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Shoumyo Majumdar, Xiomara Calderon-Colon, Morgana Trexler, Oliver Schein, Jennifer Elisseeff; Electric field mediated alignment of collagen fibers in collagen Vitrigel materials. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3726.
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© ARVO (1962-2015); The Authors (2016-present)
Collagen vitrigels are thin, transparent biomaterial membranes with a high density of organized collagen fibrils. However collagen vitrigels do not possess the high degree of collagen fibril alignment present in native cornea, which is a requirement for thicker vitrigels to maintain optical clarity. We utilized electric field (EF) to align fibrils during gelation and vitrification. EF enabled fabrication of thick and highly transparent vitrigel materials (EFVs).
Collagen (commercially available atelocollagen type I) gels were prepared in the presence of 2 V/cm EF in a custom built mold with vertically placed electrodes using vitrigel media with HEPES (+β), basic media without HEPES (-β), or only 0.1 N NaOH. Vitrification and rehydration were carried out as previously described (Biomaterials 33 (2012) 8286-95). Transmittance was measured using a Synergy 2 microplate reader (Biotek). Samples were processed for TEM and stained with uranyl acetate; images were taken in a Philips CM120 TEM. Samples were compared to vitrigels prepared without the use of electric field.
Collagen membrane ultrastructure was significantly altered by the electric field. Fibril alignment was evident in EF samples (Figure 1), whereas regular vitrigels showed random fibrillar organization. While EFV [NaOH] membranes showed collagen fibrils of lower diameter, EFV[Media(+β)] samples demonstrated characteristic collagen banding and fibril diameter similar to cornea. Light absorption values in the visible light spectrum for the different samples are shown in Figure 2. EFV[Media(-β)] and EFV[NaOH] show lowest absorption, followed by EFV[Media(+β)].
EF influence alters the biomaterial ultrastructure, allowing collagen fibril alignment. Effects of fibril alignment were quantitatively assessed through transparency data. Quality of collagen fibrils generated through EF modulated vitrification is dependent on media components. Combination of EFV with [Media(+β)] results in vitrigels which absorb less light than regular vitrigels while maintaining presence of mature collagen fibers, which would aid in mimicking the natural environment for keratocyte growth and proliferation. Both of these characteristics of increased transparency and fibrillar organization are therefore significantly enhanced by the influence of electric field.
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