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In this study, a direct and label-free immunosensor was designed and constructed by modifying the screen-printed electrode with graphene nanoplatelets (GNPs) for the detection of the cardiac troponin T (cTnT). Firstly, GNPs were drop-casted onto carbon working electrode. Monoclonal cTnT antibodies were then immobilized on the GNPs via physical adsorption; finally, BSA was introduced to block non-specific binding sites. The detection of cTnT was performed using an electrochemiluminescence (ECL) technique with tris(bipyridine)ruthenium(II) chloride ([Ru(bpy)3]Cl2) used as a luminophore and TPrA (tripropylamine) as a co-reactant. The ECL intensity was demonstrated to be directly proportional to the cTnT concentration where a linear range from 100 pg mL-1 to 5 fg mL-1 of the cTnT detection was established. An extremely low limit of detection was achieved to be 0.05 fg mL-1 with an outstanding specificity. Additionally, this immunosensor showed excellent percentage recovery for real samples analyses in artificially spiked human serum.

In this work, a nanocomposite of gold nanoparticles (AuNPs), carbon nano-onions (CNOs), single-walled carbon nanotubes (SWCNTs) and chitosan (CS) (AuNPs/CNOs/SWCNTs/CS) was prepared for the development of highly sensitive electrochemical immunosensor for the detection of carcinoembryonic antigen (CEA), clinical tumor marker. Firstly, layer-by-layer fabrication of the CEA-immunosensors was studied using cyclic voltammetry (CV) and square wave voltammetry (SWV). By combining the advantages of large surface area and electronic properties of AuNPs, CNOs, SWCNTs, and film forming properties of CS, AuNPs/CNOs/SWCNTs/CS-nanocomposite-modified glassy carbon electrode showed a 200% increase in effective surface area and electronic conductivity. The calibration plot gave a negative linear relationship between log[concentration] of CEA and electrical current with a correlation coefficient of 0.9875. The CEA-immunosensor demonstrated a wide linear detection range of 100 fg mL−1 to 400 ng mL−1 with a low detection limit of 100 fg mL−1. In addition to high sensitivity, reproducibility and large stability, CEA-immunosensor provided an excellent selectivity and resistant-to-interference in the presence of other antigens in serum and hence a potential to be used with real samples.

Recently, there has been a growing concern of consumers on the authenticity of food ingredients including adulteration with porcine and/or its derivatives. Therefore, this work reports on the development of a novel, simple, sensitive and rapid luminol-based electrochemiluminescence (ECL) technique for Sus scrofa (Porcine) DNA detection. Porcine DNA was firstly amplified using loop-mediated isothermal amplification (LAMP) method and subsequently added to luminol solution for further ECL analysis for quantification. The DNA-luminol complexes were formed causing the diffusion of luminol towards the electrode surface to be slowed down and hindered that resulted in low luminol intensity. The LAMP-ECL sensor is shown to be highly specific, sensitive (≥0.1 pg/μL) and rapid (∼5 min for detection). Hence, by employing this principle with carbon screen-printed electrode (SPE), this technique has a potential to be developed further into a compact biosensor for the verifying food authenticity.

This study reports a new method of fabrication and application of “green” starch nanoparticles (SNPs) from local sago (Metroxylon Sagu) starch granules employing a high-pressure homogenization procedure. This approach is environmentally friendly, highly feasible, low cost and chemical-free with large-scale production capacity. In this work, SNPs' morphological, particle size and thermal properties were studied. The effects of SNPs concentration (ranging from 0 to 8% w/w) as nano-fillers in composite films’ barrier, transparency and contact angle were also investigated. Our results have shown that the fabricated SNPs exhibited excellent uniformity and spherical shapes. Addition of SNPs have demonstrated to enhance polymeric structure of nanocomposite film due to decreased water vapour permeability and increased contact angle. Sago SNPs as fillers pose an excellent prospect in green composites fabrication for material and biomedical purposes with potential application as carriers for drug delivery.

In recent years, tremendous advances have been made in biosensors based on nanoscale electrochemical immunosensors for use in the fields of agriculture, food safety, biomedicine, quality control, and environmental and industrial monitoring. One of the main challenges in biosensors is achieving an extremely low limit of detection. A current trend to address this is fabrication of highly sensitive electrochemical immunosensors through the use of nanotechnology; for example, biofunctionalization of nanomaterials that are used as a catalyst, label or biosensing transducer. This review introduces recent advances in signal amplification strategies for electrochemical immunosensing applications, with a particular focus on nanotechnology. The strategies employed and their general principles to increase sensitivity, as well as the advantages and limitations of electrochemical immunosensors developed to date are also considered.

In this work we exploited the electrostatic interaction of double stranded DNA (dsDNA) with drug components to construct a simple, but highly sensitive, DNA-electrochemical sensor for detecting ciprofloxacin. The following straightforward three-step procedure was performed to determine ciprofloxacin: (i) dsDNA-layer immobilization on the surface of the working graphene-modified screen-printed carbon electrode; (ii) dsDNA-ciprofloxacin interaction for 2 min; and (iii) electrochemical measurement using square-wave voltammetry. An increased oxidation of the guanine component was observed, at +1.0 V, as a result of the electrostatic interaction of positively charged ciprofloxacin with the negatively charged nucleic acid sugar phosphate. Based on the International Conference on Harmonization Guidelines, a linear relationship between the guanine oxidation peak and ciprofloxacin concentration (0.1 to 100 μM) was obtained with a detection limit of 0.1 μM. Our developed sensor is straightforward to construct and use, requiring no multi-step time-consuming preconditioning of electrodes. It is highly sensitive and selective in the detection of ciprofloxacin, and has the potential to be useful in the future fabrication of rapid and portable on-site food safety analysis devices.

A label free electrochemical immunosensor for sensitive detection of porcine serum albumin (PSA) is reported in this work. The immunosensor was constructed by first electrochemically reducing 4-carboxyphenyl diazonium salt, which had been electrochemically generated in situ, to a stable 4-carboxyphenyl layer on carbon nanofiber-modified screen printed electrode. Antibodies were covalently attached onto the electrode using carbodiimide chemistry between the carboxylic groups of the 4-carboxyphenyl layer and amine groups of the antibody. Using the strong affinities of serum albumins towards anions, the increase in cathodic peak current in anionic redox probe after immunocomplex formation with antibodies was used for PSA detection. The reported immunosensor demonstrated a linear range from 0.5 to 500pg/mL for the measurement of PSA with detection limit of 0.5pg/mL in buffer solution. Cross-reactivity studies have shown excellent specificity with satisfactory recovery of PSA in fresh meat samples without the need of sample dilution.