title: Sustained polymeric delivery of gene silencing antisense ODNs, siRNA, DNAzymes and ribozymes: in vitro and in vivo studies.
abstract: Small interfering RNA (siRNA), antisense oligonucleotides (ODNs), ribozymes and DNAzymes have emerged as sequence-specific inhibitors of gene expression that may have therapeutic potential in the treatment of a wide range of diseases. Due to their rapid degradation in vivo, the efficacy of naked gene silencing nucleic acids is relatively short lived. The entrapment of these nucleic acids within biodegradable sustained-release delivery systems may improve their stability and reduce the doses required for efficacy. In this study, we have evaluated the potential in vitro and in vivo use of biodegradable poly (D,L-lactide-co-glycolide) copolymer (PLGA) microspheres as sustained delivery devices for ODNs, ribozyme, siRNA and DNA enzymes. In addition, we investigated the release of ODN conjugates bearing 5'-end lipophilic groups. The in vitro sustained release profiles of microsphere-entrapped nucleic acids were dependent on variables such as the type of nucleic acid used, the nature of the lipophilic group, and whether the nucleic acid used was single or double stranded. For in vivo studies, whole body autoradiography was used to monitor the bio-distribution of either free tritium-labelled ODN or that entrapped within PLGA microspheres following subcutaneous administration in Balb-c mice. The majority of the radioactivity associated with free ODN was eliminated within 24 h whereas polymer-released ODN persisted in organs and at the site of administration even after seven days post-administration. Polymer microsphere released ODN exhibited a similar tissue and cellular tropism to the free ODN. Micro-autoradiography analyses of the liver and kidneys showed similar bio-distribution for polymer-released and free ODNs with the majority of radioactivity being concentrated in the proximal convoluted tubules of the kidney and in the Kupffer cells of the liver. These findings suggest that biodegradable PLGA microspheres offer a method for improving the in vivo sustained delivery of gene silencing nucleic acids, and hence are worthy of further investigation as delivery systems for these macromolecules.
authors.affiliation: Centre for Genome-based Therapeutics, The Welsh School of Pharmacy, Cardiff University, UK.
authors.forename: Alim
authors.initials: A
authors.lastname: Khan
authors.forename: Mustapha
authors.initials: M
authors.lastname: Benboubetra
authors.forename: Pakeeza Z
authors.initials: PZ
authors.lastname: Sayyed
authors.forename: Keng Wooi
authors.initials: KW
authors.lastname: Ng
authors.forename: Stephen
authors.initials: S
authors.lastname: Fox
authors.forename: Gordon
authors.initials: G
authors.lastname: Beck
authors.forename: Ibrahim F
authors.initials: IF
authors.lastname: Benter
authors.forename: Saghir
authors.initials: S
authors.lastname: Akhtar
mesh_terms: D000818:Animals; D001345:Autoradiography; D021881:DNA, Catalytic / Q000008:administration & dosage* / Q000737:chemistry; D016503:Drug Delivery Systems; D005472:Fluorouracil / Q000008:administration & dosage / Q000493:pharmacokinetics; D020868:Gene Silencing; D066298:In Vitro Techniques; D007668:Kidney / Q000378:metabolism; D019344:Lactic Acid / Q000737:chemistry*; D008099:Liver / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008863:Microspheres; D016376:Oligonucleotides, Antisense / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000737:chemistry*; D016337:RNA, Catalytic / Q000008:administration & dosage* / Q000737:chemistry; D034741:RNA, Small Interfering / Q000008:administration & dosage* / Q000737:chemistry; D013154:Spleen / Q000378:metabolism; D013997:Time Factors
chemical_list: D021881:DNA, Catalytic; D016376:Oligonucleotides, Antisense; D011108:Polymers; D016337:RNA, Catalytic; D034741:RNA, Small Interfering; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D005472:Fluorouracil