Rapid Fingerprinting of Urinary Volatile Metabolites\nand Point-of-Care Diagnosis of Phenylketonuria on a Patterned Nanorod\nSensor Array with Multiplexed Surface-Enhanced Raman Scattering Readouts

Phenylketonuria\n(PKU) is one of the most common genetic metabolic\ndiseases, especially among newborns. Traditional clinical examination\nof newborn blood samples for PKU is invasive, laborious, and limited\nto hospitals and healthcare facilities. We reported herein a SERS-based\nsensor array with three thiophenolic nanoreceptors built on a patterned\nnanorod vertical array for rapid and inexpensive detection of characteristic\nvolatile biomarkers indicative of PKU in the urine and accurate classification\nof newborn baby patients all performed on a hand-held SERS spectrophotometer.\nThe well-ordered array was generated from the volatility-driven assembly\nof gold nanorods (AuNRs) into an upright and closely packed hexagonal\nconfiguration. The uniformly distributed nanowells between AuNRs offered\nan intense and aspect-ratio-dependent plasmonic field for the molecular\nenhancement of SERS outputs. The SERS-based detector was integrated\ninto a test chip for regular monitoring of volatile phenylketone bodies\nin the spiked solution or patients’ urine within 5 min, allowing\nthe quantification of a wide variety of normal or abnormal metabolites\nat their physiologically relevant concentration range. The detection\nlimits for common biomarkers of PKU, including phenylpyruvic acid,\n4-hydroxyphenylacetic acid, and phenylacetic acid, were at a few μM\nand well below the diagnostic thresholds. Moreover, the volatile headspace\n mixtures from a given urine sample could be fingerprinted by the\nsensor array and discriminated using machine-learning algorithms.\nUltimately, the discrimination of baby patients among 26 cases of\nmild and classic PKU phenotypes and 17 cases of healthy volunteers\ncould be realized with an overall accuracy of 97%. This hand-held\nSERS platform plays a pivotal role in advancing healthcare applications\nin quick screening of neonatal PKU through a facile urinary vapor\ntest.