Scavenging of free radicals in gas-phase mainstream cigarette smoke by immobilized catalase at filter level

Catalase is well known as capable of inducing the decomposition of H2O2. In this study, a kind of immobilized catalase (entrapped in cross-linked chitosan beads) was dispersed in conventional acetate filter as an antioxidant additive. Quantitative estimation of the free radicals in mainstream cigarette smoke (MCS) was performed to address the effect of this modified filter. It was found that the levels of PBN adduct and NO center dot/NO2 center dot associated with the gas-phase mainstream cigarette smoke (GPCS) were efficiently decreased by similar to 40% through catalase filtering. Besides, the modified filter was found to lower the MCS-induced adverse biological effects including lipid peroxidation and mutagenicity. This was proved to be substantially attributed to the catalase-dependent breakdown of NO center dot which was stimulated by some of peroxides (most probably being H2O2), the dismutation products of tar particulate matters (TPM). These results highlighted a promising approach to reduce the smoking-associated health risks to passive smokers. Moreover, the mechanisms of catalase filtering may be helpful for the development of appropriate immobilized enzyme systems to be applied for reducing health risks associated with gaseous pollutants.