Cellular Uptake and Transport Mechanism of 6-Mercaptopurine Nanomedicines for Enhanced Oral Bioavailability

2-Monoacylglycerol Mimetic Liposomes to Promote Intestinal Lymphatic Transport for Improving Oral Bioavailability of Dihydroartemisinin

Purpose

Reducing the first-pass hepatic effect via intestinal lymphatic transport is an effective way to increase the oral absorption of drugs. 2-Monoacylglycerol (2-MAG) as a primary digestive product of dietary lipids triglyceride, can be assembled in chylomicrons and then transported from the intestine into the lymphatic system. Herein, we propose a biomimetic strategy and report a 2-MAG mimetic nanocarrier to target the intestinal lymphatic system via the lipid absorption pathway and improve oral bioavailability.

Methods

The 2-MAG mimetic liposomes were designed by covalently bonding serinol (SER) on the surface of liposomes named SER-LPs to simulate the structure of 2-MAG. Dihydroartemisinin (DHA) was chosen as the model drug because of its disadvantages such as poor solubility and high first-pass effect. The endocytosis and exocytosis mechanisms were investigated in Caco-2 cells and Caco-2 cell monolayers. The capacity of intestinal lymphatic transport was evaluated by ex vivo biodistribution and in vivo pharmacokinetic experiments.

Results

DHA loaded SER-LPs (SER-LPs-DHA) had a particle size of 70 nm and a desirable entrapment efficiency of 93%. SER-LPs showed sustained release for DHA in the simulated gastrointestinal environment. In vitro cell studies demonstrated that the cellular uptake of SER-LPs primarily relied on the caveolae- rather than clathrin-mediated endocytosis pathway and preferred to integrate into the chylomicron assembly process through the endoplasmic reticulum/Golgi apparatus route. After oral administration, SER-LPs efficiently promoted drug accumulation in mesenteric lymphatic nodes. The oral bioavailability of DHA from SER-LPs was 10.40-fold and 1.17-fold larger than that of free DHA and unmodified liposomes at the same dose, respectively.

Conclusion

SER-LPs improved oral bioavailability through efficient intestinal lymphatic transport. These findings of the current study provide a good alternative strategy for oral delivery of drugs with high first-pass hepatic metabolism.

Combination of Chlorambucil and Mercaptopurine Show Effective Anti-Cancer Effects in Mice Model

Background

Combination therapy employing multiple drugs has been shown to enhance the efficacy of cancer treatment. Chlorambucil (Chl) and 6-mercaptopurine (6MP) are the first-line medicines for chronic lymphocytic leukemia and ovarian cancer. However, both were limited by their short half-life of disintegration, unsatisfactory water solubility, and adverse reactions.

Methods

In this work, the drug Chl and 6MP were introduced into the polymerized N-(2-hydroxypropyl) methacrylamide (polyHPMA) by pH and glutathione responsive linker to construct the polymer nanodrug delivery system for effective co-delivery.

Results

The drug load capacities, release, morphology, and cytotoxicity of the pro-drug were systematic. The two drugs showed satisfactory synergism with a combination index of 0.81, and a better ability to induce apoptosis. In and ex vivo fluorescence imaging showed a rapid systemic distribution of the conjugate within mice, majorly metabolized by liver and kidneys and eliminated after 24 hr. No significant pathological damage was observed in the major organs. This polymeric prodrug system holds promise for improved therapeutic efficiency and reduced side effects through the synergistic delivery of various chemotherapeutics.

Conclusion

The introduction of HPMA as a carrier not only enhanced the solubility and biocompatibilities of Chl and 6 MP but also improved their drug effect. This strategy might be a promising alternative for constructing multi-drug-release system.

Mechanisms of Nanoparticle Transport across Intestinal Tissue: An Oral Delivery Perspective

Oral drug administration has been a popular choice due to patient compliance and limited clinical resources. Orally delivered drugs must circumvent the harsh gastrointestinal (GI) environment to effectively enter the systemic circulation. The GI tract has a number of structural and physiological barriers that limit drug bioavailability including mucus, the tightly regulated epithelial layer, immune cells, and associated vasculature. Nanoparticles have been used to enhance oral bioavailability of drugs, as they can act as a shield to the harsh GI environment and prevent early degradation while also increasing uptake and transport of drugs across the intestinal epithelium. Evidence suggests that different nanoparticle formulations may be transported via different intracellular mechanisms to cross the intestinal epithelium. Despite the existence of a significant body of work on intestinal transport of nanoparticles, many key questions remain: What causes the poor bioavailability of the oral drugs? What factors contribute to the ability of a nanoparticle to cross different intestinal barriers? Do nanoparticle properties such as size and charge influence the type of endocytic pathways taken? In this Review, we summarize the different components of intestinal barriers and the types of nanoparticles developed for oral delivery. In particular, we focus on the various intracellular pathways used in nanoparticle internalization and nanoparticle or cargo translocation across the epithelium. Understanding the gut barrier, nanoparticle characteristics, and transport pathways may lead to the development of more therapeutically useful nanoparticles as drug carriers.