Table 1.

Promising nanoparticles for the diagnosis of CKD and DKD. A number of studies published within the last decade have shown promising pre-clinical results for the diagnosis of both DKD and CKD. Since both diseases show similar renal damage the use of NPs for therapeutic delivery have been interchangeably considered for both CKD and DKD within this table.

Class	Nanoparticle	Size (nm)	Model	Summary	Refs.
Gold	Anti-collagen-I antibody-conjugated AuNPs (bare or PEG-coated)	19 / 45	In vitro (collagen coated plate; murine kidney sections)	Co-I-AuNPs bind specifically to with increased retention to mouse fibrotic kidneys. They can then be detected by micro-CT.	[81]
	PEG-modified, highly stabilised core-satellite Au nano-assemblies with N-acetylation chitosan modification	Core: 18.7Satellite: 3.9	BALB/c mice	Fluorescence imaging indicates NACS-PEG-CSAuNAs effectively target renal tubular cells with greater retention than standard NACS-PEG-AuNPs.	[82]
	Renal clearable glutathione coated AuNPs	2.5	CD-1 mouse UUO model	Non-invasive x-ray imaging shows increased retention and cellular uptake in UUO kidneys, with anatomical localisation precisely correlated with local pathology. Contrast enhancement is 6x higher than using diatrizoate meglumine (a clinically used agent).	[83]
	Renal clearable luminescent glutathione coated AuNPs	< 5.5	Mouse UUO model	Fluorescence imaging using renal clearable near-infrared emitting AuNPs is a low cost, non-invasive measure of kidney dysfunction progression with greater contrast than small-molecule based contrast agents and greater sensitivity than typical blood markers.	[84]
Iron oxide	SPION-labelled MSCs	60	Ischaemic AKI in rabbitsCKD in Sprague-Dawley rats	SPIONs are an effective, non-toxic agent for targeted MRI when combined with the use of MSCs to treat renal injury and CKD.	[44,45]
	PEG-coated iron oxide NPs	20	BALB/cJRj mice	NPs accumulate in PTECs and generate clear negative contrast for renal MRI, with reduced RES retention and increased renal clearance.	[85]
	SPIONs	5.8		MPI is a new alternative to MRI which uses SPIONs. These are potentially a safer alternative to traditional contrast agents in CKD patients.	[[86], [87], [88]]
	Ferumoxytol	30	Licensed in humans for treatment of anaemia.Human case study.	Ferumoxytol is an effective novel MRI contrast agent with an excellent safety profile in CKD patients.	[89,[90], [91], [92]]