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Scientists investigate zinc oxide nanostructures for biomedical applications

  • Scientists investigate zinc oxide nanostructures for biomedical applications

Photo: Siddharth Kankaria

Nanotechonology, the field of science that manipulates objects at atomic or molecular level, is tout to be the science of the future. Researchers across the globe are working rigorously to tapthe potential this possesses. In a recent multinational collaborative study, researchers from the Indian Institute of Science(IISc), Bangalore, the Heriot-Watt University, Edinburgh, UK, and the Georg-August-Universität, Göttingen, Germany, have tried exploring the biomedical applicability of zinc oxide (ZnO) nanostructures. The results of this study have opened up novel possibilities in nanoscience research, especially pertaining to the field of biomedicine.

“Besides requiring a low volume of material, due to their low surface to volume ratio and controlled crystal growth, nanostructures have tailored electronic and optical properties useful for modernandday-to-day electronic gadgets, as well as, portable medical devices”, says Dr. Moumita Ghosh, a former Ph.D. scholar at the IISc and the lead author of the study. “For example, in optical sensing, bothtransparency and good electrical conductivityarenecessary, which is difficult to obtain in the bulk form of materials. But with metallic nanostructures, transparency in the visible range of light, as well as good electrical conductivity, are achievable,”she explains while talking about the wonders of nanomaterials.

Photoluminescenceis a property where materials emitvisible light following absorption of a high-energy radiation. Some materials like zinc oxide nanostructures exhibit photoluminescence in the range of visible light and are useful in biomedical imaging, drug delivery,and biosensing. In addition to being photoluminescent, it is important that these materials are stable in bio-fluidic environments like blood. Since water is a major constituent of bio-fluids, it is not surprising that scientists, while studying such materials, examine their stability in water. Dr. Ghosh and her collaborators not only looked at the stability of zinc oxide nanostructures in water, but also discovered a method to resolve a major drawback of these nanostructures.

Earlier studies had reported dispersion of zinc oxide nanostructures in water but none of them had identified any morphological change. This study found that zinc oxide nanostructures undergo morphological degradation in water.  These nanostructures also tend to agglomerate in water. Due to this, and due to the presence of dissolved carbon dioxide in water, they disintegrate in water. In order to protect them, the researchersenclosedthem in an “envelope”-like we usually do to keep something safe. They found out that methanol based biocompatible non-ionic surfactant,such as Tween-20 in methanol,can form micelles around zinc oxide nanoparticles at high concentrations. This encapsulates the nanostructuresand protects them from morphological degradation in water.

“The surfactant is used to reduce the surface tension of a liquid medium. Here, it reduces the surface tension of the solvents and allows them to disperse uniformly. If the concentration of the surfactant is too high, it forms micelles”, explains Dr. Ghosh. This process is eerily similar to action of detergents, which also contain surfactants and forms micelles encapsulating dirt particles.

This proposed solution has not only enhanced the applicability of zinc oxide nanostructures but also has opened up novel possibilities. “This simple strategy opens up ZnO nanostructure to be used in biological research, thereby opening up several academic opportunities to perform more research on this topic. I expect research scholars with materials science, chemistry, as well as physics background, to study the application of these encapsulated nanostructures in voltage sensing and electromechanics at the cellular level”, hopes Dr. Ghosh.  

The researchers of the study have a long way ahead. Choosing a proper encapsulation material with an optimized thickness, which is transparent enough, is a major hurdle. “The results suggest that we have already achieved the first step. The next step would be to perform experiments with biological cells. I foresee that overcoming the possible hurdles and understanding the experiences gained from experiments, will need a couple of years to make it accessible to the applied field,” signs off Dr. Ghosh.

About the Authors: Dr. Moumita Ghosh was a research scholar at the Indian Institute of Science duringthe initial stage of this study. Further, she carried out this research in the IIIrd and IVth Institute of Physics, Georg-August-University-Goettingen, Germany.Currently, she is a postdoctoral researcher at IVth Institute of Physics, Georg-August-University-Goettingen, Germany. The other contributors to this research include Siddharth Ghosh,Dr. Iwan A. T. Schaap (currently inInstitute of Biological Chemistry, Biophysics and Bioengineering, Heriot-Watt University, Edinburgh), Prof. Christoph F. Schmidtfrom the IIIrd Institute of Physics, Georg-August-Universität Göttingen, Prof. Michael Seibt from IVth Institute of Physics, Georg-August-University-Goettingen, Germany, and Prof. G. Mohan Rao of the Instrumentation and Applied Physics dept., Indian Institute of Science, Bangalore. Dr. Moumita Ghosh can be reached at ghoshiisc@gmail.com.

About the Research: This is based on the research article titled  “Designing deoxidation inhibiting encapsulation of metal oxide nanostructures for fluidic and biological applications” which will appear in Journal of Applied Surface Science, and E-mail conversations with Dr. Moumita Ghosh.