Deleterious Effects of Polypropylene Microplastic Ingestion in Nile Tilapia (Oreochromis niloticus).

The effect of daily ingestion of polypropylene microplastic on the health of tilapia, Oreochromis niloticus, was evaluated. 60 fish (± 200 g) were placed in 6 aquariums (n = 10, 100 L each), constituting the following treatments: Control (without the addition of polymer), fed with 100 and 500 µg of polypropylene/kg of body weight (b.w.), respectively. After 30 days of feeding, the animals were submitted to blood collection for hemogram and biochemical study and later euthanized for gut microbiological analysis, somatic index of liver, spleen, heart, kidney, stomach, and intestine. In the serum biochemical study, an increase in cholesterol and serum Aspartate Aminotransferase (AST) activity levels was observed in animals treated with 500 µg of polypropylene. Tilapia-fed polypropylene in the diet showed an increase in thrombocyte and total leukocyte counts, marked by a significant increase in the number of circulating lymphocytes. The results of the somatic study revealed a significant increase in the stomach, liver, and heart of tilapia fed with the polymer. Increase in the number of Gram-negative microorganisms and decrease in mesophilic aerobic microorganisms were observed in the gut of fish exposed to the polymer, including a dose-response effect was observed for these analyses. Therefore, tilapias fed daily with diets containing polypropylene for 30 consecutive days showed deleterious effects, resulting in systemic inflammatory disturbs by altering liver functions, leukocyte profile, and organ morphometry, as well as changes in the intestinal microbiota. Such results demonstrate the impairment of fish health, highlighting the need for further studies that evaluate the impact of microplastics on aquatic organisms.

Device implant based on poly (lactic acid) with vitamin E for vaccine delivery system in Tilapia: Study for biocompatibility and biodegradation.

The use of Poly (lactic acid) (PLA) as a slow-release vehicle for vaccines has attracted the attention of researchers, since its insertion improves the uptake of them, and reduces side effects or by stimulating recruited defense cells, assisting immunity without the need for booster vaccine doses. Seeking to develop new strategies for the administration of drugs and vaccines in aquaculture, we evaluated the biocompatibility and biodegradation of polymeric PLA devices and PLA plus vitamin E devices, implanted through subcutaneous (SC) and intraperitoneal (IP) routes in Nile tilapia. To carry out this study, 84 male tilapia (initial 243.82 ± 56.74 g; final 400.71 ± 100.54 g) were randomly distributed in 3 tanks (n = 28 fish per treatment/tank). The devices were prepared in two formulations: neat PLA (containing 100% PLA) and PLAVE (PLA plus vitamin E) implanted using a commercial AnimalTag® applicator, and non-implanted fish (control). Fish were sampled 15, 30, 60, and 120 days post-implantation (DPI). Blood analysis was used to access blood cells and blood smear for differential leucocytes count. Serum biochemistry to evaluated changes in serum proteins and glycemia. Histopathological investigation using hematoxylin-eosin (H&E) was used to assess polymer-tissue interaction. Histochemistry and immunohistochemistry was used to detection immune cells and phagocytes in capsule, and analyses of melanomacrophage centers (MMCs) to morphometric evaluation and percentage amount of melanin, hemosiderin and lipofucsin pigments. Histopathological study revealed an increase of capsular formation and inflammatory cell infiltration in PLAVE-implanted tilapia through SC route (15 DPI). Tilapia implanted with PLAVE and PLA (SC) presented mast cells and eosinophilic granular cells during 15, 30, and 60 DPI, with a decrease in these cells in the fibrous capsule around the polymer at 120 DPI. PLAVE implanted tilapia SC at 60 DPI showed significantly phagocytosis points than other groups. Phagocytic cells (F4/80+) were observed near to biopolymers in phagocytosis sites. Lipofuscin at 120 DPI in spleen melanomacrophage centers were significantly high in PLAVE implanted tilapias when compared to fish with PLA implants and control. The serum biochemical study of tilapia did not reveal changes in cytotoxicity and liver function in implanted fish. The absence of side effects in hematological and biochemical findings, including the absence of mortality after device implantation, proves its clinical safety. PLA implants in tilapia have demonstrated biocompatibility, biodegradation, clinical safety, and excellent evolution of foreign body inflammatory responses.