Nanoparticles for Photodynamic Therapy Applications - Intracellular Delivery: Fundamentals and Applications - page 554

Fig. 43 Meso -
tetrahydroxyphenyl
porphyrin, mTHPP

HO

OH

NH N

N HN

OH

OH

the nanoparticles, the PDT results on HT29 cancer cells line showed a moderate
activity whereas a good performance with HIG-82 Synoviocytes was observed.
For J774A.1 macrophages, nanoparticles were also toxic in the dark, probably due
to a lethal uptake of calcium. A good phototoxicity was also observed against the
bacterial strain S. Aureus (Gram positive) both with positively and negatively
charged nanoparticles loaded with mTHPP. Against P. aeruginosa (Gram nega-
tive) good phototoxicity was observed only with positively charged nanoparticles
loaded with mTHPP. At higher concentrations, methylene-blue loaded nanoparti-
cles where active against S. Aureus .

7.3 Zeolites

Zeolites are crystalline microporous alumino-silicates whose nanoparticles are
very promising for PDT applications. Strassert and co-workers ( 2009 ) proposed
the use of zeolite L nanocrystals 50 nm in both length and diameter for PDT
against antibiotic-resistant bacteria. The nanocrystal were loaded with (N,N¢) -
bis(2-6-dimethylphenyl)perylene-3,4,9,10-tetracarbodiimide (DXP, Fig. 44 ), which
was encapsulated by gas-phase insertion, for imaging and to label the cells. The
DXP-loaded zeolite-L nanocrystals were further functionalized with tetra-tert-
butyl-substituted Si IV , phthalocyaninedihydroxyle (PC, Fig. 45 ) by axial attach-
ment of the macrocycle's central silicon atom to OH groups of the zeolite L
surface. No energy transfer occurred from DXP to PC. The surface of the multi-
functional zeolites was coated with amino-groups to promote the adhesion to
bacteria. Indeed the zeolites are then positively charged, favoring adhesion to the
negatively charged membranes of the bacteria. The PDT activity of the zeolite
nanocrystals was tested on E. Coli and N. Gonorrhoeae bacteria. Irradiation for
2.5 h between 570 and 900 nm (3 mW cm −2 , light dose 27 J cm −2 ) led to the inac-
tivation of the cells (95% efficiency).