The Construction Of Structure-selective SERS Substrates For The Rapid Detection Of Penicilloic Acid In Penicillin

The penicillins are low-toxic and highly-efficient antibacterial drugs that have been widely used in clinical practices.However,the allergic reactions of penicillins are hazard to the penicillin-allergic patients and may lead to various fatal immune responses within a short time.Many studies have shown that penicillin itself cannot induce allergic reactions and the major allergen is penicilloic acid(PA)which is the by-product in the synthesis of penicillin or the degradation product of penicillin in storage through the opening of ?-lactam ring of penicillin.Thus,it is important to identify and detect the trace PA residue in penicillin for reducing the possibility of occurrence of allergic reactions.With the integration of high sensitivity,unique spectroscopic fingerprints and nondestructive data acquisition,surface-enhanced Raman scattering(SERS)technique has become one of the most widely pursued spectroscopic tools for the identification and detection of chemical and biological species.In this paper,the core-shell Au@Ag nanoparticles(NPs)colloids and two-dimensional molecularly imprinted monolayers(2D-MIM)substrates were fabricated for selectively detecting PA allergen.Meanwhile,the selective recognition mechanisms of the two SERS-active substrates were investigated for the detection of PA from penicillin matrix.The main results are summarized as follows:In chapter 1,we reported the structure-selective hot-spot Raman enhancement for direct identification and detection of penicilloic acid allergen in penicillin.First,the PA was prepared according to the previous literature and the reaction time as well as post-processing method was optimized.Then the core-shell Au@Ag NPs were obtained by seed growth method.The interactions of Au@Ag NPs with PA and penicillin were explored on the basis of molecular structures.It has demonstrated that Au@Ag NPs exhibit a structure-selective hot-spot Raman enhancement effect on PA.Moreover,we investigated the effect of Au@Ag NPs concentrations on the detection of target analytes.The result has shown that the Au@Ag NPs with high concentration can reduce the interference effect of penicillin for the detection of PA through increasing the binding sites on the surface of NPs.Finally,PA in aqueous solution and penicillin matrix were directly detected by using the core-shell Au@Ag NPs colloids,the limit of detection(LOD)was up to 0.1 ?M and 0.1%(g/g),respectively.In chapter 2,we reported a 2D-MIM strategy to fabricate the SERS substrate with high selectivity for detection of PA residue in penicillin.The Ag film was obtained through the silver mirror reaction in the presence of halide ions,and the effect of halide ions on the uniformity of formed Ag nanoparticles was studied in detail.At the initial stage of 2D-MIM preparation,complex of PA and p-phenylenediamine,as template,was first modified on the surface of Ag film,and then long-chain alkanethiols were used to form an ordered and oriented self-assembled monolayer around the template by backfilling.Finally,the 2D-MIM was obtained after removal of template through solvent extraction.Meanwhile,the fabrication of complex template was investigated by a series of experiments and the concentrations of alkanethiol and 4-aminothiophenol(SERS probe)were also optimized.In addition,we explored the selective recognition mechanism of 2D-MIM for PA detection from penicillin matrix in theory.Subsequently,PA in aqueous solution and penicillin matrix were indirectly detected by using the 2D-MIM substrate via the change of Raman intensity of SERS probe,the limit of detection(LOD)was up to 0.1 nM and 0.01%(g/g),respectively.Compared with non-imprinted monolayers and Au@Ag colloids,the LOD of PA for 2D-MIM substrate was about 3.9-and 10-folds that of non-imprinted monolayers substrate and Au@Ag colloids,respectively.The result reveals that 2D-MIM substrate possesses high selectivity for PA detection in penicillin matrix.The method will combine high selectivity of 2D-MIM and high sensitivity of SERS,to overcome these disadvantages such as higher mass transfer resistance of traditional molecularly imprinted ploymers(MIPs)SERS substrate and the lower selectivity of colloids SERS substrate.The new strategy reported herein may be potentially used in biological immunoassay,environment monitoring,pharmaceutical analysis and other relevant fields.