Enhancement of poly(orthoester) microspheres for DNA vaccine delivery by blending with poly(ethylenimine)

Abstract

Poly(ortho ester) (POE) microspheres have been previously shown to possess certain advantages for the in vivo delivery of DNA vaccines. In particular, timing of DNA release from POE microspheres in response to acidic phagosomal pH was shown to be an important factor in determining immunogenicity, which was hypothesized to be linked to the natural progression of antigen presenting cell uptake, transfection, maturation, and antigen presentation. Here we report in vitro characterization of the enhanced the efficacy of POE microspheres by blending poly(ethylenimine) (PEI), a well-characterized cationic transfection agent, into the POE matrix. Blending of a tiny amount of PEI (approximately 0.04 wt%) with POE caused large alterations in POE microsphere properties. PEI provided greater control over the rate of pH-triggered DNA release by doubling the total release time of plasmid DNA and enhanced gene transfection efficiency of the microspheres up to 50-fold without any significant cytotoxicity. Confocal microscopy with labeled PEI and DNA plasmids revealed that PEI caused a surface-localizing distribution of DNA and PEI within the POE microsphere as well as focal co-localization of PEI with DNA. We provide evidence that upon degradation, the microspheres of POE-PEI blends released electrostatic complexes of DNA and PEI, which are responsible for the enhanced gene transfection. Furthermore, blending PEI into the POE microsphere induced 50% to 60% greater phenotypic maturation and activation of bone marrowderived dendritic cells in vitro, judged by up-regulation of co-stimulatory markers on the cell surface. Physically blending PEI with POE is a simple approach for modulating the properties of biodegradable microspheres in terms of gene transfection efficiency and DNA release kinetics. Combined with the ability to induce maturation of antigen-presenting cells, POE-PEI blended microspheres may be excellent carriers for DNA vaccines.

Single-injection vaccines: Progress, challenges, and opportunities

“…Depending on formulation and chemical composition, these materials can be tuned to achieve continuous or delayed/pulsatile release kinetics [71,72]. However, to date these materials have only been studied for releasing model proteins or DNA, and not for clinically available vaccine antigens [72][73][74].…”

Polymer-Based DNA Delivery Systems for Cancer Immunotherapy

“…A key advantage of particulate vectors relative to other non-viral gene delivery systems is their superior in vivo stability. The principal types of polymers studied in this context include those made of poly(lactide) (PLA; reviewed in [ 99 ]), poly(lactide-co-glycolide) (PLGA; reviewed in [ 99 , 100 , 102 ]), polyorthoesters [ 103 ], polystyrene (PS) [ 104 , 105 ] and poly(ε-caprolactone) [ 106 ]. Of these, PLGA has been studied most extensively in terms of its capacity to stimulate APCs.…”

Biodegradable polymers for dental tissue engineering and regeneration

“…POE are hydrophobic, with surface eroding degradation and controllable backbone chemistry that allows the synthesis of polymers with varied acid-catalyzed degradation rates and properties. In particular, POE incorporating short segments of lactic or glycolic acid into the polymer backbone, in order to expedite degradation, are used for the delivery of analgesics [225], DNA vaccines [226], and antiproliferative drugs [227]. However, POE capacity to be used as tissue engineering scaffolds is limited by their weak mechanical properties and the induction of a mild to moderate inflammatory response [228].…”