Development of a sustained-release biodegradable polymer delivery system for site-specific delivery of oligonucleotides: characterization of P(LA-GA) copolymer microspheres in vitro.
Development of a Sustained-Release Biodegradable Polymer Delivery System for Site-Specific Delivery of Oligonucleotides: Characterization of P(LA-GA) Copolymer Microspheres In Vitro Antisense oligodeoxynucleotides (ODNs) can selectively inhibit individual gene expression provided they gain access to and remain stable at the target site for a sufficient period of time. Biodegradable sustained-release delivery systems may facilitate site-specific delivery and also prevent degradation of ODNs by nucleases whilst delivering the nucleic acid in a controlled manner to the desired site of action. In this study, we have characterized biodegradable poly (lactide-co-glycolide) (P(LA-GA)) 50:50 microspheres for the potential delivery of antisense oligonucleotides in vivo. Phosphodiester (PO) oligonucleotides complementary to either c-myc proto-oncogene or the tat gene in HIV-RNA were adequately incorporated within P(LA-GA) microspheres with entrapment efficiencies up to 60% depending on particles size. In vitro release profiles of antisense nucleic acids from 10-20 microm size microspheres over 56 days in physiological buffer were triphasic. Profiles were characterised by an initial burst effect during the first 48 hours (phase 1) of release followed by a more sustained release (phase 2) with an additional increased release (phase 3) being observed after 25 days which corresponded with bulk degradation of the copolymer matrix. The release profiles were influenced by microsphere size, copolymer molecular weight, ODN loading, ODN length and by the pH of release medium used. The serum stability of PO ODNs was significantly improved when entrapped within P(LA-GA) microspheres and the hybridization capability, as assessed by duplex melting (Tm) measurements, of released ODN was not impaired by the double-emulsion microsphere fabrication procedure used. Thus, P(LA-GA) microspheres appear to be promising candidates for improving site-specific delivery profiles for ODNs and are worthy of further evaluation in vivo.
Lewis
K J
KJ
Pharmaceutical Sciences Institute, Aston University, Birmingham, UK.
Irwin
W J
WJ
Akhtar
S
S
D001483:Base Sequence; D004337:Drug Carriers; D016503:Drug Delivery Systems; D015696:Gene Products, tat / Q000235:genetics; D015497:HIV-1 / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid; D008863:Microspheres; D009693:Nucleic Acid Hybridization; D016376:Oligonucleotides, Antisense / Q000008:administration & dosage* / Q000737:chemistry; D010316:Particle Size; D011100:Polyglycolic Acid; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers; D000090063:Proto-Oncogene Mas; D054322:tat Gene Products, Human Immunodeficiency Virus
D004337:Drug Carriers; D015696:Gene Products, tat; C000715470:MAS1 protein, human; D016376:Oligonucleotides, Antisense; D011108:Polymers; D000090063:Proto-Oncogene Mas; D054322:tat Gene Products, Human Immunodeficiency Virus; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid