Controlling Mixed-Protein Adsorption Layers on Colloidal
Alumina Particles by Tailoring Carboxyl and Hydroxyl Surface Group
Densities
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Abstract
We
show that different ratios of bovine serum albumin (BSA) and
lysozyme (LSZ) can be achieved in a mixed protein adsorption layer
by tailoring the amounts of carboxyl (−COOH) and aluminum hydroxyl
(AlOH) groups on colloidal alumina particles (<i>d</i><sub>50</sub> ≈ 180 nm). The particles are surface-functionalized
with −COOH groups, and the resultant surface chemistry, including
the remaining AlOH groups, is characterized and quantified using elemental
analysis, ζ potential measurements, acid–base titration,
IR spectroscopy, electron microscopy, nitrogen adsorption, and dynamic
light scattering. BSA and LSZ are subsequently added to the particle
suspensions, and protein adsorption is monitored by in situ ζ
potential measurements while being quantified by UV spectroscopy and
gel electrophoresis. A comparison of single-component and sequential
protein adsorption reveals that BSA and LSZ have specific adsorption
sites: BSA adsorbs primarily via AlOH groups, whereas LSZ adsorbs
only via −COOH groups (1–2 −COOH groups on the
particle surface is enough to bind one LSZ molecule). Tailoring such
groups on the particle surface allows control of the composition of
a mixed BSA and LSZ adsorption layer. The results provide further
insight into how particle surface chemistry affects the composition
of protein adsorption layers on colloidal particles and is valuable
for the design of such particles for biotechnological and biomedical
applications