Biomedical Engineering Reference
In-Depth Information
called as quadroma. Genetically, it is possible only to connect the vari-
able regions of two dif erent antibodies among themselves. h e resulting
antibodies very ot en contain two dif erent V
H
regions and two dif erent
V
L
regions. h ese bi-functional biomolecules are capable to recognise two
dif erent molecules in various regions. It is possible to attach them to one
molecule; whereas the second binding site is analyte specii c. For Examples
for the usefulness of bi-functional antibodies are immune-immobilisation
and secondary drug delivery to tumours cells [143].
Instead of using whole antibodies, only the binding sites parts of the
binding sites containing fragments which can be obtained either enzymati-
cally or genetically can be used. Enzyme scan cleave the important Fab
fragments from the Fc fragment which is not much important for most
sensor applications. h e enzyme papain is said to produces two Fab frag-
ments on every antibody, cutting the antibody into two parts that is the
hinge region and the Fab fragment. h e enzyme pepsin cuts the antibody
between the hinge region and the Fc segment, which result in F(ab)
2
frag-
ments.h e Genetic methods are more versatile and specii c. Numerous
antibody fragments have been produced and used in sensors application.
It has also been possible to produce the Fab fragments genetically. Fv and
scFv fragments have also been produced genetically by this method. Fv is
the smallest possible fragment which still guarantees complete binding of
antigen and scFv is cross-linked Fv for increased stability. Furthermore,
the Fab fragment has been cleaved and divided into two segments that is
H-chain segment (Fd) and the L-chain. Both the fragments have been used
eminently and signii cantly in biosensor applications.
It has been also possible to produce single CDRs and use them in ai n-
ity sensors for long time. h ese CDRs are useful, as they consist of only a
short amino acid chain and can be synthesised easily and cheaply. Recently
it is now possible to replace human CDRs in relating human antibodies with
the analyte specii c mouse CDRs. h e resulting antibody produced is specii c
and of much important for a certain analyte that can be used even in vivo in
humans, while the remaining antibody is not recognised as an intruder in the
human system. Due to the potentiality of recombinant antibodies, the anti-
bodies are produced much faster, with new binding properties such as speci-
i city, sensitivity etc. by which experiments on animals can be reduced [139].
7.9 Antibodymicroarrays
h e antibody microarray technology brings about great promise for pro-
tein expression proi ling of complex non-fractionated proteomes, having
