Polymeric Nanocarriers With Mucus-Diffusive and Mucus-Adhesive Properties to Control Pharmacokinetic Behavior of Orally Dosed Cyclosporine A

Intestinal distribution of anionic, cationic, and neutral polymer-stabilized nanocarriers measured with a lanthanide (europium) tracer assay

Nanocarriers, more commonly called nanoparticles (NPs), have found increasing use as delivery vehicles which increase the oral bioavailability of poorly water-soluble and peptide therapeutics. Therapeutic bioavailability is commonly assessed by measuring plasma concentrations that reflect the absorption kinetics. This bioavailability is a convolution of the gastrointestinal distribution of the NP vehicle, the release rate of the encapsulated therapeutic cargo, and the absorption-metabolism-distribution kinetics of the released therapeutic. The spatiotemporal distribution of the NP vehicle in the gastrointestinal tract is not well studied and is a buried parameter in PK studies used to measure the effectiveness of an NP formulation. This work is a study of the intestinal distribution and fate of orally dosed NPs in male CD-1 mice over 24 h. NPs have identical hydrophobic cores - composed of poly(styrene) homopolymer, a naphthalocyanine dye, and oleate-coated europium oxide colloids - with one of four different surface stabilizers: neutral poly(styrene)-block-poly(ethylene glycol) (PS-b-PEG), moderately negative hydroxypropyl methylcellulose acetate succinate (HPMCAS), highly negative poly(styrene)-block-poly(acrylic acid) (PS-b-PAA), and highly cationic adsorbed chitosan HCl on PS-b-PAA stabilized NPs. NP hydrodynamic diameters are all below 200 nm, with some variation attributable to the molecular properties of the stabilizing polymer. The encapsulated hydrophobic europium oxide colloids do not release soluble europium ions, enabling the use of highly sensitive inductively coupled plasma mass spectrometry (ICP-MS) to detect NP concentrations in digested biological tissues. Highly anionically-charged PAA and cationically-charged chitosan stabilized NPs showed statistically significant increased retention compared to the neutral PEG-stabilized NPs at p < 0.05 significance and (1-β) > 0.95 power. HPMCAS-stabilized NPs showed statistically insignificant greater retention than PEG-stabilized NPs, and all NP formulations showed clearance from the intestines within 24 h. Different surface charges preferentially reside in different segments of the intestines, where cationic chitosan-stabilized NPs showed increased retention in the small intestines (ileum) and anionic PAA-stabilized NPs in the large intestines (caecum and colon). Modifying the surface charge of a NP can be used to modulate mucoadhesion, total retention, and intestinal segment specific retention, which enables the rational design of delivery vehicles that maximize residence times in appropriate locations.

Pharmacokinetic control of orally dosed cyclosporine A with mucosal drug delivery system

This study aimed to control the oral absorption of cyclosporine A (CsA) with the use of a mucosal drug delivery system (mDDS). Mucopenetrating nanocarriers (MP/NCs) and mucoadhesive nanocarriers (MA/NCs) were prepared by flash nanoprecipitation employing polystyrene-block-poly(ethylene glycol) and polystyrene-block-poly(N,N-dimethyl aminoethyl methacrylate), respectively. Their particle distribution in the rat gastrointestinal tract were visualized by fluorescent imaging. Plasma concentrations were monitored after oral administration of CsA-loaded MP/NCs (MP/CsA) and MA/NCs (MA/CsA) to rats. MP/NCs and MA/NCs had a particle size below 200 nm and ζ-potentials of 4 and 40 mV, respectively. The results from in vitro experiments demonstrated mucopenetration of MP/NCs and mucoadhesion of MA/NCs. Confocal laser scanning microscopic images showed diffusion of MP/NCs in the gastrointestinal mucus towards epithelial cells and localization of MA/NCs on the surface of the gastrointestinal mucus layer. In a pH 6.8 solution, rapid and sustained release of CsA were observed for MP/CsA and MA/CsA, respectively. After oral dosing (10 mg-CsA/kg) to rats, amorphous CsA powder exhibited a time to maximum plasma concentration (Tmax) of 3.4 h, maximum plasma concentration (Cmax) of 0.12 μg/mL, and bioavailability of 0.7%. Compared with amorphous CsA powder, MP/CsA shortened Tmax by 1.1 to 2.3 h and increased the bioavailability by 43-fold to 30.1%, while MA/CsA prolonged Tmax by 3.4 to 6.8 h with Cmax and bioavailability of 0.65 μg/mL and 11.7%, respectively. These pharmacokinetic behaviors would be explained by their diffusion and release properties modulated by polymeric surface modification. The mDDS approach is a promising strategy for the pharmacokinetic control of orally administered CsA.

Recent Advancements in the Development of Nanocarriers for Mucosal Drug Delivery Systems to Control Oral Absorption

Oral administration of active pharmaceutical ingredients is desirable because it is easy, safe, painless, and can be performed by patients, resulting in good medication adherence. The mucus layer in the gastrointestinal (GI) tract generally acts as a barrier to protect the epithelial membrane from foreign substances; however, in the absorption process after oral administration, it can also disturb effective drug absorption by trapping it in the biological sieve structured by mucin, a major component of mucus, and eliminating it by mucus turnover. Recently, functional nanocarriers (NCs) have attracted much attention due to their immense potential and effectiveness in the field of oral drug delivery. Among them, NCs with mucopenetrating and mucoadhesive properties are promising dosage options for controlling drug absorption from the GI tracts. Mucopenetrating and mucoadhesive NCs can rapidly deliver encapsulated drugs to the absorption site and/or prolong the residence time of NCs close to the absorption membrane, providing better medications than conventional approaches. The surface characteristics of NCs are important factors that determine their functionality, owing to the formation of various kinds of interactions between the particle surface and mucosal components. Thus, a deeper understanding of surface modifications on the biopharmaceutical characteristics of NCs is necessary to develop the appropriate mucosal drug delivery systems (mDDS) for the treatment of target diseases. This review summarizes the basic information and functions of the mucosal layer, highlights the recent progress in designing functional NCs for mDDS, and discusses their performance in the GI tract.

Promising strategies for improving oral bioavailability of poor water-soluble drugs

INTRODUCTION

Oral administration of poorly water-soluble drugs (PWSDs) is generally related to low bioavailability, leading to high drug doses, multiple side effects, and low patient compliance. Thus, different strategies have been developed to increase drug solubility and dissolution in the gastrointestinal tract, opening new venues for these drugs.

AREAS COVERED

This review outlines the current challenges in PWSD formulation development and the strategies to overcome the oral barriers and increase their solubility and bioavailability. Conventional strategies include altering crystalline and molecular structures and modifying oral solid dosage forms. In contrast, novel strategies comprise micro- and nanostructured systems. Recent representative studies involving how these strategies have improved the oral bioavailability of PWSDs were also reviewed and reported.

EXPERT OPINION

New approaches to enhance PWSD bioavailability have sought to improve water solubility and dissolution rates, drug protection by overcoming biological barriers, and increased absorption. Still, only a handful of studies have focused on quantifying the increase in bioavailability. Improving the oral bioavailability of PWSDs remains an exciting unexplored field of research and has become an important issue for successfully developing pharmaceutical products.

Control and Prediction of Drug Absorption at Mucosal Tissues

The mucosal drug delivery system (mDDS) is one of the promising approaches to control the pharmacokinetic behavior of drugs. In this approach, surface properties of drug nanoparticles are key determinants to provide particles with mucoadhesive and mucopenetrating properties for prolonged retention at mucosal tissue and rapid mucosal absorption, respectively. In this paper, we would like to discuss the preparation of mDDS formulations by flash nanoprecipitation using a four-inlet multi-inlet vortex mixer, in vitro and ex vivo evaluation of mucopenetrating and mucoadhesive properties of polymeric nanoparticles as well as the application of mDDS to the pharmacokinetic control of cyclosporine A after oral administration to rats. We also share our current research on in silico modeling and prediction of the pharmacokinetic behavior of drugs after intratracheal administration to rats.

Mucus interaction to improve gastrointestinal retention and pharmacokinetics of orally administered nano-drug delivery systems

Oral delivery of therapeutics is the preferred route of administration due to ease of administration which is associated with greater patient medication adherence. One major barrier to oral delivery and intestinal absorption is rapid clearance of the drug and the drug delivery system from the gastrointestinal (GI) tract. To address this issue, researchers have investigated using GI mucus to help maximize the pharmacokinetics of the therapeutic; while mucus can act as a barrier to effective oral delivery, it can also be used as an anchoring mechanism to improve intestinal residence. Nano-drug delivery systems that use materials which can interact with the mucus layers in the GI tract can enable longer residence time, improving the efficacy of oral drug delivery. This review examines the properties and function of mucus in the GI tract, as well as diseases that alter mucus. Three broad classes of mucus-interacting systems are discussed: mucoadhesive, mucus-penetrating, and mucolytic drug delivery systems. For each class of system, the basis for mucus interaction is presented, and examples of materials that inform the development of these systems are discussed and reviewed. Finally, a list of FDA-approved mucoadhesive, mucus-penetrating, and mucolytic drug delivery systems is reviewed. In summary, this review highlights the progress made in developing mucus-interacting systems, both at a research-scale and commercial-scale level, and describes the theoretical basis for each type of system.

Clofazimine-Loaded Mucoadhesive Nanoparticles Prepared by Flash Nanoprecipitation for Strategic Intestinal Delivery

PURPOSE

This study was undertaken to develop novel mucoadhesive formulations of clofazimine (CFZ), a drug candidate for the treatment of cryptosporidiosis, with the aim of strategic delivery to the small intestine, the main site of the disease parasites.

METHODS

CFZ-loaded nanoparticles (nCFZ) coated with non-biodegradable anionic polymer (nCFZ/A) and biodegradable anionic protein complex (nCFZ/dA) were prepared by Flash NanoPrecipitation (FNP) and evaluated for their physicochemical and biopharmaceutical properties.

RESULTS

The mean diameters of nCFZ/A and nCFZ/dA were ca. 90 and 240 nm, respectively, and they showed narrow size distributions and negative ζ-potentials. Both formulations showed higher solubility of CFZ in aqueous solution than crystalline CFZ. Despite their improved dispersion behaviors, both formulations exhibited significantly lower diffusiveness than crystalline CFZ in a diffusion test using artificial mucus (AM). Quartz crystal microbalance analysis showed that both formulations clearly interacted with mucin, which appeared to be responsible for their reduced diffusiveness in AM. These results suggest the potent mucoadhesion of nCFZ/A and nCFZ/dA. After the oral administration of CFZ samples (10 mg-CFZ/kg) to rats, nCFZ/dA and nCFZ/A exhibited a prolongation in T_max by 2 and >9 h, respectively, compared with crystalline CFZ. At 24 h after oral doses of nCFZ/A and nCFZ/dA with mucoadhesion, there were marked increases in the intestinal CFZ concentration (4-7 fold) compared with Lamprene^®, a commercial CFZ product, indicating enhanced CFZ exposure in the small intestine.

CONCLUSION

The use of FNP may produce mucoadhesive CFZ formulations with improved intestinal exposure, possibly offering enhanced anti-cryptosporidium therapy.

Carboxymethyl chitosan microspheres loaded hyaluronic acid/gelatin hydrogels for controlled drug delivery and the treatment of inflammatory bowel disease

A major drawback of oral treatment of inflammatory bowel disease (IBD) is the non-specific distribution of drugs during long-term treatment. Despite its effectiveness as an anti-inflammatory drug, curcumin (CUR) is limited by its low bioavailability in IBD treatment. Herein, a pH-sensitive composite hyaluronic acid/gelatin (HA/GE) hydrogel drug delivery system containing carboxymethyl chitosan (CC) microspheres loaded with CUR was fabricated for IBD treatment. The composition and structure of the composite system were optimized and the physicochemical properties were characterized using infrared spectroscopy, X-ray diffraction, swelling, and release behavior studies. In vitro, the formulation exhibited good sustained release property and the drug release rate was 65% for 50 h. In vivo pharmacokinetic experiments indicated that high level of CUR was maintained in the colon tissue for more than 24 h; it also played an anti-inflammatory role by evaluating the histopathological changes through hematoxylin and eosin (H&E), myeloperoxidase (MPO), and immunofluorescent staining. Additionally, the formulation substantially inhibited the level of the main pro-inflammatory cytokines of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) secreted by macrophages, compared to the control group. The pharmacodynamic experiment showed that the formulation group of CUR@gels had the best therapeutic effect on colitis in mice. The composite gel delivery system has potential for the effective delivery of CUR in the treatment of colitis. This study also provides a reference for the design and preparation of a new oral drug delivery system with controlled release behavior.

[Design and Biopharmaceutical Evaluations of Peptide-loaded Inhalable Formulation to Control Pharmacokinetic Behavior]

Recently, biologics including peptides, proteins, antibodies, and nucleic acids have attracted interest as drug candidates for new modalities, since these compounds can act on target molecules that are not be affected by conventional drugs with a small molecular weight to promote greater selectivity, potency, and safety. Generally, to administer biologics, parenteral routes like intravenous and intramuscular injections have been mainly selected due to their poor oral absorbability and stability in the gastrointestinal tract, which can adversely affect patient compliance. Depending on the target diseases, inhalable formulations can be used to achieve both topical effects in the respiratory tracts and systemic actions due to the characteristics of the pulmonary site, including a large surface area, abundant capillary network, thin membrane with adequate permeability for macromolecules, reduced enzymatic degradation, and a lack of first-pass metabolism. In this study, to achieve desirable delivery of peptide drugs with an inhalable formulation to target sites in the respiratory tract and/or absorption sites in the lung, peptide-loaded inhalable formulations were designed by the application of flash nanoprecipitation, one of the precipitation methods to prepare functional nanoparticles, and the fine droplet drying process, a powderization technique using printing technology, to control the pharmacokinetic behavior. From the findings of the study, the strategic applications of these techniques could contribute to provide peptide-loaded inhalable formulations to enhance their biopharmaceutical potentials.