Mechanisms of transcellular transport of wheat germ agglutinin-functionalized polymeric nanoparticles in Caco-2 cells

Advances in the transport of oral nanoparticles in gastrointestinal tract

Biological barriers in the gastrointestinal tract (GIT) prevent oral absorption of insoluble drugs. Recently, significant progress has been made in the development of various nanoparticles (NPs) designed to enhance the efficacy of oral drugs. However, the mechanism underlying the intracellular transport of NPs remains unclear, and there are still limitations to improving the oral bioavailability of drugs. This article reviews the challenges faced in the absorption of oral NPs, proposes strategies to overcome these barriers, and discusses the future prospects.

Wheat germ agglutinin modified mixed micelles overcome the dual barrier of mucus/enterocytes for effective oral absorption of shikonin and gefitinib

The combination of shikonin (SKN) and gefitinib (GFB) can reverse the drug resistance of lung cancer cells by affecting energy metabolism. However, the poor solubility of SKN and GFB limits their clinical application because of low bioavailability. Wheat germ agglutinin (WGA) can selectively bind to sialic acid and N-acetylglucosamine on the surfaces of microfold cells and enterocytes, and is a targeted biocompatible material. Therefore, we created a co-delivery micelle system called SKN/GFB@WGA-micelles with the intestinal targeting functions to enhance the oral absorption of SKN and GFB by promoting mucus penetration for nanoparticles via oral administration. In this study, Caco-2/HT29-MTX-E12 co-cultured cells were used to simulate a mucus/enterocyte dual-barrier environment, and HCC827/GR cells were used as a model of drug-resistant lung cancer. We aimed to evaluate the oral bioavailability and anti-tumor effect of SKN and GFB using the SKN/GFB@WGA-micelles system. In vitro and in vivo experimental results showed that WGA promoted the mucus penetration ability of micelles, significantly enhanced the uptake efficiency of enterocytes, improved the oral bioavailability of SKN and GFB, and exhibited good anti-tumor effects by reversing drug resistance. The SKN/GFB@WGA-micelles were stable in the gastrointestinal tract and provided a novel safe and effective drug delivery strategy.

Co-assembly of foxtail millet prolamin-lecithin/alginate sodium in citric acid-potassium phosphate buffer for delivery of quercetin

Foxtail millet nanoparticles with smaller mean size at ∼130 nm and narrower polydispersity index at ∼0.05 were prepared in citric acid-potassium phosphate buffer (pH 8.0). Through lecithin (Lec)/sodium alginate (Alg) coating, a hydrophobic FP core, a Lec monolayer, and a hydrophilic Alg shell were formed spontaneously. Dissociation experiment revealed that electrostatic interaction and hydrogen bonding were main driving forces for the formation and maintenance of stable FP-Lec/Alg NPs. In addition, Lec/Alg coated NPs exerted an important role in sustaining the controlled release of the encapsulated quercetin under simulated gastrointestinal tract conditions. Cellular uptake test exhibited that FP-Lec-Alg NPs cold enter epithelial cells in a time-dependent manner, showing the maximum uptake efficiency were 22% and 24%, respectively, after 2 h of incubation. About 220 nm NPs can be recovered by adding 10% (w/v) sucrose. FP-Lec-Alg NPs were found to be promising delivery materials to deliver quercetin and improve its bioavailability.

Recent Advances in the Surface Functionalization of PLGA-Based Nanomedicines

Therapeutics are habitually characterized by short plasma half-lives and little affinity for targeted cells. To overcome these challenges, nanoparticulate systems have entered into the disease arena. Poly(d,l-lactide-co-glycolide) (PLGA) is one of the most relevant biocompatible materials to construct drug nanocarriers. Understanding the physical chemistry of this copolymer and current knowledge of its biological fate will help in engineering efficient PLGA-based nanomedicines. Surface modification of the nanoparticle structure has been proposed as a required functionalization to optimize the performance in biological systems and to localize the PLGA colloid into the site of action. In this review, a background is provided on the properties and biodegradation of the copolymer. Methods to formulate PLGA nanoparticles, as well as their in vitro performance and in vivo fate, are briefly discussed. In addition, a special focus is placed on the analysis of current research in the use of surface modification strategies to engineer PLGA nanoparticles, i.e., PEGylation and the use of PEG alternatives, surfactants and lipids to improve in vitro and in vivo stability and to create hydrophilic shells or stealth protection for the nanoparticle. Finally, an update on the use of ligands to decorate the surface of PLGA nanomedicines is included in the review.

Wheat Germ Agglutinin-Conjugated Disulfide Cross-Linked Alginate Nanoparticles as a Docetaxel Carrier for Colon Cancer Therapy

PURPOSE

In chemotherapy, oral administration of drug is limited due to lack of drug specificity for localized colon cancer cells. The inability of drugs to differentiate cancer cells from normal cells induces side effects. Colonic targeting with polymeric nanoparticulate drug delivery offers high potential strategies for delivering hydrophobic drugs and fewer side effects to the target site. Disulfide cross-linked polymers have recently acquired high significance due to their potential to degrade in reducing colon conditions while resisting the upper gastrointestinal tract's hostile environment. The goal of this project is, therefore, to develop pH-sensitive and redox-responsive fluorescein-labeled wheat germ agglutinin (fWGA)-mounted disulfide cross-linked alginate nanoparticles (fDTP2) directly targeting docetaxel (DTX) in colon cancer cells.

METHODS

fDTP2 was prepared by mounting fWGA on DTX-loaded nanoparticles (DTP2) using the two-step carbodiimide method. Morphology of fDTP2 was examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Dynamic light scattering (DLS) study was carried out to determine the mean diameter, polydispersity index (PDI) and zeta potential of fDTP2. Cellular uptake efficiency was examined using fluorescence microplate reader. Biocompatibility and active internalization of fDTP2 were conducted on HT-29.

RESULTS

fDTP2 was found to exhibit a DTX loading efficiency of 19.3%. SEM and TEM tests revealed spherical nanoparticles. The in vitro DTX release test showed a cumulative release of 54.7%. From the DLS study, fDTP2 reported a 277.7 nm mean diameter with PDI below 0.35 and -1.0 mV zeta potential. HT-29 which was fDTP2-treated demonstrated lower viability than L929 with a half maximal inhibitory concentration (IC50) of 34.7 µg/mL. HT-29 (33.4%) internalized fDTP2 efficiently at 2 h incubation. The study on HT-29 active internalization of nanoparticles through fluorescence and confocal imaging indicated such.

CONCLUSION

In short, fDTP2 demonstrated promise as a colonic drug delivery DTX transporter.

Low-frequency ultrasound combined with microbubbles improves gene transfection in prostate cancer cells in vitro and in vivo

OBJECTIVES

The aim of this study is to explore whether low-frequency ultrasound combined with microbubbles improves pEGFP genes transfection into human prostate cancer cells.

METHODS

Ultrasound with frequency of 80 kHz and duty cycle of 50% was adopted in the study; in in vitro experiments, cell lysis, and membrane damage were evaluated after ultrasound exposure; and the membrane continuity and transfection efficiency were observed by transmission electron microscope and laser scanner, respectively. Human prostate cancer xenograft models were exposed to ultrasound and transfection efficiency and histological examination were analyzed.

RESULTS

Compared with the control group, ultrasound combined with microbubbles significantly improves gene transfection efficiency (P < .05). In in vitro study, ultrasound combined with microbubbles resulted in cell lysis and the interruption of cell membrane continuity, and its average transfection efficiency was 9.9%; the green fluorescence intensity was 15.2% in the ultrasound combined with microbubbles group in vivo; both values were higher than that in the control group (P < .05).

CONCLUSION

Low-frequency ultrasound combined with microbubbles could be used as a method to promote gene transfection in prostate cancer cells.

Mechanistic Approaches of Internalization, Subcellular Trafficking, and Cytotoxicity of Nanoparticles for Targeting the Small Intestine

Targeting the small intestine employing nanotechnology has proved to be a more effective way for site-specific drug delivery. The drug targeting to the small intestine can be achieved via nanoparticles for its optimum bioavailability within the systemic circulation. The small intestine is a remarkable candidate for localized drug delivery. The intestine has its unique properties. It has a less harsh environment than the stomach, provides comparatively more retention time, and possesses a greater surface area than other parts of the gastrointestinal tract. This review focuses on elaborating the intestinal barriers and approaches to overcome these barriers for internalizing nanoparticles and adopting different cellular trafficking pathways. We have discussed various factors that contribute to nanocarriers' cellular uptake, including their surface chemistry, surface morphology, and functionalization of nanoparticles. Furthermore, the fate of nanoparticles after their uptake at cellular and subcellular levels is also briefly explained. Finally, we have delineated the strategies that are adopted to determine the cytotoxicity of nanoparticles.

Tuning the PEG surface density of the PEG-PGA enveloped Octaarginine-peptide Nanocomplexes

One of the main limitations of protein drugs is their restricted capacity to cross biological barriers. We have previously reported nanostructured complexes of insulin and modified octaarginine (C12-r8), enveloped by a polyethyleneglycol-polyglutamic acid (PEG-PGA) protective shell, and showed their capacity to overcome different barriers associated to the oral modality of administration. The objective of this work was to produce the said nanocomplexes with structurally diverse PEG-PGA shells, i.e. with different chain lengths and PEG substitution degrees, and comparatively analyze their PEG surface density and subsequent impact on their interaction with mucus glycoproteins and Caco-2 cells. The new PEG-PGA enveloped C12-r8-insulin nanocomplexes (ENCPs) exhibited a narrow size distribution (average size of 210-239 nm), a neutral surface charge and a 100% insulin association efficiency (final insulin loading of 16.5-29.6% w/w). Proton nuclear magnetic resonance (¹H NMR) analysis indicated the possibility to modulate the PEG density on the ENCPs from 6.7 to 44.5 PEG chains per 100 nm². This increase in the ENCPs PEG surface density resulted in their reduced interaction with mucins in vitro, while their interaction with Caco-2 cells in vitro remained unaltered. Overall, these data indicate the capacity to tune the surface characteristics of the ENCPS in order to maximize the capacity of these nanocarriers to overcome barriers associated to mucosal surfaces.

Subcellular Performance of Nanoparticles in Cancer Therapy

With the advent of nanotechnology, various modes of traditional treatment strategies have been transformed extensively owing to the advantageous morphological, physiochemical, and functional attributes of nano-sized materials, which are of particular interest in diverse biomedical applications, such as diagnostics, sensing, imaging, and drug delivery. Despite their success in delivering therapeutic agents, several traditional nanocarriers often end up with deprived selectivity and undesired therapeutic outcome, which significantly limit their clinical applicability. Further advancements in terms of improved selectivity to exhibit desired therapeutic outcome toward ablating cancer cells have been predominantly made focusing on the precise entry of nanoparticles into tumor cells via targeting ligands, and subsequent delivery of therapeutic cargo in response to specific biological or external stimuli. However, there is enough room intracellularly, where diverse small-sized nanomaterials can accumulate and significantly exert potentially specific mechanisms of antitumor effects toward activation of precise cancer cell death pathways that can be explored. In this review, we aim to summarize the intracellular pathways of nanoparticles, highlighting the principles and state of their destructive effects in the subcellular structures as well as the current limitations of conventional therapeutic approaches. Next, we give an overview of subcellular performances and the fate of internalized nanoparticles under various organelle circumstances, particularly endosome or lysosome, mitochondria, nucleus, endoplasmic reticulum, and Golgi apparatus, by comprehensively emphasizing the unique mechanisms with a series of interesting reports. Moreover, intracellular transformation of the internalized nanoparticles, prominent outcome and potential affluence of these interdependent subcellular components in cancer therapy are emphasized. Finally, we conclude with perspectives with a focus on the contemporary challenges in their clinical applicability.

The challenges of oral drug delivery via nanocarriers

The oral application of pharmaceuticals is unarguably the most convenient method of application. Especially for protein- or peptide-based drugs, however, the effectiveness is significantly reduced due to enzymatic digestion in the stomach as well as a poor bioavailability in the small intestine. For these difficult formulations, the encapsulation into nanocarriers would protect the sensitive drug and thus could considerably improve the efficiency of oral drug delivery. In the last years, many candidate biodegradable nanomaterials for such carrier systems have been published. However, before the cargo can be released, the nanocarrier needs to cross multiple barriers of the human body, including a layer of intestinal mucus and epithelial as well as endothelial cells. For overcoming these cellular barriers, transcytosis is favored over a paracellular transport for most nanomaterials as paracellular transport routes lack selectivity of transported molecules once opened up. The exact mechanisms behind the transcellular translocations are up to now still not completely understood. For the vast majority of nanocarriers, the rate of transcellular transport is not sufficient to realize their application in oral drug delivery. Especially trafficking into the endolysosomal pathway often marks a key problem. In this review, we focus on the molecular mechanisms of overcoming cellular barriers, especially transcytosis, and highlight difficulties of oral drug delivery via nanocarriers.

Role of critical elements in botulinum neurotoxin complex in toxin routing across intestinal and bronchial barriers

The highly potent botulinum neurotoxin serotype A (BoNT/A) inhibits neurotransmitter release at neuromuscular junctions resulting in flaccid muscle paralysis, respiratory arrest and death. In order to reach their neuronal cell targets, BoNT/A must cross epithelial cell barriers lining the intestines and airways. The toxin is produced as a large protein complex comprised of the neurotoxin and non-toxic neurotoxin-associated proteins (NAPs). Although NAPs are known to protect the toxin from harsh environments, their role in the movement of BoNT/A across epithelial barriers has not been fully characterized. In the current study, movement of the toxin across epithelial cells was examined macroscopically using a sensitive near infrared fluorescence transcytosis assay and microscopically using fluorescently labeled toxin and confocal microscopy. The studies show that the BoNT/A complex internalizes more rapidly than the pure toxin. The studies also show that one NAP protein, hemaglutinin 33 (Hn33), enhanced both the binding and movement of a deactivated recombinant botulinum neurotoxin A (DrBoNT) across epithelial cell monolayers and that the toxin associates with Hn33 on the cell surface. Collectively, the data demonstrate that, in addition to their protective role, NAPs and Hn33 play an important role in BoNT/A intoxication.

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.

Noninvasive monitoring of nanoparticle clearance and aggregation in blood circulation by in vivo flow cytometry

Nanoparticles have been widely used in biomedical research as drug carriers or imaging agents for living animals. Blood circulation is crucial for the delivery of nanoparticles, which enter the bloodstream through injection, inhalation, or dermal exposure. However, the clearance kinetics of nanoparticles in blood circulation has been poorly studied, mainly because of the limitations of conventional detection methods, such as insufficient blood sample volumes or low spatial-temporal resolution. In addition, formation of nanoparticle aggregates is a key determinant for biocompatibility and drug delivery efficiency. Aggregation behavior of nanoparticles in blood is studied using dynamic light scattering in serum or serum protein solutions, which is still very different from in vivo condition. In this work, we monitored the dynamics of nanoparticle concentration and formation of nanoparticle aggregates in the bloodstream in live animals using in vivo flow cytometry (IVFC). The results indicated that nanoparticles in smaller size could stay longer in the bloodstream. Polyethylene glycol (PEG)-modification could prolong circulating time and reduce the formation of aggregates in the blood circulation. Our work shows that IVFC can be a powerful tool for pharmacokinetic studies of nanoparticles and other drug carriers, assessing cell-targeting efficiency, as well as potentially measuring cardiac output and hepatic function in vivo.

Targeted Therapeutic Nanoparticles: An Immense Promise to Fight against Cancer

In nanomedicine, targeted therapeutic nanoparticle (NP) is a virtual outcome of nanotechnology taking the advantage of cancer propagation pattern. Tying up all elements such as therapeutic or imaging agent, targeting ligand, and cross-linking agent with the NPs is the key concept to deliver the payload selectively where it intends to reach. The microenvironment of tumor tissues in lymphatic vessels can also help targeted NPs to achieve their anticipated accumulation depending on the formulation objectives. This review accumulates the application of poly(lactic-co-glycolic acid) (PLGA) and polyethylene glycol (PEG) based NP systems, with a specific perspective in cancer. Nowadays, PLGA, PEG, or their combinations are the mostly used polymers to serve the purpose of targeted therapeutic NPs. Their unique physicochemical properties along with their biological activities are also discussed. Depending on the biological effects from parameters associated with existing NPs, several advantages and limitations have been explored in teaming up all the essential facts to give birth to targeted therapeutic NPs. Therefore, the current article will provide a comprehensive review of various approaches to fabricate a targeted system to achieve appropriate physicochemical properties. Based on such findings, researchers can realize the benefits and challenges for the next generation of delivery systems.

Isolation of Rice Bran Lectins and Characterization of Their Unique Behavior in Caco-2 Cells

Rice bran lectins, named as RBA1 and RBA2, were isolated from Oryza sativa in two chromatography steps: affinity chromatography and cation-exchange chromatography. RBA1 was found to be composed of a covalently linked heterodimer of 20- and 12-kDa subunits, and RBA2 was a noncovalently linked dimer of 12-kDa subunits. Both RBA1 and RBA2 bound to desialylated complex glycoproteins such as fetuin, α1-acid glycoprotein, and transferrin, and agalactosylated complex glycoproteins such as agalacto fetuin, agalacto-α1-acid glycoprotein, and agalacto-transferrin, in addition to chitooligosacchrides. RBAs were heat stable up to 80 °C and stable at pH 4–10. RBA1 increased the transport of the fluorescent marker, rhodamine 123, which is known to be transported via the P-glycoprotein-mediated efflux pathway across human intestinal Caco-2 cell monolayers. Furthermore, RBA1 itself was transported to the basolateral side of the monolayers via an endocytotic pathway.

Mechanisms of transport of polymeric and lipidic nanoparticles across the intestinal barrier

Unraveling the mechanisms of nanoparticle transport across the intestinal barrier is essential for designing more efficient nanoparticles for oral administration. The physicochemical parameters of the nanoparticles (e.g., size, surface charge, chemical composition) dictate nanoparticle fate across the intestinal barrier. This review aims to address the most important findings regarding polymeric and lipidic nanoparticle transport across the intestinal barrier, including the evaluation of critical physicochemical parameters of nanoparticles that affect nanocarrier interactions with the intestinal barrier.

Intercellular transfer of P-glycoprotein in human blood-brain barrier endothelial cells is increased by histone deacetylase inhibitors

The blood–brain barrier (BBB) controls the entry of compounds into the brain, thereby regulating brain homeostasis. Efflux transporters such as P-glycoprotein (Pgp) significantly contribute to BBB function. Multiple signaling pathways modulate the expression and activity of Pgp in response to xenobiotics and disease. A non-genetic way of intercellular transfer of Pgp occurs in cancer cells, but whether this also occurs in non-cancer cells such as endothelial cells that form the BBB is not known. A human brain endothelial cell line (hCMEC/D3) was used to study whether cell-to-cell Pgp transfer occurs during co-culturing with Pgp-EGFP expressing hCMEC/D3 cells. The Pgp-EGFP fusion protein was transferred from donor to recipient cells by cell-to-cell contact and Pgp-EGFP enriched vesicles, which were exocytosed by donor cells and endocytosed by adherent recipient cells. Flow cytometry experiments with the Pgp substrate eFLUXX-ID Gold demonstrated that the transferred Pgp is functional in the recipient cells. Exposure of the donor cells with inhibitors of histone deacetylases (HDACs) resulted in an enhanced intercellular Pgp transfer. Non-genetic transfer of a resistance phenotype and its regulation by HDACs is a novel mechanism of altering BBB functionality. This mechanism may have important implications for understanding drug-induced alterations in Pgp expression and activity.

The mechanism of self-assembled mixed micelles in improving curcumin oral absorption: In vitro and in vivo

Curcumin-loaded self-assembled polymeric micelles (Cur-PMs) were designed to increase oral bioavailability of curcumin and investigate the oral absorption mechanism in vitro and in vivo. The Cur-PMs were spherical nano-size particles 17.82±0.33nm in size, with a drug loading of 3.52±0.18%, and encapsulation efficiency as high as 93.08±2.23%. The intestinal absorption of Cur-PMs in the duodenum, jejunum, and ileum was 3.09-, 6.48-, and 1.78-fold greater than that of curcumin solution (Cur-Sol) at 0.5h. The cellular uptake of Cur-PMs in Caco-2 cells was significantly enhanced in comparison with Cur-Sol by caveolae-mediated and clathrin-mediated endocytosis. Moreover, the apparent permeability coefficient (Papp) of Cur-PMs was 3.50-fold higher than that of Cur-Sol in Caco-2 transport studies. The transport mechanism of Cur-PMs into the system circulation was not paracellular transport through opening the tight junctions, but was by energy-dependent, macropinocytic transcytosis and lymphatic transport pathways. Furthermore, the AUC(0-t) value of Cur-PMs was improved 2.87-fold compared with that of Cur-Sol after oral administration in rats. Therefore, self-assembled polymeric micelles could be a promising vehicle to efficiently improve the oral absorption of curcumin.

High-content analysis for drug delivery and nanoparticle applications

High-content analysis (HCA) provides quantitative multiparametric cellular fluorescence data. From its origins in discovery toxicology, it is now addressing fundamental questions in drug delivery. Nanoparticles (NPs), polymers, and intestinal permeation enhancers are being harnessed in drug delivery systems to modulate plasma membrane properties and the intracellular environment. Identifying comparative mechanistic cytotoxicity on sublethal events is crucial to expedite the development of such systems. NP uptake and intracellular routing pathways are also being dissected using chemical and genetic perturbations, with the potential to assess the intracellular fate of targeted and untargeted particles in vitro. As we discuss here, HCA is set to make a major impact in preclinical delivery research by elucidating the intracellular pathways of NPs and the in vitro mechanistic-based toxicology of formulation constituents.

Fluorescence microscopy colocalization of lipid-nucleic acid nanoparticles with wildtype and mutant Rab5-GFP: A platform for investigating early endosomal events

Endosomal entrapment is known to be a major bottleneck to successful cytoplasmic delivery of nucleic acids (NAs) using cationic liposome-NA nanoparticles (NPs). Quantitative measurements of distributions of NPs within early endosomes (EEs) have proven difficult due to the sub-resolution size and short lifetime of wildtype EEs. In this study we used Rab5-GFP, a member of the large family of GTPases which cycles between the plasma membrane and early endosomes, to fluorescently label early endosomes. Using fluorescence microscopy and quantitative image analysis of cells expressing Rab5-GFP, we found that at early time points (t<1h), only a fraction (≈35%) of RGD-tagged NPs (which target cell surface integrins) colocalize with wildtype EEs, independent of the NP's membrane charge density. In comparison, a GTP-hydrolysis deficient mutant, Rab5-Q79L, which extends the size and lifetime of EEs yielding giant early endosomes (GEEs), enabled us to resolve and localize individual NPs found within the GEE lumen. Remarkably, nearly all intracellular NPs are found to be trapped within GEEs implying little or no escape at early time points. The observed small degree of colocalization of NPs and wildtype Rab5 is consistent with recycling of Rab5-GDP to the plasma membrane and not indicative of NP escape from EEs. Taken together, our results show that endosomal escape of PEGylated nanoparticles occurs downstream of EEs i.e., from late endosomes/lysosomes. Our studies also suggest that Rab5-Q79L could be used in a robust imaging assay which allows for direct visualization of NP interactions with the luminal membrane of early endosomes.

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

Ligand grafted nanoparticles have been shown to enhance drug transport across epithelium barrier and are expected to improve drug delivery. However, grafting of these ligands to the surface of pure nanodrug, i.e., nanocrystals (NCs), is a critical challenge due to the shedding of ligands along with the stabilizer upon high dilution or dissolving of the drug. Herein, a non-sheddable nanocage-like stabilizer was designed by covalent cross-linking of poly(acrylic acid)-b-poly(methyl acrylate) on drug nanocrystal surface, and a ligand, wheat germ agglutinin (WGA), was successfully anchored to the surface of itraconazole (ITZ) NCs by covalent conjugation to the nanocage (WGA-cage-NCs). The cellular study showed that large amount of WGA-cage-NCs were adhered to Caco-2 cell membrane, and invaded into cells, resulting in a higher drug uptake than that of ordinary NCs (ONCs). After oral administration to rats, WGA-cage-NC were largely accumulated on the apical side of epithelium cells, facilitating drug diffusing across epithelium barrier. Interestingly, WGA-cage-NCs were capable of invading rat intestinal villi and reaching to lamina propria by transcytosis across goblet cells, which behaved like a foodborne pathogen, Listeria monocytogenes. The WGA-cage-NCs showed an improved oral bioavailability, which was 17.5- and 2.41-folds higher than that of coarse crystals and ONCs, respectively. To our best knowledge, this may represent the first report that a functional ligand was successfully anchored to the surface of pure nanodrug by using a cage-like stabilizer, showing unique biological functions in gastrointestinal tract and having an important significance in oral drug delivery.

Antitumor effect of iRGD-modified liposomes containing conjugated linoleic acid-paclitaxel (CLA-PTX) on B16-F10 melanoma

In the present study, we prepared a novel delivery system of iRGD (CRGDK/RGPD/EC)-modified sterically stabilized liposomes (SSLs) containing conjugated linoleic acid–paclitaxel (CLA-PTX). The anti-tumor effect of iRGD-SSL-CLA-PTX was investigated on B16-F10 melanoma in vitro and in vivo. The in vitro targeting effect of iRGD-modified SSLs was investigated in a real-time confocal microscopic analysis experiment. An endocytosis-inhibition assay was used to evaluate the endocytosis pathways of the iRGD-modified SSLs. In addition, the in vitro cellular uptake and in vitro cytotoxicity of iRGD-SSL-CLA-PTX were evaluated in B16-F10 melanoma cells. In vivo biodistribution and in vivo antitumor effects of iRGD-SSL-CLA-PTX were investigated in B16-F10 tumor-bearing mice. The induction of apoptosis by iRGD-SSL-CLA-PTX was evaluated in tumor-tissue sections. Real-time confocal microscopic analysis results indicated that the iRGD-modified SSLs internalized into B16-F10 cells faster than SSLs. The identified endocytosis pathway of iRGD-modified SSLs indicated that energy- and lipid raft-mediated endocytosis played a key role in the liposomes’ cellular uptake. The results of the cellular uptake experiment indicated that the increased cellular uptake of CLA-PTX in the iRGD-SSL-CLA-PTX-treated group was 1.9-, 2.4-, or 2.1-fold compared with that in the CLA-PTX group after a 2-, 4-, or 6-hour incubation, respectively. In the biodistribution test, the CLA-PTX level in tumor tissues from iRGD-SSL-CLA-PTX-treated mice at 1 hour (1.84±0.17 μg/g) and 4 hours (1.17±0.28 μg/g) was 2.3- and 2.0-fold higher than that of CLA-PTX solution at 1 hour (0.79±0.06 μg/g) and 4 hours (0.58±0.04 μg/g). The value of the area under the curve for the first 24 hours in the tumors of iRGD-SSL-CLA-PTX-treated mice was significantly higher than that in the SSL-CLA-PTX and CLA-PTX solution-treated groups (P<0.01). The in vivo antitumor results indicated that iRGD-SSL-CLA-PTX significantly inhibited the growth of B16-F10 tumors compared with the SSL-CLA-PTX or CLA-PTX solution-treatment groups (P<0.01). The results of tumor-cell apoptosis showed that tumors from the iRGD-SSL-CLA-PTX-treated group exhibited more advanced cell apoptosis compared with the control, CLA-PTX solution-, and SSL-CLA-PTX-treated groups. In conclusion, the antitumor effect of iRGD-SSL-CLA-PTX was confirmed on B16-F10 melanoma in vitro and in vivo.

Lipoprotein-based nanoparticles rescue the memory loss of mice with Alzheimer's disease by accelerating the clearance of amyloid-beta

Amyloid-beta (Aβ) accumulation in the brain is believed to play a central role in Alzheimer's disease (AD) pathogenesis, and the common late-onset form of AD is characterized by an overall impairment in Aβ clearance. Therefore, development of nanomedicine that can facilitate Aβ clearance represents a promising strategy for AD intervention. However, previous work of this kind was concentrated at the molecular level, and the disease-modifying effectiveness of such nanomedicine has not been investigated in clinically relevant biological systems. Here, we hypothesized that a biologically inspired nanostructure, apolipoprotein E3-reconstituted high density lipoprotein (ApoE3-rHDL), which presents high binding affinity to Aβ, might serve as a novel nanomedicine for disease modification in AD by accelerating Aβ clearance. Surface plasmon resonance, transmission electron microscopy, and co-immunoprecipitation analysis showed that ApoE3-rHDL demonstrated high binding affinity to both Aβ monomer and oligomer. It also accelerated the microglial, astroglial, and liver cell degradation of Aβ by facilitating the lysosomal transport. One hour after intravenous administration, about 0.4% ID/g of ApoE3-rHDL gained access to the brain. Four-week daily treatment with ApoE3-rHDL decreased Aβ deposition, attenuated microgliosis, ameliorated neurologic changes, and rescued memory deficits in an AD animal model. The findings here provided the direct evidence of a biomimetic nanostructure crossing the blood-brain barrier, capturing Aβ and facilitating its degradation by glial cells, indicating that ApoE3-rHDL might serve as a novel nanomedicine for disease modification in AD by accelerating Aβ clearance, which also justified the concept that nanostructures with Aβ-binding affinity might provide a novel nanoplatform for AD therapy.

Co-administration of dual-targeting nanoparticles with penetration enhancement peptide for antiglioblastoma therapy

Chemotherapy is an indispensable auxiliary treatment for glioma but highly limited by the existence of both blood-brain barrier (BBB) and blood-brain tumor barrier (BBTB). The dysfunctional brain tumor blood vessels and high interstitial pressure in glioma also greatly hindered the accumulation and deep penetration of chemotherapeutics into the glioma. Lactoferrin (Lf), with its receptor overexpressed on both the brain endothelial cells and glioma cells, was here functionalized to the surface of poly(ethylene glycol)-poly(lactic acid) nanoparticles to mediate BBB/BBTB and glioma cell dual targeting. tLyP-1, a tumor-homing peptide, which contains a C-end Rule sequence that can mediate tissue penetration through the neuropilin-1-dependent internalization pathway, was coadministrated with Lf-functionalized nanoparticles (Lf-NP) to enhance its accumulation and deep penetration into the glioma parenchyma. Enhanced cellular association in both BCEC and C6 cells, increased cytotoxicity of the loaded paclitaxel, and deep penetration in the 3D glioma spheroids was achieved by Lf-NP. Following coadministration with tLyP-1, the functionalized nanoparticles obtained improved tumor targeting, glioma vascular extravasation, and antiglioma efficacy. The findings here suggested that the strategy by coadministrating BBB/BBTB and glioma cells dual-targeting nanocarriers with a tumor penetration enhancement peptide represent a promising platform for antiglioma drug delivery.

Concepts and practices used to develop functional PLGA-based nanoparticulate systems

The functionality of bare polylactide-co-glycolide (PLGA) nanoparticles is limited to drug depot or drug solubilization in their hard cores. They have inherent weaknesses as a drug-delivery system. For instance, when administered intravenously, the nanoparticles undergo rapid clearance from systemic circulation before reaching the site of action. Furthermore, plain PLGA nanoparticles cannot distinguish between different cell types. Recent research shows that surface functionalization of nanoparticles and development of new nanoparticulate dosage forms help overcome these delivery challenges and improve in vivo performance. Immense research efforts have propelled the development of diverse functional PLGA-based nanoparticulate delivery systems. Representative examples include PEGylated micelles/nanoparticles (PEG, polyethylene glycol), polyplexes, polymersomes, core-shell-type lipid-PLGA hybrids, cell-PLGA hybrids, receptor-specific ligand-PLGA conjugates, and theranostics. Each PLGA-based nanoparticulate dosage form has specific features that distinguish it from other nanoparticulate systems. This review focuses on fundamental concepts and practices that are used in the development of various functional nanoparticulate dosage forms. We describe how the attributes of these functional nanoparticulate forms might contribute to achievement of desired therapeutic effects that are not attainable using conventional therapies. Functional PLGA-based nanoparticulate systems are expected to deliver chemotherapeutic, diagnostic, and imaging agents in a highly selective and effective manner.