Development and application of MIPbased sensors

During the past decade the number of application of MIP-based sensors has increased drastically.

The high selectivity and affinity properties of MIP for target analytes make them ideal recognition elements in sensors development [63].

Capacitive [189], conductimetric [190], field effect [191], amperometric [192] and voltammetric [193] electrochemical transduction systems have been used.

On the basis of conductimetric transduction by Piletsky et al. [190] sensors for herbicide analysis have been developed with a linear range of 0.01-0.50 mg/L for atrazine, without interference of simazine. Chloroaromatic acids were determined by Lahav et al. [191] using a TiO2 sol-gel system, and using a voltammetric transduction Pizzariello et al. [193] developed a sensor for clembuterol analysis.

MIP-based sensors coupled to piezoelectric transducers are one of the most promising areas. Different devices have been developed for their use in food industry, such as a supported-piezoelectric detection based on MIP for the quantification of caffeine content in coffee and tea samples [194], the detection of sorbitol [195], antibiotics in milk [174], and the detection of toxicant compound such as PAHs [196].

Another optical transducers reported is a chemiluminescent sensor for clembuterol determination [197]. Applications of MIP-based sensors for contaminant analysis are summarized in Table 5.

In spite of the development in this field, MIPs still have a series of limitations:

• Unless the print-material is inexpensive, their preparation is very costly

• There is a lack of robustness and sensitivity, due to inefficient removal of the print molecules during MIP preparation

• Several times there is a lack of reproducibility

• General MIP preparation procedures are adequate at the laboratory level, and now these preparation procedures need to be developed for scaling up to commercial production.

Table 5 Examples of MIP-based sensors for food toxicant analysis

Analyte

Functional monomer

Transduction

Reference

o-Xilene

NS

QCM

[198]

2,4-Dichlorophenoxy-

4-VP

Electrochemical

[199]

acetic-acid

detection using screen

printed electrodes

Atrazine

MAA+EDMA

Amperometric

[200]

detection

Trichloroacetic acid

4-VP+EDMA

Conductimetric sensor

[201]

and haloacetic acids

Domoic acid

2-(Diethylamino)

SPR-QCM

[202]

ethyl methacrylate

Ochratoxin A

Polypyrrole film

SPR (SPREETA)

[203]

Sulphamethazine

MAA

Voltammetric

[204]

Caffeine

MAA+EDMA

BAW

[140]

Note: PQC, piezoelectric quartz.

Note: PQC, piezoelectric quartz.

However, new polymeric strategies have been proposed in order to overcome these limitations. For example, Jodlbauer et al. [138] reported the development of an OTA-selective MIP material, specifically designed to recognize and bind OTA under polar protic conditions, using as a functional monomer Q-MMA, auxiliary monomer tBu-MAA and the OTA-mimicking template. Recently, Maier et al. [180] reported the application of this material for the investigation of OTA in red wines using a two-dimensional SPE clean-up protocol on C18-silica and a target-selective MIP. The combined protocol afforded extracts suitable for sensitive OTA quantification by HPLC-fluorescence detection. In this study, problems inherent to MIP-based SPE have been addressed including the reproducible preparation of MIP materials with consistent molecular recognition characteristics, the potential for repeated use of MIP, unfavourable polymer swelling in application-relevant solvents, potential sample contamination by template bleeding and slow analyte binding kinetics.

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