No abstract

The field of wound healing has seen an increase in research activity in wound care and hydrogel-based dressings have been targeted as a solution for these applications. Hydrogels with silver nanoparticles can present many advantages for this field. However, if the aggregation and sterilization of this product have not been carefully considered, the effectiveness or use could be limited. Therefore, in the current study, a hydrogel-based wound dressing membrane was developed using polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), agar, and carboxymethyl cellulose (CMC). Silver ions (Ag+) were dispersed in the polymer matrix and its reduction with formation of a hydrogel and silver nanoparticles was performed using 60Co gamma irradiation to enhance the dressings antimicrobial properties. The resulting hydrogel presented a high degree of swelling and a good size control of silver nanoparticles. The incorporation of AgNPs was confirmed via Raman spectroscopy and the samples presented no signs of toxicity in vitro as assessed using an elution assay with neutral red uptake as the cytotoxic end point. Membranes were tested in vivo using a full thickness defeat model in rabbits. Postmortem histopathological analysis indicated that the use of the hydrogel membranes that incorporated AgNPs had a stimulatory action on wound healing as evidenced by a high intensity of fibroblasts and neovascularization in the tissue, which promoted a faster healing process when compared to the untreated wounds. We demonstrate the possibility of producing a hydrogel with good size control of AgNPs, which can also be directly sterilized within the formation of this material via gamma irradiation. Furthermore, the mechanism of hydrogel healing, in vivo, with silver nanoparticles was found to have a direct correlation of silver nanoparticles with in vitro cell results.

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Scaffolds are models designed to aid the interaction between cells and extracellular bone matrix, providing structural support for newly formed bone tissue. In this work, wollastonite with β‐TCP porous ceramic scaffolds was developed by the polymer sponge replication. Their microstructure, cell viability and bioactivity were tested. in vivo was performed to evaluate the use of a calcium silicate‐based implant in the repair of rabbit tibias. Holes were made in the both proximal and distal tibial metaphysis of each animal and filled with calcium silicate‐based implant, and in the left tibia, no implant were used, serving as control group. Animals underwent euthanasia after 30 and 60 days of study. The animals were submitted to clinical‐radiographic evaluations and their histology was analyzed by optical and scanning electron microscope. The studied calcium silicate implant provided biocompatibility and promoted bone formation, stimulating the process of bone repair in rabbits, features observed by gradual radiopacity shown in the radiographic evaluations.

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The main goal of this study is to evaluate potential applications of two zirconia-hydroxyapatite composites, Z4H6 and Z6H4, as bone substitutes. Composite plugs were implanted into the distal femoral metaphysis and also onto the longissimus dorsi of 18 adult mixed-breed dogs in order to assess in vivo biocompatibility by immediate clinical and radiographic evaluation 30, 90, and 120 days after implantation. Radiographic examination revealed radiolucency on the defect site. However, a progressive increase in bone density was observed over time, reaching a radiopacity similar to that of bone 120 days after implantation. Histological study revealed that a thin layer of fibroblasts was observed at the implant-bone interface in addition to osteoblastic activity 30 days after implantation, whereas bone neoformation around the implants was detected for the subsequent implantation times (90 and 120 days). Otherwise, the histological evaluation of the implant-muscle interface showed the presence of an initially thick fibrous tissue layer 30 days after implantation, which decreased with longer investigation times (90 and 120 days). The numbers of plasmocytes, lymphocytes, and macrophages gradually reduced as a function implantation time, being completely absent 120 days after implantation with a resulting complete osteointegration process. The zirconia phase content did not affect the bioactive behavior of the implants investigated and did not induce bone formation when implanted into muscle either.

The aim of this research was to evaluate the process of bone regeneration in rabbits, using chitosan and beta-tricalcium phosphate (β-TCP) independently and in combination. A total of 12 New Zealand rabbits of both sexes, with average weight of 3.0 ± 0.57 kg were used. Animals were randomly divided into two experimental time points, with six animals euthanized 45 days after surgery and six euthanized 90 days after surgery. We performed two osteotomies in each tibia. The left tibia was used for the chitosan (QUI) and control groups, and the right tibia was used for the β-TCP alone and in combination with chitosan (QUI+TCP) groups. Tomographic evaluation showed no statistically significant difference among groups; however radiopacity was higher in the treated groups. Comparative descriptive histological evaluation found that treatment groups stimulated a more pronounced tissue repair reaction and accelerated bone repair. Morphometric analysis showed that treatment groups presented statistically higher bone formation compared with the control group.

Avaliação de diferentes proporções de fosfato de cálcio na regeneração do tecido ósseo de coelhos: estudo clínicocirúrgico, radiológico e histológico Evaluation of different proportions of calcium phosphate in the regeneration of bone tissue of rabbits: clinical-surgical, radiological and histological study