**5. Conclusions**

The paper-based biosensors developed for quantification of the synthetic hormone EE2 presented higher sensitivity when compared to the more complex and

**91**

*Paper-Based Biosensors for Analysis of Water DOI: http://dx.doi.org/10.5772/intechopen.84131*

sample pretreatment.

*in situ* analysis.

**Acknowledgements**

**Conflict of interest**

through project PTDC/CTAAMB/31756/2017.

We declare that there is no conflict of interest.

expensive LC-MS/MS methods [31, 32]. With respect to the developed biosensors for quantification of different metals (uranium [24], arsenite [30], and cadmium [23]), the LOD was lower than their respective MCLs, thus complying with regulatory requirements. Furthermore, *E. coli* was detected [21, 22] at concentration level similar or lower than the maximum CFU/mL allowed in fresh recreational water. Hence, the use of paper-based platforms in biosensors has allowed the development of simple, specific, sensitive, and portable devices for the detection of several types of target analytes in water, with possible features summarized in **Figure 3**. Most of the reported methods were applied to surface water and drinking water samples only, which are samples containing a reduced amount of organic matter when compared to wastewater. Hence, efforts to develop sensors that can deal with more complex matrices should be pursued, encompassing strategies that accommodate

The most frequently used transducers comprised electrochemical and optical methods, with analytical strategies based on colorimetric reactions, associated with image processing analysis. Besides the recent advances in the development of paper-based analytical tools and biosensor devices, their association to the analysis of contaminants in water is still an open research field with a high potential for the implementation of new portable and low-cost analytical methods for

This work received financial support from the European Union (FEDER funds through COMPETE POCI-01-0145-FEDER-031756) and National Funds (FCT/ MEC, Fundação para a Ciência e Tecnologia and Ministério da Educação e Ciência)

### *Paper-Based Biosensors for Analysis of Water DOI: http://dx.doi.org/10.5772/intechopen.84131*

*Biosensors for Environmental Monitoring*

agent). An LOD of 0.1 ppb was achieved.

able to detect as low as 10 CFU mL<sup>−</sup><sup>1</sup>

**5. Conclusions**

(reporter protein) at arsenite concentration above 8 μg L<sup>−</sup><sup>1</sup>

expensive techniques performed under lab environment.

tium [26] to report spiking pollution in wastewater influents.

*Schematic representation of the elements that compose paper-based biosensors.*

samples were spiked with 10 and 100 ppb of Cd2+, and other 11 metals commonly found in such type of water, containing also EDTA and ovoalbumin (masking

A semiquantitative approach based on a paper-based bacterial biosensor was applied [30] for the detection of arsenite in groundwater samples. It was observed that arsenite produced a visible blue color from substrate of β-galactosidase

lateral flow device was developed for uranium (VI) determination with an LOD (36 nM) below the action level established by the World Health Organization (126 nM) using an immunological competitive approach [24]. These sensors are a suitable tool for field analysis, in opposition to conventional time-consuming and

Sensors based on microbial metabolism were developed for application in wastewaters. Pollution peaks, meaning the abrupt change in concentration of organic and metal pollutant in wastewater treatment plants, can compromise the biological treatment phases by killing or inhibiting microorganisms present in sludge. Hence, untargeted sensors were developed using either biofilms [25] or bacteria consor-

Waterborne pathogens are a major public health as they can lead to several diseases such as cholera, typhoid fever, and dysentery. Hence, accessible, cheap, and disposable analytical tools for monitoring the presence of these pathogens are mandatory, especially in areas with low resources. In this context, an electrochemical paper-based biosensor [28] was developed for the detection of *E. coli* in water, as an indicator of fecal contamination and an indirect indicator of the presumptive presence of other gastrointestinal bacteria. Different *E. coli* strains (both pathogenic and nonpathogenic) were detected in uninoculated and inoculated lagoon water. The method was

The paper-based biosensors developed for quantification of the synthetic hormone EE2 presented higher sensitivity when compared to the more complex and

of pathogenic and nonpathogenic *E. coli*.

. Finally, a paper-based

**90**

**Figure 3.**

expensive LC-MS/MS methods [31, 32]. With respect to the developed biosensors for quantification of different metals (uranium [24], arsenite [30], and cadmium [23]), the LOD was lower than their respective MCLs, thus complying with regulatory requirements. Furthermore, *E. coli* was detected [21, 22] at concentration level similar or lower than the maximum CFU/mL allowed in fresh recreational water. Hence, the use of paper-based platforms in biosensors has allowed the development of simple, specific, sensitive, and portable devices for the detection of several types of target analytes in water, with possible features summarized in **Figure 3**. Most of the reported methods were applied to surface water and drinking water samples only, which are samples containing a reduced amount of organic matter when compared to wastewater. Hence, efforts to develop sensors that can deal with more complex matrices should be pursued, encompassing strategies that accommodate sample pretreatment.

The most frequently used transducers comprised electrochemical and optical methods, with analytical strategies based on colorimetric reactions, associated with image processing analysis. Besides the recent advances in the development of paper-based analytical tools and biosensor devices, their association to the analysis of contaminants in water is still an open research field with a high potential for the implementation of new portable and low-cost analytical methods for *in situ* analysis.
