Three-Dimensional-Printed Sodium Alginate and k-Carrageenan-Based Scaffolds with Potential Biomedical Applications

Abstract

This work reports the development of a marine-derived polysaccharide formulation based on k-Carrageenan and sodium alginate in order to produce a novel scaffold for engineering applications. The viscoelastic properties of the bicomponent inks were assessed via rheological tests prior to 3D printing. Compositions with different weight ratios between the two polymers, without any crosslinker, were subjected to 3D printing for the first time, to the best of our knowledge, and the fabrication parameters were optimized to ensure a controlled architecture. Crosslinking of the 3D-printed scaffolds was performed in the presence of a chloride mixture (CaCl₂:KCl = 1:1; v/v) of different concentrations. The efficiency of the crosslinking protocol was evaluated in terms of swelling behavior and mechanical properties. The swelling behavior indicated a decrease in the swelling degree when the concentration of the crosslinking agent was increased. These results are consistent with the nanoindentation measurements and the results of the macro-scale tests. Moreover, morphology analysis was also used to determine the pore size of the samples upon freeze-drying and the uniformity and micro-architectural characteristics of the scaffolds. Overall, the registered results indicated that the bicomponent ink, Alg/kCG = 1:1 may exhibit potential for tissue-engineering applications.

Keywords: 3D printing; interpenetrated networks hydrogels scaffolds; k-Carrageenan; sodium alginate.

Figure 1

Schematic steps representation of the printing process, including synthesis of the bicomponent material and the crosslinking of the manufactured 3D-printed scaffold Alg/kCG = 1:1.

Figure 2

The viscosity dependence on the shear rate at 25 °C.

Figure 3

The dependence of storage modulus G′ and loss modulus G″ on frequency for the studied solutions.

Figure 4

The recovery behaviors of the bicomponent formulations subjected to alteration of shear rates (0.1 s⁻¹ and 100 s⁻¹) at 25 °C.

Figure 5

Printed structures using Alg/kCG = 3:1. All objects have 5 layers with 4 mm line spacing and were printed at 10 mm/s velocity using a 27 G needle at different extruding pressures like 40 kPa (A); 100 kPa (B) and 50 kPa (C) and a 23 G needle at a 25 kPa pressure (D).

Figure 6

Printed structures using Alg/kCG = 1:3. All trails were performed using a G 27 nozzle. The structures (A,B) were extruded at 150 kPa with 10 mm/s for (A) and 8 mm/s for (B,C). The pressure used for manufacturing C construct was 180 kPa.

Figure 7

Three-dimensional layer-by-layer depositions of Alg/kCG = 1:1 ink. Macroscopic imagine (A) represent a 35-layer scaffold; imagine (B) displays a 60 layers construct; imagine (C) shows a 20-layer scaffold prior crosslinking while (D) shows a 20-layer scaffold after crosslinking. A 15-layer grid construct is presented in (E). The imagines noted with (F,G) depict the side view of a 40-layers scaffold. The imagine (H), illustrates the top view of a 35-layer scaffold.

Figure 8

Graphical representation of storage modulus and loss modulus as obtained from indentation tests.

Figure 9

(A) Maximum swelling degree of the crosslinked scaffolds in PBS, pH = 7.4; (B) Swelling kinetics of the 3D-printed constructs; (C) Images of 3D-printed specimens during swelling trials showing the 3D construct before (left) and after (right) the sinking in PBS, pH = 7.4 and the side view of the scaffolds.

Figure 10

Degradation analyses of the bi-component Alg/kCG = 1:1 3D-printed scaffolds.

Figure 11

Micro-CT images depicting the surface of whole (A1) 0.3 M, (B1) 0.5 M, (C1) 0.8 M and (D1) 1.2 M consisting of original tomograms (grayscale half) overlapped with CTAn-processed color-coded dataset (bottom half). Secondary and ternary subsets depict the same top-view section for each printed object providing the image of pore/wall interface (A2–D2) and the solidity of inner solid structures (A3–D3). The “4” subsections depict the original tomogram of the objects with the focus on the outer aspect of the prints, as follows: 4.1—lateral view, 4.2—cross-section to illustrate the aspect of the external walls of the grid, 4.3—top view of the central areas of the samples and 4.4—overall surface aspect of the printed objects. (E) division covers the plot of the quantitative analysis of pore size within the scanned samples).