Current Analytical Chemistry - Volume 18, Issue 4, 2022

Background: While significant advancement has made to reduce the percentage of mortality during the treatment of chronic diseases, however, there are several challenges associated with the healthcare sector for the improvement of human lifestyle. Recently, the development of specific, sensitive, accurate, quick, low-cost and easy-to-use diagnostic tools are in great demand. Nanodiagnostic is defined as an application of nanotechnology to medical diagnostics that offers several unique opportunities to treat chronic diseases successfully and more effectively. Methods: This review is aimed at focusing a wide range of nano-based platforms, including smart nanomaterials and their nanodevices for point-of-care applications. Results: The current state-of-the-art and most promising nanodiagnostics include miniaturized diagnostic tools, nanorobotics and drug delivery systems. The present review also highlights the drawbacks and potential developments that are associated with nanodiagnostics for point-of-care applications in the treatment of chronic diseases. Conclusions: Even though several researchers have dedicated their time to developing highly advanced smart nanodevices for point-of-care applications, but reliability and continuous monitoring of patient’s health are questionable. Moreover, researchers and administrators need to focus on the designing of a roadmap for the availability of nanodevices to rural patients to undergo insitu diagnosis as well as reusability of the devices which could reduce the percentage of mortality and cost of the testing.

Background: The invention of Surface 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 are defined as nanoclusters (NCs) and they possess distinct optical properties. In addition, the excited electrons from absorption bands result in the emission of positive luminescence associated with the quantum size effect in which separate energy levels are produced. Results: It is demonstrated that fluorescent-based SERS investigations of metal nanoparticles show more photostability, high compatibility, and good water solubility, which has resulted in high sensitivity, better imaging and sensing experience in 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 to some benefits, including cost-effectiveness, easy synthesis routes and less consumption of sample volumes. Outcomes of this study confirm that SERS-based fluorescent nanoclusters could be one of the thrust research areas in biochemistry and biomedical engineering.

Background: Mexiletine belongs to the β-amino-aryl-ether group of pharmaceutical and applied in the diagnosis of antiarrhythmics, allodynia, and myotonic disorders. In its chemical structure, it possesses a chiral center and practiced in the form of the racemic mixture. The production and accessibility of mexiletine have accompanied with a meaningful development in awareness of its pharmacologic actions. But in clinical arrhythmias and binding experiments on cardiac sodium channels, the (R)-enantiomer of mexiletine is more potent than the (S)-enantiomer. Also, (S)-enantiomer is further active in the diagnosis of allodynia than the (R)-enantiomer Methods: During the last two decades, chromatographic techniques such as HPLC, and GC coupled with mass spectrometry or field ionization detector have been used for the stereoselective analysis of MEX enantiomers Results: The direct enantioresolution deals with the use of chiral stationary phases (CSPs) with or no pre-derivatization which depend on a chromophoric entity in the racemates whereas the indirect HPLC process involves the use of chiral derivatization reagents (CDR) for the synthesis of diastereomeric derivatives of racemates. Different techniques have their strengths and weaknesses. Conclusion: Regulation of enantiomeric purity and estimation of particular enantiomers of drug molecules stay an essential topic for therapeutic, diagnostic, and regulatory uses and to promote a precise assessment of the hazards to human health by false enantiomers. This review aims to offer a systematic survey of the analytical methods (chromatography based) used in the enantioselective analysis of MEX developed in the last two decades (the year 2000 onwards).

Background: The introduction of inorganic fillers into the polymer matrix (with multiplicity in functionalization) augments the specific properties of such materials. One such method employed here, which is environmental friendly and facile is the sol-gel synthesis Objective: The nanocomposite synthesized by the above-mentioned method was primarily utilized for ion-exchange applications in general and cation exchange in particular. The ZrP based nanocomposite (PS/AG/ZrP) has been examined (as a photocatalyst) for the elimination of toxic cationic dye, methylene blue (Mb) from the wastewater by the mechanism of photodegradation. This study provides the experimental evidence and discussion of the different physicochemical characteristics of the synthesized nanocomposite. Methods: Herein, we synthesized zirconium phosphate (ZrP)-linked-potato starch/sodium alginate nanocomposite ion exchanger (PS/AG/ZrP) employing facile sol-gel method. Highly sophisticated techniques like FTIR, TGA, SEM, TEM, XRD & UV-Vis were subjected to characterize the PS/AG/ZrP nanocomposite Results: The ion exchange (IE) results show that the nanocomposite ion exchanger (PS/AG/ZrP-6) exhibited higher IEC (2.1meq/g) and thermal stability as conferred from IEC and TGA studies. Using UV-Vis irradiation, photocatalytic results revealed that 74.5% of Mb dye was degraded by novel nanocomposite (PS/AG/ZrP) within 50 minutes Conclusion: The results discussed reveal that the nanocomposite (PS/AG/ZrP-6) is a potential candidate for ion exchange applications vis-à-vis a photocatalyst for the remediation of wastewater as the time demands. The nanocomposite (PS/AG/ZrP-6) successfully characterized through various techniques and utilized as a potential ion exchanger and a photocatalyst for the dye degradation (MB) under UV-Vis irradiation.

Background: The nanocomposites are formed by introducing inorganic nano-clusters, fullerenes, clays, metals, oxides with numerous organic polymers. The assembly of these materials exhibits better properties such as catalytic, thermal stability and adsorption properties, than the individual materials. Objective: The nanocomposite synthesized here by the sol-gel method was primarily evaluated for cation exchange properties viz, elution concentration, elution behavior, and the effect of temperature on ion-exchange capacity. The synthesized composite was used as an electroactive component for the fabrication of the Hg²⁺ ion-selective membrane electrode. Methods: The sol-gel technique was used to synthesize multi-walled carbon nanotubes Zr(IV) phosphate composite cation exchanger. By the technique of solution casting, the material as an electroactive part was used for the fabrication of mercury ion-selective membrane electrode. The potential response of the electrode was also investigated as a function of membrane composition and plasticizer. Results: The composite cation exchanger exhibited 1.8 meq g^-1 ion-exchange capacity (IEC). It retained almost 65% of its initial IEC up to a temperature of 400°C. Distribution studies showed the selective nature of the composite for Hg(II) ions. The ion-selective membrane electrode exhibited a typical Nernstian response towards Hg²⁺ ions in the concentration range 1×10^-1-1×10^-1 M. Conclusion: The results discussed reveal that the new cation composite exchanger-multi-walled carbon nanotubes Zr (IV) phosphate exhibited excellent cation exchange properties and was found to be preferentially selective towards the Hg²⁺ ions. It was also used as an indicator electrode in the titration of Hg²⁺ ions using ethylenediaminetetraacetic acid as a titrant.

Aim: The main strategy of this study is to develop a novel ionic liquid functionalized 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 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 of all age groups. So, this work is aimed at developing a novel electrochemical sensor for the determination of rifampicin (RIF) in pharmaceutical samples Objective: The study aimed to synthesize and characterize the novel liquid functionalized metal nanocomposite. A glassy carbon electrode is fabricated with potent electrode modifiers whose applicability as electrocatalysis agents towards rifampicin is investigated. Methods: In this work, a nanocomposite based on trihexyltetradecylphosphonium-bis-(2,4,4- trimethylpentyl)-phosphinate ([P14, 6, 6, 6] [(C8H17)2 PO2)]) ionic liquid functionalized titanium oxide nanoparticles (TiO2NPs) and multiwalled carbon nanotubes (MWCNTs) was used in the modification of a highly sensitive electrochemical sensor for quantification of rifampicin in pharmaceutical formulations. The modified glassy carbon electrode (GCE) was characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). Results: The electrochemical behavior 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 was 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 a 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: Nanomaterials have facilitated remarkable advances in the remediation of many environmental problems. A few studies have tackled the removal of Co (II) from aqueous solutions using nanomaterials. Herein, we studied the retention kinetics of cobalt species on carbon nanotubes (CNTs) bearing different amounts of TiO2 and Fe3O4/TiO2 nanomaterials individually. Methods: CNTs and their TiO2/Fe3O4/TiO2-modified nanomaterials were well characterized. Cobalt retention by these adsorbents was investigated considering different influencing factors such as Co (II) content, solution pH, and time. The kinetic data were fitted with pseudo-first-order, pseudosecond- order rate models, and intra-particle diffusion models for better elucidation of the mechanism of Co retention. Results: XRD evidenced the formation of TiO2 and Fe3O4/TiO2. High loads of both oxides were needed for higher and faster Co retention by CNTs. Co retention capacity increased with increasing the solution pH. The pseudo-second-order model presented the kinetics of Co retention at 30°C, and 48% of available capacity was attained within the first hour of interaction by CNT-TiO2 and with a moderate S/L ratio of 0.5 g/L. Co retention was increased with the amount of oxide to reach a maximum value of 16. 40 mg/g (90.2% TiO2) and 13.60 mg/g (48.2% Fe3O4/TiO2). The JovanoviĦ#135; equilibrium model predicted the maximum retention values as the nearest to the experimental ones. Conclusion: The potential of CNT-Fe3O4/TiO2 nanomaterials has been successfully demonstrated for the removal of cobalt, which makes them highly attractive and cost-effective adsorbents for wastewater treatment. The reported retention and removal rate values were relatively better than those seen in the literature. Loading different active oxides by CNTs is an interesting research area as selective adsorbents can be fabricated with affordable experimental costs.

As a vital amino acid in the human body, tyrosine is indispensable in various biological processes, and therefore its accurate and simple determination is of crucial importance. In this work, a facile approach was developed to construct a molecularly imprinted sensor for tyrosine via co-electrodeposition of chitosan, β-cyclodextrin and tyrosine on the surface of indium tin oxide that was pre-coated with multi-walled carbon nanotubes (MWNTs). Methods: Benefitting from the excellent film-forming ability and the rich functional groups to form a hydrogen bond with target molecules, chitosan was utilized to form a recognition matrix. MWNTs and β-cyclodextrin were then introduced to enhance the selectivity and sensitivity to tyrosine, due to the subtle electronic, catalytic properties and possible π-π interaction of MWNTs with tyrosine, as well as recognition ability of β-cyclodextrin. The morphology of the imprinted films was characterized by a scanning electron microscope. The electrochemistry and tyrosine sensing performance were investigated in detail by cyclic voltammetry and chronoamperometry. Results: Amperometry results showed that the imprinted sensor exhibited a linear range of 1.0×10−6 to 1.0×10−4 M and 1.0×10−4 to 1.0×10−3 M for tyrosine determination, with a detection limit of 6.0 × 10−7 M (S/N=3). Moreover, a satisfactory recovery in the range of 99.0% to 105.1% was obtained with the application of the imprinted sensor in artificial urine samples analysis. Conclusion: The imprinted electrode is reusable with satisfactory reproducibility and stability in tyrosine determination.