04-01-2013, 02:04 PM
Biosensors for clinical diagnostics industry
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Abstract
There is an urgent need in the medical diagnostics laboratories for accurate, fast and inexpensive devices, which can be routinely used. The
reliable and accurate information on the desired biochemical parameters is an essential prerequisite for effective healthcare. In this context,
biosensors are considered to provide viable solutions to the problems posed by the contemporary healthcare industry. This is because these
biosensing devices offer considerable advantages, such as specificity, small size faster response and cost. It is anticipated that these
bioanalytical tools can be used for frequent measurements of metabolites, blood cations and gases, etc. In this paper, an attempt has been made
to highlight some of the trends that rule the research and developments of some of the important biosensors that are likely to accelerate the
growth of clinical diagnostics industry.
Introduction
Diagnosis and monitoring of various diseases necessitate
intensive efforts for routine examination of blood samples
and other associated tests. These however require typical
analytical techniques, need efficient hands to perform the
job and time for collecting the desired samples for performing
clinical tests. Clinical laboratory testing enables qualified
personnel to diagnose and monitor various diseases.
Some of the analytes determined are known to be specific for
a given disease and hence can be helpful to monitor its
progress. The clinical utility of a biochemical test is determined
by its sensitivity, ability to detect the disease with no
false negatives and its specificity, i.e. the ability to avoid
false positives in a non-diseased person.
Technical development of biosensing devices
Biosensors are developed by immobilization of desired
sensing biomolecules to a support and coupling with a
physicochemical transducer. The most commonly used techniques
of immobilization are adsorption of inert carriers,
cross-linking by bifuctional reagents into the macroscopic
particles, physical entrapment in gel lattices, covalent binding
of water insoluble matrices, microencapsulation within
the wall spheres and electrochemical entrapment, etc. All the
methods can be broadly divided into two parts: attachment
and entrapment. The entrapped enzymes are isolated from
the large molecules, which cannot diffuse into the matrix.
The attached enzyme can be exposed to the molecules of all
sizes. Thus different form of kinetics is observed during the
reaction.
Clinical laboratory testing verses biosensing
devices
As a patient reaches a clinician for medical examination,
it is useful to first develop a problem list based on the history,
physical examination and basic laboratory studies. Synthesis
and analysis result in differential diagnosis with associated
disease probabilities. A selective use of diagnostic tests is
then used to rule in or rule out these possibilities, e.g., a
patient having symptoms of jaundice anorexia, fever and
abdominal pain, the relative increased level of liver function
tests will help to guide the subsequent evaluation. The type
of disease is decided by the biochemical parameter and the
level of increase. Clinical laboratories in the hospitals have
attained a significant growth during the past few years.
However, it is sometimes realized that these facilities are
inadequate due to long assay procedures and time consuming
sensitive procedures. This is particularly true for critical
care at the emergency, which requires accurate and quick
results. But delay in the results may affect the timely
commencement of proper treatment. A point of care system
has the practical utility to the physician only if it provides
analysis for a wide range of analytes with the same accuracy
as that obtained by the central clinical laboratories.
Clinical applications of biosensors
There has been a great demand for rapid and reliable
methods which can be used in biochemical laboratories for
determination of substances in biological fluids such as
blood, serum and urine, etc. There is also a demand to move
clinical analysis from centralized laboratories to a doctor’s
clinic and patients self-testing at home. Most of the methods
available in the market for rapid detection are based on
enzyme electrodes. They provide for a negligible enzyme
consumption of <1 mg per sample. The Glucometer GKM 01
was the first commercial enzyme electrode based glucose
analyzer developed in Europe. It was introduced in 1980 at
the Centre of Scientific Equipment of the Academy of
Sciences of the GDR. The glucometer is being adapted to
the quantification of uric acid, lactate and the activity of
acetylcholine esterase. The lipid analyzer ICA-LG 400 from
the Japanese company Toyo Jozo is capable of measuring
whole group of analytes, namely cholesterol, triglycerides
and phospholipids by using enzyme electrodes [40].
Although biosensors have found immense applications in
various fields, their use in health care monitoring is of utmost
importance.