Doctoral dissertation of MSc(Tech) Hannu Välimäki

Hannu Välimäki



Can drug screening technologies be useful when making human spare parts? According to the dissertation of Hannu Välimäki, a researcher of the Center of Excellence in Body-on-Chip Research, CoEBoC at Tampere University, the answer is yes. Optical measurement technologies that can improve the performance of label-based rapid immunoassays also perform excellently in the oxygen tension monitoring of stem cell cultures and human spare part processes.

Stem cell-based cell and tissue models can be used to study the functioning of various cells and tissues, development of diseases and traumas as well as the influence of medical substances or toxins. In addition, the models provide tools for a personalized medical testing and manufacturing of body spare parts.

An appropriate cell model requires a precise control of environmental conditions. Especially temperature, pH and oxygen tension need to be carefully regulated. For example, the oxygen monitoring is particularly important when creating ischemic conditions, i.e. oxygen deprivation in tissues, which is linked to many important diseases. A central component of the cell model control system is an oxygen sensor, which should generate real time information about the oxygen condition reliably and without harm or disruption to the cells. The dissertation developed oxygen measurement methods based on luminescent, i.e. light-emitting oxygen-sensitive indicators.

”Surface-selective optical measurement technologies combined with a biocompatible luminescent indicator material provides an excellent way for a real time oxygen monitoring that is highly sensitive, reliable and gentle for the cells. It also enables accurate local measurements and smoothly merges into a modular cell culturing system combining many measurement and imaging functions, developed in our research group“, Välimäki says.

In his dissertation, Välimäki has developed both optical sensing set-ups and biocompatible indicator materials. However, his work with the surface-selective luminescence methods started at VTT, the Technical Research Centre of Finland, more than ten years ago, when he developed technologies for rapid on-site drug screening.

“At that time, we understood that the surface-selective luminescence methods allow real-time monitoring of labelled immunological binding events even in challenging biological samples without any sample pretreatment. Based on this, we were able to speed up multiple developed drug tests”, Välimäki tells.

In addition to the drug screening, the measurement methods developed by Välimäki are well-suited for immunoassays of many other interesting molecules, including medical substances, hormones, environmental toxins, antibodies and viruses. The Covid-19 pandemic is a dire reminder of the importance of developing rapid medical tests.

The doctoral dissertation of M.Sc. (Tech) Hannu Välimäki in the field of Biomedical Sciences and Engineering titled Surface-selective Luminescence Methods ─ Enabling technologies for rapid immunoassays and chemical sensing in cell cultures was publicly examined in the Faculty of Medicine and Health Technology at Tampere University at on August 28, 2020. The Opponent was Professor Carl-Fredrik Mandenius from Linköping University, Sweden and the Custos was Professor Emeritus Jukka Lekkala from the Faculty of Medicine and Health Technology.

The dissertation is available online at