Assessing Ribose-Induced Collagen Mechanics

Post-glycated 3D collagen matrices were elaborated as explained above using the same conditions of collagen fibers configuration (confocal reflectance imaging). The ribose-induced mechanical alterations in the collagen gels were examined on the 7^th, 14^th and 21^st days by assessing their Young’s elastic modulus, E, which is indicative of gel’s resistance to deformation. E was measured using a stand-alone AFM (Bioscope, Veeco, USA) coupled to an inverted optical microscope as previously described [33 (link)]. Briefly, the AFM measurements were taken using low spring constant cantilevers with pyramidal tips (nominal k = 0.01 N/m) (Microlever, Veeco), which were calibrated using the thermal noise method [34 (link)]. For each gel location, three force vs. piezo displacement curves (F-z curves) were acquired using a moderate loading force (~1 nN). For each gel location, E and the extent of gel indentation (d) were computed as the averages of the values obtained by least-squares fitting of a contact elastic model to each set of three F-z curves, as reported elsewhere [35 (link)]. The same protocol was applied on at least 9 random gel locations. For each treatment, the E data were normalized using the corresponding value obtained from 0 mM ribose gel at the 7^th day.