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

Quantitative Investigation of Intestinal Drug Absorption Enhancement by Drug-Rich Nanodroplets Generated via Liquid-Liquid Phase Separation

Drug-rich droplets formed through liquid-liquid phase separation (LLPS) have the potential to enhance the oral absorption of drugs. This can be attributed to the diffusion of these droplets into the unstirred water layer (UWL) of the gastrointestinal tract and their reservoir effects on maintaining drug supersaturation. However, a quantitative understanding of the effect of drug-rich droplets on intestinal drug absorption is still lacking. In this study, the enhancement of intestinal drug absorption through the formation of drug-rich droplets was quantitatively evaluated on a mechanistic basis. To obtain fenofibrate (FFB)-rich droplets, an amorphous solid dispersion (ASD) of FFB/hypromellose (HPMC) was dispersed in an aqueous medium. Physicochemical characterization confirmed the presence of nanosized FFB-rich droplets in the supercooled liquid state within the FFB/HPMC ASD dispersion. An in situ single-pass intestinal perfusion (SPIP) assay in rats demonstrated that increased quantities of FFB-rich nanodroplets enhanced the intestinal absorption of FFB. The effective diffusion of FFB-rich nanodroplets through UWL would partially contribute to the improved FFB absorption. Additionally, confocal laser scanning microscopy (CLSM) of cross sections of the rat intestine after the administration of fluorescently labeled FFB-rich nanodroplets showed that these nanodroplets were directly taken up by small intestinal epithelial cells. Therefore, the direct uptake of drug-rich nanodroplets by the small intestine is a potential mechanism for improving FFB absorption in the intestine. To quantitatively evaluate the impact of FFB-rich droplets on the FFB absorption enhancement, we determined the apparent permeabilities of the FFB-rich nanodroplets and dissolved FFB based on the SPIP results. The apparent permeability of the FFB-rich nanodroplets was 110-130 times lower than that of dissolved FFB. However, when the FFB-rich nanodroplet concentration was several hundred times higher than that of dissolved FFB, the FFB-rich nanodroplets contributed significantly to FFB absorption improvement. The present study highlights that drug-rich nanodroplets play a direct role in enhancing drug absorption in the gastrointestinal tract, indicating their potential for further improvement of oral absorption from ASD formulations.

Phytochemicals and Cancer Treatment: Cell-Derived and Biomimetic Vesicles as Promising Carriers

The majority of anticancer agents currently used derive from natural sources: plants, frequently the ones employed in traditional medicines, are an abundant source of mono- and diterpenes, polyphenols, and alkaloids that exert antitumor activity through diverse mechanisms. Unfortunately, many of these molecules are affected by poor pharmacokinetics and limited specificity, shortcomings that may be overcome by incorporating them into nanovehicles. Cell-derived nanovesicles have recently risen to prominence, due to their biocompatibility, low immunogenicity and, above all, targeting properties. However, due to difficult scalability, the industrial production of biologically-derived vesicles and consequent application in clinics is difficult. As an efficient alternative, bioinspired vesicles deriving from the hybridization of cell-derived and artificial membranes have been conceived, revealing high flexibility and appropriate drug delivery ability. In this review, the most recent advances in the application of these vesicles to the targeted delivery of anticancer actives obtained from plants are presented, with specific focus on vehicle manufacture and characterization, and effectiveness evaluation performed through in vitro and in vivo assays. The emerging overall outlook appears promising in terms of efficient drug loading and selective targeting of tumor cells, suggesting further engrossing developments in the future.

Investigating the trans-membrane transport of HAIYPRH peptide-decorated nano-drugs

Transferrin (Tf) has been effectively used to promote the cellular uptake of HAIYPRH (T7) peptide-conjugated nano-drugs. In this study, the enhancing effect of Tf on T7-decorated nano-drug transport was investigated using force tracing and nano-indentation techniques at a single-particle/cell level. Furthermore, the results were confirmed by ensemble fluorescence imaging.

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

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

Enhanced Oral Absorption and Liver Distribution of Polymeric Nanoparticles through Traveling the Enterohepatic Circulation Pathways of Bile Acid

The intestinal epithelium is known to be a main hindrance to oral delivery of nanoparticles. Even though surface ligand modification can enhance cellular uptake of nanoparticles, the "easy entry and hard across" was frequently observed for many active targeting nanoparticles. Here, we fabricated polymeric nanoparticles relayed by bile acid transporters with monomethoxy poly(ethylene glycol)-poly(D,l-lactide) and deoxycholic acid-conjugated poly(2-ethyl-2-oxazoline)-poly(D,l-lactide) based on structural characteristics of intestine epithelium and the absorption characteristics of endogenous substances. As anticipated, deoxycholic acid-modified polymeric nanoparticles featuring good stability in simulated gastrointestinal fluid could notably promote the internalization of their payload by Caco-2 cells through mediation of apical sodium-dependent bile acid transporter (ASBT) and transmembrane transport of the nanoparticles across Caco-2 cell monolayers via relay-guide of ASBT, ileal bile acid-binding protein, and the heteromeric organic solute transporter (OSTα-OSTβ) along with multidrug resistance-associated protein 3 (MRP3) evidenced by competitive inhibition and fluorescence immunoassay, which was further visually confirmed by the stronger fluorescence from C6-labeled nanoparticles inside enterocytes and the basal side of the intestinal epithelium of mice. The transcellular transport of deoxycholic acid-modified nanoparticles in an intact form was mediated by caveolin/lipid rafts and clathrin with intracellular trafficking trace of endosome-lysosome-ER-Golgi apparatus and bile acid transport route. Furthermore, the increased uptake by HepG2 cells compared with unmodified nanoparticles evidenced the target ability of deoxycholic acid-modified nanoparticles to the liver, which was further supported by ex vivo imaging of excised major organs of mice. Thus, this study provided a feasible and potential strategy to further enhance transepithelial transport efficiency and liver-targeted ability of nanoparticles by means of the specific enterohepatic circulation pathways of bile acid.

Nanocrystals for controlled delivery: State of the art and approved drug products

INTRODUCTION

Controlled/extended-release formulations offer numerous benefits over conventional especially reduced side effects, improved therapeutic outcomes and high patient compliance. Controlled release nanocrystal is extremely versatile technology with several advantages such as very high drug loading, ease of manufacturing, avoidance of dose dumping, reproducible drug release. Usually, nanonization of drug is performed to improve dissolution rate, intrinsic solubility and thereby bioavailability. Most of the times, this is done for immediate release dosage forms where objective is quick onset of action. However, nanocrystals can also provide a sustained, reproducible plasma concentration profile for weeks to months based on tissue microenvironment, surface coating administration route.

AREAS COVERED

This review briefly describes the methods for producing nanocrystals, summarizes preclinical research and commercial products demonstrating tremendous potential of controlled release nanocrystals.

EXPERT OPINION

Lipophilic drugs are attractive candidates for the development of nanocrystal based controlled release formulations. However, constraint should be practiced while generalizing the technology for the controlled release purpose. Not all drugs fit in the requirement from the perspectives of physicochemical properties or pharmacokinetic requirements. Additionally, technologies should be explored which can convert the nanocrystal into its final dosage form for administration yet preserves the benefits of small particle size and controlled release.

Paclitaxel Drug Delivery Systems: Focus on Nanocrystals' Surface Modifications

Paclitaxel (PTX) is a chemotherapeutic agent that belongs to the taxane family and which was approved to treat various kinds of cancers including breast cancer, ovarian cancer, advanced non-small-cell lung cancer, and acquired immunodeficiency syndrome (AIDS)-related Kaposi’s sarcoma. Several delivery systems for PTX have been developed to enhance its solubility and pharmacological properties involving liposomes, nanoparticles, microparticles, micelles, cosolvent methods, and the complexation with cyclodextrins and other materials that are summarized in this article. Specifically, this review discusses deeply the developed paclitaxel nanocrystal formulations. As PTX is a hydrophobic drug with inferior water solubility properties, which are improved a lot by nanocrystal formulation. Based on that, many studies employed nano-crystallization techniques not only to improve the oral delivery of PTX, but IV, intraperitoneal (IP), and local and intertumoral delivery systems were also developed. Additionally, superior and interesting properties of PTX NCs were achieved by performing additional modifications to the NCs, such as stabilization with surfactants and coating with polymers. This review summarizes these delivery systems by shedding light on their route of administration, the methods used in the preparation and modifications, the in vitro or in vivo models used, and the advantages obtained based on the developed formulations.