Rajasekhar Chokkareddy

Smart Nanomaterials for Infectious Diseases Nanoscience & Nanotechnology Series Editor-in-chief: Nguyễn T. K. Thanh, University College London, UK Seri

Aim:: The main strategy of this study is to develop a novel ionic liquid functionalised metal nanocomposite based electrochemical sensor with potential applications for the sensitive electrochemical detection of rifampicin.Background:: Tuberculosis (TB) is a widespread disease that is caused by the gram-positive Mycobacterium tuberculosis (MTB). In addition, for several decades TB has become a constant threat to human health, however due to the accessibility of broad-spectrum antibiotics (rifampicin, pyrazinamide, isoniazid, and ethambutol), which are active against the bacterium, the social and economic burden for sufferers from the illness remains to be huge. Specially, in countries, like India and sub Saharan Africa, it is one of the common diseases affecting members from all age groups. So, this work is aimed at developing a novel electrochemical sensor for the determination of rifampicin (RIF) in pharmaceutical samples.Objective:: To synthesis and characterization of the novel liquid functionalised metal nanocomposite. Fabrication of glassy carbon electrode with potent electrode modifiers whose applicability as electro catalysis agents towards rifampicin is investigated.Method:: In this work, a nanocomposite based on trihexyltetradecylphosphonium-bis-(2,4,4-trimethylpentyl)-phosphinate ([P14, 6, 6, 6] [(C8H17)2 PO2)]) ionic liquid functionalised titanium oxide nanoparticles (TiO2NPs) and multiwalled carbon nanotubes (MWCNTs) were used in the modification of a highly sensitive electrochemical sensor for quantification of rifampicin in pharmaceutical formulations. The modified glassy carbon electrode (GCE) were characterised by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD).Results:: The electrochemical behaviour of RIF was studied on the modified electrode by the cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. At pH 6.0 in phosphate buffer solution (PBS), the anodic peak current value of RIF obtained with the fabricated electrode is 7 times greater than with the bare GCE electrode. The anodic peak current value and concentration of RIF showed a good linear relationship in the range of 0.015–2.8 μM, with the limit of detection (LOD) of 0.0218 μM and limit of quantification (LOQ) 0.3120 μM respectively.Conclusion:: Under the optimal conditions, the IL-f-TiO2NPs-MWCNTs-GCE provided a relatively lower detection limit and wider linear range compared to other previous procedures. The proposed electrochemical sensor had potent catalytic activity for RIF oxidation and provided important quantitatively reproducible analytical performance. Finally, this modified electrode was successfully applied to the determination of RIF in real pharmaceutical samples.

Background:: While significant strides have been made to avoid mortality during the treatment of chronic diseases, it is still one of the biggest health-care challenges that have a profound effect on humanity. The development of specific, sensitive, accurate, quick, low-cost, and easy-to-use diagnostic tools is therefore still in urgent demand. Nanodiagnostics is defined as the application of nanotechnology to medical diagnostics that can offer many unique opportunities for more successful and efficient diagnosis and treatment for infectious diseases. Methods:: In this review we provide an overview of infectious disease using nanodiagnostics platforms based on nanoparticles, nanodevices for point-of-care (POC) applications. Results:: Current state-of-the-art and most promising nanodiagnostics POC technologies, including miniaturized diagnostic tools, nanorobotics and drug delivery systems have been fully examined for the diagnosis of diseases. It also addresses the drawbacks, problems and potential developments of nanodiagnostics in POC applications for chronic diseases. Conclusions:: While progress is gaining momentum in this field and many researchers have dedicated their time in developing new smart nanodevices for POC applications for various chronic diseases, the ultimate aim of achieving longterm, reliable and continuous patient monitoring has not yet been achieved. Moreover, the applicability of the manufactured nanodevices to rural patients for on-site diagnosis, cost, and usability are the crucial aspects that require more research, improvements, and potential testing stations. Therefore, more research is needed to develop the demonstrated smart nanodevices and upgrade their applicability to hospitals away from the laboratories.

Background: The invention of enhanced Raman scattering by adsorbing molecules on nanostructured metal surfaces is a milestone in the development of spectroscopic and analytical techniques. Important experimental and theoretical efforts were geared towards understanding the Surface Enhanced Raman Scattering effect (SERS) and evaluating its significance in a wide range of fields in different types of ultrasensitive sensing applications. Methods: Metal nanoclusters have been widely studied due to their unique structure and individual properties, which place them among single metal atoms and larger nanoparticles. In general, the nanoparticles with a size less than 2 nm is defined as nanoclusters (NCs) and they possess distinct optical properties. In addition, the excited electrons from absorption bands results in the emission of positive luminescence associated to the quantum size effect in which separate energy levels are produced. Results: It is demonstrated that fluorescent based SERS investigations of metal nanoparticles have showed more photostability, high compatibility, and good water solubility, has resulted in high sensitivity, better imaging and sensing experience in the biomedical applications. Conclusion: In the present review, we report recent trends in the synthesis of metal nanoclusters and their applications in biosensing and bio-imaging applications due some benefits including cost-effectiveness, easy synthesis routes and less consumption of sample volumes. Outcomes of this study confirms that SERS based fluorescent nanoclusters could be one of thrust research areas in biochemistry and biomedical engineering.

A sensitive, low cost and novel electrochemical sensor based on 1‐ethyl‐3‐methylimidazolium 1,1,2,2‐tetrafluoroethanesulfonate ionic liquid (EmimTFES) combined with multi‐walled carbon nanotubes (MWCNTs) and zinc oxide nanoparticles (ZnONPs) in order to modify the glassy carbon electrode (GCE), has been developed for the first time. It was assessed that this sensor can be used for the rapid detection of the pharmaceutically antiretroviral drug zidovudine (ZDV). The characterization of ZnONPs, MWCNTs‐ZnONPs and MWCNTs‐ZnONPs‐EmimTFES was performed using Transmission electron microscopy (TEM), Ultraviolet Visible spectrophotometer (UV‐Vis), Fourier‐transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), and Thermogravimetric analysis (TGA). The electrochemical of behaviour of MWCNTs‐ZnONPs‐EmimTFES‐GCE was studied using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. The proposed sensor shows high electrocatalytic activity towards ZDV reduction over the concentration range of 0.2 μM to 2.0 μM. In addition, the limit of detection (LOD) of 0.0029 μM and limit of quantification (LOQ) of 0.0416 μM was obtained. Under optimal conditions the ionic liquid‐based sensor showed high selectivity, stability and sensitivity for ZDV detection, making it a suitable sensor for rapid determination of ZDV.

A novel and sensitive method for the determination of aflatoxin B1 (AFA−B1) in ground paprika using a methyltrioctylammonium chloride ionic liquid (IL), iron oxide nanorods (Fe₃O₄ nanorods) and reduced graphene oxide (RGO) fabricated glassy carbon electrode (GCE) was developed. The synthesized nanoparticles, nanocomposites and modified electrode surfaces were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA/DSC) and x‐ray diffraction (XRD) analyses. Moreover, the electrochemical performance of the developed sensor was determined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The obtained results demonstrate that the sensitivity of AFA−B1 is significantly enhanced on RGO‐Fe₃O₄ nanorods‐IL‐GCE in comparison with bare GCE, RGO‐GCE and RGO‐Fe₃O₄ nanorods‐GCE. The redox peak currents of AFA−B1 exhibited good linear relationship with its concentration in the range from 0.02 to 0.33 ng mL⁻¹ with detection limit of (LOD) 0.03 ng mL⁻¹ and limit of quantification (LOQ) 0.36 ng mL⁻¹ respectively (S/N=3). In addition, the fabricated electrode showed good stability and reproducibility. The proposed technique was effectively applied to identify the AFA−B1 in real ground paprika samples with acceptable results.

Background: A simple, low cost and highly sensitive catalytic hydrogen wave (CHW) method has developed for the investigation of Manganese(II) in ammonium 4-phenylpiperazine-1- dithiocarbamate and ammonium 4-benzylpiperidine-1-dithiocarbamate in various environmental and biological samples using D.C. polarography. This procedure was based on the reaction of Mn(II) in APP-DTC/ABP-DTC in the presences of NH₄Cl-NH₄OH medium at pH 6.6 and 7.2 respectively. The resulting oxidation signals were obtained at -0.78 V and -0.64 V vs SCE, owing to the CHWs. Different experimental conditions such as pH effects, background electrolyte (NH₄Cl-NH₄OH) effects and DTCs and Mn(II) ion effects have been studied. The current method was effectively employed for the testing of Mn(II) in different environmental and biological samples and attained recovery percentages (95-99%) are comparable to the Atomic Absorption Spectrophotometry (AAS) method. Methods: Direct current polarography, model CL-357 and CL-25 (Elico Private Ltd, Hyderabad, India), Shimadzu AA 6300 spectrometer furnished thru a deuterium background corrector and hollow cathode lamp, at corresponding wavelengths (resonance line) with an air acetylene flame. The experimental guidelines remained those suggested by the makers. Results: The effect of NH4Cl between 0.1 to 0.7 M on the nature of CHW at DME, maintaining the concentrations of Mn(II) at 4.0 ppm and DTC at 3.0 mM (APP-DTC/ABP-DTC) then adjusting the pH to 6.6/7.2 (APP-DTC/ABP-DTC). The polarograms were well-defined in NH₄Cl of 0.4/0.5 M for APP-DTC/ABP-DTC. The peak height decreased beyond this concentration and therefore 0.4/0.5 M (APP-DTC/ABP-DTC) concentrations was kept for more analysis. At fixed concentration of DTC, (3.0 mM APP-DTC/ABP-DTC) and (0.4/0.5 M for APP-DTC/ ABP-DTC) NH₄Cl adjusting the pH to 6.6/7.2 respectively the metal ion concentration of the Mn(II) was adjusted between 0.05 to 7.0 ppm and results of CHWs were studied. The peak current increased linearly with Mn(II) concentration in the range 0.05 to 4.0 ppm for both DTCs. However, the sensitivity of the method was more with APP-DTC/ABP-DTC because of strong complex of Mn(II) and increased catalytic activity. Conclusion: The developed CHW method is highly sensitive, simple and spontaneous for the analysis of Mn(II) in environmental and biological samples. The polarographic reduction of Mn(II) in aqueous solutions in the attendance of DTC displays a catalytic wave as a role of pH, concentration of supporting electrolyte and metal ion. The graphs of catalytic signals as a role of the concentration of dithiocarbamate shows that the signals do not vary linearly with the concentration of dithiocarbamate which the characteristic of Brdicka CHWs. It is presumed that the dithiocarbamate complexes with metal ions involve adsorption process and can be described by a Langmuir adsorption isotherm and the plot of CL/ip Vs CL should be linear. The CHW method is free from interference effect avoiding the removal stages which made towards placing among utmost sensitive methods for the analysis of Mn(II) in different Environmental and Biological samples.

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