Electrochemical Determination of Naloxone Using Molecularly Imprinted Poly(para-phenylenediamine) Sensor

A molecularly imprinted polymer (MIP)-based electrochemical sensor featuring an electrochemically grafted para-phenylenediamine functional monomer on a reduced graphene oxide-gold nanoparticles composite modified screen printed electrode is reported. The morphology and properties of the sensing material were characterized with microscopy, spectroscopy and electrochemical techniques. A number of factors affecting the performance of the MIP sensor were examined and optimized. Under an optimized condition, the imprinted electrochemical sensor yielded homogenous naloxone binding sites with a dissociation constant of 8.6 μ M, and responded linearly up to 8 μ M naloxone, with a limit of detection of 0.16 μ M. The sensor showed good run-to-run repeatability and batch-to-batch performance reproducibility with relative standard deviation of 5.7%–9.6% (n = 4) and <9% (n = 3), respectively. The imprinted sensor retained 95% and 85% of its performance when stored at ambient conditions for one and two weeks, respectively, demonstrating the sensor’s good stability. Selectivity experiments showed that both the MIP sensor and non-imprinted polymer electrode had minimal response (<25%) to equal concentrations of structurally similar compounds such as morphine, naltrexone and noroxymorphone, indicating good selectivity of the MIP sensor towards naloxone. The MIP sensor was successfully used to quantify naloxone in artificial urine samples, yielding recoveries greater than 92%.