How to build an adapted and bioactive cell microenvironment? A chemical interaction study of the structure of Ca-alginate matrices and their repercussion on confined cells (original) (raw)
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Biomacromolecules, 2019
The synthesis and detailed physicochemical behavior and structural characterization of these ALG gels are subjects of our current investigation. ASSOCIATED CONTENT Supporting Information. Experimental details for preparation of alginate beads; composition of the alginate beads; morphological characterization; swelling capacity tests; dissolution tests; ex vivo cytotoxicity tests; solid-state NMR spectroscopy; and scanning electron microscopy.
Design of Porous Alginate Hydrogels by Sacrificial CaCO3Templates: Pore Formation Mechanism
Advanced Materials Interfaces, 2015
signifi cantly precise control over the scaffold architecture. Well-defi ned internal structure (porosity) determines both cellular infi ltration into the scaffold and its material properties. Pore size and distribution ensuring diffusion of nutrients into the scaffold and removal of metabolic products is of high importance. [ 4,11 ] Ionically crosslinked polymer gels such as alginate hydrogels have been extensively developed as scaffolds for tissue engineering. [ 12-15 ] The adjustable kinetics of the alginate gel degradation at neutral pH [ 1,16,17 ] gives an option to use the gels for multiple applications as wound dressings, anti-adhesive, and repair materials. [ 14,18-21 ] Characteristics of alginate gels (hydration, softness, porosity, swelling in water, etc.) can be adjusted using a certain fabrication approach and by variation of interactions between charged polyanionic groups and crosslinking counterions; [ 13,17,22-25 ] these interactions are known to be strongly affected by ionic strength, molecule length and structure, solvent pH, salt concentration, and temperature conditions. [ 26-31 ] This allows the fabrication of alginate scaffolds possessing desired properties corresponding to a certain tissue, for instance cartilage, [ 12 ] or dura mater. [ 21 ] Porous alginate gels can provide space and mechanical support to seed biological cells for tissue formation, [ 1,13,32 ] also allowing a controlled release of gel-laden drugs (peptides and proteins) trapped within the alginate network. [ 14,24,25,33,34 ] To achieve loading of both biological cells and bioactive molecules, the internal structure of hydrogels has to be controlled on the scale of nano-and micrometers. Adjustment of the gel geometry has been demonstrated on substrate surfaces using different micropatterning techniques including a light-addressable electrolytic system, [ 14 ] electrodeposition, [ 15 ] electrochemical patterning, [ 35 ] or the benchtop method using Nylon mesh. [ 11 ] The internal structure of alginate gels has been patterned with regular tube-like pores, [ 16,36 ] interconnected ordered honeycomb pores, [ 12 ] and sponge-like isotropic pores. [ 37-39 ] However, most of the approaches for alginate gel fabrication lack a precise control over the microstructure and require special equipment. Encapsulation of molecules of interest with controlled spatial distribution is rather complicated or even impossible. There is a need to develop a simple approach for design of a scaffold with welldefi ned internal structure providing both a space to culture cells and cavities to host/release encapsulated (bio)active molecules. Fabrication of porous alginate hydrogels with a well-controlled architecture useful for tissue engineering is still a challenge. Here, CaCO 3-based templating is utilized to design stable alginate gels with controlled pore dimensions in the range of 5-50 µm. The mechanism of pore formation is studied considering two factors affecting the pore size: i) osmotic pressure generated during the dissolution of sacrifi cial CaCO 3 templates and ii) alginate gel network density. Osmotic pressure can achieve an upper limit of 100 MPa but does not affect the gel porosity. Additional osmotic pressure (range of kPa) induced by dextrans pre-encapsulated into CaCO 3 vaterite is also insuffi cient for pore enlargement. Pore stability depends merely on the gel network density and on the number of crosslinking calcium ions provided locally per unit time; pores are collapsed when template dissolution is too slow or if there is insuffi cient alginate concentration (below 2%). Young's modulus indicates the soft nature of the prepared hydrogels (tens of kPa) applicable as soft porous scaffolds with a tuned internal structure.
Structural Characterization of Calcium Alginate Matrices by Means of Mechanical and Release Tests
Molecules, 2009
In this paper we have concentrated on the characterization of calcium alginate hydrogels loaded with a model drug (myoglobin) by means of a mechanical approach; in addition, release tests of myoglobin from alginate hydrogels were performed. At a fixed temperature, relaxation tests (mechanical study) were carried out on matrices constituted by different polymer concentrations. The interpretation of the relaxation behavior of the different matrices was conducted using the generalized Maxwell model; as a result of this investigation it was possible to conclude that for polymer concentrations greater than 0.5 g/ 100 mL the matrices behaved as solid materials. In addition, it was observed that the mechanical properties of the matrices increased with polymer concentration. With regard to the release tests, the diffusion coefficient of myoglobin in the matrix in relation to polymer concentrations was determined. The mechanical and release data where then analyzed by Flory's theory and by a modified free-volume theory, respectively, to estimate the network mesh size ξ. The comparison between the mesh sizes obtained by the two approaches showed a satisfactory agreement for polymer concentrations greater than
Investigations of cell immobilization in alginate: rheological and electrostatic extrusion studies
Journal of Chemical Technology & Biotechnology, 2006
In this study, the process of electrostatic extrusion as a method for cell immobilization was investigated. We have assessed the effects of concentrations of yeast cells (as a model cell type) and Na alginate on the size of the resulting microbeads and attempted to rationalize the obtained findings by rheological characterization of the cell-alginate suspensions. Under the investigated conditions, microbeads, 50-600 µm in diameter, were produced and the increase in both alginate and cell concentrations resulted in larger microbeads with their sizes having higher standard deviations. Rheological characterization revealed non-Newtonian, pseudoplastic behavior of cell-alginate suspensions with higher viscosities at higher alginate concentrations. However, the presence of cells even at high concentrations (5 × 10 8 and 1 × 10 9 cells mL −1 ) did not significantly affect the rheological properties of the Na alginate solution. Finally, we have investigated the kinetics of alginate gelation with respect to the quantity of Ca 2+ ions and the presence of cells. The molar ratio of α-L-guluronic acid units to Ca 2+ ions of 4:1 provided complete crosslinking. The presence of cells decreased the rate of network formation as well as the strength of the obtained Ca alginate hydrogel.
Alginate: Properties and biomedical applications
Alginate is a biomaterial that has found numerous applications in biomedical science and engineering due to its favorable properties, including biocompatibility and ease of gelation. Alginate hydrogels have been particularly attractive in wound healing, drug delivery, and tissue engineering applications to date, as these gels retain structural similarity to the extracellular matrices in tissues and can be manipulated to play several critical roles. This review will provide a comprehensive overview of general properties of alginate and its hydrogels, their biomedical applications, and suggest new perspectives for future studies with these polymers.
Biomaterials based on a natural polysaccharide: alginate
TIP, 2014
In this short review, our objective was to describe few new applications of a natural polysaccharide extracted from algae, the alginates. Firstly, the chemical composition is recalled and the main techniques used for characterization are cited. The role of guluronic acid blocks (GG blocks) is particularly important for gel mechanical properties in presence of calcium counterions. Then, the main applications in food and biomedicine are briefly mentioned followed by tentative applications in packaging, paper, textil and wound dressing which are described. Especially, fine fibers are produced now industrially under mixed sodium/calcium ionic form.
The Usages and Potential Uses of Alginate for Healthcare Applications
Frontiers in Molecular Biosciences, 2021
Due to their unique properties, alginate-based biomaterials have been extensively used to treat different diseases, and in the regeneration of diverse organs. A lot of research has been done by the different scientific community to develop biofilms for fulfilling the need for sustainable human health. The aim of this review is to hit upon a hydrogel enhancing the scope of utilization in biomedical applications. The presence of active sites in alginate hydrogels can be manipulated for managing various non-communicable diseases by encapsulating, with the bioactive component as a potential site for chemicals in developing drugs, or for delivering macromolecule nutrients. Gels are accepted for cell implantation in tissue regeneration, as they can transfer cells to the intended site. Thus, this review will accelerate advanced research avenues in tissue engineering and the potential of alginate biofilms in the healthcare sector.
Biomaterials, 2001
Alginate gels have been used in both drug delivery and cell encapsulation applications in the bead form usually produced by dripping alginate solution into a CaCl bath. The major disadvantages to these systems are that the gelation rate is hard to control; the resulting structure is not uniform; and mechanically strong and complex-shaped 3-D structures are di$cult to achieve. In this work controlled gelation rate was achieved with CaCO }GDL and CaSO }CaCO }GDL systems, and homogeneous alginate gels were formulated as sca!olds with de"ned dimensions for tissue engineering applications. Gelation rate increased with increasing total calcium content, increasing proportion of CaSO , increasing temperature and decreasing alginate concentration. Mechanical properties of the alginate gels were controlled by the compositional variables. Slower gelation systems generate more uniform and mechanically stronger gels than faster gelation systems. The compressive modulus and strength increased with alginate concentration, total calcium content, molecular weight and guluronic acid (G) content of the alginate. MC3T3-E1 osteoblastic cells were uniformly incorporated in the alginate gels and cultured in vitro. These results demonstrated how alginate gel and gel/cell systems could be formulated with controlled structure, gelation rate, and mechanical properties for tissue engineering and other biomedical applications.
Alginate-Based Biomaterials in Tissue Engineering and Regenerative Medicine
Marine Drugs
Today, with the salient advancements of modern and smart technologies related to tissue engineering and regenerative medicine (TE-RM), the use of sustainable and biodegradable materials with biocompatibility and cost-effective advantages have been investigated more than before. Alginate as a naturally occurring anionic polymer can be obtained from brown seaweed to develop a wide variety of composites for TE, drug delivery, wound healing, and cancer therapy. This sustainable and renewable biomaterial displays several fascinating properties such as high biocompatibility, low toxicity, cost-effectiveness, and mild gelation by inserting divalent cations (e.g., Ca2+). In this context, challenges still exist in relation to the low solubility and high viscosity of high-molecular weight alginate, high density of intra- and inter-molecular hydrogen bonding, polyelectrolyte nature of the aqueous solution, and a lack of suitable organic solvents. Herein, TE-RM applications of alginate-based ma...
Characterisation of Encapsulated Cells in Calcium Alginate Microcapsules
—Polysaccharides including agarose, chitosan, alginate and collagen are group of natural polymers applied for microencapsulation of cells. This study focused on the characterisation of calcium alginate microcapsules and encapsulated human keratinocytes cell lines. The synthesised calcium alginate were characterised using Fourier Transform Infrared Spectroscopy (FTIR) in wavelength ranging from 600-4000 cm-1 and Field Emission Scanning Electron Microscopy (FESEM). Cells restructuring in the calcium alginate microcapsules influenced the functional groups and chemistry contents of the cells.