Table 30.

Strategies demonstrated for the immobilization of nucleic acid probes on SiP sensors and representative surfaces.

Immobilization of Nucleic Acid Probes for Hybridization Sensing
Immobilization Strategy Type	Bioreceptor Subtype	Surface Pre-Treatment	Chemical Surface Modification	Linking Strategy	Targeted Probe Terminal Group	Sensor Type	Refs.
Covalent	DNA	Piranha treatment	ICPTS silanization	Direct conjugation to silanized surface	Amine	Si wafers and nanostructured Si	[291]
Covalent	DNA	NaOH and ethanol/water cleaning	GPTMS silanization	Direct conjugation to silanized surface	Amine	Hydex MRR	[172]
Covalent	DNA	Piranha treatment and thermal oxidation	APTES silanization	Sulfosuccinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate (Sulfo-SMCC) linker	Thiol	Si MRR and Si PhC	[201]
Covalent	DNA	Piranha treatment and thermal oxidation	TEOS-HBA silanization	Base-by-base in situ ssDNA probe synthesis via phosphoramidite method	-	Si MRR and Si PhC	[201]
Covalent	DNA	Piranha treatment	APTES silanization + S-HyNic surface modification	Conjugation of DNA probe with S-4FB for hydrazone bond formation with modified surface	Amine	Si MRR	[194]
Covalent	DNA	Nitric acid wash	APTES silanization	Succinic anhydride and EDC linker	Amine	Si3N4 MRR	[202]
Covalent	PNA	Oxygen plasma	11-hydroxyundecylphosphonate surface modification	3-maleimidopropionic-acid-N-hydroxysuccinimide linker	Cysteine tag	Si nanowires	[270]
Covalent	DNA	Ethanol and water rinse	-	Direct UV crosslinking on surfaces	No tag and poly(TC) tag	Glass slides (unmodified and GAPS II™ aminosilane coated)	[273]
Covalent	DNA	Piranha treatment	APTES silanization	BS3 linker	Amine	Si MRR	[195]
Covalent	DNA	Piranha and oxygen plasma treatment	Electrografting of alkyne- and azide-presenting diazonium salts	Cu-catalyzed azide-alkyne click reaction	Azide and alkyne	N-doped Si MRR electrophotonic sensor	[59]
Covalent	DNA	Piranha treatment	HyNic silane surface modification	Conjugation of DNA probe with S-4FB for hydrazone bond formation with modified surface	Amine	Si MRR	[109,196,198,303]
Covalent	DNA	Oxygen plasma and nitric acid treatment	MPTMS silanization	Direct conjugation via disulphide bond formation	Thiol	Si3N4 Mach-Zehnder interferometer	[200]
Covalent	DNA	Oxygen plasma	APTES silanization	Glutaraldehyde linker	Amine	Si MRR	[23,197,199]
Covalent	Morpholino	Piranha treatment	APTMS silanization	Glutaraldehyde linker	Amine	Suspended Si photonic microring resonator	[110]
Covalent + bioaffinity	DNA (biotinylated)	-	3-isocyanatepropyl thriethoxysilane vapor silanization	Streptavidin conjugated to silanized surface and used as a bioaffinity linker	Biotin tag	Planar photonic crystal- waveguide-based optical sensor	[203]

ICPTS: 3-isocyanatepropyl triethoxysilane, TEOS-HBA: N-(3-triethoxysilylpropyl)-4-hydroxybutyramide.