DETERMINATION OF COLLAGEN-PROTEOGLYCAN INTERACTIONS IN-VITRO

The objective of this study was to characterize the physical interacti ons of the molecular networks formed by mixtures of collagen and prote oglycan in vitro. Pure proteoglycan aggrecan solutions, collagen (type II) suspensions and mixtures of these molecules in varying proportion s and concentrations were subjected to viscometric how measurements us ing a cone-on-plate viscometer. Linear viscoelastic and non-Newtonian dow properties of these solutions and suspensions were described using a second-order statistical network theory for polymeric fluids (Zhu e t al., 1991, J. Biomechanics 24, 1007-1018). This theory provides a se t of material coefficients which relate the macroscopic how behavior o f the fluid to an idealized molecular network structure. The results i ndicated distinct differences between the how properties of pure colla gen suspensions and those of pure proteoglycan solutions. The collagen network showed much greater shear stiffness and more effective energy storage capability than the proteoglycan network. The relative propor tion of collagen to proteoglycan is,the dominant factor in determining the flow behavior of the mixtures. Analysis of the statistical networ k theory indicated that the collagen in a collagen-proteoglycan mixtur e enhances molecular interactions by increasing the amount of entangle ment interactions and/or the strength of interaction, while aggrecan a cts to reduce the number and/or strength of molecular interactions. Th ese results characterize the physical interactions between type II col lagen and aggrecan and provide some insight into their potential roles in giving articular cartilage its mechanical behavior. (C) 1996 Elsev ier Science Ltd.