Semiconductor nanocrystals or quantum dots (QDs) have
gained significant
attention in biomedical research as versatile probes for imaging,
sensing, and therapies. However, the interactions between proteins
and QDs, which are crucial for their use in biological applications,
are not yet fully understood. Asymmetric flow field-flow fractionation
(AF4) is a promising method for analyzing the interactions of proteins
with QDs. This technique uses a combination of hydrodynamic and centrifugal
forces to separate and fractionate particles based on their size and
shape. By coupling AF4 with other techniques, such as fluorescence
spectroscopy and multi-angle light scattering, it is possible to determine
the binding affinity and stoichiometry of protein–QD interactions.
Herein, this approach has been utilized to determine the interaction
between fetal bovine serum (FBS) and silicon quantum dots (SiQDs).
Unlike metal-containing conventional QDs, SiQDs are highly biocompatible
and photostable in nature, making them attractive for a wide range
of biomedical applications. In this study, AF4 has provided crucial
information on the size and shape of the FBS/SiQD complexes, their
elution profile, and their interaction with serum components in real
time. The differential scanning microcalorimetric technique has also
been employed to monitor the thermodynamic behavior of proteins in
the presence of SiQDs. We have investigated their binding mechanisms
by incubating them at temperatures below and above the protein denaturation.
This study yields various significant characteristics such as their
hydrodynamic radius, size distribution, and conformational behavior.
The compositions of SiQD and FBS influence the size distribution of
their bioconjugates; the size increases by intensifying the concentration
of FBS, with their hydrodynamic radii ranging between 150 and 300
nm. The results signify that in the alliance of SiQDs to the system,
there is an augmentation of the denaturation point of the proteins
and hence their thermal stability, providing a more comprehensive
understanding of the interactions between FBS and QDs.