Abstract
(1) Background: Nanocrystals (NCs)-based electrochemical sensors have been proposed for biomarkers detection, although immunosensors using ZnO NCs decorated with copper are still scarce. (2) Methods: Electrochemical immunodetection of human salivary alpha-amylase (HSA) used ZnO, CuO, and ZnO:xCu (x = 0.1, 0.4, 1.0, 4.0, and 12.0) NCs. (3) Results: Substitutional incorporation of Cu2+ in the crystalline structure of ZnO and formation of nanocomposite were demonstrated by characterization. Graphite electrodes were used and the electrochemical signal increased by 40% when using ZnO:1Cu and 4Cu (0.25 mg·mL−1), in an immunosensor (0.372 mg·mL−1 of anti-alpha-amylase and 1% of casein). Different interactions of HSA with the alpha-amylase antibody were registered when adding the NCs together, either before or after the addition of saliva (4 μL). The immunosensor changed specificity due to the interaction of copper. The ZnO:1Cu and ZnO:4Cu samples showed 50% interference in detection when used before the addition of saliva. The immunosensor showed 100% specificity and a sensitivity of 0.00196 U·mL−1. (4) Conclusions: Results showed that the order of NCs addition in the sensors should be tested and evaluated to avoid misinterpretation in detection and to enable advances in the validation of the immunosensor.
Highlights
In search of high sensitivity, response time, good performance, easy handling, accurate reporting, portability, low cost, and reliable detection of biomarkers, in this work, we developed an immunosensor based on zinc oxide (ZnO) NCs decorated with Cu for the electrochemical detection of human salivary alpha-amylase (HSA)
The grain size was obtained from the X-ray diffractograms (XRDs) line-broadening measurement, using the Scherrer equation; being 20 nm, it confirmed the formation of NCs
After adding different concentrations of NCs onto the electrode surface, the results showed that ZnO:0.4Cu (3th bar) presented 26.21% higher roughness compared with ZnO
Summary
There are odd properties associated with design, and this field presents a new universe with vast possibilities and enormous technological potential, mainly in the development of biosensor speed, low cost, and portability. Both organic (viral or protein) and inorganic (metal) nanoparticles exist in nature. They do not present controlled synthesis, which means a sample will not be homogeneous when collected at different sites or conditions [2,3]. They do not present controlled synthesis, which means a sample will not be homogeneous when collected at different sites or conditions [2,3]. 4.0/).
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