Interfacial phenomena are important in the following biological and pharmaceutical applications:
Biological and
pharmaceutical applications
Interfacial
phenomena are important in the following biological and pharmaceutical
applications:
·
Physical stability
of biphasic dosage forms, such as suspensions and
emulsions, are affected by the stabilization of the solid–liquid and the
liquid–liquid interfaces, respectively.
·
Gas exchange in the
lung:
Biological surfactants in the lung lower the
surface tension of the alveolar membrane. Thus, alveoli can expand easily with
inspiration and do not collapse at the end of expiration. If there is little or
no surfactant in the lungs to assist these processes, the alveoli collapse,
leading to respiratory distress syndrome.
·
Preventing
absorption after oral overdose and poisoning: Activated charcoal, magnesium oxide, and tannic acid are administered to
reduce the absorption of an oral overdose of many drugs such as colchicines,
phenytoin, aspirin, and chlorphenamine.
·
Hemoperfusion: Many cases of
severe drug overdoses can be treated by
direct perfusion of the blood over charcoal granules. Although activated
charcoal granules are very effective in adsorbing many toxic materials, they
are not safe to use because they tend to embolize par-ticles and remove blood
platelets. Charcoal-induced embolism was reduced by microencapsulation of
activated charcoal granules in bio-compatible membranes, such as acrylic
hydrogels.
·
Adsorption in drug
formulation:
Some drugs tend to adsorb onto solid
surfaces, which may reduce the rate and/or extent of drug release from the
dosage form. This is exemplified by ionic interactions of ion-izable drugs with
ion-exchange resins. This phenomenon is used to create sustained- or
extended-release dosage forms and in the use of resins for oral overdose.
·
Adsorption to
packaging components: Adsorption of medicaments onto the container and closure material can reduce the potency of
the drug product.
·
Improving drug
dissolution:
The dissolution rate of poorly soluble drugs
can be improved by adsorption of a small amount of surfactant on the surface of
drug particles.
·
Protein adsorption: Adsorption of
proteins onto surfaces is a fast process
and depends on concentration, charge, temperature, and hydrophobicity.
Adsorption of protein on hydrophobic surfaces can catalyze its unfolding and
aggregation, leading to physical instability in drug product formulation. Thus,
containers and closures for the storage and administration of protein
therapeutics, including intrave-nous infusion sets, need to be carefully
evaluated for protein—surface interaction.
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