Efficient Sequential Detection of Two Antibiotics Using a Fiber-Optic Surface Plasmon Resonance Sensor.

Antibiotic residues have become a worldwide public safety issue. It is vital to detect multiple antibiotics simultaneously using sensors. A new and efficient method is proposed for the combined detection of two antibiotics (enrofloxacin (Enro) and ciprofloxacin (Cip)) in milk using surface plasmon resonance (SPR) sensors. Based on the principle of immunosuppression, two antibiotic antigens (for Enro and Cip) were immobilized on an optical fiber surface with conjugates of bovine serum albumin using dopamine (DA) polymerization. Each single antigen was bound to its corresponding antibody to derive standard curves for Enro and Cip. The fiber-optic sensor's sensitivity was 2900 nm/RIU. Detection limits were calculated to be 1.20 ng/mL for Enro and 0.81 ng/mL for Cip. The actual system's recovery rate was obtained by testing Enro and Cip in milk samples; enrofloxacin's and ciprofloxacin's mean recoveries from the milk samples were 96.46-120.46% and 96.74-126.9%, respectively. In addition, several different regeneration solutions were tested to analyze the two target analytes' regeneration ability; NaOH and Gly-HCl solutions were found to have the best regeneration ability.

Oligomeric procyanidins inhibit insulin fibrillation by forming unstructured and off-pathway aggregates.

ß-sheet-rich amyloid fibril or aggregate accumulation has been implicated in a number of human diseases. Numerous studies demonstrate that natural polyphenols decrease the risk of degenerative diseases and inhibit in vitro amyloid formation. However, the molecular mechanism for the anti-amyloidogenesis of polyphenols is still unclear. Thus, this study investigates the effects of oligomeric procyanidins (OPCs), resveratrol, and trehalose on the amyloidogenicity of insulin via thioflavin-T (ThT) fluorescence, dynamic light scattering (DLS), circular dichroism (CD), and transmission electronic microscopy (TEM). The results demonstrate that the order of inhibitory effects on insulin amyloid fibrillation is OPCs > resveratrol > trehalose, suggesting that the polyphenolic structure is important for fibril deposition. OPCs show potent inhibitory effects at all stages of insulin fibrillation and redirect the insulin aggregation pathway via the formation of unstructured, off-pathway aggregates. These findings contribute to the development of novel anti-amyloidogenic products from naturally occurring materials.