MIP-based solid phase extraction cartridges combined with MIP- based sensors for the detection of microcystin-LR I. Chianella , S.A. Piletsky, I.E. Tothill, B. Chen, A.P.F. Turner Institute of BioScience and Technology, Cranfield University at Silsoe, Silsoe, Bedfordshire MK45 4DT, UK Received 11 February 2002; accepted 9 July 2002 Abstract Microsystin-LR is one of the most widespread and dangerous toxins produced by the freshwater Cyanobacteria. The contamination of water supplies with microcystin-LR has been reported in several areas around the world and the development of an easy-to-use, rapid, robust and inexpensive sensor for this toxin is urgently required. In this work an artificial receptor for microcystin-LR was synthesised using the technique of molecular imprinting. The composition of the molecularly imprinted polymer (MIP) was optimised using computer modelling. The synthesised polymer was used both as a material for solid-phase extraction (SPE) and as a sensing element in a piezoelectric sensor. Using the combination of SPE followed by detection with a piezoelectric sensor the minimum detectable amount of toxin was 0.35 nM. The use of MIP  /SPE provided up to 1000 fold pre- concentration, which was more than sufficient for achieving the required detection limit for microcystin-LR in drinking water (1 nM). This work is the first example where the same MIP receptor has been used successfully for both SPE and the corresponding sensor. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Molecularly imprinted polymer; Microcystin; Sensor; Solid-phase extraction 1. Introduction During the bloom period, certain genera of Cyano- bacteria (freshwater microorganisms also known as blue  /green algae) such as Microcystis , Anabaena , Nodularia , Nostoc and Oscillatoria produce potent cyclic peptide hepatotoxins such as microcystins (Car- michael, 1992). These hepatotoxins have a common cyclic structure with some variable sections (Fig. 1). So far, more than 50 different microcystins have been isolated and characterised and among them microcystin- LR is the most widespread hepatotoxic toxin (Trogen et al., 1998). In addition to acute hepatotoxicity, the tumour promoting activity of microcystins can threaten human health by low-level chronic exposure to these toxins in drinking water. Evidence for this includes the high incidence of liver cancer in China where there are high levels of microcystins in ponds/ditches water and in river water (Carmichael, 1997). Contamination of water supplies from cyanobacterial toxins has also been reported in several other areas around the world. Currently toxic compounds from Cyanobacteria are analysed using time consuming and expensive techni- ques such as chromatography (HPLC, TLC) and immunoassay (Chu et al., 1990). Therefore, the development of an easy-to-use, rapid, robust and inexpensive method (such as a sensor) for the measure- ment of low concentrations of these toxins has been recognised as a high priority (for example by the European Union Framework 4 Programme, 1998). Biosensors are analytical devices incorporating a biologically active (or biomimetic) sensing element either intimately connected to or integrated within a transducer (Turner et al., 1987). Several different biological components can be used as sensing elements for environmental monitoring including enzymes, re- ceptors and antibodies (Bilitewski and Turner, 2000; Kro ¨ger et al., 2002). Although these biological mole- cules are usually very specific and sensitive for the target analytes, their poor stability, high cost and time  Corresponding author. Tel.:  /44-1525-86-3000; fax:  /44-1525- 86-3001; http://www.silsoe.cranfiled.ac.uk/ibst E-mail address: i.chianella.1998@cranfield.ac.uk (I. Chianella). Biosensors and Bioelectronics 18 (2003) 119 /127 www.elsevier.com/locate/bios 0956-5663/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0956-5663(02)00165-3