The 3D-McMap Guidelines: Three-Dimensional Multicomposite Microsphere Adaptive Printing

Abstract

Microspheres, synthesized from diverse natural or synthetic polymers, are readily utilized in biomedical tissue engineering to improve the healing of various tissues. Their ability to encapsulate growth factors, therapeutics, and natural biomolecules, which can aid tissue regeneration, makes microspheres invaluable for future clinical therapies. While microsphere-supplemented scaffolds have been investigated, a pure microsphere scaffold with an optimized architecture has been challenging to create via 3D printing methods due to issues that prevent consistent deposition of microsphere-based materials and their ability to maintain the shape of the 3D-printed structure. Utilizing the extrusion printing process, we established a methodology that not only allows the creation of large microsphere scaffolds but also multicomposite matrices into which cells, growth factors, and therapeutics encapsulated in microspheres can be directly deposited during the printing process. Our 3D-McMap method provides some critical guidelines for issues with scaffold shape fidelity during and after printing. Carefully timed breaks, minuscule drying steps, and adjustments to extrusion parameters generated an evenly layered large microsphere scaffold that retained its internal architecture. Such scaffolds are superior to other microsphere-containing scaffolds, as they can release biomolecules in a highly controlled spatiotemporal manner. This capability permits us to study cell responses to the delivered signals to develop scaffolds that precisely modulate new tissue formation.

Keywords: 3D bioprinting; Bioplotter; PLA; PLGA; microspheres; multicomposite scaffold.

Figure 1

(A) Microsphere manufacturing unit with custom carrier platform; (B) Custom setup to permit for bio-ink extrusion from a 1 mL Luer lock syringe in a 3D Bioplotter using either a (C1) 18G or (C2) 16G precision syringe tip; (D) Custom dichloromethane vapor sintering chamber.

Figure 2

(A) PLA microspheres of 200 µm +/−10 µm diameter after sifting. (B) PLGA microspheres of 200 µm +/−10 µm diameter after sifting without sucrose. (C) Sucrose interference of the autofluoresces capability of PLGA microspheres (dotted circles mark the microspheres). (D) PLGA microspheres of 200 µm +/−10 µm diameter sifted with sucrose and after sucrose removal through washing.

Figure 3

(A1–A3) Conventional 3D-printing techniques utilizing Ø 200 µm +/−10 µm PLA microspheres versus (B,C1–C3) the 3D-McMap method.

Figure 4

µCT scan (top view) of a PLA microsphere-based scaffold fabricated via the 3D-McMap method.

Figure 5

Multicomposite hemisphere/condyle scaffold comprising Ø 200 µm +/−10 µm PLA microspheres, with an internal strutted architecture utilizing the 3D-McMap method/guide.

Figure 6

SEM and compression assay structural results of 3D-printed PLGA scaffolds (A,D) unsintered (control), (B,E) sintered for 165 s, and (C,F) oversintered after 240 s.

Figure 7

(A) Mechanical stability and (B) compressive strength of 3D-printed PLGA microsphere scaffolds, unsintered (control), sintered for 165 s, and oversintered for 240 s.