## 1 Introduction  
A general classification of kidney diseases could be its division into acute kidney injury (AKI) and chronic kidney diseases (CKD). AKI usually occurs when the serum creatinine level exceeds 0.3 mg/dL within 48 h or the urine volume is below 0.5 mL/k/h for 6 h, or serum creatinine surges up to more than 1.5 times baseline. Urinary obstruction, hypovolemia, and drug overdose are considered the main causes of AKI. The persistent abnormality (more than 3 months) in the structure and function of the kidney is defined as CKD and is commonly connected with primary glomerular diseases, diabetes, and hypertension. There are different definitions, causes, and therapeutical strategies. The global prevalence of CKD is more than 10%, mostly affecting the elderly [1]. Several adverse outcomes and clinical complications as well as individual and social-economic burdens affect CKD patients [2]. Therefore, the prevention and early diagnosis of CKD is an emerging public health issue. Whether the renal disease is localized within the glomeruli, tubules, vessels, intersititium, and/or cysts, the pathological classification of the disease must be determined. In a few groups of CKD patients, a renal biopsy might be required [3]. CKD is tightly connected with the elevated risk of vascular and early cardiovascular-related death. The current guideline categorizes CKD into five stages according to the glomerular filtration rate (GFR) level. However, the conventional techniques of GFR measuring are time-consuming, inconvenient, and might be inaccurate. Although radiolabeled approaches can result in accurate GFR evaluation, they are less practical [4]. Stage 1 CKD is considered as renal damage, but the GFR is normal (90) or increased. A mild plunge in GFR (60-89) is observed at stage 2. The GFR at stages 3 and 4 drops to 30-59 and 15-29, respectively. Finally, in stage 5, renal failure occurs and the GFR is below 15. All GFRs are demonstrated in mL/min/1.73 m\({}^{2}\)[4]. A calculation of the estimated GFR (eGFR) from serum creatinine according to a formula in relation to the characteristics of the patients has become an available and facilitated method of monitoring kidney damage. The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation now represents the finest way to precisely estimate GFR [4; 5]. Nanoparticles (NPs) are valuable matrix structures that can encapsulate proteins, drugs, imaging agents, and/or their combinations in a single nano-sized construction [6; 7; 8]. Nanotechnology is a rapidly progressing field with wide applications [9; 10]. Several medical applications have benefited from using NPs to deliver theranostic agents. In particular, NPs can overcome the physical and biological limitations of conventional therapies and thus provide new opportunities against the stability and solubility problems of many compounds. Rapid progress in nanotechnology through the development of several nanomaterials as diagnostic or therapeutic agents holds promise in treating several diseases [11; 12]. Sophisticated targeting tactics and multifunctionality are considered as unique properties of nanomedicine products. Nanoparticles as drug/gene delivery vehicles and contrast agents in imaging have been extensively used [13]. In this context, a wide range of organic, inorganic, polymeric, lipid, and glycan compounds have been successfully applied [14]. A broad body of evidence supports the capability of NPs in the diagnosis and treatment of CKD [15]. NPs have been applied in the measurement of renal morphology and function and targeted delivery of different therapeutics. However, few studies have been conducted on using NPs in CKD [16]. Novel techniques have been developed to generate electrostatic charges and thus turn NPs into hydrophobic structures, increasing sight-specific delivery. Additionally, different ligands can be conjugated to the surface of NPs to increase targeted therapy; this is seen in antibodies and peptides to reach specific cell receptors.