Effect of crosslinking density on thermoresponsive nanogels: A study on the size control and the kinetics release of biomacromolecules

Abstract

Thermoresponsive nanogels emerged as a robust and efficient platform for the delivery of a number of therapeutic agents. The need to deliver a wide range of biomolecules from different sizes requires a structural system with the ability to be tuned according to the specific applications. In this study, we design a library of nanogels using dendritic polyglycerol (dPG) as a crosslinker and poly (N-isopropyl acrylamide) as connecting thermoresponsive chains. Nanogels with diameters in a range of 70–210 nm were obtained by precipitation polymerization with low polydispersity. We provide a detailed study on how the flexibility of the network and size of the nanogels can be tuned by the modification of functionalities of the dPG, monomer feed and the size of the crosslinker. Additionally, we use different molecular weight proteins (6–66 kDa) as an indicator of the density of the structure by encapsulation and release experiments. We prove that the versatility of the system relays on the correct design of the nanogels and the careful selection of the starting materials and its final proportion in the reaction. By controlling the network density, a wider range of application can be achieved from a system with a short-term release triggered by temperature to a long-term release that could serve as reservoir platform.