Engineering Surface-Functionalized, Intelligent Hydrogel Nanoparticles with Tunable Release Properties

Authors: 
Wagner, A., The University of Texas at Austin
Al-Sayyad, N., The University of Texas at Austin
Schroeder, A., The University of Texas at Austin
Peppas, N. A., University of Texas at Austin
The CDC estimates that 14 million people are diagnosed with cancer globally each year and 8 million die from the disease. Current treatment plans include chemotherapy, radiation, surgical removal of tumors, or, most often, a combination of those methods. However, current chemotherapeutic regimens do not distinguish between healthy and cancerous cells and typically lead to debilitating side effects. These dose limiting toxicities require patients to wait for long periods between treatments. During this time, any cancerous cells that have been exposed to the drug, but not killed, have an opportunity to recover from the treatment and become drug resistant. The use of nanoparticles as delivery vehicles has shown promise for enhancing the systemic delivery of chemotherapeutic agents and solving some of the limitations that conventional administration presents. Ultimately, localizing and controlling drug release at the disease site would offer advantages over the current chemotherapeutic regimens because it limits the toxicity to healthy tissues and decreases the side effects for the patient. Here, we have developed a novel, multi-stimuli responsive nanoscale hydrogels (nanogels) for the controlled, tumor-targeted delivery of multiple chemotherapeutic agents (CAs).

The nanogels are comprised of a: (i) cationic monomer, 2-(diethylamino)ethyl methacrylate, that imparts a pH-response by ionization of amine pendant groups, (ii) tetraethylene glycol dimethacrylate crosslinker to improve drug retention, (iii) n-alkyl methacrylate monomer to improve drug loading through CA-polymer interactions, and (iv) surface-grafted poly(ethylene glycol) or hyaluronic acid to impart serum stability. The impact of n-alkyl methacrylate monomer inclusion was investigated through systematic variation of monomer steric bulk and chain length. The physical properties of resulting nanogels were compared using dynamic light scattering, zeta potential, titration, pyrene fluorescence, and hemolysis as a function of pH to elicit the influence of polymer composition on swelling ratio, surface charge, pKa, hydrophile-hydrophobe phase transition, and cell membrane disruption capability. The therapeutic delivery potential of the nanogels was optimized and analyzed using paclitaxel and carboplatin.

Nanogel-mediated combination therapy offers many advantages including the ability to signal different pathways in the cancer cells, maximize the therapeutic efficacy against specific targets, target different phases of the cell cycle, and overcome efflux-driven mechanisms of resistance. Further, it allows PK/PD to be dictated by the in vivo distribution and cellular uptake of the nanogels rather than the physicochemical properties of free CAs, ensuring optimal synergistic ratios are delivered to the cytosol. We demonstrated that both the grafted monomer and hydrophobic monomer composition can be varied to enable precise control over the nanogel surface and core characteristics to enable effective, controlled delivery. The nanogel molecular architecture was rationally designed to entrap cargos with widely varying physicochemical properties and to release the cargo only in response to a specific environmental cue. Further, control over the nanogel functionalization was demonstrated, and the surface properties were optimized to avoid clearance mechanisms and increase circulation time while still maintaining the necessary characteristics to promote cellular uptake. Ultimately, the tunability of our multicomponent nanogel system can be exploited to enable long-circulation and effective transport of the drugs to the tumor site.