Ana Paula Dias Ribeiro - Faculdade de Odontologia - Unesp

living organism, in response to the oxidative stress generated by the presence of ROS,the defense the system releases several endogenous antioxidant agents, such asperoxidases and catalases, which promotes an enzymatic degradation of those highlyreactive and unstable molecules to avoid excessive tissue damage [25].The interaction of curcumin with biomolecules and cells has beeninvestigated. Results of recent studies have indicated that curcumin bindspreferentially to lipid membrane and some cell proteins [18]. Bruzell et al. [26]observed that PDT using curcumin at 13.5 µM in combination with halogen lightillumination (6 J/cm 2 ) resulted in around 80% of necrotic cell death and less the 20%of apoptotic cell death. In the present study, the SEM analysis revealed that thefibroblast cell cultures subjected to PDT exhibited a significant decrease in thenumber of cells adhered to the glass substrate. In addition, several cytoplasmic restsremained adhered to the glass coverslip, indicating rupture of the cytoplasmicmembrane and suggesting necrotic cell death.Another factor to be considered for the use of curcumin as a PS is the vehicleused to deliver this compound. As curcumin is relatively insoluble in water, variousdiluents like acetone, DMSO and ethanol as well as other preparations such asmicelles, cyclodextrine, liposomes and hydrophilic polymers have been proposed asvehicles for curcumin [26]. DMSO is the most commonly used vehicle to evaluate thephototoxic effects of PDT in in vitro studies and it has become a control to evaluateseveral types of drug vehicles because of its excellent solvent propriety [15,20]. In thepresent study, dilution of curcumin in DMSO increased its solubility in aqueoussolutions, improving its bioavailability and promoting bacterial photokilling [27].Bruzell et al. [26] reported that the use of curcumin at 13.5 µM diluted in DMSO wassufficient to reduce by 80% the viability of rat submandibular salivary gland acinarcells. However, preparation of the same curcumin concentration in cyclodextrine orliposome did not cause reduction of enzymatic activity. It is known that DMSO is notan optimal vehicle for in vivo applications because it increases membranepermeability to the drugs and may cause tissue damage and systemic effects [20].Therefore, further studies should evaluate different vehicles as efficient as DMSO forcurcumin to exert photokilling against bacterial strains.Both essential components of PDT - the PS and the visible light - can alter cellfunctions. However, in the present study, no significant differences were observedbetween the groups exposed only to curcumin (C+L-) or blue LED light (C-L+) when