Self-Photopolymerizable Hydrogel-Ceramic Composites with Scavenger Properties.

The photocatalytic behaviours of semiconductive ceramic nanoparticles such as TiO2, ZnO, Fe2O3, and Fe3O4, have been extensively studied in photocatalysis and photopolymerization, due to their ability to produce radical species under ultraviolet-visible light, and even in dark conditions. In addition, in the form of microparticles, TiO2 and its Magnéli phases are capable of neutralizing radical species, and a heterogeneous catalytic process has been suggested to explain this property, as it is well known as scavenging activity. Thus, in this study, we demonstrate that these ceramic powders, in the form of microparticles, could be used as photoinitiators in UV polymerization in order to synthesize a hydrogel matrix. Them, embedded ceramic powders could be able to neutralize radical species of physiological media once implanted. The hydrogel matrix would regulate the exchange of free radicals in any media, while the ceramic particles would neutralize the reactive species. Therefore, in this work, the scavenger activities of TiO2, ZnO, Fe2O3, and Fe3O4 microparticles, along with their photoinitiation yield, were evaluated. After photopolymerization, the gel fraction and swelling behaviour were evaluated for each hydrogel produced with different ceramic initiators. Gel fractions were higher than 60%, exhibiting variation in their scavenging activity. Therefore, we demonstrate that ceramic photoinitiators of TiO2, ZnO, Fe2O3, and Fe3O4 can be used to fabricate implantable devices with scavenger properties in order to neutralize radical species involved in inflammatory processes and degenerative diseases.

Nanocellulose for peripheral nerve regeneration in rabbits using citric acid as crosslinker with chitosan and freeze/thawed PVA.

This work investigates peripheral nerve regeneration using membranes consisting of pure chitosan (CHI), which was further blended with nanofibrillated cellulose, with citric acid as crosslinker, with posterior addition of polyvinyl alcohol, with subsequent freeze thawing. Nanocellulose improves the mechanical and thermal resistance, as well as flexibility of the film, which is ideal for the surgical procedure. The hydrogel presented a slow rate of swelling, which is adequate for cell and drug delivery. A series ofin vitrotests revealed to be non-toxic for neuronal Schwann cell from the peripheral nervous system of Rattus norvegicus, while there was a slight increase in toxicity if crosslink is performed-freeze-thaw. Thein vivoresults, using rabbits with a 5 mm gap nerve defect, revealed that even though pure CHI was able to regenerate the nerve, it did not present functional recovery with only the deep pain attribute being regenerated. When autologous implant was used jointly with the biomaterial membrane, as a covering agent, it revealed a functional recovery within 15 d when cellulose and the hydrogel were introduced, which was attributed to the film charge interaction that may help influence the neuronal axons growth into correct locations. Thus, indicating that this system presents ideal regeneration as nerve conduits.

Synthesis and in vivo evaluation of a scaffold containing wollastonite/ß-TCP for bone repair in a rabbit tibial defect model.

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 ß-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.

A tough and novel dual-response PAA/P(NiPAAM-co-PEGDMA) IPN hydrogels with ceramics by photopolymerization for consolidation of bone fragments following fracture.

In this work, a novel dual-response hydrogel for enhanced bone repair following multiple fractures was investigated. The conventional treatment of multiple bone fracture consists on removing smaller bone fragments from the body in a surgery, followed by the fixation of the bone using screws and plates. This work proposes an alternative for this treatment via in situ UV-initiated radical polymerization of a novel IPN hydrogel composed of PAA/P(NiPAAM-co-PEGDMA) incorporated with ceramic additives. The influence of different additives on mechanical properties and sensitivity of the polymer, as well as the prepolymer mixture, were investigated in order to analyse the suitability of the composites for bone healing applications. This material exhibited an interpenetrating network, confirmed by FTIR, with ceramics particles dispersed in between the polymer network. These structures presented high strength by tensile tests, sensitivity to pH and temperature and a decrease on Tg values of NiPAAm depending on the amount of PEGDMA and ceramics added; although, the addition of ceramics to these composites did not decrease their stability drastically. Finally, cytotoxicity tests revealed variations on the toxicity, whereas the addition of TCP presented to be non-toxic and that the cell viability increased when ceramics additives were incorporated into the polymeric matrix with an increased reporter activity of NF-κB, associated with aiding fibroblast adhesion. Hence, it was possible to optimise feedstock ratios to increase the applicability of the prepolymer mixture as a potential treatment of multiple fractures.

Synthesis and in Vivo Behavior of PVP/CMC/Agar Hydrogel Membranes Impregnated with Silver Nanoparticles for Wound Healing Applications.

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.

Oral administration of an anti-inflammatory does not compromise the efficacy of intra-testicular injection of zinc gluconate as a contraceptive for dogs.

The objective was to determine whether the efficacy of zinc gluconate (Testoblock(®)) as a chemical contraceptive in male dogs was compromised in the presence of metamizole sodium (a nonsteroidal antiinflammatory/analgesic agent). Ten sexually mature mongrel dogs were assigned to two groups, a control group (n = 5) and a treated group (n = 5). Testoblock(®), a proprietary zinc-gluconate (13.1 mg zinc/ml) solution in a physiological vehicle, was injected into each testis (0.2-1.0 ml/testis, based on testis width). Half of the dogs (treated group) were also given metamizole sodium (also known as sodium dipyrone) orally (25mg/kg three times a day for 2 days), starting 2-3 h after testis injection. A physical examination and assessment of testis width, hematology, clinical chemistry (hepatic and renal function) and semen characteristics, were done immediately after treatment and then every 2 months for 180 days. There was no post-treatment scrotal biting or licking, although there was transient testicular swelling in both control and treated dogs during the first 3 days after injection. At 60 days after injection, all dogs were azoospermic. At 120 and 180 days, seven dogs had azoospermia and the remaining three (two control and one treated) had apparent aspermia (no ejaculate could be collected). There were no significant differences between groups for clinical findings or any aspect of hematology, renal, or hepatic function. In conclusion, giving metamizole sodium concurrent with an intra-testicular injection of a zinc-based solution did not interfere with chemical sterilization and it improved animal welfare.

Permanent contraception of dogs induced with intratesticular injection of a Zinc Gluconate-based solution.

The objective was to evaluate the efficacy of a single intratesticular injection of a Zinc Gluconate-based solution to induce sterility in male dogs. Fifteen pubertal mongrel dogs (8 mo to 4 y old) were assigned to two groups; Control dogs (n = 5) received a single injection of an isotonic saline solution into each testis, whereas Treated dogs (n = 10), were given Testoblock, a proprietary zinc-gluconate (13.1 mg zinc/ml) solution in a physiological vehicle. The volume of saline or Testoblock injected varied from 0.2 to 1.0 ml/testis (based on testis width). Physical examination, testis width, hematology, clinical chemistry (hepatic and renal function), plasma testosterone concentration, semen characteristics, and libido, were assessed until castration (150 d after treatment). In Treated dogs, testis width increased (approximately 20%) relative to that in Control dogs, but subsequently was not significantly different from Controls (group × time interaction, P < 0.0001). For all dogs, values for hematology and clinical chemistry consistently remained within reference ranges. Although plasma testosterone concentrations decreased over time (P < 0.006), there was only a tendency for an effect of group (P < 0.09), and libido was not significantly affected. By 63 d after Testoblock treatment, eight Treated dogs were azoospermic, whereas the remaining two were oligozoospermic (<10 × 10(6) sperm/ml). We concluded that intratesticular injection of the Zinc Gluconate-based chemical sterilant Testoblock has considerable potential to induce permanent contraception in male dogs.