Formation of gold decorated porphyrin nanoparticles and evaluation of their photothermal and photodynamic activity.

A core-shell gold (Au) nanoparticle with improved photosensitization have been successfully fabricated using Au nanoparticles and 5,10,15,20 tetrakis pentafluorophenyl)-21H,23H-porphine (PF6) dye, forming a dyad through molecular self-assembly. Au nanoparticles were decorated on the shell and PF6 was placed in the core of the nanoparticles. Highly stable Au nanoparticles were achieved using PF6 with poly(N-vinylcaprolactam-co-N-vinylimidazole)-g-poly(D,L-lactide) graft copolymer hybridization. This was compared with hybridization using cetyltrimethylammonium bromide and polyethylene glycol-b-poly(D,L-lactide) for shell formation with PF6-Au. The resulting PF6-poly(N-vinylcaprolactam-co-N-vinylimidazole)-g-poly(D,L-lactide)-Au core-shell nanoparticle were utilized for photothermal and photodynamic activities. The spectroscopic analysis and zeta potential values of micelles revealed the presence of a thin Au layer coated on the PF6 nanoparticle surface, which generally enhanced the thermal stability of the gold nanoparticles and the photothermal effect of the shell. The core-shell PF6-Au nanoparticles were avidly taken up by cells and demonstrated cellular phototoxicity upon irradiation with 300W halogen lamps. The structural arrangement of PF6 dyes in the core-shell particles assures the effectiveness of singlet oxygen production. The study verifies that PF6 particles when companied with Au nanoparticles as PF6-Au have possible combinational applications in photodynamic and photothermal therapies for cancer cells because of their high production of singlet oxygen and heat.

Tailoring pigment dispersants with polyisobutylene twin-tail structures for electrowetting display application.

We have designed a class of highly hydrophobic dispersants for finely dispersing carbon black and organic pigment nanoparticles in apolar mediums. The synthesis involved the use of polyisobutylene-g-succinic anhydride (PIB-SA) and judiciously selected amines by amidation and imidation. The structures were characterized by infrared spectroscopy for anhydride functionalities in the starting materials and amide/imide linkages in the products. These polymeric forms of dispersants were structurally varied with respects to their PIB molecular weight, twin-tails, and linkages. Their relative performance for dispersing six different pigments in decane was evaluated against solution homogeneity, viscosity, stability, and particle size. The fine dispersion was achieved at particle sizes of ca. 100 nm, with the viscosity as low as 2-3 cP. The measurement of zeta potentials, which varied from -39.8 to -5.1 mV with pigment addition, revealed a strong surface-charge interaction between pigment and PIB dispersant molecules. Examination by TEM (transmission electronic microscope) showed the homogeneous dispersion of the primary structures of pigment particles at ca. 20 nm in diameter. The polymeric dispersants with different PIB tails and imide functionalities could be tailored for pigment stability in the oil phase, which is potentially suitable for the electrowetting devices.