Structural anisotropy, often observed in naturally occurring materials such as wood and human tissues, is central to the function in several engineered and non-engineered applications. In this study, we present the theory and proof-of-concept demonstration of an ultrasound-assisted non-contact manufacturing approach to create well-defined spatial patterns of micro-particles within a fluid matrix. A chamber with opposing pair of ultrasonic transducers was designed and prototyped based on standing bulk acoustic wave theory, and it was used to study the effects of ultrasound frequency (1, 1.5, 2, 3 MHz) and voltage amplitude (80, 160 mVpp) on alignment characteristics of polymer micro-particles (mean Ø = 8 μm) suspended in water (0.01 g/ml). The experimental results were consistent with theory in that the micro-particles aligned along linear strands, with the inter-strand spacing reducing with increasing frequency (p < 0.05). Increasing voltage amplitude reduced the time taken to align the particles, but it did not significantly change the observed spacing (p > 0.05). The observed spacing, however, was higher than the theoretical spacing of half-wavelength, for each frequency and amplitude. The alignment of living human adipose derived stem cells in viscous alginate hydrogel matrix was also successfully demonstrated. The approach presented herein can be scaled up into manufacturing processes, including layered manufacturing, to create highly functional mechanically and/or electrically anisotropic composites through controlled spatial geometry, as well as to biofabricate engineered tissues with aligned cells and extracellular matrix components to mimic natural tissues.
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This content will become publicly available on June 12, 2024
Label-Free Quantification of Microscopic Alignment in Engineered Tissue Scaffolds by Polarized Raman Spectroscopy
Various biomacromolecule components of extracellular matrix (ECM) link together to form a structurally stable composite. Monitoring of such matrix microstructure can be very important in studying structure-associated cellular processes, improving cellular function, and ensuring sufficient mechanical integrity in engineered tissues. This paper describes a novel method to study microscale alignment of matrix in engineered tissue scaffolds (ETS) that were usually composed of a variety of biomacromolecules derived by cells. as the organization of overall biomacromolecule network has been seldomly examined. First, a trained loading function was derived from Raman spectra of highly aligned native tissue via PCA, where prominent changes associated with Raman bands (e.g., 1444, 1465, 1605, 1627-1660 and 1665-1689 cm−1) were detected with respect to the polarized angle. These changes were mainly caused by the aligned matrix of many compounds within the tissue relative to the laser polarization, including proteins, lipids and carbohydrates. Hence this trained function was applied to quantify the alignment within ETS of various matrix components derived by cells. A simple metric called Amplitude Alignment Metric was derived to correlate the orientation dependence of polarized Raman spectra of ETS to the degree of matrix alignment. By acquiring polarized Raman spectra of ETS at micrometer regions, the Amplitude Alignment Metric was significantly higher in anisotropic ETS than isotropic ones. The PRS method showed a lower p-value for distinguishing the alignment between the two types of ETS as compared to the microscopic method for detecting fluorescently labeled protein matrices at similar microscopic scale. These results indicate the anisotropy of complex matrix in engineered tissue can be assessed at microscopic scale using a PRS-based simple metric, superior to traditional microscopic method. This PRS-based method can serve as a complementary tool for the design and assessment of engineered tissues that mimic the native matrix organizational microstructures.
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- Award ID(s):
- 1762791
- NSF-PAR ID:
- 10470478
- Publisher / Repository:
- AMER CHEMICAL SOC
- Date Published:
- Journal Name:
- ACS Biomaterials Science & Engineering
- Volume:
- 9
- Issue:
- 6
- ISSN:
- 2373-9878
- Page Range / eLocation ID:
- 3206 to 3218
- Subject(s) / Keyword(s):
- ["polarized Raman spectroscopy, principal component analysis, extracellular matrix, matrix alignment, engineered tissue scaffolds, anisotropy"]
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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