Acellular Mineral Deposition in Collagen-Based Biomaterials Incubated in Cell Culture Media

Abstract

Rapid developments in tissue engineering have renewed interest in biodegradable three-dimensional structures such as collagen-based biomaterials. Collagen matrices seeded in vitro with fibroblasts, osteoblasts, and chondrocytes can form tissues resembling skin, bone, and cartilage that could be used as functional substitutes for damaged tissues. Collagen is associated with both dystrophic calcification of collagenous implants and bone mineralization. We report here the calcification properties of collagen sponges incubated in cell-free media. Mineral deposited in sponges was identified by X-ray and electron diffraction, Fourier transform infrared spectroscopy, and the molar ratio of calcium:phosphorus (Ca:P) as a poorly crystalline apatite similar to bone. The degree of calcification increased with length of incubation and the Ca and P content of the media, with 10-15% Ca (dry weight) after 21 days' incubation in media containing 1.6-3 mM Ca and a Ca x P molar product of 2-3 mM(2), but only 2% Ca after incubation in medium with 1.33 mM Ca and a 1.7 mM(2) Ca x P molar product. Mineral deposition was completely inhibited in sponges that were washed extensively and initially contained less than 0.01% P. Readdition of phosphate in these sponges and subsequent freeze drying and sterilization restore their mineralization capacity, suggesting that collagen per se cannot initiate calcification and that the inorganic phosphate content associated with the collagen preparation process is in the solid state a potential nucleator. Addition of chondroitin 4-sulfate to the sponges partially or totally inhibited mineral deposition, even though 80-90% of the compound was released within 24 hours. These results indicate that acellular calcification of collagen-based biomaterials can occur under the culture conditions currently used in tissue engineering.

Osteoinductive PolyHIPE Foams as Injectable Bone Grafts

“…48 Studies conducted on collagen sponges in media containing 1.6 mM calcium illustrated minimal calcium deposition on phosphate-free scaffolds compared to 10 wt% calcium deposition on sponges with phosphate indicating the potential role of phosphates as a site of nucleation for mineralization. 49 The basal media utilized in this study contain 1.8 mM calcium plus the calcium found in the fetal bovine serum supplemented to the media. Therefore, we would expect a substantial amount of calcium deposition on the PFDMA-based polyHIPEs in these media conditions.…”

A Review of the Biocompatibility of Implantable Devices: Current Challenges to Overcome Foreign Body Response

“…These include collagen sponges, 158 polyurethane, 159,160 and PVA. 161,162 For instance, others have investigated the calcification properties of collagen sponges incubated in cell-free media and indicated that a cellular calcification of collagen-based biomaterials can occur under the culture conditions currently used in tissue engineering.…”

“…161,162 For instance, others have investigated the calcification properties of collagen sponges incubated in cell-free media and indicated that a cellular calcification of collagen-based biomaterials can occur under the culture conditions currently used in tissue engineering. 158,163,164 Levy et al 164 implanted collagen sponges that were cross-linked with glutaraldehyde and formaldehyde subcutaneously into rats for 21 days and observed calcification. Golomb and associates reported the formation of calcium phosphate deposits in a polyurethane matrix in both in vitro 159 and in vivo studies.…”

Effect of extremely low frequency magnetic field in prevention of spinal cord injury-induced osteoporosis

“…ELF-MF has been suggested to promote the formation of matrix protein, namely collagen, OC, and ALP in bone cell cultures [43][44][45]. In our model of SCIinduced osteoporosis, ELF-MF also increased the concentration of collagen I, OC, and ALP, indicating the formation of matrix protein in the bones, wherein collagen I specifically provides a site for mineral precipitation and OC and ALP for its mineralization [46]. An increased mineralization in sublesional bones in our ELF-MF exposed rats with SCI is further supported by their increase in BMC and BMD, with a concomitant decrease in water content and microarchitecture.…”