Transmembrane Pathways and Mechanisms of Rod-like Paclitaxel Nanocrystals through MDCK Polarized Monolayer

Modulating the Protein Corona on Nanoparticles by Finely Tuning Cross-Linkers Improves Macrophage Targeting in Oral Small Interfering RNA Delivery

The protein corona (PC) plays an important role in regulating the in vivo fate of nanoparticles (NPs). Modulating the surface chemical properties of NPs to control PC formation provides an alternative impetus for the oral delivery of small interfering RNA (siRNA). Herein, using tripolyphosphate (TPP), hyaluronic acid, and poly-γ-glutamic acid as cross-linkers, three types of mannose-modified trimethyl chitosan-cysteine (MTC)-based NPs with distinct surface chemistries were prepared to encapsulate siRNA via ionic gelation. The MTC-based NPs that were cross-linked exclusively with TPP (MTC/TPP/siRNA NPs) exhibited greater thiol group accessibility on their surfaces, resulting in a stronger affinity for apolipoprotein (APO) B48 during translocation across intestinal epithelia. Moreover, intracellular transport of MTC/TPP/siRNA NPs via the endoplasmic reticulum and Golgi apparatus further increased adsorption of APOB48, a key component of chylomicrons, which follow a similar transport pathway. Benefiting from the elevated APOB48 levels within the PC, the orally delivered MTC/TPP/siRNA NPs showed higher uptake by hepatic macrophages and better therapeutic efficacy for acute liver injury. Our results elucidate the role of NP surface chemical characteristics and translocation mechanisms across intestinal epithelia in forming oral PC, providing valuable insights for designing NPs that achieve effective oral gene delivery by customizing PC formation in vivo.

3-Indoleacetic Acid-Modified Chondroitin Sulfate-Mediated Paclitaxel Nanocrystal Assembly for the Treatment of Pancreatic Cancer

High drug-loading nanocrystals show significant advantages in delivering hydrophobic small-molecule drugs. However, these nanocrystals face challenges, including inherent instability and limited targetability. In this study, we developed a paclitaxel nanocrystal delivery platform based on chondroitin sulfate modified with 3-indoleacetic acid (CS-IAA). Paclitaxel and CS-IAA assembled into stable nanocrystals (PTX@CS-IAA, PC) with a high drug loading (up to 46.6%), facilitated by π-π stacking and hydrophobic interactions. CS-IAA targets tumors through CD44 receptors, which helps to minimize off-target effects. Additionally, CS-IAA, serving as a functional delivery vehicle, can significantly increase reactive oxygen species (ROS) levels at the tumor site. In an orthotopic pancreatic cancer mouse model, PTX@CS-IAA nanocrystals showed significantly enhanced antitumor effects. When PTX@CS-IAA was combined with the αPD-L1 antibody, the survival of mice with pancreatic tumors was further prolonged. This study provides valuable insights into alternative treatment options for pancreatic cancer, with the potential to improve patient prognosis and survival.

Intestinal nanoparticle delivery and cellular response: a review of the bidirectional nanoparticle-cell interplay in mucosa based on physiochemical properties

Orally administered nanocarriers play an important role in improving druggability, promoting intestinal absorption, and enhancing therapeutic applications for the treatment of local and systemic diseases. However, the delivering efficiency and cell response in mucosa to orally administered nanocarriers is affected by the physiological environment and barriers in the gastrointestinal tract, the physicochemical properties of the nanocarriers, and their bidirectional interactions. Goblet cells secrete and form extracellular mucus, which hinders the movement of nanoparticles. Meanwhile, intestinal epithelial cells may absorb the NPs, allowing for their transcytosis or degradation. Conversely, nanoparticle-induced toxicity may occur as a biological response to the nanoparticle exposure. Additionally, immune response and cell functions in secretions such as mucin, peptide, and cytokines may also be altered. In this review, we discuss the bidirectional interactions between nanoparticles and cells focusing on enterocytes and goblet cells, M cells, and immune cells in the mucosa according to the essential role of intestinal epithelial cells and their crosstalk with immune cells. Furthermore, we discuss the recent advances of how the physiochemical properties of nanoparticles influence their interplay, delivery, and fate in intestinal mucosa. Understanding the fate of nanoparticles with different physiochemical properties from the perspective of their interaction with cells in mucosa provides essential support for the development, rational design, potency maximation, and application of advanced oral nanocarrier delivery systems.

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.

Combined Hydroxyethyl Starch Luteolin Nanocrystals for Effective Anti-Hyperuricemia Effect in Mice Model

Introduction

Although flavonoid compounds exhibit various pharmacological activities, their clinical applications are restricted by low oral bioavailability owing to their poor solubility. Nanocrystals (NCs) represent an excellent strategy for enhancing the oral bioavailability of flavonoids. Hydroxyethyl starch (HES), a biomaterial compound used as a plasma expander, could be an ideal stabilizer material for preparing flavonoid NCs.

Methods

HES was used to stabilize flavonoid nanocrystals (NCs), using luteolin (LUT) as a model drug. After full characterization, the freeze-drying and storage stability, solubility, intestinal absorption, pharmacokinetics, and in vivo anti-hyperuricemic effect of the optimized HES-stabilized LUT NCs (LUT-HES NCs) were investigated.

Results

Uniformed LUT-HES NCs were prepared with mean particle size of 191.1±16.8 nm, zeta potential of about -23 mV, drug encapsulation efficiency of 98.52 ± 1.01%, and drug loading of 49.26 ± 0.50%. The freeze-dried LUT-HES NCs powder showed good re-dispersibility and storage stability for 9 months. Notably, compared with the coarse drug, LUT-HES NCs exhibited improved saturation solubility (7.49 times), increased drug dissolution rate, enhanced Caco-2 cellular uptake (2.78 times) and oral bioavailability (Fr=355.7%). Pharmacodynamic studies showed that LUT-HES NCs remarkably lowered serum uric acid levels by 69.93% and ameliorated renal damage in hyperuricemic mice.

Conclusion

HES is a potential stabilizer for poorly soluble flavonoid NCs and provides a promising strategy for the clinical application of these compounds. LUT-HES NCs may be an alternative or complementary strategy for hyperuricemia treatment.

Combination of PEGylation and Cationization on Phospholipid-Coated Cyclosporine Nanosuspensions for Enhanced Ocular Drug Delivery

Strong precorneal clearance mechanisms including reflex blink, constant tear drainage, and rapid mucus turnover constitute great challenges for eye drops for effective drug delivery to the ocular epithelium. In this study, cyclosporine A (CsA) for the treatment of dry eye disease (DED) was selected as the model drug. Two strategies, PEGylation for mucus penetration and cationization for potent cellular uptake, were combined to construct a novel CsA nanosuspension (NS@lipid-PEG/CKC) by coating nanoscale drug particles with a mixture of lipids, DSPE-PEG2000, and a cationic surfactant, cetalkonium chloride (CKC). NS@lipid-PEG/CKC with the mean size ∼173 nm and positive zeta potential ∼+40 mV showed promoted mucus penetration, good cytocompatibility, more cellular uptake, and prolonged precorneal retention without obvious ocular irritation. More importantly, NS@lipid-PEG/CKC recovered tear production and goblet cell density more efficiently than the commercial cationic nanoemulsion on a dry eye disease rat model. All results indicated that a combination of PEGylation and cationization might provide a promising strategy to coordinate mucus penetration and cellular uptake for enhanced drug delivery to the ocular epithelium for nanomedicine-based eye drops.

Intravenous nanocrystals: fabrication, solidification, in vivo fate, and applications for cancer therapy

INTRODUCTION

Intravenous nanocrystals (INCs) have shown intrinsic advantages in antitumor applications, particularly their properties of high drug loading, low toxicity, and controllable size. Therefore, it has a very bright application prospect as a drug delivery system.

AREAS COVERED

The ideal formulation design principles, fabrication, solidification, in vivo fate of INCs, the applications in drug delivery system (DDS) and the novel applications are covered in this review.

EXPERT OPINION

It is vital to select a suitable formulation and fabrication method to produce a stable and sterile INCs. Besides, the type of stabilizers and physical characteristics can also influence the in vivo fate of INCs, which is worthy of further studying. Based on wide researches about applications of INCs in cancer, biomimetic INCs are concerned increasingly for its favorable compatibility. The output of these studies suggested that INCs-based drug delivery could be a novel strategy for addressing the delivery of the drug that faces solubility, bioavailability, and toxicity problems.

Recent advances in bioactive nanocrystal-stabilized Pickering emulsions: Fabrication, characterization, and biological assessment

Numerous literatures have shown the advantages of Pickering emulsion (PE) for the delivery of bioactive ingredients in the fields of food, medicine, and cosmetics, among others. On this basis, the multi-loading mode of bioactives (internal phase encapsulation and/or loading at the interface) in small molecular bioactives nanocrystal-stabilized PE (BNC-PE) enables them higher loading efficiencies, controlled release, and synergistic or superimposed effects. Therefore, BNC-PE offers an efficacious delivery system. In this review, we briefly summarize BNC-PE fabrication and characterization, with a focus on the processes of possible evolution and absorption of differentially applied BNC-PE when interacting with the body. In addition, methods of monitoring changes and absorption of BNC-PE in vivo, from the nanomaterial perspective, are also introduced. The purpose of this review is to provide an accessible and comprehensive methodology for the characterization and evaluation of BNC-PE after formulation and preparation, especially in relation to biological assessment and detailed mechanisms throughout the absorption process of BNC-PE in vivo.

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.

Chondroitin Sulfate-Derived Paclitaxel Nanocrystal via π-π Stacking with Enhanced Stability and Tumor Targetability

Nanocrystals with high drug loading have become a viable strategy for solubilizing drugs with poor aqueous solubility. It remains challenging, however, to synthesize nanocrystals with sufficient stability and targeting potential. Here, we report a novel nanocrystal platform synthesized using paclitaxel (PTX) and Fmoc-8-amino-3,6-dioxaoctanoic acid (Fmoc-AEEA)-conjugated chondroitin sulfate (CS) (CS-Fmoc) via π-π stacking to afford a stable formulation with CD44 targetability (PTX NC@CS-Fmoc). The PTX NC@CS-Fmoc exhibited rodlike shapes with an average hydrodynamic size of 173.6 ± 0.7 nm (PDI = 0.11 ± 0.04) and a drug loading of up to 31.3 ± 0.6%. Next, PTX NC@CS-Fmoc was subjected to lyophilization in the absence of cryoprotectants for long-term storage, and after redispersion, PTX NC@CS-Fmoc displayed an average hydrodynamic size of 205.3 ± 2.9 nm (PDI = 0.15 ± 0.01). In murine Panc02 cells, PTX NC@CS-Fmoc showed higher internalization efficiency than that of PTX nanocrystals without CS modification (PTX NC@F127) (P < 0.05) or that of CS-Fmoc micelles (P < 0.05). Moreover, PTX NC@CS-Fmoc appeared to accumulate in both lysosomes and Golgi apparatus, while CS-Fmoc micelles accumulated specifically in the Golgi apparatus. In the orthotopic Panc02 tumor-bearing mice model, PTX NC@CS-Fmoc showed higher tumor-specific accumulation than CS-Fmoc micelles, which also demonstrated comparable tumor growth inhibition as to Nab-PTX. Overall, the CS-Fmoc-derived nanocrystals represent a neat and viable formulation strategy for targeted chemotherapy with great potential for translational studies.

Efficient Sustained-Release Nanoparticle Delivery System Protects Nigral Neurons in a Toxin Model of Parkinson’s Disease

Parkinson’s disease (PD) is a serious neurodegenerative disease wherein the progressive destruction of dopaminergic neurons results in a series of related movement disorders. Effective oral delivery of anti-Parkinson’s drugs is challenging owing to the blood-brain barrier (BBB) and the limited plasma exposure. However, polymeric nanoparticles possess great potential to enhance oral bioavailability, thus improving drug accumulation within the brain. In this work, biodegradable poly(ethylene glycol)-b-poly(trimethylene carbonate) (PEG-PTMC) nanoparticles (PPNPs) were developed to deliver Ginkgolide B (GB) as a potent treatment for PD, aiming to enhance its accumulation within both the blood and the brain. The resultant GB-PPNPs were able to facilitate sustained GB release for 48 h and to protect against 1-methyl-4-phenylpyridine (MPP⁺)-induced neuronal cytotoxicity without causing any toxic damage. Subsequent pharmacokinetic studies revealed that GB-PPNPs accumulated at significantly higher concentrations in the plasma and brain relative to free GB. Oral GB-PPNP treatment was also linked to desirable outcomes in an animal model of PD, as evidenced by improvements in locomotor activity, levels of dopamine and its metabolites, and tyrosine hydroxylase activity. Together, these data suggest that PPNPs may represent promising tools for the effective remediation of PD and other central nervous system disorders.

Biological and Intracellular Fates of Drug Nanocrystals through Different Delivery Routes: Recent Development Enabled by Bioimaging and PK Modeling

Nanocrystals have contributed to exciting improvements in the delivery of poorly water-soluble drugs. The biological and intracellular fates of nanocrystals are currently under debate. Due to the remarkable commercial success in enhancing oral bioavailability, nanocrystals have originally been regarded as a simple formulation approach to enhance dissolution. However, the latest findings from novel bioimaging tools lead to an expanded view. Intact nanocrystals may offer long-term durability in the body and offer drug delivery capabilities like those of other nano-carriers. This review renews the understanding of the biological fates of nanocrystals administered via oral, intravenous, and parenteral (e.g., dermal, ocular, and pulmonary) routes. The intracellular pathways and dissolution kinetics of nanocrystals are explored. Additionally, the future trends for in vitro and in vivo quantification of nanocrystals, as well as factors impacting the biological and intracellular fates of nanocrystals are discussed. In conclusion, nanocrystals present a promising and underexplored therapeutic opportunity with immense potential.

ZIF-based carbon dots with lysosome-Golgi transport property as visualization platform for deep tumour therapy via hierarchical size/charge dual-transform and transcytosis

The poor penetration of nanomaterials in solid tumours and difficulty in monitoring their penetration depth are major obstacles in their application for the treatment of solid tumours. Herein, pH-responsive carbon dots (ZCD) based on a zeolitic imidazolate framework (ZIF-8) were fabricated to achieve the deep delivery of the chemotherapeutic doxorubicin (DOX) via a hierarchical size/charge dual-transformation and transcytosis. The as-prepared ZCD accumulated in the solid tumour and the acidic tumour microenvironment further triggered its decomposition. Firstly, ZCD was decomposed by the weakly acidic extracellular microenvironment of the solid tumour, enabling it to transform into small and neutrally charged particles. Subsequently, these particles were endocytosed by lysosomes, and further disintegrated into smaller and positively charged particles, which could target the Golgi apparatus. Consequently, ZCD delivered DOX deep into the solid tumour via a size-shrinking strategy and Golgi-mediated transcytosis, thus significantly improving its antitumour efficacy. In addition, carbonization endowed ZCD with superior fluorescence property, which was enhanced in the acidic microenvironment, thus improving the sensitivity and accuracy of ex vivo monitoring of the penetration depth of the nanomedicine in real time. Collectively, our results confirmed that the carbon dots obtained via the direct carbonization of ZIF-8 simultaneously exhibited enhanced deep penetration into solid tumours and fluorescence, which could be monitored, and that the carbonization of functional materials is effective to enhance their fluorescence, and further broaden their applications.

Biomimetic and temporal-controlled nanocarriers with ileum transporter targeting for achieving oral administration of chemotherapeutic drugs

BACKGROUND

Oral chemotherapy is preferred for patients with cancer owing to its multiple advantages, including convenience, better patient compliance, and improved safety. Nevertheless, various physical barriers exist in this route that hamper the development of oral chemotherapeutic formulations, including destruction of drugs in the gastrointestinal tract (GIT), low permeability in enterocytes, and short residence time in the intestine. To overcome these limitations, it is necessary to design an efficient oral drug delivery system with high efficacy and improved safety.

RESULTS

Herein, we designed novel glycocholic acid (GCA)-functionalized double layer nanoparticles (GCA-NPs), which can act via an endogenous pathway and in a temporally controlled manner in the intestine, to enhance the oral bioavailability of hydrophobic chemotherapeutic drugs such as paclitaxel (PTX). GCA-NPs were composed of quercetin (Qu)-modified liposomes (QL) coated with GCA-chitosan oligosaccharide conjugate (GCOS). The GCA-NPs thus prepared showed prolonged intestinal retention time and good GIT stability due to the presence of chitosan oligosaccharide (COS) and enhanced active transportation via intestinal apical sodium-dependent bile acid transporter (ASBT) due to the presence of GCA. GCA-NPs also efficiently inhibited intestinal P-gp induced by Qu. PTX-loaded GCA-NPs (PTX@GCA-NPs) had a particle size of 84 nm and an entrapment efficiency of 98% with good stability. As a result, the oral bioavailability of PTX was increased 19-fold compared to that of oral Taxol^® at the same dose. Oral PTX@GCA-NPs displayed superior antitumor efficacy and better safety than Taxol^® when administered intravenously.

CONCLUSIONS

Our novel drug delivery system showed remarkable efficacy in overcoming multiple limitations and is a promising carrier for oral delivery of multiple drugs, which addresses several challenges in oral delivery in the clinical context.

Effectiveness of idebenone nanorod formulations in the treatment of Alzheimer's disease

Idebenone (IDB) has demonstrated the potential to treat mitochondrial and neurodegenerative diseases, including Alzheimer's disease (AD). However, its therapeutic effects are compromised by poor compliance due to low bioavailability. The objective of this study is to fabricate IDB nanorods (IDBNRs) to improve oral bioavailability and increase concentrations in the brain in order to enhance therapeutic effects of IDB in the treatment of AD. IDBNRs showed desired sizes and rod-shaped morphologies. The release rate and the antioxidant activity of IDBNRs were improved relative to other delivery routes. The plasma and brain concentrations were enhanced due to rapid release into the systemic circulation. In behavioral tests, mice treated orally with IDBNRs showed amelioration of AD-induced impairment of learning and memory. Thus, because of improved efficiency of drug delivery, doses can be reduced, and the compliance and therapeutic experience of patients can be improved. IDBNRs may provide effective and convenient treatments for AD patients in the future.

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.

Angiopep-2-functionalized nanoparticles enhance transport of protein drugs across intestinal epithelia by self-regulation of targeted receptors

Ligand-modified nanoparticles (NPs) have been widely used in oral drug delivery systems to promote endocytosis on intestinal epithelia. However, their transcytosis across the intestinal epithelia is still limited. Except for complex intracellular trafficking, recycling again from the apical sides into the intestinal lumen of the endocytosed NPs cannot be ignored. In this study, we modified NP surfaces with angiopep-2 (ANG) that targeted the low-density lipoprotein receptor-related protein 1 (LRP-1) expressed on the intestine to increase both the apical endocytosis and basolateral transcytosis of NPs. Notably, our finding revealed that ANG NPs could increase the apical expression and further basolateral redistribution of LRP-1 on Caco-2 cells, thus generating an apical-to-basolateral absorption pattern. Because of the enhanced transcytosis, insulin loaded ANG NPs possessed much stronger absorption efficiency and induced maximal blood glucose reduction to 61.46% in diabetic rats. Self-regulating the distribution of receptors on polarized intestine cells to promote basolateral transcytosis will provide promising insights for the rational design of oral delivery systems of protein/peptide drugs.

Preparation of oridonin nanocrystals and study of their endocytosis and transcytosis behaviours on MDCK polarized epithelial cells

Context: Oridonin (ORI) has obvious anticancer effects, but its solubility is poor. Nanocrystal (NC) is a novel nano-drug delivery system for increasing bioavailability for ORI. However, the endocytosis and transcytosis behaviours of oridonin nanocrystals (ORI-NCs) through epithelial membrane are still unclear.Objectives: ORI-NCs were prepared and characterized. The in vitro cytotoxicity and endocytosis and transcytosis process on Madin-Darby canine kidney (MDCK) monolayer were investigated.Materials and methods: Anti-solvent precipitation method was adopted in preparation of ORI-NCs. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were adopted to explore crystallography of ORI-NCs. Sulforhodamine B (SRB) method was used to test the inhibition effect on proliferation of MDCK cells. Quantitative analysis by HPLC was performed to study the endocytosis and transcytosis of ORI-NCs and ORI bulk drug, and the process was observed by confocal laser spectrum microscopy (CLSM) and flow cytometry.Results: The particle size of ORI-NCs was about 274 nm. The crystallography form of ORI was not changed after prepared into NCs. The dissolution rate of ORI-NCs was higher than pure ORI in 120 min. At higher concentrations (34, 84 and 135 μg/mL), ORI-NCs significantly reduced the cell viability compared with free ORI (p < 0.05, p < 0.01). ORI-NCs demonstrated higher endocytosis in MDCK cells than free ORI (p < 0.01). In the transport process, ORI-NC was taken up into cells in an intact form, and excreted out from basolateral membrane of polarized epithelial cells in an intact form. The internalization and transmembrane amount increased as a function of time.Conclusions: ORI-NCs transported through the MDCK monolayers in an intact form.

Preparation of parenteral nanocrystal suspensions of etoposide from the excipient free dry state of the drug to enhance in vivo antitumoral properties

Nanoparticle technology in cancer chemotherapy is a promising approach to enhance active ingredient pharmacology and pharmacodynamics. Indeed, drug nanoparticles display various assets such as extended blood lifespan, high drug loading and reduced cytotoxicity leading to better drug compliance. In this context, organic nanocrystal suspensions for pharmaceutical use have been developed in the past ten years. Nanocrystals offer new possibilities by combining the nanoformulation features with the properties of solid dispersed therapeutic ingredients including (i) high loading of the active ingredient, (ii) its bioavailability improvement, and (iii) reduced drug systemic cytotoxicity. However, surprisingly, no antitumoral drug has been marketed as a nanocrystal suspension until now. Etoposide, which is largely used as an anti-cancerous agent against testicular, ovarian, small cell lung, colon and breast cancer in its liquid dosage form, has been selected to develop injectable nanocrystal suspensions designed to be transferred to the clinic. The aim of the present work is to provide optimized formulations for nanostructured etoposide solutions and validate by means of in vitro and in vivo evaluations the efficiency of this multiphase system. Indeed, the etoposide formulated as a nanosuspension by a bottom-up approach showed higher blood life span, reduced tumor growth and higher tolerance in a murine carcinoma cancer model. The results obtained are promising for future clinical evaluation of these etoposide nanosuspensions.

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.

Further Enhancement in Intestinal Absorption of Paclitaxel by Using Transferrin-Modified Paclitaxel Nanocrystals

The intestinal epithelium is considered to be a major obstacle to the gastrointestinal administration for water-insoluble drugs. To enhance the intestinal absorption of paclitaxel by improving its solubility and overcoming the intestinal epithelium barrier, transferrin-modified paclitaxel nanocrystals were prepared based on the specific transferrin receptor expressed on the apical membrane of the intestinal epithelium and examined to exhibit a mean size of around 178 nm, a rod-like morphology, a sustained release property, and an enhanced in vitro antitumor effect. The in situ intestinal perfusion study proved that the intestinal absorption of transferrin-modified paclitaxel nanocrystals was remarkably enhanced compared with that of Taxol and unmodified paclitaxel nanocrystals, which was further evidenced by the result of pharmacokinetic study. Their transcytosis pathway and intracellular trafficking track were disclosed using Caco-2 cell monolayers. The transcytosis of transferrin-modified paclitaxel nanocrystals and unmodified paclitaxel nanocrystals was principally mediated by clathrin and lipid rafts. The colocalization of both paclitaxel nanocrystals with the organelles observed under confocal microscopy suggested that the late endosomes, lysosomes, ER, and Golgi apparatus played a part in the transcellular transport of both paclitaxel nanocrystals during their transcytosis. Therefore, the designed transferrin-modified drug nanocrystals might have a great potential in the enhancement of intestinal absorption of water-insoluble drugs.

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

Nanotechniques show significant merits in terms of improving the oral bioavailability of poorly water-soluble drugs. However, the mechanisms behind are not clear yet. For instance, what is the contribution of free drug released during nanogranule transcytosis, as well as the impact of drug transporter and chylomicron? To address these issues, sorafenib nanogranules (SFN-NGs) were prepared as model by the high-gravity antisolvent precipitation method which approaches to practical mass production. Then, a multiaspect study on the transcytosis mechanism of SFN-NGs was conducted in Caco-2 cells and rats, including paracellular transport, endocytosis, intracellular trafficking, transmembrane pathway, as well as the involvement of transporter and chylomicron. Pharmacokinetics in rats demonstrated an obvious superiority of SFN-NGs in oral absorption and lymphatic transfer over SFN crude drugs. Different from free SFN, SFN-NGs could be internalized in cells in early stage by caveolin/lipid raft or clathrin induced endocytosis, and transported intactly through the polarized cell monolayers. While in late stage, transporter-mediated transport of free SFN began to play a vital role on the transmembrane of SFN-NGs. No paracellular transport of SFN-NGs was found, and the trafficking of SFN-NGs was affected by the pathway of ER-Golgi complexes. Surprisedly, the intracellular free SFN was the main source of transmembrane for SFN-NGs, which was entrapped into chylomicrons and then secreted into the extracellular space. Generally, the findings in current study may shed light on the absorption mechanism of oral nanoformulations.

The High Permeability of Nanocarriers Crossing the Enterocyte Layer by Regulation of the Surface Zonal Pattern

The intestinal epithelium is a major barrier that limits the absorption of oral drugs. The integrity of the epithelial tissue is a very important factor for preventing intestinal diseases. However, destabilization of the epithelium can promote the transportation of nanocarriers and increase the absorption of oral drugs. In our research, three different gold nanoparticles (GNPs) of the same size but with differing negative surface charge were designed and constructed as a model to determine the surface properties crucial for promoting absorptivity and bioavailability of the nanocarriers. The higher the ratio of surface carboxyl groups on GNPs, the higher capacity to induce transepithelial electrical resistance change and cell monolayer tight junction opening with higher permeability. The half carboxyl and half methyl surfaced GNPs displayed unique zonal surface patterns exhibited the greater ability to pass through intestinal epithelial cell layer but had a relatively small influence on tight junction distribution.

Fabrication of Fine Puerarin Nanocrystals by Box-Behnken Design to Enhance Intestinal Absorption

Puerarin is widely used as a therapeutic agent to cardiovascular diseases in clinics in China through intravenous administration, which could elicit adverse drug reactions caused by cosolvents, hindering its application in clinics. Therefore, the development of oral dosage is urgently needed. In our previous studies, we proved that the bioavailability of puerarin increased as particle sizes of nanocrystals decreased; however, we have not optimized the best process parameters for nanocrystals. In this study, we aim to fabricate fine nanocrystals (with smallest particle size) by Box-Behnken design and study the intestinal permeability of puerarin and its nanocrystals via employing everted gut sac model and in situ perfusion model. The results showed that the Box-Behnken design could be used to optimize the producing parameters of puerarin nanocrystals, and the particle sizes of fine nanocrystals were about 20 nm. Results of everted gut sacs showed that the polyvinylpyrrolidone (PVP) and verapamil had no influence on the absorption of puerarin and nanocrystals, and the nanocrystals could increase the P_app of puerarin for 2.2-, 2.9-, and 2.9-folds, respectively, in duodenum, jejunum, and ileum. Enhanced Ka and Peff were observed on the nanocrystal group, compared with puerarin, and PVP and verapamil had no influence on the absorption of nanocrystals, while the absorption of puerarin was influenced by P-gp efflux. Combining the results mentioned above, we can conclude that the Box-Behnken design benefits the optimization for preparation of nanocrystals, and the nanocrystals could enhance the intestinal absorption of puerarin by enhanced permeability and inhibited P-gp efflux.

A quantitative assessment of the dynamic modification of lipid-DNA probes on live cell membranes

Synthetic lipid-DNA probes have recently attracted much attention for cell membrane analysis, transmembrane signal transduction, and regulating intercellular networks. These lipid-DNA probes can spontaneously insert onto plasma membranes simply after incubation. The highly precise and controllable DNA interactions have further allowed the programmable manipulation of these membrane-anchored functional probes. However, we still have quite limited understanding of how these lipid-DNA probes interact with cell membranes and also what parameters determine this process. In this study, we have systematically studied the dynamic process of cell membrane modification with a group of lipid-DNA probes. Our results indicated that the hydrophobicity of the lipid-DNA probes is strongly correlated with their membrane insertion and departure rates. Most cell membrane insertion stems from the monomeric form of probes, rather than the aggregates. Lipid-DNA probes can be removed from cell membranes through either endocytosis or direct outflow into the solution. As a result, long-term probe modifications on cell membranes can be realized in the presence of excess probes in the solution and/or endocytosis inhibitors. For the first time, we have successfully improved the membrane persistence of lipid-DNA probes to more than 24 h. Our quantitative data have dramatically improved our understanding of how lipid-DNA probes dynamically interact with cell membranes. These results can be further used to allow a broad range of applications of lipid-DNA probes for cell membrane analysis and regulation.

Gradient Redox-Responsive and Two-Stage Rocket-Mimetic Drug Delivery System for Improved Tumor Accumulation and Safe Chemotherapy

Recent drug delivery nanosystems for cancer treatment still suffer from the poor tumor accumulation and low therapeutic efficacy due to the complex in vivo biological barriers. To resolve these problems, in this work, a novel gradient redox-responsive and two-stage rocket-mimetic drug nanocarrier is designed and constructed for improved tumor accumulation and safe chemotherapy. The nanocarrier is constructed on the basis of the disulfide-doped organosilica-micellar hybrid nanoparticles and the following dual-functional modification with disulfide-bonded polyethylene glycol (PEG) and amido-bonded polyethylenimine (PEI). First, prolonged circulation duration in the bloodstream is guaranteed due to the shielding of the outer PEG chains. Once the nanocarrier accumulates at the tumoral extracellular microenvironment with low glutathione (GSH) concentrations, the first-stage redox-responsive behavior with the separation of PEG and the exposure of PEI is triggered, leading to the improved tumor accumulation and cellular internalization. Furthermore, with their endocytosis by tumor cells, a high concentration of GSH induces the second-stage redox-responsiveness with the degradation of silsesquioxane framework and the release of the encapsulated drugs. As a result, the rocket-mimetic drug carrier displays longer circulation duration in the bloodstream, higher tumor accumulation capability, and improved antitumor efficacy (which is 2.5 times higher than that with inseparable PEG). It is envisioned that the rocket-mimetic strategy can provide new solutions for improving tumor accumulation and safety of nanocarriers in further cancer chemotherapy.

Fabrication of ultra-small nanocrystals by formation of hydrogen bonds: In vitro and in vivo evaluation

Poor water solubility and low bioavailability hinder the clinical application of about 70% of newly synthesized compounds. Nanocrystal technology has become a preferred way to improve bioavailability by improving solubility. However, it remains challenging to produce nanocrystals with ultra-small particle sizes to further enhance the extent of bioavailability. Herein, we constructed ultra-small puerarin nanocrystals (Pue-NCs) (20-40 nm) via formation of hydrogen bond during HPH. We confirmed the formation of hydrogen bonds by ¹H NMR and FTIR, and observed the distribution of polymer chains by SEM and TEM. The absorption mechanisms were studied in Caco-2 cell monolayers, and the results showed that the major transport mechanism for puerarin was passive diffusion, meanwhile, for Pue-NCs, the passive transport and micropinocytosis-mediated endocytosis coexisted. The absolute bioavailability of Pue-NCs was 35.28%, which was 11.54 folds compared to that of puerarin. Therapeutic equivalence was demonstrated between Pue-NCs and puerarin injection at 50 mg/kg and 15 mg/kg, respectively, in isoproterenol-induced myocardial ischemia model. This study provides a novel strategy for preparing ultra-small nanocrystals by HPH to increase bioavailability of poorly soluble drugs.

Towards more accurate bioimaging of drug nanocarriers: turning aggregation-caused quenching into a useful tool

One of the current challenges in the monitoring of drug nanocarriers lies in the difficulties in discriminating the carrier-bound signals from the bulk signals of probes. Environment-responsive probes that enable signal switching are making steps towards a solution to this problem. Aggregation-caused quenching (ACQ), a phenomenon generally regarded as unfavorable in bioimaging, has turned out to be a promising characteristic for achieving environment-responsiveness and eliminating free-probe interference. So-called ACQ probes emit fluorescence when dispersed molecularly within the carrier matrix but quench immediately and absolutely once they are released into the ambient aqueous environment upon the degradation of the nanocarriers. Therefore, the fluorescence observed represents integral nanocarriers. Based on this rationale, the in vivo fates of various nanocarriers have been explored using live imaging equipment, with very interesting findings revealing the role of the particles. The current applications are however restricted to nanocarriers with highly hydrophobic matrices (lipid or polyester nanoparticles) or with a hydrophobic core-hydrophilic shell structure (micelles). The ACQ-based bioimaging strategy is emerging as a promising tool to achieve more accurate bioimaging of drug nanocarriers. This review article provides an overview of the ACQ phenomenon and the rationale for and examples of applications, as well as the limitations of the ACQ-based strategy, with a focus on improving the accuracy of bioimaging of nanoparticles.

Intestinal Mucin Induces More Endocytosis but Less Transcytosis of Nanoparticles across Enterocytes by Triggering Nanoclustering and Strengthening the Retrograde Pathway

Mucus, which is secreted by the goblet cells of enterocytes, constitutes the first obstacle encountered for the intestinal absorption of nanomedicines. For decades, mucus has simply been regarded as a physical barrier that hinders the permeation and absorption of drugs, because of its high viscosity and reticular structure, whereas the interaction of mucus ingredients with nanomedicines is usually neglected. It is unclear whether glycoproteins, as the main components of mucus, interact with nanomedicines. We also do not know how the potential interaction affects the subsequent transportation of nanomedicines through the intestinal epithelium. In this study, mucin as the key element of mucus was investigated to characterize the interaction of nanomedicines with mucus. PEG-modified gold nanoparticles (PGNPs) were fabricated as model nanoparticles. Mucin was found to adhere to the nanoparticle surface to form a corona structure and induce the clustering of PGNPs by joining particles together, demonstrating the interaction between mucin and PGNPs. In addition, two intestinal epithelia, Caco-2 (non- mucus secretion) and HT-29 (high mucus secretion), were compared to evaluate the influence of mucin on the cellular interaction of PGNPs. Amazingly, mucin altered the trafficking characteristic of PGNPs in intestinal epithelium. Both in vitro and in vivo investigations demonstrated more nanoparticles being internalized by cells due to the mucin coverage. However, mucin induced a significant reduction in the transcytosis of PGNPs across epithelial monolayers. The mechanism exploration further revealed that the "more endocytosis but less transcytosis (MELT)" effect was mainly attributed to the strengthened retrograde pathway in which more PGNPs were transported to Golgi apparatus and exocytosed back to the apical but not the basolateral side of the epithelial monolayers. The "MELT" effect endowed mucin with duality in the nanoparticle transportation. Therefore, the rational regulation based on the "MELT" effect will provide new insight into overcoming the mucus obstacle as a barrier and enhancing the oral absorption rate of nanomedicines.

Study on orally delivered paclitaxel nanocrystals: modification, characterization and activity in the gastrointestinal tract

Drug nanocrystals (NCs) can improve the solubility and bioavailability of insoluble drugs for oral administration. However, the biocompatibility and mechanisms of transmittance of drug NCs through the intestinal epithelial tissue are still not well understood. In this work, the physico-chemical properties and interactions with biomolecules in oral delivery pathways, as well as the transmittance through mimical intestinal epithelial cells, of NCs of paclitaxel (PTX) are investigated. PTX was previously demonstrated to be an effective anti-cancer drug. It is found that maximum 1% (w/v) poly(styrenesulfonate) is sufficient to keep PTX NCs monodisperse in varied biological environments and presents no significant interaction with extracellular biomolecules for at least 24 h. The concentration of PTX NCs is kept carefully controlled to avoid serious toxicity to cells (10 µg ml^-1 in our experiments but this also depends on NC size). The transmittance of PTX NCs through mimical intestinal epithelial reached 25% in 6 h, demonstrating its comparatively high oral bioavailability in the human body. This work demonstrates the great potential of PTX NC treated in oral delivery.

Drug nanocrystals for cancer therapy

Drug nanocrystals (NCs) with fascinating physicochemical properties have attracted great attention in drug delivery. High drug-loading efficiency, great structural stability, steady dissolution, and long circulation time are a few examples of these properties, which makes drug NCs an excellent formulation for efficient cancer therapy. In the last two decades, there are a lot of hydrophobic or lipophilic drugs, such as paclitaxel (PTX), camptothecin (CPT), thymectacin, busulfan, cyclosporin A, 2-devinyl-2-(1-hexyloxyethyl) pyropheophorbide (HPPH), and so on, which have been formulated into drug NCs for cancer therapy. In this review, we summarized the recent advances in drug NCs-based cancer treatment. So far, there are main three methods to synthesize drug NCs, including top-down, bottom-up, and combination methods. The characterization methods of drug NCs were also elaborated. Furthermore, the applications and mechanisms of drug NCs were introduced by their administration routes. At the end, we gave a brief conclusion and discussed the future perspectives of drug NCs in cancer therapy. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.