Full text loading...
Atomic force microscopy images of type-I collagen molecules immobilized non-covalently on a hydrophilic ITO surface at different temperatures and time periods of immobilization; (a) 30 min, (b) 3 h, (c) 48 h at 4 °C, and (d) 30 min, (e) 3 h, and (f) 48 h at 26 °C. A liquid-type AFM with the tapping mode was used to obtain these high-resolution images; the initial concentration of collagen molecules was 0.135 μg/ml (prepared in phosphate buffered saline).
Atomic force microscopy images of type-I collagen molecules immobilized non-covalently on a hydrophilic mica surface with an initial concentration of 0.135 μg/ml (prepared in phosphate buffered saline) under various conditions; (a) 30 min, (b) 3 h, (c) 48 h at 4 °C, and (d) 30 min, (e) 3 h, and (f) 48 h at 26 °C. A liquid-type AFM, with tapping mode, was used to pursue these high-resolution images; the morphological characteristics (morphological change from amorphous clusters to collagen fibrils) of collagen molecules on ITO and mica surfaces were similar at two different temperatures.
Atomic force microscopy images of type-I collagen molecules immobilized non-covalently on a hydrophobic poly(dimethylsiloxane) surface via the application of a liquid-type tapping-mode AFM with an initial concentration of 0.135 μg/ml (prepared in phosphate buffered saline) under three immobilization durations and two temperatures; (a) 30 min, (b) 3 h, (c) 48 h at 4 °C, and (d) 30 min, (e) 3 h, and (f) 48 h at 26 °C. During the non-covalent immobilization of collagen molecules on a hydrophobic poly(dimethylsiloxane) surface, collagen molecules assembled into collagen fibrils at 4 °C after 30 min of immobilization; when the immobilization duration was increased, not only did collagen molecules assemble into fibrils but they also formed a three-dimensional matrix with an extended size at 4 °C, as shown in (c). However, when we immobilized collagen molecules on a poly(dimethylsiloxane) surface at 26 °C, it was likely that collagen molecules became the nucleation site for the crystallization of inorganic salts; regular patterns built on the collagen molecules were observed in the AFM images (e and f), as the crystallization occurred around the collagen molecules.
Adhesion force measurements versus an increase in the immobilization time from 30 min to 48 h on (a) ITO, (b) mica, and (c) poly(dimethylsiloxane) via a liquid-type AFM with the contact mode at both 4 °C and 26 °C. All adhesion force measurements (collagen molecules on either a hydrophilic or a hydrophobic surface) exhibited the “decrease-increase” trend. The initial concentration of collagen was 0.135 μg/ml (prepared in phosphate buffered saline). Each datum is the mean of 50 replicates (N = 50), and the error bars represent the standard deviations of the adhesion force measurements.
Schematic of the self-assembly of collagen molecules on different surfaces at various stages (different immobilization times). In this schematic, type-I collagen molecules are viewed as “single particles” suspended in liquid on a hydrophobic surface (i.e., PDMS), but these “single particles” in liquid attach onto a hydrophilic surface (i.e., ITO or mica). The collagen molecules gradually assemble into microfibrils to form a dense structure with a larger size by covalently bonding with other collagen molecules (i.e., single collagen molecules as the fundamental building blocks in this study). With an increase in immobilization duration, the assembled microfibrils distribute homogeneously on either a hydrophobic or a hydrophilic surface, in order to form collagen fibrils (microfibrils as the building blocks of collagen fibrils).
Article metrics loading...