Bio-analytical Chemistry Investigations Based On The Enzyme Mimic Activity Of Gold Nanoparticles

Gold nanoparticles (AuNPs) are facile to synthesize, easy for surface decoration, having stable properties and good biological compatibilities. Owing to these characteristics, AuNPs are widely used in analytical chemistry fields. Up to now, detection methods based on the changes of the AuNPs'surface plasmon absorbance were developed ripely and realized the analysis of various analytes. Different from these methods, we took the advantages of the peroxidase mimic activity of the gold nano-materials and built a new strategy for Hg2+measurement, at the same time, accomplishing the discoloring of the dye Malachite Green in aqueous solutions. Details are listed herein:1. Based on the tuning of the peroxidase mimetic activity of AuNPs, we developed a new method for selective and sensitive detection for Hg2+. Normally, the citrate capped AuNPs just have relative low peroxidase like activity. When they are coexisted with Hg2+, the citrate ions can reduce Hg2+to form Hg0. Attributing to the high affinity between Hg0and gold, the as formed Hg0can easily attached to the surface of AuNPs, changing their surface properties. Theoretically, AuNPs'peroxidase activities are closely related to their surface status, and so the attached Hg0can undoubtedly influence the peroxidase mimic activity of AuNPs. Through the contrasts of the ability for the catalytic oxidation of the substrate of H2O2between AuNPs that were deposited with Hg0or not, we found that the attached Hg0can greatly enhance the peroxidase activity of AuNPs. Furthermore, within the range of Hg2+concentration from1.0×10-9M to6.0×10-7M, the absorbance of the oxidized H2O2substrate are linear correlated with the Hg2+concentration. The linear equation is y=0.019058+0.0017x, the linear correlation coefficient is0.9980and the detection limit is3.5×10-11M. By the means of a serials characterization, we also accomplished the mechanism study of the reactions.2. We developed a simple and facile way for the incorporation of nanoparticles. Accompanied with the gelation of hot agar solutions, the dispersed nanoparticles in solutions can finally embedded in the matrix of agar gel and formed the new nanoparticle-agar composite materials. Through this way, we confirmed that the monodispersity, stability, unique optical and catalytic properties were obtained fairly well. Moreover, owing to the good corporation ability of the agar gel matrix, the formed composite materials are superior stable to the rigorous outer conditions, including acidic, basic, saliferous and various organic solvents environments. These make the composite materials more adoptable in many complex practical applications. Based on that, we exploited a new Hg2+sensor which enables visual observation used the AuNPs-agar gel composite materials. Additionally, we further developed a new kind of agar membrane supported nanoparticle composite materials. We observed the antibacterial ability of the agar gel-and agar membrane-nanoparticles composite materials, and the results showed that these two materials were all antimicrobial, showing the potential to develop new kinds of antibacterial materials and antimicrobial medicaments.3. Au clusters is a kind of Au materials with specialty, because of their super fluorescence properties. Upon the observation of the interactions between H2O2and Au clusters, we found that trace amount of H2O2can result in the decrease of the fluorescence intensity of Au clusters. Based on this phenomenon, we developed a method to detect the uric concentration in blood serum. Under the catalysis of the uric enzyme, uric can be oxidized and produce stoichiometric H2O2, leading to the decrease of the fluorescence intensity of Au clusters, realizing the indirect detection for uric. The linear equation is y=-0.18783+0.24706x, the linear correlation coefficient is0.9908and the detection limit is7μM. Although the detection limit is not so low, this method can afford the measurement of uric in serum. By the contrast of the obtained results between our method and local hospital detection, this presented method is confirmed to be reliable.4. We applied the BSA-Au clusters to the discoloring of the dye Malachite Green in aqueous solutions. The peroxidase mimetic activity of Au clusters makes them be able to catalyze the decomposition of H2O2and produce abundant of·OH radicals.·OH radicals are extensive oxidants that can lead to the degradation of organic dyes. In our experiments, BSA-Au clusters exhibited excellent catalytic ability to degrade Malachite Green. When the H2O2concentration was1M, the pH value of the solution is3.78,5mg/ml BSA-Au clusters can degrade93%of Malachite Green within25min. If the reaction time was prolonged to1h,98%of the dye can be decomposed. Additionally, through the flocculation and the final sedimentation of BSA, BSA can help cooperatively to remove the resident pollutants from solutions. Consequentially, Malachite Green can be disappeared in water thoroughly.Generally, in this paper, we proposed conception to tune the peroxidase mimic activity of gold nanomaterials. Based on that, we realized the high selective and sensitive detection for mercuric ions in solution. This new strategy is an advantageous supplement to the applications of the nanomaterials based peroxidase mimics in optical analytical chemistry and is helpful to clarify the mechanisms of the forming of the peroxidase like activity of nanomaterials.The way we developed to incorporate nanoparticles into agar matrix is simple, facile and effective. This way is universal for many thermal-stable nanoparticles to form composite materials.Because that H2O2is a kind of the non hazardous oxidants, we suggested that exploit peroxidase mimic nanoparticles to degrade small molecule organic pollutants will be prospective. Concluded from our experiments, the combination of the catalytic activity with the facility of the synthesis, surface decoration, and separation of nanoparticles will be promising to exploit high efficient and reusable nanomaterials to deal with dye waste water.In all, we have extended the applications of the peroxidase mimetic gold nanoparticles and clusters in analytical chemistry and environmental chemistry. These methods proposed herein are all simple, quick, visual and effective. We hope these will be benefit for the researches of the enzyme mimic materials.