Table 2.

Optical biosensing platforms utilizing nanoparticles in their fabrication.

Biosensor	AD Biomarker	Sample Used	Limit of Detection	Fabrication Method	Ref.
LSPR–based AuNPs	Aβ42	Human CSF	1 pg mL−1	AuNP films coated on polyethylene terephthalate substrate	[65]
AuNSs and AuNCs	Aβ40 fibrils	Solution buffer	20 μM	Traditional seed-method, functionalized with C12C6C12Br2, combined with ThT in solution buffer	[69]
Shape-code nanoplasmonic AuNPs	Aβ40, Aβ42, tau protein (multiplex detection)	Mimicked blood	Aβ40 at 34.9 fM Aβ42 at 26 fM tau protein at 23.6 fM	Spherical and rod-shaped (long and short) AuNPs are fabricated, functionalized with PEG, and immobilized on a glass slide	[68]
AuNRs conjugated with CRANAD-2 AuNPs conjugated with double-stranded DNA aptamers	AβFs Exosome miRNAs	Mouse brain tissue Human serum	0.001 nM 3.37–4.01 aM	AuNRs modified with PEG spacers (HS-PEG-OMe and HS-PEG-COOH), functionalized with the D1 peptide AuNPs conjugated with double-stranded DNA aptamers, facilitating the formation of a programmable curved nanoarchitecture	[71] [74]
AuNPs conjugated with F-SERS probe	Aβ42	Mouse brain tissue	2 μM	Bifunctional AuNPs conjugated with Rose Bengal	[77]
AuNPs conjugated with Gua-HCl chaotropic agent	tau protein	Human blood	0.1 pM (100fM)	PEG treatment, AuNRs to conjugated antibody immune complexes, functionalized with EDC/NHS.	[79]
AuNPs quenched by CdTe QDs	AβOs	Solution buffer	0.2 nM	IFE utilized on CdTe QDs synthesized and combined with AuNPs	[85]
CuInS2/ZnS QDs	tau protein	Human serum	9.3 pM	QDs functionalized with dopamine are structured in a redox-mediated fluorescence immunoassay	[83]
Carbon QDs	AChE	Human serum	4.25 U L−1	Copper (II) ions interact with carboxyl groups on carbon QDs, resulting in fluorescence quenching	[86a]
Carbon QDs	miR-501-3p and miR-455-3p	Human serum	0.01 – 4 pM miR-501-3p, 0.01 – 5 pM miR-455-3p	Dual-signal DNA probe based on the fluorescent recovery of carbon QDs and sulfo-cyanine5 dye	[86b]
Graphene oxide UCNPs Graphene oxide magnetic NPs	BACE-1 Aβ1–42, P-tau-181	Blood plasmaHuman Serum	500 fM Aβ1–42 at 1.62 fg mL−1, P-tau-181 at 5.74 fg mL−1	UCNPs functionalized with EDC/NHS and conjugated with target-specific oligomers Graphene oxide magnetic NPs (Fe3O4@GOs) conjugated with tannin-coated AgNPs in a SERS-based probe	[84] [93]
ZnO-NPs	Aβ42	Human and mouse CSF, Mouse brain tissue	12 ag mL−1 (Human CSF)	Nanoporous ZnO-NPs conjugated with PDPP	[91]
PBNPs	Aβ40O	Human CSF	1 nM - 100 nM	PBNPs conjugated with FAM and modified with Aβ40O-targeting aptamer (FAM-AptAβ)	[92c]
MWCNT	tau protein	Solution buffer, artificial CSF	7.8 nM in solution buffer, 15.0 nM in artificial CSF	Carbon structures synthesized and fabricated in layer-by-layer method, creating walls of CNTs	[92b]
Negatively charged c-PNP	AβF, AβO	Human serum	15 μg mL−1 for AβF, 10 μg mL−1 for AβO	c-PNP synthesized using solid-phase peptide synthesis method	[92d]
SPR fiber-based	T-tau protein, p-tau protein	Human serum	2.4 pg mL−1 for T-tau protein 1.6 pg mL−1 for p-tau protein	Multimode fiber coated in Au film and mounted on PDMS ring-shaped flow cell	[92a]