Shabi Abbas Zaidi

Recent developments in nanostructure based electrochemical glucose sensors.

Diabetes is a major health problem causing 4 million deaths each year and 171 million people suffering worldwide. Although there is no cure for diabetes, nevertheless, the blood glucose level of diabetic patients should be monitored tightly to avoid further complications. Thus, monitoring of glucose in blood has become an inevitable need leading to fabrication of accurate and sensitive advanced blood sugar detection devices for clinical diagnosis and personal care. It led to the development of enzymatic glucose sensing approach. Later on, various types of nanostructures have been utilized owing to their high surface area, great stability, and cost effectiveness for the fabrication of enzymatic as well as for nonenzymatic glucose sensing approach. This work reviews on both categories, however it is not intended to discuss all the research reports published regarding nanostructure based enzymatic and nonenzymatic approaches between mid-2010 and mid-2015. We, do, however, focused to describe the details of many substantial articles explaining the design of sensors, and utilities of the prepared sensors, so that readers might get the principles behind such devices and relevant detection strategies. This work also focuses on biocompatibility and toxicity of nanomaterials as well as provides a critical opinion and discussions about misconceptions in glucose sensors.

Molecular imprinted polymers as drug delivery vehicles

Abstract This review is aimed to discuss the molecular imprinted polymer (MIP)-based drug delivery systems (DDS). Molecular imprinted polymers have proved to possess the potential and also as a suitable material in several areas over a long period of time. However, only recently it has been employed for pharmaceuticals and biomedical applications, particularly as drug delivery vehicles due to properties including selective recognition generated from imprinting the desired analyte, favorable in harsh experimental conditions, and feedback-controlled recognitive drug release. Hence, this review will discuss their synthesis, the reason they are selected as drug delivery vehicles and for their applications in several drug administration routes (i.e. transdermal, ocular and gastrointestinal or stimuli-reactive routes).

Dual‐templates molecularly imprinted monolithic columns for the evaluation of serotonin and histamine in CEC

To extend the application of molecularly imprinted polymers, the dual‐templates molecularly imprinted monolithic columns were developed in a capillary format. Two templates serotonin and histamine were simultaneously imprinted using two different functional monomers such as methacrylic acid (MAA) and methylenesuccinic acid (MSA) in a mixture of ethylene glycol dimethacrylate (EDMA) as a cross‐linker and AIBN as polymerization initiator dissolved in DMF as porogen. The resulting molecular imprinted polymers (MIPs) were characterized based on their performance in the CEC separation of two imprinted templates. The optimization parameters such as pH, ACN composition, and concentration of the eluent were varied to achieve best resolution and efficiency for CEC separation of templates with each MIP column. It was found that the MIP monolith column fabricated using MSA offered better resolution and separation efficiency compared to column fabricated with MAA. This work utilized the dual‐templates imprinting approach successfully and broadens the scope of multi‐templates imprinting capabilities in capillary format in CEC application.

Latest trends in molecular imprinted polymer based drug delivery systems

Molecular imprinted polymers (MIP) are promising and versatile materials that have been used for the determination of many different analytes. In the last few years, MIPs have been substantially employed for various biomedical applications, especially drug delivery systems (DDS), owing to some of their unique features such as specific recognition by imprinting the desired analyte, suitability in rough experimental conditions, and targeted and sustained drug release. Hence, this review is focused on the development of strategies undertaken for their application to drug delivery systems involving several different administration routes (i.e. transdermal, ocular and oral routes) published between 2014 and now. Herein, we have also highlighted the summaries of published works, in order to gain a better understanding of the synthetic strategies employed and the analytical performances of the reported MIPs, in addition to pointing out the challenges and future perspectives of MIP based DDS.

A review on the latest developments in nanostructure-based electrochemical sensors for glutathione

Glutathione, a low molecular mass thiol compound, is considered a vital biomarker for various disease and cancers owing to the variation in the level of GSH from its normal level in the micromolar to millimolar range in biological fluids and cells. Thus, it is of foremost importance to confirm the accurate and reliable concentration of it in order to provide appropriate treatments to patients. Nanostructure modified electrochemical sensors provide a sensitive, fast, and economic remedy for glutathione analysis. This short review is focused on the latest developments in nanostructure-based sensors from 2012 onward.

Facile and efficient electrochemical enantiomer recognition of phenylalanine using β-Cyclodextrin immobilized on reduced graphene oxide

This work demonstrates the facile and efficient preparation protocol of β-Cyclodextrin-reduced graphene oxide modified glassy carbon electrode (β-CD/RGO/GCE) sensor for an impressive chiral selectivity analysis for phenylalanine enantiomers. In this work, the immobilization of β-CD over graphene sheets allows the excellent enantiomer recognition due to the large surface area and high conductivity of graphene sheets and extraordinary supramolecular (host-guest interaction) property of β-CD. The proposed sensor was well characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and electrochemical impedance spectroscopy (EIS) techniques. The analytical studies demonstrated that the β-CD/RGO/GCE exhibit superior chiral recognition toward L-phenylalanine as compared to D-phenylalanine. Under optimum conditions, the developed sensor displayed a good linear range from 0.4 to 40µM with the limit of detection (LOD) values of 0.10µM and 0.15µM for l- and D-phenylalanine, respectively. Furthermore, the proposed sensor exhibits good stability and regeneration capacity. Thus, the as-synthesized material can be exploited for electrochemical enantiomer recognition successfully.

A novel and highly sensitive electrochemical monitoring platform for 4-nitrophenol on MnO2 nanoparticles modified graphene surface

4-Nitrophenol (4-NP) has been considered a deadly pollutant causing slow photosynthetic reactions, carcinogenicity and other related serious detrimental effects toward human and aquatic life. In this work, a novel, sensitive and reliable electrochemical sensor was prepared by electrodepositing manganese dioxide nanoparticles (MnO2-NPs) over reduced graphene oxide (RGO) for the determination of 4-NP. The successful synthesis of graphene oxide (GO), reduced graphene oxide, and MnO2-NPs were characterized by scanning electron microscopy (SEM). The electrochemical behaviors of 4-NP on MnO2–RGO/GCE and various other modified electrodes were investigated and compared. It was observed that only the MnO2–RGO/GCE electrode exhibited well defined redox peak currents toward 4-NP. Under optimized conditions, the reduction peak current varies linearly with the concentration of 4-NP ranging between 0.02–0.5 μM and 2–180 μM and a detection limit (LOD) of 10 nM (S/N = 3) was estimated. Furthermore, the as-fabricated sensor displayed high selectivity, stability, reproducibility and excellent recoveries of 4-NP in various water samples spiked with 4-NP. Thus, the proposed method provides an outstanding platform for the detection of 4-NP with great ease and reliability.

Recent developments in molecularly imprinted polymer nanofibers and their applications

Molecularly imprinted polymers (MIPs) have been potential and versatile candidates for analyte detection. The ability to create materials with well-controlled nanofibers is of intense interest for a variety of applications. In recent years, two fascinating materials MIPs and nanofibers have been combined to facilitate and achieve greater benefits through pre-synthesized MIP nanoparticle or microsphere encapsulation into nanofibers via electrospinning or direct reaction conditions. On the other hand, there are few excellent reports where MIP reaction constituents were dissolved into uniform and homogeneous electrospinning solutions to achieve MIP electrospun nanofibers. This article is the very first review reporting on the development of MIP nanofiber preparation and their applications for the determination of several valuable compounds in various areas.

Synthesis of Multifunctional Electrically Tunable Fluorine-Doped Reduced Graphene Oxide at Low Temperatures

Doping with heteroatoms is a well-established method to tune the electronic properties and surface chemistry of graphene. Herein, we demonstrate the synthesis of a fluorine-doped reduced graphene oxide (FrGO) at low temperatures that offers multiple opportunities in applied fields. The as-synthesized FrGO product shows a better electrical conductivity of 750 S m-1 than that of undoped rGO with an electrical conductivity of 195 S m-1. To demonstrate the multifunctional applications of the as-synthesized FrGO, it was examined for electromagnetic interference shielding and electrochemical sensing of histamine as an important food biomarker. A laminate of FrGO delivered an EMI shielding effectiveness value of 22 dB in Ku band as compared with 11.2 dB for an rGO laminate with similar thickness. On the other hand, an FrGO modified sensor offered an excellent sensitivity (∼7 nM), wide detection range, and good selectivity in the presence of similar biomarkers. This performance originates from the better catalytic ability of FrGO as compared with rGO, where fluorine atoms play the role of catalytic active sites owing to their high electronegativity. The fluorination reaction also helps to improve the reduction degree of the chemically synthesized graphene, consequently enhancing the electrical conductivity, which is a prime requirement for increasing the electromagnetic and electrochemical properties of graphene.

Cancer Biomarker Immunosensing Monitoring Strategies via Graphene Surface-Engineered Materials

Cancer is the second most dreaded disease responsible to huge number of morbidity and mortality worldwide. By 2030, the global burden is expected to grow to 21.7 million new cancer cases as compared to present estimate of 14.1 million new cancer cases and 8.2 million cancer deaths worldwide. The substances that are produced by cancer or by other cells of the body in response to cancer or certain benign (noncancerous) conditions are called as tumor, or cancer markers (biomarkers). In cancer cells, these biomarkers are produced at much higher levels in cancerous conditions and secreted into the blood, urine, stool, tumor tissue, or other tissues or bodily fluids of some patients suffering from cancer. The sensitive and reliable detection of cancer biomarkers provides an effective way for cancer screening and diagnosis, as well as evaluating the pathogenic processes, pharmacological responses to a therapeutic intervention, and prognosis of different cancers. Among many detection strategies, electrochemical immunosensing has attracted considered attention over the past few years due to its intrinsic advantages, such as good portability, low cost, simple instrumentation, and high sensitivity. Furthermore, many approaches, especially the applications of various types of nanomaterials, are being utilized for greater sensitivity resulting from ultralow amount of target tumor markers. Hence, herein, we intend to summarize the selective works on various types of biomarkers and their detection methods using a wide variety of nanomaterials in combination of graphene.