Histopathological analysis of zebrafish after introduction of non-biodegradable polyelectrolyte microcapsules into the circulatory system

Polystyrene nanoplastics synergistically exacerbate diclofenac toxicity in embryonic development and the health of adult zebrafish

In this study, we investigated the possible ecotoxicological effect of co-exposure to polystyrene nanoplastics (PS-NPs) and diclofenac (DCF) in zebrafish (Danio rerio). After six days of exposure, we noticed that the co-exposure to PS-NP (100 μg/L) and DCF (at 50 and 500 μg/L) decreased the hatching rate and increased the mortality rate compared to the control group. Furthermore, we noted that larvae exposed to combined pollutants showed a higher frequency of morphological abnormalities and increased oxidative stress, apoptosis, and lipid peroxidation. In adults, superoxide dismutase and catalase activities were also impaired in the intestine, and the co-exposure groups showed more histopathological alterations. Furthermore, the TNF-α, COX-2, and IL-1β expressions were significantly upregulated in the adult zebrafish co-exposed to pollutants. Based on these findings, the co-exposure to PS-NPs and DCF has shown an adverse effect on the intestinal region, supporting the notion that PS-NPs synergistically exacerbate DCF toxicity in zebrafish.

Cadmium and ketoprofen accumulation influences aquatic ecosystem demonstrated using in-vivo zebrafish model

The growing concern about pollution and toxicity in aquatic as well as terrestrial organisms is predominantly caused due to waterborne exposure and poses a risk to environmental systems and human health. This study addresses the co-toxic effects of cadmium (Cd) and ketoprofen (KPF), representing heavy metal and pharmaceutical discharge pollutants, respectively, in aquatic ecosystems. A 96-h acute toxicity assessment was conducted using zebrafish embryos. The results indicated that high dosages of KPF (10, 15, and 100 µg/mL) and Cd (10 and 15 µg/mL) reduced survivability and caused concentration-dependent deformities such as scoliosis and yolk sac edema. These findings highlight the potential defects in development and metabolism, as evidenced by hemolysis tests demonstrating dose-dependent effects on blood cell integrity. Furthermore, this study employs adult zebrafish for a 42-day chronic exposure to Cd and KPF (10 and 100 µg/L) alone or combined (10 + 10 and 100 + 100 µg/L) to assess organ-specific Cd and KPF accumulation in tissue samples. Organ-specific accumulation patterns underscore complex interactions impacting respiratory, metabolic, and detoxification functions. Prolonged exposure induces reactive oxygen species formation, compromising antioxidant defense systems. Histological examinations reveal structural changes in gills, gastrointestinal, kidney, and liver tissues, suggesting impairments in respiratory, osmoregulatory, nutritional, and immune functions. This study emphasizes the importance of conducting extensive research on co-toxic effects to assist with environmental risk assessments and safeguard human health and aquatic ecosystems.

Tissue Reaction to Low-Density Polyacrylamide Gel as a Carrier for Microimplants in the Adipose Fin of Rainbow Trout

The implantation of optical sensors is a promising method for monitoring physiological parameters of organisms in vivo. For this, suitable hydrogels are required that can provide a biocompatible interface with the organism's tissues. Amorphous hydrogel is advantageous for administration in animal organs due to its ease of injection compared to resilient analogs. In this study, we investigated the applicability of a semi-liquid 2.5% polyacrylamide hydrogel (PAAH) as a scaffold for fluorescent polyelectrolyte microcapsules (PMs) in rainbow trout. The hydrogel was injected subcutaneously into the adipose fin, which is a small, highly translucent fold of skin in salmonids that is convenient for implanting optical sensors. Using histological methods, we compared tissue organization and in vivo stability of the applied hydrogel at the injection site after administration of uncoated PMs or PMs coated with 2.5% PAAH (PMs-PAAH) for a period of 3 to 14 days. Our results showed that the introduction of PMs into the gel did not have a masking effect, as they were recognized, engulfed, and carried away by phagocytes from the injection site. However, both PMs and PMs-PAAH were found to provoke chronic inflammation at the injection site, although according to cytokine expression in the fish spleen, the irritating effect was local and did not affect the systemic immunity of the fish. Therefore, our study suggests low applicability of 2.5% polyacrylamide as a scaffold for injectable sensors within a timeframe of days.

New insight into long-term effects of phthalates microplastics in developing zebrafish: Evidence from genomic alteration and organ development

The plasticizer leaches from the microplastics are one of the significant concerns related to plastic pollution. These plasticizers are known to be endocrine disrupters; however, little is known about their long-term effect on the development of aquatic vertebrates. Hence, the present study has been conducted to provide a holistic understanding of the effect of the three most common plasticizers, dibutyl phthalate (DBP), diethyl phthalate (DEP), and di-ethylhexyl phthalate (DEHP) leaching out from the microplastics in zebrafish development. Zebrafish larvae were exposed to different phthalates at different concentrations. The phthalates have shown significantly higher mortality and morphological changes in the larva upon exposure compared to the control. A significant change in the genes related to cardiovascular development (krit1, fbn2b), dorsoventral axis development (chrd, smad5), tail formation (pkd2, wnt3a, wnt8a), and floorplate development (foxa2) were also observed under the effects of the phthalates in comparison to control.

Durability of Implanted Low-Density Polyacrylamide Hydrogel Used as a Scaffold for Microencapsulated Molecular Probes inside Small Fish

Implantable sensors based on shaped biocompatible hydrogels are now being extensively developed for various physiological tasks, but they are usually difficult to implant into small animals. In this study, we tested the long-term in vivo functionality of pH-sensitive implants based on amorphous 2.7% polyacrylamide hydrogel with the microencapsulated fluorescent probe SNARF-1. The sensor was easy to manufacture and introduce into the tissues of a small fish Danio rerio, which is the common model object in biomedical research. Histological examination revealed partial degradation of the gel by the 7th day after injection, but it was not the case on the 1st day. Using the hydrogel sensor, we were able to trace the interstitial pH in the fish muscles under normal and hypercapnic conditions for at least two days after the implantation. Thus, despite later immune response, amorphous polyacrylamide is fully suitable for preparing implantable sensors for various mid-term physiological experiments on small fishes. The proposed approach can be further developed to create implantable sensors for animals with similar anatomy.

PEGDA microencapsulated allogeneic islets reverse canine diabetes without immunosuppression

Background

Protection of islets without systemic immunosuppression has been a long-sought goal in the islet transplant field. We conducted a pilot biocompatibility/safety study in healthy dogs followed by a dose-finding efficacy study in diabetic dogs using polyethylene glycol diacrylate (PEGDA) microencapsulated allogeneic canine islets.

Methods

Prior to the transplants, characterization of the canine islets included the calculations determining the average cell number/islet equivalent. Following measurements of purity, insulin secretion, and insulin, DNA and ATP content, the islets were encapsulated and transplanted interperitoneally into dogs via a catheter, which predominantly attached to the omentum. In the healthy dogs, half of the microspheres injected contained canine islets, the other half of the omentum received empty PEGDA microspheres.

Results

In the biocompatibility study, healthy dogs received increasing doses of cells up to 1.7 M cells/kg body weight, yet no hypoglycemic events were recorded and the dogs presented with no adverse events. At necropsy the microspheres were identified and described as clear with attachment to the omentum. Several of the blood chemistry values that were abnormal prior to the transplants normalized after the transplant. The same observation was made for the diabetic dogs that received higher doses of canine islets. In all diabetic dogs, the insulin required to attempt to control blood glucose was cut by 50–100% after the transplant, down to no required insulin for the course of the 60-day study. The dogs had no adverse events and behavioral monitoring suggested normal activity after recovery from the transplant.

Conclusions and implications

The study provides evidence that PEGDA microencapsulated canine islets reversed the signs of diabetes without immunosuppression and led to states of insulin-independence or significantly lowered insulin requirements in the recipients.

Polyelectrolyte Multilayered Capsules as Biomedical Tools

Polyelectrolyte multilayered capsules (PEMUCs) obtained using the Layer-by-Layer (LbL) method have become powerful tools for different biomedical applications, which include drug delivery, theranosis or biosensing. However, the exploitation of PEMUCs in the biomedical field requires a deep understanding of the most fundamental bases underlying their assembly processes, and the control of their properties to fabricate novel materials with optimized ability for specific targeting and therapeutic capacity. This review presents an updated perspective on the multiple avenues opened for the application of PEMUCs to the biomedical field, aiming to highlight some of the most important advantages offered by the LbL method for the fabrication of platforms for their use in the detection and treatment of different diseases.