An Insight Into the Potentiation Effect of Potassium Iodide on aPDT Efficacy

Abstract

Antimicrobial photodynamic therapy (aPDT) is gaining a special importance as an effective approach against multidrug-resistant strains responsible of fatal infections. The addition of potassium iodide (KI), a non-toxic salt, is recognized to increase the aPDT efficiency of some photosensitizers (PSs) on a broad-spectrum of microorganisms. As the reported cases only refer positive aPDT potentiation results, in this work we selected a broad range of porphyrinic and non-porphyrinic PSs in order to gain a more comprehensive knowledge about this aPDT potentiation by KI. For this evaluation were selected a series of meso-tetraarylporphyrins positively charged at meso positions or at β-pyrrolic positions and the non-porphyrinic dyes Methylene blue, Rose Bengal, Toluidine Blue O, Malachite Green and Crystal Violet; the assays were performed using a bioluminescent E. coli strain as a model. The results indicate that KI has also the ability to potentiate the aPDT process mediated by some of the cationic PSs [Tri-Py(+)-Me, Tetra-Py(+)-Me, Form, RB, MB, Mono-Py(+)-Me, β-ImiPhTPP, β-ImiPyTPP, and β-BrImiPyTPP] allowing a drastic reduction of the treatment time as well as of the PS concentration. However, the efficacy of some porphyrinic and non-porphyrinic PSs [Di-Py(+)-Me opp, Di-Py(+)-Me adj, Tetra-Py, TBO, CV, and MG] was not improved by the presence of the coadjuvant. For the PSs tested in this study, the ones capable to decompose the peroxyiodide into iodine (easily detectable by spectroscopy or by the visual appearance of a blue color in the presence of amylose) were the most promising ones to be used in combination with KI. Although these studies confirmed that the generation of 1O2 is an important fact in this process, the PS structure (charge number and charge position), aggregation behavior and affinity for the cell membrane are also important features to be taken in account.

The Remarkable Effect of Potassium Iodide in Eosin and Rose Bengal Photodynamic Action against Salmonella Typhimurium and Staphylococcus aureus

“…Xanthene dyes have been considered good PSs to induce bacterial photoinactivation due to their low price, high molar absorptivity, and high singlet oxygen quantum yield (Φ ∆ ) [18,33,35]. The xanthene dyes, rose bengal (RB) and eosin Y (EOS) (Figure 1), have already proven to be effective against gram-positive and gram-negative bacteria [19,20,31,36], however, these dyes showed to be more effective against gram-positive bacteria. This limitation can be overcome by the use of different organic salts such as sodium bromide, sodium azide, sodium thiocyanate, and potassium iodide (KI) [36][37][38].…”

“Smart” Antimicrobial Nanocomplexes with Potential to Decrease Surgical Site Infections (SSI)

“…Polyiodides consist of [I 2k+n ] n− units and are stabilized by donor-acceptor interactions of the combined iodine molecules and iodide ions [33][34][35]. Triiodides are the smallest examples of polyiodides and contain either symmetric or asymmetric [I-I-I] − groups, which are connected to each other by halogen and/or hydrogen bonding [36,37] Triiodides were successfully used in combination with phototherapy in wound healing [38,39]. Ideal, symmetric triiodide units are characterized by pure halogen bonding and can be identified by characteristic Raman stretching Pharmaceutics 2020, 12, 361 3 of 36 vibrations at 108 cm −1 due to the electron density redistribution during the formation of halogen bonds [27,40,41].…”

Photodynamic Inactivation of Candida albicans in Blood Plasma and Whole Blood

“…Figure 1 [65,66,74]. The UV-Vis spectrum of these photosensitizers was already reported in the literature [64,65].…”

“…The selected porphyrinic PSs have already proved their efficiency in the photoinactivation of Escherichia coli [5,64,65], Pseudomonas syringe [66], Staphylococcus aureus [5,64,65], and C. albicans [54]. FORM has been considered an excellent alternative to the highly efficient constituents, Tri-Py(+)-Me and Tetra-Py(+)-Me, since production costs were reduced significantly due to its use [54,64,65]. Moreover, Tri-Py(+)-Me was recently described as a potential PS for the inactivation of E. coli and S. aureus in blood plasma and whole blood [5].…”

“…The MB (used as PS reference), was less effective, causing a decrease of 0.8 log 10 in C. calbicans survival after 270 min of irradiation. to its use [54,64,65]. Moreover, Tri-Py(+)-Me was recently described as a potential PS for the inactivation of E. coli and S. aureus in blood plasma and whole blood [5].…”