**Acknowledgements**

traditional fragile nature, similarly to biological membranes, and suffer from low sensitivity and reproducibility which hampered their application in biosensor. The organic–inorganic material prepared by sol–gel method can yield a highly sensitive, robust and stable biosensor.

Hydrogels have also been extensively investigated as coatings support for immobilization of enzymes. Enzymes can often denature and lose their efficiency; however this effect can be mitigated by encapsulating it inside a hydrogel, because hydrogel is a type of waterswollen and cross-linked polymer formed by the gelling process and features a highly hydrophilic structure of three dimensional networks. And the consequent swelling of the polymer matrix provides a biocompatible microenviroment for the enzyme to maintain its natural configura‐ tion, thus is an ideal matrix for the massive entrapment of cell and enzyme. Moreover, the biosensors based on the hydrogel have high sensitivities. Although it exhibits a high affinity for water, it does not dissolve, and provides sufficient permeability for both solvent and substrate molecules so that they are capable of diffusing quickly through the water-swollen polymer which has reasonably high water content. In addition, the external hydrophobic organic solvent is unable to distort the native conformation of the entrapped enzyme in the sol-gel, and the hydrogel is soft and of rubbery consistence which closely resemble living tissues. Consequently, the widely utilised application for hydrogels has been as enzyme

Proper electrode fabrication using different materials for efficient electron transport has recently aroused much interest as a versatile tool for the constructing biosensors. Biosensors designed employing polymeric materials results in low detection limits, high sensitivities, lower applied potential, reduction of background, efficient electron transfer and easier immobilization of enzymes on electrodes. Application of organic CPs in biosensors has recently aroused much interest as potential candidates to enhance speed, sensitivity and versatility for electrochemical biosensors due to their easy preparation methods along with attractive unique properties such as high stability at room temperature, good conductivity output and facile polymerization and being compatible with biological molecules in a neutral aqueous solution. However, there are verious of challenges to be addressed in order to fulfill the applications of polymers. In addition, long laboratory synthetic pathways and costs are also involved in the production of the functional polymers. The aforementioned disadvantages of the above polymeric materials call for search for low cost biomaterials as alternative for the development of novel electrochemical sensors and biosensors. Those focuses towards design‐ ing smart polymers such as nanostructure doped polymers are the most promising for polymers to be further investigated. By combination of the unique properties of nanostructured material and various polymers, it is possible to develop novel enzyme-based bioelectronic devices with particular advantages. In particular, the integration of nanotech‐

nology, with novel polymeric materials should lead to very sensitive and fast assays.

stabilising agents [64-68].

82 State of the Art in Biosensors - General Aspects

**7. Conclusion and future perspectives**

I have benefited over the years from many publications with the authors of the papers cited. I thank them for their explanations and inspiration. I apologize to those whose work I have seemed to overlook.

Financial support from the the financial support from the National Natural Science Foundation of China (21205008), the Fundamental Research Funds for the Central Universities (DUT12LK31) and the Beijing National Laboratory for Molecular Sciences (BNLMS) are gratefully acknowledged.
