| Background: Endophthalmitis, a bacterial infection of the eye, may result in loss of sight. Although intravitreal injection becomes the routin treatment of endophthalmitis, it may associated with several other problems, for example, drug concentration decreases fast after a single injection while multi-injections must be repeated to maintain the drug level within a therapeutic range. Poly(N-isopropylacrylamide)- polyethylene oxide(PNIPAAm-PEO)is a new kind of synthetical polymerizer,it is a smart drug delivery material due to its unique phase separation behavior upon external temperature changes. As a newly designed drug delivery system, PNIPAAm-PEO for the research in the field of ophthalmology has not been reported.Purpose: (1) to investigate the therapeutic effects of an intravitreal norvancomycin-loaded poly(N-isopropyl acrylamide)-polyethylene oxide drug delivery system(NV-PNIPAAm-PEO)on a rabbit model of mixture-infectious bacterial endophthalmitis.(2) to evaluate ocular toxicity of intravitreal norvancomycin-loaded poly(N-isopropyl acrylamide)-polyethylene oxide drug delivery system(NV-PNIPAAm-PEO)on rabbitsMethods: (1) in order to observe the effects of NV-PNIPAAm-PEO, 50 new Zealand albino rabbits were received an intravitreal injection of mixed bacterial suspension. After therapy 24 hours, all models were randomly divided into 5 groups. Group A: the empty control group, treat nothing after bacterial suspension injection, group B : intravitreal injection of the empty drug delivery system 2mg/0.1ml, group C: intravitreal injection of sterilized saline 0.1ml, group D: intravitreal injection of norvancomycin 0.44mg/0.1ml, group E: intravitreal injection of NV-PNIPAAm-PEO 2mg/0.1ml. The clinical observation, B-scan ultrasonography and histopathological examination were performed at time points of 1, 2, 3, 7, 14, 21, 28, 42 d after operation.(2)in the ocular toxicity study , 20 New Zealand albino rabbits were randomly divided into 2 groups. Group A received intravitreal injection of NV-PNIPAAm-PEO 2mg/0.1ml , and Group B received 0.1 ml sterilized Saline. The clinical observation, electeoretinography and histopathological examination were performed at time points of before operation 1 d and 1, 2, 3, 7, 14, 21, 28, 35, 42 d after operation.Results: (1) The inflammation response was lower in groups D, E than groups A , B and C(P<0.005). There was no significant statistical difference between group A, B and C. After 3 weeks, the inflammation response of vitreous body was lower in groups E than groups D (P<0.005). While group E shows normal, the B-scan ultrasonography indicated that mild vitreous opacity in group D after 3 weeks, and the lymphocyte and plasma cells were observed at the posterior pole via pathological examination.(2) All eyes showed normal via clinical observation, and electeoretinography and histopathological examination did not found significant changes in both groups.Conclusions: (1)The norvancomycin drug delivery system can effectively suppress the inflammation of the rabbit model of mixture-infectious bacterial endophthalmitis.(2) The norvancomycin drug delivery system has no significant ocular toxity at the treatment dose(2mg) . |
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