Search

Luminescently probed by luminol, the interaction behaviors of bovine serum albumin (BSA) with different antibiotics (macrolides, tetracyclines and sulfonamides) at picomolar levels were investigated using flow injection chemiluminescence (FI-CL) analysis. It was found that BSA and antibiotics formed complexes with the binding ratio of 1 : 1, with the binding constants K within the range of 103 to 105 L mol−1 generally following the order of macrolides < tetracyclines < sulfonamides. Results showed that the ester groups of –OOCC3H7 or –OOC(CH2)2COOC2H5 in macrolides led to increased K by factors of 3.1–42.8 times, –OH or –Cl in tetracyclines increased K by 1.1–1.3 times, and the additional –C(NH)NH2 in sulfonamides increased K about 1.3 times. The thermodynamic parameters demonstrated that the BSA–antibiotic binding process should be spontaneous mainly through hydrophobic interaction for macrolides, hydrogen bonding and van der Waals force for tetracyclines, and electrostatic interaction for sulfonamides. The further antibiotics to BSA molecular docking study revealed that the pocket at subdommain IIA of BSA should be the principle binding site for antibiotics, showing that the interaction parameters including K and ΔG agreed well with the results from the proposed FI-CL analysis. The interesting phenomenon that the log K had good linear correlation to molecular volume MV, molar refractivity MR, polarizability POL and partition coefficient log P of antibiotics was also observed.

Based on the linear enhancement of formaldehyde (FA) within 7.0 ∼ 1000 pmol l−1 on luminol—bovine serum albumin (BSA) chemiluminescence (CL) system, FA determination in air and beer samples using CL with flow injection (FI) was proposed. The detection limit was 2.5 pmol l−1 (3σ) and the relative standard deviations were less than 4.5% (n = 7). At a flow rate of 2.0 mL min−1, a whole analysis from sampling to washing only needed 32 s, offering a sample throughput of 112 h−1. This proposed method was successfully utilized to determine FA vapor pressure in liquid (121.8 ± 3.8 Pa), FA content in real air sample (8.93 ± 0.03 mg m−3), and FA levels in beer (199.5 ± 5.6 ∼ 225.2 ± 3.5 mg l−1), giving determination recoveries from 90.7% to 109.3%. The mechanism of BSA—FA interaction was also investigated, showing FA binding to BSA was a spontaneous process mainly through hydrogen bonding and van der Waals force by FI-CL, with binding constant K of 1.89 × 106 l mol−1 and the number of binding sites n of 0.86. Molecular docking analysis further revealed FA could enter into the pocket at subdomain IIA of BSA, with K of 1.71 × 105 l mol−1 and ΔG of -29.68 kJ mol−1.

A sensitive method for the determination of picogram level dibutyl phthalate (DBP) in wine by flow-injection chemiluminescence (FI–CL) analysis is presented for the first time, which was based on the quenching effect of DBP on the luminol–myoglobin (Mb) CL system. The decrement of CL intensity was linearly proportional to the logarithm of DBP concentration in the range of 0.1–100 pg mL −1 with the detection limit of 0.03 pg mL −1 (3 σ ). At a flow rate of 2.0 mL min −1 , a complete determination of DBP including sampling and washing could be accomplished in 0.5 min, giving the maximum sample throughput of 120 h −1 . The proposed method was successfully applied to the determination of DBP in wine, human serum and urine samples with the relative standard deviations (RSDs) of less than 3.0% ( n = 5). The molecule docking results showed that DBP interacted with the amino acid residues near the heme moiety of Mb. The possible CL mechanism of luminol–Mb–DBP reaction should be that the binding of Mb with DBP forming a 1:1 complex (binding constant K = 1.55 × 10 4 L mol −1 ) led to the conformational change of Mb and resulted in the quenching of CL intensity.

Human saliva quantitative monitoring of clarithromycin (CLA) by chemiluminescence (CL) with flow injection analysis was proposed for the first time, which was based on the quenching effect of CLA on luminol–bovine serum albumin (BSA) CL system with a linear range from 7.5 × 10−4 to 2.0 ng/ml. This proposed approach, offering a maximum sample throughput of 100 h−1, was successfully applied to the quantitative monitoring of CLA levels in human saliva during 24 h after a single oral dose of 250 mg intake, with recoveries of 95.2∼109.0 % and relative standard deviations lower than 6.5 % (N = 7). Results showed that CLA reached maximum concentration of 2.28 ± 0.02 μg/ml at approximately 3 h, and the total elimination ratio was 99.6 % in 24 h. The pharmacokinetic parameters including absorption rate constant (0.058 ± 0.006 h−1), elimination rate constant (0.149 ± 0.009 h−1) and elimination half-life time (4.66 ± 0.08 h) were obtained. A comparison of human saliva and urine monitoring was also given. The mechanism study of BSA–CLA interaction revealed the binding of CLA to BSA is an entropy driven and spontaneous process through hydrophobic interaction, with binding constant K BSA–CLA of 4.78 × 106 l/mol and the number of binding sites n of 0.82 by flow injection–chemiluminescence model. Molecular docking analysis further showed CLA might be in subdomain IIA of BSA, with K BSA–CLA of 6.82 × 105 l/mol and ΔG of −33.28 kJ/mol.

Human saliva quantitative monitoring of roxithromycin (ROX) at picomolar-level by flow injection (FI) chemiluminescence (CL) analysis is described for the first time, to our knowledge. Monitoring was based on the CL intensity from luminol-BSA reaction, which can be quenched in the presence of ROX, with the decreasing CL intensity linearly proportional to the logarithm of the ROX concentration, ranging from 0.6 to 1000 pmol·L-1. The detection limit of the proposed method for the determination of ROX was as low as 0.2 pmol·L-1 (3?), and the relative standard deviations were less than 4.0% (n = 7). A complete analytical process, including sampling and washing for ROX determination, conducted at a flow rate of 2.0 mL·min-1, was performed completely within 30 s, yielding a sample efficiency of 120 h-1. The proposed method was successfully applied to the determination of ROX in human saliva and serum samples with recoveries from 90.9% to 110.1%. The continuous monitoring of ROX in human saliva after oral intake showed that the total elimination ratio was 87.1% during 24 h, and the pharmacokinetic parameters were 0.97 ± 0.18 h-1 for the absorption rate constant Ka, 0.082 ± 0.010 h-1 for the elimination rate constant Ke, and 8.56 ± 1.11 h for the elimination half-life time t1/2. It was also found that ROX in human saliva and urine simultaneously reached the maximum at 2 h with the concentration correlate ratio of 0.97.

In this paper, the luminescence behavior of bovine serum albumin (BSA) and luminol was first studied by flow injection chemiluminescence (CL). It was found that the hyperchromic effect of luminol in the presence of BSA led to the acceleration of the electrons transferring rate of excited 3-aminophthalate, which greatly enhanced the CL intensity of luminol/dissolved oxygen reaction. The increments of CL intensity were proportional to the concentrations of BSA with a linear range from 0.01 to 7 nmol L−1. It was also found that azithromycin could inhibit the CL intensity of luminol/BSA reaction. The decrements of CL intensity were logarithm over the concentrations of azithromycin ranging from 0.1 to 700 ng mL−1. At a flow rate of 2.0 mL min−1, a complete analytical process, which included sampling and washing, could be performed within 30 s with relative standard deviations of less than 3.1%. This proposed method was successfully applied in assaying azithromycin in pharmaceutical and human serum samples with recoveries from 91.0 to 104.3%. The possible luminescence mechanism of luminol/BSA/azithromycin reaction was discussed in detail by CL, UV and fluorescence methods.