Agriculture Reference
In-Depth Information
ratio, they have been little used. In fact, they have not been used for the detection of
antibiotics (Huet et al.
2010
).
During the past four decades, there has been an increasing research on the
development of lactate biosensors mainly because of the association of lactate
with several severe clinical conditions. Elevated blood lactate concentration
might predict multiple organ failure and death of patient with septic shock. In
addition to the relevance in clinical diagnosis, the determination of lactate is very
important in other areas such as food analysis and fermentation (Bakker et al.
1996
;
Sartain et al.
2006
). The characterization and design of a lactate biosensor are
described. The biosensor is developed through the immobilization of lactate oxi-
dase (LOD) in a mucin- and albumin-composed hydrogel. The enzyme is then
cross-linked with glutaraldehyde to the polymeric matrix and entrapped between
two polycarbonate membranes. The hydrogen peroxide produced by the reaction of
lactate and LOD is detected on a Pt electrode operated at 0.65 V versus Ag/AgCl.
The performance of the biosensor was evaluated in matrixes with different amounts
of albumin, mucin and glutaraldehyde. High reproducibility in the response was
obtained when several biosensors were prepared with the same composition
(Romero et al.
2008
).
Few diseases have drawn more public and scientific attention than the transmis-
sible spongiform encephalopathy (TSE). The infectious agent behind TSE/BSE
(bovine spongiform encephalopathy) is a misshapen protein known as prion
(PrPSC), typically found in the brain and spinal cord tissue (Prusiner
1982
). The
prion protein that causes the transmission of TSEs is formed by the post-
conformational and translational change in the normal prion protein (Hope and
Manson
1991
; Prusiner
1991
). Prions are highly stable proteins, and they are
resistant to extreme conditions involved in food processing such as high tempera-
ture pasteurization, drying, freezing and radiation. An affinity-based biosensing
technique was enhanced using an anti-transmissible spongiform encephalopathy
monoclonal antibody to detect prion in 0.1 mol/l sodium phosphate buffer. Fluo-
rescein isothiocyanate (FITC) labelled with a prion epitope (QYQRES) was used as
a decoy for prions. Lowest detectable prion concentration was determined as
8 nmol/l in phosphate buffer. The biosensing scheme was used to probe the
presence of prions in baby formula and gelatin. The gelatin interfered with the
binding and the displacement reaction of the antibody, decoy and prion. Addition of
sodium dodecyl sulphate (SDS) at 0.3 mg/ml to gelatin samples enabled prion
detection in gelatin. The lowest detectable concentration of prion in gelatin was
0.5 nmol/l at 0.4 mg/ml gelatin. The baby formula samples produced light scatter-
ing, and the intrinsic peak of baby formula interfered with the dye peak. Serial
dilutions of baby formula were done to reduce the interference. Addition of Triton
X-100 at 0.454 mg/ml to the baby formula samples enabled the prion detection. The
lowest detectable concentration of prion was measured as 2 nmol/l for baby
formula. Gelatin, which is made from the beef bones and hides and pork skin, is
used for the manufacturing of many kinds of products including food, cosmetics
and drugs. The procedures used for gelatin production might reduce the infectious-
ness of BSE-contaminated raw material, but complete inactivation is not possible.
