Table 1.

Summary of selected label-free affinity impedance biosensors for comparison. Detection limits are estimated if not explicitly stated in the publication.

Probe	Target	LoD	Measurement	Var.	Excitation	Surface Chemistry	Reference	Year	Cit.	Comments
antibody	hIgG	50 ng/mL	ID-electrode nonfaradaic	Z @ freq	100 Hz?	polymer/probe mix	electrode w/ or w/o Ab	1991	[185]	one of first affinity impedance biosensors
antibody	IgG, anti-IgG	est. <1 ng/mL	2-electrode nonfaradaic	Csurf	100 mV @ 1 kHz	silane, linker	after-before, time course	1992	[133]	significant nonspecific binding
antibody	α-fetoprotein	est. 50 ng/mL	2-electrode nonfaradaic	Z @ freq	1.5 kHz	silane, linker	IgG-coated electrode	1997	[187]	SiO2 surface biased so no field-effect
antibody	HSA	1000 ng/mL	2-electrode nonfaradaic	Csurf	10 mV @ 20 Hz	various compared	time course	1997	[154]	results with HDA + linker, normalized
antibody	IL-2	est. 0.05 ng/mL	3-electrode nonfaradaic	Csurf	50 mV step	SAM, linker, C12 diluent	after-before	1998	[149]	several other Ab-target pairs tried
antibody	interferon-γ	0.00000002 ng/mL	3-electrode nonfaradaic	Z @ freq	10 mV @ 113 Hz	SAM, linker	time course	2001	[196]	flow system, large nonspecific signal
antibody	Schistosoma japonicum	0.1 ng/mL	3-electrode nonfaradaic	Csurf	50 mV step	PrA linker, thiol diluent	after-before, time course	2002	[191]	optimized several parameters
antibody	IgG	100 ng/mL	3-electrode nonfaradaic	Z @ freq	10 mV @ 10 kHz	conducting polymer entrapment	blank-coated electrode	2002	[90]
antibody	vitellogenin	420 ng/mL	3-electrode nonfaradaic	Rct	10 mV @ 10 – 105 Hz	conducting polymer, linker	after-before	2004	[206]	redox species in polymer
antibody	HSA	1.6 ng/mL	3-electrode nonfaradaic	Z @ freq	10 mV @ 34 Hz	polymer, linker	after-before	2005	[150]	optimized several parameters
antibody	transferrin	0.08 ng/mL	3-electrode faradaic	Csurf	50 mV step	Au nanoparticles, conducting polymer	after-before, time course	2005	[194]	significant nonspecific binding
antibody	α-fetoprotein	10000 ng/mL	3-electrode nonfaradaic	Csurf	50 mV step	various compared	after-before	2006	[190]	similar results for all surface chemistries
antigen	anti-HRP	0.024 ng/mL	3-electrode faradaic	Csurf	10 mV @ 0.05 – 104 Hz	SAM, linker	after-before	2005	[203]	includes some SPR data
antigen	anti-Der 12	est. 2000 ng/mL	3-electrode faradaic	Rct	5 mV @ 10−1 – 105 Hz	MPTS, Au nanoparticles	after-before	2006	[208]	Au deposited on GCE
antigen	antibody	0.00 ng/mL	3-electrode nonfaradaic	Csurf	50 mV step	thiol-probe, C16 diluent	after-before	2006	[193]	reverse array to test probe composition
aptamer	lysozyme	est. 1000 ng/mL	3-electrode faradaic	Rct	5 mV @ 10−2 – 105 Hz	ITO, SA, biotin-aptamer	after-before	2005	[116]
aptamer	IgE	19 ng/mL	3-electrode faradaic	Rct	5 mV @ 10³ – 105 Hz	SAM, linker		2005	[201]	small electrode array
aptamer	thrombin	3.6 ng/mL	3-electrode faradaic	Rct	5 mV @ 1 – 105 Hz	thiol-probe, C6 diluent	after-before	2006	[117]
ssDNA	ssDNA	0.0000000002 nM	3-electrode nonfaradaic	Csurf	50 mV step	thiol-DNA, C2 diluent	after-before, time course	1999	[188]	with very long target, large nonspecific signal
ssDNA	ssDNA	4 nM	3-electrode faradaic	Rct	10 mV @ 10−2 – 105 Hz	silane, Ag nanoparticle	after-before	2005	[209]
ssDNA	ssDNA	100 nM	3-electrode nonfaradaic	Rct	10 mV @ 0.5 – 105 Hz	polymer	after-before	2005	[207]	significant nonspecific binding