[Show abstract][Hide abstract] ABSTRACT: A main issue in controlled delivery of biotechnological products from injectable biodegradable microspheres is to preserve their integrity and functional activity after the microencapsulation process and final sterilization. The present experimental work tested different technological approaches to maintain the biological activity of an encapsulated biotechnological product within PLGA [poly (lactic-co-glycolic acid)] microspheres (MS) after their sterilization by gamma irradiation. GDNF (glial cell line-derived neurotrophic factor), useful in the treatment of several neurodegenerative diseases, was chosen as a labile model protein. In the particular case of optic nerve degeneration, GDNF has been demonstrated to improve the damaged retinal ganglion cells (RGC) survival.
No preview · Article · Jul 2012 · International Journal of Pharmaceutics
[Show abstract][Hide abstract] ABSTRACT: The present experimental work describes the use of a novel protein encapsulation method to achieve protection of the biological factor during the microencapsulation procedure. With this aim, the protein is included in poly(lactic-co-glycolic acid) (PLGA) microspheres without any preliminary manipulation, in contrast to the traditional S/O/W (solid-in-oil-in-water) method where the bioactive substance is first dissolved and then freeze-dried in the presence of lyoprotectors. Furthermore, the presented technique involves the use of an oily additive, vitamin E (Vit E), useful from a technological point of view, by promoting additional protein protection and also from a pharmacological point of view, because of its antioxidant and antiproliferative properties. Application of this microencapsulation technique has been performed for GDNF (glial cell line-derived neurotrophic factor) designed for the treatment of optic nerve degenerative diseases, such as glaucoma, the second leading cause of blindness in the western world. The protein was released in vitro in its bioactive form for more than three months, demonstrated by the survival of their potential target cells (photoreceptors and retinal ganglion cells (RGC)). Moreover, the intravitreal injection of GDNF/Vit E PLGA microspheres in an experimental animal model of glaucoma significantly increased RGC survival compared with GDNF, Vit E or blank microspheres (p<0.01). This effect was present for at least eleven weeks, which suggests that the formulation prepared may be clinically useful as a neuroprotective tool in the treatment of glaucomatous optic neuropathy.
No preview · Article · Jun 2011 · Journal of Controlled Release
[Show abstract][Hide abstract] ABSTRACT: The failure of the adult mammalian retina to regenerate can be partly attributed to the barrier formed by inhibitory extracellular matrix (ECM) and cell adhesion molecules, such as CD44 and neurocan, after degeneration. These molecules act to separate a sub-retinal graft from integrating into the host retina. It has been shown that matrix metalloproteinase 2 (MMP2) can promote host-donor integration by degrading these molecules. In order to enhance cellular integration and promote retinal repopulation, we co-transplanted biodegradable poly(lactic-co-glycolic acid) (PLGA) microspheres that have the ability to deliver active MMP2 with retinal progenitor cells (RPCs) to the sub-retinal space of adult retinal degenerative Rho-/- mice. Following delivery, significant degradation of CD44 and neurocan at the outer surface of the degenerative retina without disruption of the host retinal architecture was observed. Coincident with this, we observed a significant increase in the number of cells migrating beyond the barrier into the degenerative retina. No changes in the differentiation characteristics of RPCs were observed. Cells in the outer nuclear layer (ONL) could express the mature photoreceptor markers recoverin, make contacts with residual protein kinase C (PKC)-positive cells and express the ribbon synapse protein bassoon. Thus, co-transplantation of MMP2-PLGA microspheres with RPCs provides controlled release of active MMP2 to the site of retinal degeneration, stimulating inhibitory barrier removal and enhancing cell integration. This suggests a practical and effective strategy for retinal repair.