Hybrid multi-layered scaffolds produced via grain extrusion and electrospinning for 3D cell culture tests

Purpose: The purpose of this paper is to focus on the production of scaffolds with specific morphology and mechanical behavior to satisfy specific requirements regarding their stiffness, biological interactions and surface structure that can promote cell-cell and cell-matrix interactions though proper porosity, pore size and interconnectivity. Design/methodology/approach: This case study was focused on the production of multi-layered hybrid scaffolds made of polycaprolactone and consisting in supporting grids obtained by Material Extrusion (ME) alternated with electrospun layers. An open source 3D printer was utilized, with a grain extrusion head that allows the production and distribution of strands on the plate according to the designed geometry. Square grid samples were observed under optical microscope showing a good interconnectivity and spatial distribution of the pores, while scanning electron microscope analysis was used to study the electrospun mats morphology. Findings: A good adhesion between the ME and electrospinning layers was achieved by compression under specific thermomechanical conditions obtaining a hybrid three-dimensional scaffold. The mechanical performances of the scaffolds have been analyzed by compression tests, and the biological characterization was carried out by seeding two different cells phenotypes on each side of the substrates. Originality/value: The structure of the multi-layered scaffolds demonstrated to play an important role in promoting cell attachment and proliferation in a 3D culture formation. It is expected that this design will improve the performances of osteochondral scaffolds with a strong influence on the required formation of an interface tissue and structure that need to be rebuilt

Analisa Teknis Perancangan Turbin pada Turbocahrger Menggunakan CFD

Fungsi tambahan dari Turbocharger terhadap motor yakni dapat mengurangi SFOC (Specific Fuel Oil Consumption), memperkecil getaran, serta meningkatkan efisiensia. Prinsip kerja dari turbocharger adalah gas buang dari mesin diesel dialirkan menuju gas inlet cashing untuk menggerakan turbin turbocharger, setelah turbin bergerak aliran fluida akan keluar melalui gas outlet cashing. Karena turbin berputar maka shaft turbin yang telah terhubung dengan kompresor otomatis akan memutar impeller kompresor tersebut. Sehingga mengakibatka udara luar masuk melalui air inlet casing, akibat putaran kompresor fluida gas menjadi bertekanan dan dapat mensuplay ke mesin diesel tersebut. Pada penulisan tugas akhir ini akan membahas tentang analisa teknis perancangan turbin turbocharger dengan mevariasikan nilai putaran turbin sejumpah 5000 rpm,10000 rpm, 15000 rpm, 20000 rpm 25000 rpm dan 30000 rpm. Sedangkan mass flow rate fluida disesuaikan dengan exhaust gas mass flow rate berdasarkan kondisi engine 100%, 85%, 75 % sedangkan nilai mass flow rate sebesar 1.7 kg/s, 1.45 kg/s dan 1.28 kg/s. Jumlah blade dan diameter blade telah ditentukan dan tidak mengubah sudut setiap putaran turbin. Analisa menggunakan Computational Fluids Dynamics (CFD) dengan memasukan nilai-nilai yang telah ditentukan. Dengan menghasilkan putaran RPM ketika engine power sebesar 75% maka putaran 18944 RPM,Ketika engine power sebesar 85% maka putaran 22346 RPM.,Ketika engine power sebesar 100% sebesar 26956 RPM

Fatigue behavior and cyclic damage of peek short fiber reinforced composites

Fatigue strength and failure mechanisms of short fiber reinforced (SFR) PEEK have been investigated in the past by several research groups. However some relevant aspects of the fatigue behavior of these materials, like cyclic creep and fatigue damage accumulation and modeling, have not been studied yet, in particular in presence of both fillers and short fibers as reinforcement. In the present research these aspects were considered by carrying out uni-axial fatigue tests in load control (cycle ratio R = 0) on neat PEEK and PEEK based composites reinforced either with short carbon fibers only or with addition of fillers (graphite and PTFE). For each material stress-life curves were obtained and compared. Fatigue fracture surfaces were analyzed to identify failure mechanisms in presence of different reinforcement types. The evolution of cyclic creep strain was also monitored as a function of the number of cycles, thus allowing investigation on the correlation between cyclic creep parameters and fatigue life. The evolution of cyclic damage with loading cycles was then compared by defining a damage parameter related to the specimen stiffness reduction observed during the tests. Progressive cyclic damage evolution of short fiber reinforced PEEK composites presented significantly different patterns depending on applied stress level and on the presence of different reinforcement typologies. In order to reproduce the different fatigue damage kinetics and stages of progressive damage accumulation observed experimentally, a cyclic damage model was finally developed and implemented into a finite element code by which a satisfactory agreement between numerical prediction and experimental data at different stress levels for each examined material

Stress-Free Two-Way Shape Memory Effect of Poly(ethylene glycol)/ Poly(epsilon-caprolactone) Semicrystalline Networks

In this work, poly(ethylene glycol) (PEG)/poly(epsilon- caprolactone) (PCL) semicrystalline networks were prepared by photo-cross-linking of methacrylated macromonomers with different molecular weights and in different proportions to obtain amphiphilic materials capable of displaying properly designed shape memory effects. Networks based on PCL 10 kDa and PEG 3 kDa showed suitable thermal and mechanical properties with well-separated crystallization and melting regions to achieve a self-standing two-way shape memory effect. Particularly, after the application of a specific thermomechanical history, these materials are capable of cyclically changing their shape between two configurations upon cooling-heating cycles in the absence of any external load applied. The effect of the composition of the networks and of the employed thermomechanical parameters, such as the applied strain and the actuation temperature, was investigated to shed light on the shape memory mechanism for this class of materials, which are considered promising for applications in the biomedical field and as reversible actuators for soft robotics

Interactive effects between carbon allotrope fillers on the mechanical reinforcement of polyisoprene based nanocomposites

Interactive effects of carbon allotropes on the mechanical reinforcement of polymer nanocomposites were investigated. Carbon nanotubes (CNT) and nano-graphite with high shape anisotropy (nanoG) were melt blended with poly(1,4- cis-isoprene), as the only fillers or in combination with carbon black (CB), measuring the shear modulus at low strain amplitudes for peroxide crosslinked composites. The nanofiller was found to increase the low amplitude storage modulus of the matrix, with or without CB, by a factor depending on nanofiller type and content. This factor, fingerprint of the nanofiller, was higher for CNT than for nanoG. The filler-polymer interfacial area was able to correlate modulus data of composites with CNT, CB and with the hybrid filler system, leading to the construction of a common master curve. © BME-PT

Master curves for the mechanical reinforcement of diene elastomers with sp2 carbon allotropes

sp2 carbon allotropes are efficient reinforcing fillers for polymer melt and elastomers: carbon black (CB) has been used since early 1900’s and nanofillers such as carbon nanotubes (CNT), graphene and graphene related materials (GRM) have increased their importance over the last decades. Nanofillers can definitely establish larger interfacial area with the polymer matrix than CB and great impact on material properties is thus expected. However, it is widely acknowledged that they will not be able to completely replace CB. Hence, increasing research efforts are on hybrid systems based on CB-CNT and CB-GRM [1]. Research objective is to identify common features and behaviour of nano (CNT, GRM) and nanostructured (CB) sp2 carbon allotropes. In this work, initial modulus was determined by means of dynamic-mechanical shear measurements of composites based on either poly(1,4-cis-isoprene) or poly(styrene-co-butadiene) as the rubber and either CB or CNT or GRM or hybrid systems as the reinforcing fillers. Filler-polymer interfacial area (i.a.), calculated as the product of filler surface area, density and volume fraction, was used to establish a common correlation with the composite initial modulus. A sort of master curve was derived, able to fit all the points up to interfacial area of about 27 μm-1, corresponding to remarkable filler content. Much better efficiency was shown by carbon fillers, when composites were prepared through latex blending. To allow easy dispersion in rubber latex, sp2 carbon allotropes were functionalized with a serinol derivative: 2-(2,5-dimethyl- 1H-pyrrol-1-yl)-1,3-propanediol (serinol pyrrole, SP) [2, 3], shown in Figure 1

Is renalase a novel player in catecholaminergic signaling? The mystery of the catalytic activity of an intriguing new flavoenzyme

Renalase is a flavoprotein recently discovered in humans, preferentially expressed in the proximal tubules of the kidney and secreted in blood and urine. It is highly conserved in vertebrates, with homologs identified in eukaryotic and prokaryotic organisms. Several genetic, epidemiological, clinical and experimental studies show that renalase plays a role in the modulation of the functions of the cardiovascular system, being particularly active in decreasing the catecholaminergic tone, in lowering blood pressure and in exerting a protective action against myocardial ischemic damage. Deficient renalase synthesis might be the cause of the high occurrence of hypertension and adverse cardiac events in kidney disease patients. Very recently, recombinant human renalase has been structurally and functionally characterized in vitro. Results show that it belongs to the p-hydroxybenzoate hydroxylase structural family of flavoenzymes, contains non-covalently bound FAD with redox features suggestive of a dehydrogenase activity, and is not a catecholamine-degrading enzyme, either through oxidase or NAD(P)H-dependent monooxygenase reactions. The biochemical data now available will hopefully provide the basis for a systematic and rational quest toward the identification of the reaction catalyzed by renalase and of the molecular mechanism of its physiological action, which in turn are expected to favor the development of novel therapeutic tools for the treatment of kidney and cardiovascular diseases

Synthesis and biological evaluation of new natural phenolic (2E,4E,6E)-Octa-2,4,6-trienoic esters

In the present study the esterification of the OH groups of resveratrol, caffeic acid, ferulic acid, and -sitosterol with an antioxidant polyconjugated fatty acid, (2E,4E,6E)-octa-2,4,6-trienoic acid, was achieved. As the selective esterification of OH groups of natural compounds can affect their biological activity, a selective esterification of resveratrol and caffeic acid was performed by an enzymatic approach. The new resulting compounds were characterized spectroscopically (FT-IR, NMR mono, and bidimensional techniques); when necessary the experimental data were integrated by quantum chemical calculations. The antioxidant, anti-inflammatory and proliferative activity was evaluated. The good results encourage the use of these molecules as antioxidant and/or anti-inflammatory agents in dermocosmetic application

Reversible Stress-Driven and Stress-Free Two-Way Shape Memory Effect in a Sol-Gel Crosslinked Polycaprolactone

The two-way shape memory effect is the ability of a material to change its shape between two configurations upon application and removal of a stimulus, and, among shape memory polymers, it is featured only by few systems, such as semicrystalline networks. When studied under tensile conditions, it consists of elongation-contraction cycles along cooling and heating across the crystallization and melting region, typically under the application of a constant load. However, recent studies on crosslinked semicrystalline co-polymers demonstrate that also a completely stress-free, or self-sustained, two-way effect may be achieved through specific thermomechanical cycles. This effect is currently regarded with interest for the development of intrinsically reversible sensors and actuators, and it may also be displayed by simpler materials, as homopolymer-based semicrystalline networks. Only seldom articles investigate this possibility, therefore in this work the two-way shape memory behavior is studied on a poly(e-caprolactone) system, crosslinked by means of a sol-gel approach. The effect is studied both under stress-driven and stress-free condition, by applying properly set-up thermo-mechanical histories. The results allow to describe the effect as a function of temperature, to reveal the dependence on specific testing parameters and to compare the extent of the reversible strain variation under these two conditions

Curcumin and Novel Synthetic Analogs in Cell-Based Studies of Alzheimer's Disease

Alzheimer's disease (AD) is a chronic neurodegenerative disorder that is associated with the most common type of dementia and is characterized by the presence of deposits of the protein fragment amyloid beta (A\u3b2) in the brain. The natural product mixture of curcuminoids that improves certain defects in innate immune cells of AD patients may selectively enhance A\u3b2 phagocytosis by alteration of gene transcription. In this work, we evaluated the protective effects of curcuminoids in cells from AD patients by investigating the effect on NF-\u3baB and BACE1 signaling pathways. These results were compared to the gene expression profile of the clearance of A\u3b2. The minor curcumin constituent, bisdemethoxycurcumin (BDC) showed the most potent protective action to decrease levels of NF-\u3baB and BACE1, decrease the inflammatory cascade and diminish A\u3b2 aggregates in cells from AD patients. Moreover, mannosyl-glycoprotein 4-beta-N-acetylglucosaminyltransferase (MGAT3) and vitamin D receptor (VDR) gene mRNAs were up-regulated in peripheral blood mononuclear cells from AD patients treated with BDC. BDC treatment impacts both gene expression including Mannosyl (Beta-1,4-)-Glycoprotein Beta-1,4-N-Acetylglucosaminyltransferase, Vitamin D and Toll like receptor mRNA and A\u3b2 phagocytosis. The observation of down-regulation of BACE1 and NF-\u3baB following administration of BDC to cells from AD patients as a model system may have utility in the treatment of asymptomatic AD patients