Surface Engineering

Laser Desorption Mass Spectrometry on Porous Silicon

Research is currently being undertaken to improve the detection of various illicit drugs with the use of pSi films and laser-desorption/ionisation mass spectrometry (LDI-MS). We also incorporate immunocapture function into the pSi films. This research may offer an alternative non-invasive method for detecting illicit drugs on the roadside or in the workplace.

Figure 11. Immunocapture pSi LDI-MS analysis. An antibody-modified pSi surface is exposed to analyte solution via the solid-liquid extraction method, following solvent and unbound molecule removal. The captured analyte molecules are then desorbed and ionized using a pulsed laser into the time-of-flight detector.

Diatom: Nature's Own nanotechnology

Biological materials are promising alternative to the existing fabrication technologies and provide a rich inspiration for the design of advanced materials and devices. The unicellular algae called diatoms are among the most spectacular examples of organisms capable of synthesising inorganic (silica) based structures into intricate architecture with ordered features from the micron to the nanoscale and multifunctional properties. Our research group is interested in exploring the properties of diatom biosilica (structural, chemical, optical and mechanical), and their potential for nanotechnological applications (optical devices, membranes and nanofabrications).

Figure 12. SEM images of diatom structures obtained from several species cultured in our lab

Cell Microarrays

Within the Voelcker lab, many projects are dedicated to cell-based microarray screening. We fabricate various surface-engineered cell microarrays and evaluate cell behaviour in response to biological and synthetic biomaterials. We evaluate potential platforms that enable stem cell isolation or generate specific cellular responses such as proliferation or differentiation.

We also design platforms that act as smart “self-sorting” cell arrays that allow us to selectively capture and study specific cells within a heterogeneous mixture of cells. Some of the advanced cell studies we conduct on the microarrays consist of studying DNA damage of human lymphocytes.

The overall objectives of our microarray based research aim to benefit the areas of regenerative medicine, on-chip diagnostic technologies, and preventative health technologies.

Figure 13. Lymphocytes immobilized on surface-engineered microarrays. The microarrays act as self-sorting cell platforms for separating cells into their respective lymphocyte subsets studying effects of cytotoxic and genotoxic agents.

Biological Surface Characterisation

Fibre-Forming Protein Aggregates
Bone Material Properties

FIBRE-FORMING PROTEIN AGGREGATES

Protein aggregation is a significant clinical issue since the formation of protein aggregates in the body can cause a range of diseases, from neurodegenerative diseases such as Parkinson's and Alzheimer's disease, to localised non-neuropathic diseases such as type II Diabetes, Cataracts and Pseudoexfoliation Syndrome. More recently, such aggregations have become the focus for biomaterial research, as the aggregates can form a wide variety of structures which may be applicable to biotechnological applications.

Figure 14. AFM height images of recombinant a-synuclein aggregation at different points of aggregation at 37°C.

BONE MATERIAL PROPERTIES

Current research involves usage of complementary analyses of the micro- and nanostructures of collagen-containing human bone matrixes to explore the factors affecting their structural and material properties. Of particular interest are the factors influencing bone mineral calcium (Ca) content, chemical and topographical mineral-protein interactions and micro- nanomechanical properties. We apply X-ray Photoelectron Spectroscopy (XPS), backscattered Scanning Electron Microscopy (bSEM), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), Atomic Force Microscopy (AFM), Nanoindentation, Matrix-Assisted Laser Desorption Ionisation - Time of Flight Mass Spectrometry (MALDI-ToF) and 2D Gel Electrophoresis to map and correlate the chemical composition, protein constituents and nanomechanical properties.

Figure 15. HIERARCHICAL STRUCTURE OF BONE: The term "bone" refers to a family of materials that have complex hierarchically organized structure. It goes from its “overview” or “macroscopic” level, which corresponds to the whole bone, down to the subnanostructure, which represents the molecular structure of constituent elements, such as mineral, collagen, and non-collagenous organic proteins. The varied arrangement of material structures at the many length scales work in concert to perform the diverse mechanical, biological and chemical functions of bone.

Dendrimer Nanocomposites

Our work focuses on metal nanoparticle formation and interaction with poly(amidoamine) (PAMAM) dendrimers, and potential biomedical applications. We employ scattering techniques (SAXS, SANS, and DLS) along with resonant techniques to investigate the different chemistries involved in nanoparticle formation. These investigations include interaction between the metal ions and the host matrix and nucleation and nanoparticle growth both in absence and presence of the host matrix. Microscopic methods (TEM and AFM) are used to support scattering data showing the nanoparticle size and shape as well as location of nanoparticle with respect to host matrix.

Figure 16. Schematic outlining the general procedure for producing dendrimer encapsulated metal nanoparticles.