Poly-γ-glutamic acid coating polymeric nanoparticles enhance renal drug distribution and cellular uptake for diabetic nephropathy therapy.

Poor drug distribution and inefficient renal cellular uptake are the major barriers diminishing the efficacy of nanoparticles in renal targeted therapy. We designed the rhein (RH)-loaded poly-γ-glutamic acid (PGA)-coated polycaprolactone-polyethyleneimine nanoparticles (RGPP) to enhance renal drug distribution and cellular uptake via PGA-mediated receptor-ligand interaction with γ-glutamyltranspeptidase (GGT) expressed highly in the kidney. PGA coating not only ensured the stability, sustained drug release, and biocompatibility of RGPP, but also promoted renal cellular uptake via binding with the GGT on the renal cells. Following intravenous administration, PGA coating protects RGPP from recognition by the reticuloendothelial system, resulting in prolonged blood circulation. RGPP enables targeted RH accumulation in the kidneys of streptozotocin-induced diabetic nephropathy (DN) mice, resulting in significant recovery of renal physiological function. The PGA coating strategy opens a new avenue for the management of renal diseases using nanomedicine.

Kidney-targeted drug delivery via rhein-loaded polyethyleneglycol-co-polycaprolactone-co-polyethylenimine nanoparticles for diabetic nephropathy therapy.

INTRODUCTION: Diabetic nephropathy (DN) is the primary root of morbidity and mortality in diabetic patients. Unfortunately, currently, no effective therapeutic strategies are available to ameliorate and reverse the progression of DN. Rhein (RH) is an anthraquinone derivative extracted from herbal medicines with various pharmacological effects on DN. However, its clinical administration is limited by its poor solubility, low bioavailability, reduced distribution into the kidney and adverse effects. METHODS AND RESULTS: To improve the delivery of RH into kidney and the therapeutic effect on DN, we synthesized and utilized polyethyleneglycol-co-polycaprolactone-co-polyethylenimine triblock amphiphilic polymers to prepare RH-loaded polyethyleneglycol-co-polycaprolactone-co-polyethylenimine nanoparticles (PPP-RH-NPs). PPP-RH-NP size was optimized to 75 ± 25 nm for kidney-targeted drug delivery; the positive zeta potential allowed an effective cellular uptake and the polyethylenimine amine groups facilitate the endosomal escape quickly. The distribution and pharmacodynamics of PPP-RH-NPs were studied in a streptozocin-induced DN model, which explicitly demonstrated kidney-targeted distribution and improved the therapeutic effects of RH on DN by ameliorating several pathological indicators. CONCLUSION: Therefore, this study not only stimulates further clinical research on RH but also, more importantly, proposes a promising DN therapy consisting of an effective kidney-targeted drug delivery.

[Preparation and in vitro evaluation of rhein-loaded PEG-PCL-PEI nanoparticles].

This study was aimed to synthesize the polyethyleneglycol-polycaprolactone-polyethyleneimine (PEG-PCL-PEI) three block polymer material, prepareRhein (RH)-loaded PEG-PCL-PEI nanoparticles(PPP-RH-NPS), and then evaluate their physical and chemical properties and biological characteristics in vitro. PEG-PCL-PEI polymer was obtained by adopting thering-opening polymerization and Michael addition reaction, and their physical and chemical properties were analyzed by using NMR and gel permeation chromatography. PEG-PCL-PEI was then used as the carriers to prepare PPP-RH-NPS by applying spontaneous emulsification solvent diffusion method. The results showed that molecular weight of PEG-PCL-PEI polymer was 9.5×103, and critical micelle concentration was 0.723 mmol•L⁻¹. PPP-RH-NPS had pale yellow, opalescence faade, round and smooth without aggregation, formed of (118.3±3.6) nm in particle size with PDI of (0.19±0.08), Zeta potential of (6.3±1.5) mV, entrapment efficiency of (93.64±5.28)%, and drug loading of (8.57±0.53)%. The accumulative release percentage of PPP-RH-NPS was 75.92% in 48h, and the release profiles in PBS conformed to the Higuchi equation： Q=0.121 6t1/2+0.069 5 (R²=0.887 4), presenting slow release characteristics. Within the scope of the 0-0.05 mmol•L⁻¹, the nanoparticles had no obvious hemolysis on rabbit red blood cells and toxicity on HK-2 cells. In the investigation of uptake efficiency by flow cytometry, nanoparticles can be absorbed into cells quickly and internalized within 30 minutes fully, with a high uptake efficiency. In confocal laser scanning microscope observation, the nanoparticles can escape from lysosome into cytoplasm. Herein, this study synthesized the PEG-PCL-PEI polymer and prepared PPP-RH-NPS successfully; the nanoparticles showed uniform particle size, higher encapsulation efficiency and drug-loading rate, slow release characteristics, quick uptake and internalization, lysosome escape property and good biocompatibility. PPP-RH-NPS will be a promising pharmaceutical formulation for further development.

[Determination of trace arsenic in Chinese traditional medicine by hydride generation atomic fluorescence spectrometry].

A hydride generation atomic fluorescence spectrometry method was developed for the determination of trace arsenic in CTM. A digestion system using HNO3-H2O2 under high pressure was applied for the pretreatment of the samples. The experimental conditions were optimized. Under the optimum conditions, there was a good linear relationship between the fluorescence intensity and arsenic concentration in the range of 0-80 microg x L(-1) with a correlation coefficient of 0.9999, while the detection limit was 0.069 microg x L(-1). Trace arsenic in the standard reference substance (GBW08501) was determined incording this way and the results for six times of analysis were in good agreement with certified value. The authors also studied the arsenic contents in three kinds of CTM by the working curve method and the results were satisfactory.

[Determintion of trace lead in the traditional Chinese medicine using hydride generation atomic fluorescence spectrometry].

A hydride generation atomic fluorescence spectrometry method has been developed for the determination of trace lead in traditional Chinese medicines. A high pressure digestion using HNO3-H2O2 system was applied for the pretreatment of traditional Chinese medicine samples and the interval flow precedure was used. The experimental conditions and instrumental operating parameters such as KBH4 concentration, flow rates of carrier and shield gases, current of the lamp and height of the atomizer, have been optimized. Under the optimum conditions the detection limit is 0.08 microg x L(-1). The relative standard deviation is 0.34%. This method is simple, rapid and sensitive, so it can be successfully used for the determination of lead in traditional Chinese medicines.

[Determination of trace mercury in the Chinese traditional medicine by hydride generation-atomic fluorescence spectrometry].

A hydride generation atomic fluorescence spectrometry method has been developed for the determination of trace mercury in traditional Chinese medicines. A high-pressure digestion using HNO3-H2O2 system was applied to the pretreatment of traditional Chinese medicine samples and an interval flow precedure was used. The experimental conditions and instrumental operation parameters such as KBH4 concentration, flow rates of carrier and shield gases, currents of lamp and height of atomic oven, which affect the determination, have been optimized respectively as 0.05%, 400 and 800 mL x min(-1), 20 mA and 6 mm. Under the optimum conditions, there is a linear relationship between the fluorescence intensity and the mercury concentration with correlation coefficient of 0.9999, while the detection limit is 0.021 microg x L(-1). Trace mercury in the standard reference substance peach leaf (GBW08501, produced by the Environmental Science Committee of Chinese Scientific Institute) was also determinated in this way and the results of six times were in good agreement with the certified value, with a variation coefficient not more than 0.34%. This method is simple, rapid, sensitive, convinent and accurate, so it can be successfully used for the determination of trace mercury in traditional Chinese medi-