Adriana P. Gerola

Antiadhesive and Antibacterial Multilayer Films via Layer-by-Layer Assembly of TMC/Heparin Complexes

N-Trimethyl chitosan (TMC), an antibacterial agent, and heparin (HP), an antiadhesive biopolymer, were alternately deposited on modified polystyrene films, as substrates, to built antiadhesive and antibacterial multilayer films. The properties of the multilayer films were investigated by Fourier transform infrared spectroscopy, atomic force microscopy, scanning electron microscopy, and Kelvin force microscopy. In vitro studies of controlled release of HP were evaluated in simulated intestinal fluid and simulated gastric fluid. The initial adhesion test of E. coli on multilayer films surface showed effective antiadhesive properties. The in vitro antibacterial test indicated that the multilayer films of TMC/HP based on TMC80 can kill the E. coli bacteria. Therefore, antiadhesive and antibacterial multilayer films may have good potential for coatings and surface modification of biomedical applications.

Formulation of Aluminum Chloride Phthalocyanine in Pluronic™ P-123 and F-127 Block Copolymer Micelles: Photophysical properties and Photodynamic Inactivation of Microorganisms

Aluminum Chloride Phthalocyanine (AlPcCl) can be used as a photosensitizer (PS) for Photodynamic Inactivation of Microorganisms (PDI). The AlPcCl showed favorable characteristics for PDI due to high quantum yield of singlet oxygen (ΦΔ) and photostability. Physicochemical properties and photodynamic inactivation of AlPcCl incorporated in polymeric micelles of tri‐block copolymer (P‐123 and F‐127) against microorganisms Staphylococcus aureus, Escherichia coli and Candida albicans were investigated in this work. Previously, it was observed that the AlPcCl undergoes self‐aggregation in F‐127, while in P‐123 the PS is in a monomeric form suitable for PDI. Due to the self‐aggregation of AlPcCl in F‐127, this formulation did not show any effect on these microorganisms. On the other hand, AlPcCl formulated in P‐123 was effective against S. aureus and C. albicans and the death of microorganisms was dependent on the PS concentration and illumination time. Additionally, it was found that the values of PS concentration and illumination time to eradicate 90% of the initial population of microorganisms (IC90 and D90, respectively) were small for the AlPcCl in P‐123, showing the effectiveness of this formulation for PDI.

Properties of Chlorophyll and Derivatives in Homogeneous and Microheterogeneous Systems

Chlorophyll (Mg-Chl) and its derivatives, zinc chlorophyll (Zn-Chl), copper chlorophyll (Cu-Chl), pheophytin (Pheo), pheophorbide (Pheid), and zinc chlorophyllide (Zn-Chld), were studied as to their acid-base equilibrium properties, hydrophobicity, stability, binding, and relative localization in neutral surfactant micellar systems. The stability order of metalochlorophyll (pH(M)) in acidic medium was found to be Cu-Chl > Zn-Chld > Zn-Chl > Mg-Chl. The apparent pK(a) for protonation of porphyrin ring nitrogens was around 1.0 for all derivatives. The pK(a) for protonation of carboxylate phorbide was 5.9 for Pheid and 2.4 for Zn-Chld. This difference was attributed to complexation of carboxylate with zinc. The hydrophobicity of chlorophyll in relation to the ability of partitioning the cell membrane lipid layer was estimated in the octanol/water biphasic system. Pheo, a more hydrophobic molecule, presented the highest partition coefficient (K(P)) in the organic phase, followed by Cu-Chl, Mg-Chl, Zn-Chl, Pheid, and Zn-Chld. The hydrophobic character was the key to relative drug location in the micellar systems. All studied derivatives interacted strongly with Tween 80 micellar systems, and particularly with P-123. For both surfactants, the order followed by binding constant (K(b)) was Zn-Chld > Pheo > Cu-Chl > Mg-Chl > Zn-Chl > Pheid, while binding constants estimated for the Chl containing the phytyl group correlated with K(P). Fluorescence quenching studies have shown that phorbides are located in a less hydrophobic region than the phytyl chain-containing derivatives, which are located preferentially in a deeper micellar microenvironment. Thus, the association of the chlorophylls with specific binding sites of micellar systems is strongly modulated by the presence of phytyl chains and metal coordinated to the porphyrinic ring.

Effects of Metal and the Phytyl Chain on Chlorophyll Derivatives: Physicochemical Evaluation for Photodynamic Inactivation of Microorganisms

Chlorophyll compounds and their derivatives containing metal or phytyl chain can be used as photosensitizer in photodynamic inactivation of microorganisms (PDI). So, the physicochemical properties and antimicrobial effect of chlorophyll derivatives were investigated: Mg‐chlorophyll (Mg‐Chl), Zn‐chlorophyll (Zn‐Chl), Zn‐chlorophyllide (Zn‐Chlde), Cu‐chlorophyll (Cu‐Chl), pheophytin (Pheo) and pheophorbide (Pheid). The photobleaching experiments showed photostability according to Cu‐Chl > Pheo ∼ Pheid ≫ Zn‐Chl ∼ Zn‐Chlde > Mg‐Chl. This order was discussed in terms of metal and the phytyl chain presences. Pheid and Zn‐Chl in aqueous Tween 80 solution exhibited highest singlet oxygen yield compared with the other derivatives. Chlorophyll derivatives (CD) with phytyl chain was limited by the self‐aggregation phenomenon at high concentrations, even in micellar systems (Tween 80 and P‐123). The antimicrobial effect of CD derivatives was investigated against Staphylococcus aureus, Escherichia coli, Candida albicans and Artemia salina. Pheid showed the best results against all organisms tested, Zn‐Chlde was an excellent bactericide in the dark and Cu‐Chl had no PDI effect. No correlation with CD uptake by microorganisms and darkness cytotoxicity was found. The physicochemical properties allied to bioassays results indicate that Mg‐Chl, Pheo, Zn‐Chl and Pheid are good candidates for PDI.

Synthesis and controlled curcumin supramolecular complex release from pH-sensitive modified gum-arabic-based hydrogels

Curcumin (CUR) is a polyphenolic compound including a beta-diketone moiety, which is associated with numerous pharmacological activities, but applications are limited due to its low water solubility. Thus, in this work some inclusion complexes of CUR with alpha-cyclodextrin (α-CD) and beta-cyclodextrin (β-CD) were prepared using different host : guest proportions to improve drug solubilization in biological fluids. The formation of these complexes was confirmed by 1H NMR and thermogravimetric analysis. The stoichiometries of the CUR/α-CD and CUR/β-CD complexes were 1 : 1 and 1 : 2 and the association constants were 344 mol−1 L and 7.2 × 107 mol−2 L2 for α-CD and β-CD, respectively. The major stability of the CUR/β-CD complex is justified by an inclusion of the aromatic ring inside the CD cavity, whilst in the case of α-CD-complexes the interactions occur via H-bridges, showing the latter complexes’ slow exchange on the NMR time-scale. Even so, the solubility of curcumin complexes is clearly controlled by the solubility of CDs, showing the highest solubility for CUR/α-CD complexes. Hydrogels of modified gum arabic containing CUR/α-CD (1 : 4) were obtained and used for controlled release of CUR in simulated intestinal fluid (SIF) and simulated gastric fluid (SGF). The kinetics of release was pH-responsive and the percentage of CUR released was ca. 97% in SIF and 6.7% in SGF. For the toxicity studies on undifferentiated Caco-2 cells, IC50s of 63.4 ± 14.4 μg mL−1 and 85.2 ± 14.9 μg mL−1 for CUR and CUR/α-CD (1 : 4), respectively, were obtained. The toxicity of these samples on differentiated Caco-2 cells was lower than on undifferentiated cells. Additionally, the CUR incorporated into hydrogels showed no toxic effects on differentiated and undifferentiated Caco-2 cells, indicating the pharmaceutical potential of three-dimensional matrices of GAm for controlled release of CUR complexed with cyclodextrin.

Physico-chemical properties of meso-tetrakis(p-methoxyphenyl)porphyrin (TMPP) incorporated into pluronicTM p-123 and f-127 polymeric micelles

The physicochemical properties (solubilization, structural organization and stability) of meso-tetrakis(p-methoxyphenyl)porphyrin (TMPP), a promising photosensitizer for photodynamic therapy, solubilized in polymeric micelles of tri-block copolymers PluronicTM P-123 and F-127, were studied. The formulations obtained by the solid dispersion method led to monomerization of TMPP in these copolymers. Solubility studies showed that P-123 solubilizes double the photosensitizer than F-127. The self-aggregation phenomenon was affected by the [TMPP]/[poloxamer] ratio and medium temperature. The decrease in the temperature of these systems promoted the formation of different kinds of TMPP aggregates intrinsically connected with the structural changes occurring in the micelles.

SPECTROSCOPIC STUDY OF ALUMINUM PHTHALOCYANINE CHLORIDE (AlPcCl) IN HOMOGENEOUS AND MICRO-HETEROGENEOUS MEDIA CONSISTING OF P-123 AND F-127 POLYMERIC MICELLES

Aluminum phthalocyanine chloride (AlPcCl) is a photoactive compound which has been used as a photosensitizer (PS) in photodynamic therapy (PDT). Its spectroscopic properties have been studied in solvents of different polarities (ethanol, acetone, dimethylsulfoxide and chloroform). Its solubility has been found to decrease with increasing solvent polarity, together with full self-aggregation in aqueous solution. The binding of AlPcCl to the copolymer PluronicTM micellar class P-123 and F-127 used as solubilizer/carriers was studied. Greater interaction between the more hydrophobic copolymer P-123 and AlPcCl was observed, besides a complex interaction profile involving different AlPcCl forms (self-aggregate/monomeric form) in the copolymers. Time- and temperature-dependent structural organization of AlPcCl in the copolymers was also observed. Thus, AlPcCl has a strong tendency to self-aggregate with increasing solvent polarity, an effect also observed in micellar media.