Preparation And Applications Of Inorganic Boronate Affinity Materials

Many biomolecules of research or clinical importance,such as catecholamines,some saccharides,ribonucleotides,glycolipids,glycopeptides and glycoproteins,possess at least one cis-diol structure.Boronate affinity chromatography,relying on the specific,reversible esterification reaction of boronic acid ligands with the 1,2 or 1,3 cis-diol moieties of the target molecules,has become a promising tool for the enrichment or interaction research of the target biomolecules,and has drawn increasing attention in recent years.The properties of boronate affinity depend mainly on boronic acid ligands,and the supporting material also has significant effects on the binding properties.In addition to the specific cis-diol interaction,several secondary interactions,i.e.hydrophobic,have been observed on boronate affinity materials,having impact on the selectivity.Almost all ligands used in boronate affinity materials are aromatic or heterocyclic boronic acids.These organic boronate ligands to some extend can arise to hydrophobic interaction.Therefore,the development of boronate affinity materials with high selectivity and high affinity is still desirable in the future.In this dissertation some novel boronate affinity materials were prepared by utilizing inorganic boric acid as ligands.The mechanism was discussed and the applications were explored.Main points of this work are listed as following:1.A unique in-needle inorganic monolithic column was prepared through sol-gel technology by using tetrabutyl orthotitanate and tetraethoxysilane as the co-precursors.The monolith was in situ synthesized in a stainless steel needle,and exhibited good selectivity towards different cis-diol containing compounds.Recovery of greater than 90%was achieved for in-needle extraction of catechol under neutral conditions.Owing to the hydrophilic property of the monolith,the procedure of enrichment can be performed in aqueous solution,avoiding the use of organic solvents.The monolithic in-needle extraction device is robust and convenient in operation.Elution of the analyte from the needle requires only microliter-scale solvent,and thus the in-needle extraction device is appropriate for pretreatment of small-volume samples.2.Titania was modified with boric acid,and the resulting material was characterized by scanning electron microscopy,Fourier transform infrared spectroscopy,X-ray powder diffraction and X-ray photoelectron spectrometry,indicating that inorganic boric acid was covalently incorporated into amorphous titania.The new material,in contrast to conventional boronate affinity materials containing boronic acid ligands,bears boric acid groups.It is shown to exhibit high specificity for cis-diol containing compounds including glycoproteins.Because of high hydrophilicity of the supporting material and the lack of aromatic boronic acid ligands,nonspecific binding due to hydrophobic interaction can be minimized.The material exhibits good selectivity and capacities towards glycoproteins,and the binding capacities for ribonuclease B,horse radish peroxidase and ovalbumin typically are 9.3,26.0 and 53.0 mg/g,respectively.The method was successfully applied to the selective enrichment of ovalbumin from egg white.3.A coated capillary was fabricated by coating the inner surface of capillary with boric acid-modified titania,and the covalently coated capillary was applied to the separation of protein glycoforms.In comparison with the naked capillary for the zone electrophoresis separation of ovalbumin,ribonuclease B and horse radish peroxidase,the coated capillary has improved performance for the separation of glycoforms.4.Boronate affinity pollens were prepared by modifying the pollen surface with boric acid-functionalized titania.Glucose oxidase and horse radish peroxidase were immobilized onto the pollens under mild conditions.A visualized method for the detection of glucose was developed on the basis of the coupled reactions catalyzed by the immobilized enzymes,and was applied to the detection of glucose in urine samples and serum.The method is fast,accurate,and convenient in operation.The result can be observed by naked eyes without the need of instruments.This method has potential to become a quick,popular way for the detection of glucose.