Adsorption and Orientation of the Physiological Extracellular
Peptide Glutathione Disulfide on Surface Functionalized Colloidal
Alumina Particles
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Abstract
Understanding the
interrelation between surface chemistry of colloidal
particles and surface adsorption of biomolecules is a crucial prerequisite
for the design of materials for biotechnological and nanomedical applications.
Here, we elucidate how tailoring the surface chemistry of colloidal
alumina particles (<i>d</i><sub>50</sub> = 180 nm) with
amino (−NH<sub>2</sub>), carboxylate (−COOH), phosphate
(−PO<sub>3</sub>H<sub>2</sub>) or sulfonate (−SO<sub>3</sub>H) groups affects adsorption and orientation of the model
peptide glutathione disulfide (GSSG). GSSG adsorbed on native, −NH<sub>2</sub>-functionalized, and −SO<sub>3</sub>H-functionalized
alumina but not on −COOH- and −PO<sub>3</sub>H<sub>2</sub>-functionalized particles. When adsorption occurred, the process
was rapid (≤5 min), reversible by application of salts, and
followed a Langmuir adsorption isotherm dependent on the particle
surface functionalization and ζ potential. The orientation of
particle bound GSSG was assessed by the release of glutathione after
reducing the GSSG disulfide bond and by ζ potential measurements.
GSSG is likely to bind via the carboxylate groups of one of its two
glutathionyl (GS) moieties onto native and −NH<sub>2</sub>-modified
alumina, whereas GSSG is suggested to bind to −SO<sub>3</sub>H-modified alumina via the primary amino groups of both GS moieties.
Thus, GSSG adsorption and orientation can be tailored by varying the
molecular composition of the particle surface, demonstrating a step
toward guiding interactions of biomolecules with colloidal particles