Table 2.

Strategies used for the development of detection probes for enhanced detection.

Detection Probe	Components	Preparation Conditions	Ref.
HRP, Anti-CEA/AuNPs-PAN@CNTs	PAN@CNTs	(NH4)2S2O8 based polymerization of CNTs and aniline monomers solution in HCl at ice bath	[47]
	AuNPs	Citrate reduction
	AuNPs-PAN@CNTs	Electrostatic assembly of AuNPs
HRP-PSA aptamer/AuNP-PAMAM	AuNP	Citrate reduction	[70]
	thiol-PAMAM	Treating amine-terminated PAMAM dendrimer (G4) with methyl mercaptoacetate at 50 °C for 18 h
	AuNP-PAMAM	Incubation for 5 h at RT
Thi-Anti-AFP/HRP NPs-hollow AuNPs	hollow AuNPs	HAuCl4 reduction in N2 environment using NaBH4, sodium citrate and CoCl2·6H2O mixed solution	[40]
	HRP NPs-hollow AuNPs	Self-assembly of L-cysteine modified HRP-NPs prepared via desolvation followed by glutaraldehyde chemistry;
	Thi-Anti-AFP	EDC/NHS chemistry
HRP, anti-AFP/Fe3O4 NPs-MSNs	Fe3O4 NPs-MSNs	Treating APTES modified MSNs with bromine-functionalized Fe3O4 NPs in EtOH	[64]
AgNPs-GOx-anti CEA	AgNPs	Ag nanospheres prepared via ethylene glycol (EG) and poly(vinyl pyrrolidone) (PVP) based reduction	[56]
HRP-anti CA 19-9/Au@SBA-15	Au@SBA-15	incubating PDDA coated SBA-15 particles with AuNPs solution	[74]
Anti-CEA/Ag/Au–DN–GR	Ag/Au–DN–GR	(i) HAuCl4, AgNO3, trisodium citrate dihydrate and SDS mixture reduction using NaBH4, (ii) Mix and incubate Ag/Au with DN-graphene	[34]
PAMAM-Gr/anti-AFP-HRP	PAMAM-Gr	EDC/NHS chemistry	[50]
HRP, GOD, anti-AFP/SWCNHs	Carboxylated SWCNHs	Acid treatment of SWCNHs	[73]
AuNPs-MCF	carboxy-MCF	Refluxing MCF in acid	[71]
	AuNPs-MCF	NaBH4 based reduction of HAuCl4-MCF mixture
CHIT-PB-AuNP CHIT-FC-AuNP	CHIT-PB	Treating K3Fe(CN)6 and FeCl3 solution (pH 1.5) in CHIT	[52]
	CHIT-FC	EDC/NHS chemistry;
	AuNP binding	Physical adsorption by mixing
anti-AFP2,2-AuNPs-Thi@rGO	AuNPs-Thi@rGO	(i) Incubating rGO and Thi for 12 h, (ii) Incubating Thi@rGO with AuNPs for 24 h, (iii) Mixing FeCl3 and K3Fe(CN)6 solution (pH 1.5) to rGO dispersion	[36]
anti-CEA2,1-AuNPs-PB@rGO	AuNPs-PB@rGO	(i) Mixing PB@rGO with PDDA, 30 min, (ii) Incubation with AuNPs
Anti-CEA /PB–CS-Au and Anti-CEA/Cd–CS-Au	PB–CS-Au and Cd–CS-Au	(i) PBNPs and CdNPs were prepared using FeCl3 and CdCl2 were first mixed with CS solution in 1% acetic acid, (ii) Incubating PBNPs and CdNPs with AuNPs	[44]
PLL-Au-Cd-Apo-Ab2 and PLL-Au-Pb-Apo-Ab2	PLL-Au	Incubating PLL with citrate reduced AuNPs	[59]
	Cd-Apo and Pb-Apo	Dropwise adding metal ions (Cd2+, Pb2+) to Apo solution pH 2 and adjusting pH to 8.5 before stirring for 3 h
anti-CEA/PtPNPs-Cd2+ and anti-AFP /PtPNPs-Cu2+	PtPNPs-Cd2+ and PtPNPs-Cu2+	(i) PtPNPs synthesised from chloroplatinic acid treatment with ascorbic acid in KOH, (ii) Mercapto-ethylamine modification of PtPNPs for capture of Cd2+ or Cu2+ ions	[29]
CdNCs–Au–anti-CEA and CuNCs– Au–anti-AFP	CdNCs–Au and CuNCs–Au	(i) Treating CdCl2 or CoCl2 in presence of CS with K3Co(CN)6 dispersed PDDA, (ii) Nanocubes incubation with AuNPs prepared via citrate and NaBH4 reduction	[53]
TB/Au@KIT-6/CMC/ILs-anti-CEA	Au@KIT-6	Treating APTES silanized KIT-6 with AuNPs prepared via NaBH4 reduction;	[45]
	TB/Au@KIT-6/CMC/ILs-Ab2	(i) Physical binding of anti-CEA on Au@KIT-6, (ii) TB binding using EDC NHS, (iii) Mixing and incubating with 1-butyl-pyridine tetrafluoroborate (ILs) dissolved in CMC
Ab2/M-Alg; (M: Cd, Pb and Cu)	M-Alg	(i) Emulsion A: agitate the mixture of triton x-100, 1-hexyl alcohol, n-octane and sodium for more than 30 min RT, (ii) Emulsion B: agitate mixture of triton x-100, 1-hexyl alcohol, n-octane and Metal salt for more than 30 min RT, (iii) Add emulsion A dropwise to emulsion B and stir for 4 h RT, (iv) Break M-Alg using acetone and ethanol to get M-Alg nanobeads	[43]
M/Ab2-Envision copolymer; (M: AuNPs, CdS and PbS)	Ab2-Envision copolymer	Mix and incubate Ab2 with Envision (highly branched polymer) at 4 °C, 24 h	[107]
	M/Ab2-Envision copolymer	AuNP tagging via physical adsorption, CdS and PbS were bound to HRP modified envision-Ab2 via EDC/NHS chemistry
Au@MCM-41/TB/Ab2	Au@MCM-41	APTES modified MCM-41 was mixed with AuNPs prepared via NaBH4 based reduction of HAuCl4	[57]
Au@CMK-3-anti-CEA-neutral red and Au@CMK-3-anti-SCCA-thionine	Au@CMK-3	AuNPs were prepared from sodium citrate based reduction of HAuCl4 were mixed and stir with mesoporous carbon CMK-3 for 4 h	[66]
AuNPs-Ab2-Cu2+ or Pb2+	AuNPs	Via sodium citrate based reduction of HAuCl4	[54]
	Cu2+ and Pb2+ tagging	Cu(NO3)2 or Pb(NO3)2 incubation with AuNPs-Ab2
Redox tag bio-dsDNA/SA/bio-Ab2/Au/SiO2-Fe3O4	Au/SiO2–Fe3O4	(i) Nano-sized Fe3O4 via treating FeCl2-FeCl3 mixture with NaOH, (ii) Fe3O4–SiO2 via alkaline hydrolysis of TEOS, (iii) Au/SiO2–Fe3O4 via mixing and incubating PDDA treated SiO2–Fe3O4 with for 20 min	[46]
	bio-dsDNA/SA/bio-Ab2/Au/SiO2-Fe3O4	(i) Incubation of biotin-Ab2 Au/SiO2-Fe3O4 12 h, 4 °C, (ii) Treatment with streptavidin (SA), initiator bio-S1, bio-S2 and bio-S3 in sequence to form bio-dsDNA/SA/bio-Ab2/Au/SiO2-Fe3O4 via HCR reaction
Anti-CA15-3–f-TiO2–Cd2+	nanoporous TiO2	(i) Mixing and stirring tetrabutoxytitanium (TBOT) and ethylene glycol for 8 h, RT, (ii) Pouring mixture in acetone-water followed by vigorous stirring 1 h, (iii) Ethanol wash and drying at 50 °C, (iv) Mix with water and reflux for 1 h	[32]
	f-TiO2–Cd2+	(i) APTMS treatment to get NH2 functionalized nanoporous TiO2 (f-TiO2), (ii) Mixing f-TiO2 with Cd(NO3)2 and stirring for 24 h at 50 °C
Anti-PSA/Fc-AuNPs	Fc-AuNPs	Self-assembly of 6-ferrocenyl hexanethiol onto AuNPs	[68]
Apt/Thi-AuNPs/SiO2@MWCNTs	Apt/Thi-AuNPs/SiO2@MWCNTs	(i) Treat COOH-MWCNTs (c-MWCNTs) with PDDA, (ii) TEOS modification to get SiO2@MWCNTs, (iii) Treatment with PDDA, (iv) Incubation in AuNPs solution to obtain AuNPs/SiO2@MWCNTs, (v) Mixing and incubating with thionine 1 h, RT, (vi) Incubation with SH-Apt solution	[58]
Ab2-PGN	rGO	Mix and refluxing GO with PEI	[48]
	PGN	Mix H2PtCl6 with rGO and treat with NaBH4
Anti-CEA/APTES/3DGS@MB and anti-AFP/APTES/3DGS@Fc-COOH	3DGS	NaI based reduction of GO prepared from graphite	[76]
	APTES/3DGS@MB, APTES/3DGS@Fc-COOH	(i) Redox tag (MB for CEA and Fc-COOH for AFP) modification by mixing and stirring; (ii) Treatment with APTES to get amino functionalized composites
CGN-Thi-anti-CEA, CGN-DAP-anti-PSA and CGN-Cd2+-anti-AFP	CGN	(i) Glucose carbonization in presence of sodium citrate, (ii) AuNPs deposition on carbon particles from HAuCl4 using microwave reaction	[75]
	Thi or DAP or Cd2+/CGN	Mixing Thi or DAP or Cd(NO3)2 with CGN and stirring for 5 h
M-Pt-Ab2	M-Pt	Ascorbic acid based reduction of K2PtCl4	[30]
Anti-CA72-4/PANi–Au AMNPs	PANi–Au AMNPs	Mix and incubate aniline in hexane with HAuCl4 aqueous solution at 45 °C overnight	[55]
Fe3O4@SiO2/Fc/GA/anti-CEA	Fe3O4@SiO2/Fc/GA/	(i) Fe3O4 via solvothermal method; (ii) Treatment with TEOS to obtain Fe3O4@SiO2; (iii) Treatment with APTES to get Fe3O4@SiO2–NH2; (iv) Treatment with EDC/NHS activated Fc-COOH followed by treatment with GA	[35]
Anti-SCCA/Pd–Au/C	Pd–Au/C	Mixing activated carbon, PdCl2, HAuCl4 and H2O-tetrahydrofuran via ultra-sonicating and stirring followed by treatment with NaBH4 and Na2CO3	[28]
Cu@Ag-CD/anti-CEA	Cu@Ag-CD	CD-ascorbic acid (pH 11) solution based sequential reduction of CuSO4·5H2O and AgNO3 solution in ammonia, followed by mixing and stirring with HS-β-CD overnight; Obtained Cu@Ag-CD was used for EDC/NHS based binding of Ab2 modified ADA-COOH	[37]
Fe3O4@C@Pd/anti-AFP	Fe3O4@C@Pd	(i) Fe3O4@C magnetic nanoparticles via hydrothermal process; (ii) Treatment with PDDA followed by mixing and incubation with PDNPs prepared via citrate and NaBH4 based reduction of Na2PdCl4	[33]
Anti-CA15-3/NP-PtFe	NP-PtFe	By removing Al using NaOH from ternary PtFeAl alloy with 80%Al	[31]
Anti-AFP/PdNi/N-GNRs	PdNi/N-GNRs	(i) N-GNRs powders via microwave-assisted treatment of N-MWCNTs, (ii) Mix N-GNRs with aqueous solution of Na2PdCl4, NiCl2·6H2O, and glutamate in ethylene glycol (EG), (pH 11) and stirring it for 2h followed by heating at 160 °C for 6 h in autoclave to get PdNi/N-GNRs	[39]
Pb2+@Au@MWCNTs-Fe3O4/anti-AFP	Pb2+@Au@MWCNTs-Fe3O4	(i) MWCNTs-Fe3O4 via autoclaving the mixture of acid treated MWCNTs, FeCl3.6H2O and sodium acetate, (ii) Amino-functionalization via APTES modification, (iii) Mixing and incubation with AuNPs prepared via citrate reduction; (iv) Treatment with lead nitrate solution 24 h to get Pb2+@Au@MWCNTs-Fe3O4	[49]
Au/Ag/Au@anti-SCCA	Au/Ag/Au	(i) Mix AuNPs, ascorbic acid, and AgNO3 in CTAB solution, (ii) Add NaOH dropwise with vigorous stirring to get yellow-golden colored, silver coated Au particles, (iii) Mix with HAuCl4 and ascorbic acid and stirred vigorously to obtain dark-blue Au/Ag/Au NPs solution	[41]
Anti-AFP/Pd/APTES-M-CeO2-GS	Pd/APTES-M-CeO2-GS	(i) The Pd octahedral NPs via sonicating followed by heating the mixture of 1-ethenyl-2-pyrrolidinone homopolymer (PVP), citric acid, and Na2PdCl4 dissolved in ethanol and water at 80 °C with stirring and refluxing for 3 h, (ii) M-CeO2-GS prepared by dissolving Ce(NO3)3·6H2O into water followed by adding C2H5COOH, ethylene glycol and GO and then treating at 180 °C for 200 min followed by cooling, centrifuging the ppt and drying at 50 °C for 12 h, (iii) APTES modification of M-CeO2-GS by refluxing, (iv) Pd binding by sonication and stirring to get Pd/APTES-M-CeO2-GS	[51]
Anti-SCC-Pt–Fe3O4	Pt–Fe3O4	(i) Mix platinum acetylacetonate, oleic acid, oleylamine and octadecane under argon atmosphere followed by heating to 120 °C, (ii) add Fe(CO)5 heat at 280 °C, 20 min, (iii) Precipitation using ethanol addition	[65]
Anti-AFP/Pt@CuO-MWCNTs	Pt@CuO-MWCNTs	(i) Acid treated MWCNTs mixed with Cu(CH3COO)2·H2O were grounded and calcinated at 350 °C in argon, followed by addition of NH4OH solution, (ii) MWCNTs addition followed by ageing and calcination to get CuO/MWCNTs composite, (iii) Pt loading by adding CuO/MWCNTs nanocomposites to K2PtCl4 solution followed by Pt salt reduction	[38]
M-Pd@Pt/NH2-GS/anti-PSA	NH2-GS	(i) Mix GO and ethylene glycol under ultrasonication followed by ammonia water addition, (ii) Autoclave for solvothermal reaction at 180 °C, 10 h	[78]
	M-Pd@Pt	(i) Mix Pluronic F127 with aqueous solution of K2PtCl4, Na2PdCl4 and hydrochloric, (ii) Reduction using ascorbic acid at 35 °C for 4 h
	M-Pd@Pt/NH2-GS	Mix and sonicate NH2-GS and M-Pd@Pt for 1 h
Ir NPs-anti-CEA	PVP stabilized Ir NPs	(i) Add aqueous IrCl3 solution dropwise to ethanol solution containing PVP followed by mixing and stirring at 25 °C for 12 h, (ii) Refluxed in air at 100 °C for 6 h followed by evaporation	[79]
PBG-Au-anti-CEA; PPP-Au-anti-NSE; PTBO-Auanti-CA125; PMCP-Au-anti-Cyfra21–1; Cd NCs-Auanti-SCCA	PBG-Au	Add and stir TTAB to brilliant green aqueous solution followed by HAuCl4 addition and agitation for 4 h, RT	[80]
	PPP-Au	Add water with stirring to DMF solution of N-phenyl-p-phenylenediamine followed by HAuCl4 addition and agitation for 4 h, RT
	PTBO-Au	Add HAuCl4 to toluidine blue o aqueous solution and agitate for about 4 h, RT
	PMCP-Au	Add and stir DTAB to m-cresol purple ethanol solution followed by HAuCl4 addition and agitation for 4 h, RT
	Cd NCs-Au	Mix Cd NCs with gold colloid and stirred for 4 h
HRP-anti-CYFRA21-1/AuNPs/Thi/MWCNT-NH2	AuNPs	HAuCl4 reduction using NaBH4 in Thi/MWCNT-NH2 solution	[84]
	MWCNT-NH2	Acid treatment of MWCNT to get MWCNT-COOH followed by treatment with HMDA in presence of DCC for 96 h at 120 °C
anti-AFP-Co3O4@MnO2-Thi	Co3O4@MnO2	Mixture of Co(CH3COO)2·4H2O and MnO2 nanotubes in ammonium hydroxide autoclaved at 150 °C, 5 h followed by calcination at 300 °C, 1 h	[85]
	Co3O4@MnO2-Thi	Co3O4@MnO2 treatment with APTES at 70 °C, 1.5 h followed by incubation with Thi at 95 °C, 1 h
	anti-AFP-Co3O4@MnO2-Thi	EDC/NHS chemistry
antiHER2/Hyd@AuNPs-APTMS-Fe3O4	antiHER2/Hyd@AuNPs-APTMS-Fe3O4	AuNPs preparation using HAuCl4 reduction via NaBH4, sodium citrate followed by treatment with APTMS-Fe3O4. Resulting AuNPs-APTMS-Fe3O4 were treated with thiolated anti-HER2 followed by treatment with hydrazine	[86]
Anti-CEA-AuNPs-Fc	AuNPs	Reduction of chloroauric acid with trisodium citrate	[87]
	Anti-CEA-AuNPs-Fc	Physical immobilization of anti-CEA on AuNPs followed by chemisorption of Fc-SH
HRP-anti-CEA-AuNPs-TiO2-graphene	TiO2-graphene	Sonicate graphene with dopamine for 1 h, followed by stirring with TiO2	[89]
	HRP-anti-CEA-AuNPs-TiO2-graphene	Treat TiO2-graphene with HAuCl4 under ultraviolet irradiation followed by physical adsorption of HRP-anti-CEA
PtCu@rGO/g-C3N4/anti-PSA	PtCu@rGO/g-C3N4/anti-PSA	Physical adsorption of anti-PSA on PtCu@rGO/g-C3N4	[90]
M-Pd@Pt/NH2-GS/anti-PSA	NH2-GS	GO prepared via modified Hummer’s method was mixed with ethylene glycol and ammonia followed by autoclaving at 180 °C for 10 h	[78]
	M-Pd@Pt	Pluronic F127 was mixed with K2PtCl4 and Na2PdCl4 in HCl followed by reducing with ascorbic acid
Anti-AFP-Pt NPs/Co3O4/graphene	Pt NPs/Co3O4/graphene	Mix GO and Co(NO3)2·6H2O in ethanol and add ammonia solution followed by autoclaving at 190 °C for 24 h. Obtained Co3O4/graphene was mixed with Na2PtCl4 in ethanol aqueous solution and treat with NaBH4	[91]
GS-Fe3O4/Au@Ag/Ni2+-anti-CEA	NH2-GS-Fe3O4	GO prepared via modified Hummer’s method was mixed with clear solution of FeCl3·6H2O in ethylene glycol along with NaAc and ethanediamine and autoclaved at 200 °C for 8 h. Resulting GS-Fe3O4 was treated with APTES to get NH2-GS-Fe3O4	[92]
	Au@Ag	AuNPs prepared via citrate reduction were mixed with ascorbic acid, AgNO3 and CTAB solution and treated with NaOH
	GS-Fe3O4/Au@Ag/Ni2+-anti-CEA	GS-Fe3O4/Au@Ag made by mixing NH2-GS-Fe3O4 and Au@Ag were dispersed in Ni(NO3)2·6H2O solution and stir for 24 h, anti CEA was immobilized via physical adsorption
Ag NPs-MWCNTs/MnO2-Anti-CEA	Ag NPs-MWCNTs/MnO2	Acid treated MWCNTs were dispersed in KMnO4 solution and treated with MnSO4. Obtained MWCNTs/MnO2 were mixed with AgNO3 in water followed by reduction NaBH4	[93]
PdCu-anti-CEA	PdCu	Using AA as reducing agent and HDPC as growth inhibitor	[95]
anti-AFP-GNPs-HRP	GNP	Citrate reduction	[96]
anti-AFP/HRP-Au@ZnO	Au@ZnO	C18N3 was added to mixture of Zn(NO3)2 and HAuCl4 and heated at 145 °C, 5 h	[97]
anti-PSA/AuNPs	AuNPs	Citrate reduction in cold for smaller size and in boiling condition for large size	[98]
Co3O4@CeO2-Au@Pt-anti-SCCA	Co3O4@CeO2	Co(NO3)2·6H2O solution was treated with NaOH at 180 °C, 5 h. Obtained Co3O4 cubes were mixed in ethanol aqueous solution followed by addition of Ce(NO3)3 and HMT and refluxing at 70 °C, 2 h	[99]
	Au@Pt	Citrate reduced AuNPs were mixed with H2PtCl6 under boiling conditions followed by reduction with AA
	Co3O4@CeO2-Au@Pt	APTES treated Co3O4@CeO2 were mixed with Au@Pt and stir for 12 h at room temperature.
Anti-AFP/Au@Ag/PDA-PR-MCS	PR-MCS	C6H5OH and HCHO were added to solution containing NH4OH and C2H5OH and autoclaved at 100 °C, 24 h. Product was mixed with KOH and treated at 350 °C, 1 h followed by at 700 °C, 2 h	[100]
	Au@Ag	Citrate reduced AuNPs were mixed with AgNO3 solution and treated with NaBH4 solution
	Au@Ag/PDA-PR-MCS	PR-MCS dispersed in tris buffer was treated with Dopamine hydrochloride 24 h and mixed with Au@Ag solution
MSN-MB/PDA-anti-PSA	MSN	Mixture of CTAB and pluronics F127 in ethanol, water and ammonia was treated with TEOS	[101]
	MSN-MB/PDA	MB loaded MSN was treated with dopamine in tris buffer, pH 8.5
Au@Pt DNs/NG/Cu2+-anti-CEA	NG	GO prepared via modified Hummer’s method was treated with ammonia solution at 90 °C, 4 h	[103]
	Au@Pt DNs	NaBH4 and AA reduced HAuCl4 and CTAB solution was mixed with K2PtCl4 and AA and treated at 60 °C, 12 h
Au@Ag-Cu2O/anti-PSA	Au@Ag-Cu2O	Citrate reduced AuNPs were mixed with CTAC and AgNO3 followed by reduction using AA at 30 °C, 2 h. Obtained Au@Ag solution was mixed with CuCl2 and SDS followed by treatment with NaOH and NH2OH·HCl	[104]

Notes: AA: ascorbic acid; Apo: apoferritin; Cd NCs-Au: Cd nanocubes-gold; CdNCs and CuNCs: Cd₃[Co(CN)₆]₂ and Cu₃[Co(CN)₆]₂ nanocubes; CTAB: hexadecyl trimethyl ammonium bromide; CTAC: cetyltrimethylammonium chloride; HDPC: hexadecylpyridinium chloride monohydrate; HMDA: hexamethylenediamine; HMT: hexamethylenetetramine; Ir NPs: iridium nanoparticles; M-Alg: metal alginate nanobeads; MCF: mesoporous carbon form; MCM-41: multifunctional mesoporous silica; M-Pd@Pt/NH2-GS: mesoporous core-shell Pd@Pt nanoparticles loaded by amino group functionalized graphene; M-Pt NPs: mesoporous platinum nanoparticles; MSNs: mesoporous silica nanoparticles; N-MWCNTs: N-doped multi-walled carbon nanotubes; PBG-Au: poly (brilliant green)-gold; PDDA: poly(diallyldimethylammonium chloride); PMCP-Au: poly (m-cresol purple)-gold; PPP-Au: poly (N-phenyl-p-phenylenediamine)-gold; PTBO-Au: poly (toluidine blue o)-gold; PtPNPs: platinum porous nanoparticles; PVP: polyvinylpyrrolidone; SDS: sodium dodecyl sulfate.