Aneconomical single use optical biosensor has been developed for lead detection
using a microfluidic approach. The present study represents the initiative step
for amalgamation of microfluidic and advanced biosensor technologies which
offers rapid analysis with lab-on-a-chip policy. Urease producing Bacillus
sphaericus was co-immobilized with phenol red (pH indicator) in the glass
capillary which acted as a microchannel. For immobilization, a combination of
sol-gel approach and calcium alginate method cited first time in literature was
used which reduced the time of solidification to seconds as compared to hours
with sol-gel alone. Bioassay principle was based on urease inhibition in the
presence of lead. Fiber optic spectrophotometer was used as transducer which
measured the intensity of color change. Linear relationship (10-1000 μg/L) was
observed between logarithmic concentration of lead and absorbance. The study
resulted in the development of cheap, miniaturized, sensitive and reliable lead
biosensor with requirement of small sample volume (1 mL).
Increasedenvironmental awareness and stringent environmental regulation led to the dire
need of the techniques for the fast, easy and economic detection of various
pollutants like heavy metals, pesticides and toxic gases. Heavy metals are
among the most hazardous pollutants due to their ubiquitous presence in the
biosphere, their bioavailability from both natural and anthropogenic sources as
well as their high toxicity even at trace level. Lead is among the toxic
heavy metals which harm the body when present above the threshold concentration. The higher concentration of lead (>18 μM) in the blood may cause coma
and death. It affects different parts of the body particularly brain and
central nervous system. Accumulation of lead in the body produces damaging
effects associated with hematology, neurology and nephrology which include
paralysis, mental retardation and neural deafness. The substitution of calcium
in the body with lead causes impairment in the development of bones and teeth. Human exposure to lead occurs primarily through leadbased paints,
industrial waste, water from lead-laden pipes, soil and dust generated from
gasoline and food items like milk, dairy products and imported candies. The
cattle grazing on the metal contaminated fields transmit lead contamination in
the milk and dairy products. A threshold lead limit of 10 μg/L was
estimated in food and water by the International Agency for Research on Cancer
(IARC) while 5 μg/L in drinking water by Environmental Protection Agency (EPA). It is mandatory, therefore, to detect the lead in food samples and
drinking water to prevent the deleterious effects of lead. Conventional methods
to detect heavy metals like differential pulse polarography, Atomic Absorption
Spectrophotometry (AAS), Differential Pulse Cathodic Stripping Voltametry
(DPCSV) are superseded by the use of biosensors.
Biosensorsare analytical tools capable of providing either qualitative or quantitative
results, consisting of an immobilized biological recognition element such as an
enzyme, antibody or cell receptor immobilized to a physicochemical transducer
to create a single unit. Now-a-days biosensor technology has emerged as the
most promising tool for detection of heavy metals being costeffective, fast, selective,
sensitive, portable, easy to use and reliable. A number of lead biosensors
have been developed using various transducers like conductometer,
electrochemical and optical based on whole cell, enzymes or
DNAzyme.
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