Solid polymeric microparticles enhance the delivery of siRNA to macrophages in vivo.

Therapeutics based on small interfering RNA (siRNA) have a great clinical potential; however, delivery problems have limited their clinical efficacy, and new siRNA delivery vehicles are greatly needed. In this report, we demonstrate that submicron particles (800-900 nm) composed of the polyketal PK3 and chloroquine, termed as the PKCNs, can deliver tumor necrosis factor-alpha (TNF-alpha) siRNA in vivo to Kupffer cells efficiently and inhibit gene expression in the liver at concentrations as low as 3.5 microg/kg. The high delivery efficiency of the PKCNs arises from the unique properties of PK3, which can protect siRNA from serum nucleases, stimulate cell uptake and trigger a colloid osmotic disruption of the phagosome and release encapsulated siRNA into the cell cytoplasm. We anticipate numerous applications of the PKCNs for siRNA delivery to macrophages, given their high delivery efficiency, and the central role of macrophages in causing diseases such as hepatitis, liver cirrhosis and chronic renal disease.

Acid-degradable protein delivery vehicles based on metathesis chemistry.

In this communication we demonstrate that acyclic diene metathesis (ADMET) polymerization is a powerful methodology for the synthesis of acid-degradable polymers based on polyketals and polyacetals. Ten new polyketals and polyacetals were synthesized, using ADMET, and a polyacetal based on anthracene aldehyde was identified, which had the physical properties needed for microparticle formulation. The antioxidant protein catalase was encapsulated into microparticles, formulated from this polyacetal, using a double emulsion procedure, and cell culture studies demonstrated that these microparticles dramatically improved the ability of catalase to scavenge hydrogen peroxide produced by macrophages. We anticipate numerous applications of ADMET for the synthesis of acid-degradable polymers based on its excellent tolerance toward functional groups and ease of synthesis.

Polyketal microparticles: a new delivery vehicle for superoxide dismutase.

There is currently great interest in developing microparticles that can enhance the delivery of proteins to macrophages. In this communication, we present a new acid-sensitive polymer for drug delivery, poly(cyclohexane-1,4-diyl acetone dimethylene ketal) (PCADK). PCADK is designed to hydrolyze, after phagocytosis by macrophages, in the acidic environment of the phagosome and enhance the intracellular delivery of phagocytosed therapeutics. Other key attributes of PCADK for drug delivery are its well-characterized degradation products and straightforward synthesis. PCADK hydrolyzes into 1,4-cyclohexanedimethanol, a compound used in food packaging, and acetone, a compound on the FDA GRAS list. PCADK was synthesized using the acetal exchange reaction between 1,4-cyclohexanedimethanol and 2,2-dimethoxypropane, and could be obtained on a multigram scale in one step. The hydrolysis kinetics of the ketal linkages in PCADK were measured by 1H NMR and were determined to be pH-sensitive, having a half-life of 24.1 days at pH 4.5 and over 4 years at pH 7.4. The therapeutic enzyme superoxide dismutase (SOD), which scavenges reactive oxygen species, was encapsulated into PCADK-based microparticles using a double emulsion procedure. Cell culture experiments demonstrated that PCADK-based microparticles dramatically improved the ability of SOD to scavenge reactive oxygen species produced by macrophages. We anticipate numerous applications of PCADK in drug delivery, based on its acid sensitivity, well-characterized degradation products, and straightforward synthesis.