Lena Golubewa, a researcher at the Department of Molecular Compound Physics at FTMC, has defended her PhD thesis on "Diversiform black silicon for bio-sensing" (academic supervisor: Dr. Renata Karpič, academic consultant: Prof. Dr. Polina Kuzhir).
Congratulations to our colleague and best wishes for the successful continuation of her important work!
We have heard a lot about the chemical element silicon. It is the second most abundant element (after oxygen) on our planet, accounting for about 28% of the Earth's crust. Silicon is hard, shiny, bluish-grey and occurs naturally as quartz (sand) or silicate minerals.
Silicon's unique properties for electronics have led to the current period of humanity being known as the Silicon Age; no suprise that the famous Silicon Valley, home to technology companies, is called so.
Black silicon was discovered accidently and considered as an unwanted byproduct of silicon industry. In fact, it is a 'normal' silicon, but with a significantly modified surface consisting of pyramids, needles, cones, holes, columns, pillars, etc. Such a surface determines high light absorption from UV to NIR, endowing black silicon with its color – mate black. However, exactly due to combination of these properties (developed surface and high absorbance), black silicon holds great promise in the field of hypersensitive sensors. The potential of this material has not yet been fully explored and is therefore attracting increasing interest.
In particular, Lena is interested in optical biosensors, which allow data to be collected by light at a distance (which is the least invasive method). Such sensors are expected to be useful in medicine and healthcare.
(Micro-structuring of silicon, acquired light-trapping properties and related to micro-structuring applications. Picture from L. Golubewa's dissertation)
Her thesis aimed to develop an inexpensive, reliable, safe and otherwise high-quality black silicon-based substrate suitable for SERS sensors. SERS is a surface-enhanced Raman spectroscopy, a highly sensitive technique from a family of vibrational spectroscopies, which allows obtaining characteristic information about materials with significant accuracy and specificity.
Such sensors should detect trace amounts of biomolecules, recognise specific changes in nanomaterials, and be suitable for analizing living cells. In her Thesis, by applying sensitive black silicon-based SERS substrate, Lena was able to solve one of the urgent problems of theranostics.
Theranostics is one of the most promising ways of detecting and treating cancer, combining diagnostics and therapy in one specific nano-agent - a tiny probe that enters the body, identifies the cancerous tumour and destroys it. For this to happen, the agent needs to be activated externally (by ultrasound, irradiation, etc.). Finally, after destroying the enemy, the nanoagent must be biodegraded and safely removed from the body. Black silicon-based SERS substrate allowed to disclose the mechanism of biodegradation of graphene-based nanomaterials used as anticancer theranostic nanoagents in glioma (brain tumor) cells.
Such technology sounds like something out of science fiction - but real science is moving towards it, and L. Golubewa is contributing to it too.
(Dissertation defence. Photo: FTMC)
"One of the parts of my Thesis is dedicated to the photothermoacoustic distruction of glioma cells accumulated single-walled carbon nanotubes (SWCNTs). The idea is that cancer cells accumulate SWCNT inside, agglomerate SWCNTs in micron-sized agglomerates and than interaction of pico-second laser pulses with these agglomerates leads to the generation of acoustic wave which, in turn, is enougn to destroy the membrane of a cancer cell.
In our case there is practically no overheating, which is usually a serious drawback of similar approaches as overheating touches not only cancer cells but also normal surrounding tissue. In our case due to specificity of our nano-agents and regime of its opthical activation we overcome this. But still there is a problem of after-treatment dust – „dust“ of graphene origin, which is released from cancer cells after the treatment. And here, in my Thesis, I demonstrate how our immune system react on this and black silicon-based SERS substarte allows opening up the way of nanomaterials biodegradation", says L. Golubewa.
According to the researcher, the most valuable outcome of her thesis is that FTMC team were able to disclose the potential of diversoform black silicon, which allowed them fabrication of cost-effective, reliable, reproducible, very sensitive and at the same time re-usable SERS substrates, also suitable for real-time living cell investigations.
"Nowadays, high cost, single use, unstability of SERS platforms significantly limits the development of SERS market, while food and drug safety and healthcare (as we see it from the Covid pandemy) requires great amounts of simple, reliable and cheap solutions for SERS bio-sensing industry. I really hope, that our research allowed us to take another small step in this direction."