Specific Renal Uptake of Randomly 50% N-Acetylated Low Molecular Weight Chitosan

Efficient and selective kidney targeting by chemically modified carbohydrate conjugates

We investigated a renal tubule-targeting carbohydrate (RENTAC) that can selectively deliver small-molecule and nucleic acid analogs to the proximal convoluted tubules of the kidney following systemic delivery in mice. We comprehensively evaluated anti-miR-21-peptide nucleic acid-RENTAC, and fluorophore-RENTAC conjugates in cell culture and in vivo. We established that RENTAC conjugates showed megalin- and cubilin-dependent endocytic uptake in the immortalized kidney cell line. In vivo biodistribution studies confirmed the retention of RENTAC conjugates in the kidneys for several days compared with other organs. Immunofluorescence staining confirmed the selective distribution of the RENTAC conjugates in proximal convoluted tubules. We further demonstrated proximal convoluted tubule targeting features of RENTAC conjugates in a folic acid-induced kidney fibrosis mouse model. As a biological readout, we targeted miR-33 using antisense peptide nucleic acid (PNA) 33-RENTAC conjugates in the fibrotic kidney disease model. The targeted delivery of PNA 33-RENTAC resulted in slower fibrosis progression and decreased collagen deposition. We also confirmed that the RENTAC ligand did not exert any adverse reactions. Thus, we established that the RENTAC ligand can be used for broad clinical applications targeting the kidneys selectively.

Rediscovering the chemistry of the Cunninghamella species: potential fungi for metabolites and enzymes of biological, industrial, and environmental values

Endophytic fungi have a strong affinity for producing the same or comparable compounds to those produced by their hosts. Herein, genetic diversity and environmental adaptation of the Cunninghamella species were briefly investigated. The genetic flexibility in Cunninghamella represents an evolutionary mechanism that allows them to respond effectively to environmental changes. The current review paid much attention toward the phytochemical screening of Cunninghamella sp., revealing the presence of alkaloids, unsaturated sterols, fatty acids, polyphenols, and quinones. The intensive investigations clarified that Cunninghamella sp. are distinguished in producing several numbers of fatty acids, in particular polyunsaturated fatty acids (PUFA), in large quantities compared to other metabolites. The study demonstrated the effective role of Cunninghamella sp. in forming several bioactive metabolites owing to cytochrome P450 (CYP) that confirm significant value of such species for potential media biotransformation. The comparative investigations revealed that the isolation of flavonoids is yet to be reported, while the number of elucidated alkaloids and steroids is still limited. In contrast, successful results in the biotransformation of these metabolites were verified and showed a high affinity to convert simple substances to more valuable agents by Cunninghamella. The biomedical applications of naturally occurring compounds isolated from Cunninghamella were well documented; these included their antimicrobial, anti-cancer, anti-inflammatory, anti-Alzheimer, and antiaging properties. The antimicrobial activity was mostly attributed to the fatty acid contents in Cunninghamella sp. Moreover, tremendous attention was paid towards the agricultural and industrial usage of chitosan as it is one of the most crucial metabolites involved in wide applications. Chitosan is involved in food preservation for extending life storage period and utilized as biofertilizer, which enhances bacterial disease resistance. In addition, Cunninghamella is considered an important enzyme reservoir. Various Cunninghamella sp. produce several important enzymes, such as lignin peroxidase, catalase, cellulase, xylanase, laccase, and CYPs, that can be used for remediation, fertilization, preservation and medicinal purposes. Hence, further in-depth investigations are highly recommended to explore new insights into this potential reservoir of a wide spectrum of chemicals for industrial, medicinal, agricultural, and environmental applications.

Renal-Targeted Drug Delivery by Chitosan Oligosaccharide Micelles with HSA-Enriched Protein Corona for the Treatment of Ischemia/Reperfusion-Induced Acute Kidney Injury

Renal-specific nanoparticulate drug delivery systems have shown great potential in reducing systemic side effects and improving the safety and efficacy of treatments for renal diseases. Here, stearic acid-grafted chitosan oligosaccharide (COS-SA) was synthesized as a renal-targeted carrier due to the high affinity of the 2-glucosamine moiety on COS to the megalin receptor expressed on renal proximal tubular epithelial cells. Specifically, COS-SA/CLT micelles were prepared by encapsulating celastrol (CLT) with COS-SA, and different proportions of human serum albumin (HSA) were then adsorbed onto its surface to explore the interaction between the protein corona and cationic polymeric micelles. Our results showed that a multilayered protein corona, consisting of an inner "hard" corona and an outer "soft" corona, was formed on the surface of COS-SA/CLT@HSA8, which was beneficial in preventing its recognition and phagocytosis by macrophages. The formation of HSA protein corona on COS-SA/CLT micelles also increased its accumulation in the renal tubules. Furthermore, the electropositivity of COS-SA/CLT micelles affected the conformation of adsorbed proteins to various degrees. During the adsorption process, the protein corona on the surface of COS-SA/CLT@HSA1 was partially denatured. Overall, COS-SA/CLT and COS-SA/CLT@HSA micelles demonstrated sufficient safety with renal targeting potential, providing a viable strategy for the management of ischemia/reperfusion-induced acute kidney injury.

Chitosan-based oral nanoparticles as an efficient platform for kidney-targeted drug delivery in the treatment of renal fibrosis

There is increasingly keen interest in developing orally delivered targeted drugs, especially for diseases that require long-term medication. Hence, we manufactured nanoparticles derived from methoxypolyethylene glycol-chitosan (PCS) to enhance the oral delivery and kidney-targeted distribution of salvianolic acid B (SalB), a naturally occurring renoprotective and anti-fibrotic compound, as a model drug for the treatment of renal fibrosis. Orally administered SalB-loaded PCS nanoparticles (SalB-PCS-NPs) maintained good stability in the gastrointestinal environment, improved mucus-penetrating capacity, and enhanced transmembrane transport through a Caco-2 cell monolayer. The relative oral bioavailability of SalB-PCS-NPs to free SalB and SalB-loaded chitosan nanoparticles (SalB-CS-NPs) was 367.0 % and 206.2 %, respectively. The structural integrity of SalB-PCS-NPs after crossing the intestinal barrier was also validated by Förster resonance energy transfer (FRET) in vitro and in vivo. Fluorescein isothiocyanate (FITC)-labeled SalB-PCS-NPs showed higher kidney accumulation than free FITC and FITC-labeled SalB-CS-NPs (4.6-fold and 2.1-fold, respectively). Significant improvements in kidney function, extracellular matrix accumulation, and pathological changes were observed in a unilateral ureter obstruction mouse model of renal fibrosis after once daily oral treatment with SalB-PCS-NPs for 14 days. Thus, oral administration of SalB-PCS-NPs represents a promising new strategy for kidney-targeted drug delivery.

Illumination of Hydroxyl Radical in Kidney Injury and High-Throughput Screening of Natural Protectants Using a Fluorescent/Photoacoustic Probe

The hydroxyl radical (•OH) is shown to play a crucial role in the occurrence and progression of acute kidney injury (AKI). Therefore, the development of a robust •OH probe holds great promise for the early diagnosis of AKI, high-throughput screening (HTS) of natural protectants, and elucidating the molecular mechanism of intervention in AKI. Herein, the design and synthesis of an activatable fluorescent/photoacoustic (PA) probe (CDIA) for sensitive and selective imaging of •OH in AKI is reported. CDIA has near-infrared fluorescence/PA channels and fast activation kinetics, enabling the detection of the onset of •OH in an AKI model. The positive detection time of 12 h using this probe is superior to the 48-hour detection time for typical clinical assays, such as blood urea nitrogen and serum creatinine detection. Furthermore, a method is established using CDIA for HTS of natural •OH inhibitors from herbal medicines. Puerarin is screened out by activating the Sirt1/Nrf2/Keap1 signaling pathway to protect renal cells in AKI. Overall, this work provides a versatile and dual-mode tool for illuminating the •OH-related pathological process in AKI and screening additional compounds to prevent and treat AKI.

'Passive' nanoparticles for organ-selective systemic delivery: design, mechanism and perspective

Nanotechnology has shown tremendous success in the drug delivery field for more effective and safer therapy, and has recently enabled the clinical approval of RNA medicine, a new class of therapeutics. Various nanoparticle strategies have been developed to improve the systemic delivery of therapeutics, among which surface modification of targeting ligands on nanoparticles has been widely explored for 'active' delivery to a specific organ or diseased tissue. Meanwhile, compelling evidence has recently been reported that organ-selective targeting may also be achievable by systemic administration of nanoparticles without surface ligand modification. In this Review, we highlight this unique set of 'passive' nanoparticles and their compositions and mechanisms for organ-selective delivery. In particular, the lipid-based, polymer-based, and biomimetic nanoparticles with tropism to different specific organs after intravenous administration are summarized. The underlying mechanisms (e.g., protein corona and size effect) of these nanosystems for organ selectivity are also extensively discussed. We further provide perspectives on the opportunities and challenges in this exciting area of organ-selective systemic nanoparticle delivery.

Delivering drugs to tubular cells and organelles: the application of nanodrugs in acute kidney injury

Acute kidney injury (AKI) is a common clinical syndrome with limited treatment options and high mortality rates. Proximal tubular epithelial cells (PTECs) play a key role in AKI progression. Subcellular dysfunctions, including mitochondrial, nuclear, endoplasmic reticulum and lysosomal dysfunctions, are extensively studied in PTECs. These studies have led to the development of potential therapeutic drugs. However, clinical development of those drugs faces challenges such as low solubility, short circulation time and severe systemic side effects. Nanotechnology provides a promising solution by improving drug properties through nanocrystallization and enabling targeted delivery to specific sites. This review summarizes advancements and limitations of nanoparticle-based drug-delivery systems in targeting PTECs and subcellular organelles, particularly mitochondria, for AKI treatment.

Co-delivery of celastrol and lutein with pH sensitive nano micelles for treating acute kidney injury

To treat acute kidney injury with high efficiency and low toxicity, a novel nanoplatform was developed to remove excess reactive oxygen species (ROS). Lutein (LU) and celastrol (Cel) were loaded into low molecular weight chitosan (CS) to prepare Cel@LU-CA-CS nanomicelles. Renal tubular epithelial (HK-2) cell uptake experiments showed that the drugs could be internalized in renal tubular via the megalin receptor. In this study, the amide bond formed by the reaction of citraconic anhydride (CA) with an amino group of CS could be destroyed under acidic conditions. Therefore, the drugs were released in HK-2 cells due to the acidic environment of the lysosome. In vitro studies showed that the nanomicelles could reduce toxicity in non-target organs and enhance therapeutic efficacy in acute kidney injury (AKI). In addition, Cel@LU-CA-CS micelles had alleviated kidney oxidative stress disorder and stabilized the mitochondrial membrane potential quickly. Next, in vivo studies proved that Cel@LU-CA-CS micelles could inhibit the activation of the NF-κB p65 and p38 MAPK inflammatory signaling pathways. Therefore, the micelles further reduced the overexpression of related inflammatory factors. In conclusion, Cel@LU-CA-CS nanomicelles could treat AKI with high efficiency and low toxicity, and inhibit renal fibrosis.

Novel Drug Delivery Technologies and Targets for Renal Disease

The burden of acute and chronic kidney diseases to the health care system is exacerbated by the high mortality that this disease carries paired with the still limited availability of comprehensive therapies. A reason partially resides in the complexity of the kidney, with multiple potential target cell types and a complex structural environment that complicate strategies to protect and recover renal function after injury. Management of both acute and chronic renal disease, irrespective of the cause, are mainly focused on supportive treatments and renal replacement strategies when needed. Emerging preclinical evidence supports the feasibility of drug delivery technology for the kidney, and recent studies have contributed to building a robust catalog of peptides, proteins, nanoparticles, liposomes, extracellular vesicles, and other carriers that may be fused to therapeutic peptides, proteins, nucleic acids, or small molecule drugs. These fusions can display a precise renal uptake, an enhanced circulating time, and a directed intraorgan biodistribution while protecting their cargo to improve therapeutic efficacy. However, several hurdles that slow the transition towards clinical applications are still in the way, such as solubility, toxicity, and sub-optimal renal targeting. This review will discuss the feasibility and current limitations of drug delivery technologies for the treatment of renal disease, offering an update on their potential and the future directions of these promising strategies.

Kidney-Targeted Drug Delivery System Based on Metformin-Grafted Chitosan for Renal Fibrosis Therapy

Our previous study demonstrated that metformin plays an anti-fibrotic role in addition to its hypoglycemic effect. Worryingly, it often requires more than 5 times the hypoglycemic dose to achieve a satisfactory anti-fibrotic effect, which greatly increases the risk of systemic acidosis caused by metformin overdose. Low-molecular-weight chitosan (LMWC) has natural kidney-targeting properties and good biocompatibility and degradability. Thus, we synthesized a novel carrier metformin-grafted chitosan (CS-MET) based on an imine reaction between oxidized chitosan and metformin. Then, GFP was recruited to form GFP-loaded CS-MET nanoparticles (CS-MET/GFP NPs) with controllable particle size. We hypothesized that CS-MET/GFP NPs would enrich in the kidney and be absorbed by HK-2 cells via megalin-mediated endocytosis by intravenous injection, which may avoid systemic acidosis caused by metformin overdose. Subsequently, the nanoparticle ruptures and releases metformin to exert its anti-apoptotic, anti-inflammatory, and anti-fibrotic effects. Our results showed that CS-MET/GFP NPs have great transfection efficiency and could enter HK-2 cells mainly through megalin-mediated endocytosis. Compared to the free metformin, CS-MET/GFP NPs showed similar anti-apoptotic ability but better therapeutic effects on cellular inflammation and fibrosis in vitro. On the other hand, CS-MET/GFP NPs showed great kidney-targeting ability and superior anti-apoptotic, anti-inflammatory, and anti-fibrotic effects in vivo.

Effect of Different Molecular Weights of Chitosan on Formulation and Evaluation of Allopurinol-Loaded Nanoparticles for Kidney Targeting and in Management of Hyperuricemic Nephrolithiasis

Present research study was conducted to formulate kidney-targeted allopurinol (AO)-loaded chitosan nanoparticles (ANPs) for management of hyperuricemic related nephrolithiasis. Different molecular weights of chitosan were used for fabricating ANP formulation by adopting modified ionotropic gelation method. The prepared batches were than evaluated for particle size analysis, entrapment efficiency, transmission electron microscopy, X-ray diffraction, Differential Scanning Calorimetry, in vitro release and in vivo animal study. The in vivo study depicted that post 2 h of administration of different formulations and pure drug; ANPs prepared from low molecular weight chitosan showed maximum concentration of AO in kidney signifying successful kidney targeting of drug (25.92 fold) whereas no or very less amount of AO was seen in other animal groups. Effectiveness (p < 0.01) of formulation in management of hyperuricemia-associated nephrolithiasis was also evaluated via estimation of urine pH and serum and urine uric acid levels of mice. Further histological study was also performed on kidney samples which again affirmed these results. Present investigation demonstrated that ANPs prepared from low MW chitosan depicted maximum kidney-targeting ability that might be due to its specific uptake by the kidneys as well as its higher solubility than other two polymers, which results in enhanced release rate from the formulation and also offers an efficient strategy for the management of hyperuricemic nephrolithiasis.

Nano-Technological Approaches for Targeting Kidney Diseases With Focus on Diabetic Nephropathy: Recent Progress, and Future Perspectives

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease worldwide. With the rising prevalence of diabetes, the occurrence of DN is likely to hit pandemic proportions. The current treatment strategies employed for DN focus on the management of blood pressure, glycemia, and cholesterol while neglecting DN’s molecular progression mechanism. For many theranostic uses, nano-technological techniques have evolved in biomedical studies. Several nanotechnologically based theranostics have been devised that can be tagged with targeting moieties for both drug administration and/or imaging systems and are being studied to identify various clinical conditions. The molecular mechanisms involved in DN are discussed in this review to assist in understanding its onset and progression pattern. We have also discussed emerging strategies for establishing a nanomedicine-based platform for DN-targeted drug delivery to increase drug’s efficacy and safety, as well as their reported applications.

Detoxification strategies of triptolide based on drug combinations and targeted delivery methods

Tripterygium wilfordii Hook f. has a long history of use in Chinese medicine. Triptolide (TP), as its main pharmacological component, has been widely explored in various diseases, including systemic lupus erythematosus, rheumatoid arthritis and cancer. However, due to its poor water solubility, limited therapeutic range and multi-organ toxicity, TP's clinical application has been greatly hampered. To improve its clinical potential, many attenuated drug combinations have been developed based on its toxicity mechanism and targeted delivery systems aimed at its water-solubility and structure. This review, conducted a systematic review of TP detoxification strategies including drug combination detoxification strategies from metabolic and toxic mechanisms, as well as drug delivery detoxification strategies from the prodrug strategy and nanotechnology. Many detoxification strategies have demonstrated promising potential in vitro and in vivo due to previous extensive studies on TP. Therefore, summarizing and discussing TP detoxification strategies for clinical problems can serve as a reference for developing novel TP detoxification strategies, and provide opportunities for future clinical applications.

Role of Nanotechnology and Their Perspectives in the Treatment of Kidney Diseases

Nanoparticles (NPs) are differing in particle size, charge, shape, and compatibility of targeting ligands, which are linked to improved pharmacologic characteristics, targetability, and bioavailability. Researchers are now tasked with developing a solution for enhanced renal treatment that is free of side effects and delivers the medicine to the active spot. A growing number of nano-based medication delivery devices are being used to treat renal disorders. Kidney disease management and treatment are currently causing a substantial global burden. Renal problems are multistep processes involving the accumulation of a wide range of molecular and genetic alterations that have been related to a variety of kidney diseases. Renal filtration is a key channel for drug elimination in the kidney, as well as a burgeoning topic of nanomedicine. Although the use of nanotechnology in the treatment of renal illnesses is still in its early phases, it offers a lot of potentials. In this review, we summarized the properties of the kidney and characteristics of drug delivery systems, which affect a drug’s ability should focus on the kidney and highlight the possibilities, problems, and opportunities.

Preferential siRNA delivery to injured kidneys for combination treatment of acute kidney injury

Acute kidney injury (AKI) is characterized by a sudden loss of renal function and is associated with high morbidity and mortality. Tumor suppressor p53 and chemokine receptor CXCR4 were both implicated in the AKI pathology. Here, we report on the development and evaluation of polymeric CXCR4 antagonist (PCX) siRNA carrier for selective delivery to injured kidneys in AKI. Our results show that PCX/siRNA nanoparticles (polyplexes) provide protection against cisplatin injury to tubule cells in vitro when both CXCR4 and p53 are inhibited. The polyplexes selectively accumulate and are retained in the injured kidneys in cisplatin and bilateral ischemia reperfusion injury models of AKI. Treating AKI with the combined CXCR4 inhibition and p53 gene silencing with the PCX/sip53 polyplexes improves kidney function and decreases renal damage. Overall, our results suggest that the PCX/sip53 polyplexes have a significant potential to enhance renal accumulation in AKI and deliver therapeutic siRNA.

Oligochitosan Synthesized by Cunninghamella elegans, a Fungus from Caatinga (The Brazilian Savanna) Is a Better Antioxidant than Animal Chitosan

Animal chitosan (Chit-A) is gaining more acceptance in daily activities. It is used in a range of products from food supplements for weight loss to even raw materials for producing nanoparticles and hydrogel drug carriers; however, it has low antioxidant activity. Fungal oligochitosan (OChit-F) was identified as a potential substitute for Chit-A. Cunninghamella elegans is a fungus found in the Brazilian savanna (Caatinga) that produces OligoChit-F, which is a relatively poorly studied compound. In this study, 4 kDa OChit-F with a 76% deacetylation degree was extracted from C. elegans. OChit-F showed antioxidant activity similar to that of Chit-A in only one in vitro test (copper chelation) but exhibited higher activity than that of Chit-A in three other tests (reducing power, hydroxyl radical scavenging, and iron chelation). These results indicate that OChit-F is a better antioxidant than Chit-A. In addition, Chit-A significantly increased the formation of calcium oxalate crystals in vitro, particularly those of the monohydrate (COM) type; however, OChit-F had no effect on this process in vitro. In summary, OChit-F had higher antioxidant activity than Chit-A and did not induce the formation of CaOx crystals. Thus, OChit-F can be used as a Chit-A substitute in applications affected by oxidative stress.

Therapeutic and delivery strategies of phytoconstituents for renal fibrosis

Chronic kidney disease (CKD) is one of the most common diseases endangering human health and life. By 2030, 14 per 100,000 people may die from CKD. Renal fibrosis (RF) is an important intermediate link and the final pathological change during CKD progression to the terminal stage. Therefore, identifying safe and effective treatment methods for RF has become an important goal. In 2018, the World Health Organization introduced traditional Chinese medicine into its effective global medical program. Various phytoconstituents that affect the RF process have been extracted from different plants. Here, we review the potential therapeutic capabilities of active phytoconstituents in RF treatment and discuss how phytoconstituents can be structurally modified or combined with other ingredients to enhance efficiency and reduce toxicity. We also summarize phytoconstituent delivery strategies to overcome renal barriers and improve bioavailability and targeting.

Natural Glycan Derived Biomaterials for Inflammation Targeted Drug Delivery

Inflammation is closely related to a variety of fatal or chronic diseases. Hence, targeting inflammation provides an alternative approach to improve the therapeutic outcome of diseases such as solid tumors, neurological diseases, and metabolic diseases. Polysaccharides are natural components with immune regulation, anti-virus, anti-cancer, anti-inflammation, and anti-oxidation activities. Herein, this review highlights recent progress in the polysaccharide-based drug delivery systems for achieving inflammation targeting and its related disease treatment. Moreover, the chemical modification and the construction of polysaccharide materials for drug delivery are discussed in detail.

General sites of nanoparticle biodistribution as a novel opportunity for nanomedicine

The development of nanomedical devices has led to a considerable number of clinically applied nanotherapeutics. Yet, the overall poor translation of nanoparticular concepts into marketable systems has not met the initial expectations and led to increasing criticism in recent years. Most novel nano approaches thereby use highly refined formulations including a plethora of active targeting sequences, but ultimately fail to reach their target due to a generally high off-target deposition in organs such as the liver or kidney. In this context, we argue that initial nanoparticle (NP) development should not entirely become set on conventional formulation aspects. In contrast, we propose a change of focus towards a prior analysis of general sites of NP in vivo deposition and an assessment of how accumulation in these organs or tissues can be harnessed to develop therapies for site-related pathologies. We therefore give a comprehensive overview of existing nanotherapeutic targeting strategies for specific cell types within three of the usual suspects, i.e. the liver, kidney and the vascular system. We discuss the physiological surroundings and relevant pathologies of described tissues as well as the implications for NP-mediated drug delivery. Additionally, successful cell-selective NP concepts using active targeting strategies are assessed. By bringing together both (patho)physiological aspects and concepts for cell-selective NP formulations, we hope to show a novel opportunity for the development of more promising nanotherapeutic devices.

Glycol chitosan-based tacrolimus-loaded nanomicelle therapy ameliorates lupus nephritis

Background

Recently, we developed hydrophobically modified glycol chitosan (HGC) nanomicelles loaded with tacrolimus (TAC) (HGC-TAC) for the targeted renal delivery of TAC. Herein, we determined whether the administration of the HGC-TAC nanomicelles decreases kidney injury in a model of lupus nephritis. Lupus-prone female MRL/lpr mice were randomly assigned into three groups that received intravenous administration of either vehicle control, an equivalent dose of TAC, or HGC-TAC (0.5 mg/kg TAC) weekly for 8 weeks. Age-matched MRL/MpJ mice without Fas^lpr mutation were also treated with HGC vehicle and used as healthy controls.

Results

Weekly intravenous treatment with HGC-TAC significantly reduced genetically attributable lupus activity in lupus nephritis-positive mice. In addition, HGC-TAC treatment mitigated renal dysfunction, proteinuria, and histological injury, including glomerular proliferative lesions and tubulointerstitial infiltration. Furthermore, HGC-TAC treatment reduced renal inflammation and inflammatory gene expression and ameliorated increased apoptosis and glomerular fibrosis. Moreover, HGC-TAC administration regulated renal injury via the TGF-β1/MAPK/NF-κB signaling pathway. These renoprotective effects of HGC-TAC treatment were more potent in lupus mice compared to those of TAC treatment alone.

Conclusion

Our study indicates that weekly treatment with the HGC-TAC nanomicelles reduces kidney injury resulting from lupus nephritis by preventing inflammation, fibrosis, and apoptosis. This advantage of a new therapeutic modality using kidney-targeted HGC-TAC nanocarriers may improve drug adherence and provide treatment efficacy in lupus nephritis mice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00857-w.

Nanomedicine in the treatment of diabetic nephropathy

Globally, diabetic nephropathy (DN) is the foremost cause of end-stage renal disease. With the incidence of diabetes increasing day by day, DN's occurrence is expected to surge to pandemic proportions. Current available therapeutic interventions associated with DN emphasize blood pressure, glycemia and lipid control while ignoring DN's progression mechanism at a molecular level. This review sheds light on the molecular insights involved in DN to help understand the initiation and progression pattern. Further, we summarize novel strategies with reported applications in developing a nanomedicine-based platform for DN-targeted drug delivery to improve drug efficacy and safety.

Targeting Interstitial Myofibroblast-Expressed Integrin αvβ3 Alleviates Renal Fibrosis

Renal fibrosis is the final manifestation of various chronic kidney diseases. Interstitial myofibroblasts, which are reported to highly express integrin αvβ3, are the effector cells in renal fibrogenesis. Since current therapies do not efficiently target these cells, there is no effective therapeutic method for preventing or mitigating the disease. Here, we modified sterically stable PEGylated liposomes with the pentapeptide cRGDfC (RGD-Lip), which has a high affinity for αvβ3, to specifically deliver drug to renal interstitial myofibroblasts. Our results showed that attaching cRGDfC to liposomes significantly increased their uptake by activated renal fibroblasts NRK-49F cells, and this effect was greatly abolished by adding excess-free cRGDfC or a knockdown of αvβ3. Systemic administration of RGD-Lip gave rise to significant accumulation in a fibrotic kidney, which is ascribed to the specific recognition with integrin αvβ3 on interstitial myofibroblasts. When loaded with celastrol, RGD-guided liposomes dramatically depressed the proliferation and activation of NRK-49F cells in vitro. Additionally, celastrol-loaded RGD-Lip markedly attenuated renal fibrosis, injury, and inflammation induced by unilateral ureteral obstruction (UUO) in mice, without inducing significant systemic toxicity. Thus, this liposomal system shows great promise for delivering therapeutic agents to interstitial myofibroblasts for renal fibrosis treatment with minimal side effects.

Self-crosslinkable chitosan-hyaluronic acid dialdehyde nanoparticles for CD44-targeted siRNA delivery to treat bladder cancer

Bladder cancer is one of the concerning malignancies worldwide, which is lacking effective targeted therapy. Gene therapy is a potential approach for bladder cancer treatment. While, a safe and effective targeted gene delivery system is urgently needed for prompting the bladder cancer treatment in vivo. In this study, we confirmed that the bladder cancer had CD44 overexpression and small interfering RNAs (siRNA) with high interfere to Bcl2 oncogene were designed and screened. Then hyaluronic acid dialdehyde (HAD) was prepared in an ethanol-water mixture and covalently conjugated to the chitosan nanoparticles (CS-HAD NPs) to achieve CD44 targeted siRNA delivery. The in vitro and in vivo evaluations indicated that the siRNA-loaded CS-HAD NPs (siRNA@CS-HAD NPs) were approximately 100 nm in size, with improved stability, high siRNA encapsulation efficiency and low cytotoxicity. CS-HAD NPs could target to CD44 receptor and deliver the therapeutic siRNA into T24 bladder cancer cells through a ligand-receptor-mediated targeting mechanism and had a specific accumulation capacity in vivo to interfere the targeted oncogene Bcl2 in bladder cancer. Overall, a CD44 targeted gene delivery system based on natural macromolecules was developed for effective bladder cancer treatment, which could be more conducive to clinical application due to its simple preparation and high biological safety.

Engineering of stepwise-targeting chitosan oligosaccharide conjugate for the treatment of acute kidney injury

Acute kidney injury (AKI) is a common and serious clinical syndrome of acute renal dysfunction in a short period. One of therapeutic interventions for AKI is to reduce ROS massively generated in the mitochondria and then ameliorate cell damage and apoptosis induced by oxidative stress. In this study, stepwise-targeting chitosan oligosaccharide, triphenyl phosphine-low molecular weight chitosan-curcumin (TPP-LMWC-CUR, TLC), was constructed for sepsis-induced AKI via removing excessive ROS in renal tubular epithelial cells. Benefiting from good water solubility and low molecular weight, TLC was rapidly and preferentially distributed in the renal tissues and then specifically internalized by tubular epithelium cells via interaction between Megalin receptor and LMWC. The intracellular TLC could further delivery CUR to mitochondria due to high buffering capacity of LMWC and delocalized positive charges of TPP. Both in vitro and in vivo pharmacodynamic results demonstrated the enhanced therapeutic effect of TLC in the treatment of AKI.

Biomedical and Pharmacological Uses of Fluorescein Isothiocyanate Chitosan-Based Nanocarriers

Chitosan-based nanocarriers (ChNCs) are considered suitable drug carriers due to their ability to encapsulate a variety of drugs and cross biological barriers to deliver the cargo to their target site. Fluorescein isothiocyanate-labeled chitosan-based NCs (FITC@ChNCs) are used extensively in biomedical and pharmacological applications. The main advantage of using FITC@ChNCs consists of the ability to track their fate both intra and extracellularly. This journey is strictly dependent on the physico-chemical properties of the carrier and the cell types under investigation. Other applications make use of fluorescent ChNCs in cell labeling for the detection of disorders in vivo and controlling of living cells in situ. This review describes the use of FITC@ChNCs in the various applications with a focus on understanding their usefulness in labeled drug-delivery systems.

Transdermal Delivery of Kidney-Targeting Nanoparticles Using Dissolvable Microneedles

INTRODUCTION

Chronic kidney disease (CKD) affects approximately 13% of the world's population and will lead to dialysis or kidney transplantation. Unfortunately, clinically available drugs for CKD show limited efficacy and toxic extrarenal side effects. Hence, there is a need to develop targeted delivery systems with enhanced kidney specificity that can also be combined with a patient-compliant administration route for such patients that need extended treatment. Towards this goal, kidney-targeted nanoparticles administered through transdermal microneedles (KNP/MN) is explored in this study.

METHODS

A KNP/MN patch was developed by incorporating folate-conjugated micelle nanoparticles into polyvinyl alcohol MN patches. Rhodamine B (RhB) was encapsulated into KNP as a model drug and evaluated for biocompatibility and binding with human renal epithelial cells. For MN, skin penetration efficiency was assessed using a Parafilm model, and penetration was imaged via scanning electron microscopy. In vivo, KNP/MN patches were applied on the backs of C57BL/6 wild type mice and biodistribution, organ morphology, and kidney function assessed.

RESULTS

KNP showed high biocompatibility and folate-dependent binding in vitro, validating KNP's targeting to folate receptors in vitro. Upon transdermal administration in vivo, KNP/MN patches dissolved within 30 min. At varying time points up to 48 h post-KNP/MN administration, higher accumulation of KNP was found in kidneys compared with MN that consisted of the non-targeting, control-NP. Histological evaluation demonstrated no signs of tissue damage, and kidney function markers, serum blood urea nitrogen and urine creatinine, were found to be within normal ranges, indicating preservation of kidney health.

CONCLUSIONS

Our studies show potential of KNP/MN patches as a non-invasive, self-administrable platform to direct therapies to the kidneys.

Advances in kidney-targeted drug delivery systems

The management and treatment of kidney diseases currently have caused a huge global burden. Although the application of nanotechnology for the therapy of kidney diseases is still at an early stages, it has profound potential of development. More and more nano-based drug delivery systems provide novel solutions for the treatment of kidney diseases. This article summarizes the physiological and anatomical properties of the kidney and the biological and physicochemical characters of drug delivery systems, which affects the ability of drug to target the kidney, and highlights the prospects, opportunities, and challenges of nanotechnology in the therapy of kidney diseases.

Progress in drug delivery system for fibrosis therapy

Fibrosis is a necessary process in the progression of chronic disease to cirrhosis or even cancer, which is a serious disease threatening human health. Recent studies have shown that the early treatment of fibrosis is turning point and particularly important. Therefore, how to reverse fibrosis has become the focus and research hotspot in recent years. So far, the considerable progress has been made in the development of effective anti-fibrosis drugs and targeted drug delivery. Moreover, the existing research results will lay the foundation for more breakthrough delivery systems to achieve better anti-fibrosis effects. Herein, this review summaries anti-fibrosis delivery systems focused on three major organ fibrotic diseases such as liver, pulmonary, and renal fibrosis accompanied by the elaboration of relevant pathological mechanisms, which will provide inspiration and guidance for the design of fibrosis drugs and therapeutic systems in the future.

Effect of fluid shear stress on the internalization of kidney-targeted delivery systems in renal tubular epithelial cells

Renal tubular epithelial cells (RTECs) are important target cells for the development of kidney-targeted drug delivery systems. Under physiological conditions, RTECs are under constant fluid shear stress (FSS) from original urine in the renal tubule and respond to changes of FSS by altering their morphology and receptor expression patterns, which may affect reabsorption and cellular uptake. Using a microfluidic system, controlled shear stress was applied to proximal tubule epithelial cell line HK-2. Next, 2-glucosamine, bovine serum albumin, and albumin nanoparticles were selected as representative carriers to perform cell uptake studies in HK-2 cells using the microfluidic platform system with controlled FSS. FSS is proven to impact the morphology of HK-2 cells and upregulate the levels of megalin and clathrin, which then led to enhanced cellular uptake efficiencies of energy-driven carrier systems such as macromolecular and albumin nanoparticles in HK-2 cells. To further investigate the effects of FSS on endocytic behavior mediated by related receptors, a mice model of acute kidney injury with reduced fluid shear stress was established. Consistent with in vitro findings, in vivo studies have also shown reduced fluid shear stress down-regulated the levels of megalin receptors, thereby reducing the renal distribution of albumin nanoparticles.

A stimuli-responsive drug release nanoplatform for kidney-specific anti-fibrosis treatment

The renoprotective effects of hypoxia inducible-factor (HIF) activators have been demonstrated by improving renal hypoxia in chronic kidney disease. Cobalt chloride is one of the most widely used HIF activators in biomedicine; however, poor kidney targeting and undesirable side effects greatly limit its clinical applications. Here, we report a novel stimuli-responsive drug release nanoplatform in which glutathione (GSH)-modified Au nanoparticles (GLAuNPs) and Co2+ self-assemble into nanoassemblies (GLAuNPs-Co) through coordination interactions between empty orbitals of Co2+ and lone pairs of GSH. The GLAuNPs, when used as a drug carrier, demonstrated high drug loading capacity and pH-triggered drug release after assembling with Co2+. The acidic environment of lysosomes in renal fibrosis tissues could disassemble GLAuNPs-Co and release Co2+. Moreover, encapsulation of the Co2+ ions in the GLAuNPs greatly lowered the cytotoxicity of Co2+ in kidney tubule cells. Tissue fluorescence imaging showed that GLAuNPs-Co specifically accumulated in the kidneys, especially in the renal proximal tubules. After GLAuNPs-Co was intraperitoneally injected into ureter-obstructed mice, significant attenuation of interstitial fibrosis was exhibited. The beneficial effects can be mainly ascribed to miR-29c expression restored by HIF-α activation. These findings revealed that GLAuNPs-Co have pH-responsive drug release and renal targeting capabilities; thus, they are a promising drug delivery platform for treating kidney disease.

Crosstalk between chitosan and cell signaling pathways

The field of tissue engineering (TE) experiences its most exciting time in the current decade. Recent progresses in TE have made it able to translate into clinical applications. To regenerate damaged tissues, TE uses biomaterial scaffolds to prepare a suitable backbone for tissue regeneration. It is well proven that the cell-biomaterial crosstalk impacts tremendously on cell biological activities such as differentiation, proliferation, migration, and others. Clarification of exact biological effects and mechanisms of a certain material on various cell types promises to have a profound impact on clinical applications of TE. Chitosan (CS) is one of the most commonly used biomaterials with many promising characteristics such as biocompatibility, antibacterial activity, biodegradability, and others. In this review, we discuss crosstalk between CS and various cell types to provide a roadmap for more effective applications of this polymer for future uses in tissue engineering and regenerative medicine.

Bioformulative concepts on intracellular organ specific bioavailability

Bioavailability is an ancient but effective terminology by which the entire therapeutic efficacy of a drug directly or indirectly relays. Despite considering general plasma bioavailability, specific organ/tissue bioavailability will pave the path to broad spectrum dose calculation. Clear knowledge and calculative vision on bioavailability can improve the research and organ-targeting phenomenon. This article comprises a detailed introduction on bioavailability along with regulatory aspects, kinetic data and novel bioformulative approaches to achieve improved organ specific bioavailability, which may not be readily related to blood plasma bioavailability.

Small-Sized Cationic miRi-PCNPs Selectively Target the Kidneys for High-Efficiency Antifibrosis Treatment

Small-sized cationic miRi (microRNA-21 inhibitor)-PCNPs (low molecular weight chitosan (LMWC)-modified polylactide-co-glycoside (PLGA) nanoparticles (PLNPs)) with special kidney-targeting and high-efficiency antifibrosis treatment are fabricated through coupling miRi, PLGA, and LMWC. In the miRi-PCNPs, easily degraded miRi is encapsulated in PCNPs and thus prevented from degradation by nuclease. Cytotoxicity, immunotoxicity, and systemic toxicity assays and in vitro and ex vivo fluorescence imaging suggest that PCNPs possess excellent biocompatibility, higher cellular uptake efficiency, and selective kidney-targeting capacity. Western blotting, pathological staining, and real-time polymerase chain reaction analyses show that the therapeutic effect of miRi-PCNPs on kidney fibrosis is much higher than that of miRi, which is mainly through suppressing transforming growth factor beta-1/drosophila mothers against decapentaplegic protein 3 (TGF-β1/Smad3) and extracellular signal-regulated kinases/mitogen-activated protein kinase signaling pathway by inhibiting the expression of microRNA-21. For example, the tubule damage index and tubulointerstitial fibrosis area in the miRi-PCNPs group are ≈2.5-fold lower than those in the saline and bare miRi groups. The miRi-PCNPs with special kidney-targeting and high-efficiency antifibrosis treatment may represent a promising strategy for designing and developing a therapeutic treatment for kidney fibrosis.

Coordination-driven assembly of catechol-modified chitosan for the kidney-specific delivery of salvianolic acid B to treat renal fibrosis

Kidney-specific delivery is critically important for the treatment of renal fibrosis with drugs such as salvianolic acid B (Sal B). Here we report a kidney-specific nanocomplex formed by the coordination-driven assembly of catechol-modified low molecular weight chitosan (HCA-Chi), calcium ions and Sal B. The prepared HCA-Chi-Ca-Sal B (HChi-Ca-Sal B) nanocomplex reversed the TGF-β1-induced epithelial-mesenchymal transition (EMT) in HK-2 cells. In vivo imaging demonstrated a kidney-specific biodistribution of the nanocomplex. The anti-fibrosis effect of HChi-Ca-Sal B was tested in a mouse model of unilateral ureteral obstruction (UUO). Significant attenuation of the morphological lesions and the levels of extracellular matrix (ECM) proteins in the tubulointerstitium was observed in mice treated with HChi-Ca-Sal B, suggesting that the nanocomplex was able to prevent fibrosis better than the treatment with free Sal B. It was concluded that the HChi-Ca-Sal B nanocomplex showed a specific renal targeting capacity and could be utilized to enhance Sal B delivery for treating renal fibrosis.

Targeting renal fibrosis: Mechanisms and drug delivery systems

Renal fibrosis is the common outcome of many chronic kidney diseases (CKD) independent of the underlying etiology. Despite a host of promising experimental data, currently available strategies only ameliorate or delay the progression of CKD but do not reverse fibrosis. One of the major impediments of translating novel antifibrotic strategies from bench to bedside is due to the intricacies of the drug delivery process. In this review, we briefly describe mechanisms of renal fibrosis and methods of drug transfer into the kidney. Various tools used in gene therapy to administer nucleic acids in vivo are discussed. Furthermore, we review the modes of action of protein- or peptide-based drugs with target-specific antibodies and cytokines incorporated in hydrogels. Additionally, we assess an intriguing new method to deliver drugs specifically to tubular epithelial cells via conjugation with ligands binding to the megalin receptor. Finally, plant-derived compounds with antifibrotic properties are also summarized.

Highly Stabilized Core-Satellite Gold Nanoassemblies in Vivo: DNA-Directed Self-Assembly, PEG Modification and Cell Imaging

Au nanoparticles (NPs) have important applications in bioimaging, clinical diagnosis and even therapy due to its water-solubility, easy modification and drug-loaded capability, however, easy aggregation of Au NPs in normal saline and serum greatly limits its applications. In this work, highly stabilized core-satellite Au nanoassemblies (CSAuNAs) were constructed by a hierarchical DNA-directed self-assembly strategy, in which satellite Au NPs number could be effectively tuned through varying the ratios of core-AuNPs-ssDNA and satellite-AuNPs-ssDNAc. It was especially interesting that PEG-functionalized CSAuNAs (PEG-CSAuNAs) could not only bear saline solution but also resist the enzymatic degradation in fetal calf serum. Moreover, cell targeting and imaging indicated that the PEG-CSAuNAs had promising biotargeting and bioimaging capability. Finally, fluorescence imaging in vivo revealed that PEG-CSAuNAs modified with N-acetylation chitosan (CSNA) could be selectively accumulate in the kidneys with satisfactory renal retention capability. Therefore, the highly stabilized PEG-CSAuNAs open a new avenue for its applications in vivo.

Renal-targeted delivery of triptolide by entrapment in pegylated TRX-20-modified liposomes

Previously, 3,5-dipentadecyloxybenzamidine hydrochloride (TRX-20)-modified liposomes were reported to specifically target mesangial cells (MCs) in glomeruli. To further gain a better understanding of the characteristics and potential application for glomerular diseases of TRX-20-modified liposomes, we synthesized TRX-20 and prepared TRX-20-modified liposomes (TRX-LPs) with different molar ratios - 6% (6%-TRX-LP), 11% (11%-TRX-LP), and 14% (14%-TRX-LP) - of TRX-20 to total lipid in the present study. All TRX-LPs exhibited concentration-dependent toxicity against the MCs at a lipid concentration ranging from 0.01 to 1.0 mg/mL with IC50 values of 3.45, 1.13, and 0.55 mg/mL, respectively. Comparison of the cell viability of TRX-LPs indicated that high levels of TRX-20 caused severe cell mortality, with 11%-TRX-LP showing the higher cytoplasmic accumulation in the MCs. Triptolide (TP) as a model drug was first loaded into 11%-TRX-LP and the liposomes were further modified with PEG5000 (PEG-TRX-TP-LP) in an attempt to prolong their circulation in blood and enhance TP-mediated immune suppression. Due to specific binding to MCs, PEG-TRX-TP-LP undoubtedly showed better anti-inflammatory action in vitro, evidenced by the inhibition of release of nitric oxide (NO) and tumor necrosis factor-α from lipopolysaccharide-stimulated MCs, compared with free TP at the same dose. In vivo, the PEG-TRX-TP-LP effectively attenuated the symptoms of membranous nephropathic (MN) rats and improved biochemical markers including proteinuria, serum cholesterol, and albumin. Therefore, it can be concluded that the TRX-modified liposome is an effective platform to target the delivery of TP to glomeruli for the treatment of MN.

Inhibition of Glomerular Mesangial Cell Proliferation by siPDGF-B- and siPDGFR-β-Containing Chitosan Nanoplexes

Mesangioproliferative glomerulonephritis is a disease that has a high incidence in humans. In this disease, the proliferation of glomerular mesangial cells and the production of extracellular matrix are important. In recent years, the RNAi technology has been widely used in the treatment of various diseases due to its capability to inhibit the gene expression with high specificity and targeting. The objective of this study was to decrease mesangial cell proliferation by knocking down PDGF-B and its receptor, PDGFR-β. To be able to use small interfering RNAs (siRNAs) in the treatment of this disease successfully, it is necessary to develop appropriate delivery systems. Chitosan, which is a biopolymer, is used as a siRNA delivery system in kidney drug targeting. In order to deliver siRNA molecules targeted at PDGF-B and PDGFR-β, chitosan/siRNA nanoplexes were prepared. The in vitro characterization, transfection studies, and knockdown efficiencies were studied in immortalized and primary rat mesangial cells. In addition, the effects of chitosan nanoplexes on mesangial cell proliferation and migration were investigated. After in vitro transfection, the PDGF-B and PDGFR-β gene silencing efficiencies of PDGF-B and PDGFR-β targeting siRNA-containing chitosan nanoplexes were 74 and 71% in immortalized rat mesangial cells and 66 and 62% in primary rat mesangial cells, respectively. siPDGF-B- and siPDGFR-β-containing nanoplexes indicated a significant decrease in mesangial cell migration and proliferation. These results suggested that mesangial cell proliferation may be inhibited by silencing of the PDGF-B signaling pathway. Gene silencing approaches with chitosan-based gene delivery systems have promise for the efficient treatment of renal disease.

Renal-targeting triptolide-glucosamine conjugate exhibits lower toxicity and superior efficacy in attenuation of ischemia/reperfusion renal injury in rats

AIM

We previously reported a novel triptolide (TP)-glucosamine conjugate (TPG) that specifically accumulated in kidneys and protected renal function from acute ischemia/reperfusion (I/R) injury in rats. In this study we further examined the molecular mechanisms underlying the renoprotective action of TPG.

METHODS

The renal-targeting of TPG was investigated in a human proximal renal tubular epithelial cell line (HK-2) by measuring cell uptake of TP or TPG. The effects of TP or TPG on cell cycle distribution and apoptosis rate of HK-2 cells were assessed, and the activities of caspase-3 and caspase-9 were also measured. SD rats were subjected to bilateral renal ischemia by temporarily clamping both renal pedicles. The rats were administered TP (4.17 μmol·kg-1·d-1, iv) or TPG (4.17 μmol·kg-1·d-1, iv) for 3 d before the renal surgery. The kidneys were harvested after 24 h of recovery from the surgery. The levels of oxidative stress, proinflammatory cytokines, chemotactic cytokines and intracellular adhesion molecules in kidneys were examined.

RESULTS

The uptake of TPG in HK-2 cells was 2-3 times higher than that of TP at the concentrations tested. Furthermore, TPG targeting the proximal tubules was mediated through interactions with megalin receptors. TP (40-160 nmol/L) concentration-dependently increased G2/M arrest, apoptosis and caspase-3/caspase-9 activity in HK-2 cells, whereas the same concentrations of TPG did not show those features when compared with the control group. In I/R-treated rats, TPG administration caused more robust down-regulation of proinflammatory cytokines (TNF-α, IL-6, IL-1, TGF-β) and chemotactic cytokines (MCP-1) in the kidneys compared with TP administration, suggesting the inhibition of the proliferation and accumulation of lymphocytes. And TPG administration also caused more prominent inhibition on the levels of oxidative stress and intracellular adhesion molecules in the kidneys, compared with TP administration.

CONCLUSION

The renal-targeting TPG is more effective and less toxic than TP, in amelioration of I/R-induced rat renal injury, which may provide a new avenue for the treatment of acute kidney injury.

Nanomedicines for renal disease: current status and future applications

Treatment and management of kidney disease currently presents an enormous global burden, and the application of nanotechnology principles to renal disease therapy, although still at an early stage, has profound transformative potential. The increasing translation of nanomedicines to the clinic, alongside research efforts in tissue regeneration and organ-on-a-chip investigations, are likely to provide novel solutions to treat kidney diseases. Our understanding of renal anatomy and of how the biological and physico-chemical properties of nanomedicines (the combination of a nanocarrier and a drug) influence their interactions with renal tissues has improved dramatically. Tailoring of nanomedicines in terms of kidney retention and binding to key membranes and cell populations associated with renal diseases is now possible and greatly enhances their localization, tolerability, and efficacy. This Review outlines nanomedicine characteristics central to improved targeting of renal cells and highlights the prospects, challenges, and opportunities of nanotechnology-mediated therapies for renal diseases.