CDs are non-dimensional nanoparticles with a size of less than 10 nm. Due to their applications in computer science and electronics, fluorescent carbon nano dots have sparked a lot of interest in the last decade [1, 2]. Compared to other fluorogenic probes, CDs step forward by their inherent features; chemical stability, inertness, significant luminescent emissions, least toxicity, ease of synthesis, high biocompatibility and photostability [3,4,5,6,7]. Furthermore, they possess free aqueous solubility as a result of hanging hydroxyl and carboxylic groups at the surface, high safe carbon content (99.9%) relative to inorganic metal nanoparticles and finally the affordability endears the CDs’ participation in nowadays targeted green analytical methodologies [8].
Generally, there are many methods for synthesizing CDs, including electrochemical, chemical oxidation, laser ablation, and arc discharge. Furthermore, when seeking a synthesis approach to obtain CDs, a number of criteria need to be taken into account. The possibility of carbonaceous aggregation, which is frequently formed during the carbonization process, emerges in the synthesis of CDs. Synthesis techniques including the hydrothermal route, organic pyrolysis, and microwave assisted approach can solve this problem. These methods have the ability to regulate the homogeneity and size of CDs in solvents [9].
Nowadays, scientific community’s interest has been directed towards synthesis, direct and indirect CDs’ assays. The present labour targets the insightful use of CDs for optic nano sensing of two non-fluorophoric nitrogenous compounds of high pharmaceutical interest; Azithromycin (AZN) and Rasagiline mesilate (RSGL) in both pure bulk and medical products. Quantitative CDs quenching is related to the added traces of each drug in stoichiometric reactions.
This article enfolds the direct use of green synthesized CDs [10] as spectrophotometric and fluorescent probes for both drugs’ analysis. The used nano CDs were already synthesized from garlic peels, as natural precursor, as described by Gaber et al. [11]. Detailed steps of synthesis of the used nanodots are provided in Additional file 1.
AZN belongs to the macrolide family of antibiotics. It is mainly indicated for respiratory, enteric and genitourinary infections [12, 13]. AZN has been included in the solidarity concomitant Covid-19 protocol [14] since March, 2020. AZN, chemically named C38H72N2O12, Mwt 748.98 g/mol. Its IUPAC name is (2R, 3S, 4R, 5R, 8R, 10R, 11R, 12S, 13S, 14R)-13-[(2,6-Dideoxy-3-C-methyl-3-O-methyl-α-l-ribo-hexopyranosyl)oxy]-2-ethyl-3,4,10-trihydroxy-3,5,6,8,10,12,14-heptamethyl-11-[[3,4,6-trideoxy-3-(dimethylamino)-β-d-xylo-hexopyranosyl]oxy]-1-oxa-6 azacyclopentadecan-15-one; and Fig. 1 depicts its chemical structure. AZN lacks chromophore for direct UV absorption. So, its quantification represents a real analytical challenge.
RSGL is a novel molecule that works as an irreversible monoamine oxidase inhibitor to treat idiopathic Parkinson's disease [15,16,17]. Chemical name for RSGL is (1R)-N-(prop-2-yn-1-yl)-2,3-dihydro-1H-inden-1-amine; methane sulfonic acid, (Fig. 1). Literature reveals few spectrophotometric methods [18,19,20,21,22,23] and two fluorimetric assays [24, 25] for determination of AZN in bulk and formulations. A detailed review for RSGL estimation [26] is reported, without direct fluorimetric technique. RSGL has been determined by LC-fluorimetric detection in rat plasma for pharmacokinetic studies [27]. This endears developing novel selective, sensitive, methods of AZN and RSGL determination in routine quality control. Herein, CDs act as potent spectrometric sensors for non-fluorophoric nitrogenous compounds. Both drugs react stoichoimetrically with CDs, resulting in a linear diminish in the dots measured absorbance and fluorimetric emission values. The present study achieves green and economic direct AZN and RSGL optical sensing in both pure and pharmaceutical dosage forms.