No abstract

A new electrochemical DNA biosensor based on mercaptopropionic acid (MPA)-capped ZnS quantum dots (MPA-ZnS QDs) immobilization matrix for covalent binding with 20-base aminated oligonucleotide has been successfully developed. Prior to the modification, screen-printed carbon paste electrode (SPE) was self-assembled with multilayer gold nanoparticles (AuNPs) and cysteamine (Cys). The inclusion of MPA-ZnS QDs semiconducting material in modified electrodes has enhanced the electron transfer between the SPE transducer and DNA leading to improved bioanalytical assay of target biomolecules. Electrochemical studies performed by cyclic voltammetry (CV) and differential pulsed voltammetry (DPV) demonstrated that the MPA-ZnS QDs modified AuNPs electrode was able to produce a lower charge transfer resistance response and hence higher electrical current response. Under optimal conditions, the immobilized synthetic DNA probe exhibited high selectivity towards synthetic target DNA. Based on the DPV response of the reduction of anthraquinone monosulphonic acid (AQMS) redox probe, the MPA-ZnS QDs-based electrochemical DNA biosensor responded to target DNA concentration from 1 × 10−9 μM to 1 × 10−3 μM with a sensitivity 1.2884 ± 0.12 µA, linear correlation coefficient (R2) of 0.9848 and limit of detection (LOD) of 1 × 10−11 μM target DNA. The DNA biosensor exhibited satisfactory reproducibility with an average relative standard deviation (RSD) of 7.4%. The proposed electrochemical transducer substrate has been employed to immobilize the aminated Arowana fish (Scleropages formosus) DNA probe. The DNA biosensor showed linearity to target DNA from 1 × 10−11 to 1 × 10−6 µM (R2 = 0.9785) with sensitivity 1.1251 ± 0.243 µA and LOD of 1 × 10−11 µM. The biosensor has been successfully used to determine the gender of Arowana fish without incorporating toxic raw materials previously employed in the hazardous processing conditions of polypyrrole chemical conducting polymer, whereby the cleaning step becomes difficult with thicker films due to high levels of toxic residues from the decrease in polymerization efficacy as films grew.

The aim of this work is to determine the concentration of mercury in body lotion from several brands that are available in Banda Aceh. This research expected to provide information for the public and government related to the negative effects of harmful cosmetics that widely circulated. This information is useful into consideration of policy-making and monitoring the use of Hg metal. This study determined the type of body lotion cosmetics containing Hg metal by using Cold Vapor Atomic Absorption Spectroscopy (CVAAS) method. There are 22 samples and 11 of them have been selected by purposive sampling. The standard Hg calibration curve produces a linear line with the equation y = 0.0874x + 0.0729, and the correlation coefficient (R 2) value of 0.9726. LOD value is 0.004854 ppb, and LOQ is 0.01681 ppb. The positive results were obtained from samples code TB3= 0.046, TB6= 0.01, and TB13= 0.004 ppb respectively. These results indicated the mercury level was still lower than 1 mg/L the threshold by drug and food control centers (BPOM).

The use of the notorious synthetic dye, rhodamine B, in food and beverage products has been widely reported. This application urges the need to develop an analytical method that can provide reliable rhodamine B data with an easy operational technique. Therefore, this research is aimed to develop an Arduino Uno-based TCS3200 color sensor and study its application to determine rhodamine B levels in syrup. The design of the analytical instrument included TCS3200, an Arduino Uno microcomputer, an Integrated Development Environment (IDE) software, a black box container, and a 24 × 2 matrix display screen, where samples were prepared via absorption using wool thread. With a linear range of 1–20 mg/L, our proposed colorimetric sensor had recoveries of 96.25–110.3%, which was better compared to that was obtained from the UV-vis (81.8–100.6%) method. The detection and quantification limits of the sensor were 2.766 and 8.383 mg/L, respectively. The syrup samples used in this study were purchased from the local stores in Banda Aceh. Based on the proposed TCS3200 color sensor, the highest rhodamine B concentration from the syrup sample was 16.74 mg/L. The t-test analysis in this study revealed that the Rhodamine B levels quantified using the newly developed TCS3200 color sensor were not statistically or significantly different from the UV-Vis spectrophotometer method.