Comparative Assessment of Bioavailability and Toxicity of Zinc Nanoparticles in Animal Model

Abstract

Zinc is an important micronutrient having multiple biological roles. Being integral components of more than 300 enzymes of all six classes and various transcription factors, it plays vital role in cellular signaling and functioning especially in immune cells and hepatocytes. Zinc in various form have been used for various pathological conditions like Wilson’s disease, common cold, hepatic malfunctions and acrodermatitis enteropathica. The main problem in zinc supplementation/therapy is its erratic bioavailability and pharmacokinetics. The main site for zinc absorption is jejunum. Various cellular zinc transporters play a significant role in zinc absorption. These transporters proteins are greatly affected by other dietary divalent cations e.g. calcium, iron, and magnesium. Furthermore, administrations of higher amount of zinc results in the saturation of these transporters. Nanotechnology has been applied in pharmaceutical sciences to enhance the bioavailability and cellular uptake of various drugs. Zinc oxide nanoparticles were developed to overcome this problem, but these formulations were linked to oxidative stress in the experimental animals. To address the problem efficiently, current study was designed to prepare zinc sulfate nanoparticles to avoid oxidative stress with enhanced bioavailability. Zinc nanoparticles were prepared using zinc sulfate nanoparticles by inotropic gelation method and characterized using scanning electron microscope (SEM) and zetasizer. Sprague Dawley Rats (n=27) were equally divided into three groups receiving: zinc sulfate nanoparticles (4 mg/Kg); plain zinc sulfate (4 mg/Kg) and normal saline to keep in account the diurnal variation. All the drugs were administered orally. Blood samples (0.3 to 0.5 ml) were collected randomly from tail vein at 0, 0.5, 1, 2, 4, 6, 8, 12, 24, 36, 72 and 120 hours from three animals in each group. After separating the plasma, samples were processed and analyzed for concentration of zinc by atomic absorption spectroscopy. Plasma zinc concentrations thus obtained were analyzed by one-way analysis of variance (ANOVA) with Duncan test for multiple comparisons. The plasma concentration vs time curve was used to calculate half-life, Cmax, tmax, AUC (0 to t), clearance and mean residual time by PK solver software using noncompartment model. For safety/toxicity studies albino mice (n=54) were randomly segregated into six groups: group I received normal saline (control); group II received plain zinc sulfate (40 mg/kg); group III received zinc oxide nanoparticles (40 mg/kg). while group IV, V and VI received 2 mg/kg, 4 mg/kg and 40 mg/kg of zinc sulfate nanoparticles respectively through gavage daily for 21 days. Food and water were provided ad libitum. Blood sample (approximately 1 ml) was collected from three animals in each group weekly for hematological examination and clinical chemistry. Liver, kidney and lungs were isolated form the decapitated animals and processed for histopathological examination. Results of study showed significant rise in plasma zinc concentration in animal receiving zinc sulfate nanoparticles than that of plain zinc sulfate after 1 hour of administration of zinc nanoparticles (p<0.05). The increase was remained significant till the end of the study (120 hours). Furthermore, significant rise in Cmax, AUC0-t and mean residual time were recorded in animal receiving the zinc nanoparticles. Moreover, data of studies showed improvement in bioavailability and pharmacokinetics parameters of zinc in nanoparticles formulation as compared to conventional zinc preparation. Animals given zinc oxide nanoparticles indicated significant rise in bilirubin, ALT, AST, ALP and creatinine level than that of animals received normal saline (group I). Whereas, significant decline was observed in serum total protein level was observed in these animals than animals of the group I. Moreover, sever degenerative changes in liver, kidney and lungs were present in these animals. However, animals receiving zinc nanoparticles didn’t indicate such degenerative changes. The Serum and hematological profile of these animals are comparable with animals receiving plain zinc sulfate. It is concluded from findings of the study that orally administered zinc sulfate nanoparticles has significantly increased the bioavailability of zinc and appear to be less toxic as compared to zinc oxide nanoparticles.