| Summary: | Our increased understanding of the molecular biology of disease has had a significant impact on healthcare. Genetics has allowed the identification of hereditary diseases and predisposition for others, such as cancer. However, for many diseases is it also necessary to monitor the expression of panels of proteins. The need to monitor protein expression presents a significant technological challenge requiring a highly multiplexed analytical technology with a sensitivity down to femtomolar-range. Low-cost photonic devices are highly sensitive to changes in their local environment and can be chemically modified to exhibit high specificity detection towards, for instance, proteins or DNA oligonucleotides. However, even if small-footprint photonic biosensors can be engineered in silicon microarrays, approaches to realise the very high-density, multiplexed sensing potential of photonic biosensors have yet to be demonstrated. This study aims to develop and demonstrate, for the first time, a dual-mode electro-photonic technology capable of highly multiplexed detection at the submicron scale and multiparameter profiling of biomolecules on the silicon photonics platform. Furthermore, the technology integrates electrochemical and photonic measurements in a single sensor platform. By combining the complementary information revealed by each of the domains it is possible to broaden the range of systems that are accessible for silicon photonics. Our dual-mode technology consists of microring resonators optimally n-doped (doping density of 7.5 x 10 16 cm −3 ) to support high-Q resonances (Q-factor ≈ 50, 000) alongside electrochemical processes in situ. This combination of sensing mechanisms enables the application of electrochemical methods for site-controlled immobilisation of receptor molecules. Furthermore, electrochemical characterisation of molecules bound to the sensor surface also provides direct quantification of binding density and unique insight into chemical reactivity, which is unavailable with photonic detection alone. This unique technology, based on the combination of electrochemical and photonic sensing on a silicon platform, not only enables detection of multiple biological molecules required for future clinical diagnostics, but also has the potential to impact on fundamental biochemical research.
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