Enhanced transport of nanocage stabilized pure nanodrug across intestinal epithelial barrier mimicking Listeria monocytogenes

Transcytosis: an effective mechanism to enhance nanoparticle extravasation and infiltration through biological barriers

Nanoparticles (NPs)1have been explored as drugs carriers for treating tumors and central nervous system (CNS)2diseases and for oral administration. However, they lack satisfactory clinical efficacy due to poor extravasation and infiltration through biological barriers to target tissues. Most clinical antitumor NPs have been designed based on enhanced permeability and retention effects which are insufficient and heterogeneous in human tumors. The tight junctions33TJs: tight junctionsof the blood-brain barrier44BBB: blood-brain barrierand the small intestinal epithelium severely impede NPs from being transported into the CNS and blood circulation, respectively. By contrast, transcytosis enables NPs to bypass these physiological barriers and enhances their infiltration into target tissues by active transport. Here, we systematically review the mechanisms and putative application of NP transcytosis for targeting tumor and CNS tissues, explore oral NP administration, and propose future research directions in the field of NP transcytosis.

Transepithelial transport of nanoparticles in oral drug delivery: From the perspective of surface and holistic property modulation

Despite the promising prospects of nanoparticles in oral drug delivery, the process of oral administration involves a complex transportation pathway that includes cellular uptake, intracellular trafficking, and exocytosis by intestinal epithelial cells, which are necessary steps for nanoparticles to enter the bloodstream and exert therapeutic effects. Current researchers have identified several crucial factors that regulate the interaction between nanoparticles and intestinal epithelial cells, including surface properties such as ligand modification, surface charge, hydrophilicity/hydrophobicity, intestinal protein corona formation, as well as holistic properties like particle size, shape, and rigidity. Understanding these properties is essential for enhancing transepithelial transport efficiency and designing effective oral drug delivery systems. Therefore, this review provides a comprehensive overview of the surface and holistic properties that influence the transepithelial transport of nanoparticles, elucidating the underlying principles governing their impact on transepithelial transport. The review also outlines the chosen of parameters to be considered for the subsequent design of oral drug delivery systems.

Bioactive Molecules Delivery through Ferritin Nanoparticles: Sum Up of Current Loading Methods

Ferritin (Ft) is a protein with a peculiar three-dimensional architecture. It is characterized by a hollow cage structure and is responsible for iron storage and detoxification in almost all living organisms. It has attracted the interest of the scientific community thanks to its appealing features, such as its nano size, thermal and pH stability, ease of functionalization, and low cost for large-scale production. Together with high storage capacity, these properties qualify Ft as a promising nanocarrier for the development of delivery systems for numerous types of biologically active molecules. In this paper, we introduce the basic structural and functional aspects of the protein, and summarize the methods employed to load bioactive molecules within the ferritin nanocage.

Oral targeted drug delivery to post-gastrointestinal sites

As an essential branch of targeted drug delivery, oral targeted delivery is attracting growing attention in recent years. In addition to site-specific delivery for the treatment of locoregional diseases in the gastrointestinal tract (GIT), oral targeted delivery to remote sites beyond the GIT emerges as a cutting-edge research topic. This review aims to provide an overview of the fundamental concepts and most recent advances in this field. Owing to the physiological barriers existing in the GIT, carrier systems should be transported across the enteric epithelia to target remote sites. Recently, pioneer investigations have validated the transport of intact micro- or nanocarriers across gastrointestinal barriers and subsequently to various distal organs and tissues. The microfold (M) cell pathway is the leading mechanism underlying the oral absorption of particulates, but the contribution of the transcellular and paracellular pathways should not be neglected either. In addition to well-acknowledged physicochemical and biological factors, the formation of a protein corona may also influence the biological fate of carrier systems. Although in an early stage of conceptualization, oral targeted delivery to remote diseases has demonstrated promising potential for the treatment of inflammation, tumors, and diseases inflicting the lymphatic and mononuclear phagocytosis systems.

Particle Integrity and Size Effect on the Journey of Polymeric Nanocarriers in Zebrafish Model and the Correlation with Mice

Polymeric nanocarriers have high biocompatibility for potential drug delivery applications. After entering bloodstream, nanocarriers will circulate, interact with proteins, dissociate, or be cleared by reticuloendothelial system. Zebrafish as a visual animal model, can serve as a tool for screening nanomedicines and monitoring nanocarrier behaviors in vivo. However, a comprehensive correlation between zebrafish and rodent models is currently deficient. Here, different-sized poly(caprolactone) nanocarriers (PCL NCs) are fabricated with or without PEGylation to investigate correlation between zebrafish and mice regarding their biofate via Förster resonance energy transfer technique. Results show that PEGylated PCL NCs have higher integrity in both zebrafish and mice. Small PEG-PCL NCs have longer circulation, while large PEG-PCL NCs have dramatically higher macrophage sequestration in zebrafish and mice spleen, leading to poor circulation. PCL NCs dissociate rapidly with less macrophage sequestration. Moreover, in 7 days postfertilization (dpf) zebrafish, polymers are eliminated via hepatobiliary pathway, which is not fully functional at earlier stages of development. The effects of nanocarrier integrity on macrophage sequestration in zebrafish and good correlation with mice spleen are pioneered to be demonstrated. The findings suggest that 7 dpf zebrafish are suitable as an in vivo screening model of nanocarriers and predict their biofate in rodents.

An ex Vivo Model Enables Systematic Investigation of the Intestinal Absorption and Transcytosis of Oral Particulate Nanocarriers

Nanoparticulate formulations are being developed toward enhancing the bioavailability of orally administrated biologics. However, the processes mediating particulate carriers' intestinal uptake and transport remains to be fully elucidated. Herein, an optical clearing-based whole tissue mount/imaging strategy was developed to enable high quality microscopic imaging of intestinal specimens. It enabled the distribution of nanoparticles within intestinal villi to be quantitatively analyzed at a cellular level. Two-hundred and fifty nm fluorescent polystyrene nanoparticles were modified with polyethylene glycol (PEG), Concanavalin A (ConA), and pectin to yield mucopenetrating, enterocyte targeting, and mucoadhesive model nanocarriers, respectively. Introducing ConA on the PEGylated nanoparticles significantly increased their uptake in the intestinal epithelium (∼4.16 fold for 200 nm nanoparticle and ∼2.88 fold for 50 nm nanoparticles at 2 h). Moreover, enterocyte targeting mediated the trans-epithelial translocation of 50 nm nanoparticles more efficiently than that of the 200 nm nanoparticles. This new approach provides an efficient methodology to obtain detailed insight into the transcytotic activity of enterocytes as well as the barrier function of the constitutive intestinal mucus. It can be applied to guide the rational design of particulate formulations for more efficient oral biologics delivery.

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.

Molecular and cellular cues governing nanomaterial-mucosae interactions: from nanomedicine to nanotoxicology

Mucosal tissues constitute the largest interface between the body and the surrounding environment and they regulate the access of molecules, supramolecular structures, particulate matter, and pathogens into it. All mucosae are characterized by an outer mucus layer that protects the underlying cells from physicochemical, biological and mechanical insults, a mono-layered or stratified epithelium that forms tight junctions and controls the selective transport of solutes across it and associated lymphoid tissues that play a sentinel role. Mucus is a gel-like material comprised mainly of the glycoprotein mucin and water and it displays both hydrophilic and hydrophobic domains, a net negative charge, and high porosity and pore interconnectivity, providing an efficient barrier for the absorption of therapeutic agents. To prolong the residence time, absorption and bioavailability of a broad spectrum of active compounds upon mucosal administration, mucus-penetrating and mucoadhesive particles have been designed by tuning the chemical composition, the size, the density, and the surface properties. The benefits of utilizing nanomaterials that interact intimately with mucosae by different mechanisms in the nanomedicine field have been extensively reported. To ensure the safety of these nanosystems, their compatibility is evaluated in vitro and in vivo in preclinical and clinical trials. Conversely, there is a growing concern about the toxicity of nanomaterials dispersed in air and water effluents that unintentionally come into contact with the airways and the gastrointestinal tract. Thus, deep understanding of the key nanomaterial properties that govern the interplay with mucus and tissues is crucial for the rational design of more efficient drug delivery nanosystems (nanomedicine) and to anticipate the fate and side-effects of nanoparticulate matter upon acute or chronic exposure (nanotoxicology). This review initially overviews the complex structural features of mucosal tissues, including the structure of mucus, the epithelial barrier, the mucosal-associated lymphatic tissues and microbiota. Then, the most relevant investigations attempting to identify and validate the key particle features that govern nanomaterial-mucosa interactions and that are relevant in both nanomedicine and nanotoxicology are discussed in a holistic manner. Finally, the most popular experimental techniques and the incipient use of mathematical and computational models to characterize these interactions are described.

In vivo labeling of epithelial cell-associated antigen passages in the murine intestine

The intestinal immune system samples luminal contents to induce adaptive immune responses that include tolerance in the steady state and protective immunity during infection. How luminal substances are delivered to the immune system has not been fully investigated. Goblet cells have an important role in this process by delivering luminal substances to the immune system through the formation of goblet cell-associated antigen passages (GAPs). Soluble antigens in the intestinal lumen are transported across the epithelium transcellularly through GAPs and delivered to dendritic cells for presentation to T cells and induction of immune responses. GAPs can be identified and quantified by using the ability of GAP-forming goblet cells to take up fluorescently labeled dextran. Here, we describe a method to visualize GAPs and other cells that have the capacity to take up luminal substances by intraluminal injection of fluorescent dextran in mice under anesthesia, tissue sectioning for slide preparation and imaging with fluorescence microscopy. In contrast to in vivo two-photon imaging previously used to identify GAPs, this technique is not limited by anatomical constraints and can be used to visualize GAP formation throughout the length of the intestine. In addition, this method can be combined with common immunohistochemistry protocols to visualize other cell types. This approach can be used to compare GAP formation following different treatments or changes to the luminal environment and to uncover how sampling of luminal substances is altered in pathophysiological conditions. This protocol requires 8 working hours over 2-3 d to be completed.

Functional lipid polymeric nanoparticles for oral drug delivery: Rapid mucus penetration and improved cell entry and cellular transport

To improve Biopharmaceutics Classification System class IV drug bioavailability, mucus and underlying intestinal epithelial barriers must be overcome. Hydrophilic nanoparticle coatings may hinder cellular uptake and transport. We integrated hydrophilic, detachable poly(N-(2-hydroxypropyl) methacrylamide) with vitamin B12-modified chitosan into lipid polymeric nanoparticles (H/VC-LPNs) to enhance mucus penetration, intracellular uptake, and transepithelial absorption. Multiple particle tracking revealed accelerated mucus diffusion into porcine mucus in vitro. The nanoparticles increased uptake and intracellular distribution in Caco-2 cells, which may involve intrinsic factor receptor-mediated endocytosis and intercellular tight junctions. Integration of improved mucus penetration and intracellular absorption was confirmed by in vitro internalization kinetics in HT29-MTX/Caco-2 co-cultures and in vivo distribution, transport, and mouse Peyer's patch absorption. H/VC-LPNs substantially increased curcumin bioavailability in rats. A nanocarrier with a dissociable shell, receptor-mediated intracellular penetration, and paracellular transport may be promising for oral curcumin delivery. This study identified the key factors involved in oral bioavailability enhancement.

Enhanced anti-colon cancer efficacy of 5-fluorouracil by epigallocatechin-3- gallate co-loaded in wheat germ agglutinin-conjugated nanoparticles

Colon adenocarcinoma is the third most common cause of cancer-related deaths worldwide owing to its aggressive nature. Here, we developed a novel oral drug delivery system (DDS) that comprised active targeted nanoparticles made from gelatin and chitosan (non-toxic polymers). The nanoparticles were fabricated using a complex coacervation method, which was accompanied by conjugation of wheat germ agglutinin (WGA) onto their surface by glutaraldehyde cross-linking. Specifically, we integrated 5-fluorouracil (5-FU), the first-line treatment agent against colon cancer, and (-)-epigallocatechin-3-gallate (EGCG), which inhibits tumor growth via anti-angiogenesis and apoptosis-inducing effects, into the nanoparticles, named WGA-EF-NP. The 5-FU and EGCG co-loaded nanoparticles showed sustained drug release, enhanced cellular uptake, and longer circulation time. WGA-EF-NP exhibited superior anti-tumor activity and pro-apoptotic efficacy compared to the drugs and nanoparticles without WGA decoration owing to better bioavailability and longer circulation time in vivo. Thus, WGA-EF-NP shows promise as a DDS for enhanced efficacy against colon cancer.

Hybrid drug nanocrystals

Nanocrystals show promise to deliver poorly water-soluble drugs to yield systemic exposure. However, our knowledge regarding the in vivo fate of nanocrystals is in its infancy, as nanocrystallization is simply viewed as an approach to enhance the dissolution of drug crystals. The dying crystal phenomenon inspired the development of hybrid nanocrystals by physically embedding fluorophores into the crystal lattice. This approach achieved concurrent therapy and bioimaging and is well-established to study pharmacokinetics and nanocrystal dissolution in vivo. Nanocrystals also offer the advantage of long-term durability in the body for interacting with biological tissues and cells. This review introduces the hybrid nanocrystal technique, including the theoretical concepts, preparation, and applications. We also discuss the latest development in self-discriminative hybrid nanocrystals utilizing environment-responsive probes. This review will stimulate further development and application of nanocrystal-based drug delivery systems for theranostic strategies.

Intestinal Macromolecular Transport Supporting Adaptive Immunity

The gastrointestinal tract performs opposing functions of nutrient absorption, barrier maintenance, and the delivery of luminal substances for the appropriate induction of tolerogenic or protective adaptive immunity. The single-layer epithelium lining the gastrointestinal tract is central to each of these functions by facilitating the uptake and processing of nutrients, providing a physical and chemical barrier to potential pathogens, and delivering macromolecular substances to the immune system to initiate adaptive immune responses. Specific transport mechanisms allow nutrient uptake and the delivery of macromolecules to the immune system while maintaining the epithelial barrier. This review examines historical observations supporting macromolecular transport by the intestinal epithelium, recent insights into the transport of luminal macromolecules to promote adaptive immunity, and how this process is regulated to promote appropriate immune responses. Understanding how luminal macromolecules are delivered to the immune system and how this is regulated may provide insight into the pathophysiology of inflammatory diseases of the gastrointestinal tract and potential preventative or therapeutic strategies.

Fenofibrate Nanocrystals Embedded in Oral Strip-Films for Bioavailability Enhancement

The aim of the present study was to make a fenofibrate (FNB) nanocrystal (NC) by wet media milling, characterizations and formulates into oral strip-films (OSFs). Mechanical properties, redispersion study, and solid-state characterizations results suggested that reduction of drug crystal size at nanoscale and incorporation into OSFs does not affect the solid-state properties of the drug. In vitro dissolution kinetics showed enhanced dissolution rate was easily manipulated by changing the thickness of the OSF. In situ UV-imaging was used to monitor drug dissolution qualitatively and quantitatively in real time. Results confirm that the intrinsic dissolution rates and surface drug concentration measured with this device were in agreement with the USP-IV dissolution profiles. In vivo pharmacokinetics in rabbits showed a significant difference in the pharmacokinetics parameter (1.4 fold increase bioavailability) of FNB NC-loaded OSFs as compared to the marketed formulation “Tricor” and as-received (pristine) drug. This approach of drug nanocrystallization and incorporation into OSFs may have significant applications in cost-effective tools for bioavailability enhancement of FNB.

Nanocaged platforms: modification, drug delivery and nanotoxicity. Opening synthetic cages to release the tiger

Nanocages (NCs) have emerged as a new class of drug-carriers, with a wide range of possibilities in multi-modality medical treatments and theranostics. Nanocages can overcome such limitations as high toxicity caused by anti-cancer chemotherapy or by the nanocarrier itself, due to their unique characteristics. These properties consist of: (1) a high loading-capacity (spacious interior); (2) a porous structure (analogous to openings between the bars of the cage); (3) enabling smart release (a key to unlock the cage); and (4) a low likelihood of unfavorable immune responses (the outside of the cage is safe). In this review, we cover different classes of NC structures such as virus-like particles (VLPs), protein NCs, DNA NCs, supramolecular nanosystems, hybrid metal-organic NCs, gold NCs, carbon-based NCs and silica NCs. Moreover, NC-assisted drug delivery including modification methods, drug immobilization, active targeting, and stimulus-responsive release mechanisms are discussed, highlighting the advantages, disadvantages and challenges. Finally, translation of NCs into clinical applications, and an up-to-date assessment of the nanotoxicology considerations of NCs are presented.

The in vivo fate of nanocrystals

There has been significant research interest in, and development of, nanocrystals in recent years for the delivery of poorly water-soluble drugs via various routes. However, there is a common misinterpretation of nanocrystallization as an approach to modulate, and more specifically to enhance, the dissolution of drug crystals. Nevertheless, it is possible for nanocrystals to interact with biological tissues because nanocrystals can survive for a longer duration in vivo compared with solution counterparts. Therefore, understanding the in vivo fate of nanocrystals and determining its contribution to efficacy is of tremendous significance for optimizing the performance of nanocrystals. Here, we critically review the general hypotheses related to the in vivo fate of nanocrystals.

Nanoparticles for oral delivery: Design, evaluation and state-of-the-art

The oral route is a preferred method of drug administration, though achieving effective drug delivery and minimizing off-target side effects is often challenging. Formulation into nanoparticles can improve drug stability in the harsh gastrointestinal (GI) tract environment, providing opportunities for targeting specific sites in the GI tract, increasing drug solubility and bioavailability, and providing sustained release in the GI tract. However, the unique and diverse physiology throughout the GI tract, including wide variation in pH, mucus that varies in thickness and structure, numerous cell types, and various physiological functions are both a barrier to effective delivery and an opportunity for nanoparticle design. Here, nanoparticle design aspects to improve delivery to particular sites in the GI tract are discussed. We then review new methods for evaluating oral nanoparticle formulations, including a short commentary on data interpretation and translation. Finally, the state-of-the-art in preclinical targeted nanoparticle design is reviewed.

Advances in the transepithelial transport of nanoparticles

The intestinal epithelium represents a barrier to the delivery of nanoparticles (NPs). It prevents intact NPs from efficiently crossing the mucosa to access the circulation, thus limiting the successful application of NP-based oral drug delivery. Recent advances in nanotechnology have provided promising solutions to this challenge. This review describes the potential intestinal absorption pathways of NPs, including the transenterocytic pathway, paracellular pathway and M-cell-mediated pathway. NP properties that influence transcytosis are summarized; and the biodistribution of NPs after oral absorption is described and the future prospects of novel NPs are explored.