Matheus Ferreira de Souza

In this study, a full multilevel factorial design (2¹ × 3¹ × 2¹) × 2 was conducted to investigate the effects of molar mass of chitosan (CS), the type of acid used for dissolution, and the composition of the coagulation bath on the coagulation, mechanical properties, and swelling of the filaments. The results showed the statistical significance of the factors in the characteristics of these filaments. The coagulation followed Fick’s second law of diffusion, with an increase in the chitosan molar mass reducing the coagulation rate, as did the use of acetic acid instead of lactic acid. CS with higher molar mass produced filaments with larger diameters, but without a proportional increase in tensile strength. Swelling was influenced by the acid and composition of the coagulation bath. The interaction of CS with acid and the CS molar mass factor were the terms of greatest statistical significance. Crystallinity was higher for samples dissolved in aqueous solutions of acetic acid and coagulated with ethanol, while lactic acid induced greater structural disorder. Samples coagulated with ethanol presented more homogeneous surfaces, while methanol resulted in rougher filaments. These findings emphasize the critical role of processing conditions in tailoring the properties of CS filaments, providing valuable insights for their optimization for biomedical applications.

In this work, polyhydroxybutyrate (PHB) was maleic anhydride (MA)-grafted in the molten state, using dicumyl peroxide (DCP) as a reaction initiator. Tin(II) 2-ethylhexanoate (Sn(Oct)₂) and styrene monomer (St.) were used to maximize the maleic anhydride grafting degree. When PHB was modified with MA/DCP and MA/DCP/Sn(Oct)₂, viscosity was reduced, suggesting chain scission in relation to pure PHB. However, when the styrene monomer was added, the viscosity increased due to multiple grafts of MA and styrene into the PHB chain. In addition, the FTIR showed the formation of a new band at 1780 cm⁻¹ and 704 cm⁻¹, suggesting a multiphase copolymer PHB-g-(St-co-MA). The PHB (MA/DCP) system showed a grafting degree of 0.23%; however, the value increased to 0.39% with incorporating Sn(Oct)₂. The highest grafting efficiency was for the PHB (MA/DCP/St.) system with a value of 0.91%, while the PHB (MA/DCP/St./Sn(Oct)₂) hybrid mixture was reduced to 0.73%. The chemical modification process of PHB with maleic anhydride increased the thermal stability by about 20 °C compared with pure PHB. The incorporation of 0.5 phr of the Sn(Oct)₂ catalyst increased the efficiency of the grafting degree in the PHB. However, the St./Sn(Oct)₂ hybrid mixture caused a deleterious effect on the maleic anhydride grafting degree.

This work aimed to develop chitosan/gelatin scaffolds loaded with ethanolic extract of Jatropha mollissima (EEJM) to evaluate the influence of its content on the properties of these structures. The scaffolds were prepared by freeze-drying, with different EEJM contents (0–10% (w/w)) and crosslinked with genipin (0.5% (w/w)). The EEJM were characterized through High Performance Liquid Chromatography coupled to a Diode Array Detector (HPLC-DAD), and the determination of three secondary metabolites contents was accomplished. The physical, chemical and biological properties of the scaffolds were investigated. From the HPLC-DAD, six main substances were evidenced, and from the quantification of the total concentration, the condensed tannins were the highest (431.68 ± 33.43 mg·g⁻¹). Spectroscopy showed good mixing between the scaffolds’ components. Adding and increasing the EEJM content did not significantly influence the properties of swelling and porosity, but did affect the biodegradation and average pore size. The enzymatic biodegradation test showed a maximum weight loss of 42.89 within 28 days and reinforced the efficiency of genipin in crosslinking chitosan-based materials. The addition of the extract promoted the average pore sizes at a range of 138.44–227.67 µm, which is compatible with those reported for skin regeneration. All of the scaffolds proved to be biocompatible for L929 cells, supporting their potential application as skin tissue engineering materials.

Chitosan/montmorillonite nanocomposite films were prepared by the solvent evaporation method to immobilize the drug ibuprofen (IBU) and delay its release in a medium that simulates the environment of the gastrointestinal tract. The effects of montmorillonite, at different mass proportions (10, 20, and 50%), on the morphological and physical properties of the films were studied. The samples were characterized by X-ray diffraction (XRD), Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), degree of swelling, drug encapsulation, and drug release efficiency. According to the XRD it was evidenced that the incorporation of montmorillonite to chitosan led to the formation of nanocomposites of ordered morphology. The infrared spectra confirmed the good interaction between montmorillonite and chitosan by the formation of nanocomposites. This fact, which favored the imprisonment of the IBU, reduced the diffusion coefficient in the studied systems. The micrographs comproved the formation of dense and uniform films. The controlled release profile, especially for the nanocomposite with 10% clay mass, showed a slow drug release rate. The incorporation of montmorillonite at different proportions produced different morphologies, with good encapsulation efficiency and an adequate profile for the controlled release of the drug.

Episiotomy is an obstetric technique that consists of making an incision in the perineum during vaginal childbirth, to facilitate the baby to pass through. After delivery, the perineal region is sutured with absorbable threads to heal the cut. However, are frequent reports of pain, infections, and dyspareunia after the execution of this technique. In this context, the use of biomaterials becomes relevant as they promote faster and safer tissue repair, making it an attractive alternative for the healing process of episiotomy. Based on the physical-chemical and biological properties of chitosan and Aloe vera, this research developed three different vaginal gels, with the purpose of promoting tissue regeneration and infection prevention post-episiotomy. Chitosan solutions with concentrations of 5% w/v were prepared by dissolving the chitosan powder in 2% v/v aqueous solution of acetic acid. After the extraction and processing of the mucilage, the pulp of the Aloe vera leaf was added to the chitosan gel in the proportions of 1, 2, and 3% v/v. All formulations were neutralized by the slow drip technique of a neutralizing solution of sodium hydroxide (2 M). The compositions were analyzed according to their organoleptic aspect, optical microscopy, spreadability, hydrogen potential, absorption spectroscopy, cytotoxicity, and rheological behavior. Based on the results obtained, it was possible to conclude that gels produced have the potential to be used as vaginal gels.

Chitosan is a natural, biodegradable, non-toxic and biocompatible polymer, with characteristics such as a healing, hemostatic, antimicrobial agent, among others. Therefore, the aim of this study is to develop a tubular chitosan device for use as a prosthetic coating application in vascular surgery. The chitosan wires were obtained by the spinning method in a 2M sodium hydroxide coagulant solution (NaOH) and used in the form of wires and screens as a reinforcement structure to obtain the tubes. In order to characterize the tubes, optical microscopy, contact angle, degree of swelling, in vitro biodegradation, cytotoxicity and tensile strength were used. The results indicated that the tubes have uniformity over the entire length and as for the resistance to the trace, the tube reinforced with mesh presented greater deformation, while the tube reinforced with wire presented a higher value of rupture stress. The degree of swelling was higher in chitosan tubes with mesh. As for the biodegradation test, it was observed that the lysozyme samples showed greater loss of mass and the cytotoxicity test confirmed the cell viability of the material, concluding that the tubes reinforced with chitosan wires are promising for use in vascular surgeries.

Cranioencephalic traumatism (TBI) is a common situation in trauma hospitals and has become responsible for high rates of mortality worldwide. When the victim of TBI is affected by injuries to the skullcap with a need for grafting, problems regarding the availability of suitable and affordable materials eventually happen. In this study, a 3D structure of Polyetheretherketone (PEEK) that mimics the cranial bone morphology for use in cranioplasty was developed. Samples of different formulations, in the form of round bars, were obtained through uniaxial compression, and porosity was controlled by the salt leaching technique. Then, the specimens were characterized in terms of pore morphology and distribution, surface roughness, compression resistance and cytotoxicity. Results exhibited high levels of similarity of the 3D strutures of PEEK to the natural human bone, which indicates the effectiveness of the proposed method in mimicking the morphology of the compact/porous/compact system of the skullcap (diploe).

As bentonitas são amplamente investigadas por atuarem como agentes viscosificantes e estabilizantes de fluidos emulsionados. As propriedades dos fluidos de perfuração são extremamente importantes, para o alcance do sucesso da perfuração do poço de petróleo. Todavia, a purificação das argilas se faz necessário para promover uma melhora no comportamento reológico das dispersões. Assim como as argilas bentoníticas naturais, as argilas organofílicas obtidas a partir de argilas bentoníticas sódicas possuem uma gigantesca importância industrial devido ao seu alto grau de inchamento em água, e sais quarternários de amônio. Neste estudo, a influência do tipo de argila é investigada reologicamente em fluidos emulsionados de diferentes proporções mássicas óleo/água (O/W): 50/50, 70/30, 80/20, 90/10 e 95/05 sob a concentração de 6000ppm. As amostras de argilas foram caracterizadas por FRX, DRX E TG/DTA. Todos os fluidos emulsionados de base oleoso foram analisados através de observações morfológicas do tipo macroscópico e reológico. As argilas bentoníticas verde-lodo purificada (hidrofílica) e verde-lodo organofílica (hidrofóbica) foram testadas como agentes viscosificantes e estabilizantes das emulsões. A partir dos resultados, foi possível verificar a composição química das argilas, sendo a argila organofílica a de maior perda ao fogo, a eficiência da intercalação do surfactante na argila verde-lodo organofílica denotada nos difratogramas de raios X, assim como, os eventos de perda de massa, onde a verde-lodo organofílica apresentou uma maior perda. Reologicamente os resultados confirmaram que somente a emulsão contendo argila verde-lodo organofílica de fração mássica 50/50 (O/W) apresentou-se estável fisicamente.