Drugs and the pharmaceutical sciences

270 Meltzer
Extents of adsorption differ same organism / different Ros
polyamide vs. cellulose acetate
Bound radioactivity (CPM)
(thousands)
50
40
30
20
10
0
the attachments. This latter quality is a result, if not a cause, of hydrophobic adsorptions,
as will be discussed. From the foregoing, it seems there is a degree of commonality
between biofilm formation and protein adsorption.
The adsorption of organisms from their suspensions onto solid surfaces would
involve the same forces of attraction and repulsion that regulate the adsorptive joining of
one colloidal particle’s surface to that of another. The process involving organisms would
manifest itself in their adsorptive retention to the filter surfaces.
Marshall (1992) points out that bacteria, as also particles in general, are kept from
contact with surfaces by electrostatic forces. This includes the surfaces of other
organisms. The repulsive forces involved are effective at long range, and prevail over the
weaker attractive forces that are simultaneously present. As will be described in the
forthcoming discussion of the electric double layer, the repulsions are attenuated by
higher electrolyte concentrations. The attractive forces, albeit weaker, can then assert
their influence. The adsorptive interactions that follow would result in the formation of a
biofilm.
Fuoss Effect
0 40 80 120 160 200 240 280
Time (seconds)
FIGURE 5 Upper
line: Micobacterium
adsorbed to polyamide
RO membrane.
Lower line: Micobacterium
adsorbed to
cellulose acetate RO
membrane. Source:
From Ridgway
et al., 1984a;
In suggesting a similarity between protein adsorptions to polymeric filter surfaces and
organism attachments to the same type surfaces, it is speculated that the term
“adsorption” as used in the phrase “protein adsorption” includes a more varied
expression of the same mechanisms that fixedly bond other surfaces to one another. The
bonding to activated carbon of organic molecular substances, whether in the form of
vapors, liquids or particles, as utilized in gas masks or in water purification contexts, is a
classical example of adsorption. As will be seen, the ionic strengths of the aqueous
solutions from which proteins may be adsorbed also govern the adsorptive bonding of the
organics to the surfaces of the activated carbon particles. In this instance as well, there is
an apparent similarity in cause and effect. It is speculated that the adsorption of organic
compounds including proteins to activated carbon surfaces is part of a like operation.
The positive effect of ionic strengths on adsorptive sequestrations is forthcoming
from the field of water treatment and involves the adsorption of organic substances by