Targeted drug delivery along with controlled drug release mechanisms have been of tremendous interest concerning the battle against cancer. Lipobeads – spherical bipartite nanoparticles consisting of a hydrogel core coated by a lipid bilayer – exhibit properties of mechanical stability and environmental responsiveness attractive for the drug delivery systems. This work is devoted to the synthesis and properties of the degradable under presence of reducing agents microgels, which could be used as the hydrogel core within lipobeads. Using the inverse suspension polymerization (ISP) method, “thermophilic” spherical microgels (~Ø10–300 µm), which swell upon heating, have been prepared via thermal polymerization of acrylamide and acrylonitrile as co-monomers along with either <i>N, N’</i>-bis(acryloyl)cystamine as a cross-linker with disulfide bridges or <i>N,N’</i>-methylenebis(acrylamide) without disulfide cross-links. In both cases, microgels were fluorescently labeled in order to characterize them under confocal microscope. Direct observations by confocal microscopy revealed the following properties of thus prepared microgels: (i) microgels without disulfide cross-links do not exhibit degradation, whereas microgels with disulfide cross-links exhibit degradation under presence of a reducing agent (dithiothreitol or glutathione); (ii) two steps of degradation are distinguished: microgel expands due to the reduction in cross-linking density and degrades due to outward diffusion of the cleaved polymer chains; (iii) kinetics of swelling and degradation was measured to conclude that the swelling is slower than the degradation; (iv) the extent and rates of degradation depend on pH and amount of a reductant added. These findings propose an avenue towards drug delivery systems that encapsulated drug molecules to release with the maximal rate within specified microenvironment of cancerous cells.

Disulfide cross-linked poly(acrylamide-co-acrylonitrile) microgels: Synthesis, properties, and de-cross-linking kinetics

ACS Spring Meeting 2021

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