Abstract
A photonic bandgap (PBG) biosensor has been developed for the label-free detection of proteins. As the sensing in this type of structures is governed by the interaction between the evanescent field going into the cladding and the target analytes, scanning near-field optical microscopy has been used to characterize the profile of that evanescent field. The study confirms the strong exponential decrease of the signal as it goes into the cladding. This means that biorecognition events must occur as close to the PBG structure surface as possible in order to obtain the maximum sensing response. Within this context, the PBG biosensor has been biofunctionalized with half-antibodies specific to bovine serum albumin (BSA) using a UV-induced immobilization procedure. The use of half-antibodies allows one to reduce the thickness of the biorecognition volume down to ca. 2.5 nm, thus leading to a higher interaction with the evanescent field, as well as a proper orientation of their binding sites towards the target sample. Then, the biofunctionalized PBG biosensor has been used to perform a direct and real-time detection of the target BSA antigen.
Highlights
The development of integrated lab-on-a-chip (LOC) devices for the highly sensitive and label-free detection of target analytes is one of the fields arousing high interest over the recent years [1,2]
We have developed a photonic biosensor based on photonic bandgap (PBG) sensing structures for the specific detection of proteins
A strong exponential decay has been observed in the scanning nearfield optical microscopy (SNOM) characterization carried out, highlighting the importance of having biorecognition layers as thin as possible for a high-sensitivity detection
Summary
The development of integrated lab-on-a-chip (LOC) devices for the highly sensitive and label-free detection of target analytes is one of the fields arousing high interest over the recent years [1,2]. We report the experimental work carried out to characterize and enhance the interaction with the target analytes in evanescent-wave-based sensors, for the case of PBG sensing structures, and to increase the sensitivity of the sensors.
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