Abstract
Purpose: :
Gene and drug delivery to ocular tissues including retina and cornea is hampered by inefficient transport of therapeutic molecules across the plasma membrane. We hypothesized whether molecules including DNA, siRNA, drugs, fluorophores, proteins, antibodies and quantum dots conjugated to a peptide that penetrates the cell plasma membrane may allow efficient delivery of these molecules to ocular tissues including retina and cornea.
Methods: :
Based on molecular modeling of heparin-binding regions of acidic fibroblast growth factor (FGF) and basic FGF, we designed a variety of peptides and tested them for the ability to translocate across the cell plasma membrane. One such peptide refered to as 'peptide for ocular delivery' or POD was comprised of the amino acid sequence CGGG(ARKKAAKA)4. POD was conjugated to a variety of molecules and delivered to mice either subretinally, intravitreally or applied topically to the cornea. Kinetics of cell plasma membrane translocation and toxicity of POD in human embryonic retinoblasts was also characterized .
Results: :
Upon subretinal delivery, POD entered the photoreceptors and retinal pigment epithelium within 20 min without any significant toxicity. Upon intravitreal delivery, POD localized to the ganglion cells and inner nuclear layers of the retina, in addition to trabecular meshwork and lens epithelium. Topical application of POD to murine cornea led to uptake of POD by the corneal epithelium, sclera, choroid and surprisingly also the optic nerve dura. In human embryonic retinoblasts (HER) in culture, POD was taken up by 92.23% of cells within 5 min. Uptake of POD was energy and temperature dependent and did not disrupt the cell plasma membrane. Uptake of POD could be blocked by pre-incubation of cells with proteoglycans. POD could compact and deliver plasmid DNA to > 56% of HER cells. POD could also compact and deliver siRNA to HER cells at levels sufficient to silence CMV promoter driven GFP expression by >50%. Finally, POD also functions as a bacteriostatic, significantly inhibting growth of bacterial colonies at concentrations as low as 0.3 micro moles.
Conclusions: :
POD may be a useful gene, drug and protein delivery vehicle for retinal and corneal cells in vitro and in vivo. In addition, the bacteriostatic property of POD makes it an ideal drug delivery vehicle for ocular diseases associated with bacterial infections.
Keywords: gene transfer/gene therapy • retina • cornea: epithelium