Study of the antibacterial and cytotoxic activity of chitosan and its derivatives chemically modified with phthalic anhydride and ethylenediamine.

The insertion of hydrophobic and hydrophilic chains in the chitosan molecule can improve its antibacterial activity, expanding its range of application in several areas of medical-pharmaceutical sciences. Thus, this work aimed to increase the antibacterial activity of chitosan through the modification reaction with phthalic anhydride (QF) and subsequent reaction with ethylenediamine (QFE). The chitosan and derivatives obtained were characterized by elemental analysis, 13C Nuclear Magnetic Resonance (13C NMR), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TG), where it was possible to prove the chemical modification. Both materials showed a greater antibacterial inhibitory effect against Gram-positive bacteria, Staphylococcus aureus, emphasizing antibacterial activity against Gram-negative bacteria, Escherichia coli, with values above 70 % of the inhibitory effect, which is a promising result. Assays with human fibroblast cells by the [3-(4,5-dimethylthiazolyl)-2,5-diphenyl tetrazolium (MTT)] bromide reduction test did not indicate toxicity in the materials. Thus, the derived materials showed promise for biomedical applications since they combined excellent antibacterial activity against gram-positive and gram-negative strains and did not show cytotoxicity.

Use of Cactus Pear Meal in the Feeding of Laying Hens in Semi-Intensive System.

Little information is available in the literature on the use of cactus pear meal (CPM) in poultry diets; therefore, it is important to evaluate diets that provide excellent performance and lower production costs. Our objective was to study the use of Miúda CPM in the diets of laying hens. In the first study, two diets for male and female chicks were used-1: 80% reference diet + 20% Miúda cactus pear meal (CPM) and 2: 80% reference diet + 20% Gigante cactus pear meal (CPM). The variety Miúda provided a better use of metabolizable energy, as well as a greater digestibility coefficient of dry matter, protein, and mineral matter. In the second study, a control diet was compared to three diets with different levels of Miúda CPM for laying hens in the proportions of 3%, 6%, and 9%. No significant differences were found in productive performance. However, there were significant differences in the some parameters egg quality, texture and color profile of the cooked yolk, egg composition, fatty acids and cholesterol in the yolk. It is possible to use 9% Miúda CPM in the diet of laying hens in a semi-intensive system that does not compromise performance and egg quality, and using 3% Miúda CPM provides a higher economic return.

Development of a New Clay-Based Aerogel Composite from Ball Clay from Piauí, Brazil and Polysaccharides.

The incorporation of polymeric components into aerogels based on clay produces a significant improvement in the physical and thermal properties of the aerogels. In this study, clay-based aerogels were produced from a ball clay by incorporation of angico gum and sodium alginate using a simple, ecologically acceptable mixing method and freeze-drying. The compression test showed a low density of spongy material. In addition, both the compressive strength and the Young's modulus of elasticity of the aerogels showed a progression associated to the decrease in pH. The microstructural characteristics of the aerogels were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The chemical structure was studied by infrared spectroscopy with Fourier transform (FTIR). The TGA curves from a non-oxidizing atmosphere indicated that the clay had a mass loss of 9% above 500 °C and that due to the presence of polysaccharides, the aerogels presented a decomposition of 20% at temperatures above 260 °C. The DSC curves of the aerogels demonstrated a displacement in higher temperatures. In conclusion, the results showed that aerogels of ball clay with the incorporation of polysaccharides, which are still minimally studied, have potential application as thermal insulation considering the mechanical and thermal results obtained.

Development of a new biomaterial based on cashew tree gum (Anarcadium occidentale L.) enriched with hydroxyapatite and evaluation of cytotoxicity in adipose-derived stem cell cultures.

Cashew tree gum is a polysaccharide material highly available in the Northeast region of Brazil. It has been explored for biocompatibility with human tissues. This research aimed to describe the synthesis and characterization of cashew gum/hydroxyapatite scaffold and evaluate the possible cytotoxicity in murine adipose-derived stem cells (ADSCs) cultures. ADSCs of the subcutaneous fat tissue of Wistar rats were collected, isolated, expanded, differentiated into three strains, and characterized immunophenotypically. The scaffolds were synthesized through chemical precipitation, lyophilized and characterized through scanning electron microscopy (SEM), infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermal analysis (TG and DTG), and mechanical testing. The scaffold presented a crystalline structure and pores with an average diameter of 94.45 ± 50.57 µm. By mechanical tests, the compressive force and modulus of elasticity were like the cancellous bone. The isolated adipose-derived stem cells (ADSCs) presented fibroblast morphology, adhesion capacity to plastic, differentiation in osteogenic, adipogenic and chondrogenic lineages, positive expression for the CD105 and CD90 markers and negative expression for the CD45 and CD14 markers. The MTT test showed increased cell viability, and the biomaterial showed a high level of hemocompatibility (<5 %). This study allowed the development of a new scaffold for future surgical applicability in tissue regeneration.

Insulin-loaded nanoparticles based on acetylated cashew gum/chitosan complexes for oral administration and diabetes treatment.

Insulin is one of the most important drugs in the clinical treatment of diabetes. There is growing interest in oral insulin administration as it mimics the physiological pathway and potentially reduces side effects associated with subcutaneous injection. In this study, a nanoparticulate system was developed using acetylated cashew gum (ACG) and chitosan by the polyelectrolyte complexation method, for oral administration of insulin. The nanoparticles were characterized by size, zeta potential and encapsulation efficiency (EE%). And they had a particle size of 460 ± 11.0 nm, PDI of 0.2 ± 0.021, zeta potential of 30.6 ± 0.48 mV, and an EE% of 52.5 %. Cytotoxicity assays were performed for HT-29 cell lines. It was observed that ACG and nanoparticles did not have a significant effect on cell viability, verifying their biocompatibility. Hypoglycemic effects of the formulation were analyzed in vivo, noting that the nanoparticles reduced blood glucose by 51.0 % of baseline levels after 12 h, not inducing signs of toxicity or death. Biochemical and hematological profiles were not clinically modified. Histological study indicated no signs of toxicity. Results showed that the nanostructured system presented itself as a potential vehicle for oral insulin release.

Organic-Inorganic Hybrid Pigments Based on Bentonite: Strategies to Stabilize the Quinoidal Base Form of Anthocyanin.

Anthocyanins are one of the natural pigments that humanity has employed the most and can substitute synthetic food dyes, which are considered toxic. They are responsible for most purple, blue, and red pigment nuances in tubers, fruits, and flowers. However, they have some limitations in light, pH, oxygen, and temperature conditions. Combining biomolecules and inorganic materials such as clay minerals can help to reverse these limitations. The present work aims to produce materials obtained using cetyltrimethylammonium bromide in bentonite clay for incorporation and photostabilization of anthocyanin dye. Characterizations showed that the organic molecules were intercalated between the clay mineral layers, and the dye was successfully incorporated at a different pH. Visible light-driven photostability tests were performed with 200 h of irradiation, confirming that the organic-inorganic matrices were efficient enough to stabilize the quinoidal base form of anthocyanin. The pigment prepared at pH 10 was three-fold more stable than pH 4, showing that the increase in the synthesis pH promotes more stable colors, probably due to the stronger intermolecular interaction obtained under these conditions. Therefore, organobentonite hybrids allow to stabilize the fragile color coming from the quinoidal base form of anthocyanin dyes.

Hydrogel Based on Nanoclay and Gelatin Methacrylate Polymeric Matrix as a Potential Osteogenic Application.

A nanocomposite hydrogel has potentially applicability in the induction of osteogenesis. The hydrogel was synthesized using 1% gelatin methacrylate (GelMA), a biodegradable and bioactive polymer containing the structure of gelatin, denatured collagen derived from the extracellular bone matrix, and 6% laponite (Lap), a synthetic phyllosilicate of nanosized particles. Initially, 0.6 g of Lap was added to deionized water, and then a solution of GelMA/Igarcure was added under stirring and UV light for crosslinking. The spectra in the Fourier-transform infrared region showed bands that indicate the interaction between gelatin and methacrylate anhydride. X-ray diffraction patterns confirmed the presence of Lap and GelMA in the hydrogel. The thermogravimetric analysis suggested an increase in the thermal stability of the hydrogel with the presence of clay mineral. Rheological analysis showed that the hydrogel had a viscosity that allowed its injectability. The hydrogel did not show acute toxicity at any of the concentrations tested according to the Artemia salina lethality test. It showed cell viability more significant than 80% in the MTT test, which makes it suitable for in vivo osteogenic induction tests. The cell differentiation test showed the differentiation of stem cells into osteogenic cells. It indicates a material with the potential for osteogenic induction and possible application in bone tissue engineering.

pH-responsive phthalate cashew gum nanoparticles for improving drugs delivery and anti-Trypanosoma cruzi efficacy.

Nanotechnology is a crucial technology in recent years has resulted in new and creative applications of nanomedicine. Polymeric nanoparticles have increasing demands in pharmaceutical applications and require high reproducibility, homogeneity, and control over their properties. Work explores the use of cashew phthalate gum (PCG) as a particle-forming polymer. PCG exhibited a pH-sensitive behavior due to the of acid groups on its chains, and control drug release. We report the development of nanoparticles carrying benznidazole. Formulations were characterized by DLS, encapsulation efficiency, drug loading, FTIR, pH-responsive behavior, release, and in vitro kinetics. Interaction between polymer and drug was an evaluated by molecular dynamics. Morphology was observed by SEM, and in vitro cytotoxicity by MTT assay. Trypanocidal effect for epimastigote and trypomastigote forms was also evaluated. NPs responded to the slightly basic pH, triggering the release of BNZ. In acidic medium, they presented small size, spherical shape, and good stability. It was indicated NP with enhanced biological activity, reduced cytotoxicity, high anti T. cruzi performance, and pH-sensitive release. This work investigated properties related to the development and enhancement of nanoparticles. PCG has specific physicochemical properties that make it a promising alternative to drug delivery, however, there are still challenges to be overcome.

Modification of chicha gum: Antibacterial activity, ex vivo mucoadhesion, antioxidant activity and cellular viability.

The aim of the present work was to modify the exuded gum of Sterculia striata tree by an amination reaction. The viscosity and zero potential of the chicha gum varied as a function of pH. The modification was confirmed by X-ray diffraction (XRD), infrared spectroscopy (FTIR), size exclusion chromatography (SEC), zeta potential, thermogravimetric analysis (TG), and differential scanning calorimetry (DSC). Furthermore, the chemical modification changed the molar mass and surface charge of the chicha gum. In addition, the gums were used in tests for ex vivo mucoadhesion strength, antibacterial activity against the standard strain of Staphylococcus aureus (ATCC 25923), inhibitory activity of α-glucosidase, antioxidant capacity, and viability of Caco-2 cells. Through these tests, it was found that amination caused an increase in the mucoadhesive and inhibitory activity of chicha gum against the bacterium Staphylococcus aureus. In addition, the gums (pure and modified) showed antioxidant capacity and an inhibitory effect against the α-glucosidase enzyme and did not show cytotoxic potential.

Biochar Obtained from Caryocar brasiliense Endocarp for Removal of Dyes from the Aqueous Medium.

Given the increase in environmental pollution, especially of water, the emergence of studies that seek to develop strategies to mitigate/treat such effects have gained prominence in the world scientific community. Among the numerous adsorption processes, those made from biochar production stand out. This study analyzed the adsorption properties of the blue methylene model dye in the aqueous solution of biochar and activated biochar developed from pequi (Caryocar brasiliense) endocarp. The biochar was characterized, before and after adsorption, by infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffractometry (XRD), and thermogravimetric analysis (TG). The surface load of the materials was performed by the point of zero charge (pHPZC) method. The study also included analyses of contact time parameters and adsorbed concentration in the adsorption process. Morphological analysis showed that a more significant and profound number of fissures and pores appeared in the activated biochar compared to the biochar. Residual mass analysis evidenced that biochar lost about 15% more mass than the activated biochar, indicating that activation occurred satisfactorily. The adsorption process was well adjusted by pseudo-second-order kinetics and Langmuir's isothermal model. The activated biochar achieved an excellent adsorption capacity of 476.19 mg.g-1, thus demonstrating to be a sound system for removing dyes from an aqueous medium.

Amino-Functionalized Titanate Nanotubes: pH and Kinetic Study of a Promising Adsorbent for Acid Dye in Aqueous Solution.

This work reports the functionalization of sodium titanate nanotubes with amine groups obtained from the reaction of titanate nanotubes with [3-(2-Aminoethylamino)propyl]trimethoxysilane, NaTiNT-2NH, and 3-[2-(2-Aminoethylamino)ethylamino]propyltrimethoxysilane, NaTiNT-3NH. It was verified that the crystalline and morphological structures of NaTiNT were preserved after the functionalization, spectroscopies showed that aminosilane interacted covalently with the surface of NaTiNT, and the incorporation of the aminosilane groups on the surface of NaTiNT can be confirmed. The adsorbent matrices NaTiNT-2NH and NaTiNT-3NH were used to remove the anionic dye from remazol blue R (RB) in aqueous medium, and the highest adsorption capacity was around 365.84 mg g-1 (NaTiNT-2NH) and 440.70 mg g-1 (NaTiNT-3NH) in the range of pH 5.0 to 10.0 and the equilibrium time was reached in 210 min (NaTiNT-2NH) and 270 min (NaTiNT-3NH). Furthermore, the Elovich model, which reports the adsorption in heterogeneous sites and with different activation energies in the chemisorption process, was the most appropriate to describe the adsorption kinetics. Thus, these adsorbent matrices can be used as an alternative potential for dye removal RB in aqueous solution.

Antiulcerogenic and Antibacterial Effects of Chitosan Derivatives on Experimental Gastric Ulcers in Rats.

Gastric ulcer is an injury that develops on the lining of the stomach due to an imbalance between aggressive and defensive agents. Chitosan derivatives demonstrate promising biological activities in accelerating the healing activity of gastric lesions. Thus, this study aimed at investigating the healing activity of gastric lesion, induced by acetic acid (80%), of the chitosan derivative with acetylacetone (Cac) modified with ethylenediamine (Cacen) or diethylenetriamine (Cacdien). The biological activity was determined based on cytotoxicity, antibacterial activity, and gastroprotective activities. The results showed no significant difference in the cytotoxicity, a better antibacterial activity against S. aureus and E. coli, and a positive result on the healing of gastric lesions of the materials (Cac 18.4%, Cacen 55.2%, and Cacdien 68.1%) compared to pure chitosan (50.7%). Therefore, the results indicate that derivatives of chitosan are promising biomaterials for application in the control of lesions on the gastric mucosa.

Polyurethane/Vermiculite Foam Composite as Sustainable Material for Vertical Flame Retardant.

Rigid polyurethane foams were prepared by the one-step expandable foam method using casting molding followed by forming clay-based composites. Polyurethane/vermiculite foam composites (PU/VMT) were controlled based on adding the percentage of clay in the formulation. The effects of composite modifications were evaluated by X-ray diffraction (XRD), thermogravimetric analysis (TG/DTG), and scanning electron microscopy (SEM/EDS) applied to the flame retardancy explored by the vertical burn test. The results indicated that adding clay controlled the particle size concerning polyurethane (PU) foams. However, they exhibited spherical structures with closed cells with relatively uniform distribution. XRD analysis showed the peaks defined at 2θ = 18° and 2θ = 73° relative to the crystallinity in formation and interaction of rigid segments were identified, as well as the influence of crystallinity reduction in composites. In the flame test, the flame retardant surface was successful in all composites, given the success of the dispersibility and planar orientation of the clay layers and the existence of an ideal content of vermiculite (VMT) incorporated in the foam matrix.

Application of Water Hyacinth Biomass (Eichhornia crassipes) as an Adsorbent for Methylene Blue Dye from Aqueous Medium: Kinetic and Isothermal Study.

Water pollution has generated the need to develop technologies to remove industrial pollutants. Adsorption has been recognized as one of the most effective techniques for effluent remediation. In this study, parts (stem and leaves) of a problematic aquatic weed, the water hyacinth (Eichhornia crassipes), were separated to produce a bioadsorbent. The objective was to evaluate the adsorption of a cationic dye, methylene blue (MB), in an aqueous solution of the biomass from different parts of the water hyacinth (Eichhornia crassipes) plants. The materials were characterized through techniques of infrared spectroscopy, scanning electron microscopy, X-ray diffractometry, and thermogravimetric analysis, before and after the material adsorption. Water hyacinth biomasses presented adsorption capacity above 89%, and the kinetics was faster for stem biomass. The kinetic study found that the adsorption process is better described by the pseudo-second-order model, and the adjustments of the isotherm experimental data indicated that both materials are favorable for adsorption. Therefore, water hyacinth bioadsorbent represents a renewable resource with potential for effluent treatment.

TiO2/Karaya Composite for Photoinactivation of Bacteria.

TiO2/Karaya composite was synthesized by the sol-gel method for the photoinactivation of pathogens. This is the first time that we have reported this composite for an antimicrobial approach. The structure, morphology, and optical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-rays (EDS), Fourier transform infrared spectroscopy (FTIR), and diffuse reflectance, and the surface area was characterized by the BET method. The XRD and EDS results showed that the TiO2/Karaya composite was successfully stabilized by the crystal structure and pore diameter distribution, indicating a composite of mesoporous nature. Furthermore, antibacterial experiments showed that the TiO2/Karaya composite under light was able to photoinactivate bacteria. Therefore, the composite is a promising candidate for inhibiting the growth of bacteria.

Magnetic-responsive polysaccharide hydrogels as smart biomaterials: Synthesis, properties, and biomedical applications.

This review reports recent advances in polysaccharide-based magnetic hydrogels as smart platforms for different biomedical applications. These hydrogels have proved to be excellent, viable, eco-friendly alternative materials for the biomedical field due to their biocompatibility, biodegradability, and possibility of controlling delivery processes via modulation of the remote magnetic field. We first present their main synthesis methods and compare their advantages and disadvantages. Next, the synergic properties of hydrogels prepared with polysaccharides and magnetic nanoparticles (MNPs) are discussed. Finally, we describe the main contributions of polysaccharide-based magnetic hydrogels in the targeted drug delivery, tissue regeneration, and hyperthermia therapy fields. Overall, this review aims to motivate the synthesis of novel composite biomaterials, based on the combination of magnetic nanoparticles and natural polysaccharides, to overcome challenges that still exist in the treatment of several diseases.

Nanocomposite Hydrogel Produced from PEGDA and Laponite for Bone Regeneration.

Herein, a nanocomposite hydrogel was produced using laponite and polyethylene-glycol diacrylate (PEGDA), with or without Irgacure (IG), for application in bone tissue regeneration. The nanocomposites were characterized by X-ray diffraction (XRD), Fourier-Transform infrared spectroscopy (FTIR), and thermal analysis (TG/DTG). The XRD results showed that the crystallographic structure of laponite was preserved in the nanocomposite hydrogels after the incorporation of PEGDA and IG. The FTIR results indicated that PEGDA polymer chains were entangled on laponite in hydrogels. The TG/DTG found that the presence of laponite (Lap) improved the thermal stability of nanocomposite hydrogel. The toxicity tests by Artemia salina indicated that the nanocomposite hydrogels were not toxic, because the amount of live nauplii was 80.0%. In addition, in vivo tests demonstrated that the hydrogels had the ability to regenerate bone in a bone defect model of the tibiae of osteopenic rats. For the nanocomposite hydrogel (PEGDA + Lap nanocomposites + UV light), the formation of intramembranous bone in the soft callus was more intense in 66.7% of the animals. Thus, the results presented in this study evidence that nanocomposite hydrogels obtained from laponite and PEGDA have the potential for use in bone regeneration.

Potential Wound Healing Effect of Gel Based on Chicha Gum, Chitosan, and Mauritia flexuosa Oil.

Wounds are considered a clinically critical issue, and effective treatment will decrease complications, prevent chronic wound formation, and allow rapid healing. The development of products based on naturally occurring materials is an efficient approach to wound healing. Natural polysaccharides can mimic the extracellular matrix and promote cell growth, thus making them attractive for wound healing. In this context, the aim of this work was to produce a gel based on chicha gum, chitosan, and Mauritia flexuosa oil (CGCHO) for wound treatment. TG and DTG analyzed the thermal behavior of the materials, and SEM investigated the surface roughness. The percentages of total phenolic compounds, flavonoids, and antioxidants were determined, presenting a value of 81.811 ± 7.257 µmol gallic acid/g Mauritia flexuosa oil, 57.915 ± 0.305 µmol quercetin/g Mauritia flexuosa oil, and 0.379 mg/mL, respectively. The anti-inflammatory was determined, presenting a value of 10.35 ± 1.46% chicha gum, 16.86 ± 1.00% Mauritia flexuosa oil, 10.17 ± 1.05% CGCHO, and 15.53 ± 0.65% chitosan, respectively. The materials were tested against Gram-negative (Klebsiella pneumoniae) and Gram-positive (Staphylococcus aureus) bacteria and a fungus (Candida albicans). The CGCHO formulation showed better antimicrobial activity against Gram-positive bacteria. In addition, an in vivo wound healing study was also performed. After 21 days of treatment, the epidermal re-epithelialization process was observed. CGCHO showed good thermal stability and roughness that can help in cell growth and promote the tissue healing process. In addition to the good results observed for the antimicrobial, antioxidant, anti-inflammatory activities and providing wound healing, they provided the necessary support for the healing process, thus representing a new approach to the wound healing process.

Clays as Vehicles for Drug Photostability.

Clay minerals are often used due to their high adsorption capacity, which has sparked interest in their biological applications to stabilize drugs and pharmaceutical products. This research aims to summarize information about the stability of drugs, cosmetics, dermocosmetics, and pharmaceutical compounds incorporated in the structure of different clay minerals. The databases used to search the articles were Web of Science, Scopus, PubMed, and Science Direct. Photostabilization of these compounds is reviewed and its importance demonstrated. For biological applications, the increase in solubility and bioavailability of clay minerals has proven useful for them as drug carriers. While their natural abundance, low toxicity, and accessible cost have contributed to classical applications of clay minerals, a wide range of interesting new applications may be facilitated, mainly through incorporating different organic molecules. The search for new functional materials is promising to challenge research on clay minerals in biological or biotechnological approaches.

Montmorillonite with essential oils as antimicrobial agents, packaging, repellents, and insecticides: an overview.

Essential oils (EOs) are complex natural mixtures of secondary plant metabolites that function as biocides and therapeutic agents. They are extensively used in bactericidal, virucidal, fungicidal, antiparasitic, insecticidal, pharmaceutical, and cosmetic products. However, certain characteristics, such as the volatility of EOs, hinder their widespread use. To mitigate this limitation, several studies have investigated combinations of EOs with natural materials, including clay minerals. Clay minerals are abundant in nature, biocompatible, and non-toxic to the environment and humans. Clay minerals such as montmorillonite possess available sites where EO molecules can interact. The combination of EOs with clay minerals produces new materials for various applications including antibacterial, antifungal, insecticidal/repellent, and active packaging materials. Therefore, this review focuses on the immobilization of several types of EOs in raw and modified montmorillonites. The applications of the described systems were evaluated and demonstrated the synergism of the properties of the isolated components as a function of different EOs incorporated in the silicate matrix.