| The presence of antibiotic residues in food products, drinking water, and environment constitutes a worldwide concern because of its serious health consequences, including the emergence of antibiotic-resistant bacterial strains, disturbance or disruption of the normal ecological equilibrium and increasing instances of allergic reactions. Penicillins and otherβ-lactam antibiotics are the most frequently used antibiotics and have long been widely used for treating various bacterial infections in human, livestock, poultry, and aquaculture. Consequently, detection of the residues of these antibiotics in food and environment is vital for protecting the public health. Current methods applied for the detection of these drugs mainly include traditional microbial inhibitor tests, HPLC/MS methods, and some commercial screening tests based on inhibition of bacterial growth, inhibition of D-carboxypeptidase, or the receptor protein-antibiotic binding. Each of these methods has its particular limitation:the microbial inhibitor tests need a lengthy incubation step and are thus very time consuming, the HPLC/MS methods require expensive instruments and extensive sample pretreatment, and most commercial screening tests can provide only semi-quantitative results. The aim of this thesis work was to develop new alternative methods for rapid, sensitive, slective, and simple detection ofβ-lactam antibiotics. The main contents include: 1. A review on detection technologies for antibiotic residues.2. The development of an amperometric penicillin biosensor based on co-immobilization of multi-walled carbon nanotubes (MWCNTs), hematein, andβ-lactamase on glassy carbon electrode using a layer-by-layer assembly (LbL) technique. Under catalysis of the immobilized enzyme, penicillin was hydrolyzed, decreasing the local pH. The pH change was monitored amperometrically with hematein as a pH-sensitive redox probe. MWCNTs were used as an electron transfer enhancer as well as an efficient immobilization matrix for the sensitivity enhancement. The effects of immobilization procedure, working potential, enzyme quantity, buffer concentration, and sample matrix on the biosensor performance were investigated. The biosensor offered a minimum detection limit of 50 nM (19μg/L) for penicillin V, lower than those of the conventional pH change-based biosensors by more than two orders of magnitude. The detection range was up to 2.7 mM. The electrode-to-electrode variation of the response sensitivity was 7.0% RSD (relative standard deviation).3. The development of an amperometric penicillin biosensor based on co-immobilization of penicillinase and MWCNTs on gold electrode via para-benzoquinone electroreduction-induced deposition of chitosan. The effects of deposition time, applied potential, enzyme quantity, and concentration of buffer solution on the biosensor performance were investigated. The detection range was 9.8 nM-2.7 mM for pencillin V.4. The development of an amperometric penicillin biosensor based on co-immobilization of MWCNTs, hematein, andβ-lactamase on screen-sprinted electrode. The stepwise assembly of the biosensor was characterized by electrochemical impedance spectroscopy and cyclic voltammetry. Under the optimal conditions, the detection range was 57 nM-48μM for ampicillin sodium.5. The development of a flow injection chemiluminescence (CL) method for detection of ampicillin sodium based on the finding that the CL arising from oxidation of luminal with potassium periodate in strong ankaline solution was greatly enhanced by the combined effects of N, N-dimethyl formamide (DMF) and acetonitrile. The linear detection range was 0.1-4.0μg.L-1 with a detection limit of 1 ng.L-1. The relative standard deviation (RSD) was 2.3%at 1.0μg.L-1.
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