A multiaspect study on transcytosis mechanism of sorafenib nanogranules engineered by high-gravity antisolvent precipitation

Impact of Physiological Characteristics on Chylomicron Pathway-Mediated Absorption of Nanocrystals in the Pediatric Population

Nanocrystals exhibit significant advantages in improving the oral bioavailability of poorly soluble drugs. However, the complicated absorption properties of nanocrystals and the differences in physiological characteristics between children and adults limit pediatric applications of nanocrystals. To elucidate the absorption differences and the underlying mechanisms between children and adults, the pharmacokinetics and tissue distribution of aprepitant crystals with different particle sizes (NC200, NC500, and MC2.5) in rats and mice at different ages were studied, and their absorption mechanisms were investigated in Caco-2 cells, mice, and rats. It was found that childhood animals demonstrated higher bioavailability compared with adolescent and adult animals, which was related to higher bile salt concentration and accelerated drug dissolution in the intestine of childhood animals. The majority of nanocrystals were dissolved and formed micelles under the influence of bile salts. Compared with intact nanocrystals, the bile salt micelle-associated aprepitant was absorbed through the chylomicron pathway, wherein Apo B assisted in the reassembling of the aprepitant micelles after endocytosis. Higher bile salt concentration and Apo B expression in the intestines of childhood animals are both responsible for the higher chylomicron transport pathways. Elucidation of the chylomicron pathway in the varied absorption of nanocrystals among children, adolescents, and adults provides strong theoretical guidance for promoting the rational and safe use of nanocrystals in pediatric populations.

The Controlled Preparation of a Carrier-Free Nanoparticulate Formulation Composed of Curcumin and Piperine Using High-Gravity Technology

Carrier-free nanoparticulate formulations are an advantageous platform for the oral administration of insoluble drugs with the expectation of improving their bioavailability. However, the key limitation of exploiting carrier-free nanoparticulate formulations is the controlled preparation of drug nanoparticles on the basis of rational prescription design. In the following study, we used curcumin (Cur) and piperine (Pip) as model water-insoluble drugs and developed a new method for the controlled preparation of carrier-free drug nanoparticles via multidrug co-assembly in a high-gravity environment. Encouraged by the controlled regulation of the nucleation and crystal growth rate of high-gravity technology accomplished by a rotating packed bed, co-amorphous Cur-Pip co-assembled multidrug nanoparticles with a uniform particle size of 130 nm were successfully prepared, exhibiting significantly enhanced dissolution performance and in vitro cytotoxicity. Moreover, the hydrogen bonding interactions between Cur and Pip in nanoparticles provide them with excellent re-dispersibility and storage stability. Moreover, the oral bioavailability of Cur was dramatically enhanced as a result of the smaller particle size of the co-assembled nanoparticles and the effective metabolic inhibitory effect of Pip. The present study provides a controlled approach to preparing a carrier-free nanoparticulate formulation through a multidrug co-assembly process in the high-gravity field to improve the oral bioavailability of insoluble drugs.

Customized Intranasal Hydrogel Delivering Methylene Blue Ameliorates Cognitive Dysfunction against Alzheimer's Disease

The accumulation of hyperphosphorylated tau protein aggregates is a key pathogenic event in Alzheimer's disease (AD) and induces mitochondrial dysfunction and reactive oxygen species overproduction. However, the treatment of AD remains challenging owning to the hindrance caused by the blood-brain barrier (BBB) and the complex pathology of AD. Nasal delivery represents an effective means of circumventing the BBB and delivering drugs to the brain. In this study, black phosphorus (BP) is used as a drug carrier, as well as an antioxidant, and loaded with a tau aggregation inhibitor, methylene blue (MB), to obtain BP-MB. For intranasal (IN) delivery, a thermosensitive hydrogel is fabricated by cross-linking carboxymethyl chitosan and aldehyde Pluronic F127 (F127-CHO) micelles. The BP-MB nanocomposite is incorporated into the hydrogel to obtain BP-MB@Gel. BP-MB@Gel could be injected intranasally, providing high nasal mucosal retention and controlled drug release. After IN administration, BP-MB is continuously released and delivered to the brain, exerting synergistic therapeutic effects by suppressing tau neuropathology, restoring mitochondrial function, and alleviating neuroinflammation, thus inducing cognitive improvements in mouse models of AD. These findings highlight a potential strategy for brain-targeted drug delivery in the management of the complex pathologies of AD.

The Increased Dissolution and Oral Absorption of Itraconazole by Nanocrystals with an Endogenous Small-Molecule Surfactant as a Stabilizer

The aim of this study was to develop cholic-acid-stabilized itraconazole nanosuspensions (ITZ-Nanos) with the objective of enhancing drug dissolution and oral absorption. A laboratory-scale microprecipitation-high-pressure homogenization method was employed for the preparation of the ITZ-Nanos, while dynamic light scattering, transmission electron microscope analysis, X-ray diffraction, differential scanning calorimetry, and high-performance liquid chromatography analysis were utilized to evaluate their physicochemical properties. The absorption and bioavailability of the ITZ-Nanos were assessed using Caco-2 cells and rats, with Sporanox® pellets as a comparison. Prior to lyophilization, the particle size of the ITZ-Nanos measured approximately 225.7 nm. Both X-ray diffraction and differential scanning calorimetry confirmed that the ITZ remained crystalline within the nanocrystals. Compared to the pellets, the ITZ-Nanos exhibited significantly higher levels of supersaturation dissolution and demonstrated enhanced drug uptake by the Caco-2 cells. The AUC(0-t) value for the ITZ-Nanos in rats was 1.33-fold higher than that observed for the pellets. These findings suggest that cholic acid holds promise as a stabilizer for ITZ nanocrystals, as well as potentially other nanocrystals.

Recent developments in the use of nanocrystals to improve bioavailability of APIs

Nanocrystals refer to materials with at least one dimension smaller than 100 nm, composing of atoms arranged in single crystals or polycrystals. Nanocrystals have significant research value as they offer unique advantages over conventional pharmaceutical formulations, such as high bioavailability, enhanced targeting selectivity and controlled release ability and are therefore suitable for the delivery of a wide range of drugs such as insoluble drugs, antitumor drugs and genetic drugs with broad application prospects. In recent years, research on nanocrystals has been progressively refined and new products have been launched or entered the clinical phase of studies. However, issues such as safety and stability still stand that need to be addressed for further development of nanocrystal formulations, and significant gaps do exist in research in various fields in this pharmaceutical arena. This paper presents a systematic overview of the advanced development of nanocrystals, ranging from the preparation approaches of nanocrystals with which the bioavailability of poorly water-soluble drugs is improved, critical properties of nanocrystals and associated characterization techniques, the recent development of nanocrystals with different administration routes, the advantages and associated limitations of nanocrystal formulations, the mechanisms of physical instability, and the enhanced dissolution performance, to the future perspectives, with a final view to shed more light on the future development of nanocrystals as a means of optimizing the bioavailability of drug candidates. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Remodeling of intestinal epithelium derived extracellular vesicles by nanoparticles and its bioeffect on tumor cell migration

Extracellular vesicles (EVs) are an effective tool to elucidate the bioeffect of nanomedicines. To clarify the interaction between oral nanomedicines and intestinal epithelial cells, and their bioeffects on downstream cells, polystyrene nanoparticles (PS-NPs) with different sizes were used as the model nanomedicines for EVs induction. Caco-2 monolayers were selected as the model of the intestinal epithelium and DLD-1 cells as the colorectal cancer model proximal to the gastrointestinal tract. It is found that compared with small-sized (25, 50, 100 nm) PS-NPs, the large-sized (200 and 500 nm) exhibited higher co-localization with multivesicular bodies and lysosomes, and more significant reduction of lysosomal acidification in Caco-2 cells. Proteomic and western-blotting analysis showed that the EVs remodeled by large-sized PS-NPs exhibited a higher extent of protein expression changes. The in vitro and in vivo signaling pathway detection in DLD-1 cells and DLD-1 cell xenograft nude mice showed that the remodeled EVs by large-sized PS-NPs inhibited the activation of multiple signaling pathways including Notch3, EGF/EGFR, and PI3K/Akt pathways, which resulted in the inhibition of tumor cell migration. These results primarily clarify the regulation mechanisms of nanomedicines-EVs-receptor cells chain. It provides a new perspective for the rational design and bioeffect evaluation of oral drug nanomaterials and sets up the fundamental knowledge for novel tumor therapeutics in the future.

Enantioselective Oral Absorption of Molecular Chiral Mesoporous Silica Nanoparticles

Inspired by the unique pharmacological effects of chiral drugs in the asymmetrical body environments, it is assumed that the chirality of nanocarriers is also a key factor to determine their oral adsorption efficiency, apart from their size, shape, etc. Herein, l/d-tartaric acid modified mesoporous silica nanoparticles (l/d-CMSNs) are fabricated via a one-pot cocondensation method, and focused on whether the oral adsorption of nanocarriers will be benefited from their chirality. It is found that l-CMSN performed better in the sequential oral absorption processes, including mucus permeation, mucosa bio-adhesion, cellular uptake, intestinal transport and gastrointestinal tract (GIT) retention, than those of the d-chiral (d-CMSN), racemic (dl-CMSN), and achiral (MSN) counterparts. The multiple chiral recognition mechanisms are experimentally and theoretically demonstrated following simple differential adsorption on biointerfaces, wherein electrostatic interaction is the dominant energy. During the oral delivery task, l-CMSN, which is proven to be stable, nonirritative, biocompatible, and biodegradable, is efficiently absorbed into the blood (1.72-2.05-fold higher than other nanocarriers), and helps the loaded doxorubicin (DOX) to achieve better intestinal transport (2.32-27.03-times higher than other samples), satisfactory bioavailability (449.73%) and stronger antitumor effect (up to 95.43%). These findings validated the dominant role of chirality in determining the biological fate of nanocarriers.

Oral lymphatic delivery of alpha-galactosylceramide and ovalbumin evokes anti-cancer immunization

We developed an orally delivered nanoemulsion that induces cancer immunization. It consists of tumor antigen-loaded nano-vesicles carrying the potent invariant natural killer T-cell (iNKT) activator α-galactosylceramide (α-GalCer), to trigger cancer immunity by effectively activating both innate and adaptive immunity. It was validated that adding bile salts to the system boosted intestinal lymphatic transport as well as the oral bioavailability of ovalbumin (OVA) via the chylomicron pathway. To increase intestinal permeability further and amplify the antitumor responses, an ionic complex of cationic lipid 1,2-dioleyl-3-trimethylammonium propane (DTP) with sodium deoxycholate (DA) (DDP) and α-GalCer were anchored onto the outer oil layer to form OVA-NE#3. As expected, OVA-NE#3 exhibited tremendously improved intestinal cell permeability as well as enhanced delivery to mesenteric lymph nodes (MLNs). Subsequent activation of dendritic cells and iNKTs, in MLNs were also observed. Tumor growth in OVA-expressing mice with melanoma was more strongly suppressed (by 71%) after oral administration of OVA-NE#3 than in untreated controls, confirming the strong immune response induced by the system. The serum levels of OVA-specific IgG1 and IgG2a were 3.52- and 6.14-fold higher than in controls. Treating OVA-NE#3 increased the numbers of tumor-infiltrating lymphocytes, including cytotoxic T-cell and M1-like macrophage. Antigen- and α-GalCer-associated enrichment of dendritic cells and iNKTs in tumor tissues also increased after OVA-NE#3 treatment. These observations indicate that our system induces both cellular and humoral immunity by targeting the oral lymphatic system. It may offer a promising oral anti-cancer vaccination strategy that involves the induction of systemic anti-cancer immunization.

Oral Delivery of siRNA Using Fluorinated, Small-Sized Nanocapsules toward Anti-Inflammation Treatment

Oral delivery of small interfering RNA (siRNA) provides a promising paradigm for treating diseases that require regular injections. However, the multiple gastrointestinal (GI) and systemic barriers often lead to inefficient oral absorption and low bioavailability of siRNA. Technologies that can overcome these barriers are still lacking, which hinders the clinical potential of orally delivered siRNA. Herein, small-sized, fluorinated nanocapsules (F-NCs) are developed to mediate efficient oral delivery of tumor necrosis factor α (TNF-α) siRNA for anti-inflammation treatment. The NCs possess a disulfide-cross-linked shell structure, thus featuring robust stability in the GI tract. Because of their small size (≈30 nm) and fluorocarbon-assisted repelling of mucin adsorption, the best-performing F₃ -NCs show excellent mucus penetration and intestinal transport capabilities without impairing the intestinal tight junction, conferring the oral bioavailability of 20.4% in relative to intravenous injection. The disulfide cross-linker can be cleaved inside target cells, causing NCs dissociation and siRNA release to potentiate the TNF-α silencing efficiency. In murine models of acute and chronic inflammation, orally delivered F₃ -NCs provoke efficient TNF-α silencing and pronounced anti-inflammatory efficacies. This study therefore provides a transformative strategy for oral siRNA delivery, and will render promising utilities for anti-inflammation treatment.

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

Background

Nanomedicines have significant advantages in enhancing the oral bioavailability of drugs, but a deeper understanding of the underlying mechanisms remains to be interpreted. Hence, the present study aims to explain the uptake and trafficking mechanism for 6-MP nanomedicines we previously constructed.

Methods

6-MP loaded poly(lactide-co-glycolide) (PLGA) nanomedicines (6-MPNs) were prepared by the multiple emulsion method. The transcytosis mechanism of 6-MPNs was investigated in Caco-2 cells, Caco-2 monolayers, follicle associated epithelium (FAE) monolayers and rats, including transmembrane pathway, intracellular trafficking, paracellular transport and the involvement of transporter.

Results

Pharmacokinetics in rats showed that the area under the curve (AUC) of 6-MP in the 6-MPNs group (147.3 ± 42.89 μg/L·h) was significantly higher than that in the 6-MP suspensions (6-MPCs) group (70.31 ± 18.24 μg/L·h). The uptake of 6-MPNs in Caco-2 cells was time-, concentration- and energy-dependent. The endocytosis of intact 6-MPNs was mediated mainly through caveolae/lipid raft, caveolin and micropinocytosis. The intracellular trafficking of 6-MPNs was affected by endoplasmic reticulum (ER)-Golgi complexes, late endosome-lysosome and microtubules. The multidrug resistance associated protein 4 (MRP4) transporter-mediated transport of free 6-MP played a vital role on the transmembrane of 6-MPNs. The trafficking of 6-MPNs from the apical (AP) side to the basolateral (BL) side in Caco-2 monolayers was obviously improved. Besides, 6-MPNs affected the distribution and expression of zona occludens-1 (ZO-1). The transport of 6-MPNs in FAE monolayers was concentration- and energy-dependent, while reaching saturation over time. 6-MPNs improved the absorption of the intestinal Peyer's patches (PPs) in rats.

Conclusion

6-MPNs improve the oral bioavailability through multiple pathways, including active transport, paracellular transport, lymphatic delivery and MRP4 transporter. The findings of current study may shed light on the cellular uptake and transcellular trafficking mechanism of oral nanomedicines.

A common strategy to improve transmembrane transport in polarized epithelial cells based on sorting signals: Guiding nanocarriers to TGN rather than to the basolateral plasma membrane directly

The intestinal barrier has always been the rate-limiting step in the oral administration process. To overcome the intestinal barrier, researchers have widely adopted nanocarriers, especially active-targeting nanocarriers strategies. However, most of these strategies focus on the ligand decoration of nanocarriers targeting specific receptors, so their applications are confined to specific receptors or specific cell types. In this study, we tried to investigate more common strategies in the field of transmembrane transport enhancement. Trans-Golgi network (TGN) is the sorting center of biosynthetic route which could achieve polarized localization of proteins in polarized epithelial cells, and the basolateral plasma membrane is where all transcytotic cargos have to pass through. Thus, it is expected that guiding nanocarriers to TGN or basolateral plasma membrane may improve the transcytosis. Hence, we choose sorting signal peptide to modify micelles to guide micelles to TGN (named as BAC decorated micelles, BAC-M) or to basolateral plasma membrane (named as STX decorated micelles, STX-M). By incorporating coumarin-6 (C6) or Cy5-PEG-PCL in the micelles to indicate the behavior of micelles, the effects of these two strategies on the transcytosis were investigated. To our surprise, BAC-M and STX-M behaved quite differently when crossing biological barriers. BAC-M showed significant superiority in colocalization with TGN, transmembrane transport and even in vivo absorption, while STX-M had no significant difference from blank micelles. Further investigation revealed that the strategy of directly guiding nanocarriers to the basolateral plasma membrane (STX-M) only caused the stack of vesicles near the basolateral plasma membrane. So, we concluded that guiding nanocarriers to TGN which related to secretion may contribute to the transmembrane transport. This common strategy based on the physiological function of TGN in polarized epithelial cells will have broad application prospects in overcoming biological barrier.

Nanocrystals for Improving Oral Bioavailability of Drugs: Intestinal Transport Mechanisms and Influencing Factors

With the limitation of solubility and dissolution rate of insoluble drugs, following oral administration, they would rifely prove poor and volatile bioavailability, which may fail to realize its therapeutic value. The drug nanocrystals are perceived as effective tactic for oral administration of insoluble drugs attributes to possess many prominent properties such as elevating dissolution rate and saturation solubility, high drug loading capacity, and improving oral bioavailability. Based on these advantages, the application of nanocrystals in oral drug delivery has acquired significant achievement, and so far more than 20 products of drug nanocrystals have been confirmed in the market. However, the oral absorption of drug nanocrystals is still facing huge challenges due to the limitation of many factors. Intrinsic properties of the drugs and complex physiological environment of the intestinal tract are the two most important factors affecting the oral bioavailability of drugs. In addition, the research on the multi-aspect mechanisms of nanocrystals promoting gastrointestinal absorption and bioavailability has been gradually deepened. In this review, we summarized recent advances of the nanocrystals delivered orally, and provided an overview to the research progress for crossing the intestinal tract transport mechanisms of the nanocrystals by some new research techniques. Meanwhile, the factors relevant to the transport of drug nanocrystals were also elaborated in detail. Graphical Abstract.

Current strategies for oral delivery of BCS IV drug nanocrystals: challenges, solutions and future trends

INTRODUCTION

Oral absorption of BCS IV drug benefits little from improved dissolution. Therefore, the absorption of BCS IV drug nanocrystals 'as a whole' strategy is preferred, and structural modification of nanocrystals is required. Surface modification helps the nanocrystals maintain particle structure before drug dissolution is needed, thus enhancing the oral absorption of BCS IV drugs and promoting therapeutic effect. Here, the main challenges and solutions of oral BCS IV drug nanocrystals delivery are discussed. Moreover, strategies for nanocrystal surface modification that facilitates oral bioavailability of BCS IV drugs are highlighted, and provide insights for the innovation in oral drug delivery.

AREAS COVERED

Promising size, shape, and surface modification of nanocrystals have gained interests for application in oral BCS IV drugs.

EXPERT OPINION

Nanocrystal surface modification is a feasible method to maintain the structural integrity of nanocrystals, and the introduced materials can also be modified to integrate additional functions to further facilitate the absorption of nanocrystals. It is expected that the absorption 'as a whole' strategy of nanocrystals will provide different choices for the oral BCS IV drugs.

Bile acid transporter-mediated oral drug delivery

Bile acids are synthesized in the liver, stored in the gallbladder, and secreted into the duodenum at meals. Apical sodium-dependent bile acid transporter (ASBT), an ileal Na⁺-dependent transporter, plays the leading role of bile acid absorption into enterocytes, where bile acids are delivered to basolateral side by ileal bile acid binding protein (IBABP) and then released by organic solute transporter OSTα/β. The absorbed bile acids are delivered to the liver via portal vein. In this process called "enterohepatic recycling", only 5% of the bile acid pool (~3 g in human) is excreted in feces, indicating the large recycling capacity and high transport efficacy of ASBT-mediated absorption. Therefore, bile acid transporter-mediated oral drug delivery has been regarded as a feasible and potential strategy to improve the oral bioavailability. This review introduces the key factors in enterohepatic recycling, especially the mechanism of bile acid uptake by ASBT, and the development of bile acid-based oral drug delivery for ASBT-targeting, including bile acid-based prodrugs, bile acid/drug electrostatic complexation and bile acid-containing nanocarriers. Furthermore, the specific transport pathways of bile acid in enterocytes are described and the recent finding of lymphatic delivery of bile acid-containing nanocarriers is discussed.