Microsphere-Based Seamless Scaffolds Containing Macroscopic Gradients of Encapsulated Factors for Tissue Engineering

Abstract

Spatial and temporal control of bioactive signals in three-dimensional (3D) tissue engineering scaffolds is greatly desired. Coupled together, these attributes may mimic and maintain complex signal patterns, such as those observed during axonal regeneration or neovascularization. Seamless polymer constructs may provide a route to achieve spatial control of signal distribution. In this study, a novel microparticle-based scaffold fabrication technique is introduced as a method to create 3D scaffolds with spatial control over model dyes using uniform poly(D,L-lactide-co-glycolide) microspheres. Uniform microspheres were produced using the Precision Particle Fabrication technique. Scaffolds were assembled by flowing microsphere suspensions into a cylindrical glass mold, and then microspheres were physically attached to form a continuous scaffold using ethanol treatment. An ethanol soak of 1 h was found to be optimum for improved mechanical characteristics. Morphological and physical characterization of the scaffolds revealed that microsphere matrices were porous (41.1 ± 2.1%) and well connected, and their compressive stiffness ranged from 142 to 306 kPa. Culturing chondrocytes on the scaffolds revealed the compatibility of these substrates with cell attachment and viability. In addition, bilayered, multilayered, and gradient scaffolds were fabricated, exhibiting excellent spatial control and resolution. Such novel scaffolds can serve as sustained delivery devices of heterogeneous signals in a continuous and seamless manner, and may be particularly useful in future interfacial tissue engineering investigations.

Endothelial cells guided by immobilized gradients of vascular endothelial growth factor on porous collagen scaffolds

“…Methods to generate growth factor gradients concurrently with the fabrication of porous scaffolds are available. For example, dye loaded Poly(D,L-lactide-co-glycolide) (PLG) microparticles were assembled into multilayered or gradient scaffolds by ethanol treatment, where the concentration of the released molecule can be spatially controlled within the scaffold [61].…”

Osteogenic Differentiation of Human Bone Marrow Stromal Cells in Hydroxyapatite-Loaded Microsphere-Based Scaffolds

“…The advantages of this approach relate to the ability to tightly control a gradient in physical or chemical properties across the length of the scaffold by using each single microsphere as a ''building block.'' The current study, for the first time, used a precision particle fabrication technology 28,[30][31][32] to make poly(d,l-lactic acid-co-glycolic acid) (PLGA) microspheres loaded with HAp nanoparticles. The microspheres were used to construct 3-D scaffolds with various HAp contents on which human bone marrow stromal cells (hBMSC) were osteogenically differentiated for 6 weeks.…”

Microsphere-Based Gradient Implants for Osteochondral Regeneration: a Long-Term Study in Sheep

“…Two different batches of monodisperse microspheres were prepared using the aforementioned emulsions of PLGA-CS-NaHCO 3 and PLGA-β-TCP according to our previously reported technology [12][13][14]. Briefly, uniform polymer droplets were created by introducing regular jet instabilities in the polymer stream through acoustic excitation via an ultrasonic transducer.…”

“…Microsphere-based gradient implants for osteochondral regeneration: a long-term study in sheep Research Article Fabrication of gradient scaffolds Gradient scaffolds were prepared using our previously reported technology [12][13][14][15]. Briefly, 50 mg of lyophilized chondrogenic microspheres and 100 mg of osteogenic microspheres were dispersed in DI water, and separately loaded into two syringes.…”

“…A gradient profile was used for engineering scaffolds in which chondrogenic microspheres comprised the top quarter (1.5 mm), followed by a (1.5 mm) linear transition from chondrogenic microspheres to osteogenic microspheres, and the bottom half (3 mm) were comprised only osteogenic microspheres. Options to sinter microsphere-based scaffolds include heat [16], carbon dioxide [17,18] and solvent/nonsolvent sintering [13]. In the current study, the stacked microspheres were sintered together using ethanol-acetone (95:5 v/v) for 45 min and were further lyophilized at -20°C for 48 h. The resulting scaffolds were 6 mm in diameter and 6 mm height.…”