3D-Bioprinting of Polylactic Acid (PLA) Nanofiber–Alginate Hydrogel Bioink Containing Human Adipose-Derived Stem Cells

Abstract

Bioinks play a central role in 3D-bioprinting by providing the supporting environment within which encapsulated cells can endure the stresses encountered during the digitally driven fabrication process and continue to mature, proliferate, and eventually form extracellular matrix (ECM). In order to be most effective, it is important that bioprinted constructs recapitulate the native tissue milieu as closely as possible. As such, musculoskeletal soft tissue constructs can benefit from bioinks that mimic their nanofibrous matrix constitution, which is also critical to their function. This study focuses on the development and proof-of-concept assessment of a fibrous bioink composed of alginate hydrogel, polylactic acid nanofibers, and human adipose-derived stem cells (hASC) for bioprinting such tissue constructs. First, hASC proliferation and viability were assessed in 3D-bioplotted strands over 16 days in vitro. Then, a human medial knee meniscus digitally modeled using magnetic resonance images was bioprinted and evaluated over 8 weeks in vitro. Results show that the nanofiber-reinforced bioink allowed higher levels of cell proliferation within bioprinted strands, with a peak at day 7, while still maintaining a vast majority of viable cells at day 16. The cell metabolic activity on day 7 was 28.5% higher in this bioink compared to the bioink without nanofibers. Histology of the bioprinted meniscus at both 4 and 8 weeks showed 54% and 147% higher cell density, respectively, in external versus internal regions of the construct. The presence of collagen and proteoglycans was also noted in areas surrounding the hASC, indicating ECM secretion and chondrogenic differentiation.

3D printing of hydrogel composite systems: Recent advances in technology for tissue engineering

“…Improved mechanical properties and biological properties Cartilage [91] Fiber 3D plotting Acrylamide Cellulose short fibril Anisotropic swelling behaviors 4D printing [92] 3D plotting Alginate PLA continuous nanofiber Improved mechanical properties and biological properties Cartilage [93] Casting + 3D plotting PEGDGE, Acrylamide PU continuous microfiber Improved mechanical properties General [94] 3D plotting Alginate, Acrylamide Emax (UV-curable epoxy)…”

“…Fiber reinforcements can also improve mechanical properties of hydrogel matrix in which the fiber contents and its distribution inside its matrix determine mechanical properties such as stiffness and strength of composites [92][93][94][95] . In the case of common 3D printing systems, short fiber reinforcements are the most commonly used due to its easy processing procedure at low cost.…”

“…However, in spite of its outstanding performance, the most challenging issue for applying this composite system to the 3D printing process are practical ways to achieve an uniform distribution and intended alignment of continuous fibers within the hydrogel matrix. Narayanan et al tried to fabricate alginate-nanofiber bioink for 3D-bioprinting which could provide protection for encapsulated cells during the digitally driven fabrication process [93] . To prepare the composite hydrogel, pre-fabricated portions of PLA nanofiber was mixed with alginate (ratio 1:5, w/w), and agitated in a vortex mixer, and finally sonicated for 2 hours.…”

Nanofiber‐Based Hydrogels: Controllable Synthesis and Multifunctional Applications

“…Meanwhile, various designed 3D print structures are easily obtained through combining 3D printing technique with imaging or graphics techniques . Recently, 3D‐printed NFHGs with designed tissue constructs were successfully prepared by taking mixtures of alginate hydrogel, PLA nanofibers, and stem cells as fibrous bioink ( Figure ) . Conventionally, printable ink with appropriate viscosity and shear‐thinning properties is the most vital part of the 3D printing technique, because of the significant influences on the formability of printed 3D materials.…”

Polymeric 3D printed structures for soft‐tissue engineering

“…In attempt to combat the cellular viability dilemma, Narayanan et al . recently demonstrated that by blending a PLA nanofibrous matrix with alginate hydrogel, cellular viability could further be enhanced through ECM mimicry . Human adipose‐derived stem cells were cultured in vitro over an 8‐week period after bioprinting with and without the nanofibrous matrix blend.…”