The effect of
divalent cations,
EDTA and
chitosan (CS) on the uptake and photoinactivation of Escherichia coli produced by
5,10,15,20-tetrakis(4-N,N,N-trimethylammoniumphenyl)porphyrin (
TMAP(4+)), 5,10-di(4-methylphenyl)-15,20-di(4-N,N,N-trimethylammoniumphenyl)porphyrin (MPAP(2+)) and 5,10,15,20-tetra(4-sulphonatophenyl)porphyrin (TPPS(4-)) were examined under different conditions. These
porphyrins were rapidly bound to E. coli cells (<2.5min) and the uptake of
photosensitizers was not dependent on incubation temperature, reaching values of 0.61, 0.18 and 0.08nmol/10(8) cells for
TMAP(4+), MPAP(2+) and TPPS(4-), respectively. The addition of Ca(2+) or Mg(2+) to the cultures enhanced the uptake of MPAP(2+) and TPPS(4-) by cells. In contrast, the amount of
TMAP(4+) bound to cells was decreased. The presence of
EDTA produced an increase in the uptake of
porphyrins by cells, while CS mainly enhanced the amount of TPPS(4-) bound to E. coli. The photoinactivation of E. coli cells mediated by
TMAP(4+) was highly effective even at low concentration (1μM) and short irradiation period (5min). However, a reduction in the
phototoxicity was found for
TMAP(4+) in presence of Ca(2+) and Mg(2+). In contrast, the phototoxic activity mediated by MPAP(2+) and TPPS(4-) was increased. Addition of
EDTA did not show effect on the photoinactivation induced by cationic
porphyrins, while a small enhance was found for TPPS(4-). Moreover, inactivation of E. coli cells was achieved in the presence CS. This cationic
polymer was antimicrobial by itself in the dark. Using a slightly toxic CS concentration, the phototoxic activity induced by
TMAP(4+) was diminished. This effect was mainly observed at lower concentration of
TMAP(4+) (0.5-1μM). In contrast, an increase in E. coli photoinactivation was obtained for MPAP(2+) and TPPS(4-) in presence of CS. Thus, this natural polymeric destabilizer agent mainly benefited the photoinactivation mediated by TPPS(4-).