Table 3.

Summary of magnetic relaxivity (r₁), particle size (d_avg), specific properties and modalities of reported CAs.

S. No.	CAs	Magnetic Relaxivity (r1) (s−1·mM−1)	Particle Size (davg) (nm)	Specific Characteristics	Modality	Ref.
1	Gd–albumin conjugates	9~10.5	~5–6	Blood clearance half-lives = 40–47 min	T1 MRI	[110]
2	Gd–albumin-Folic acid conjugates	10.8	~201–215	Almost non-cytotoxic, good biocompatibility	T1 MRI	[111]
3	TAT-Gd-NPs	18.2	1.5	Good in vitro cell viability, non-toxic upto 20 μM Gd	T1 MRI	[112]
4	Cyclic RGD-conjugated Gd-NPs	10.0–18.7	1.0–2.5	Nontoxic up to 10 μM Gd	T1 MRI	[25]
5	PPy@BSA-Gd	10.203	50	Good cytocompatibility, Phototherma therapy	T1 MRI	[114]
6	D-glucuronic acid coated Gd-NPs	12.2	2.0	Highly water-dispersible and non-toxic	T1 MRI	[122]
7	Chitosan oligosaccharide lactate (COL)-Gd-NPs	13.0	1.9	Non-toxic up to 500 μM Gd	T1 MRI	[124]
8	Gd-NPs-polyacrylic acid (PAA)-rhodamine B (Rho)	22.6	1.5	High cell viabilities up to 500 μM Gd and good biocompatibility	T1 MRI-NCT-FI	[135]
9	PAAMA coated Gd-NPs	40.6	1.8	Exceptionally low cellular toxicity	T1 MRI	[136]
10	PMVEMA-coated Gd-NPs	36.2	1.9	Excellent colloidal stability in aqueous solution and appreciable biocompatibility	T1 MRI	[137]
11	PFTQ-PEG-Gd-NPs	10.95	95 ± 4.6	Low biotoxicity and outstanding chemical and optical stability	T1 MRI	[139]
12	Gd-NPs@SiO2-DO3A and Gd-NPs@SiO2-DO2A-benzothiazoles (BTA)	Gd@SiO2-DO3A = 5.47 Gd@SiO2-DO2A-BTA = 7.99	50–60	High water solubility and colloidal stability, anticancer characteristics	T1 MRI	[141]
13	Gd(DO3A-BTAA)(H2O) chelates	3.84	-	Tumour-specific, antiproliferative activities	T1 MRI	[142]
14	Gd-NPs@C	16.26	3.1	Cell viabilities up to 500 μM Gd, good biocompatibility	T1 MRI-FI	[143]
15	Gd-NPs/GO-NCs	34.48	2.89	Water dispersible with good biocompatibility	T1 MRI	[144]
16	Gd-PEG-GO-QDs	210.9 at 114 μT	4.0	Low biotoxicities	T1 MRI-FI	[146]
17	Gd(III)-loaded AuNPs-DEN modified with arginine-glycine-aspartic acid peptide Complex	13.17	-	Satisfactory cytocompatibility	T1 MRI-CT	[149]
18	Gd-dysprosium oxide nanoparticles (Gd-DONPs) D-glucuronic acid coated Gd-DONPs	6.0	1.0	Non-toxic up to 200 μM	T1, T2 MRI	[150]
19	D-glucuronic acid coated Zn(II)/Gd(III) oxide NPs	12.3	2.1	Slightly cytotoxic in DU145 cell lines, negligible cytotoxicity in NCTC1469 cell lines up to 200 M (Gd + Zn)	T1 MRI	[152]
20	LA coated Gd–europium oxide NPs	11.9	1.75	Non-toxic up to 279 mM Gd and Eu	T1,T2 MRI-FI	[153]
21	Gd compounds –NSAIDs chelates	5.0–7.0	-	Neuroprognostic	T1 MRI	[154]
22	Gd-chelate conjugated with Chal (Gd-DO3A-Chal	4.95	-	Aβ-targeting	MRI-FI	[155]
23	Fluorescein/FITC-Gd-NPs	Fluorescein-coated = 9.8 FITC-coated = 12.3	Fluorescein-coated = 1.6 FITC-coated = 1.4	Good cell viability up to 100 μM Gd	T1 MRI-FI	[158]