Abstract
Many studies show how biomaterial properties like stiffness, mechanical stimulation and surface topography can influence cellular functions and direct stem cell differentiation. In this work, two different natural materials, gelatin (Gel) and cellulose nanofibrils (CNFs), were combined to design suitable 3D porous biocomposites for soft-tissue engineering. Gel was selected for its well-assessed high biomimicry that it shares with collagen, from which it derives, while the CNFs were chosen as structural reinforcement because of their exceptional mechanical properties and biocompatibility. Three different compositions of Gel and CNFs, i.e., with weight ratios of 75:25, 50:50 and 25:75, were studied. The biocomposites were morphologically characterized and their total- and macro- porosity assessed, proving their suitability for cell colonization. In general, the pores were larger and more isotropic in the biocomposites compared to the pure materials. The influence of freeze-casting and dehydrothermal treatment (DHT) on mechanical properties, the absorption ability and the shape retention were evaluated. Higher content of CNFs gave higher swelling, and this was attributed to the pore structure. Cross-linking between CNFs and Gel using DHT was confirmed. The Young’s modulus increased significantly by adding the CNFs to Gel with a linear relationship with respect to the CNF amounts. Finally, the biocomposites were characterized in vitro by testing cell colonization and growth through a quantitative cell viability analysis performed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Additionally, the cell viability analysis was performed by the means of a Live/Dead test with Human mesenchymal stem cells (hMSCs). All the biocomposites had higher cytocompatibility compared to the pure materials, Gel and CNFs.
Highlights
The difficulties and limitations of conventional tissue engineering (TE) have recently given rise to a new concept known as “in situ TE”, where the own regenerative capability of the body is exploited and addressed to enable the regeneration and healing of the target tissue [1,2]
Biopolymer blends with a final concentration of 1.1 wt% were obtained by mixing an aqueous solution of Gel (1.1 wt%) and an aqueous suspension of cellulose nanofibrils (CNFs) (1.09 ± 0.01 wt%) in order to obtain significances between the samples were calculated using the two-way analysis of variance (ANOVA) test
Morphological Characterization Biocomposite morphology was evaluated after freeze-drying by environmental scanning microscopPyor(eESmEoMrp,hQoluoagnytaan2d0d0iFstEriGbu, tFiEonI Cploamy pa acnruyc,iHalirlloslbeosrinoc, eOtRhe, yUaSfAfe)c.t:Tih) ethseacmelplulelasrwaderheespiorenp, ared proliferation and growth; ii) the permeation of nutrients and oxygen for the cells from the surface by fixtoinwgartdhsemtheoncotoreaoluf mthiensucmaffostldubasndustihnegecliamrbinoantiotanpoef, CanOd2 athndenoAthuercmoaettaebdoulitseisngfrothme tchoeactionrge unit PolartoonwSarpdusttthere Csuorafatecer;Ea5n1d0i0ii)(PthoelamroenchEanqiuciapl mbeehnatv,iWoraotffothrde,wHheorletfsocradffsohlidr.eE, SUEKM).images
Summary
The difficulties and limitations of conventional tissue engineering (TE) have recently given rise to a new concept known as “in situ TE”, where the own regenerative capability of the body is exploited and addressed to enable the regeneration and healing of the target tissue [1,2]. The new far reaching goal of the most innovative regenerative approaches for tissue engineering is to restore the original functionality of the damaged or injured tissues and organs, in order to obtain a complete recovery [3] In this perspective, natural polymers are attracting more and more interest as scaffolds, due to their biocompatibility and when degraded, resorbable nature. The scaffolds should be able to support cell adhesion, migration and growth, and to influence cellular functions and direct “in situ” stem cells differentiation This can be influenced by the scaffold’s chemical composition, stiffness, surface topography, geometry, and permeability. It is a physical treatment that removes water from polymer molecules thanks to the increased temperature (160 ◦C) and vacuum conditions This results in the formation of intermolecular cross-links through condensation reactions, either by esterification or by amide formation [8]. An effective strategy is outlined to develop biocompatible and bioresorbable 3D porous scaffolds as a promising option for in situ soft-tissue engineering with tunable properties
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