Porous silicates for applications in smart water treatment systems and antimicrobial biomedical coatings

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Porous silicates, particularly ordered ones, may find novel and wide-ranging applications in the bioengineering arena in the near future. For instance, zeolites, a family of microporous, crystalline aluminosilicates, are promising candidate materials for the fabrication of next-generation water treatment systems that not only remove unwanted pollutants from waste water, but also provide real-time quality monitoring of water quality. In a different field, drug-loaded, ordered mesoporous silicate coatings may provide improvements to the current standard of treating implant-borne bacterial infections. This thesis contains two studies aimed at advancing scientific knowledge towards making these applications feasible. First, as a first step toward "smart" or inherently-selective water treatment sensors and systems, we studied the fundamental spectroscopic properties of a commonly-used zeolite material; these properties provide the foundation for determining what types of sensor systems in which the materials could be used. Here, we report the investigation of the influence of three synthetic parameters (aging time, crystallization temperature, and crystallization time) on the infrared absorbance spectra of siliceous and aluminosilicate zeolite sodalite (SOD). We found that these parameters do not appear to interfere in SOD's absorbance modes. Rather, they seem to play a role in determining whether SOD will be formed, especially for its siliceous form. Furthermore, the experimental data reported here was used to validate Density Functional Theory models, which allow the interrogation of these materials properties with a higher degree of precision when compared to experimental analyses. This work demonstrates that these materials could potentially be applied as a selective coating to sensor surfaces without worrying that their synthetic parameters might alter the sensor's response. Secondly, as a first step towards using mesoporous silica materials as coatings for implantable devices, we studied the adsorption of the three most prevalent serum proteins: albumin, fibrinogen, and immunoglobulin G. We characterized these processes using bicinchoninic acid (BCA) assays. We investigated the influence of three parameters (initial protein concentration, incubation time, and calcination time) on the non-competitive adsorption of these model proteins onto mesoporous silica films employing a 3 x 3 Latin-square experimental design, performed in triplicate. Our results suggest that mesoporous silica has a higher affinity to albumin when compared to fibrinogen and immunoglobulin G. Moreover, we observed that proteins tend to adsorb in higher amounts with increasing concentration. Neither calcination time nor incubation time had significant effects on the adsorption process. These studies represent advances in our current understanding of the synthetic mechanisms of SOD and of the biocompatibility of mesoporous silica films. Further studies will be aimed at further elucidating SOD's potential to be used in high-tech water filtration systems and mesoporous silica coatings as potential materials for next-generation antimicrobial coatings.