Nanocomposite Based on Bacterial Cellulose and Silver Nanoparticles Improve Wound Healing Without Exhibiting Toxic Effect

Wound healing is an important and complex process, containing a multifaceted process governed by sequential yet overlapping phases. Certain treatments can optimize local physiological conditions and improve wound healing. Silver nanoparticles (AgNP) are widely known for their antimicrobial activity. On the other hand, bacterial cellulose (BC) films have been used as a dressing that temporarily substitutes the skin, offering many advantages in optimizing wound healing, in addition to being highly biocompatible. Considering the promising activities of AgNP and BC films, the present study aimed to evaluate the wound healing activity in Wistar Hannover rats using a nanocomposite based on bacterial cellulose containing AgNP (AgBC). In a period of 21 days, its influence on the wound area, microbial growth, histopathological parameters, and collagen content were analyzed. In addition, toxicity indicators were assessed, such as weight gain, water consumption, and creatinine and alanine transaminase levels. After 14 days of injury, the animals treated with AgBC showed a significant increase in wound contraction. The treatment with AgBC significantly reduced the number of microbial colonies compared to other treatments in the first 48 h after the injury. At the end of the 21 experimental days, an average wound contraction rate greater than 97 % in relation to the initial area was observed, in addition to a significant increase in the amount of collagen fibers at the edge of the wounds, lower scores of necrosis, angiogenesis and inflammation, associated with no systemic toxicity. Therefore, it is concluded that the combination of preexisting products to form a new nanocomposite based on BC and AgNP amplified the biological activity of these products, increasing the effectiveness of wound healing and minimizing possible toxic effects of silver.

Evaluation of the acute toxicity of ellagic acid and gallic acid incorporated in Poloxamer407® gel, in Zophobas morio larvae

Gallic acid (GA) has antioxidant, anti-inflammatory and antimicrobial properties, while ellagic acid (EA) demonstrates anticancer, antiviral and photoprotective activity. In this study, the combination of these substances incorporated into a poloxamer gel was tested to verify the individual effect of the substances, in addition to taking advantage of a probable complementary effect, aiming to provide additional therapeutic benefits. As a result of the incorporation, formulations containing GA, EA and GA + EA were obtained, which were evaluated for the effects of the Freeze-thaw cycle on pH, which revealed a significant decrease (p < 0.05) in most samples, including the vehicle (without drug) and the gel containing both drugs. No sample showed variation outside the normal pH range for the skin, with values ranging from 4.8 to 6.0. Regarding conductivity, the GA, EA and GA + EA formulations showed a reduction (p < 0.05) after the freeze-thaw cycle. The drug content in the formulations ranged from 95.86% to 101.35% initially to 91.30% to 101.51% after the freeze-thaw cycle. Regarding the drug release, the results revealed the following cumulative percentages: GA-3% - 92.58% after 1.5 h; AE-3% - 51.60% after 6 h; GA + EA (1.5% = 1.5%) - 99.91% after 2 h; GA + EA- (1.5% = 1.5%) released 57.06%, after 6 h. Regarding toxicity, it was observed that the group treated with GA showed a lower survival rate of the larvae (40%) at the dose 3000 mg/Kg in the formulation. Following the same trend, in the acute lethal concentration (ALC50) test performed using Zophobas morio larvae, an ALC50 of 2191.51 mg/Kg was observed for GA at 48 h. Melanin analysis showed a decrease in concentrations of 30 mg/Kg in the GA group, 3 mg/Kg of EA and 3, 300, 3000 mg/Kg of GA + EA, of the pure drugs. In the groups with the drugs incorporated into the gel, there was a significant decrease (P < 0.05) in melanin in the vehicle (gel), at concentrations of 300 and 3000 mg/Kg of GA and EA. On the other hand, in the combination of GA + EA, a reduction was observed at concentrations of 3 and 30 mg/Kg when compared to the control group. Thus, the gel showed good quality as a pharmaceutical formulation for topical use and low toxicity, making it promising for use in skin therapies.

Toxicological analyses of the venoms of Nigerian vipers Echis ocellatus and Bitis arietans

BACKGROUND

Among the medically important snakes in Nigeria, Echis ocellatus and Bitis arietans have the most lethal venom. These venoms were classified according to the presence of snake venom metalloproteinases (SVMPs), snake venom phospholipase A2 (PLA2s), and snake venom serine proteases (SVSPs). Toxicological analyzes were performed to understand the significance of different protein families in venoms.

METHODS

Proteins were separated from venom using column chromatography. The skin and footpad of mice were used to determine hemorrhagic and edematogenic activities. Caprine blood plasma was used to test fibrinolytic activity in vitro.

RESULTS

The results showed that, compared to the crude venom, the SVMP fraction induced hemorrhagic effects with a diameter of 26.00 ± 1.00 mm in E. ocellatus and 21.33 ± 1.52 mm in B. arietans. Both SVSP and SVMP had anticoagulant effects; however, the SVSP fraction had a stronger effect, with a longer anticoagulation time of 30.00 ± 3.00 min in E. ocellatus and 26.00 ± 2.00 min in B. arietans. These main venom toxins, SVMPs, SVSPs, and PLA2, were found to have edema-forming effects that were optimal at 2 h after envenomation. PLA2s had the highest edema-inducing activity, with onset 30 min after envenomation.

CONCLUSIONS

Given the importance of SVMPs in altering the integrity of the membrane structure and impairing the blood coagulation system, an antivenom that can specifically neutralize its activity could inhibit the hemorrhage effects of the venoms.

Acute and chronic toxicity of imidacloprid in the pollinator fly, Eristalis tenax L., assessed using a novel oral bioassay

Imidacloprid is a neonicotinoid neurotoxin that remains widely used worldwide and persists in the environment, resulting in chronic exposure to non-target insects. To accurately map dose-dependent effects of such exposure across taxa, toxicological assays need to assess relevant modes of exposure across indicator species. However, due to the difficulty of these experiments, contact bioassays are most frequently used to quantify dose. Here, we developed a novel naturalistic feeding bioassay to precisely measure imidacloprid ingestion and its toxicity for acute and chronic exposure in a dipteran, Eristalis tenax L., an important member of an under-represented pollinator group. Flies which ingested imidacloprid dosages lower than 12.1 ng/mg all showed consistent intake volumes and learned improved feeding efficiency over successive feeding sessions. In contrast, at doses of 12.1 ng/mg and higher flies showed a rapid onset of severe locomotive impairment which prevented them from completing the feeding task. Neither probability of survival nor severe locomotive impairment were significantly higher than the control group until doses of 1.43 ng/mg or higher were reached. We were unable to measure a median lethal dose for acute exposure (72 h) due to flies possessing a relatively high tolerance for imidacloprid. However, with chronic exposure (18 days), mortality went up and an LD50 of 0.41 ng/mg was estimated. Severe locomotive impairment (immobilisation) tended to occur earlier and at lower dosages than lethality, with ED50s of 7.82 ng/mg and 0.17 ng/mg for acute and chronic exposure, respectively. We conclude that adult Eristalis possess a much higher tolerance to this toxin than the honeybees that they mimic. The similarity of the LD50 to other dipterans such as the fruitfly and the housefly suggests that there may be a phylogenetic component to pesticide tolerance that merits further investigation. The absence of obvious adverse effects at sublethal dosages also underscores a need to develop better tools for quantifying animal behaviour to evaluate the impact of insecticides on foraging efficiency in economically important species.

In vivo antitumoral effect of 4-nerolidylcatechol (4-NC) in NRAS-mutant human melanoma

NRAS-mutations arise in 15-20% of all melanomas and are associated with aggressive disease and poor prognosis. Besides, the treatment for NRAS-mutant melanoma are not very efficient and is currently limited to immune checkpoints inhibitors or aggressive chemotherapy. 4-nerolidylcathecol (4-NC), a natural product extracted from Pothomorphe umbellata, induces apoptosis in melanoma cells by ROS production, DNA damage and increased p53 expression, in addition to inhibiting invasion in reconstructed skin. Moreover, 4-NC showed cytotoxicity in BRAF/MEKi-resistant and naive melanoma cells by Endoplasmic Reticulum (ER) stress induction in vitro. We evaluated the in vivo efficacy and the systemic toxicity of 4-NC in a NRAS-mutant melanoma model. 4-NC was able to significantly suppress tumor growth 4-fold compared to controls. Cleaved PARP and p53 expression were increased indicating cell death. As a proof of concept, MMP-2 and MMP-14 gene expression were decreased, demonstrating a possible role of 4-NC in melanoma invasion inhibition. Toxicological analysis indicated minor changes in the liver and bone marrow, but this toxicity was very mild when compared to other proteasome inhibitors and ER stress inductors already described. Our data indicate that 4-NC can counteract melanoma growth in vivo with minor adverse effects, suggesting further investigation as a potential NRAS-mutant melanoma treatment.