Bifunctionality of Carbon Nanotubes – Chitosan Film Based Biosensor for Selective Determination of Atropine in Biological Fluids and Leaf Extract of Datura Stramonium
Authors: Mane Suyash Shashikant , Chatterjee Sanghamitra 
Published: February 2020

Atropine is a tropane alkaloid, which is most commonly found in Solanaceae family and serves as a drug with wide variety of effects. It is a racemic mixture of d-hyoscyamine and l-hyoscyamine, with most of its physiological effects due to l-hyoscyamine. The drug has extensive clinical applications because of its strong parasympatolytic, antispasmodic and anticholinergic actions. The anticholinergic activity results in blurred vision, vasodilation, increased heart rate and delirium. It is used to cure organic phosphorous pesticides poisoning. Atropine acts pharmacologically via blocking acetylcholine receptors of the muscarine subtype, which causes not only peripheral effect symptoms such as tachycardia, dilated pupils, and decreased gastrointestinal motility, but also affects the central nervous system and causes agitation, disorientation and hallucinations. It has been established as a very efficacious antidote to poisoning with parasympathomimetic nerve agents. Atropine has several medicinal applications like reducing rigidity in Parkinsonism, bronchial asthma, treating bradycardia in emergency settings, alleviating the viscera angina, peptic ulcers, renal colic and biliary colic. In spite of its wide clinical applications, the use of the highly toxic atropine in suicides and homicides has also been described in case reports. Since, the dosage level of atropine in pharmaceutical preparation is key to the effective treatment of diseases; its quantitative determination is of considerable significance in medicinal applications.
Carbon nanotubes aroused attention in the burgeoning field of electrochemical sensors due to their unique properties including improved electrochemical activity. The single walled carbon nanotubes (SWCNTs) based biosensor is one of the immense frontiers in analytical chemistry, which is because of the high electrical conductivity, large surface area, ability to alleviate surface fouling and remarkable biochemical stability of SWCNTs. Chitosan is a cellulose – based biopolymer with large number of reactive amino and hydroxyl functional groups rendering the properties of excellent film-forming ability, high water permeability, good adhesion, and susceptibility to chemical modifications. SWCNTs have the potential to form stable and uniform nanocomposite dispersion in chitosan solution via covalent attachment that provide a platform for the development of biosensor.
The integration of nanomaterials with biopolymer in the field of sensors and biosensors have allowed improving analytical performance. The main objective of this work is to develop an electrochemical sensor with enhanced sensitivity and augmented selectivity in the desired environment. In the present investigation, we have explored a non-destroyable surface decoration of single walled carbon nanotubes with biopolymer chitosan composite film coated on a glassy carbon electrode for the first time for the selective and ultrasensitive determination of atropine. The biosensor exhibited notable stability, exemplary reproducibility and uniformity in the composite film, short response time and an excellent catalytic activity towards the electro oxidation of atropine leading to a significant improvement in sensitivity. The developed biosensor displayed an electrocatalytic effect towards the anodic oxidation of atropine with selective recognition. Under the optimized conditions, the calibration curve for atropine concentration was linear in the range from 100 nM – 150 µM with the limits of quantification and detection as 54.9 and 16.5 nM, respectively. The high sensitivity was estimated to be 2.7 µA µM-1 for the proposed method. The selectivity of the developed sensor was substantiated by performing interference study in the presence of commonly existing biological metabolites. The developed biosensor was efficaciously applied to determine atropine in pharmaceutical samples available in the market. The biological relevance of the present method has been demonstrated by the analysis of atropine in media of human plasma and urine samples that correlate best with the pharmacological or toxicological effects. In addition, the versatility of the fabricated sensor was corroborated by the selective detection of atropine in the leaf extract of Datura stramonium.