TABLE 1.

Different methods to detect IL-6.

NO.	Test method	Detection limits	References
1	SERS,ICA	7.897 pg/mL	Xia et al. (2020)
2	SERS	1.6 pg/mL	Wang et al. (2021)
3	Optics	0.25 nM	Anastasopoulou et al. (2018)
4	SPFS	2 pg/mL	Toma and Tawa, (2016)
5	Fiber-optic	5p.m.	Kapoor and Wang, (2009)
6	Impedimetric aptasensor	1.6 pg/mL	Tertis et al. (2019)
7	Impedimetric immunosensor	6 fg/mL	Aydin, (2020)
8	Photoelectrochemical	0.38 pg/mL	Fan et al. (2014)
9	Electrochemical immunosensor	7 fg/mL	Cao et al. (2020)
10	Electrochemical immunosensor	0.059 pg/mL	Lou et al. (2014)
11	Fibre sensor	0.1 pg/mL	Zhang et al. (2018)
12	SERS	1 pg/mL	Wang et al. (2013)
13	Immunofluorescence	0.5 pg/mL	Shakeri et al. (2020)

SERS, surface enhanced Raman spectroscopy; ICA, immunochromatographic assay; SPFS, surface plasmon enhanced fluorescence spectroscopy.