Interaction Force Profiles between Cryptosporidium parvum Oocysts and Silica Surfaces

The interaction force profile between single Cryptosporidium parvum oocysts and silica particles was measured in aqueous solutions using an atomic force microscope. The oocysts were immobilized during the measurements by entrapment in Millipore polycarbonate membranes with a 3 μm pore size. Experime...

Full description

Saved in:
Bibliographic Details
Published in:Environmental science & technology 2005-12, Vol.39 (24), p.9574-9582
Main Authors: Byrd, T. L, Walz, J. Y
Format: Article
Language:English
Subjects:
Animals
Applied sciences
Aqueous solutions
Bacteria
Calcium Chloride - chemistry
Carbohydrates - chemistry
Cryptosporidium parvum
Cryptosporidium parvum - metabolism
Electrolytes
Environmental science
Exact sciences and technology
Experiments
Groundwaters
Kinetics
Microscopes
Microscopy
Microscopy, Atomic Force
Natural water pollution
Oocysts - chemistry
Oocysts - metabolism
Osmolar Concentration
Pollution
Proteins - chemistry
Protozoa
Silica
Silicon Dioxide - chemistry
Sodium Chloride - chemistry
Surface Properties
Water Purification - methods
Water treatment and pollution
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The interaction force profile between single Cryptosporidium parvum oocysts and silica particles was measured in aqueous solutions using an atomic force microscope. The oocysts were immobilized during the measurements by entrapment in Millipore polycarbonate membranes with a 3 μm pore size. Experiments were performed in both NaCl and CaCl2 solutions at ionic strengths ranging from 1 to 100 mM. For both electrolytes the decay length of the repulsive force profile, obtained via the slope of a plot of the logarithm of interaction force versus separation, was found to be essentially independent of the ionic strength and always much larger than the theoretical Debye length of the system. In addition, the magnitude of the force was found to be essentially the same for both electrolytes, suggesting that the long-range repulsive forces are primarily steric in nature. Fitting the force to an expression for the steric repulsive force between two grafted brush layers yields a layer thickness of approximately 115 nm. These results support the idea that the oocysts are covered by a relatively thick layer of uncharged (or weakly charged) carbohydrates, possibly mixed with a thinner layer of charged protein.
ISSN:0013-936X
1520-5851
DOI:10.1021/es051231e