22.6 Limitation of Biofunctionalized Nanoparticles for Environmental Application

355

Colorimetric sensors are the group of optical sensors that quantify/detect color in

response to external stimuli. Electrochemical biosensors use electrical and chemical

parameters and are further divided into conductometric, potentiometric, or amper-

ometric biosensors. The potentiometric biosensor reads the potential difference

between the analyte and reference probe in a medium. Conductometric biosensor

measures the flow of current through a medium when the analyte undergoes a

reaction with bioconjugated nanoparticles. In amperometric sensing, the current

is measured across two electrodes as a function of time during a redox reaction

between biomolecule and medium containing analyte. Various biofunctionalized

nanoparticles have been developed which can detect inorganic/organic compounds,

heavy metals, pesticides, herbicides, coliforms, and xenobiotics in soil and water.

An amperometric sensor fabricated by multiwalled carbon nanotubes conjugated

with mushroom tyrosinase is developed to sense bisphenol A in plastic products.

Another amperometric biosensor designed from liposome bioreactor and chitosan

nanocomposite along with mushroom tyrosinase was successfully tested for sensing

the presence of phenolic compounds. A biosensor fabricated from urease enzyme

and ZnO nanoparticles was developed by Eghbali et al. and can detect urea in water

[39]. A core–shell magnetic iron functionalized with acetylcholinesterase is demon-

strated for the sensing of organophosphorus pesticide. This biosensor was able to

retain its activity even after prolonged use in initial trial. Heavy metal pollution is

the most persistent problem across the globe. It affects both soil and water bodies.

A colorimetric sensing assay developed by Liu and Lu uses the Au nanoparticle

cross-linked DNAzyme. In the presence of water contaminated with Pb²⁺, the

cleavage of cross-link was seen, which trigger a color change in the medium of

action [40]. Various pathogen and coliform recognition sensors have also been

developed using nanoparticles and antibodies. Engineered/polyclonal/monoclonal

antibody-conjugated nanoparticles have been tested for their capability to sense the

presence of viruses, bacteria, spore, toxins, and xenobiotics.

22.6

Limitation of Biofunctionalized Nanoparticles

for Environmental Application

Nanoparticle-based remediation innovations have gained a lot of attention in recent

years. The inherent properties of nanoparticles and biofunctionalized biomaterials

make them an exceptional tool to be used in maintaining the well-being of our

environment. These extraordinary capabilities of nanoparticles support their use

but also attract the researcher’s attention to the novel toxicity caused by them.

With widespread use, nanoscale materials can find their way to air, water, and

soil. Nanoparticles can affect the food chain and, ultimately, the heath of animals

and humans. Once reactive nanoparticles find their way to the living organism,

they lead to the production of reactive oxygen species, which can later affect DNA,

proteins, and cellular membranes. Inhalation of nanoparticles with people affected

with asthma can cause long-term lung disorders. In a study conducted in a mouse

model, exposure to carbon nanotubes has shown the development of granuloma