Studies towards the preparation of functionalized cellulose microspheres with affinities towards negatively charged biomembranes

2021-7
Demirel, Kaan
Cellulose microspheres (CMs), generally with diameters in the 10-1000 µm range, have been used as stationary phases in chromatography, substrates for ion exchange applications, supports for protein immobilization and solid-phase synthesis, and drug loading and release materials. Furthermore, cellulose and CMs are biocompatible and have been used in many biomedical applications as varied as the dressing of wounds and blood filtration. Targeting of bacterial cells can be achieved using antibodies, antibody fragments, peptides, polycationic dendrimers, antibiotics such as vancomycin, and certain metal complexes. Zinc (II) bisdipicolylamine (Zn2BDPA) complexes are capable of selectively binding to negatively charged phosphate amphiphiles displayed by bacterial cells. Blood is normally sterile and the presence of bacteria in blood is a condition known as bacteremia. Bacteremia can be caused by burns, injuries, local infections, surgical procedures, and the use of catheters or needles. If undetected and untreated, the immune response to bacteremia can result in sepsis, septic shock, and multiple organvi failure. Septic shock and multiple organ failure as a result of hospital-acquired bacteremia is a leading cause of death in intensive care units. This study aimed to develop Zn2BDPA-derivatized CMs as selective sorbents capable of binding to negatively charged liposomes and bacterial cells, with an ultimate goal of obtaining functional materials for the treatment of bacteremia through extracorporeal whole blood filtration. To this end, the preparation of CMs through the thermal regeneration of cellulose from water-in-oil emulsions of viscose has been investigated and the effect of various factors on particle size have been determined. Underivatized (native) CMs were then activated to display aldehyde, amino, carboxylic acid, cyano, and epoxy functionalities. Amine and carboxylic acid bearing BDPA ligands were then coupled with some of these activated CMs. Formation of BDPA-CM conjugates was confirmed using several analytical techniques. Zn2BDPA complex functionalized CMs were then shown to bind to negatively charged fluorescent liposomes and green fluorescent protein (GFP) expressing bacterial cells through fluorescence spectroscopic measurements and/or fluorescence microscopy. Further development of these materials is likely to lead to effective sorbents for bacterial cells which would have applications in the diagnosis and treatment of bacteremia and in the isolation and preconcentration of bacterial cells from a variety of liquid samples.

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Citation Formats
K. Demirel, “Studies towards the preparation of functionalized cellulose microspheres with affinities towards negatively charged biomembranes,” M.S. - Master of Science, Middle East Technical University, 2021.