The endocytosis and intracellular fate of nanomedicines: Implication for rational design

AbstractNanomedicines employ multiple endocytic pathways to enter cells. Their following fate is interesting, but it is not sufficient understood currently. This review introduces the endocytic pathways, presents new technologies to confirm the specific endocytic pathways and discusses factors for pathway selection. In addition, some intriguing implication about nanomedicine design based on endocytosis will also be discussed at the end. This review may provide new thoughts for the design of novel multifunctional nanomedicines

Transporter-Guided Delivery of Nanoparticles to Improve Drug Permeation across Cellular Barriers and Drug Exposure to Selective Cell Types

Targeted nano-drug delivery systems conjugated with specific ligands to target selective cell-surface receptors or transporters could enhance the efficacy of drug delivery and therapy. Transporters are expressed differentially on the cell-surface of different cell types, and also specific transporters are expressed at higher than normal levels in selective cell types under pathological conditions. They also play a key role in intestinal absorption, delivery via non-oral routes (e.g., pulmonary route and nasal route), and transfer across biological barriers (e.g., blood–brain barrier and blood–retinal barrier. As such, the cell-surface transporters represent ideal targets for nano-drug delivery systems to facilitate drug delivery to selective cell types under normal or pathological conditions and also to avoid off-target adverse side effects of the drugs. There is increasing evidence in recent years supporting the utility of cell-surface transporters in the field of nano-drug delivery to increase oral bioavailability, to improve transfer across the blood–brain barrier, and to enhance delivery of therapeutics in a cell-type selective manner in disease states. Here we provide a comprehensive review of recent advancements in this interesting and important area. We also highlight certain key aspects that need to be taken into account for optimal development of transporter-assisted nano-drug delivery systems

Development of a Supercritical Fluid Chromatography-Tandem Mass Spectrometry Method for the Determination of Azacitidine in Rat Plasma and Its Application to a Bioavailability Study

Azacitidine is widely used for the treatment of myelodysplastic syndromes (MDS) and acute myelogenous leukaemia (AML). The analysis of azacitidine in biological samples is subject to interference by endogenous compounds. Previously reported high-performance liquid chromatography/tandem mass spectrometric (HPLC-MS/MS) bioanalytical assays for azacitidine suffer from expensive sample preparation procedures or from long separation times to achieve the required selectivity. Herein, supercritical fluid chromatography with tandem mass spectrometry (SFC-MS/MS) was explored as a more promising technique for the selective analysis of structure-like or chiral drugs in biological matrices. In this study, a simple, rapid and specific SFC/MS/MS analytical method was developed for the determination of azacitidine levels in rat plasma. Azacitidine was completely separated from the endogenous compounds on an ACQUITY UPLC™ BEH C18 column (100 mm × 3.0 mm, 1.7 μm; Waters Corp., Milford, MA, USA) using isocratic elution with CO2/methanol as the mobile phase. The single-run analysis time was as short as 3.5 min. The sample preparation for protein removal was accomplished using a simple methanol precipitation method. The lower limit of quantification (LLOQ) of azacitidine was 20 ng/mL. The intra-day and inter-day precisions were less than 15%, and the relative error (RE) was within ±15% for the medium- and high-concentration quality control (QC) samples and within ±20% for the low-concentration QC samples. Finally, the developed method was successfully applied to a pharmacokinetic study in rats following the intravenous administration of azacitidine

OCTN2-targeted nanoparticles for oral delivery of paclitaxel: differential impact of the polyethylene glycol linker size on drug delivery in vitro, in situ, and in vivo

Targeted nanocarriers have shown great promise in drug delivery because of optimized drug behavior and improved therapeutic efficacy. How to improve the targeting efficiency of nanocarriers for the maximum possible drug delivery is a critical issue. Here we developed L-carnitine-conjugated nanoparticles targeting the carnitine transporter OCTN2 on enterocytes for improved oral absorption. As a variable, we introduced various lengths of the polyethylene glycol linker (0, 500, 1000, and 2000) between the nanoparticle surface and the ligand (CNP, C5NP, C10NP and C20NP) to improve the ligand flexibility, and consequently for more efficient interaction with the transporter, to enhance the oral delivery of the cargo load into cells. An increased absorption was observed in cellular uptake in vitro and in intestinal perfusion assay in situ when the polyethylene glycol was introduced to link L-carnitine to the nanoparticles; the highest absorption was achieved with C10NP. In contrast, the linker decreased the absorption efficiency in vivo. As the presence or absence of the mucus layer was the primary difference between in vitro/in situ versus in vivo, the presence of this layer was the likely reason for this differential effect. In summary, the size of the polyethylene glycol linker improved the absorption in vitro and in situ, but interfered with the absorption in vivo. Even though this strategy of increasing the ligand flexibility with the variable size of the polyethylene glycol failed to increase oral absorption in vivo, this approach is likely to be useful for enhanced cellular uptake following intravenous administration of the nanocarriers

Drug discovery and formulation development for acute pancreatitis

Acute pancreatitis is a sudden inflammation and only last for a short time, but might lead to a life-threatening emergency. Traditional drug therapy is an essential supportive method for acute pancreatitis treatment, yet, failed to achieve satisfactory therapeutic outcomes. To date, it is still challenging to develop therapeutic medicine to redress the intricate microenvironment promptly in the inflamed pancreas, and more importantly, avoid multi-organ failure. The understanding of the acute pancreatitis, including the causes, mechanism, and severity judgment, could help the scientists bring up more effective intervention and treatment strategies. New formulation approaches have been investigated to precisely deliver therapeutics to inflammatory lesions in the pancreas, and some even could directly attenuate the pancreatic damages. In this review, we will briefly introduce the involved pathogenesis and underlying mechanisms of acute pancreatitis, as well as the traditional Chinese medicine and the new drug option. Most of all, we will summarize the drug delivery strategies to reduce inflammation and potentially prevent the further development of pancreatitis, with an emphasis on the bifunctional nanoparticles that act as both drug delivery carriers and therapeutics

Transporter-Targeted Nano-Sized Vehicles for Enhanced and Site-Specific Drug Delivery

Nano-devices are recognized as increasingly attractive to deliver therapeutics to target cells. The specificity of this approach can be improved by modifying the surface of the delivery vehicles such that they are recognized by the target cells. In the past, cell-surface receptors were exploited for this purpose, but plasma membrane transporters also hold similar potential. Selective transporters are often highly expressed in biological barriers (e.g., intestinal barrier, blood–brain barrier, and blood–retinal barrier) in a site-specific manner, and play a key role in the vectorial transfer of nutrients. Similarly, selective transporters are also overexpressed in the plasma membrane of specific cell types under pathological states to meet the biological needs demanded by such conditions. Nano-drug delivery systems could be strategically modified to make them recognizable by these transporters to enhance the transfer of drugs across the biological barriers or to selectively expose specific cell types to therapeutic drugs. Here, we provide a comprehensive review and detailed evaluation of the recent advances in the field of transporter-targeted nano-drug delivery systems. We specifically focus on areas related to intestinal absorption, transfer across blood–brain barrier, tumor-cell selective targeting, ocular drug delivery, identification of the transporters appropriate for this purpose, and details of the rationale for the approach

Dual targeting of l-carnitine-conjugated nanoparticles to OCTN2 and ATB0,+ to deliver chemotherapeutic agents for colon cancer therapy

l-Carnitine, obligatory for oxidation of fatty acids, is transported into cells by the Na+-coupled transporter OCTN2 and the Na+/Cl–-coupled transporter ATB0,+. Here we investigated the potential of L-carnitine-conjugated poly(lactic-co-glycolic acid) (PLGA) nanoparticles (LC-PLGA NPs) to deliver chemotherapeutic drugs into cancer cells by targeting the nanoparticles to both OCTN2 and ATB0,+. The cellular uptake of LC-PLGA NPs in the breast cancer cell line MCF7 and the colon cancer cell line Caco-2 was increased compared to unmodified nanoparticles, but decreased in the absence of co-transporting ions (Na+ and/or Cl–) or in the presence of competitive substrates for the two transporters. Studies with fluorescently labeled nanoparticles showed their colocalization with both OCTN2 and ATB0,+, confirming the involvement of both transporters in the cellular uptake of LC-PLGA NPs. As the expression levels of OCTN2 and ATB0,+ are higher in colon cancer cells than in normal colon cells, LC-PLGA NPs can be used to deliver chemotherapeutic drugs selectively into cancer cells for colon cancer therapy. With 5-fluorouracil-loaded LC-PLGA NPs, we were able to demonstrate significant increases in the uptake efficiency and cytotoxicity in colon cancer cells that were positive for OCTN2 and ATB0,+. In a 3D spheroid model of tumor growth, LC-PLGA NPs showed increased uptake and enhanced antitumor efficacy. These findings indicate that dual-targeting LC-PLGA NPs to OCTN2 and ATB0,+ has great potential to deliver chemotherapeutic drugs for colon cancer therapy. Dual targeting LC-PLGA NPs to OCTN2 and ATB0,+ can selectively deliver chemotherapeutics to colon cancer cells where both transporters are overexpressed, preventing targeting to normal cells and thus avoiding off-target side effects

Development and validation of a UPLC–MS/MS assay for the determination of gemcitabine and its L-carnitine ester derivative in rat plasma and its application in oral pharmacokinetics

A simple and rapid UPLC–MS/MS method to simultaneously determine gemcitabine and its L-carnitine ester derivative (2'-deoxy-2', 2'-difluoro-N-((4-amino-4-oxobutanoyl) oxy)-4-(trimethyl amm-onio) butanoate-cytidine, JDR) in rat plasma was developed and validated. The conventional plasma sample preparation method of nucleoside analogues is solid-phase extraction (SPE) which is time-consuming and cost-expensive. In this study, gradient elution with small particles size solid phase was applied to effectively separate gemcitabine and JDR, and protein precipitation pretreatment was adopted to remove plasma protein and extract the analytes with high recovery(>81%). Method validation was performed as per the FDA guidelines, and the standard curves were found to be linear in the range of 5–4000 ng/ml for JDR and 4–4000 ng/ml for gemcitabine, respectively. The lower limit of quantitation (LLOQ) of gemcitabine and JDR was 4 and 5 ng/ml, respectively. The intra-day and inter-day precision and accuracy results were within the acceptable limits. Finally, the developed method was successfully applied to investigate the pharmacokinetic studies of JDR and gemcitabine after oral administration to rats