for inducing controlled cell alignment and varying porosity features within tubular scaffolds for potential tissue engineering applications
A review of natural fibres and biopolymer composites : progress, limitations, and enhancement strategies
No full textThe interest in natural fibres and biopolymers for developing bio-composites has greatly increased in recent years, motivated by the need to reduce the environmental impact of traditional synthetic, fossil fuel-derived materials. However, several limitations associated with the use of natural fibres and polymers should be addressed if they are to be seriously considered mainstream fibre reinforcements. These include poor compatibility of natural fibres with polymer matrices, variability, high moisture absorption, and flammability. Various surface treatments have been studied to tackle these drawbacks, such as alkalisation, silane treatment, acetylation, plasma treatment, and polydopamine coating. This review paper considers the classification, properties, and limitations of natural fibres and biopolymers in the context of bio-composite materials. An overview of recent advancements and enhancement strategies to overcome such limitations will also be discussed, with a focus on mechanical performance, moisture absorption behaviour, and flammability of composites. The limitations of natural fibres, biopolymers, and their bio-composites should be carefully addressed to enable the widespread use of bio-composites in various applications, including electronics, automotive, and construction
A Review of Natural Fibres and Biopolymer Composites: Progress, Limitations, and Enhancement Strategies
No full textThe interest in natural fibres and biopolymers for developing bio-composites has greatly increased in recent years, motivated by the need to reduce the environmental impact of traditional synthetic, fossil fuel-derived materials. However, several limitations associated with the use of natural fibres and polymers should be addressed if they are to be seriously considered mainstream fibre reinforcements. These include poor compatibility of natural fibres with polymer matrices, variability, high moisture absorption, and flammability. Various surface treatments have been studied to tackle these drawbacks, such as alkalisation, silane treatment, acetylation, plasma treatment, and polydopamine coating. This review paper considers the classification, properties, and limitations of natural fibres and biopolymers in the context of bio-composite materials. An overview of recent advancements and enhancement strategies to overcome such limitations will also be discussed, with a focus on mechanical performance, moisture absorption behaviour, and flammability of composites. The limitations of natural fibres, biopolymers, and their bio-composites should be carefully addressed to enable the widespread use of bio-composites in various applications, including electronics, automotive, and construction
Very ductile polymer concrete using carbon nanotubes
No full textReda Taha, Mahmoud M./0000-0002-3707-9336; Emiroglu, Mehmet/0000-0002-0214-4986WOS: 000456755400042Polymer concrete (PC) is a type of concrete where a polymer is used to replace cement as the binder. PC is an impermeable and chemical resistant concrete with appreciable mechanical properties. However, for most structural engineers, PC advantages do not outweigh its higher cost when compared with normal cement concrete. We report on the production of very ductile PC (measured by tensile strain at failure) with appreciable tensile strength utilizing a hybrid mixture of pristine and carboxyl (COOH) functionalized multi-walled carbon nanotubes (MWCNTs) at 2.0 wt% of epoxy resin. Experimental investigations reveal that COOH functionalization maximizes PC ductility reaching unprecedented 5.5% failure strains and increasing toughness by 184%. Fourier transformation infrared spectroscopy and dynamic modulus analysis indicate an increase in crosslinking density of the epoxy matrix up to 84% due to the carbonyl band formation induced by the COOH functionalization of MWCNTs. The significant improvement in ductility and energy absorption provides a promising platform for creating very ductile PC with attractive properties. (C) 2018 Elsevier Ltd. All rights reserved.Southern Plains Transportation Center (SPTC), US Department of Transportation; Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK); Egyptian Science and Technology Development FundScience and Technology Development Fund (STDF) [STDF-CSE 5213]This work has been funded by Southern Plains Transportation Center (SPTC), US Department of Transportation, contract to The University of New Mexico. The authors greatly acknowledge this support. The second author acknowledges financial support from the Scientific and Technological Research Council of Turkey (TUBITAK) BIDEB-2219 Postdoctoral Research program. Finally, support to the third author by the Egyptian Science and Technology Development Fund (STDF-CSE 5213) is also appreciated. Donation of polymer concrete materials by Transpo Industries, Inc. is much acknowledged
Carlas von Schmithas ir Druskininkų kurorto pradžia
No full textAlbumo Necrolithuanica autoriaus Carlo von Schmitho (apie 1795–1797–1876) pavardę ne kartą minėjo istorikai, rašę apie Druskininkų kurorto pradžią: 1838 m. Druskininkų mineralinių vandenų prižiūrėtojas von Schmithas kartu su kitais dviem savo kolegomis tapo pirmaisiais valstybės iždo išlaikomais miesto tarnautojais. Antra vertus, Druskininkų genezės temą gvildenę tyrėjai niekuomet neapsistojo prie jų veiklos analizės, taigi nebuvo aptarti ir von Schmitho tarnybos aspektai. Todėl straipsnyje siekiama rekonstruoti albumo Necrolithuanica autoriaus gyvenimą Druskininkuose – tiek jo kasdienybę, susijusią su mineralinių vandenų prižiūrėtojo funkcijomis (statybų priežiūra, į kurortą atvykstančių svečių registracija, įvažiavimo mokesčio rinkliava ir kt.), tiek ir jo laisvalaikį, pašvęstą didžiajai jo aistrai – archeologijai. Šaltinių analizė parodė, kad per tuos pora metų (iš Druskininkų išvyko 1840 m.) von Schmitho archeologijos kolekcija buvo gerokai papildyta – ne tik radiniais iš jau žinomų Druskininkų apylinkių radimviečių, bet ir „archeologiniais netikėtumais“, kuriuos pateikė jo prižiūrimi kurorto statybų darbai. Tą patvirtina ir albumas Necrolithuanica, kuriame iš 321 ten užfiksuotų archeologinių daiktų piešinių 18 yra ir iš Druskininkų. Mums šiandien šie piešiniai yra itin vertingi: beveik nėra duomenų, kokiu būdu von Schmithas surinko savo archeologijos kolekciją, kaip ir kada kasinėjo, tuo tarpu Druskininkų radinių istoriją, jų aplinkybes šiandien jau galime ne tik nujausti, bet ir gana tiksliai datuoti Reikšminiai žodžiai: Prižiūrėtojai; KurortaiHistorians writing on the origins of Druskininkai resort often mentioned the name of Carl von Schmith (circa 1795–1797–1876), the author of Necrolithuanica album: in 1838, a supervisor of Druskininkai mineral waters, von Schmith, together with other two colleagues became the first city servants financed from the state budget. On the other hand, researchers exploring genesis of Druskininkai never paused at analyzing their activities, thus ignoring the features of von Schmith’s service. For this reason, the article aims to reconstruct the life of the author of Necrolithuanica album in Druskininkai: the author includes both – his everyday life related to the supervision of mineral waters (oversight of constructions, registration of guests arriving at the resort, collection of entry tax and so on) and his free time, mostly devoted to his greatest passion - archaeology. Analysis of data sources has revealed that in the period of those few years von Schmith’s archaeological collection was significantly expanded to include not only findings from already known sties around Druskininkai, but also from “archaeological surprises” unearthed during supervision of construction works taking place in the resort. This fact is confirmed by Necrolithuanica album, whose list of 321 illustrations of archaeological items includes 18 drawings from Druskininkai. These drawings are of particular value: there is almost no information about how von Schmith assembled his archaeological collection, when and where excavations took place, in contrast, the history of the Druskininkai findings, circumstances surrounding their recovery, can be not only intuited, but also accurately dated
Improved phosphate‐based glass fiber performance achieved through acid etch/polydopamine treatment
No full textPhosphate based glass fibres (PGF) are of interest as reinforcements for degradable implants, but have seen limited application due to their rapid loss of strength when subjected to aqueous conditions. Previous studies have utilised heat treatments to improve longer term strength retention at a significant cost to initial strength. In this study, acid etching is used to recover the initial fibre strength after heat treatment and a subsequent coating of polydopamine is applied to provide longer term retention of this recovered strength. After an initial loss of strength after heat treatment (1135-> 509 MPa), an optimised combination of acid treatment and polydopamine coating was able to recover to approximately 85% of the initial strength (969 MPa). The result was significant in comparison to acid treatment (647 MPa) or coating (688 MPa) alone. The combined acid/coating treatment was demonstrated to maintain fibre properties for at least 14 days, although the amount of polydopamine coating was observed to decrease over this period. The approach reported here is of importance as it offers the require
Motiejus Valančius' list of rare Lithuanian books
No full textLietuvos mokslų akademijos Vrublevskių bibliotekos Rankraščių skyriuje (toliau – LMAVB RS), Augustino Janulaičio (1878–1950) fonde (f. 267, b. 1492), saugoma rankraštinė knyga, priklausiusi Motiejaus vel Motiejaus Kazimiero Valančiaus (Maciej Kazimierz Wołonczewski, 1801–1875) asmeninei bibliotekai (archyvui) (toliau – VRK) (žr. 1 pav.). Šis dokumentas neįtrauktas į dirbtinai suformuotą, nes ne spaudai (!) skirtų Valančiaus rankraščių rinkinį, šiandien žinomą bendru "Pamiętnik Domowy" (Namų užrašai) vardu. 2003 m. rengiant naują šio rinkinio laidą (pirmoji – 1929 m.) Janulaičio fondas nebuvo „patikrintas“ (priešingai nei LMAVB RS fondai „Literatūrinių rankraščių kolekcija“ [f. 29] ir „Valentina Horoškevičiūtė“ [f. 98]), nors nuo 1911 m. kaip tik šis istorikas ypač domėjosi ad se ipsum rašytu Valančiaus palikimu, kritikavo Vaižgantą (tikr. Juozas Tumas, 1869–1933) dėl nepreciziško šių dokumentų skelbimo, siekė parengti naują visavertę (ir originalo kalba) jų publikaciją. Paieškoti Valančiaus rankraščių Janulaičio fonde vertėjo dar ir dėl tos priežasties, kad ten nukeliavo ir vienas kitas kadaise Eduardo Volterio (Эдуард Александрович Вольтер, 1856–1941) turėtas rankraštis. Volteris ne tik domėjosi Valančiaus palikimu, bet 1886 m. ekspedicijos po Lietuvą metu gavo (įsigijo?) kai kuriuos Žemaičių vyskupo rankraščius [...] 1986 m. Vladas Žukas (1925–2014), rašydamas apie Vаlančiaus santykį su lietuviška knyga, atkreipė dėmesį, kad Volteris 1887 m. spaudoje skelbtoje ataskaitoje Imperatoriškajai mokslų akademijai Sankt Peterburge (prieš tai buvo pateikta citata kaip tik iš šio leidinio) „minėjo jo [Valančiaus – R. G.] užrašus apie perskaitytas retas lietuviškas knygas“. Tačiau Žukas Valančiaus sąrašo pats nematė – žinojo tik iš Volterio. Antrą kartą šį dokumentą netiesiogiai paminėjo 1989 m. rašydamas apie Volterio senosios lietuviškos knygos tyrimus, konkrečiai – Samuelio Boguslavo Chylinskio8 Bibliją: „Jis [Volteris – R. G.] apžvelgė spaudoje užfiksuotus duomenis (J. J. Kvanto, L. Rėzos, M. Stankevičiaus), nurodė, kad bibliją skaitė ir trumpai aprašė M. Valančius“. [...] XX a. 9 dešimtmetyje Žukas informaciją atgaivino, tačiau, kaip minėta, toliau nežengė. Gina Kavaliūnaitė išsamiai aptarė Kuniko ir Volterio nuopelnus ieškant Chylinskio Biblijos Vilniaus egzemplioriaus, tačiau Valančiaus skaitytų ir matytų knygų sąrašu, kuriame buvo apibūdintas kaip tik šis veikalas (paskutinė sąrašo pozicija), nesusidomėjo. Tad net galėjo susidaryti įspūdis, kad toks sąrašas ir visai neegzistavo, juolab kad Volteris pacitavo tik vieną jo sakinį. Abejones išsklaidė minėta LMAVB RS saugoma VRK, o tiksliau, į ją įrištas Valančiaus ranka rašytas dokumentas „Spis Ksiązek Ƶmudzkich które niegdyś czytałem“ („Kitados skaitytų žemaitiškų knygų sąrašas“; toliau – SKƵ). [...]The Augustinas Janulaitis (1878–1950) Fund (F267-1492) in the Manuscript Department of the Wroblewski Library of the Lithuanian Academy of Sciences is home to a book from the personal collection of the Samogitian Bishop Motiejus Kazimieras Valančius (in Polish Maciej Kazimierz Wołonczewski, 1801–1875). This archivalia has not yet received any amount of scholarly attention. The book is considered part of the so-called silva rerum, a collection of 18 documents of varying genres and content handwritten by Valančius or someone else in Polish, Russian, Latin and Lithuanian, including a number of statutes, privileges, old legal and ecclesiastical documents, extracts from works of literature and historical tracts, a translation, a poem, and so on. Pending detailed research into the contents of these documents and the paper on which they are written, we should stick to 1834 and 1845 as the dates bookending the creation of this book manuscript (seeing as these dates are recorded therein). In turn, we can assume that the documents were bound into a book some time after 1861 (as referenced by the relief imprint of tree branches and an inscription that reads "Нововеркская фабрика № 6" on the extra blank pages of the book). The publication features one element of this book: a list of 21 Lithuanian books Valančius once read. That is Valančius’ signature. The books are not listed in chronological or alphabetical order. The metrics of the publications are not necessarily written down with any degree of precision. Valančius kept some of the books in his library, he read others elsewhere (for instance, in the Library of the Spiritual Academy of Roman Catholics in St Petersburg). The editions of the books date from between 1579 and 1842 (two books are dated 1579, one is dated 1599, one 1660, one 1629, one 1713, one 1737, one 1745, two 1747, one 1755, three 1781, two 1800, two 1823, one 1829, one 1841, one 1842). Valančius provided a commentary on each of the books on the list, with one exception, Маłdos Krikszczioniszkos (1781, author unknown). Only six of the books received any sort of acclaim from him. Seven of the books he appraised in terms of their language as well. The document published here supports, once again, the findings of researchers who conducted a probe into the library of the Samogitian bishop: (1) Valančius was not an avid bibliophile, but he had a passion for reading and a strong opinion about books (and not just religious books); (2) he would never write any comments on a book down in Lithuanian (using Polish or Latin instead); (3) his opinion would always be spot-on, he was able to critically evaluate the pros and the cons of a book. The list of Lithuanian books that is published here also confirms, and not for the first time, that Valančius treasured the Lithuanian book, just as he considered himself an expert in the Lithuanian language. The book handwritten by Valančius was procured by Eduardas Volteris (in Russian Эдуард Александрович Вольтер; in Latvian Eduards Volters, 1856–1941) during his 1887 ethnographic trip across Lithuania. Later, it made its way into Janulaitis’ archives (as did quite a few of Volter’s other documents). Volter was also the first to mention the most ‘Lithuanian’ element of the book, the list of Lithuanian books drawn up by Valančius that is published here, in the press in 1887
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