This paper presents the tribological properties of silicon and oxygen incorporated diamond-like carbon coatings tested in simulated body fluid and bovine serum albumin environments. The tests were performed using a ball-on-disc tribometer with an AISI316L steel counterbody. The wear tracks and wear scars were analyzed using optical microscopy and a nanoindenter. The interaction between the coating and the working environment was analyzed by Fourier transform infrared spectroscopy, whereas changes in the chemical structure before and after the tribological tests were compared with the use of Raman spectroscopy. Our study showed that the tribological parameters are governed by the presence of oxygen rather than the changing concentration of silicon. Both of the spectroscopy results confirm this statement, indicating that coatings with low concentrations of silicon and oxygen appear to be better candidates for biological applications in terms of wear resistance.

All forms of vitamin A have a similar structure and physiological functions in the body. These compounds can be classified as retinoids, including moieties with a common structure of four isoprenoid units of natural or synthetic origin. Vitamin A is generally uptake from products of animal origin (retinol and its derivatives) or from plants as provitamin A (carotenoids). Vitamin A is fat-soluble, so it is easily absorbed and transported in the body. The main storage sites are the liver and adipose tissue. Excessive amounts of the vitamin may lead to the development of different abnormal processes in the human body. Apart from being crucial for retina conditions and functions and the immune system, vitamin A is also deeply involved in DNA repair mechanisms. Its antioxidant nature helps to reduce the oxidative damage to DNA by neutralizing free radicals and thus decreasing the oxidative stress. On the other hand, vitamin A deficiency leads to lower antioxidant enzyme activity, which results in the weakening of the defense system against free radicals. This study aims to elucidate the mechanisms of DNA repair and determine the role of carotenoids, vitamin A, and its derivatives as contributing factors in this process. This review synthesizes the current knowledge on the dual role of vitamin A in DNA integrity by examining the conditions under which it acts as a genotoxic agent versus a facilitator of DNA repair. This article also discusses the role of vitamin A in inhibiting oxidative stress and its anti- and pro-cancer impact.