Optical-based bioanalytical assays for drugs quality control and diagnostic applications

Driven by the interest in the design of easy-to-use, low-cost and fast-response diagnostic devices that ensure continuous monitoring of the patient's health, this work aims to the development of innovative and alternative optical-based bioanalytical assays. The easiness to use, the non-destructive features, as well as the possibility of label-free approaches for direct optical detection, render optical methods a powerful tool for bioanalytical investigations. In these last, more frequently is necessary to determine small quantities of the analyte. For this purpose, photoluminescence properties of a class of nanomaterials (copper nanoclusters) and of a novel fluorophore, derived from serotonin self-oxidation, were respectively applied for the sensitive detection of human serum albumin and Cu(II) in human samples. These optical-based bioanalytical approaches could represent a valid alternative for an early diagnosis of albumin and copper-dependent diseases. Optical-bioanalytical detection strategies were also applied for drugs active principles estimation. The design of methods for pharmaceutical analysis for the drugs quality control, that is the unambiguous detection of a drug in a pharmaceutical product, is as crucial as its determination in complex matrices, since the pharmaceutical product quality is directly related to the patient’s health. Colorimetric methods, here, were applied for the determination of two active principles in commercial Parkinson’s drugs, levodopa, and carbidopa. Levodopa was quantified by exploiting a colorimetric reaction that leads to the purple melanochrome formation, here isolated and stabilized for the first time. The designed melanochrome-based colorimetric assay was effectively applied to levodopa and dopamine detection in human urinary samples, paving the way for future application in the monitoring of pharmacological therapy in Parkinson’s patients. Carbidopa content was also determined in pharmaceutical formulation by using an alternative colorimetric approach based on the selective condensation reaction between the hydrazine group of carbidopa and the formyl functional group of vanillin leading to the formation of yellow 4-hydroxy-3-methoxybenzaldazine. The novel optical-based bioanalytical approaches designed in this research work could have a significant impact on analytical diagnostic tools commonly employed in clinical practice and pharmaceutical analysis improving their availability and applicability.