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Adsorption and Orientation of the Physiological Extracellular Peptide Glutathione Disulfide on Surface Functionalized Colloidal Alumina Particles
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