Thermal Biosensors in Biotechnology - Advances in Biochemical Engineering Biotechnology - page 40

Table 2. Enzyme thermistors for clinical chemistry

Analyte Immobilized Concentration Reference

enzyme range [mmol/l]

ascorbic acid ascorbate oxidase 0.05-0.6 Mattiasson et al.1982

ATP apyrase 1-8 Mosbach/

Danielsson 1981

cholesterol cholesterol oxidase 0.03-0.15 Danielsson et al.1981a

cholesterol ester cholestrol oxidase + 0.03-0.15 Danielsson et al.1981a

cholestol esterase

creatine creatinase + sarcosin 0.1-5 Lammers 1996

oxidase + catalase

creatinine creatinine iminohydrolase 0.01-10 Danielsson et al.1981a

ethanol alcohol oxidase + catalase 0.01-2 Guilbault et al.1983

glucose glucose oxidase + catalase 0.002-0.8 Schmidt et al.1976

hexokinase 0.5-25 Bowers and Carr 1976

lactate lactate-2-monooxygenase 0.01-1 Danielsson et al.1981a

lactate oxidase+catalase 0.005-2 Danielsson 1994

oxalic acid oxalate oxidase 0.005-0.5 Winquist et al.1985

oxalate decarboxylase 0.1-3 Danielsson et al.1981a

pyrophosphate pyrophosphatase 0.1-20 Satoh et al.1988

triglycerides lipoproteine lipase 0.1-5 Satoh et al.1981

urea urease 0.01-500 Danielsson et al.1988

uric acid uricase 0.05-4 Danielsson et al.1981a

have attracted great interest.Here,antibody specificity to an antigen is used for
protein analysis. Due to its time-consuming nature, bioengineers require fully
automized systems for process monitoring of special proteins like monoclonal
antibodies or recombinant t-PA.Automated immunoanalyzers allow a real-time
process control whereas the well established ELISA kits only perform a process
documentation.
On the basis of an enzyme thermistor,Mattiasson et al.(1977) developed one
of the first immunosensors.Immobilized antibodies against albumin are placed
in a column and set into an ET. After injection of an albumin-sample and a
known amount of enzyme-labeled albumin,both are separated from the sample
matrix by antibody-antigen-interaction.After injection of a substrate,the chan-
ge in heat is a measure of analyte concentration.The less heat produced means
that more albumin has been bound.An elution step regenerates the ELISA.Due
to its thermal detection principle,the procedure is called TELISA (thermome-
tric enzyme-linked immunosorbent assay).Figure 3 shows the principle of the
TELISA procedure in its sandwich configuration.
Table 3 illustrates the various proteins that have so far been determined using
a TELISA.Nevertheless,the TELISA competes with recently developed fluores-
cence assays.The latter are cheaper,more sensitive and faster due to not need-