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.

Mikrosensor pendarfluor optik untuk kuantifikasi asid borik dalam sampel makanan telah dibangunkan berdasarkan filem mikrosfera poli(n-butil akrilat) [poli(nBA)]. Pencirian optik reagen alizarin merah S (ARS) terpegun pada filem mikrosfera poliakrilat dengan asid borik telah dilakukan melalui pendekatan transduksi pendarfluor. Reagen ARS telah dijerap secara fizikal pada filem mikrosfera akrilik hidrofobik untuk membentuk mikropolimer kelat dengan sokongan matriks sol-gel untuk mengelakkan larut lesap molekul ARS yang bersifat larut air. Pengkelat ARS yang terpegun pada filem mikrosfera poli(nBA) memberikan tindak balas pengesanan optik yang cepat dalam masa 1 minit. Julat rangsangan linear dinamik yang berguna bagi mikrosensor pendarfluor optik asid borik telah diperoleh antara 1.6 μM dan 32.0 μM asid borik dengan had pengesanan (LOD) pada 1 μM. Mikrosensor pendarfluor optik asid borik berasaskan mikropolimer akrilik menghasilkan prestasi kebolehulangan yang baik dengan nilai sisihan piawai relatif (RSD) yang dicapai dalam julat 3.3-3.6%. Mikrosensor optik yang dibangunkan telah digunakan untuk pengukuran pendarfluor asid borik dalam sampel mi kuning dan mi beras leper (‘hor fun’/’kway teow’) dan tidak menunjukkan perbezaan yang ketara berbanding dengan kaedah rujukan tradisional spektrometri pemancaran plasma-optik berganding secara induktif (ICP-OES).