Gabriel Goetten de Lima

Extraction Method Plays Critical Role in Antibacterial Activity of Propolis-Loaded Hydrogels

Extracted propolis has been used for a long time as a remedy. However, if the release rate of propolis is not controlled, the efficacy is reduced. To overcome this issue, extracted propolis was added to a cryogel system. Propolis collected from southern Brazil was extracted using different methods and loaded at different concentrations into polyvinyl alcohol (PVA) and polyacrylic acid hydrogels as carrier systems. The material properties were investigated with a focus on the propolis release profiles and the cryogel antibacterial properties against 4 different bacteria, namely: Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, and Pseudomonas putida. Swelling studies indicated that the swelling of the hydrogel was inversely related to propolis content. In addition, propolis release studies indicated a decreased release rate with increased propolis loading. PVA and PVA/polyacrylic acid-loaded propolis were effective against all 4 bacteria studied. These results indicate that the efficacy of propolis can be enhanced by incorporation into hydrogel carrier systems and that hydrogels with higher concentrations of propolis can be considered for use as bactericide dressing.

Mechanical properties of anodic titanium films containing ions of Ca and P submitted to heat and hydrothermal treatment

Anodic oxidation is a technique widely used to improve the bioactivity of Ti surface. In this study, micro-arc oxidation (MAO) was used to obtain an anodic film incorporating Ca and P ions to evaluate the effect of heat and hydrothermal treatment on the mechanical and in vitro bioactivity properties of these new layers. The MAO process was carried out using (CH3COO)2Ca·H2O and NaH2PO4·2H2O electrolytes under galvanostatic mode (150mA/cm(2)). The thermal treatments were made at 400°C and 600°C in air atmosphere while hydrothermal treatment was made in an alkaline water solution at 130°C. These surfaces presented desired mechanical properties for biomedical applications owing to the rutile and anatase phases in the anodic film that are more crystalline after thermal treatments; which provided an increase in hardness values and lower elastic modulus. The dry sliding wear resistance increased by performing thermal treatments on the surfaces with one condition still maintaining the film after the test. Bioactivity was investigated by immersion in simulated body fluid during 21 days and hydroxyapatite was formed on all samples. Finally, lower values of contact angle were obtained for heat treated samples.

Electrospinning of Hydrogels for Biomedical Applications

The field of biomedical applications for hydrogels requires the development of nanostructures with specific controlled diameter and mechanical properties. Nanofibers are ideal candidates for these advanced requirements, and one of the easiest techniques that can produce one-dimensional nanostructured materials in fibrous form is the electrospinning process. This technique provides extremely thin fibers with controlled diameter and highly porous microstructure with interconnected pores. Electrospinning demonstrates extreme versatility allowing the use of different polymers for tailoring properties and applications. It is a simple cost-effective method for the preparation of scaffolds. In this section, we will discuss recent and specific applications with a focus on their mechanisms. As such, we conclude this section with a discussion on perspectives and future possibilities on this field.

Structure Response for Cellulose-Based Hydrogels Via Characterization Techniques

Hydrogels are three-dimensional cross-linked polymeric networks capable of imbibing substantial amounts of water or biological fluids and are widely used in biomedical applications, especially in pharmaceutical industry as drug delivery systems. Although their solvent content can be over 99%, hydrogels still retain the appearance and properties of solid materials, and the structural response can include a smart response to environmental stimuli (pH, temp, ionic strength, electric field, presence of enzyme, etc.) These responses can include shrinkage or swelling. Cellulose-based hydrogels are one of the most commonly used materials and extensively investigated due to the widespread availability of cellulose in nature. Cellulose is the most abundant renewable resource on earth that is intrinsically degradable. Additionally, the presence of hydroxyl groups results in fascinating structures and properties. Also, cellulose-based hydrogels with specific properties can be obtained by combining it with synthetic or natural polymers. This chapter surveys different characterization for cellulose hydrogels and the structure-response relationship. As such we would describe the techniques involved for characterizing cellulose-based hydrogels and their response in terms of their morphology such as polarized optical microscopy (POM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), their stability by thermal properties (often with differential scanning calorimetry, DSC), and structure response such as Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). In addition, we give a focus on measuring the mechanical properties of superabsorbent hydrogels giving examples with cellulose where applicable. Finally, we describe the techniques for analyzing biological techniques and the applications with cellulose.

Platelet-Rich Plasma, Hydroxyapatite, and Chitosan in the Bone and Cartilaginous Regeneration of Femoral Trochlea in Rabbits: Clinical, Radiographic, and Histomorphometric Evaluations

The aim of this study was to evaluate the trochlear bone and cartilaginous regeneration of rabbits using the association of PRP, chitosan, and hydroxyapatite. Hole was made in rabbit troches, one hole in each animal remained empty (group C), and one was filled by a combination of PRP, chitosan, and hydroxyapatite (group T). Clinical-orthopedic, radiographic, and histomorphometric evaluations were performed. Clinical-orthopedic evaluation showed lameness of two members of the T group and one member of group C. The radiographic evaluation showed that the T group showed absence of subchondral bone reaction (33%). The presence of moderate subchondral bone reaction was more frequently reported in group C with 67%. Microscopic evaluation revealed a presence of tissue neoformation, composed of connective tissue. Microscopic findings were similar in both groups, with a difference in the amount of neoformed tissue being perceptible, which was confirmed after the morphometric analysis, which revealed a significant difference in the quantity of newly formed tissue at the bone/cartilage/implant interface. The composite base of the association of chitosan, hydroxyapatite, and platelet-rich plasma favored bone and cartilage healing.