From catalysis to diagnostics and targeted drug delivery, new and exciting applications in nanotechnology have emerged over the past two decades. Because of their distinctive features—an incredibly high surface area to volume ratio for catalytic reactions, in addition to their capacity for carrying drugs and imaging agents—nanoparticles have provided novel solutions to many industrial and healthcare challenges.
Their potential notwithstanding, polymeric nanoparticles in use today are often non-biodegradable, which means that they accumulate in the environment and eventually enter the food chain. Preparing ultra-small nanoparticles in the sub-30 nanometer size range can also prove extremely challenging, with current methods (such as self-assembly) resulting in nanoparticles in the 100-nanometer size range or larger.
A rising interest in biodegradable and ultra-small nanoparticles due to their intriguing similarity with natural systems like proteins and other biological molecules inspired researchers at A*STAR’s Institute of Chemical and Engineering Sciences (ICES) to turn to single-chain technology, a method of synthesizing nanoparticles with a high level of precision that allows for individual copolymer chains to be folded and collapsed into single-chain nanoparticles. This method gives rise to ultra-small nanoparticles that are sub-30 nanometer in size.
“Our approach is experimentally robust and a straightforward route for the preparation of degradable single-chain nanoparticles,” said the lead investigator of the study, Praveen Thoniyot, a Senior Scientist and Team Leader at ICES. “Since the linear polymer precursor is prepared under free-radical conditions, it is easy to introduce a very large number of functionalities compared to other polymerization methods.”
Starting with a degradable linear polymer precursor containing cyclic ketene acetal-derived ester moieties and cross-linkable functional groups throughout the chain, the nanoparticles were formed via intramolecular chain folding and cross-linking. The degree of chain folding corresponded to the quantity of diamine cross-linker added for amide bond formation, while degradation into branched oligomers was attained through main-chain ester hydrolysis. Thoniyot and colleagues confirmed that they produced single-chain nanoparticles via light scattering and size-exclusion chromatography.
Due to their small diameters and higher diffusion rates compared to larger conventional nanoparticles, degradable nanoparticles have great potential to be used in a variety of applications including catalysis, nanoreactors, sensing and nanomedicine, said co-corresponding author Alexander William Jackson, a Scientist at ICES.
“Sustainability is a key driver of all technological innovations today,” added Thoniyot. “Non-degradable and environmentally persistent polymer nanoparticles are harmful to the biosphere. Introducing degradability into polymer chains can be one of the first steps towards achieving true sustainability.”
The A*STAR-affiliated researchers contributing to this research are from the Institute of Chemical and Engineering Sciences (ICES).