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Sensors & Transducers Journal, Vol. 113, Issue 2, February 2010, pp. 1-17

In this review, we will discuss how QDs, PS, and Si-nanoparticles, can be used as biosensors and transducers or as drug delivery materials in biomedical studies.

2. Nanobiosensors

A biosensor is a device that detects, transmits and records the information regarding an analyte that combines a biological component with a physiochemical detection system. A nanosensor is a biosensor which acts on the nano-scale region. There are different types of nanobiosensors – optical biosensors, electrical biosensors, electrochemical biosensors, nanowire biosensors, nanotube based biosensors, viral nano biosensors and nanoshell biosensors.

Fig. 1 [118] shows a basic biosensor assembly, which includes a bioreceptor, i.e., a biological recognition element, a transducer and a processor. The biological recognition elements used are living biological systems like, cells, tissues, or whole organism and biological molecular species such us antibody, enzyme, protein etc. The transducer essentially acts like a translator which recognizes the biological or chemical event from the biological component and transforms it into another signal for interpretation by the processor, which then converts it into a measurable output.

Fig. 1. Components of a biosensor [Source: Ref. 118].

The transducers may have different forms depending on the type of parameters being measured. These are (a) Amperometric transducers [76]; (b) Potentiometric transducers [77]; (c) Piezoelectric transducers [78]; (d) Thermal transducers [79]; (e) Optical transducers [80]. Transducers act as an interface, which measures the physical changes occurred at the bioreceptor [102], and transforms that energy into a readable output.

Nanobiosensors have wide applications in the field of biology and environment. Among the biological applications, there are (a) DNA sensors: genetic monitoring of diseases, (b) Immunosensors: HIV, hepatitis, other viral disease, drug testing, environmental monitoring, (c) Cell-based sensors: functional sensors, drug testing, (d) Point-of-care sensors: blood, urine, electrolytes, gases, steroids, drugs, hormones, proteins and others, (e) Bacteria (E-coli, streptococcus, other) sensors: food industry, medicine, environmental and others, (f) Enzyme sensors: diabetics, drug testing, and others are important. The environmental applications are (a) Detection of environmental pollution and toxicity, (b) Agricultural monitoring, (c) Ground water screening, (d) Ocean monitoring.

Nanosensors can be used to measure biotargets in a living cell without affecting its viability in a major way [44]. The effect of nanotechnology is enormous on the sensor industry because most chemical, biological and even physical sensors depend on the interactions occurring at the nanoscale level. The

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