Affinity Biosensors For Phenylketonuria Diagnosis: A Review of Bioreceptors and Transducers Strategies

Abstract

Phenylketonuria (PKU) is an inborn error of metabolism which arises from the mutations in phenylalanine hydroxylase (PAH) gene. PAH enzymes hydroxylate phenylalanine to tyrosine in the presence of the cofactor tetrahydrobiopterin (BH4), molecular oxygen and iron. Mutations in PAH gene led to lack of one of the essential enzymes, phenylalanine hydroxylase (PAH). Lack of this crucial enzyme brings about the accumulation of L-phenylalanine and their metabolites in the newborns’ blood, urine and other body fluids, causing skin lesions, epilepsy, microcephaly, eczema, and scleroderma and, if untreated, also cause mental retardation. The amount of serum phenylalanine of healthy individual, is expected to be measured in the range of 50-110 μM, while phenylalanine in phenylketonuria patients is in the range of 0.6-3.8 mM in serum and 20-60 mM in urine. Metabolic diseases such as phenylketonuria are rare diseases but these types of illness reduce the quality of life at serious levels. If these diseases can be diagnosed early by the help of detection methods, mortality and morbidity can be prevented. For this reason, early diagnosis of metabolic diseases provides a better quality of life for the patients. Today, phenylketonuria could be determined using microbial inhibition, chromatographic and spectrophotometric methods. In Turkey, phenylketonuria test is performed by colorimetric method in screening centers. However, since these methods are time-consuming and expensive, complex instrumentation, preliminary preparation and special laboratory facilities are needed, the need in this area cannot be fully met. For this reason, there is an urgent need to develop simpler, faster and more economical assay methods and make them readily available at the clinic. For this reason, the development of new techniques and/or devices is a great need to be addressed urgently. In this context, use of affinity biosensors which are known with their sensitivity, selectivity, low cost and rapid response, to the following of phenylketonuria disease will ensure that these disadvantages are overcome. This review aims at presenting the bioreceptors to selectively and sensitively diagnose phenylketonuria by using different transducers in affinity biosensors.