(403c) Self-Assembled Gold Nanoparticles Embedded in Conductive and pH-Sensitive Nanocomposite Hydrogel

Intelligent biomaterials that alter their function through sensing local molecular cues may enable technological advances in the fields of drug delivery, actuators, artificial muscles, and biosensors. We have synthesized a series of biocompatible, polymeric matrices that couple a stimuli-induced volume change with conductivity. The hydrogel is comprised of dithiolated poly(N,N-dimethylaminoethyl methacrylate) (dT-DMAEMA) and 2-hydroxyethyl methacrylate (HEMA). dT-DMAEMA was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization using a difunctional chain transfer agent. The thiol groups have affinity to both colloidal gold (Au) and Au3+ ions in the hydrogels. Embedded gold nanoparticles percolate when the gel is not swollen. Expansion of the gel under acidosis results in an increase in the interparticle distances (and decrease in the volume fraction) of the gold nanoparticles. Changes in the volume fraction of gold nanoparticles leads to changes in matrix conductivity. Gold nanoparticles (2-5nm) were homogeneously distributed in dT-DMAEMA/HEMA hydrogels as confirmed by transmission electron microscopy. High swelling rates and conductivity are achieved with high content of dT-DMAEMA, low crosslinking density, and low pH. We characterized the materials' conductivity, swelling ratio and matrix elasticity as a function of pH. The conductivity of the matrix may be tailored by altering the particle size, initial volume fraction, and the stimuli-responsive characteristics of the matrix. The conductivity and pH sensitivity of nanocomposite hydrogels in this research can be useful for needs to acidic conditions for a various applications including pH-sensitive actuators, biosensors, microfluidic devices, and drug delivery devices.