AFM Study of Morphology of Ethanol Induced Gelatin Coacervation

ABSTRACT

AFM studies have been carried out on coacervating 1% (w/v) aqueous alkali processed gelatin (Type-B) solutions titrated with ethanol close to its iso-electric pH = 5.01 (pI = 4.9). Turbidity measurements performed at 450 nm clearly established the transition points in terms of the percentage of volume of alcohol added relative to that of the total volume corresponding to the first occurrence of turbidity (Vt = 47±2%v/v) and a point of turbidity maximum (). Addition of more alcohol drove the system towards precipitation. The values of Vt and Vp characterized the initiation of intramolecular collapse and intermolecular aggregate formation of the charge neutralized gelatin molecules, and the subsequent micro coacervate droplet formation. The gelatin molecules in the solution were observed to undergo a series of micro-structural transformations as seen by AFM until the coacervates phase was reached. At a critical ethanol concentration of fractal clusters of aggregated polypeptide molecules having fractal dimension were observed.

Keywords:

• atomic force microscopy (AFM)
• gelatin coacervates
• fractal aggregates
• surface morphology
• self-assembly

Acknowledgments

BM is thankful to the Council of Scientific and Industrial Research, India for a Junior Research Fellowship. This work was supported by Department of Science and Technology, Government of India research grant, and DRS grant of University Grants Commission, India.