Search

This study determined the extent of heavy metal contamination of local fruit in Rayong, Thailand, an area where an industrial base is adjacent to agricultural areas. Dietary exposure to agricultural products grown in contaminated areas can cause multiple adverse effects to the human body. In order to avoid such undesirable effects, concentrations of heavy metals [arsenic (As), cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn)] were investigated in popular tropical fruits from three districts of Rayong, namely Wang Chan, Klang and Mueang. The levels of heavy metals were determined by inductively coupled plasma-mass spectrometry (ICP-MS) and cold vapor-atomic absorption spectrometry (CV-AAS). Levels of the six heavy metals in sampled fruits (durian, jackfruit, pineapple, rambutan, long kong, and mangosteen) were in the range of 0.0004-6.7095 mg/kg; 16.7% of fruit samples exceeded maximum permissible limits of Pb. Based on health risk assessments, values of estimated daily intake (EDI) were less than those of maximum tolerable daily intake. However, for non-carcinogenic risks, high hazard index (HI) values were found in some markets while for carcinogenic risks (CRs), CR values of three fruits (durian, jackfruit, and mangosteen) exceeded acceptable levels. Therefore, long-term fruit consumption could impact health of local consumers. These results provided insight into the need for regular monitoring of heavy metal concentrations in potentially contaminated fruits and for prevention of its potential effects.

Abstract Cardiac troponin I (cTnI) is a specific cardiac biomarker for diagnosis of acute myocardial infarction (AMI). A sensitive and simple point-of-care test (POCT) is still required for early detection of AMI. To address this need, we developed a dip strip assay based on sandwich immunoassay coupled with a silver enhancement system. Pre-incubation and silver enhancement were introduced to the dip strip to increase sensitivity. Due to the catalytic reaction of the silver enhancement solution, the red color of AuNPs changed to dark brown as silver ions precipitated and enlarged the AuNPs. The obtained results were easily seen by the naked eye. For quantitative analysis, the color intensity of the results was analyzed using a smartphone with RGB color picker application. The effects of operating parameters (volume of AuNP-Ab conjugate, volume of sample, incubation time, and analysis time) were investigated and optimized. Under optimal conditions, the limit of detection (LOD) by the naked eye was 0.5 ng/mL. The LOD with silver enhancement was 50-fold lower than without. For quantitative analysis using the smartphone, linearity of detection was observed through the range of 0.5–50 ng/mL (R2 = 0.9952) and the LOD was 0.12 ng/mL. The developed method was successfully applied to detection of cTnI in serum samples, achieving analytical recoveries and %RSD in the ranges of 96.10–119.17% and 2.91–5.13%, respectively. Additionally, this developed assay was not cross reactive with the potentially interfering serum proteins. These results showed the great potential of this dip strip assay as an alternative POCT for detection of serum cTnI.

A colorimetric probe based on a hybrid sensing system of gold nanoparticles (AuNPs), silver nanoparticles (AgNPs), and thymine (Thy) was developed for easy and rapid detection of copper (II) ions (Cu2+) in solution. The underlying principle of this probe was the Cu2+-triggered aggregation of the nanoparticle components. Color change of the sensing solution (from red to purple) was clearly observed with naked eyes. The experimental parameters, including pH and concentration of tris buffer, thymine concentration and AgNP dilution ratios, were investigated and optimized. Once optimized, the limits of detection were found to be 1, 0.09 and 0.03 ppm for naked eyes, smartphone application and UV-vis spectrophotometer, respectively. Furthermore, determination of Cu2+ was accomplished within 15 min under ambient conditions. For quantitative analysis, the linearity of detection was observed through ranges of 0.09–0.5 and 0.03–0.5 ppm using smartphone application and UV-vis spectrophotometer, respectively, conforming to the World Health Organization guideline for detection of copper at concentrations < 2 ppm in water. This developed hybrid colorimetric probe exhibited preferential selectivity toward Cu2+, even when assessed in the presence of other metal ions (Al3+, Ca2+, Pb2+, Mn2+, Mg2+, Zn2+, Fe3+, Ni2+, Co2+, Hg2+ and Cd2+). The developed procedure was also successfully applied to quantification of Cu2+ in real water samples. The recovery and relative standard deviation (RSD) values from real water sample analysis were in the ranges of 70.14–103.59 and 3.21–17.63%, respectively. Our findings demonstrated a successful development and implementation of the Thy-AuNP-AgNP hybrid sensing system for rapid, simple and portable Cu2+ detection in water samples using a spectrophotometer or a smartphone-based device.