Table 4.

Advantages and disadvantages of multiple magnetic sensors.

Sensor	Advantages	Disadvantages	Examples
AMR	- Small operating field; - Linear operation; - Simple fabrication.	- Fragile at high temperatures; - Low MR ratio.	- 50 nm Fe3O4 chitosan nanoparticles were detected (detection limit: magnetic moments of 0.56 μemu) [160]. - 50 nm Fe3O4 chitosan nanoparticles were detected (detection limit of 1 μemu) [127].
GMR	- Moderate MR ratio; - Simple fabrication; - Linear operation.	- Noise at low frequencies.	- 100 nm FeCo nanoparticles were used for detecting DNA with sensitivity of 10 pM [161]. - 200 nm magnetic/polymer beads were used to detect proteins (detection limitation of 7.4 pg/mL) [134]. - 12.8 nm FeCo nanoparticles were used for detecting endoglin (as few as 1000 copies and concentration of 83 fM) [162]. - 4.5 μm beads were detected (as few as 10 beads) [132]. - 50nm Fe2O3 nanoparticles were to detect Immunoglobulin G protein (140 ng/mL limitation) [163].
TMR	- High MR value; - Low power consumption.	- Large noise; - Complicated fabrication.	- 250 nm streptavidin coated magnetic beads were used to detect DNA (sensitivity below the nM range) [144]. - 16 nm and 50 nm magnetic nanoparticles were used to detect 2.5 μM DNA with signal-to-noise ratios of 25 and 12, respectively [164]. - 200 nm Fe3O4 beads were detected (sensitivity to detect 500 ng at concentrations of 0.01 mg/m) [141].
MRX	- Avoids the high dynamic range requirement; - Potential for detecting two different particles.		- Fe3O4 magnetic nanoparticles were detected (volume of 150μL, 100 nmol Fe) [165]. - 22.4 nm Fe3O4 magnetic nanoparticles were used to detect breast cancer cells (with ability to detect fewer than 100 thousands cells) [166].