Preparation and characterization of biopolymeric microparticles for surface-enhanced Raman spectroscopy and fluorescent microscopy imaging

Abstract

Spectroscopy is an interesting research field because of its wide applications areas. Therefore, in my doctoral thesis, I was centering on the preparation and laser spectroscopic characterization of polymeric microparticles for different applications. Firstly, I prepared microparticles and estimated their optimal preparation conditions, then developed them to fabricate fluorescent microparticles to be used in imaging. Secondly, I obtained a new composite of polymer microparticles covered with gold nanoparticles to be used in surface-enhanced Raman spectroscopic applications to detect certain biomolecules. The first step of my doctoral research work was to study the reaction kinetics of DEGDMA monomer in different solvents upon gamma irradiation with different doses and to determine the dose dependence of the degree of conversion with Raman spectroscopy and mass difference measurements. Both methods showed good agreement in the DC, therefore, the Raman method was found to be an excellent method of choice to determine the conversion rate of the polymer by a non-contact, non-destructive and, in terms of realization, simple manner, having the potential for real-time remote monitoring in the irradiation chamber. The results were fitted using the Avrami equation, and the observed variations in reaction rate were attributed to the fact that the DEGDMA polymerization process behaves differently in alcohols and other solvents, as determined by their solubility values. In the second phase, I synthesized polymeric microparticles of DEGDMA monomer with ethyl propionate solvent by gamma radiation-initiated precipitation polymerization firstly, then FITC dye was incorporated into the polymer matrix to form luminescent FITC/DEGDMA microparticles. The morphology, size, bonding configuration, and emission properties of the microparticles were investigated by using SEM, Raman, PL spectroscopy, and LSFM, respectively. It was found that the structure of the FITC was preserved after the irradiation and the obtained microparticles have good emission properties. In the last part of my study, I have developed the method to synthesize SERS enhanced substrate by attaching gold nanoparticles to polymeric microparticles prepared by gamma radiation-initiated polymerization. Firstly, I fabricated poly(DEGDMA)/AuNPs composite and investigated their enhancement efficiency as a SERS substrate using R6G the common fluorescent probe dye. Secondly, the practical applications of proposed SERS substrates were tested by DNA strand-specific to the parasite Giardia lamblia (the β-giardin gene).