Alginate dependent changes of physical properties in 3D bioprinted cell-laden porous scaffolds affect cell viability and cell morphology

Abstract

Three-dimensional (3D) cell-laden scaffolds are becoming more prevalent in bone tissue repair and regeneration. However, the influence of physical scaffold properties on cell behavior is still unclear. In this study, we fabricated four different alginate concentration (0.8, 1.3, 1.8 and 2.3%alg) composite cell-laden porous scaffolds using a 3D bioprinting technique. The aim was to investigate the changes of physical properties affected by the alginate concentration and the influences on cell behavior. The study showed that the different alginate concentration scaffolds had uniform macropores (500–600 μm) with compressive moduli ranging from 1.5 kPa (0.8%alg) to 14.2 kPa (2.3%alg). Long-term structural integrity of the printed scaffolds was achieved when cultured in cell culture media, but not when cultured in phosphate buffered saline (PBS). Scaffold structure, swelling behavior, and compressive moduli decreased with culturing time and higher alginate concentration lead to more stable physical scaffold properties. Meanwhile, human mesenchymal stem cell (hMSCs) laden non-printed and bioprinted composite scaffolds were fabricated. Bioprinting did not affect cell viability, but alginate concentration had a significant influence on cell viability and cell morphology. Lower alginate concentration scaffolds (0.8%alg) showed higher cell viability (84% ± 0.7% versus 68% ± 1.3%) compared to higher alginate concentration scaffolds (2.3%alg) at day 14. Live cell image in the 0.8%alg scaffolds demonstrated the formation of a 3D interconnected cellular network, while cells in the 1.8 and 2.3%alg scaffolds formed spheroids. In conclusion, this study broadens the design space for alginate-based bioinks for 3D bioprinting. Higher alginate concentration preserved better scaffold fidelity and mechanical properties. Better cell viability and cell spreading morphology was achieved in lower alginate concentration scaffolds, which is relevant for potential applications in bone tissue engineering.

3D Bioprinting of Graphene Oxide-Incorporated Cell-laden Bone Mimicking Scaffolds for Promoting Scaffold Fidelity, Osteogenic Differentiation and Mineralization

“…The shrinkage behavior of 0GO was similar to that observed in our previously published study when the scaffold was cultured in cell culture media [7] . James et al [24] and Ma et al [22] reported that ionically crosslinked alginate gel will lose its stability due to the loss of crosslinking calcium ions when in the presence of calcium chelators (e.g., phosphates), monovalent ions (e.g., K + , Na + , etc.…”

“…Four alginate/gelatin/GO composite ink solutions containing different GO concentrations, 0 mg/ml, 0.5 mg/ml, 1 mg/ml and 2 mg/ml GO, were named 0GO, 0.5GO, 1GO and 2GO, respectively. Alginate (70.4 mg, 0.8% w/v) and gelatin (360 mg, 4.1% w/v) were added to a homogeneous glycerol/ phosphate-buffered saline (PBS) (9.1% v/v) solution to prepare the 0GO group as a control, as described previously [7] . The commercial GO product is a 5 mg/ml GO dispersion in water solution.…”

“…Alginate polymer chains are crosslinked with Ca 2+ after bioprinting to provide long-term mechanical strength. Our previous studies have shown that low-density alginate/gelatin (0.8% alg) blend bioinks can maintain high cell viability (> 85%) and induce the osteogenic differentiation of human mesenchymal stem cells (hMSC) [7] . Significantly more mineralized tissue was formed in low-density (0.8% alg) than high-density (1.8%) alginate/gelatin scaffolds (43.5 ± 7.1 mm 3 vs 22.6 ± 6.0 mm 3 ) after culturing in osteogenic media for 42 days.…”

“…However, low-density alginate/gelatin ink solutions often result in moderate printability, insufficient mechanical strength, and low scaffold fidelity because of the intrinsic swelling and/or shrinking properties of alginate and gelatin. The scaffold fidelity and mechanical properties could be improved with higher density bioinks, such as by increasing alginate concentration, while increased viscosity suppressed cell viability and cell morphology [7] . Thus, the ability to design low-density alginate/gelatin-based bioinks with improved mechanical properties, scaffold fidelity and cell functions remains a challenge in 3D bioprinting for engineering bone tissues [8] .…”

Multicomponent polysaccharide alginate-based bioinks

“…Müller and co-workers studied this using four different alginate concentrations (0.8%, 1.3%, 1.8% and 2.3% wt/vol) in combination with gelatin. 44 The resulting bioinks were used to 3D print MSCs scaffolds, which were cross-linked with a 2% CaCl 2 solution. The obtained constructs displayed similar porosities (500-600 mm pores), but different mechanical properties depending on the alginate concentration, with compressive moduli ranging from 1.5 kPa (0.8% wt/vol) to 14.2 kPa (2.3% wt/vol).…”