Electrodeposition is an electrochemical method employed to deposit stable and robust gold nanoparticles (AuNPs) on electrode surfaces for creating chemically modified electrodes (CMEs). The use of several electrodeposition techniques with different experimental parameters allow in obtaining various surface morphologies of AuNPs deposited on the electrode surface. By considering the electrodeposition of AuNPs in various background electrolytes could play an important strategy in finding the most suitable formation of the electrodeposited AuNP films on the electrode surface. This is because different electrode roughnesses can have different effects on the electrochemical activities of the modified electrodes. Thus, in this study, the electrodeposition of AuNPs onto the glassy carbon (GC) electrode surfaces in various aqueous neutral and acidic electrolytes was achieved by using the cyclic voltammetry (CV) technique with no adjustable CV parameters. Then, surface morphologies and electrochemical activities of the electrodeposited AuNPs were investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), CV, and electrochemical impedance spectroscopy (EIS). The obtained SEM and 3D-AFM images show that AuNPs deposited at the GC electrode prepared in NaNO₃ solution form a significantly better, uniform, and homogeneous electrodeposited AuNP film on the GC electrode surface with nanoparticle sizes ranging from ∼36 to 60 nm. Meanwhile, from the electrochemical performances of the AuNP-modified GC electrodes, characterized by using a mixture of ferricyanide and ferrocyanide ions [Fe(CN₆)^3–/4–], there is no significant difference observed in the case of charge-transfer resistances (R_ct) and heterogeneous electron-transfer rate constants (k^o), although there are differences in the surface morphologies of the electrodeposited AuNP films. Remarkably, the R_ct values of the AuNP-modified GC electrodes are lower than those of the bare GC electrode by 18-fold, as the R_ct values were found to be ∼6 Ω (p > 0.001, n = 3). This has resulted in obtaining k^o values of AuNP-modified GC electrodes between the magnitude of 10^–2 and 10^–3 cm s^–1, giving a faster electron-transfer rate than that of the bare GC electrode (10^–4 cm s^–1). This study confirms that using an appropriate supporting background electrolyte plays a critical role in preparing electrodeposited AuNP films. This approach could lead to nanostructures with a more densely, uniformly, and homogeneously electrodeposited AuNP film on the electrode surfaces, albeit utilizing an easy and simple preparation method.

Vancomycin-resistant Enterococci (VRE) genes are bacteria strains generated from Gram-positive bacteria and resistant to one of the glycopeptides antibiotics, commonly, vancomycin. VRE genes have been identified worldwide and exhibit considerable phenotypic and genotypic variations. There are six identified phenotypes of vancomycin-resistant genes: VanA, VanB, VanC, VanD, VanE, and VanG. The VanA and VanB strains are often found in the clinical laboratory because they are very resistant to vancomycin. VanA bacteria can pose significant issues for hospitalized patients due to their ability to spread to other Gram-positive infections, which changes their genetic material to increase their resistance to the antibiotics used during treatment. This review summarizes the established methods for detecting VRE strains utilizing traditional, immunoassay, and molecular approaches and then focuses on potential electrochemical DNA biosensors to be developed. However, from the literature search, no information was reported on developing electrochemical biosensors for detecting VRE genes; only the electrochemical detection of vancomycin-susceptible bacteria was reported. Thus, strategies to create robust, selective, and miniaturized electrochemical DNA biosensor platforms to detect VRE genes are also discussed.

This work describes synthesis of gold nanoparticles (AuNPs) of tunable size using the seeding growth method. High concentration of AuNPs of various sizes was synthesized by varying synthesis parameters. The properties were observed using transmission electron microscope (TEM), zetasizernanoZS, X-ray diffractometer (XRD) and UV Vis spectrophotometers. The produced AuNPs were then used in fabrication of glucose sensors with the following structure; Nafion/GOx/AuNPs/ITO. The effect of AuNPs size on glucose sensor properties was studied by measuring electrocatalytic activity of the prepared AuNPs/ITO electrodes using cyclic voltammetry in the range of -0.5 to 0.5 V versus Ag/AgCl reference electrode. Cyclic voltammograms of various sizes of AuNPs tested in 10 mM glucose in 0.01 M PBS. UV-Vis analysis shows the wavelength of AuNPs increases from 518, 519, 523, 525 and 529 for 15 (Au seed), 20, 30, 40 and 50 nm, respectively. Particle size analysis using the zetasizer gave z-average for expected size 20, 30, 40 and 50 nm AuNPs of 29.97, 42.61, 44.16 and 58.78 nm, respectively. All of the z-average is larger than the size expected. The polydispersity index (PDI) for size 20, 30, 40 and 50 nm AuNPs are 0.372, 0.096, 0.112 and 0.102, respectively. XRD analysis matched with (111), (200), (220) and (311) face centered cubic Au planes (ICDD 98-005-0876). The result confirmed that AuNPs is in crystalline structure. For glucose sensor, 30 nm AuNPs has the highest electrocatalytic activity as it has the highest anodic and cathodic peak currents compared to other size of AuNPs. The results obtained could be caused by low PDI value measured using zeta-sizer and the uniform particles size distribution as observed in TEM images.

Fluorescence dyes are based on small organic molecules have become of interest in chemical biology and widely used for cell and intracellular imaging. However, fluorescence dyes have limitations such as photo bleaching, poor photochemical stability and has a short Stokes shift. It is less valuable for long-term cell tracking strategies and has very short lifetime. In order to overcome the problems, dye-incorporated nanomaterials become of interest. Nanomaterials encapsulation provides a protection layer around the fluorescence dye which improves the stability of fluorescence dye. In this study, silica nanoparticles encapsulated with 1,1%-dioctadecyl-3,3,3%,3%-tetramethylindocarbocyanine perchlorate (Dil) was successfully synthesised by using micelle entrapment method to investigate the effect of encapsulation of nanoparticles towards the properties of fluorescent dye. The synthesised nanoparticles (SiDil) was characterised by particle size analyser, Transmission Electron Microscopy (TEM), UV-Vis spectrometer and Fluorescent spectrometer. Observation using TEM showed spherical shape of nanoparticles with 53 nm diameter. Monodispersed and well nanoparticles distribution was confirmed by low polydispersity index of 0.063 obtained by particle size analyser. Furthermore, the photoluminescence properties of the SiDil were evaluated and compared with bare Dil dye. Both SiDil and bare Dil was radiated under 200 W of Halogen lamp for 60 minutes and the absorbance intensity was measured using UV-Vis spectrometer. The result showed more stable absorbance intensity for SiDil compared to bare Dil dye, which indicated that Si nanoparticles encapsulation improved the photostability property.

The advancement of nanoparticle-based approaches such as quantum dots (QDs), metallic (Au and Ag) NPs, silica NPs and other types of nanomaterial have led to a large variety of biomolecular imaging and labelling reagents with controlled size and shaped to overcome the limitation of conventional organic dye. In this study, the yellowish green color of fluorescein dye was encapsulated into colloidal silica nanoparticles by using micelle entrapment approach. Two different size of silica nanoparticles encapsulated fluorescein dye (27.7 ± 5.6 and 46.73 ± 4.3 nm) with spherical and monodispered of nanoparticles were synthesised by varying the volume of co-solvent during the synthesis process. The particles size, particles morphology, absorption spectrum and the photostability of fluorescein dye was measured by using dynamic light scaterring (DLS), Transmission Electron Microscope (TEM) and UV-Vis spectrometer. Furthermore, the effect of photostability of of silica nanoparticles encapsulated fluorescein dye was measured under radiation of 200 W of Halogen lamp for 60 minutes. The silica nanoparticles encapsulated fluorescein dye was more stable compared to bare fluorescein dye after the exposure. In conclusion, the photostability of silica nanoparticles encapsulated fluorescein dye was improved compared to bare fluorescein dye, thus silica nanoparticles encapsulation successfully provides protection from the photobleaching and photodegradation of fluorescein dye.