Vitamin E stability

P. Bracco, E. Oral, Vitamin E-stabilized UHMWPE for total joint implants a review, Clin. Orthop. Relat. Res. 469 (2011) 2286-2293. 

Vitamin E stabilizes erythrocytes against lysis initiated by vitamin A vitro (Lucy and Dingle, 1964) and vivo (Soliman, 1972). Other reports demonstrated the conservation of hepatic stores of vitamin A by vitamin E (Davies and Moore, 1941) and confirmed by Cawthorne et al (1968). However, utilizations of 3-carotene in the presence of high intakes of tocopherol were blocked (Arnrich, 1978). The latter study suggested that tocopherol interacts with 3 carotene in the biochemical steps that occur just before the formation of retinol. 

Thermally treated materials showed TG patterns similar to those observed for neat and irradiated polyethylene (Figure 2.6). However, the vitamin E-stabilized irradiated UHMWPE exhibited a distinct feature at the beginning of the experiment (Figure 2.7). 

This effect was especially noticeable after vitamin E stabilization, as registered a significant rise between 6°C and 15°C, with respect to 50 and 100 kGy as-irradiated UHMWPEs, respectively. 

Wannomae K, MicheU B, Lozynsky A, Malhi A, Oral E, Muratoglu O. Vitamin E-stabilized, irradiated UHMWPE for cruciate-retaining knees. Transactions, 53rd Annual Meeting of the Orthopaedic Research Society. San Diego, CA 2007.1783. 

In the early 1990s, researchers from the University of Torino initiated studies on UHMWPE, and, in particular, on radiation-induced oxidation of UHMWPE. As a consequence of their previous experience in the field of oxidation and stabilization of polyolefins, the researchers were immediately oriented toward the search of a suitable stabilizer. By the end of 1994, they filed an Italian patent on vitamin E stabilized UHMWPE for orthopaedic applications. At the same time, they started an initial collaboration with former PolyHiSolidur and Ticona to produce a first experimental UHMWPE sample plate of 20 X 20 X 5 cm containing 5000ppm (0.5% w/w) of vitamin E. On this sample they started the first experimental studies. In the decade that followed, new samples were produced by blending UHMWPE powder with vitamin E (Ronotec 2001, Hoffman-LaRoche), using a technique similar to that described in the previous section and following by consolidation in an industrial facility. In 2005, additional samples were provided thanks to a renewed collaboration with Ticona, Quadrant, and Orthoplastics. 

Studies from the Piedmont group indicate that vitamin E-blended UHMWPE was able to induce a PP2A-dependent increase in the matrix metalloproteinase 9 (MMP-9) release from granulocytes in the absence of the typical oxidative stress that is considered a hallmark of granulocytic activation [37]. These data emphasize the possibility that the use of vitamin-E-stabilized UHMWPE could modulate the in situ tissue remodeling and immune response through MMP-9 release and growth factor activation at the biomaterial-tissue interface. 

E J. Medel, M. J. Martinez-Morlanes, P. J. Alonso, J. Rubin, E J. Pascual and J. A. Pu rtolas, Microstructure, thermo oxidation and mechanical behavior of a novel highly linear, vitamin E stabilized, UHMWPE. Materials Science and Engineering C 33,182-188 (2013). 

Vitamin E stabilized and melted samples display the better oxidative stability. However, the stabilization by vitamin E is possible without changing the polymer morphology i.e. altering some of the other mechanical properties (impact resistance. Youngs modulus, fatigue crack resistance...). 

J. Fu, B.N. Doshi, E. Oral, O.K. Muratoglu. High temperature melted, radiation cross-linked, vitamin E stabilized oxidation resistant UHMWPE with low wear and high impact strength. Polymer 54(1), 199-209, 8 January (2013). 

H. Haider, J.N. Weisenburger, S.M. Kurtz, C.M. Rimnac, J. Freedman, D.W. Schroeder, K.L. Garvin. Does Vitamin E-Stabilized Ultrahigh-Molecular-Weight Polyethylene Address Concerns of Cross-Linked Polyethylene in Total Knee Arthroplasty The Journal of Arthroplasty 27(3), 461-469, March (2012). 

The third chapter mainly concentrates on stabilization of irradiated polyethylene by the introduction of antioxidants (vitamin E). The discussion of this chapter has two parts. The first part delineates the main types of antioxidants, stabilization by Vitamin E, structure and biological function of vitamin E, mechanism of stabilization of vitamin E, methods of incorporation of vitamin E, vitamin E stabilized polyethylenes the second part discusses the analysis of the content of vitamin E, using such instruments as FTIR, UV, HPLC and thermal methods. 

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