Tag Archives: Nafisa Zohora

Shedding light on nanoparticles for better bio-imaging

25 July 2019:

CNBP researcher Dr Nafisa Zohora has been awarded her PhD in applied physics by Melbourne’s RMIT University. Her research project looked at materials that could be used as an alternative to available fluorophores – the fluorescent chemical compounds used in a variety of biological research projects.

The discoveries of the project solves a significant problem that was stopping scientists obtaining good images of biological samples.

Fluorophores are used to stain specific cells, for example, which are then observed and analysed by a fluorescence microscope. They are used as biomarkers to identify a range of bioactive molecules such as antibodies or proteins.

But for the fluorophores to re-emit light, they must first absorb it in a process known as “excitation” – usually brought about with a laser.

The problem is, though, that some compounds just do not absorb enough with low power excitation to produce enough fluorescence to be seen under the microscope. But higher power, from greater exposure to a laser for example, can also generate so much heat that the sample is destroyed.

The fluorophores are also inclined to lose their ability to emit within a few seconds with repeated exposure to the laser, not giving enough time to take a good image.

Nafisa set out to find a solution to both these issues. She began by studying the commercially available nanoparticle fluorophores such as cuprous oxide (Cu2O), titanium dioxide (TiO2) and zinc oxide (ZnO) but couldn’t find the properties she was looking for.

She then decided to synthesise her own nanoparticles.

After two years of hard work, she had successfully developed a methodology to synthesis Cu2O nanocubes that become very bright with a very low power excitation.

What’s more they are photostable for several hours under repeated exposure to a laser – so both problems solved!

In a follow-up collaboration with the University of Adelaide, Nafisa tested the nanoparticles for their toxicity to cells, giving them a clean bill.

Her work uncovering the exceptional properties of the synthesised Cu2O nanoparticles opens up new possible applications in detecting antigens and other long-term bio-imaging applications.

Nafisa’s supervisors were Professor Brant Gibson (Physics, RMIT University), Dr Ahmad Kandjani (Chemistry, RMIT University) and Professor Mark Hutchinson (The University of Adelaide). She completed her PhD on 1 July 2019, and her graduation ceremony will be in December.

Copper oxide nanocubes good for bioimaging

Nafisa Zohora4 December 2017:

New CNBP research determines that copper oxide nanocubes are suitable for long-term bioimaging experiments. Lead author on the paper – CNBP PhD student Zafisa Zohora (RMIT University).

Journal: Scientific Reports.

Publication titleFluorescence brightness and photostability of individual copper (I) oxide nanocubes.

Authors: Nafisa Zohora, Ahmad Esmaielzadeh Kandjani, Antony Orth, Hannah M. Brown, Mark R. Hutchinson & Brant C. Gibson.

Abstract:
Conventional organic fluorophores lose their ability to fluoresce after repeated exposure to excitation light due to photobleaching. Therefore, research into emerging bright and photostable nanomaterials has become of great interest for a range of applications such as bio-imaging and tracking. Among these emerging fluorophores, metal oxide-based nanomaterials have attracted significant attention as a potential multifunctional material with photocatalytic and angeogenisis abilities in addition to fluorescnce applications. However, most of these applications are highly dependent on size, morphology, and chemo-physical properties of individual particles. In this manuscript, we present a method to study the intrinsic optical characteristics of individual copper (I) oxide (Cu2O) nanocubes. When excited at 520 nm using only 11 µW excitation power (1.7 W/cm2), individual nanocubes were observed to emit light with peak wavelengths ~760 nm which is conveniently within the near-infrared 1 (NIR1) biological window where tissue autofluorescence is minimal. Bright and photostable fluorescence was observed with intensities up to 487 K counts/s under constant illumination for at least 2 minutes with a brightness approximately four times higher than the autofluorescence from a fixed cumulus-oocyte complex. With near-IR emission, high fluorescence brightness, and outstanding photostability, Cu2O nanocubes are attractive candidates for long-term fluorescent bioimaging applications.