Biomedical applications ranging from tissue engineering to drug delivery systems require versatile biomaterials based on the scalable and tunable production of biopolymer nanofibers under physiological conditions. These requirements can be successfully met by a novel extrusion process through nanoporous aluminum oxide templates, which is presented in this study. With this simple method we are able to control the nanofiber diameter by chosing the size of the nanopores and the concentration of the biopolymer feed solution. Nanofiber assembly into different hierarchical fiber arrangements can be achieved with a wide variety of different proteins ranging from the intracellular proteins actin, α-actinin and myosin to the extracellular matrix components collagen, fibronectin, fibrinogen, elastin and laminin. The extrusion of nanofibers can even be applied to the polysaccharides hyaluronan, chitosan and chondroitin sulphate. Moreover, blends of different proteins or proteins and polysaccharides can be extruded into composite nanofibers. With these features our template-assisted extrusion process will lead to new avenues in the development of nanofibrous biomaterials.
Objective. To study age-related (as opposed to arthritis-related) changes in collagen and proteoglycan turnover.Methods. Macroscopically nondegenerate normal ankle cartilage obtained from 30 donors (ages 16-75 years) was processed for in situ hybridization to detect messenger RNA (mRNA) of type IIB collagen (CIIB); antibodies to the C-propeptide of type II collagen (CPII), to the type II collagen (CII) collagenasegenerated cleavage neoepitope (Col2-3/4C short ), and to the CII denaturation product (Col2-3/4m) were used for immunohistochemistry analysis and immunoassay. In addition, immunoblotting was used to detect the 4 collagenases. Assays were also performed to detect glycosaminoglycan (GAG) content and the 846 epitope of aggrecan.Results. There were no significant changes in CII, GAG, and the content of the 846 epitope after the age of 30 years. Both mRNA for CIIB and the CPII were present in all zones, and CPII content did not change significantly with age. While the collagenase-cleaved CII showed a trend to increase with age, the denatured collagen did not. However, the molar ratio of cleaved versus denatured collagen was positively correlated with age. All 4 collagenases were detectable in the ankle cartilage but showed no identifiable changes in content with age.Conclusion. Synthesis and degradation of CII is associated with the pericellular matrix and is maintained at a steady state throughout life. The contents of CII and proteoglycan did not change. There was a significant reduction in the denaturation of CII with age, relative to collagenase-mediated cleavage. These observations reveal that, in aging of the intact ankle articular cartilage, there is no evidence of molecular degenerative changes of the kind observed in osteoarthritis, thereby distinguishing aging from the osteoarthritis process.The talar cartilages from the talocrural joint of the ankle offer opportunities for studying age-related changes in articular cartilage. We have shown that in a population of 470 adult organ donors (21-74 years of age), ϳ62% of the talar cartilages exhibited no macroscopic signs of degenerative changes often seen increasingly with age in other joints, such as the knee (1). Thus, samples from different donors can be studied with greater assurances that changes are associated with aging of the cartilage rather than with degenerative changes. Other advantages of using the ankle cartilages for studies of aging are that the talar cartilage is more uniform in thickness (1-2 mm [2]), representing a more consistent ratio of superficial to deep chondrocytes, and the talar cartilage is more uniform in stiffness (3,4).While degenerative changes and osteoarthritis (OA) do develop in the ankle (5), it is rare (6) compared with other joints, such as the knee. Our studies reveal that there are differences between the normal articular cartilages of the knee and ankle joints that may, in part, help to explain the differences in susceptibility to OA. Ankle cartilage is less responsive to catabolic stimulation by either fibronect...
To shed light on cell-adhesion-related molecular pathways, synthetic cells offer the unique advantage of a well-controlled model system with reduced molecular complexity. Herein, we show that liposomes with the reconstituted platelet integrin αIIbβ3 as the adhesion-mediating transmembrane protein are a functional minimal cell model for studying cellular adhesion mechanisms in a defined environment. The interaction of these synthetic cells with various extracellular matrix proteins was analyzed using a quartz crystal microbalance with dissipation monitoring. The data indicated that integrin was functionally incorporated into the lipid vesicles, thus enabling integrin-specific adhesion of the engineered liposomes to fibrinogen- and fibronectin-functionalized surfaces. Then, we were able to initiate the detachment of integrin liposomes from these surfaces in the presence of the peptide GRGDSP, a process that is even faster with our newly synthesized peptide mimetic SN529, which specifically inhibits the integrin αIIbβ3.
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