Maria E. Cortés

Bioactive glass as a drug delivery system of tetracycline and tetracycline associated with β-cyclodextrin

The aim of this study was to evaluate the physical-chemical properties, in vivo biocompatibility and antimicrobial activity of bioactive glasses (BG) used as a controlled release device for tetracycline hydrochloride and an inclusion complex formed by tetracycline and beta-cyclodextrin at 1:1 molar ratio. The BG as well as their compounds loaded with tetracycline (BT) and tetracycline:beta-cyclodextrin (BTC) were characterized by FTIR spectroscopy, X-ray powder diffraction, differential scanning calorimetry and by scanning electron microscopy and energy dispersive spectroscopy. The in vivo test was carried out with female mice split into three groups treated with bioactive glass either without drugs, or associated with tetracycline, or with tetracycline:beta-cyclodextrin by subcutaneous implantation. The histological examination of tissue at the site of implantation showed moderate inflammatory reactions in all groups after 72 h. The bacterial effect was tested on A. actinomycetemcomitans suspended in BHI broth, with or without bioactive particles. A considerable bacteriostatic activity was found with BT and BTC glasses, as compared to plain glass. The presence of cyclodextrin was important to slow down the release of tetracycline for a long period of time and it was verified that the presence of tetracycline or its inclusion complex, tetracycline:beta-cyclodextrin, did not affect the bioactivity of the glass.

Metal complexes of 2-benzoylpyridine-derived thiosemicarbazones: structural, electrochemical and biological studies

Complexes of 2-benzoylpyridine thiosemicarbazone (H2Bz4DH) as well as of its N(4)-methyl (H2Bz4Me) and N(4)-phenyl (H2Bz4Ph) analogues with iron(II), nickel(II) and zinc(II) were characterized by a variety of spectroscopic techniques. Electrochemical studies revealed that the iron(II) complexes undergo oxidation giving the iron(III) analogues, which could be reduced back by cellular thiols such as thioredoxine, suggesting that this process could occur in biological media. The thiosemicarbazones have antifungal activity against Candida albicans that significantly decreases on coordination. The crystal structure 2-benzoylpyridine-N(4)-methyl thiosemicarbazone (H2Bz4Me) was determined.

The Chlorhexidine: beta;-Cyclodextrin Inclusion Compound: Preparation, Characterization and Microbiological Evaluation

The 1 : 2 chlorhexidine : β-cyclodextrin(Cx : βCD) complex was prepared and characterised using X-ray crystallography, infrared spectroscopy, thermal analysis and nuclearmagnetic resonance. The minimum inhibitory concentration (MIC50) of the chlorhexidine : β-cyclodextrin inclusion compoundagainst Streptococcus mutans, Eubacterium Lentum, Fusobacterium nucleatum, Bacteroides fragilis andActinomices actinomycetemcomitans was determined. TheCx : βCD inclusion compound inhibited the bacterial growth at a low concentration.

Antimicrobial effect of photodynamic therapy in carious lesions in vivo, using culture and real-time PCR methods

BACKGROUND The aim of this study was to evaluate the antimicrobial effect of photodynamic therapy (PDT) in carious lesions in vivo by culture and real-time PCR methods. METHODS Ten teeth with deep active carious lesions were selected and five portions of carious dentin were removed for each tooth. Two increments were used as control, to represent the superficial and deep dentin, respectively. Methylene blue at 100mg/L was placed in contact with the cavity for 5min, before being irradiated with a halogen light source for 1min. Then, after PDT, other three portions were removed. The samples were processed in laboratory and the number of viable cfu was obtained. The real-time PCR analyses were performed in two increments of carious dentin, removed before and after PDT. The Streptococcus mutans DNA was isolated from carious dentin samples and amplification and detection of DNA were performed with real-time PCR. The cavities were then restored with glass-ionomer cement. RESULTS Using conventional culture methods, the results demonstrated that viable bacteria were significantly reduced in all of the agar plates following photosensitization. No difference was found between both groups regarding S. mutans DNA quantification by real-time PCR. CONCLUSION Although PDT may not affect the number of S. mutans DNA copies immediately after the treatment, clear reduction of the number of cfu was found. Despite its promising use for eliminating bacteria in dental caries treatment, further studies are necessary to establish an effective clinical protocol for the PDT.

Electrospun nanofibers of polyCD/PMAA polymers and their potential application as drug delivery system

Herein, we used an electrospinning process to develop highly efficacious and hydrophobic coaxial nanofibers based on poly-cyclodextrin (polyCD) associated with poly(methacrylic acid) (PMAA) that combines polymeric and supramolecular features for modulating the release of the hydrophilic drug, propranolol hydrochloride (PROP). For this purpose, polyCD was synthesized and characterized, and its biocompatibility was assessed using fibroblast cytotoxicity tests. Moreover, the interactions between the guest PROP molecule and both polyCD and βCD were found to be spontaneous. Subsequently, PROP was encapsulated in uniaxial and coaxial polyCD/PMAA nanofibers. A lower PROP burst effect (reduction of approximately 50%) and higher modulation were observed from the coaxial than from the uniaxial fibers. Thus, the coaxial nanofibers could potentially be a useful strategy for developing a controlled release system for hydrophilic molecules.

Propolis varnish: antimicrobial properties against cariogenic bacteria, cytotoxicity, and sustained-release profile.

Varnishes are preparations that differ in the polymeric matrix and therapeutical agents. In dentistry they are used to prevent caries. In this study we developed a propolis varnish, considering propolis properties against cariogenic bacteria. To a chitosan polymeric base (CHV) was added ethanolic propolis extract in different concentrations: PV1 (5%), PV2 (10%), and PV3 (15%). Antimicrobial activity was carried out against Streptococcus mutans (SM), Streptococcus sanguinis (SG), Streptococcus salivarius (SS), and Lactobacillus casei (LC) through agar diffusion method. The three propolis concentrations incorporated were effective in inhibiting the growth of all microorganisms, but without significant difference between the zones of inhibition observed. Cytotoxicity assay was done by MTT method. Data were analyzed by one-way ANOVA and Bonferroni test. None of the varnishes were cytotoxic, keeping 80% of viable cells, while CHV allowed cellular proliferation (120%). Sustained-release test was carried out by applying 40 μL of each varnish in the buccal surface of bovine teeth and kept in an ethanol/water solution removed in regular times. According to the “independent model approach,” the release profiles were distinct from each varnish and the most prolonged was PV3 (8 weeks). Varnish formulations had satisfactory antimicrobial activity against cariogenic bacteria and have a low cytotoxicity (<50%).

Evaluation of the substantivity of chlorhexidine in association with sodium fluoride in vitro.

The efficacy of the fluoride-chlorhexidine association in the prevention of gingivitis and caries has been advocated for a number of years. The objective of the association of these therapeutic agents is a synergistic action. The aim of the present study was to determine the substantivity of chlorhexidine associated or not to sodium fluoride at different intervals of time, in vitro. Bovine enamel surfaces were treated with 0.12% chlorhexidine gluconate (Periogard--Colgate) or 0.05% sodium fluoride with 0.12% chlorhexidine (Duplak--Dentsply) solutions for one minute. Fragments were placed in distilled water and samples were collected at intervals of 5, 30 and 360 minutes and analyzed by spectrophotometry in the visible ultraviolet region. Substantivity was evaluated by the measurement of chlorhexidine desorption from the treated slabs. The mean values obtained were statistically analyzed by Students t-test. The results showed that the concentration of chlorhexidine decreased when it was used in association with sodium fluoride. The difference between the groups was statistically significant (p < 0.05). These in vitro results suggest that the association between sodium fluoride and chlorhexidine in the studied concentrations appears to have no beneficial effect because of the decrease in the substantivity of chlorhexidine.

Development of Sulfadiazine-Decorated PLGA Nanoparticles Loaded with 5-Fluorouracil and Cell Viability

The aim of this work was to synthesize sulfadiazine-poly(lactide-co-glycolide) (SUL-PLGA) nanoparticles (NPs) for the efficient delivery of 5-fluorouracil to cancer cells. The SUL-PLGA conjugation was assessed using FTIR, 1H-NMR, 13C-NMR, elemental analysis and TG and DTA analysis. The SUL-PLGA NPs were characterized using transmission and scanning electron microscopy and dynamic light scattering. Additionally, the zeta potential, drug content, and in vitro 5-FU release were evaluated. We found that for the SUL-PLGA NPs, Dh = 114.0 nm, ZP = −32.1 mV and the encapsulation efficiency was 49%. The 5-FU was released for up to 7 days from the NPs. Cytotoxicity evaluations of 5-FU-loaded NPs (5-FU-SUL-PLGA and 5-FU-PLGA) on two cancer cell lines (Caco-2, A431) and two normal cell lines (fibroblast, osteoblast) were compared. Higher cytotoxicity of 5-FU-SUL-PLGA NPs were found to both cancer cell lines when compared to normal cell lines, demonstrating that the presence of SUL could significantly enhance the cytotoxicity of the 5-FU-SUL-PLGA NPs when compared with 5-FU-PLGA NPs. Thus, the development of 5-FU-SUL-PLGA NPs to cancer cells is a promising strategy for the 5-FU antitumor formulation in the future.

PLGA nanofibers improves the antitumoral effect of daunorubicin.

The objective of this study was to evaluate the in vivo anti-inflammatory angiogenesis activity and in vitro cytotoxicity on normal and cancer cell models of a drug delivery system consisting of poly(lactic-co-glycolic acid) nanofibers loaded with daunorubicin (PLGA-DNR) that were fabricated using an electrospinning process. The PLGA-DNR nanofibers were also characterized by thermogravimetric analysis (TGA), differential thermal analysis (DTA) and differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and confocal fluorescence microscopy. In vitro release of DNR from the nanofibers and its corresponding mechanism were also evaluated. Sixty-five percent of the DNR was released in an initial burst over 8h, and by 1224 h, eighty-five percent of the DNR had been released. The Higuchi model yielded the best fit to the DNR release profile over the first 8h, and the corresponding data from 24 to 1224 h could be modeled using zero-order kinetics. The PLGA-DNR nanofibers exhibited a higher cytotoxicity to A431 cells than free DNR but a cytotoxicity similar to free DNR against fibroblast cells. A higher antiangiogenic effect of PLGA nanofibers was observed in the in vivo data when compared to free DNR, and no inflammatory potential was observed for the nanofibers.

Structural and thermodynamic characterization of doxycycline/β-cyclodextrin supramolecular complex and its bacterial membrane interactions.

Doxycycline is a semi-synthetic antibiotic commonly used for the treatment of many aerobic and anaerobic bacteria. It inhibits the activity of matrix metalloproteinases (MMPs) and affects cell proliferation. In this study, the structural and thermodynamic parameters of free DOX and a DOX/βCD complex were investigated, as well as their interactions and effects on Staphylococcus aureus cells and cellular cytotoxicity. Complexation of DOX and βCD was confirmed to be an enthalpy- and entropy-driven process, and a low equilibrium constant was obtained. Treatment of S. aureus with higher concentrations of DOX or DOX/βCD resulted in an exponential decrease in S. aureus cell size, as well as a gradual neutralization of zeta potential. These thermodynamic profiles suggest that ion-pairing and hydrogen bonding interactions occur between DOX and the membrane of S. aureus. In addition, the adhesion of βCD to the cell membrane via hydrogen bonding is hypothesized to mediate a synergistic effect which accounts for the higher activity of DOX/βCD against S. aureus compared to pure DOX. Lower cytotoxicity and induction of osteoblast proliferation was also associated with DOX/βCD compared with free DOX. These promising findings demonstrate the potential for DOX/βCD to mediate antimicrobial activity at lower concentrations, and provides a strategy for the development of other antimicrobial formulations.