Thermoresponsive and Biodegradable Dextran Based Microgels: Synthesis and Structural Investigation

Abstract

Nanostructured objects, often ranging from hundreds of nanometers to few microns, support a number of functions directly linked to their structural features. They are, or they will be, protagonists in biomedical applications where miniaturized activities are required. These include the interface with living systems as tissues and cells, where targeted release of drug molecules occurs, or molecular imaging methods monitoring the drug trafficking in specific cell districts. The potentials of such devices, far to be fully understood, will be assessed only when a close correlation of their functions with their structure will be established.\ud \ud In this contribution we present a dextran based microdevice responsive to temperature and biodegradable. Both thermoresponsivity and biodegradability are of relevance for the potential use as drug carrier and controlled release device. The temperature behaviour, overall structure and internal architectures have been addressed with different methods

Temperature-Induced Assembly of Monodisperse, Covalently Cross-Linked, and Degradable Poly(N-isopropylacrylamide) Microgels Based on Oligomeric Precursors

“…Diacrylate cross-linkers containing disulfide linkages have been used to prepare degradable microgels based on PVCL and POEGMA. , Analogous strategies using polyvinylalkoxysiloxanes, which degrade at basic conditions, or acetal groups, which hydrolyze in acidic conditions, have also been used to prepare thermoresponsive microgels that are degradable. Alternately, degradability can be introduced by including degradable polymeric units directly into the microgel structure; for example, dextran- co -NIPAM microgels have been reported which can be degraded over time via oxidation and/or enzymatic degradation of the dextran component. , However, if the goal is to ensure the ultimate clearance of the degradation products, the use of degradable cross-linkers is inherently limited in that the molecular weight of the C–C backbone is not directly controllable using such an approach. While inclusion of chain transfer agents and/or controlled polymerization approaches (particularly reversible addition–fragmentation chain transfer polymerization, RAFT − ) can limit the molecular weight of the backbone, such approaches introduce additional complexity to the synthesis and, in the case of RAFT, may also limit the type of microgel functionalization that is possible directly in the context of the polymerization process.…”