Eco-friendly synthesis of aloe vera plant extract decorated iron tungstate nanorods immobilized nafion based on the selective and sensitive determination of theophylline in blood serum, black tea and urine samples

Eco-friendly synthesis of aloe vera plant extract decorated iron tungstate nanorods immobilized nafion based on the selective and sensitive determination of theophylline in blood serum, [r]

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Eco-friendly synthesis of aloe vera plant extract decorated iron tungstate nanorods

immobilized nafion based on the selective and sensitive determination of theophylline

in blood serum, black tea and urine samples

A Karthika, C Sudhakar, A Suganthi, M Rajarajan

PII: S2468-2179(19)30222-9

DOI: https://doi.org/10.1016/j.jsamd.2019.09.004

Reference: JSAMD 253

To appear in: Journal of Science: Advanced Materials and Devices

Received Date: 9 May 2019

Revised Date: 5 September 2019

Accepted Date: 7 September 2019

Please cite this article as: A Karthika, C Sudhakar, A Suganthi, M Rajarajan, Eco-friendly synthesis of aloe vera plant extract decorated iron tungstate nanorods immobilized nafion based on the selective and

sensitive determination of theophylline in blood serum, black tea and urine samples, Journal of Science:

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Eco-friendly synthesis of aloe vera plant extract decorated iron tungstate nanorods immobilized nafion based on the selective and sensitive determination of theophylline in

blood serum, black tea and urine samples

A Karthika a , C Sudhakar c , A Suganthi a,b ** , M Rajarajan c*

a

PG & Research Department of Chemistry, Thiagarajar College, Madurai - 625009, Tamilnadu, India

b Mother Teresa Women's University, Kodaikanal-624 102, Tamilnadu, India

c Madurai Kamaraj University, Madurai-625 021, Tamilnadu, India Corresponding author: suganthiphd09@gmail.com**, rajarajan 1962@yahoo.com*

Abstract:

This paper describes a selective and sensitive detection of bronchodilators drug (theophylline) using aloe vera plant extract decorated iron tungstate nanorods (AFW) immobilized Nafion (Nf) modified glassy carbon electrode (GCE) (AFW/Nf/GCE) The AFW was synthesized by the co-precipitation method and characterized by UV-visible spectroscopy, x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), elemental analysis (EDX) and electrochemical studies Interestingly, the oxidation of theophylline with AFW/Nf/GCE displayed, a superior electrocatalytic activity, when compared with bare GCE and iron tungstate (FW) modified GCE Besides, oxidation of theophylline in electrochemical sensor revealed that the tremendous current response linear ranges from 0.1-160µM and low detection limit (LOD) 0.0028µ M The electrochemical sensor studies showed a tremendous selectivity in biological and food samples Besides, it showed manifested stability and reproducibility The proposed method has been applied for the selective determination of theophylline in real samples such as human serum, black tea, and urine samples

Keywords: Nanocomposite; theophylline; sensitivity; selectivity; electrochemical sensor

Eco-friendly synthesis of aloe vera plant extract decorated iron tungstate nanorods immobilized nafion based on the selective and sensitive determination of theophylline in

blood serum, black tea and urine samples Abstract:

This paper describes a selective and sensitive detection of bronchodilators drug (theophylline) using aloe vera plant extract decorated iron tungstate nanorods (AFW) immobilized Nafion (Nf) modified glassy carbon electrode (GCE) (AFW/Nf/GCE) The AFW was synthesized by the co-precipitation method and characterized by UV-visible spectroscopy, x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), elemental analysis (EDX) and electrochemical studies Interestingly, the oxidation of theophylline with AFW/Nf/GCE displayed, a superior electrocatalytic activity, when compared with bare GCE and iron tungstate (FW) modified GCE Besides, oxidation of theophylline in electrochemical sensor revealed that the tremendous current response linear ranges from 0.1-160µM and low detection limit (LOD) 0.0028µ M The electrochemical sensor studies showed a tremendous selectivity in biological and food samples Besides, it showed manifested stability and reproducibility The proposed method has been applied for the selective determination of theophylline in real samples such as human serum, black tea, and urine samples

Keywords: Nanocomposite; theophylline; sensitivity; selectivity; electrochemical sensor

1 Introduction

Theophylline (1, 3-dimethylxanthine (scheme (S1)), is one of the most important

xanthine alkaloid derivatives; present in coffee, tea, chocolate, and traditional medicines Remarkably, 6 % of people (infants, children, women, and men) were commonly affected by respiratory disorder every year Therefore, pharmaceutical chemists developed active and

e ective drugs to cure different respiratory disorders [1] The drug was clinically used in several pharmacological treatments such as asthma, neonatal apnea, airway diseases and chronic obstructive pulmonary diseases [2] Theophylline was found that the normal human blood plasma level in 5-20 µg/mL, was safe to our health But overdose [20µg/mL] and continuous usage of theophylline cause several critical issues such as arrhythmia; cardiac arrhythmias, insomnia, anorexia, fever, heartburn tachycardia, vomiting, and dehydration fever [3-5] As aforementioned, the high concentration (40µg/mL) of theophylline shows some clinical case in patients would pass on with respiratory arrest and cardiac arrest [6] Besides, theophylline developed and determined in some analytical methods reported by immunoassay, spectrophotometry, gas chromatography, mass spectrometry, thin layer chromatography, capillary electrophoresis, high-performance liquid chromatography, chemiluminescence and electrochemical method [7-14] These methods were required expert monitoring with trained technicians, required complicated facilities; high cost, need a huge amount of reagents and analysis sample was a long time Compared with other methods the electrochemical method was simple, low cost, user-friendly, portable, better selective, sensitive, accurate, easy handling and speedy analysis of theophylline determination Using various modified electrodes, several electrochemical theophylline sensors were industrialized in recent years Voltammetric performance of theophylline based on multiwalled carbon nanotube in pharmacological drug and urine samples was studied by S.J Malode et al [15] It was surveyed that after them Y Gao et

al investigated Carbon nanotube-large mesoporous/Nafion/GCE in determining theophylline in human serum samples [16] X Chen et al developed a highly sensitive electrochemical apt sensor for theophylline detection, based on gold nanoparticle [17], and theophylline sensor based manganese oxide nanoparticle/ionic liquids/ chitosan nanocomposite modified GC electrode [14] Besides, selective determination of theophylline based imprinted sol-gel film immobilized

on carbon nanoparticle modified electrode [18] and WS2/Ag nanoparticles based electrochemical determination theophylline [19] was developed Recently nanomaterial was synthesized different

properties appeared in bulk materials The intensive research of metal tungstate focused on a variety of application such as scintillator materials, semiconductors, photoluminescence, water splitting, humidity sensor, catalysis, Li-ion batteries, and an optical sensor However, dual metal oxides (combining two metals with single phase an oxygen atom) display large reactive sites, good conductivity, and higher stability when compared primary one [20-24] Over the past decades, inorganic nanostructure materials are found tremendous interest due to their unique physicochemical properties In particularly inorganic FeWO4 transition metal oxides have drawn significant interest in a variety of technological applications with photocatalysis, gas sensor, catalysis, conducting electrode, sensitized-dye using solar cells by lithium-ion batteries [25-30] Wolframite structure of inorganic nanoparticles of FeWO4 obtained different shape and size present in optical, magnetic and electrical properties [31] The oxygen binding closed pack of the hexagonal structure consisted for FeWO4 (ferrierite) nanoparticles planned method and it was a

superior performance of the electron transport process [32, 33]

Green chemistry was a major role of synthesis nanomaterials is current reported The main compensation for nanomaterial was synthesized and used for plants, microbes, and algae Now a days, synthesized nanomaterial was used as intermediary for plants obtained low cost, harmless, easily prepared single step method and eco-friendly [34-36] The aloe is a genus and the spices for A vera (syn: aloe barbadensis Mill) go to the subfamily Asphodeloideae with the main member for Liliaceae Aloe vera (Aloe Barbadecsis) leaves was triangular saw-like structure and ornamental plant It can be used as an important medicine in siddha, homeopathy, ayurveda and unani Particularly the extract of agave is used in the treatment of skin disease In the present idea of this work, a novel eco-friendly nature of plant leaf extract was decorated for FeWO4 was synthesized by co-precipitation method At this time Nafion is an electrode modifier

to immobilize the AFW nanocomposite drop cast on the surface GCE The immobilization of catalytic molecules on electrode surface has several advantages over the bare electrodes as (i) modified electrodes alter the overall rate of electrochemical reactions, (ii) the catalyst is readily separated from the solution medium and (iii) a very small amount of catalyst is required for the electrocatalytic reactions [37, 38] Simplest drop coating method has been adapted to coat AFW/Nf/GCE surface using micro-syringe This type of electrode modification allows the electrocatalyst to be dispersed into the molecular level with good electrocatalytic activity in many electrocatalytic reactions [39] The AFW was characterized by a variety of spectroscopic,

analytical and electrochemical sensing method The fabricated AFW/Nf/GCE showed good selectivity, sensitivity, low detection limit and good electrocatalytic behavior towards the detection of theophylline in various (human blood serum, back tea, and urine) real samples and better recovery results

2.0 Experimental

2.1 Materials and methods

Ferric chlorites, sodium tungstate, theophylline, cystine, citric acid, dopamine, glucose, ascorbic acid, oxalic acid, lactic acid, l-tyrosine, starch, and quercetin all the chemicals were purchased from Sigma-Aldrich The buffer solution of pH 3.0 to 8.0 (NaH2PO4 and Na2HPO4) is used to prepare the standard (0.1M) solutions and the pH values are adjusted using 0.1M NaOH and 0.1M orthophosphoric acid The stock solution of theophylline is prepared using triple distilled water and stored in dark condition All the solutions are prepared using analytical grade chemicals and triple distilled water

XRD pattern is obtained using an X-ray diffraction unit with (λ=1.5418ºA) on X-ray diffraction (Model: JDX-8.30, JEOL, Japan) The UV-visible spectra are carried out using UV-visible spectrophotometer (Model: Hitachi, U-3300) FT-IR data of the nanocomposite are obtained using Perkin-Elmer spectrophotometer in the range of 400-4000 cm-1 (Model 460plus, Jasco, Japan) Morphology aspects of nanocomposite and its particle are evaluated from SEM (Model: Vega3, TESCAN, USA) The following electrochemical methods are adopted in a usual three-electrode system with nanocomposite modified GCE as a working electrode, platinum (Pt) wire as a counter electrode and saturated KCl/Ag/AgCl as a reference electrode All the electrochemical techniques are performed using CHI-electrochemical workstation (Model-660E, USA) under a nitrogen gas atmosphere at room temperature Electrochemical investigations are performed at least 3-5 times for getting the reproducible results

2.2 Preparation of Aloe Vera Plant extract

Aloe Vera plants were collected from Thiagarajar College campus and about 25 gram was thoroughly washed in distilled water and cut into fine gel pieces The gel pieces were

dribbled with mortar The plant extract solution was filtered using a Whatman filter paper (model: 300W) Finally, the extract was used for all experiments

2.3 Synthesis of iron tungstate

The starting material of 0.1M (4.28g) of ferric chloride was dissolved in (50ml) deionized water with constant stirring, and then 0.2M (5.47g) of sodium tungstate was added in drops into above mixture solution at pH=9-11 (NaOH) The precipitate solution was transferred into an autoclave (Teflon lined stainless steel) heated at 180°C for 3 h The resultant product was filtered using NO.1 Whatman paper with ethanol and water A brown color precipitate was obtained and that was dried at 400 °C for 4 h using drier

2.4 Synthesis of aloe vera plant extracts using iron tungstate

1 g of ferric chloride and 2.03 g of sodium tungstate dissolved were dispersed in 50 mL deionized water After appearing a brown precipitate solution, 20 ml extract was added into the dispersive solution of sodium tungstate and ferric chloride followed by vigorous stirring for 3hrs

To adjust the pH value 9-11, NaOH solution (0.1M) was added The mixture solution was transferred into an autoclave (Teflon lined stainless steel) heated at 160°C for 5 h The obtained precipitate was washed with triple distilled water, ethanol and dried at 400° C (3h) muffle furnace

2.5 Fabrication of theophylline modified electrode

The polished mirror-like surface of GC electrode with 0.3mm was used for surface modifications With the aim of fixation of nanocomposite on GCE, 1 mg AFW/Nf was dispersed into the solution by an ultra-sonication method for 30 min After it was sonicated, 5 µL of AFW/Nf was the dispersive solutions was pipetted and drop cast onto the GCE surface and dried

in air at room temperature for 10 mins Finally, obtained nanocomposite modified GCE was used

to sense theophylline in the present study (scheme (S2)

3.0 Result and discussion

3.1 Characterization

UV-Vis absorption spectra were observed the electronic/optical properties of FW and AFW nanoparticle was shown in Fig 1 In Fig.1a broad absorption band onset was observed at

350 nm Aloe Vera plant extract showed the shift with the small wavelength (380 nm) shown in Fig.1b [40] The nanocomposite can be recognized to the electron charge transfer conversion of d electron metal ions found the conduction or valence band by FW and AFW The bandgap energy was calculated for FW (1.8eV) and AFW (2.1 eV) The crystallographic nature of the materials synthesized was studied by powder XRD pattern shown in Fig.2 Crystalline nature of diffraction peaks was indexed monoclinic phase JCPDS number file No 46-1446, through the lattice parameters of a = 4.739Å, b = 5.718Å, c = 4.965Å was shown in Fig.2a The intensity was clear that the full width of half maximum (FWHM) of the strongest characteristic peak for AFW nanoparticles are stronger and broader than that of FW indicating the crystal size of AFW is smaller than that of FW The crystalline size was calculated by Debye Scherer equation and was found 30 nm and 15.83 nm respectively [33] The FT-IR spectra of FW and AFW nanocomposite are shown in Fig.3 (a, b) Fig.3 shows the peak at 3352 and 2924 cm-1, which correspond to the O-H and C-H stretching vibration peak appeared The observed peak at 878 and 824 cm-1,which corresponds to WO2 and W2O8 stretching vibrations exist in FW The two bridge of oxygen (W2O2) shows symmetric stretch at 629 cm-1 In addition, the band observed at

450 cm-1 confirms the stretching vibration of the FeO6 polyhued building validating the formation of FeWO4 structure Then the peaks were positioned (1647 cm-1) C=C aromatic stretching vibration with associated O-H vibration (1452 and 1251 cm-1), C-N and N-H stretching vibration located at 663 and 1045 cm-1

The structure and morphology of the surface consequential were examined using scanning electron microscopy The morphology shape was nanorod with aggregation is observed and displayed in Fig.4a However, aggregation is not observed on the addition of plant extract as shown in Fig.4b Plant extract acts as a capping agent and is established by EDX spectrum [41, 42] The corresponding EDX spectrum was confirmed by the presence of Fe, W, O, and C that appeared as strong signal peak This showed a good agreement with the functionalized AFM nanocomposite

pH=7 (0.1M PBS) at scan rate 50 mVs-1 Fig.5 shows the potential range from +0.2 to 1.2V and the unmodified GCE (bare GCE) was not observed for anodic current peak, the bare GCE was not separated by anodic peak current of theophylline Compared with FW/GCE bare GCE observed with weak anodic peak current, presented at an electrochemical performance in theophylline was shown in Fig.5 (b & c) In Fig.5c (AFW/Nf/GCE) very sharp and high anodic peak current was observed with large surface area and excellent electrochemical activity This result of the proposed AFW/Nf/GCE nanocomposite displays a good electrocatalytic activity towards the oxidation of theophylline

3.3 Effect of scan rate and pH

The influence of scan rate on the oxidation of theophylline with AFW/Nf immobilized modified GC electrode in 50µM theophylline (0.05M PB=7) was investigated by Cyclic voltammetry (CV) and the obtained result was displayed in Fig.6 These results revealed that the anodic peak current was gradually increased with increasing the scan rate from 10-160 mV/s and slightly shifted towards the positive potential side Fig.6b exhibits the linear relationship between anodic current peak and different scan rate and a linear regression equation can be expressed as Ipa = 0.0191x+1.1859 with a correlation coefficient (R2) = 0.9963 respectively This result indicates that the electrochemical detection of theophylline at AFW/Nf/GCE which is an adsorption controlled process [43-45]

The pH of the electrolyte can affect the performance of AFW/Nf/GCE to the oxidation of theophylline From Fig.7 (a-c), it is clearly understood that increasing the pH value from 3 to 8 (0.1 M PBS) the anodic peak current of theophylline increases with increase in the pH above 7 Therefore, we selected optimum pH=7 were used for further electrochemical studies Predominant pHs, the more hydroxyl particles are collaborated with the theophylline and prompt the de-protonation, subsequently, the electrocatalytic movement decreased [46, 16] The linear plot of anodic peak potential and different pH is shown in Fig.7b By increasing the pH medium from lower to a higher level, peak current potential was shifted to the positive side The linear equation for anodic peak potential (V) =4.4812x-2.352 (R2=0.998) According to this equation [47]

Where R is the gas constant, n is the transfer electron number, T is the standard temperature m is the proton number, F is the Faraday constant and Epc is the cathodic peak potential [48-50]

3.4 Difference pulse voltammetry (DPV)

DPV was more sensitive better resolving compared with CV [51-53] The DPV found the calibration of linear plot used at pH =7 PBS shown in Fig.8 Electrochemical performance of theophylline concentration was increased from lower level to higher level from linear ranges 0.1-

160 µM Besides the DPV performed addition of theophylline in the well sharp anodic peak and the observed value is at 1.1V The calibration curve found that a linear equation Ipc (µA) = 0.0531+2.615 (R2 = 0.991) with lower limit (0.0028µM) and higher sensitivity (2.573µM−1cm−2) shown in Fig.8b The low-level concentration theophylline has appeared in movement reasonably with fast response AFW/Nf/GCE with rapidly superior electrocatalytic current The discovered result was obtained from the high linear range, lower detection limit and good sensitivity showed an enhanced or similar performance with reported in Table.1 (ST2) [46-47, 51,53-57 16, 19]

3.5 Studies of stability, selectivity, and reproducibility

The electrochemical sensor was newly developed for a significant selectivity [58-60] The selectivity evaluated the AFW/Nf/GCE containing interference for amperometric current potential applied +1.1V at 1200 pm rotation speed continuously stirred with pH=7 (0.1M PBS) Electrochemical sensor response for modified GCE was well defined through adding 50 µM of theophylline (a) presently considerable addition of hundredfold excess shows no response were observed while the response by the addition of 100 fold excess in biological sample was co-interference such as Cystine (Cys), Citric acid (Ca), Dopamine (Dp), Glucose (Glu), Ascorbic acid (Aa), Oxalic acid (Oa), Lactic acid (La), L-tyrosine (L-tyr), Starch (Str) and Quercetin (Qcerti) shown in Fig.9 The determination of theophylline used for three independent electrodes

at present in the (3.9%) relative standard deviation indicated the anodic peak current promised a

superior reproducibility Besides, the unique response appeared at 50µM storage stability of 91% AFW/Nf/GCE, suggestive of satisfactory storage capacity

3.6 Real samples analysis in theophylline

The AFW/Nf/GCE explored analysis in block tea, urine and human blood serum samples The human serum and urine sample were collected from a government hospital, Madurai and black tea samples were collected from the local market in Madurai The prepared sample was subjected to suitable dilution at pH=7, 0.1M PBS The AFW/Nf/GCE achieved good recovery by the electrochemical sensing for block tea, urine, and blood serum samples [61] The samples were diluted 100 times with PBS (pH 7.0), and different amounts of theophylline were spiked in them without further treatment These studies demonstrated that the good recovery achieved by AFW/Nf/GCE for the human urine, blood serum and black tea samples The standard addition method used in previous studies was considered The obtained good recoveries were ranging between 98.6 % and 99.3 % for the theophylline black tea, urine and serum sample, and those results are summarized in Table.2 (ST2)

4 Conclusion

We successfully synthesized aloe vera plant extract using FW nanocomposite through a simple co-precipitation method The AFW nanorods were characterized via spectral, analytical and electrochemical techniques AFW/Nf/GCE exhibited tremendous electrocatalytic activity for the oxidation of theophylline The fabricated AFW/Nf immobilized modified GC electrode using DPV techniques widely present in the linear range (0.1-160µ M), and LOD (0.0028µM) and sensitivity (2.573µ M−1cm−2) for the theophylline detection The modified electrode was displayed with great stability, selectivity, and reproducibility Besides, the AFW/Nf/GCE was sensing real-time monitoring in pharmaceutical and biological samples

Acknowledgement

The authors thank the UGC Networking Resource Centre, School of Chemistry, University of Hyderabad, Telangana, India, for providing necessary laboratory facilities to carry out this work.The authors thank the Management of Thiagarajar College for providing necessary laboratory facilities to carry out this work

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