Combination of Coordination and Releasable Covalent Binding for the Delivery of Antisense Therapeutics by Bisphosphonate-Hyaluronan-Oligonucleotide Conjugates

Abstract

To address the current problems of delivery of antisense oligonucleotide (ON) therapeutics, a macromolecular platform was proposed based on the combination of metal-ion coordination and releasable covalent conjugation. Two kinds of therapeutic molecules, bisphosphonate (BP) and antisense ON, were conjugated to a natural polysaccharide hyaluronic acid (HA). The use of two linkers with a set of terminal chemoselective groups including N-hydroxysuccinimide carbonate, 2-dithiopyridyl, and aromatic aldehyde allowed orthogonal conjugation of the two therapeutics with subsequent detachment under potentially different conditions. In this work, disulfide linkages of varied steric accessibility were utilized in the linkers allowing the release of the linked therapeutics with different kinetics upon incubation in a reducing buffer. The therapeutics were conjugated to HA via their amino groups, and the self-immolative feature of the linkers permitted traceless release of both drugs as free amines. The obtained dual macromolecular prodrug was converted into either nanogels or macroscopic hydrogels upon coordination with calcium ions via Ca2+-mediated bridging of BP groups. Macroscopic hydrogels demonstrated self-healing properties which are useful for the noninvasive administration of ONs as biodegradable implants. Moreover, transformation of the macromolecular prodrug into a nanogel under dilute conditions is a useful property to prolong the circulation of the prodrug and protect antisense ON therapeutics against degradation in vivo.