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Abstract
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Gold nanoparticles (AuNPs) exhibit a unique phenomenon known as Surface Plasmon Resonance, which is responsible for their intense red color. This color changes to blue upon aggregation of AuNPs. The color changes associated with the aggregation of AuNPs has led to the development of colorimetric based assays for a variety of target species [1,2]. Recently, the conjugation of AuNPs with biomolecules such as aminoacids and proteins has attracted considerable attention [3]. Some of the amino acids at low pH are capable of binding to the surface of AuNPs by various affinities and inducing nanoparticle aggregation with different kinetics. As a result of the induced aggregation, the UV–Vis spectra of colloidal AuNPs change with time. So, the differential interactions of amino acids with AuNPs give a distinct pattern for each of them as a fingerprint, which is employed for classification and identification. In this work, the kinetic absorption spectra related to the AuNPs aggregation in the presence of selected amino acids i.e. histidine (His), cysteine (Cys), lysine (Lys) methionine (Met) and arginine (Arg) has been recorded as a function of time for 45 min at different concentrations. The collected spectra were then analyzed with unsupervised pattern recognition techniques, including hierarchical cluster analysis (HCA) and principal component analysis (PCA). The proposed method could successfully discriminate the five amino acids and the identification accuracy was found to be 97%. Moreover, the method has the capability of discrimination of amino acids mixtures.
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