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Amyloid beta peptides (A β 1-42) have been found to be associated with the cause of Alzheimer's disease (AD) and dementia. Currently, methods for detecting A β 1-42 are complicated and expensive. The present study is aimed at developing an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) to detect A β 1-42 by using a polyclonal antibody from alpaca, an application used in urine samples. The serum was collected from the alpaca after immunizing it with A β 1-42 at 500  μ g/injection 5 times. The ic-ELISA was developed and showed a half-maximal inhibitory concentration (IC 50 ) of 103.20 ng/ml. The limit of detection (LOD) was 0.39 ng/100  μ l. The cross-reactivity was tested with A β 1-40 and 8 synthesized peptides that had sequence similarities to parts of A β 1-42. The cross-reactivity of A β 1-40 and peptide 1 (DAEFRHDSGYE) was 55% and 69.4%, respectively. The ic-ELISA was applied to analyze A β 1-42 in the urine and precipitated protein urine samples. This method can be used for detecting a normal level of total soluble A β (approximately 1 ng in 5 mg of precipitated urine protein) and can be used for detecting the early stages of AD. It is considered to be an easy and inexpensive method for monitoring and diagnosing AD., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2020 Anurak Wongta et al.)

In Thailand detection of acaricide dicofol residues has been sporadically performed due to the limitation of analytical techniques. Conventional analytical methods for detecting dicofol residues most often use chromatographic-based techniques. Our ultimate aim is to develop an alternative method for rapidly analyzing dicofol residues in vegetables and fruit samples. Here we report the production of monoclonal antibodies specific to dicofol and its derivatives. Hapten-protein carriers were prepared by linking succinic anhydride to dichlorobenzhydrol (DCBH), which was then conjugated to bovine serum albumin (BSA) and oval albumin (OVA). DCBH-BSA conjugate was used as immunogen while DCBH-OVA conjugate was used as capture antigen for competitive inhibition assay. Female BALB/c mice were immunized with DCBH-BSA conjugate subcutaneously, and antibody (Ab) level was determined 2 weeks after the last immunization. Spleen cells producing high titer antibody were isolated and fused with myeloma cells of P3.X6.Ag8.653. After limiting dilutions, antibody produced by one clone had high affinity, which was found to be of IgG1 with κ light chain. Specificity and inhibition concentrations of the monoclonal antibody (MAb) were determined by competitive indirect ELISA with dicofol, and its 50% (IC(50)) was 0.28 μg/mL. Working ranges of the developed immunoassay were from 0.07 to 25 μg/mL. Hence, the prepared MAb will be able to be applied for immunoassay development for detecting dicofol residue in vegetables and fruits far below the maximum residue limit such that 5 g of fruits and berries can be detected below 0.1 mg/kg.

Salbutamol, one of the beta-agonists, is misused as a growth promoter in meat producing animals. In-house synthesized colloidal gold was conjugated with the polyclonal anti-salbutamol antibodies. A rapid immunochromatographic assay was developed in a competitive format. The salbutamol-BSA conjugate and goat anti-rabbit IgG were immobilized on a nitrocellulose membrane as test and control lines, respectively. The color intensity of a purple test line was inversely proportional to the amount of salbutamol presenting in the samples. The sensitivity was estimated to be about 80 ng/mL of salbutamol in PBS. The method can be useful as an "on-site" screening procedure for detection of salbutamol.