Glucan microparticles thickened with thermosensitive gels as potential carriers for oral delivery of insulin

Intestinal Lymphatic Biology, Drug Delivery, and Therapeutics: Current Status and Future Directions

Historically, the intestinal lymphatics were considered passive conduits for fluids, immune cells, dietary lipids, lipid soluble vitamins, and lipophilic drugs. Studies of intestinal lymphatic drug delivery in the late 20th century focused primarily on the drugs' physicochemical properties, especially high lipophilicity, that resulted in intestinal lymphatic transport. More recent discoveries have changed our traditional view by demonstrating that the lymphatics are active, plastic, and tissue-specific players in a range of biological and pathological processes, including within the intestine. These findings have, in turn, inspired exploration of lymph-specific therapies for a range of diseases, as well as the development of more sophisticated strategies to actively deliver drugs or vaccines to the intestinal lymph, including a range of nanotechnologies, lipid prodrugs, and lipid-conjugated materials that "hitchhike" onto lymphatic transport pathways. With the increasing development of novel therapeutics such as biologics, there has been interest in whether these therapeutics are absorbed and transported through intestinal lymph after oral administration. Here we review the current state of understanding of the anatomy and physiology of the gastrointestinal lymphatic system in health and disease, with a focus on aspects relevant to drug delivery. We summarize the current state-of-the-art approaches to deliver drugs and quantify their uptake into the intestinal lymphatic system. Finally, and excitingly, we discuss recent examples of significant pharmacokinetic and therapeutic benefits achieved via intestinal lymphatic drug delivery. We also propose approaches to advance the development and clinical application of intestinal lymphatic delivery strategies in the future. SIGNIFICANCE STATEMENT: This comprehensive review details the understanding of the anatomy and physiology of the intestinal lymphatic system in health and disease, with a focus on aspects relevant to drug delivery. It highlights current state-of-the-art approaches to deliver drugs to the intestinal lymphatics and the shift toward the use of these strategies to achieve pharmacokinetic and therapeutic benefits for patients.

β-Glucan-A promising immunocyte-targeting drug delivery vehicle: Superiority, applications and future prospects

Drug delivery technologies that could convert promising therapeutics into successful therapies have been under broad research for many years. Recently, β-glucans, natural-occurring polysaccharides extracted from many organism species such as yeast, fungi and bacteria, have attracted increasing attention to serve as drug delivery carriers. With their unique structure and innate immunocompetence, β-glucans are considered as promising carriers for targeting delivery especially when applied in the vaccine construction and oral administration of therapeutic agents. In this review, we focus on three types of β-glucans applied in the drug delivery system including yeast β-glucan, Schizophyllan and curdlan, highlighting the benefits of β-glucan based delivery system. We summarize how β-glucans as delivery vehicles have aided various therapeutics ranging from macromolecules including proteins, peptides and nucleic acids to small molecular drugs to reach desired cells or organs in terms of loading strategies. We also outline the challenges and future directions for developing the next generation of β-glucan based delivery systems.

β-Cyclodextrin/dialdehyde glucan-coated keratin nanoparticles for oral delivery of insulin

Successful oral insulin administration can considerably enhance the quality of life (QOL) of diabetes patients who must frequently take insulin injections. However, Oral insulin administration is seriously hampered by gastrointestinal enzymes, wide pH range, mucus and mucosal layers, which limit insulin oral bioavailability to ≤2 %. Herein, we developed a simple, inexpensive and safe dual β-cyclodextrin/dialdehyde glucan-coated keratin nanoparticle (β-CD-K-IN-DG). The resulted β-CD-K-IN-DG not only gave the ultra-high insulin loading (encapsulation efficiency (98.52 %)), but also protected insulin from acid and enzymatic degradation. This β-CD-K-IN-DG had a notable hypoglycemic effect, there was almost 80 % insulin release after 4 h of incubation under hyperglycemic conditions. Ex vivo results confirmed that β-CD-K-IN-DG possessed high mucus-penetration ability. Transepithelial transport and uptake mechanism studies revealed that bypass transport pathway and endocytosis promoted β-CD-K-IN-DG entered intestinal epithelial cells, thus increased the bioavailability of insulin (12.27 %). The improved stability of insulin during in vivo transport implied that β-CD-K-IN-DG might be a potential tool for the effective oral insulin administration.

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.

Glucans and applications in drug delivery

Glucan is a natural polysaccharide widely distributed in cereals and microorganisms that has various biological activities, including immunomodulatory, anti-infective, anti-inflammatory, and antitumor activities. In addition to wide applications in the broad fields of food, healthcare, and biomedicines, glucans hold promising potential as drug delivery carrier materials or ligands. Specifically, glucan microparticles or yeast cell wall particles are naturally enclosed vehicles with an interior cavity that can be exploited to carry and deliver drug payloads. The biological activities and targeting capacities of glucans depend largely on the recognition of glucan moieties by receptors such as dectin-1 and complement receptor 3, which are widely expressed on the cell membranes of mononuclear phagocytes, dendritic cells, neutrophils, and some lymphocytes. This review summarizes the chemical structures, sources, fundamental properties, extraction methods, and applications of these materials, with an emphasis on drug delivery. Glucans are utilized mainly as vaccine adjuvants, targeting ligands and as carrier materials for various drug entities. It is believed that glucans and glucan microparticles may be useful for the delivery of both small-molecule and macromolecular drugs, especially for potential treatment of immune-related diseases.

Polymeric nanoparticles (PNPs) for oral delivery of insulin

Successful oral insulin administration can considerably enhance the quality of life (QOL) of diabetes patients who must frequently take insulin injections. Oral insulin administration, on the other hand, is seriously hampered by gastrointestinal enzymes, wide pH range, mucus and mucosal layers, which limit insulin oral bioavailability to ≤ 2%. Therefore, a large number of technological solutions have been proposed to increase the oral bioavailability of insulin, in which polymeric nanoparticles (PNPs) are highly promising for oral insulin delivery. The recently published research articles chosen for this review are based on applications of PNPs with strong future potential in oral insulin delivery, and do not cover all related work. In this review, we will summarize the controlled release mechanisms of oral insulin delivery, latest oral insulin delivery applications of PNPs nanocarrier, challenges and prospect. This review will serve as a guide to the future investigators who wish to engineer and study PNPs as oral insulin delivery systems.

Bioinspired yeast-based β-glucan system for oral drug delivery

Oral drug delivery is the preferred route of drug administration for patients, especially those who need long-term medication. Recently, bioinspired drug delivery systems have emerged for the oral delivery of various therapeutics. Among them, the yeast-based β-glucan system is a novel and promising platform, for oral administration that can overcome the biological barriers of the harsh gastrointestinal environment. Remarkably, the yeast-based β-glucan system not only protects the drug through the harsh gastrointestinal environment but also achieves targeted therapeutic effects by specifically recognizing immune cells, especially macrophages. Otherwise, it exhibits immunomodulatory properties. Based on the pleasant characteristics of the yeast-based β-glucan system, they are widely used in various macrophage-related diseases for oral administration. In this review, we introduced the structure and function of yeast-based β-glucan. Subsequently, we further summarized the current preparation methods of yeast-based β-glucan carriers and the strategies for preparing yeast-based β-glucan drug delivery systems. In addition, we focus on discussing the applications of β-glucan drug delivery systems in various diseases. Finally, the current challenges and future perspectives of the β-glucan drug delivery system are introduced.

Serum and lymph pharmacokinetics of nilotinib delivered by yeast glucan particles per os

Nilotinib is a selective tyrosine-kinase inhibitor approved for the treatment of chronic myeloid leukemia. It is poorly soluble in aqueous media and has a low oral bioavailability. Nilotinib encapsulation into yeast glucan particles (GPs) was investigated in this work as a means of increasing bioavailability. The amorphization of nilotinib in GPs resulted in an increased dissolution rate, which was confirmed by in vitro experiments using biorelevant dissolution media. Simultaneously, GPs containing nilotinib were effectively taken up by macrophages, which was quantified in vitro on cell cultures. The overall oral bioavailability in a rat model was approximately 39 % for nilotinib delivered in a reference formulation (Tasigna) and was almost doubled when delivered in GPs. The contribution of glucan particles to the lymphatic transport of nilotinib was quantified. When delivered by GPs, cumulative nilotinib absorption via the lymphatic system increased by a factor of 10.8 compared to the reference, but still represented arelative bioavailability of only 1.12 %. The cumulative uptake of GPs in the lymph was found to be 0.54 mg after a single dose of 50 mg. Yeast glucan particles can therefore serve as a drug delivery vehicle with a dual function: dissolution rate enhancement by amorphization, and, to asmaller extent, lymphatic delivery due to macrophage uptake.

Recent Advances in Delivery Systems for Genetic and Other Novel Vaccines

Vaccination is one of the most successful and cost-effective prophylactic measures against diseases, especially infectious diseases including smallpox and polio. However, the development of effective prophylactic or therapeutic vaccines for other diseases such as cancer remains challenging. This is often due to the imprecise control of vaccine activity in vivo which leads to insufficient/inappropriate immune responses or short immune memory. The development of new vaccine types in recent decades has created the potential for improving the protective potency against these diseases. Genetic and subunit vaccines are two major categories of these emerging vaccines. Owing to their nature, they rely heavily on delivery systems with various functions, such as effective cargo protection, immunogenicity enhancement, targeted delivery, sustained release of antigens, selective activation of humoral and/or cellular immune responses against specific antigens, and reduced adverse effects. Therefore, vaccine delivery systems may significantly affect the final outcome of genetic and other novel vaccines and are vital for their development. This review introduces these studies based on their research emphasis on functional design or administration route optimization, presents recent progress, and discusses features of new vaccine delivery systems, providing an overview of this field.

Vesicles of yeast cell wall-sitagliptin to alleviate neuroinflammation in Alzheimer's disease

A cell-based drug delivery system based on yeast-cell wall loaded with sitagliptin, a drug with an anti-inflammatory effect, was developed to control neuroinflammation associated with Alzheimer's disease. The optimized nanoparticles had a spherical shape with a negative surface charge, and were shown to be less toxic than the carrier and sitagliptin. Moreover, the nanoparticles caused anti-inflammatory effects against tumor necrosis factor-alpha in mice model of neuroinflammation. The pharmacokinetics study showed the brain concentration of drug in the nanoparticles group was much higher than in the control group. To evaluate the effect of P-glycoprotein on brain entry of sitagliptin, the experiment was repeated with verapamil, as a P-glycoprotein inhibitor. Brain concentration of the nanoparticles group remained approximately unchanged, proving the "Trojan Horse" effect of the developed nanocarriers. The results are promising for using yeast-cell wall as a carrier for targeted delivery to immune cells for the management of inflammation.

β-1,3-d-Glucan based yeast cell wall system loaded emodin with dual-targeting layers for ulcerative colitis treatment

Herein, a β-1,3-d-glucan based microcarrier, yeast cell wall microparticles (YPs), was used to develop a food-source-based nano-in-micro oral delivery system for ulcerative colitis (UC) treatment. Briefly, lactoferrin (Lf), which targets intestinal epithelial cells, was used to encapsulate emodin (EMO) to form nanoparticles (EMO-NPs), and then loaded into YPs with the natural macrophages targeting ability, forming a final formula with two outer-inner targeting layers (EMO-NYPs). These dual-targeting strategy could enhance the dual-effects of EMO in anti-inflammatory and mucosal repair effects respectively. As expected, cell uptake assessment confirmed that EMO-NPs and EMO-NYPs could target on the Lf and dection-1 receptors on the membranes of Caco-2 cells and macrophages, respectively. Importantly, EMO-NYPs showed the best anti-UC effects compared to EMO-NPs and free EMO, by inhibiting NF-κB pathway to anti-inflammation and promoting intestinal mucosa repair via MLCK/pMLC2 pathway. The results show that EMO-NYPs are a promising food-based oral delivery system in anti-UC.

Influence of non-covalent interactions in dictating the polarity and mobility of charge carriers in a series of crystalline NDIs: a computational case study

Polycyclic aromatic compounds and their derivatives have emerged as potential molecular entities for air-stable n-type organic semiconductors. In particular, naphthalene diimide (NDI)-derived compounds stand out as one of the most promising classes of molecules that have been studied extensively. There have been a lot of debatable experimental reports on the OFET performance characteristics of some of these materials, which have not yet been resolved completely. Hence, the critical intrinsic aspect of the molecular materials during charge transport in a bulk crystalline state would be essential to categorise the potential candidates. As a case study, in this comprehensive computational approach, we investigated the structural and supramolecular organization in single crystals and the role of those aspects in the bulk carrier transport of a group of selected end-substituted NDI derivatives. A subtle alteration of the end group was observed to result in the modulation of the polarity of charge transport and the charge carrier mobility in the single crystalline state. The disparity is addressed by considering the electronic coupling of the transport states, symmetry of the frontier molecular orbitals and various non-covalent intermolecular interactions. We expect that the present study would benefit towards the rational designing of air-stable n-type organic molecular semiconductors for efficient electronic devices.

Evaluation of β-glucan particles as dual-function carriers for poorly soluble drugs

Yeast glucan particles are porous polysaccharide cell walls extracted from Saccharomyces cerevisiae. Being mildly immunogenic, they are efficiently phagocytosed and have therefore been proposed as possible vehicles for drug delivery. Using curcumin as a model poorly water-soluble drug, a systematic comparison of three different physical loading methods - incipient wetness impregnation, slurry evaporation, and spray drying - was carried out and their influence on the particle morphology, encapsulation efficiency, amorphous drug content and release kinetics was evaluated. It was found that yeast glucan particles can contain up to 30% wt. of curcumin in the amorphous form when prepared by slurry evaporation. The dissolution of curcumin from glucan particles lead to a supersaturated solution in asimilar way as amorphous solid dispersions do, despite the fact that glucan particles themselves do not dissolve. Bi-phasic dissolution tests revealed up to 4-fold acceleration of curcumin dissolution rate from amorphous glucan particles compared to its crystalline form. Crucially, glucan particles were shown to retain the ability to be recognised and phagocytosed even after drug encapsulation.

Oral delivery of proteins and peptides: Challenges, status quo and future perspectives

Proteins and peptides (PPs) have gradually become more attractive therapeutic molecules than small molecular drugs due to their high selectivity and efficacy, but fewer side effects. Owing to the poor stability and limited permeability through gastrointestinal (GI) tract and epithelia, the therapeutic PPs are usually administered by parenteral route. Given the big demand for oral administration in clinical use, a variety of researches focused on developing new technologies to overcome GI barriers of PPs, such as enteric coating, enzyme inhibitors, permeation enhancers, nanoparticles, as well as intestinal microdevices. Some new technologies have been developed under clinical trials and even on the market. This review summarizes the history, the physiological barriers and the overcoming approaches, current clinical and preclinical technologies, and future prospects of oral delivery of PPs.

An update on oral drug delivery via intestinal lymphatic transport

Orally administered drug entities have to survive the harsh gastrointestinal environment, penetrate the enteric epithelia and circumvent hepatic metabolism before reaching the systemic circulation. Whereas the gastrointestinal stability can be well maintained by taking proper measures, hepatic metabolism presents as a formidable barrier to drugs suffering from first-pass metabolism. The pharmaceutical academia and industries are seeking alternative pathways for drug transport to circumvent problems associated with the portal pathway. Intestinal lymphatic transport is emerging as a promising pathway to this end. In this review, we intend to provide an updated overview on the rationale, strategies, factors and applications involved in intestinal lymphatic transport. There are mainly two pathways for peroral lymphatic transport-the chylomicron and the microfold cell pathways. The underlying mechanisms are being unraveled gradually and nowadays witness increasing research input and applications.

Yeast Cells in Microencapsulation. General Features and Controlling Factors of the Encapsulation Process

Besides their best-known uses in the food and fermentation industry, yeasts have also found application as microcapsules. In the encapsulation process, exogenous and most typically hydrophobic compounds diffuse and end up being passively entrapped in the cell body, and can be released upon application of appropriate stimuli. Yeast cells can be employed either living or dead, intact, permeabilized, or even emptied of all their original cytoplasmic contents. The main selling points of this set of encapsulation technologies, which to date has predominantly targeted food and-to a lesser extent-pharmaceutical applications, are the low cost, biodegradability and biocompatibility of the capsules, coupled to their sustainable origin (e.g., spent yeast from brewing). This review aims to provide a broad overview of the different kinds of yeast-based microcapsules and of the main physico-chemical characteristics that control the encapsulation process and its efficiency.

Utilization of PLGA nanoparticles in yeast cell wall particle system for oral targeted delivery of exenatide to improve its hypoglycemic efficacy

Oral delivery of exenatide (EXE), a high-efficiency therapeutic peptide, is urgently needed for long-term treatment of diabetes. In this study, a polylactide-co-glycoside (PLGA) nanoparticles (NPs) in yeast cell wall particle (YCWP) system was built to improve the intestinal absorption of EXE by efficient protection of EXE against gastrointestinal degradation and intestinal phagocytic cell targeted delivery. The EXE-loaded PLGA NPs were prepared by a double emulsion solvent diffusion method and exhibited a uniformly spherical appearance, a nano size (92.4 ± 4.6 nm) and a positive surface charge (+32.3 ± 3.8 mV). And then, the NPs were successfully loaded into the YCWPs by a solvent hydration - lyophilization cycle method to obtain the EXE-PLGA NPs @YCWPs, which was verified by scanning electron microscope and confocal laser scanning microscopy. An obvious sustained drug release and a reduced burst release were achieved by this nano-in-micro carrier. Moreover, the gastrointestinal stability of EXE in PLGA NPs @YCWPs was significantly higher than that in PLGA NPs in the simulated gastrointestinal environment, which were useful in enhancing the intestinal absorption of EXE. In biodistribution study, the EXE-PLGA NPs @YCWPs could quickly reached the root of the villi, and even partly entered the inner of the villi, especially in ileum and Peyer's patches. In vitro cell evaluation demonstrated an efficient β-glucan receptor mediated endocytosis and transport of EXE-PLGA NPs @YCWPs by the macrophage RAW 264.7 cells, suggesting a potential intestinal macrophage targeted absorptive pathway. The in vivo pharmacokinetic study showed a preferred hypoglycemic effect and an increased pharmacological availability (13.7 ± 4.1%) after oral administration of the EXE-PLGA NPs @YCWPs. It is believed that the PLGA nanoparticles in YCWP system could become an efficient strategy to orally deliver therapeutic peptide drugs.

Gastrointestinal lipolysis and trans-epithelial transport of SMEDDS via oral route

Self-microemulsifying drug delivery systems (SMEDDSs) have recently returned to the limelight of academia and industry due to their enormous potential in oral delivery of biomacromolecules. However, information on gastrointestinal lipolysis and trans-epithelial transport of SMEDDS is rare. Aggregation-caused quenching (ACQ) fluorescent probes are utilized to visualize the in vivo behaviors of SMEDDSs, because the released probes during lipolysis are quenched upon contacting water. Two SMEDDSs composed of medium chain triglyceride and different ratios of Tween-80 and PEG-400 are set as models, meanwhile Neoral® was used as a control. The SMEDDS droplets reside in the digestive tract for as long as 24 h and obey first order kinetic law of lipolysis. The increased chain length of the triglyceride decreases the lipolysis of the SMEDDSs. Ex vivo imaging of main tissues and histological examination confirm the trans-epithelial transportation of the SMEDDS droplets. Approximately 2%-4% of the given SMEDDSs are transported via the lymph route following epithelial uptake, while liver is the main termination. Caco-2 cell lines confirm the cellular uptake and trans-epithelial transport. In conclusion, a fraction of SMEDDSs can survive the lipolysis in the gastrointestinal tract, permeate across the epithelia, translocate via the lymph, and accumulate mainly in the liver.

Engineering a sustained release vaccine with a pathogen-mimicking manner for robust and durable immune responses

Sustained release vaccine carriers can facilitate an increased interaction time between the antigen and immune system to strengthen immune responses, but their promotion on adaptive immune responses, especially cellular immunity, are still unfavorable. Herein, we report a sustained antigen delivery vector, which carries abundant antigens, a nucleic acid adjuvant and pathogen-associated molecular patterns to simulate a natural pathogen to reinforce immune responses. Specifically, murine colorectal cancer cells MC38 lysate and Toll-like receptor 9 agonist CpG are loaded into yeast derived β-glucan particles (GPs). After vaccination, these particles can form a vaccine depot that continuously release the antigen similar to the traditional aluminum hydroxide gel, but recruit more immune cells and induce more cytokine secretion at the injection site. Stronger antibody responses, Th1 and Th17 biased cellular immunity and immune memory are achieved compared with aluminum hydroxide gel. More importantly, treatment with these particles significantly suppress tumor growth in a therapeutic tumor model. This work shed light on the efficacy of combining sustained antigen release with pathogen-mimicking manner in vaccine design.

Peroral targeting of drug micro or nanocarriers to sites beyond the gastrointestinal tract

Targeted delivery of drug micro or nanocarriers has been attained via parenteral routes, especially the intravenous route. Conventionally, oral targeting refers to site-specific delivery and triggered drug release at local sites within the gastrointestinal tract (GIT), or targeting to the enteric epithelia through ligand-receptor or transporter interactions. Beyond that barrier, the concept of peroral targeting has not been clarified. Nevertheless, this is possible as long as drug carriers are able to be absorbed into the systemic circulation intact. Recent findings on in vivo translocation of drug micro or nanocarriers shed light on potential peroral targeting to remote sites beyond the GIT. Sequential processes of penetration across the enteric epithelia, transportation via the lymphatics and ultimate convergence with the systemic circulation are involved in the underlying mechanisms. The microfold cell (M cell) pathway plays a leading role in breaking through the enteric epithelial barrier. Accumulating evidence confirms primary targeting of a series of lipid and polymeric micro or nanocarriers to organs and tissues of the mononuclear phagocyte systems (MPS), such as the liver, spleen, lungs and kidneys. The total amount of lymph-bound particles could reach 8%, as evidenced by quantification of glucan microparticles that specifically bind M cell. Migration or translocation of micro or nanocarrier-bearing macrophages attains secondary targeting of the engulfed micro or nanocarriers to distant sites far beyond the MPS. The current findings foresee a probability of targeting to sites beyond the GIT. However, the content of exposure of micro or nanocarriers at target sites and potential therapeutic or diagnostic promises are yet to be unraveled.

The role of polysaccharides from natural resources to design oral insulin micro- and nanoparticles intended for the treatment of Diabetes mellitus: A review

Oral administration of insulin (INS) would represent a revolution in the treatment of diabetes, considering that this route mimics the physiological dynamics of endogenous INS. Nano- and microencapsulation exploiting the advantageous polysaccharides properties has been considered an important technological strategy to protect INS against harsh conditions of gastrointestinal tract, in the same time that improve the permeability via transcellular and/or paracellular pathways, safety and in some cases even selectivity for targeting delivery of INS. In fact, some polysaccharides also give to the systems functional properties such as pH-responsiveness, mucoadhesiveness under specific physiological conditions and increased intestinal permeability. In general, all polysaccharides can be functionalized with specific molecules becoming more selective to the cells to which INS is delivered. The present review highlights the advances in the past 10 years on micro- and nanoencapsulation of INS exploiting the unique natural properties of polysaccharides, including chitosan, starch, alginate, pectin, and dextran, among others.

Optimization of phytic acid-crosslinked chitosan microspheres for oral insulin delivery using response surface methodology

Although oral administration is favorable mode of insulin delivery, it is the most challenging route, owing to poor oral bioavailability. In this study, a chitosan (CS)-based insulin delivery system was developed by ionic crosslinking with phytic acid (PA). CS-PA microspheres were optimized with different crosslinking conditions of CS and PA using response surface methodology to retain insulin during preparation and gastric digestion. Furthermore, the in vitro release profile, morphological structure, cytotoxicity, and intestinal permeability of the optimized microspheres, and its hypoglycemic effect in diabetic rats were evaluated. Under optimal conditions, the entrapment efficiency was 97.1%, and 67.0% of insulin was retained in the microspheres after 2 h of gastric digestion followed by a sustained-release in intestinal fluid. Insulin was primarily distributed in the microsphere core with a monodisperse diameter of 663.3 μm. The microspheres increased the permeability of insulin across Caco-2/HT-29 monolayers by 1.6 times with negligible cytotoxicity. The microspheres had a relative pharmacological bioavailability of 10.6% and significantly reduced blood glucose levels with a long-lasting hypoglycemic effect after oral administration in diabetic rats. This study demonstrated that an optimized formulation of a simple ionic crosslinking system using CS and PA could facilitate efficient oral delivery of insulin.

A Novel Strategy for Treating Inflammatory Bowel Disease by Targeting Delivery of Methotrexate through Glucan Particles

Therapy of inflammatory bowel disease (IBD) has been a difficult task in the medical field. There is a great clinical need for more effective treatments for IBD. Herein, a targeted oral delivery system of yeast glucan particles (YGPs) carrying a clinically used anti-inflammatory drug methotrexate (MTX) to the inflamed sites in IBD mice for therapy is reported. In the findings, MTX is effectively loaded into YGPs through re-precipitation followed by gelation reaction of alginate to obtain the composite YGPs/MTX, which are internalized into RAW264.7 macrophage cells through dectin-1 and CR3 receptors. Furthermore, YGPs/MTX can suppress the proliferation of macrophage cells efficiently, leading to down-regulation of pro-inflammatory cytokines induced by lipopolysaccharides. Additionally, YGPs accumulate in the inflammation site of colitis mice, enabling YGPs/MTX to target the inflammatory site, significantly improve the efficacy of MTX, and reduce the cytotoxicity of MTX. Therefore, the YGPs-based drug delivery system provides a new strategy for MTX application in the clinical treatment of IBD.

Improving the hypoglycemic effect of insulin via the nasal administration of deep eutectic solvents

This study aimed to develop biocompatible deep eutectic solvents (DESs) as carriers for improving the nasal delivery of insulin. The DES was prepared from malic acid and choline chloride broadly used in foods, drugs, or cosmetics as biocompatible additives. The DES of choline chloride and malic acid (CM-DES) demonstrated lower melting point (-59.1 °C) and higher viscosity (120,000 cP) compared with hydrogels based on sodium carboxyl methyl cellulose (CMC-Na). The conformational structure of insulin does not change in CM-DES as characterized by circular dichroism. The in vitro results showed that CM-DES dissociated gradually but did not disintegrate immediately upon contact with water. CM-DES was able to improve the hypoglycemic effect of insulin significantly at different doses compared with hydrogels or solutions of insulin, which could be ascribed to facilitated penetration of insulin across the nasal epithelia by CM-DES. The hypoglycemic effect of CM-DES loading insulin at a dose of 25 IU/kg was similar to that of subcutaneous insulin at 1 IU/kg. In addition, no evident toxicity to nasal epithelia was observed after nasal administration to rats for seven consecutive days. In conclusion, CM-DES showed promising potential in enhancing the hypoglycemic effect of insulin via the nasal route.

Curcumin encapsulation in yeast glucan particles promotes its anti-inflammatory potential in vitro

Glucan particles (GPs) from Saccharomyces cerevisiae are hollow shells that are composed mainly of β-1,3-d-glucan, which has demonstrated immunomodulatory and anti-inflammatory potential both in vitro and in vivo. Curcumin is a natural hydrophobic phenolic compound, which possesses a significant anti-inflammatory effect and is used as supportive therapy in the treatment of many inflammatory diseases. The aim of this study is to evaluate the possible synergic effect and other benefits of the co-application of GPs and curcumin in the form of pharmaceutical composites. GP/curcumin composites were prepared using controlled evaporation of the organic solvent and their anti-oxidative effect and anti-inflammatory potential were tested on THP1‑XBlue™‑MD2‑CD14 human monocytes cell line. The anti-oxidative effect was measured on pyocyanin-stimulated cells in vitro and the NF-κB/AP-1 signaling pathway on lipopolysaccharide pre-treated monocytes was chosen for anti-inflammatory assays. The secretion of pro-inflammatory cytokines TNF-α and IL-1β was evaluated as well. Results mostly showed a pro-oxidative activity of empty GPs, however, pharmaceutical composites demonstrated an anti-oxidative effect. The activity of NF-κB/AP-1 was substantially decreased by the tested GP/curcumin composites, which also caused the attenuation of cytokines secretion. The obtained results indicate a beneficial effect of the incorporation of curcumin into GPs.

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.

Loss of integrity of doxorubicin liposomes during transcellular transportation evidenced by fluorescence resonance energy transfer effect

The aim of this work was to elucidate the influence of liposome characteristics on the transcellular process by in vitro studies that would enable designing more efficient oral formulations. Various liposomes with different properties were prepared, including 100-500 nm, anionic, cationic and PEGylated liposomes. All liposomes were labeled by fluorescence resonance energy transfer (FRET) probes to evaluate their integrity in cellular uptake and transport. The FRET fluorescent intensity is proportional to the amount of intact liposomes, which was used to calculate the amount of intact liposomes in cellular uptake and transport. The liposomal structures were found to lose their integrity during or after uptake and only about 20% intact liposomes were detected in cells. However, more cationic liposomes were transported integrally across cell monolayer and accounted for 40.49% of total transport by triple culture models of Caco-2/HT29-MTX/Raji B. These results suggest that liposomes could improve cellular uptake and transport of the payloads significantly, but only a small fraction of liposomes are transported integrally across epithelial monolayer. The study is therefore helpful to rationally fabricate more efficient oral liposomes for poorly water-soluble drugs or biomacromolecules.

Reassessment of long circulation via monitoring of integral polymeric nanoparticles justifies a more accurate understanding

Monitoring of payloads results in a biased perception of long circulation of nanoparticles. Instead, herein, the long-circulation effect was re-confirmed by monitoring integral nanoparticles, but circulation was not found to be as long as generally perceived. In contrast, disparate pharmacokinetics were obtained by monitoring a model drug, paclitaxel, highlighting the bias of the conventional protocol.

Entrapping of Nanoparticles in Yeast Cell Wall Microparticles for Macrophage-Targeted Oral Delivery of Cabazitaxel

In this work, a nano-in-micro carrier was constructed by loading polymer-lipid hybrid nanoparticles (NPs) into porous and hollow yeast cell wall microparticles (YPs) for macrophage-targeted oral delivery of cabazitaxel (CTX). The YPs, primarily composed of natural β-1,3-d-glucan, can be recognized by the apical membrane receptor, dectin-1, which has a high expression on macrophages and intestinal M cells. By combining electrostatic force-driven self-deposition with solvent hydration/lyophilization methods, the positively charged NPs loaded with CTX or fluorescence probes were efficiently packaged into YPs, as verified by scanning electron microscope (SEM), atomic force mircoscope (AFM), and confocal laser scanning microscopy (CLSM) images. NP-loaded YPs (NYPs) showed a slower in vitro drug release and higher drug stability compared with NPs in a simulated gastrointestinal environment. Biodistribution experiments confirmed a widespread distribution and extended retention time of NYPs in the intestinal tract after oral administration. Importantly, a large amount of NYPs were primarily accumulated and transported in the intestinal Peyer's patches as visualized in distribution and absorption site studies, implying that NYPs were mainly absorbed through the lymphatic pathway. In vitro cell evaluation further demonstrated that NYPs were rapidly and efficiently taken up by macrophages via receptor dectin-1-mediated endocytosis using a mouse macrophage RAW 264.7 cell line. As expected, in the study of in vivo pharmacokinetics, the oral bioavailability of CTX was improved to 32.1% when loaded in NYPs, which is approximately 5.7 times higher than that of the CTX solution, indicating the NYPs are efficient for oral targeted delivery. Hence, this nano-in-micro carrier is believed to become a hopeful alternative strategy for increasing the oral absorption of small molecule drugs.

Visual validation of the measurement of entrapment efficiency of drug nanocarriers

Entrapment efficiency (EE) is a crucial parameter for the evaluation of nanocarriers. The accurate measurement of EE demands clear separation of nanocarriers from free drugs, which so far has not been clearly validated due to a lack of functional tools to identify nanocarriers. Herein, an environment-responsive water-quenching fluorophore was employed to label and identify model nanocarriers, polycaprolactone nanoparticles (PN), methoxy polyethylene glycol-poly(d,l-lactic acid) polymeric micelles (PM) and solid lipid nanoparticles (SLN). The separation process of three commonly used methods (centrifugation, ultrafiltration and gel permeation chromatography) was visualized by live imaging. The separation efficiency of the centrifugation method is very poor, especially for PM (40 nm), SLN (100 nm) and PN (100 nm); only PN (200 nm) can be efficiently separated but at a consumption of enormous energy. The ultrafiltration method shows the best separation efficiency with only 0.32-0.93% of leakage of the nanocarriers. Gel permeation chromatography exhibits good separation as well but suffers from low recovery, a potential factor that might compromise the accuracy of EE measurement. In conclusion, the ultrafiltration method is the method of choice for efficient separation and accurate measurement of EE.

Biomimetic thiamine- and niacin-decorated liposomes for enhanced oral delivery of insulin

Biomimetic nanocarriers are emerging as efficient vehicles to facilitate dietary absorption of biomacromolecules. In this study, two vitamins, thiamine and niacin, are employed to decorate liposomes loaded with insulin, thus facilitating oral absorption via vitamin ligand-receptor interactions. Both vitamins are conjugated with stearamine, which works to anchor the ligands to the surface of liposomes. Liposomes prepared under optimum conditions have a mean particle size of 125-150 nm and an insulin entrapment efficiency of approximately 30%-36%. Encapsulation into liposomes helps to stabilize insulin due to improved resistance against enzymatic disruption, with 60% and 80% of the insulin left after 4 h when incubated in simulated gastric and intestinal fluids, respectively, whereas non-encapsulated insulin is broken down completely at 0.5 h. Preservation of insulin bioactivity against preparative stresses is validated by intra-peritoneal injection of insulin after release from various liposomes using the surfactant Triton X-100. In a diabetic rat model chemically induced by streptozotocin, both thiamine- and niacin-decorated liposomes showed a comparable and sustained mild hypoglycemic effect. The superiority of decorated liposomes over conventional liposomes highlights the contribution of vitamin ligands. It is concluded that decoration of liposomes with thiamine or niacin facilitates interactions with gastrointestinal vitamin receptors and thereby facilitates oral absorption of insulin-loaded liposomes.

Influence of Particle Geometry on Gastrointestinal Transit and Absorption following Oral Administration

Geometry has been considered as one of the important parameters in nanoparticle design because it affects cellular uptake, transport across the physiological barriers, and in vivo distribution. However, only a few studies have been conducted to elucidate the influence of nanoparticle geometry in their in vivo fate after oral administration. This article discloses the effect of nanoparticle shape on transport and absorption in gastrointestinal (GI) tract. Nanorods and nanospheres were prepared and labeled using fluorescence resonance energy transfer molecules to track the in vivo fate of intact nanoparticles accurately. Results demonstrated that nanorods had significantly longer retention time in GI tract compared with nanospheres. Furthermore, nanorods exhibited stronger ability of penetration into space of villi than nanospheres, which is the main reason of longer retention time. In addition, mesenteric lymph transported 1.75% nanorods within 10 h, which was more than that with nanospheres (0.98%). Fluorescent signals arising from nanoparticles were found in the kidney but not in the liver, lung, spleen, or blood, which could be ascribed to low absorption of intact nanoparticles. In conclusion, nanoparticle geometry influences in vivo fate after oral delivery and nanorods should be further investigated for designing oral delivery systems for therapeutic drugs, vaccines, or diagnostic materials.

Binary and Tertiary Complex Based on Short-Chain Glucan and Proanthocyanidins for Oral Insulin Delivery

The present study was performed to investigate binary and tertiary nanocomposites between short-chain glucan (SCG) and proanthocyanidins (PAC) for the oral delivery of insulin. There was a large decrease in fluorescence intensity of insulin in the presence of SCG or the combination of SCG with PAC. Fourier transform infrared spectroscopy revealed that the binary and tertiary nanocomposites were synthesized due to the hydrogen bonding and hydrophobic interactions. The insulin entrapped in the nanocomposites was in an amorphous state confirmed by X-ray diffraction. The cell culture demonstrated that both the nanocomposites showed no detectable cytotoxicity with relative cell viability all above 85%. The pharmacological bioavailability after oral administration of insulin-SCG-PAC at a dose of 100 IU/kg was found to be 6.98 ± 1.20% in diabetic rats without any sharp fluctuations in 8 h.

In Vivo Fate of Biomimetic Mixed Micelles as Nanocarriers for Bioavailability Enhancement of Lipid-Drug Conjugates

The transformation of lipid-based nanovehicles into mixed micelles (MMs) upon lipolysis plays an indispensable role in enhancement of the oral bioavailability of poorly water-soluble drugs. Therefore, this study employs biomimetic MMs as functional vehicles to enhance the oral bioavailability of the lipid conjugates of a model drug silybin. The main objective is to explore the in vivo fate and underlying mechanisms of facilitated absorption by MMs. Pharmacokinetics in rats indicate bioavailability enhancement by 7-9 folds as compared to a fast-release silybin solid dispersion formulation. Confocal laser scanning microscopy reveals evidence of cellular uptake of integral MMs into the cytoplasm of both Caco-2 and Caco-2/HT29-MTX coculture cells lines. The recovery of a definite amount of prototype silybin but negligible or traces of lipid-silybin conjugates from the cells, as well as the limited trans-monolayer transport, confirms fast disruption of MMs and fast degradation of the conjugates as well. The MMs survive the gastrointestinal environment with relatively high integrity for about 4 h, and are found accumulating in intestinal villi surface layers in higher density but in lower density to the basolateral tissues. By scanning the organs, a small amount of integral MMs are observed to distribute mainly to the livers with peak time around 4-8 h. The total amount of lymphatic absorption monitored by cannulation is negligible. It is concluded that biomimetic MMs might be taken up by enterocytes and be digested there to release the prototype drug, which is further transported to the circulation, and only a limited amount of integral MMs could be absorbed into the circulation.

In vivo fate of lipid-silybin conjugate nanoparticles: Implications on enhanced oral bioavailability

Lipid-drug conjugates (LDCs) of a poorly soluble and poorly permeable drug silybin (SB) and lipids with different chain lengths (6C, 12C, 18C) are synthesized and formulated into solid lipid nanoparticles (SLNs). The in vivo fate of LDCs as well as SLNs is investigated by tracking either SB or LDCs or SLNs. LDCs are prone to be hydrolyzed by lipases either in simulated gastrointestinal media or in Caco-2 cell lines in a lipid chain length-dependent mode. The oral bioavailability of SB is enhanced by 5-7-fold in comparison with a fast-release formulation. No integral LDCs are detected in plasma confirms the readily degradable nature of LDCs. The absorption of LDCs by enteric epithelia and subsequent transportation into circulation might play a leading role in absorption enhancement, whereas the contribution of then M-cell pathway is not as remarkable. A shorter lipid chain favors earlier lipolysis and faster absorption along the intestine-to-circulation path.

Size-Dependent Translocation of Nanoemulsions via Oral Delivery

The in vivo translocation of nanoemulsions (NEs) was tracked by imaging tools with an emphasis on the size effect. To guarantee the accurate identification of NEs in vivo, water-quenching environment-responsive near-infrared fluorescent probes were used to label NEs. Imaging evidence confirmed prominent digestion in the gastrointestinal tract and oral absorption of integral NEs that survive digestion by enteric epithelia in a size-dependent way. In general, reducing particle size leads to slowed in vitro lipolysis and in vivo digestion, a prolonged lifetime in the small intestine, increased enteric epithelial uptake, and enhanced transportation to various organs. Histological examination revealed a pervasive distribution of smaller NEs (80 nm) into enterocytes and basolateral tissues, whereas bigger ones (550, 1000 nm) primarily adhered to villi surfaces. Following epithelial uptake, NEs are transported through the lymphatics with a fraction of approximately 3-6%, suggesting a considerable contribution of the lymphatic pathway to overall absorption. The majority of absorbed NEs were found 1 h post administration in the livers and lungs. A similar size dependency of cellular uptake and transmonolayer transport was confirmed in Caco-2 cell lines as well. In conclusion, the size-dependent translocation of integral NEs was confirmed with an absolute bioavailability of at least 6%, envisioning potential applications in oral delivery of labile entities.

Evidence of nose-to-brain delivery of nanoemulsions: cargoes but not vehicles

The nose-to-brain pathway has been proven to be a shortcut for direct drug delivery to the brain. However, whether and to what extent nanoparticles can be delivered through this passage is still awaiting validation with evidence. In this study, nose-to-brain transportation of nanoparticles is tracked via fluorescence bioimaging strategies using nanoemulsions (NEs) as model carriers. Identification of NEs in biological tissues is based on the on → off signal switching of a new type of environment-responsive embedded dyes, P2 and P4, and two conventional probes, DiR and coumarin-6 (C6), are embedded to represent the cargoes. Evidence for the translocation of NEs was collected either via live imaging or ex vivo histological examination in rats after nasal administration. Results suggest that NEs with a particle size of about 100 nm, either naked or coated with chitosan, have longer retention duration in nostrils and slower mucociliary clearance than larger ones. P2 signals, representing integral NEs, can be found in mucosa and trigeminal nerves for all size groups, whereas only weak P2 signals are detected in the olfactory bulb for chitosan-coated NEs of 100 nm. Confocal microscopy further confirms the translocation of integral 100 nm NEs in nasal mucosa and along the trigeminal nerve in decremental intensity. Weak signals of the P4 probe, also representing integral NEs, can be detected in the olfactory bulb but few in the brain. NEs as large as 900 nm cannot be transported to the olfactory bulb. However, the DiR or C6 signals that represent the cargoes can be found in significant amounts along the nose-to-brain pathway and finally reach the brain. Evidence shows that integral NEs can be delivered to the olfactory bulb, but few to the brain, whereas the cargoes can be released and permeated into the brain in greater amounts.

Bioimaging of nanoparticles: the crucial role of discriminating nanoparticles from free probes

The biological fate of nanocarriers has yet to be fully explored, mainly because of the lack of functional tools like probes to identify integral nanocarriers in the body. Understanding their in vivo fate remains as the bottleneck to the development of nanomedicines. Bioimaging results based on conventional fluorescent or radioactive probes should be judged critically because images merely reflect bulk signals of an admixture of the nanoparticles and free probes. It is crucial to discriminate between nanocarrier-bound and free signals. This review analyzes the state-of-the-art of bioimaging of nanoparticles in vivo and highlights directions for future endeavours.