Biosensors & Bioelectronics

Since testing for circulating vitamin D concentrations is relatively expensive and time consuming, rapid means of measurement are desired. As a step towards this goal, enzyme-modified electrodes responsive to 25-hydroxyvitamin D3 (25(OH)D3) have been developed. To make the enzyme, a synthetic gene encoding a human cytochrome P450 27B1 (CYP27B1) enzyme, which is a mitochondrial type heme-thiolate monooxygenase that converts 25(OH)D3 into 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), was expressed and purified. The CYP27B1 enzyme was combined with NADPH-adrenodoxin reductase (ADR) and adrenodoxin (ADX) and activity was characterized using liquid chromatography mass spectrometry (LC-MS/MS). It was found that dihydroxyvitamin D3 isomers were produced in addition to 1,25(OH)2D3. The enzyme was immobilized on glassy carbon electrodes using pH-adjusted Nafion® along with cobalt sepulchrate trichloride (Co(sep)3+) as a redox mediator and electrode performance was characterized using cyclic and square wave voltammetry. The results demonstrate detection of 25(OH)D3 in buffer within the physiological range (5-200 ng/ml).

Fiber optic sensors (FOSs) are optical fiber based sensing devices that have been widely used to detect physical, chemical and biological parameters. Polymer optical fibers (POFs), an important type of optical fibers, have been stifled their talents in the field of optical sensing due to the overwhelming popularity of glass optical fibers (GOFs). The unique physical and chemical properties of POFs start attracting interests to be utilized in the fabrication of high performance sensors in recent years. This article reviews the recent progress of POFs based FOSs. In particular, the article will focus on novel techniques implemented on the POF sensor fabrication, including monolayer graphene, evanescent wave absorption, localized surface plasmon resonance and fiber Bragg grating.

RNA interference (RNAi) is one of the most exciting and revolutionary new approaches to therapies that have attracted considerable amount of attention within the last few decades. Interfering RNAs (iRNA) are a major biological macromolecules that regulate specific gene sequencing, silencing and down regulating. Non coding RNA may lead to the development of a new range of potentially thousands of therapeutics. If efficiently used, iRNA is considered as a potent therapeutic agent for different disease types including viral diseases and cancer. However, the major obstacle that stands in the way of realization of such therapies is the in vivo delivery of RNAi fragments, like small interfering RNAs (siRNAs). The optimal approach to deliver si RNAs would be one to guarantee targeted delivery and high stability, a method that can protect the delivered material from undesirable immune response. In this review, we will shed the light on the use of biocompatible nanoparticlesas safe delivery vehicles of genetic material.

An electro-optic dendrimer (EO dendrimer) material has been designed for high power terahertz generation. An ordinary poly (amidoamine organosilicon) (PAMAMOS) dendrimer was modified via doping and poling to generate a high electro-optic coefficient nanomaterial. Measured EO coefficient varied from ~130 pm/V at 633 nm to ~90 pm/V at 1553 nm. An emitter designed from this EO dendrimer generates milliwatts of continuous wave (CW) terahertz radiation (T-ray) when pumped by a CW laser of suitable wavelength. The mechanism termed as the dendrimer dipole excitation (DDE) works via excitation of the dipole population generated by the doping process. The doping protocol also generates a distribution of dipole moments, as opposed to fixed dipoles in the lattice of a crystalline material; thus, when excited by a suitable pump laser, these dipoles radiate a broadband frequency that range from 0.1 THz to ~ 30 THz. A terahertz time-domain spectrometer (TeraSpectra) was designed with this DDE terahertz source. As a test of the spectrometer functionality, a standard polyethylene calibration was conducted. It was found that TeraSpectra reproduces several known absorbance peaks of polyethylene. It also produces additional absorbance peaks not observed before. It is surmised that the ultra-high sensitivity of T-ray enables observation and discovery of additional absorbance peaks that are not visible via other spectroscopy such as visible, UV, FTIR or Raman.

In this paper, a novel antibiotic modified carbon paste electrode (AMX-CPE) was fabricated for the directly determination of bacteria, such Staphylococcus aureus in physiological media. Electrochemical properties and morphological study of the modified electrode were greatly studied. We report a sensitive electrochemical voltammetric method for the immediate bacteria analyzing. A Staphylococcus bacterium adsorbed on an AMX-CPE surface and provides facile electrochemical quantitative methods for electroactive bacteria. Operational parameters have been optimized, and the stripping voltammetric performance has been studied using cyclic voltammetry (CV). The peaks current intensity is highly linear, with a good sensitivity of AMX-CPE.

The nanoparticles of gold and cadmium tellurium quantum dot (CdTe QD) are effective systems for the detection and quantitative removal of chlorpyrifos which is a commonly used pesticide found in surface water of developing nations. Gold nanoparticles coated with citrate changes its color from pink to purple in the presence of chlorpyrifos. Unique CdTe QDs were developed and functionalized by using glucose oxidase for detection of chlorpyrifos. Change in absorbance related to the change in H2O2 concentration. In the solution phase, chlorpyrifos adsorb onto the CdTe QDs surface. During this prolonged interaction, change in color takes place and adsorbed chlorpyrifos becomes precipitated. Thus complete removal of this chlorpyrifos occurs when contaminated water is passed over different CdTe QDs supported on some surface such as alumina. We believe that this method has great potential in the purification of drinking water using gold and CdTe QD nanoparticles.

Poly (Patton and Reeder’s) modified carbon paste electrode was fabricated and it was employed to study the electrochemical response of folic acid (FA) in phosphate buffer solution (PBS) of pH 7.4 by cyclic voltammetric (CV) technique. The results obtained at Poly (Patton and Reeder’s) modified carbon paste electrode shows a good electrocatalytic activity towards the oxidation of FA. The lower limit of detection of FA was found to be 1.88×10-8 M by CV technique. The parameters like effect of concentration and scan rate reveal the electrode process was controlled by adsorption of an analytes. The poly (Patton and Reeder’s) modified carbon paste electrode was used for the simultaneous determination of FA and uric acid (UA) at physiological pH.