(673j) Tuning Rheological Behavior of Polymer-Nanoparticle Hydrogels for Injectable Drug Delivery

Physically crosslinked hydrogels are promising materials for injectable prolonged delivery platforms. An appropriate hydrogel for injectable delivery should meet several performance requirements, which include, but are not limited to, low high shear viscosities to decrease injection pressures, yield stresses to prevent settling, and fast gelation kinetics to prevent burst release. Understanding structure-property relationships of physically crosslinked hydrogels will enable the design of their properties (i.e. shear-thinning and yield stress) to meet the performance requirements and is critical for engineering effective drug delivery platforms. Here, we explore structure-property relationships of polymer-nanoparticle hydrogels made from hydrophobically-modified hydroxypropylmethylcellulose (HPMC) and poly(ethylene glycol)-b-poly(lactic acid) nanoparticles (NPs). Increasing the hydrophobicity of the HPMC modification imbues HPMC-NP hydrogels with a yield stress. We also report the effects of each hydrophobic modification on the linear and non-linear viscoelasticity, flow behavior, and gelation kinetics. Lastly, we explore how the hydrophobic modifications to the HPMC-NP hydrogels can be exploited for designing injectable material platforms which require tunable viscosities and shear-thinning behavior to meet injectability performance requirements.