Deoxyribonucleic acid (DNA) can be considered the most important of all biomolecules for diagnostic purposes. Scientist have already undertaken a great deal of genetic analysis of the unique complementary structure between its base pairs of DNA (adenine/thymine) and (cytosine/guanine). The extraordinary ability of a single stranded DNA (ssDNA) molecule to hybridize to its complementary strand in a sample has provided a basis for arrange of DNA-based detection systems. Currently, there is a strong demand from areas including medical, scientific and environmental to progress such systems to a level at which they can be used for simple, cheap, rapid and reliable detection of specific genes.

DNA sensors operate in a similar way to any other kind of biosensor. The basic design comprises the same three parts. The first step is the hybridization of a target DNA to its complementary sequence immobilized on the surface of biorecognition site. The second step is the transduction of the resulting signal and the third and final step is the detection of this signal into an output which is measurable and interpretable.The immobilization step for the DNA probe is critical for to achieve a high level of sensitivity and selectivity depends on minimizing nonspecific adsorption and stabilizing the immobilized molecules. Because a critical distinctive property of nanoparticles (NPs)is their large surface area this provides a desirable high density of biomolecule immobilization for DNA sensing. NPs have all diameters less than 100 nm making them roughly the same size as biomolecules like proteins, antibodies, and membrane receptors.

In particular, iron oxide NPs are demonstrating great potential in biosensing. Nano sized magnetite Fe3O4 exhibits excellent magnetic properties, its superparamagnetic behavior becoming apparent when at a maximum of 20–30 nm in diameter.In response to a magnetic field, MNPs can be very easily magnetized and demagnetized. Additionally they have other unique and useful properties including a high surface to volume ratio,high biocompatibity and it is relatively simple to synthesize them and to functionalize their surfaces.

Quantum dots are versatile nanocrystals which, when excited, produce optically stable fluorophores of various wavelengths (from ultra violet to infrared). In biosensors, synthesized quantum dots are better than conventional fluorescent dyes because of their stability, stronger fluorescent intensity, and their range of colours. Each of these features can be adjusted by controlling the size of the dots.

For further reading, please refer to:

  1. Nur Ellina Azmi, Noor Izaanin Ramli, Jaafar Abdullah, Mohammad Azmi Abdul Hamid, Hamidah Sidek, Samsulida Abd Rahman, Nurhayati Ariffin, Nor Azah Yusof. Biosensors and Bioelectronics 67, 2015. pp129-133
  2. Roozbeh Hushiarian, Nor Azah Yusof, Negin Houshiarian, Abdul Halim Abdullah, Shahrul Ainliah Alang Ahmad. Sensors and Actuators B: Chemical 207, 2015. pp 716-723
  3. Salamatu Aliyu Tukur, Nor Azah Yusof, Reza Hajian, Sensors Journal, IEEE 15 (5), 2015. pp 2780-2784
  4. Jahwarhar Izuan Abdul Rashid, Nor Azah Yusof, Jaafar Abdullah, Uda Hashim, Reza Hajian, Materials Science and Engineering: C 45, 2014. pp 270-276