Table 2.

Examples of label-free detection strategies.

Label-tree assay	Technology	Advantages	Disadvantages	Ret.
Optical transducer	Surface plasmon resonance	Real-time detection; possibility of high throughput	Sensitive to sample matrix effects; sensor surface functionalization challenging; bulky optical equipment	[23,24]
Electrical transducer	Redox electrochemistry (amperometric)	Simple sensor design; detection platform amenable to inexpensive and miniaturization	Redox species required to increase current production; no real-time detection; sensitive to sample matrix effects	[29,147,148]
	Impedance spectroscopy	Simple electrode design; real-time detection	Sensitive to sample matrix effects; bulky equipment; data analysis may not be trivial (theoretical model may be required)	[30,31,33]
	Potentiometry	Real-time detection; consecutive measurements on different samples are possible	Bulky equipment, sensitive to sample matrix; complicated sample preparation steps; careful control of temperature is essential	[34,149]
	Field effect transistor	Real-time detection; stable sensor response; detection platform amenable to POC system	Sensitive to sample matrix effects; complicated sensor fabrication; careful control of temperature is essential	[36,37]
Mechanical transducer	Microcantilever	Real-time detection; multiplex and high throughput are possible	Sensitive to sample matrix effects; careful control of temperature is essential; bulky equipment	[38–41]
	Quartz crystal microbalance	Simple electrode design; real-time detection; detection platform amenable to POC system	Sensitive to sample matrix effects; careful control of temperature and stress is essential	[42,43,150,151]

POC: Point-of-care.