مقالات پذیرفته شده در پنجمین کنگره بین المللی زیست پزشکی
Rheology evaluation of Gelatin/ Alginate/ Laponite nanocomposite hydrogel for Tissue Engineering applications
Rheology evaluation of Gelatin/ Alginate/ Laponite nanocomposite hydrogel for Tissue Engineering applications
Faezeh Shahedi Aliabad,1Elnaz Tamjid,2,*
1. Department of Nanobiotechnology, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran 2. Department of Nanobiotechnology, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
Introduction: Gelatin is a natural polymer synthesizing from partial denaturation of Collagen which is biocompatible, biodegradable, and inexpensive with cell attachment motifs. In contrast, Sodium alginate is a natural polymer extracted from brown algae and doesn’t have cell attachment domains. Despite the fast degradation of Gelatin in physiological environments, mammalian cells are not able to break sodium alginate down. Therefore, incorporating a proper ratio of these polymers could be desirable for tissue regeneration but they don’t have enough mechanical and rheological properties. Furthermore, laponite platelets are synthetic disk-like nanomaterials with 25 nm diameter and 0.95 nm thickness which Adding them as nanofillers improve mechanical and rheological properties of composites. Tissue engineering aims to construct biocompatible scaffolds as mechanical and chemical support for cell growth, proliferation, and adhesion. Bioprinting is an attractive manufacturing method to construct scaffolds and is promising for tissue regeneration. The studied hydrogels in this research were all injectable with good rheological characteristics thus they are promising for use as bioink in 3D bioprinting. In this study, laponite, gelatin, and alginate were combined and viscosity and viscoelastic behavior of unset and set gels were performed respectively.
Methods: Three hydrogels containing 4% Gelatin, 2% Sodium alginate, and (0-2%) w/v Laponite were produced through stirring at 55°C. CaCl2 solution which crosslinks alginate chains is used as the crosslinker of the hydrogels. Unset hydrogels (before crosslinking with CaCl2) and crosslinked samples were used for viscosity and viscoelastic analysis respectively. Hydrogel solutions were cast in 24-well plate and crosslinked with immerging in 100 mM CaCl2 thus disk shape samples with 14 mm diameter and 4 mm height were created. All samples were kept at 4°C for 10 days then the rheological characterizations were performed using an Anton Paar MCR-502 Modular Compact Rheometer. Analysis was conducted using a parallel plate geometry with 25 mm diameter and 1 mm gap size at room temperature (25°C). Viscosity measurements were performed in the shear rate range of 0.01 to 1000 1/s. In addition, amplitude sweep tests were carried out to estimate viscoelasticity and mechanical characterization of crosslinked hydrogels. First, strain sweep tests were conducted at a constant frequency of 10 rad 1/s with a shear strain range of 0.01-100%. Based on the results, linear viscoelasticity (LVE) range was defined for gels so frequency sweep test performed in strain rate of 0.1% with frequency from 0.1 to 628 rad/s.
Results: Based on the results, all samples were injectable (shear thinning) which means the viscosity of the samples decreased through increasing shear rate progressively. physical cross-linking influences on viscosity and mechanical profile. incorporation of 1% (w/v) Laponite into the network increased viscosity, storage (G') and loss modulus (G") of the nanocomposites Because negative surfaces and positive edges of laponite platelets could interact with gelatin and alginate respectively. In other words, adding laponite (1% w/v) enhanced the viscosity of the hydrogel from 255 to 320 Pa.s but nanocomposites with 2% laponite due to aggregation of platelets represented less viscosity (222 Pa.s). G' was greater than G" for all samples which shows the solid behavior of each hydrogel. Further, G', G" and consequently mechanical stability of nanocomposites improved by the addition of laponite platelets into the structure.
Conclusion: In conclusion, in this study, a nanocomposite based on gelatin, alginate, and laponite was fabricated and rheological tests were conducted. Incorporating Laponite into the network develops electrostatic interactions with polymers so the viscosity profile improves. A strong shear-thinning profile and solid-like behavior guarantee printability of the hydrogels and shape-retaining after printing. addition of 1% Laponite improved shear-thinning and solid-like behavior of the hydrogel strongly.