Based on the success of glucose sensors and ELISA assays enzymatic biosensors are expected to play a key-role in clinical, biochemical and biotechnological analysis. Nowadays, as more and more cancer antigens are being identified, this opens new possibilities for early cancer diagnoses based on enzymatic biosensing which is a key issue in cancer treatment. In order to make precise diagnoses, it is essential to have highly sensitive detection methods to be able to measure very low concentrations in early cancer stages. Existing ELISA tests are not sensitive enough.
Therefore, new methods such as enzymatic biosensors are required. The aim of this project is to create a new platform of sensing techniques with an increased sensitivity. The idea is to increase the number of enzymes and their activity by e.g. incorporating them into vesicles.
In a first approach a sandwich system with vesicles as a signal amplification target was developed . The QCM-D technique allowed for detecting antigen concentrations down to 5 ng/ml or 30 pM (see Figure 1).
Figure 1: Detection limit of sandwich assay with vesicles for signal amplification.
This system was then further developed by introducing enzymes into the system. Thereby, the vesicles were enzyme functionalized. The enzymatic signal - related to the number of enzymes and thus the number of antigens - was detected with electrochemical methods, such as cyclic voltammetry or chronoamperometry.
Figure 2: Sandwich sensor with enzyme functionalized vesicles for signal amplification.
The detection limits achieved with this sensor are low enough to detect the nowadays most commonly known cancer antigens.
We are currently working on enhancing the sensitivity by improving the vesicles, including other types of the latter, such as polymeric vesicles.
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