The extracellular matrix (ECM) is a complex 3D framework of macromolecules, which regulate cell bioactivity via chemical and physical properties. The ECM's physical properties, including stiffness and physical constraints to cell shape, regulate actomyosin cytoskeleton contractions, which induce signaling cascades influencing gene expression and cell fate. Engineering such bioactivity, a.k.a., mechanotransduction, has been mainly achieved by 2D platforms such as micropatterns. These platforms cause cytoskeletal contractions with apico‐basal polarity and can induce mechanotransduction that is unnatural to most cells in native ECMs. An effective method to engineer mechanotransduction in 3D is needed. This work creates FiberGel, a 3D artificial ECM comprised of sub‐cellular scale fibers. These microfibers can crosslink into defined microstructures with the fibers' diameter, stiffness, and alignment independently tuned. Most importantly, cells are blended amongst the fibers prior to crosslinking, leading to homogeneously cellularized scaffolds. Studies using mesenchymal stem cells showed that the microfibers' diameter, stiffness, and alignment regulate 3D cell shape and the nuclei translocation of transcriptional coactivators YAP/TAZ (yes‐associated protein/transcriptional coactivator), which enables the control of cell differentiation and tissue formation. A novel technology based on repeated stretching and folding is created to synthesize FiberGel. This 3D platform can significantly contribute to mechanotransduction research and applications.
Direct laser writing (DLW) via two‐photon polymerization is an emerging highly precise technique for the fabrication of intricate cellular scaffolds. Despite recent progress in using two‐photon‐polymerized scaffolds to probe fundamental cell behaviors, new methods to direct and modulate microscale cell alignment and selective cell adhesion using two‐photon‐polymerized microstructures are of keen interest. Here, a DLW‐fabricated 2D and 3D hydrogel microstructures, with alternating soft and stiff regions, for precisely controlled cell alignment are reported. The use of both cell‐adhesive and cell‐repellent hydrogels allows selective adhesion and alignment of human mesenchymal stem cells within the printed structure. Importantly, DLW patterning enables cell alignment on flat surfaces as well as irregular and curved 3D microstructures, which are otherwise challenging to pattern with cells.
more » « less- Award ID(s):
- 1647837
- NSF-PAR ID:
- 10452323
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Macromolecular Bioscience
- Volume:
- 21
- Issue:
- 5
- ISSN:
- 1616-5187
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract We demonstrate the use of tip-enhanced Raman spectroscopy (TERS) on polymeric microstructures fabricated by two-photon polymerization direct laser writing (TPP-DLW). Compared to the signal intensity obtained in confocal Raman microscopy, a linear enhancement of almost two times is measured when using TERS. Because the probing volume is much smaller in TERS than in confocal Raman microscopy, the effective signal enhancement is estimated to be ca. 104. We obtain chemical maps of TPP microstructures using TERS with relatively short acquisition times and with high spatial resolution as defined by the metallic tip apex radius of curvature. We take advantage of this high resolution to study the homogeneity of the polymer network in TPP microstructures printed in an acrylic-based resin. We find that the polymer degree of conversion varies by about 30% within a distance of only 100 nm. The combination of high resolution topographical and chemical data delivered by TERS provides an effective analytical tool for studying TPP-DLW materials in a non-destructive way.
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