fast and sensitive conductometric biosensor for direct detection of phenol and
phenolic compounds using immobilized Pseudomonas sp. on the surface of gold
interdigitated microelectrodes by glutaraldehyde cross-linking in the presence of
bovine serum albumin. Cui et al. [23, 24] determined the cytotoxicity of heavy
metal-polluted seawater samples by constructing a toxicity biosensor Acinetobacter
baylyi Tox2 with a luminescent bacterium A. baylyi harboring a medium-copynumber plasmid. Yagur-Kroll et al. [91] proposed four methods to enhance the
performance of luminescent bacterial biosensors via promoter manipulation
by: (1) modifying the length of DNA fragments containing promoter regions;
(2) introducing a random gene mutant through directed evolution; (3) introducing
more specific site mutants into promoter sequences and (4) replicating promoter
sequences to increase binding sites of RNA polymerase. Through these four
methods, the sensitivity, response time and emission intensity of biosensors would
be significantly improved.
A wide range of algal bio-mediators based optical biosensor has been reported to
monitor significant pollutant compound in marine samples. A prior study was
conducted to determine the most appropriate biomediator for the determination of
pesticides in marine samples. The ability of Chlorella vulgaris-Tetrahymena
pyriformis symbiotic association as a sensitive biological mediator for the development of biosensor was determined [83]. In a study carried out by Gosset et al.
[37], a self-driven portable fluorimeter was reported to determine the A-chlorophyll
microalgal fluorescence, introduced by capillarity into disposable and low-cost
microfluidic chips based on xurography. Three microalgal cultures: Chlorella
vulgaris, Pseudokirchneriella subcapitata, and Chlamydomonas reinhardtii were
used for the development of the biosensor. A prior optimization of feasibility and
sensitivity parameters of biosensor, such as concentration of algal cells and
intensity of light, were carried out to calibrate the biosensor sensitivity with Diuron
(a toxic pesticide for microalgae). After that, the biosensor was engaged in monitoring of ten aqueous urban polluted samples to prove its consistency, reproducibility and performance for the determination of toxic discharges in the soil
ecosystem. Scognamiglio et al. [76] developed a paper and algae based biosensor
for the optical determination of nano encapsulated-atrazine, a well-known herbicide
with a highly effective post-emergence herbicidal activity. In this study, immobilization of the photosynthetic green microalgae Chlamydomonas reinhardtii was
carried out on a paper based substrate soaked with an agar thin-film and positioned
in a glass optical measurement cell, resulting in a totally eco-friendly technique. An
encapsulated atrazine was determined by varying parameter such as fluorescence,
which inversely proportional declined to the concentration of herbicide, in a range
of 0.5–200 nM. In order to determine storage stability, studies were conducted and
good results were obtained for up to 3 weeks. These results showed the applicability of the reported paper-based optical biosensor in smart agriculture for in situ,
eco-friendly, cheap and sensitive atrazine analysis.
268
R. Khan et al.
phenolic compounds using immobilized Pseudomonas sp. on the surface of gold
interdigitated microelectrodes by glutaraldehyde cross-linking in the presence of
bovine serum albumin. Cui et al. [23, 24] determined the cytotoxicity of heavy
metal-polluted seawater samples by constructing a toxicity biosensor Acinetobacter
baylyi Tox2 with a luminescent bacterium A. baylyi harboring a medium-copynumber plasmid. Yagur-Kroll et al. [91] proposed four methods to enhance the
performance of luminescent bacterial biosensors via promoter manipulation
by: (1) modifying the length of DNA fragments containing promoter regions;
(2) introducing a random gene mutant through directed evolution; (3) introducing
more specific site mutants into promoter sequences and (4) replicating promoter
sequences to increase binding sites of RNA polymerase. Through these four
methods, the sensitivity, response time and emission intensity of biosensors would
be significantly improved.
A wide range of algal bio-mediators based optical biosensor has been reported to
monitor significant pollutant compound in marine samples. A prior study was
conducted to determine the most appropriate biomediator for the determination of
pesticides in marine samples. The ability of Chlorella vulgaris-Tetrahymena
pyriformis symbiotic association as a sensitive biological mediator for the development of biosensor was determined [83]. In a study carried out by Gosset et al.
[37], a self-driven portable fluorimeter was reported to determine the A-chlorophyll
microalgal fluorescence, introduced by capillarity into disposable and low-cost
microfluidic chips based on xurography. Three microalgal cultures: Chlorella
vulgaris, Pseudokirchneriella subcapitata, and Chlamydomonas reinhardtii were
used for the development of the biosensor. A prior optimization of feasibility and
sensitivity parameters of biosensor, such as concentration of algal cells and
intensity of light, were carried out to calibrate the biosensor sensitivity with Diuron
(a toxic pesticide for microalgae). After that, the biosensor was engaged in monitoring of ten aqueous urban polluted samples to prove its consistency, reproducibility and performance for the determination of toxic discharges in the soil
ecosystem. Scognamiglio et al. [76] developed a paper and algae based biosensor
for the optical determination of nano encapsulated-atrazine, a well-known herbicide
with a highly effective post-emergence herbicidal activity. In this study, immobilization of the photosynthetic green microalgae Chlamydomonas reinhardtii was
carried out on a paper based substrate soaked with an agar thin-film and positioned
in a glass optical measurement cell, resulting in a totally eco-friendly technique. An
encapsulated atrazine was determined by varying parameter such as fluorescence,
which inversely proportional declined to the concentration of herbicide, in a range
of 0.5–200 nM. In order to determine storage stability, studies were conducted and
good results were obtained for up to 3 weeks. These results showed the applicability of the reported paper-based optical biosensor in smart agriculture for in situ,
eco-friendly, cheap and sensitive atrazine analysis.
268
R. Khan et al.