Synthesis of Galactoacrylamide and Study of Stimuli-Responsive Fluorescent Hierarchical Self-Assembly-Promoted Specific Interactions with Proteins

A new sugar based acrylamide, 6-N-acrylamido-D-galactopyranose (Gal-acryl) was synthesized from D-galactose in 6 steps. A solution of Gal-acryl at basic pH exhibited concentration dependent fractal type assembly formation upon solvent evaporation as revealed by the microscopic images. The fractal dimensions calculated point towards Diffusion Limited Aggregation mode of aggregate formation. The critical aggregation concentration (CAC) of Gal-acryl in water was found to be 49.3 mu M. The increase in fluorescence intensity accompanied by blue shift in emission maxima of coumarin 153 suggests increase in non-polar environment with Gal-acryl concentration. The I1/I3ratio of pyrene emission confirmed more non-polar microenvironment at acidic pH and vice versa at basic pH. Self-assembly allows Gal-acryl to exhibit specificity to lectin RCA120 as is demonstrated by fluorescence study further supported by turbidimetric assay. The fluorescence quenching studies with FITC-RCA120 afforded the Ka value as 6.34x105 M-1, which is much higher than Ka values observed for small galactose derivatives. The present study may help in designing different fractal like glycomaterials with potential applications in drug delivery, bio-sensing, tissue engineering, and as ligands to asialoglycoprotein receptors that are exclusively expressed by liver cells. The design and synthesis of a D-galactose based acrylamide, and study of its stimuli responsive hierarchical self-assembly into fractals is demonstrated. The micro polarity changes with pH and factors affecting fractal formation have been investigated. Self-assembly directed "glycocluster effect" and its effect on selective interaction with lectin RCA120 is demonstrated.image