Article

Non-invasive characterization of structure and morphology of silk fibroin biomaterials using non-linear microscopy.

Biomedical Engineering Department, Tufts University, 4 Colby Street, Room 229, Medford, MA 02155, USA.
Biomaterials (Impact Factor: 8.31). 06/2008; 29(13):2015-24. DOI: 10.1016/j.biomaterials.2007.12.049
Source: PubMed

ABSTRACT Designing biomaterial scaffolds remains a major challenge in tissue engineering. Key to this challenge is improved understanding of the relationships between the scaffold properties and its degradation kinetics, as well as the cell interactions and the promotion of new matrix deposition. Here we present the use of non-linear spectroscopic imaging as a non-invasive method to characterize not only morphological, but also structural aspects of silkworm silk fibroin-based biomaterials, relying entirely on endogenous optical contrast. We demonstrate that two photon excited fluorescence and second harmonic generation are sensitive to the hydration, overall beta sheet content and molecular orientation of the sample. Thus, the functional content and high resolution afforded by these non-invasive approaches offer promise for identifying important connections between biomaterial design and functional engineered tissue development. The strategies described also have broader implications for understanding and tracking the remodeling of degradable biomaterials under dynamic conditions both in vitro and in vivo.

2 Followers
 · 
131 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Silk degumming process is regarded as the first key point in the preparation of silk-based materials. Emphasis of this paper is placed on the effect of sodium carbonate (Na2CO3) concentrations on degummed silk fibers, the derived aqueous silk solutions, and the final regenerated silk films. Obvious damage with exposure of silk fibrils was caused at 5% Na2CO3 concentration but no microstructure destruction was observed at 0.005% Na2CO3 concentration. Weight loss increased dramatically with increasing Na2CO3 concentration, further leading to a reduction in the degummed silk diameter and poorer thermal stability. Although little change has been found on β-sheet content of degummed silks, differences in molecular weight and rheological behavior of aqueous silk solutions from different Na2CO3 concentrations are clearly found which are associated with the subsequent structure and physical properties of the regenerated silk films. The results indicate that there is an inverse relationship between Na2CO3 concentrations and the thermal degradation, wettability, and mechanical properties of regenerated silk films. Hence, a suitable choice of Na2CO3 concentrations should be seriously considered to promote the development of different performances and applications of silk-based materials.
    Journal of the Textile Institute 05/2014; 106(3):311-319. DOI:10.1080/00405000.2014.919065 · 0.77 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The mechanism by which megakaryocytes (Mks) proliferate, differentiate, and release platelets into circulation are not well understood. Growing evidence indicates that a complex regulatory mechanism, involving cellular interactions, composition of the extracellular matrix and physical parameters such as oxygen tension, may contribute to the quiescent or permissive microenvironment related to Mk differentiation and maturation within the bone marrow. Differentiating human mesenchymal stem cells (hMSCs) into osteoblasts (hOSTs), we established an in vitro model for the osteoblastic niche. We demonstrated for the first time that the combination of HSCs, Mks and hypoxia sustain and promote bone formation by increasing type I collagen release from hOSTs and enhancing its fibrillar organization, as revealed by second harmonic generation microscopy. Through co-culture, we demonstrated that direct cell-cell contact modulates Mk maturation and differentiation. In particular we showed that low oxygen tension and direct interaction of hematopoietic stem cells (HSCs) with hOSTs inhibits Mk maturation and proplatelet formation (PPF). This regulatory mechanism was dependent on the fibrillar structure of type I collagen released by hOSTs and on the resulting engagement of the alpha2beta1 integrin. In contrast, normoxic conditions and the direct interaction of HSCs with undifferentiated hMSCs promoted Mk maturation and PPF, through a mechanism involving the VCAM-1 pathway. By combining cellular, physical and biochemical parameters, we mimicked an in vitro model of the osteoblastic niche that provides a physiological quiescent microenvironment where Mk differentiation and PPF are prevented. These findings serve as an important step in developing suitable in vitro systems to use for the study and manipulation of Mk differentiation and maturation in both normal and diseased states.
    PLoS ONE 12/2009; 4(12):e8359. DOI:10.1371/journal.pone.0008359 · 3.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The field of nonlinear optics has witnessed a rapid growth into biology within the last decade, driven largely by the observations of large nonlinear optical signals from native tissue in biological microscopy. The signals generated from collagen and other biopolymer assemblies exhibit intricate polarization-dependences that are intimately connected to local structure and orientation. A key step in bridging the macroscopic polarization to microscopic structure is the development and testing of predictive models for describing the NLO properties of biopolymer assemblies. In this Letter, we review the strengths and limitations of approaches for experimentally accessing the molecular tensors of peptides, nucleotides, and saccharides, which serve as the fundamental building blocks of biopolymers.
    Chemical Physics Letters 11/2008; 465(4-6):167-174. DOI:10.1016/j.cplett.2008.09.022 · 1.99 Impact Factor