Synthesis and Characterization of Cassava Gum Hydrogel Associated with Chlorhexidine and Evaluation of Release and Antimicrobial Activity.

Hydrogels from natural sources are attracting increasing interest due to their ability to protect biologically active molecules. Starch extracted from cassava tubers is a promising material for synthesizing these hydrogels. Copolymerization of cassava gum and incorporation of chlorhexidine digluconate (CLX) into the hydrogels is confirmed by changes in the crystallographic profile, as observed through X-ray diffraction, and a shift in the 1000 cm-1 band in the Fourier-transform infrared spectroscopy spectrum. The differential scanning calorimetry reveals changes in the decomposition temperature of the synthesized hydrogels related to CLX volatility. Micrographs illustrate the material's porosity. Release tests indicate a constant linear release over 72 h, while antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans is satisfactory, with 100% effectiveness from 0.5% CLX and the formation of inhibition halos. Toxicity and biocompatibility studies show no cytotoxicity. The continuous release of chlorhexidine is promising for components of biomedical implants and applications as it can ensure antimicrobial action according to specific therapeutic needs.

Development of an Experimental Dentifrice with Hydroxyapatite Nanoparticles and High Fluoride Concentration to Manage Root Dentin Demineralization.

BACKGROUND: High-fluoride dentifrice is used to manage root caries, but there is no evidence whether its association with nanohydroxyapatite could provide an additional protection for root caries. Therefore, this study aimed to develop and evaluate the effect of an experimental dentifrice with high fluoride (F-) concentration and nanohydroxyapatite (nano-HA) on root dentin demineralization. MATERIALS AND METHODS: After formulation of dentifrices, root dentin specimens were randomly assigned to six groups (n = 10) using different dentifrice treatments: placebo; nano-HA without F-; 1,100 µg F-/g; 1,100 µg F-/g + nano-HA; 5,000 µg F-/g; and 5,000 µg F-/g + nano-HA. A pH cycling model was performed for 10 days, in which treatments were performed twice a day. After that period, the longitudinal hardness was evaluated and the area of demineralization (ΔS) was calculated. The formulated dentifrices were evaluated for primary stability, cytotoxicity, and other technical parameters. Two-way ANOVA and Tukey's test with p set at 5% were used for data analysis. RESULTS: The experimental dentifrices were stable and had no cytotoxicity. Regarding dentin demineralization, the placebo group significantly increased ΔS compared to all other treatment groups (p<0.001). The dentifrices containing 5,000 µg F-/g, regardless of the presence of nano-HA, led to a smaller lesion area in relation to the other treatments (p<0.001). CONCLUSION: The findings of this study suggest that nano-HA reduced dentin demineralization, and dentifrice with 5,000 µg F-/g dentifrices, regardless of the presence of nano-HA, showed a greater reduction in root dentin demineralization.

Solvent-free production of phthalated cashew gum for green synthesis of antimicrobial silver nanoparticles.

This work describes a solvent-free method for the chemical modification of cashew gum (Anacardium occidentale L.) using phthalic anhydride in different proportions with different reaction times. Four biopolymers were synthesized and characterized by FTIR, NMR, and elemental analysis. A computational chemistry study was conducted to understand better the reaction. Phthalated cashew gum was used in preparation of silver nanoparticles (AgNPs) by a conventional route, using sodium borohydride (NaBH4) as reducing agent, and for green route. AgNPs were evaluated for antimicrobial activity and characterized by UV-Vis spectroscopy, FTIR, nanoparticle tracking analysis, Zeta Potential analysis, and atomic force microscopy. AgNPs produced by the green route had an average size of 51.9 nm and Zeta Potential of -55.8 mV, and AgNPs produced by the conventional method had an average size of 47.7 nm and Zeta Potential of -39.3 mV. AgNPs synthesized using phthalated cashew gum showed antimicrobial activity against Staphylococcus aureus and Escherichia coli.

Development of a low-cost electrochemical sensor based on babassu mesocarp (Orbignya phalerata) immobilized on a flexible gold electrode for applications in sensors for 5-fluorouracil chemotherapeutics.

There are increasing concerns regarding the risks arising from the contamination of manipulators of antineoplastic drugs promoted by occupational exposure or even in the dosage of drugs. The present work proposes the use of an electrochemical sensor based on a biopolymer extracted from the babassu coconut (Orbignya phalerata) for the determination of an antineoplastic 5-fluorouracil (5-FU) drug as an alternative for the monitoring of these drugs. In order to reduce the cost of this sensor, a flexible gold electrode (FEAu) is proposed. The surface modification of FEAu was performed with the deposition of a casting film of the biopolymer extracted from the babassu mesocarp (BM) and modified with phthalic anhydride (BMPA). The electrochemical activity of the modified electrode was characterized by cyclic voltammetry (CV), and its morphology was observed by atomic force microscopy (AFM). The FEAu/BMPA showed a high sensitivity (8.8 µA/µmol/L) and low limit of detection (0.34 µmol/L) for the 5-FU drug in an acid medium. Electrochemical sensors developed from the babassu mesocarp may be a viable alternative for the monitoring of the 5-FU antineoplastic in pharmaceutical formulations, because in addition to being sensitive to this drug, they are constructed of a natural polymer, renewable, and abundant in nature. Graphical abstract ᅟ.

Modified chitosan-based bioactive material for antimicrobial application: Synthesis and characterization.

The search for natural antibacterial agents to treat diseases caused by resistant microorganisms has been gaining increasing attention. Chitosan has been studied in several areas due to its particular properties. The grafting of hydrophobic chains into the chitosan molecule, turning it amphiphilic, may improve its antimicrobial activity by increasing electrostatic interaction with the bacterial cell wall. The objective of this work was to enhance the antimicrobial activity of chitosan by the reaction of N-acylation with maleic anhydride. For this purpose, molar ratios of 1:2, 1:5 and 1:10 chitosan: anhydride were investigated, and the obtained derivatives were characterized by elemental analysis, FTIR, thermal analysis and XRD where it was possible to prove the chemical modification of chitosan. The modified materials presented excellent antibacterial action against Staphylococcus aureus and Escherichia coli, evidencing no activity against the protozoan Leishmania amazonensis. Cytotoxicity assays by the MTT analysis and hemolysis indicated that the derivatives did not show toxicity in mammalian cells. The proposed modified chitosan compounds showed to be promising for biomedical applications since they allied excellent antibacterial activity and absence of cytotoxicity.

Modifying cellulose with metaphosphoric acid and its efficiency in removing brilliant green dye.

In this study, cellulose was chemically modified through the addition of the phosphorylating agent, metaphosphoric acid in order to obtain a new material (MPCel) with higher adsorptive properties than the starting material. Both materials were characterized by infrared spectroscopy, X-ray diffraction, solid-state phosphorus-31 nuclear magnetic resonance spectroscopy and thermogravimetric analysis. Maximal adsorption capacity, at 45°C for pure cellulose, was 90.5mgg-1, at pH=10 and contact time of 40min, with experimental isotherms better adjusted to the Langmuir model. MPCel at the same temperature conditions showed contact time of 10min, pH=10, and maximal adsorption capacity of 150.0mgg-1, being better adjusted to the Temkin model. The kinetic study of both materials followed the pseudo-second-order model. Modification successfully occurred and both adsorbents were shown able to be capable of removing the brilliant green dye, but MPCel was more efficient for purpose, when compared to the pure cellulose.

Potential of Cellulose Functionalized with Carboxylic Acid as Biosorbent for the Removal of Cationic Dyes in Aqueous Solution.

In the last decade, adsorption has been used to minimize the pollution caused by dyes, which represents a serious environmental problem. In this context, this work reports the preparation of phthalic anhydride-modified cellulose (PhCel), through the reaction of cellulose (Cel) with phthalic anhydride (Ph). The efficiency of the reaction was observed by elemental analysis, Fourier Transform Infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and thermogravimetry/derivative thermogravimetry (TG/DTG). The adsorbent matrix (Cel and PhCel) was used in the removal of crystal violet (CV) and methylene blue (MB) dyes in aqueous medium. In the kinetic study, the experimental data obtained had the best fit to the pseudo-first-order model. In general, the isotherms obtained at different temperatures had a best fit to the model proposed by Langmuir, and the CV and MB adsorption process in adsorbent matrixes can be favored strictly by hydrogen bonds and/or electrostatic interactions for Cel and electrostatic interactions for PhCel.

Chitosan Hydrogel in combination with Nerolidol for healing wounds.

Chitosan is a natural polymer with antibacterial property, that is biodegradable, extremely abundant and non-toxic. This study aimed to develop and characterize chitosan hydrogels in combination with nerolidol, in order to optimize the antimicrobial and healing properties. The hydrogels were prepared using a reaction of the chitosan with acetic acid solution, followed by the addition of 2 or 4% of the nerolidol. Using thermogravimetry, differential scanning calorimetry and infrared spectroscopy, the incorporation of nerolidol in the hydrogel was confirmed. Direct contact tests using hydrogels and Staphylococcus aureus showed a synergistic effect in the materials, enabling total inhibition of bacterial growth. The hydrogel containing 2% nerolidol showed excellent healing effects. The beginning of re-epithelialization and reorganization of collagen was already observed on the 7th day of treatment. The material created proofed to be promising as a healing and antibacterial agent.

The systems containing clays and clay minerals from modified drug release: a review.

Clays are materials commonly used in the pharmaceutical industry, either as ingredients or as active ingredients. It was observed that when they are administered concurrently, they may interact with drugs reducing their absorption. Therefore, such interactions can be used to achieve technological and biopharmaceutical advantages, regarding the control of release. This review summarizes bibliographic (articles) and technological (patents) information on the use of systems containing clays and clay minerals in modified drug delivery. In this area, formulations such natural clay, commercial clay, synthetic clay, composites clay-polymers, nanocomposites clay-polymers, films and hidrogels composites clay-polymers are used to slow/extend or vectorize the release of drugs and consequently they increase their bioavailability. Finally, this review summarizes the fields of technology and biopharmaceutical applications, where clays are applied.