Evaluation of biological safety of silicon membrane embedded permanent magnets implanted in canine / 第二军医大学学报

ABSTRACT

Objective To investigate the biological safety of silicon membrane embedded permanent magnets implanted into canine, so as to evaluate the safety of a micturition alert device designed on the principle of compass. Methods Twelve adult male dogs (weighing 11-12 kg) were divided into experimental group (8 dogs) and control group (4 dogs ). The experimental group was implanted with a silicon membrane embedded NdFeB magnet, which was 10 mm in diameter and 3 mm in thickness and with a magnetic induction intensity of 0. 3 Tesla at the center of the pole face surface. The control group was implanted with a silicon membrane embedded NdFeB alloy with the same dimensions. The grafts were sutured onto the anterior surface of the bladder wall. The dogs were then allowed to live for one year. Both the survival and local pathology around the grafts were observed after implantation. And the pre-operation urine and post-operation urine were compared between the two groups. Results One dog in the experimental group died from operation complications 10 hours after operation, another dog had intestinal obstruction 3 weeks after operation because iron wires in the intestinal tract was caught up by the permanent magnet. The rest 6 dogs in the experimental group and 4 dogs in the control group had no abnormalities in spirit, appetite, urine or stool, and there were no infections. The animals were sacrificed one year after operation. Adhension was found between the epiploon and the bladder wall around permanent magnets in these 10 dogs; the fibrous capsule around the permanent magnets was thin, and the local bladder wall below permanent magnets was thickened, with normal bladder mucosa. Grade 2 inflammatory reaction and fibrous capsule of the local tissue were noted around the grafts. The findings of urine routine were normal before and after operation. Conclusion NdFeB permanent magnets embedded with silicon membrane are biologically safe for clinical application, which warrante further investigations.