Abstract
Abstract: :
Purpose: Study the tolerance, behavior and tissue localization of biodegradable polylactides (PLA) nanoparticles (NPs) after intravitreal injection in the rat eye. Methods: PLA NPs loaded with Nile red (NR) (310±40nm, Zeta potential -4.6mV) and PLA (PMMA-co-MA12) with Rhodamine 6G (Rh) (140±20nm, Zeta potential -60mV) were evaluated. Eighty-eight male Lewis rats received an intravitreal injection (10µl) of either NR or Rh NPs. Rats were sacrificed at various intervals starting one hour after the intravitreal injection and up to four months later. At each time point a minimum of 4 eyes were examined. One eye was snap frozen in OCT and used for immunohistochemistry analysis. One eye was preserved in 4% PAF for routine histology and ultrathin sections. Two eyes were processed for confocal microscopy. Inflammatory cells were identified using specific antibodies directed against OX42 and ED1 antigens. RPE and glial cells were identified using specific antibodies against Cytokeratin and GFAP antigens. To assess the in vivo effects on retinal function, ERG analysis were carried out . Results: During the first hour after intravitreal injection, the injected NPs are observed only in the vitreous or on the retinal internal limiting membrane. Six to 12 hours after injection, NPs were detected within the ROP layer in an apparent transretinal movement posteriorly. At 24 hours NPs are seen in the RPE cell layer. Later, a gradual increase in the number of NPs within RPE cells is recorded. It is of interest that loaded NP's are observed within the RPE cells up to 4 months after injection. PLA NPs induced a transient inflammatory reaction up to 48 hours after the injection but not later. Histology analysis of semi-thin and ultrathin sections demonstrated that the integrity of all intraocular tissues was preserved. Furthermore, ERG's responses of eyes injected with loaded or blank NP's remained unaltered. Conclusions: NPs injected into the vitreous of the rat eye do follow a transretinal pathway to accumulate in the RPE cells. These observations may be used as the basis for a wide range of future therapeutic avenues.
Keywords: 567 retinal pigment epithelium • 471 microscopy: confocal/tunneling • 436 injection