Pharmaceutical Research

, Volume 20, Issue 3, pp 508–514

Characterization of Particle-Interactions by Atomic Force Microscopy: Effect of Contact Area

  • Jennifer C. Hooton
  • Caroline S. German
  • Stephanie Allen
  • Martyn C. Davies
  • Clive J. Roberts
  • Saul J. B. Tendler
  • Philip M. Williams
Article

DOI: 10.1023/A:1022684911383

Cite this article as:
Hooton, J.C., German, C.S., Allen, S. et al. Pharm Res (2003) 20: 508. doi:10.1023/A:1022684911383

Abstract

Purpose. The purpose of this work was to compare adhesion forces, contact area, and work of adhesion of salbutamol sulphate particles produced using micronization and a supercritical fluid technique (solution-enhanced dispersion by supercritical fluids - SEDS™) using atomic force microscopy (AFM).

Methods. Adhesion forces of individual particles of micronized and SEDS™ salbutamol against a highly orientated pyrolytic graphite surface were acquired in a liquid environment consistent with that of a pressurized metered dose inhaler. The forces were then related to contact area and work of adhesion.

Results. The raw adhesion force data for the micronized and SEDS™ material were 14.1 nN (SD 2.5 nN) and 4.2 nN (SD 0.8 nN), respectively. After correction for contact area, the forces per unit area were 13 mN/μm2 (SD 2.3 mN/μm2) and 3 mN/μm2 (SD 0.6 mN/μm2). The average work of adhesion was calculated using the Johnson-Kendall-Roberts theory and was found to be 19 mJm−2 (SD 3.4 mJm−2) for the micronized particle and 4 mJm−2 (SD 0.8 mJm−2) for the SEDS™ particle.

Conclusions. It is possible to produce a three-dimensional representation of the contact area involved in the interaction and make quantitative comparisons between different particles. There was a lower force per unit area and work of adhesion observed for the SEDS™ material, possibly because of its lower surface free energy.

SEDS micronized AFM contact area work of adhesion 

Copyright information

© Plenum Publishing Corporation 2003

Authors and Affiliations

  • Jennifer C. Hooton
    • 1
  • Caroline S. German
    • 2
  • Stephanie Allen
    • 1
  • Martyn C. Davies
    • 1
  • Clive J. Roberts
    • 1
  • Saul J. B. Tendler
    • 1
  • Philip M. Williams
    • 1
  1. 1.Laboratory of Biophysics and Surface Analysis, School of Pharmaceutical SciencesUniversity of NottinghamUnited Kingdom
  2. 2.Bradford Particle Design LtdBradfordUnited Kingdom