Development of sensors and compact, modular detection units for real-time monitoring in static conditions and in microfluidics

There is a growing demand for compact, cost efficient, and user-friendly sensors and analysis platforms, demanding the need for development of new detection systems and analysis tool. In this Ph.D. thesis, the development and application of novel electrochemical and optical sensors is presented, and the integration of modular electrochemical and optical detection units with centrifugal microfluidics is explored.
For studying the interaction of oral drugs with the catalase present in the intestine, a user-friendly electrochemical tissue-based biosensor was developed. The easy to use sensor provided a new way to monitor catalase activity in the intestine tissue and also provided new insights into the antioxidant capability of some commonly taken oral drugs such as paracetamol. Furthermore, we explored the combination of Surface-enhanced Raman Spectroscopy (SERS) with electrochemistry. The developed novel electrochemistry-assisted SERS platform facilitates the reusability of the SERS substrate and improves sensor sensitivity. The compact detection unit was used for quantification of melamine, an adulterant found in milk products.
In order to develop a portable and compact microfluidic analysis system, we designed and optimized modular detection units, which can be integrated with centrifugal microfluidics, Lab-on-a-Disc (LoD) systems. To eliminate the integration complexity, a disc-shaped, lightweight electrochemical detection unit, potentiostat-on-a-disc (PoD) was designed. The PoD was thoroughly characterized, and its performance was compared with a commercial potentiostat. The PoD combined with a microfluidic disc facilitated real-time electrochemical detection of the release of a model drug from oral drug delivery microdevices during rotation. With the integration of valving on the disc, the platform can be used to mimic the pH variations in the gut, and the system can facilitate monitoring the integrity of pH sensitive coatings used for sealing of oral drug delivery microdevices. Additionally, the integration of an optical imaging module on LoD was achieved, and the potential for real-time optical detection in centrifugal microfluidics was shown. The usage of modular detection units with LoD opens up new possibilities for developing portable, compact analysis systems for point-of-need on-site detection.