Arunkumar Rengaraj

Porous Covalent Triazine Polymer as a Potential Nanocargo for Cancer Therapy and Imaging.

A microporous covalent triazine polymer (CTP) network with a high surface area was synthesized via the Friedel-Crafts reaction and employed as a potential transport system for drug delivery and controlled release. The CTP was transformed to the nanoscale region by intense ultrasonication followed by filtration to yield nanoscale CTP (NCTP). This product showed excellent dispersibility in physiological solution while maintaining its chemical structure and porosity. An anticancer drug, doxorubicin (DOX), was loaded onto the NCTP through hydrophobic and π-π interactions, and its release was controlled at pH 4.8 and 7.4. The NCTP showed no toxicity toward cancer or normal cells, but the NCTP-DOX complex showed high efficacy against both types of cells in vitro. In-vitro cell imaging revealed that NCTP is a potential material for bioimaging. The potency of NCTP on cellular senescence was confirmed by the expression of senescence associated marker proteins p53 and p21. These results suggest that NCTP can be used as a new platform for drug delivery and imaging with potential applications in diagnosis and therapy.

Electrodeposition of flower-like nickel oxide on CVD-grown graphene to develop an electrochemical non-enzymatic biosensor

We demonstrated a non-enzymatic cholesterol sensor based on a nickel oxide (NiO) and high quality graphene composite for the first time. Graphene was grown by a chemical vapor deposition technique (CVD). The nanocomposite was fabricated through the electrodeposition of nickel hydroxide onto the surface of the CVD-grown graphene, which was followed by thermal annealing. The successful formation of the NiO/graphene composite was confirmed by X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. The deposition of flower-like NiO onto the graphene surface was confirmed by scanning electron microscopy. Electrochemical analyses were conducted to investigate the characteristics of the sensor during the detection of cholesterol. The sensor showed a high sensitivity of 40.6 mA μM-1 cm-2, a rapid response time of 5 s, and a low detection of limit of 0.13 μM. We also investigated the effects of common interfering substances on the ability of the sensor to detect cholesterol. Furthermore, we successfully determined the cholesterol in a milk sample using the developed sensor. The composite electrode exhibited excellent detection of cholesterol with good reproducibility and long-term stability owing to the combined effects of NiO and graphene.

Electrochemical coupled immunosensing platform based on graphene oxide/gold nanocomposite for sensitive detection of Cronobacter sakazakii in powdered infant formula

A sensitive electrochemical immunosensing platform for the detection of Cronobacter sakazakii was developed using a graphene oxide/gold (GO/Au) composite. Transmission electron microscopy showed that the Au nanoparticles, with an average size of < 30 nm, were well dispersed on the GO surface. For the detection of C. sakazakii, a polyclonal anti-C. sakazakii antibody (IgG) was covalently immobilized to the Au nanoparticles on the surface of the GO/Au composite coated glassy carbon electrode (GCE). The electrochemical sensing performance of immunofunctionalized GCE was characterized by cyclic voltammetry and differential pulse voltammetry. Under optimized conditions, in pure culture there was a linear relationship between electrical signal and C. sakazakii levels over the range 2.0 × 102-2.0 × 107 cfu/mL (R2 = 0.999), with a detection limit of 2.0 × 101 cfu/mL. The total analytical time was 15 min per sample. The C. sakazakii electrochemical immunosensing assay was able to successfully detect 2.0 × 101 cfu/mL of C. sakazakii in artificially contaminated powdered infant formula without any enrichment or pre-enrichment steps. Furthermore, the recovery rates of the C. sakazakii electrochemical immunosensing assay following spiking of powdered infant formula with different concentrations of C. sakazakii (cfu/mL) were 82.58% at 2.0 × 101 cfu/mL, 84.86% at 2.0 × 102 cfu/mL, and 95.40% at 2.0 × 103 cfu/mL. The C. sakazakii electrochemical immunosensing assay had good selectivity, reproducibility, and reactivity compared with other Cronobacter spp. and/or pathogens belonging to other genera, indicating its significant potential in the clinical diagnosis of C. sakazakii.

PAMAM/5-fluorouracil drug conjugate for targeting E6 and E7 oncoproteins in cervical cancer: a combined experimental/in silico approach

In the present study, poly(amidoamine)/5-fluorouracil (PAMAM/5-FU) was prepared and used as a conjugate system for delivering drugs to target E6 and E7 oncoproteins, which are predominant in cervical cancers. Specifically, molecular docking analysis was used to investigate the interaction between the PAMAM/5-FU and E6/E7 oncoproteins, which showed that the PAMAM/5-FU conjugate had a higher affinity for the oncoprotein than for 5-FU. Different generations of PAMAM dendrimers (0.5G, 1.0G, 1.5G, 2.0G, and 2.5G) were synthesized, characterized and tested as drug carriers for 5-FU. The PAMAM and PAMAM/5-FU drug conjugate showed less toxicity over COS-7 and HeLa cell lines. Laser confocal imaging and western blotting for tumor suppressor proteins pRb and p53 were used to confirm the interaction of PAMAM/5-FU with E6/E7 oncoproteins. Hematological analysis of PAMAM/5-FU using BALB/c female mice with cervical cancer confirmed the less toxic nature of this material. Based on these results, the developed PAMAM/5-FU conjugate is a potential candidate for the treatment of cervical cancer.

Adsorption of rare earth metals (Sr2+ and La3+) from aqueous solution by Mg-aminoclay–humic acid [MgAC–HA] complexes in batch mode

The recoveries of Sr2+ and La3+ as rare earth metals (REMs) were studied using Mg-aminoclay–humic acid [MgAC–HA] complexes prepared by self-assembled precipitation due to electrostatic attraction between water-solubilized [MgAC] and water-soluble [HA], and were compared with the recoveries using [MgAC] and [HA]. The influences of pH and Sr2+ and La3+ concentrations in single and binary systems were evaluated. The adsorbents before/after adsorption of Sr2+ and La3+ were characterized by (1) scanning electron microscopy (SEM) micrographs, (2) Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure (EXAFS) spectra, and by (3) powder X-ray diffraction (XRD) pattern analysis. After fitting Langmuir and Freundlich isotherms, the Langmuir model was found to present better matches than the Freundlich one: the maximum adsorption capacities of Sr2+ and La3+ were 0.12 mg g−1 and 4.76 mg g−1 in the binary system at room temperature, and the optimal recovery pH was ∼8.0. In practical seawater meanwhile, the recoveries of Sr2+ and La3+ by [MgAC–HA] complexes were the highest in the binary system. However, with further recycling runs, the recoveries of Sr2+ and La3+ were critically diminished due to disassembly in [MgAC–HA] complexes under acidic conditions. Thus, for the purposes of industrial application, we are currently pursuing the enhancement of recyclability for [MgAC–HA] complexes by their encapsulation or direct hydrogel formation.

Electrochemical determination of chloramphenicol using a glassy carbon electrode modified with dendrite-like Fe 3 O 4 nanoparticles

In this study, magnetite (Fe3O4) nanoparticles were electrochemically synthesized in an aqueous electrolyte at a given potential of -1.3 V for 180 s. Scanning electron microscopy revealed that dendrite-like Fe3O4 nanoparticles with a mean size of < 80 nm were electrodeposited on a glassy carbon electrode (GCE). The Fe3O4/GCE was utilized for sensing chloramphenicol (CAP) by cyclic voltammetry and square wave voltammetry. A reduction peak of CAP at the Fe3O4/GCE was observed at 0.62 V, whereas the uncoated GCE exhibited a very small response compared to that of the Fe3O4/GCE. The electrocatalytic ability of Fe3O4 was mainly attributed to the formation of Fe(VI) during the anodic scan, and its reduction to Fe(III) on the cathodic scan facilitated the sensing of CAP. The effects of pH and scan rate were measured to determine the optimum conditions at which the Fe3O4/GCE exhibited the highest sensitivity with a lower detection limit. The reduction current for CAP was proportional to its concentration under optimized conditions in a range of 0.09-47 μM with a correlation coefficient of 0.9919 and a limit of detection of 0.09 μM (S/N=3). Moreover, the fabricated sensor exhibited anti-interference ability towards 4-nitrophenol, thiamphenicol, and 4-nitrobenzamide. The developed electrochemical sensor is a cost effective, reliable, and straightforward approach for the electrochemical determination of CAP in real time applications.