As nanomaterials continue to garner interest in a wide range of industries and
scientific fields, commercial suppliers have met growing consumer demand by readily
offering custom particles with size, shape and surface functionality made-to-order. By
circumventing the challenging and complex synthesis of functionalized nanoparticles,
these businesses seek to provide greater access for the experimentation and
application of these nanoscale platforms.
In many cases, amine functional groups are covalently attached as a surface
coating on a nanoparticle to provide a starting point for chemical derivatization and
commonly, conjugation of biomolecules in medical science applications. Successful
conjugation can improve the compatibility, interfacing and activity of therapeutic and
diagnostic nanomedicines. Amines are amongst the most popular reactive groups used
in bioconjugation pathways owing to the many high-yield alkylation and acylation
reaction are involved in.
For the design of functionalized nanomaterials with precisely tuned surface
chemical properties, it is important to develop techniques and methods which can
accurately and reproducibly characterize these materials. Quantification of surface
functional groups is crucial, as these groups not only allow for conjugation of chemical
species, but they also influence the surface charge and therefore aggregation behavior
of nanomaterials. The loss of colloidal stability of functionalized nanomaterials can often
correspond to a significant if not complete loss of functionality.
Thus, we sought to develop multiple characterization approaches for the
quantification of surface amine groups. Silica nanoparticles were selected as a model
nanomaterial as they are widely used, commercially available, and their surface
chemistry has been investigated and studied for decades. Various commercial batches
of silica nanoparticles were procured with sizes ranging from 20 – 120 nm. Two
colorimetric assays were developed and adapted for their ease-of-use, sensitivity, and
convenience. In addition, a fluorine labelling technique was developed which enabled
analysis by quantitative solid-state 19F NMR and X-ray photoelectron spectroscopy
(XPS). XPS provided data on surface chemical composition at a depth of ≈ 10 nm,
which allowed us to determine coupling efficiencies of the fluorine labelling technique
and evaluate the reactivity of the two assays.
The ensemble of surface-specific quantification techniques was used to evaluate
multiple commercial batches of aminated silica and investigate batch-to-batch variability
and the influence of particle size with degree of functionalization. In addition, resulting
measurements of surface amine content were compared and validated by an
independent method based on quantitative solution 1H NMR, which was developed for
total functional group content determination. This allowed for us to assess the role of
accessibility and reactivity of the amine groups present in our silica particles.
Overall, the objective of this study was to develop a multi-method approach for
the quantification of amine functional groups on silica nanoparticles. At the same time,
we hoped to set a precedent for the development and application of multiple
characterization techniques with an emphasis of comparing them on the basis of
reproducibility, sensitivity, and mutual validation.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/39480 |
| Date | 29 July 2019 |
| Creators | Sun, Ying |
| Contributors | Johnston, Linda |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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