Detection of L-Tyrosine by electrochemical method based on binary mixed CdO/SnO₂ nanoparticles

Highlights

• CdO/SnO₂ nanoparticles prepared by facile wet-chemical method.

• Highly sensitive in-situ L-tyrosine sensor by reliable electrochemical method.

• L-tyrosine-sensor exhibits the lower detection limit within short response time.

• Practically validated the real biological serum samples.

• Effective L-tyrosine -sensor for health care and biomedical fields.

Abstract

Here, the nanoparticles (NPs) of CdO/SnO₂ were prepared by co-precipitation method in alkaline phase at low temperature. The characterization of CdO/SnO₂ NPs were analyzed by X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) analysis. To fabricate the sensor, glassy carbon electrode (GCE) was coated by CdO/SnO₂ NPs with 5% nafion suspension. The resulted sensor was applied to detect L-Tyrosine (L-Tyr) in buffer phase. A linear relation current versus concentration known as calibration curve was made. The sensor sensitivity (11.848 µA µM⁻¹ cm⁻²) is calculated from the slope of calibration curve. Recognizing the maximum linear region in calibration curve (regression coefficient R² = 0.99), the linear dynamic range (0.1 nM–0.01 mM) is used. Finally, the lower limit of detection (97.93 ± 4.89 pM) is estimated by applying the signal to noise ratio of 3 from the calibration curve. During the sensing performances, it was found as reliable, reproducible and long-term stable sensor and validated to detect the real biological samples by electrochemical approach in room conditions.

Introduction

In this approach, L-Tyr is an nonessential amino acid, chemically known as 4-hydroxyphenylalanine and used by human body cell to produce protein biologically [1], [2]. It is a normal biochemical process in human to synthesis of L-Tyr from phenylalanine, but the individual with phenylketonuria prevents the metabolism of phenylalanine to L-Tyr [3], [4] and for those, the L-Tyr is essential amino acid. L-Tyr is major precursor to biosynthesis of thyroxin, melanin and other neurotransmitters such as dopamine and norepinephrine [5], [6]. Therefore, due to the deficiency of L-Tyr, a number of clinical syndromes such as hypothyroidism [7], [8], genetic disorders [9], [10], attention deficit hyperactivity disorder [11], [12], sympathetic hyperactivation, pheochromocytoma and autonomic failure [13], [14], [15] are perceived in human. Thus, Tyr is an important bio-precursor to biosynthesis of various bio-species in human. To ensure the healthy physical conditions, Tyr is commercially used in food and pharmaceutical industries [16], [17] and as result, the large scale production process of Tyr is growing fast. The Tyr can be prepared using three different methods such as enzymatic, extraction and fermentation [18], [19], [20]. Science, Tyr has particular role for essential biochemical process in human, it is necessary to measure its level in human fluid periodically. The present research activities are conducted to detect bio-chemical using various semi-conductive and transition metal oxides in electrochemical approach [21], [22]. The aim of this study is to development of a sensor based on binary semi-conductive metal oxides using electrochemical approach.

Generally, the cadmium oxide (CdO) is n-type semi-conductive metal oxide and it has narrow optical band-gap (2.3 eV). Therefore, it has high electrical conductivity and used in various optoelectronic technological applications such as transparent electrodes, solar cells, photodiodes [23], [24]. Besides this, CdO has been applied successfully to detect various toxic chemical and biochemical such as melamine [25], 1,2-dichlorobenzene [26] and bilirubin [27]. Due to attractive optic-electro-chemical properties, SnO₂ is found as successive sensor material to detect benzaldehyde [28] and acetone [29]. In recent year, a number of sensitivity volumetric L-Try electrochemical sensors have been reported. The electrochemical detection of L-Tyr based on squarewave voltammetry using GCE modified by POM-rGO composite (POM-rGO/GCE) has shown a wider linear dynamic range (1.0 * 10⁻¹¹–1.0 * 10⁻⁹ M) with the detection limit of 2.0 * 10⁻¹² M [30]. Applying the similar detection method, an L-Tyr electrochemical sensor has been reported based on GCE coated by multi-wall carbon nanotube (MWCNT) and exhibited 2–500 µM linear dynamic range, 1.6455 µA µM⁻¹ cm⁻² sensitivity and 0.40 µM detection limit respectively [31]. Another research has been claimed that the single wall carbon nanotube (SWCNT) is also an effectual electron mediator on GCE to detect L-Tyr applying volumetric electrochemical detection method [32]. Besides this, TiO₂-graphene composite film layered on GCE with nafion binder has performed reliability to detect L-Try with good sensitivity, broad linear dynamic range and appreciable lower limit of detection [33]. Furthermore, a novel Au-nanoparticles/poly-eriochrome black T-film modified glassy carbon electrode (AuNPs/PEBT/GCE) has exhibited wider linear dynamic range (0.05–100 μM) with 10 nM detection limit [34]. Therefore, the binary combination of CdO-SnO₂ is effective for the development of an electrochemical sensor.

Therefore, a research methodology was developed here by using GCE layered CdO/SnO₂ NPs to detect selective L-Tyr in buffer phase. The L-Tyr sensor was found to exhibit excellent performances in term of sensitivity, detection limit, response time, reproducibility. It was also performed to detect the L-Tyr in a broad range of concentration (LDR) as well as in real bio-samples for the validation. In the field of pathological diagnosis and food industry, this method might be a reliable and efficient method for the detection of selective and sensitive biochemical by binary doped nanostructure materials using electrochemical approach in near future.