Additive Manufacturing of Bioresorbable Scaffolds with Microscale Topograph

Introduction:: Engineering biomaterial scaffolds with instructive physicochemical properties represents a promising strategy for the regeneration of damaged or diseased tissues. Surface topography, as an important extracellular matrix factor, is known to dictate cellular behaviors. However, previous studies are largely restricted to 2D planar substrates and in vitro evaluations for proof-of-concept. The exploitation of topographical effects to more clinically relevant 3D scaffolds aimed at tissue regeneration has been limited by the difficulty of manufacturing topographic patterns in a controlled manner. Recently, laser processing and sacrificial templating have been developed to introduce topographic patterns in pre-fabricated 3D scaffolds to guide cell responses and regeneration of well-structured, functional tissues. Although promising, these methods involve time-consuming multiple steps and can alter materials properties. Therefore, the high-efficient manufacturing of 3D scaffolds with microscale topography remains challenging. Herein, we demonstrated the high-speed and single-step fabrication of 3D scaffolds with microscale topographic patterns via an additive manufacturing process, i.e. micro-continuous liquid interface production (μCLIP). The presence of microscale topographic patterns with size of 12–80 μm on the citrate-based bioresorbable scaffolds induced strong cell alignment and tissue organization.


Materials and Methods:: The bioresorbable citrate-based inks were comprised of 75 wt.% methacrylated poly(1,12 dodecamethylene citrate) (mPDC), 2.2 wt.% Irgacure 819, and 3.0 wt.% Ethyl 4-dimethylamino benzoate (EDAB) in the ethanol. The tubular scaffolds with groove patterns (width = gap = 12, 20, 40, 80 μm; height = 40 μm) were fabricated using a home-built μCLIP process where the polydimethylsiloxane (PDMS) is used as an oxygen permeable window and a 365 nm light source is used. Working curves were determined by empirically measuring the curing depths as functions of light dosage in order to determine the optimal printing conditions. Scanning electron microscope (SEM) was used to observe the geometry and size of 3D-printed patterns on scaffolds. Human umbilical vein endothelial cells (HUVECs) were seeded and grown on 3D-printed tubular scaffolds to evaluate their responses to surface topographic patterns. The immunostaining of F-actin, nuclei, and functional marker of CD144 was used to evaluate cell morphology and functions on 3D-printed tubular platform.


Results, Conclusions, and Discussions:: The well-defined topography with aligned groove patterns and size of 12-80 μm, which spans across the single-cell size, has been simultaneously generated in the luminal surfaces of a 3D-printed tubular scaffolds (Figure 1A). The fabrication speed of micropatterned scaffolds is 4 mm/min that is dramatically faster than the existing methods, which can take hours for laser machining and days for sacrificial templating. This in-situ, high-resolution, and high-speed patterning on 3D scaffolds is accomplished by the μCLIP technology with optimized manufacturing conditions by robustly locating the optimal focal plan and matching the layer thickness to the penetration depth of the light in the ink. Human umbilical vein endothelial cells (HUVECs) grown inside the tubular scaffolds showed significant alignment along the produced groove patterns as compared to the random orientation of cells grown on the non-patterned scaffolds (Figure 1B). Moreover, cells grown on groove patterns showed upregulated expression of CD144 (VE-cadherin), which is an important functional marker of healthy endothelial cells, when compared to the cells grown on non-patterned surfaces. This data suggests that 3D-printed scaffolds with groove patterns can induce well-structured tissue organization and benefit the regeneration of tissues with aligned structures, such as cardiac, neural, and muscle tissues.



We have successfully developed a μCLIP-based additive manufacturing technique to enable the high-resolution and high-speed fabrication of microscale topographic patterns with well-controlled geometry and size on 3D scaffolds. The 3D-printed scaffolds with microscale groove patterns induced cell alignment and elongation along the patterns and ultimately the well-structured tissue formation. This technique provides a highly effective and precise manufacturing of 3D scaffolds with well-controlled topographic patterns, which could potentially favor the functional regeneration of a wide spectrum of tissues.


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