Nucleation at surfaces: The importance of interfacial energy

The nucleation and growth of stone-forming minerals on the surfaces of othe r crystalline phases, cellular material, and immobilized macromolecules mus t be important in the formation of stones in the urinary tract. The nucleat ion and growth of calcium oxalate monohydrate (COM) crystals were studied u sing the constant composition kinetics technique, in solution supersaturate d with respect to COM (sigma(COM), = 1.44). The solid phases during the rea ction were examined by x-ray diffraction, scanning electron microscopy, and diffuse reflectance Fourier transform infrared spectroscopy. Human serum a lbumin was found to nucleate COM crystals when immobilized on hydroxyapatit e (HAP) surfaces. The induction period for nucleation of COM on HAP surface s preadsorbed with albumin significantly decreased to about 65 min from abo ut 230 min for pure HAP particles. The initial growth rate of COM on pure H AP particles, R-in approximate to 0.56 X 10(-7) mol/min per m(2), was slowe r than that for HAP surfaces preadsorbed with albumin, 2.14 X 10-7 mol/min per m2. The surface properties were characterized using contact angle measu rements by sessile drop and thin layer wicking. The thermodynamic results s uggested that surfaces with high Lewis base parameter values (gamma(-)) and Low interfacial tension with water (gamma(SL),,) are more effective in the nucleation and growth of crystal phases.