. 2023 Sep 21;13(9):898. doi: 10.3390/bios13090898

Table 4.

Representative examples of recently developed fluorescent-based optical biosensors for the detection of IL-6.

Type of Biosensor	Strategy of Detection	LOD	Linear Range	Matrix	Advantages	Disadvantages	Ref.
Fluorescence/LFIA	A double-antibody sandwich immunofluorescent assay based on EuNPs combined with lateral flow immunoassay	0.37 pg mL⁻¹	2–500 pg mL⁻¹	Serum	High sensitivity and specificity, wide linear range, high reliability, acceptable reproducibility, short detection time (15 min)	Need a reading device	[32]
Fluorescence/FRET	A FRET-based aptasensor using nitrogen-doped carbon quantum dots and gold nanoparticles	0.82 pg mL⁻¹	1.5–5.9 pg mL⁻¹	Serum	High sensitivity and specificity, simple procedure	Narrow linear range, long incubation time (1 h), Need spectrofluorimeter to read the results, no evaluation of reproducibility	[79]
Fluorescence/fiber optic	Coating of streptavidin-modified fiber surface with biotinylated capture antibodies and conjugation of detection antibodies with three different fluorescent magnetic beads	12.5 pg mL⁻¹	12.5–200 pg mL⁻¹	Serum	High sensitivity and specificity	Narrow linear range, long incubation time (2 h), need a microscope to obtain results and then perform image analysis, no evaluation of reproducibility	[83]
Fluorescence/SPFS	Sandwich immunoassay based on captured antibody immobilization on PDA layer and its complex formation with IL-6 and fluorescent labelled detection antibody	2 pg mL⁻¹	2–2372 pg mL⁻¹	Serum	High sensitivity and specificity, wide linear range	Requirement of several steps in addition of reagents, time consuming process, no evaluation of reproducibility	[84]
Fluorescence/LFIA	Quantum dots (QDs)-based LFIA strip by conjugating CdSe/ZnS QDs to the IL-6 antibody and spraying onto conjugate pad, immobilization of captured antibody IL-6 mAb2 and rabbit anti-mouse IgG onto T and C lines, respectively	1.995 pg mL⁻¹	10–4000 pg mL⁻¹	Serum	High sensitivity and specificity, wide linear range, simple analysis, high accuracy, high stability of strips at high temperature, high precision and acceptable reproducibility, short detection time (18 min)	Need a reading device	[85]
Fluorescence/LFIA	Application of CdSe QDs as label for conjugation with detection antibody and utilization of two image processing software for quantification of results	1.38 and 2.28 nM	0–20 nM	Serum	High sensitivity and selectivity, good reproducibility, multiplex assay	Narrow linear range, need a reading device	[86]
Fluorescence	Quenching of aptamer–fluorophore conjugate by adsorption to the graphene oxide outer layer of graphene oxide/nickel/platinum nanoparticle micromotor (MM) in the absence of IL-6 and fluorescence recovery by the aptamer- fluorophore separating from the MMs in the presence of IL-6	0.02 pg mL⁻¹	0.07–1000 pg mL⁻¹	Serum	High sensitivity and specificity, wide linear range, the need for small sample volume	No evaluation of reproducibility, long incubation time (30 min)	[87]