Amplifying Biosensor Sensitivity through Chitosan-Coated Nanoparticles

Chitosan, a biocompatible polymer derived from chitin, enhances biosensor sensitivity by facilitating precise recognition element immobilization and protecting against interference [1], [2]. When combined with chitosan-coated nanoparticles, it further amplifies sensitivity by increasing the surface area for binding and signal output, improving biosensor performance [3], [4]. To verify the effect of the chitosan-coated gold nanostructures on the surface of a screen-printed carbon electrode (SPCE) sensor, we modified gold nanoparticles and nanostars with chitosan and performed several morphological and electrical characterizations. Uniformity, diameter size, and dispersion of the nanostructures were investigated with atomic force microscopy (AFM), UV-Vis spectroscopy, and scanning electron microscopy (SEM) images. The electrical analysis was performed after electrodepositing the coated nanostructures on the working electrode of the SPCE sensor. First, the cyclic voltammetry (CV) technique was measured with a buffer solution where the peak currents were amplified after the functionalization step. The Nyquist plots were also recorded to verify the charge transfer resistance based on the equivalent circuit. To verify the nanostructures’ performance for the detection of biochemicals, we decided to immobilize specific antibodies (100 ng/mL) over the nanostructures and detect apolipoprotein E4 (APoE4), a specific allele of the APoE gene associated with Alzheimer's disease. We performed differential pulse voltammetry measurements to quantify the biomarker (ranging from 0.41 to 40 ng/mL) in human serum samples (less than 20 μL). The current peak variations showed high linearity, with a linear regression coefficient (R²) of 0.9841, corresponding to the levels of ApoE4. Further studies will involve validation and interference tests, including the detection of other Alzheimer's disease (AD) biomarkers, such as Amyloid-β 42.<br/><br/>[1] S. Yu, X. Xu, J. Feng, M. Liu, and K. Hu, “Chitosan and chitosan coating nanoparticles for the treatment of brain disease,” <i>Int. J. Pharm.</i>, vol. 560, no. February, pp. 282–293, Apr. 2019, doi: 10.1016/j.ijpharm.2019.02.012.<br/>[2] C. O. Mohan, S. Gunasekaran, and C. N. Ravishankar, “Chitosan-capped gold nanoparticles for indicating temperature abuse in frozen stored products,” <i>npj Sci. Food</i>, vol. 3, no. 1, p. 2, Jan. 2019, doi: 10.1038/s41538-019-0034-z.<br/>[3] X.-X. Dong <i>et al.</i>, “Portable amperometric immunosensor for histamine detection using Prussian blue-chitosan-gold nanoparticle nanocomposite films,” <i>Biosens. Bioelectron.</i>, vol. 98, pp. 305–309, Dec. 2017, doi: 10.1016/j.bios.2017.07.014.<br/>[4] G.-C. Fan, X.-L. Ren, C. Zhu, J.-R. Zhang, and J.-J. Zhu, “A new signal amplification strategy of photoelectrochemical immunoassay for highly sensitive interleukin-6 detection based on TiO2/CdS/CdSe dual co-sensitized structure,” <i>Biosens. Bioelectron.</i>, vol. 59, pp. 45–53, Sep. 2014, doi: 10.1016/j.bios.2014.03.011.