Roles of effective stabilizers in improving oral bioavailability of naringenin nanocrystals: Maintenance of supersaturation generated upon dissolution by inhibition of drug dimerization

Abstract

Nanocrystals (NCs), a colloidal dispersion system formulated with stabilizers, have attracted widespread interest due to their ability to effectively improve the oral bioavailability of poorly water-soluble drugs. The stabilizer plays a key role because it can affect the physical stability and even the oral bioavailability of NCs. However, how stabilizers affect the bioavailability of NCs remains unknown. In this study, F68, F127, HPMC, and PVP were each used as a stabilizer to formulate naringenin NCs. The NCs formulated with PVP exhibited excellent release behaviors, cellular uptake, permeability, oral bioavailability, and anti-inflammatory effects. The underlying mechanism is that PVP effectively inhibits the formation of naringenin dimer, which in turn improves the physical stability of the supersaturated solution generated when NC is dissolved. This finding provides insights into the effects of stabilizers on the in vivo performances of NCs and supplies valuable knowledge for the development of poorly water-soluble drugs.

Keywords: Bioavailability; Dimer; Nanocrystals; Stabilizers; Supersaturation maintenance.

Graphical abstract

Fig. 1

The chemical structures of (A) NAR, (B) F68 and F127, (C) HPMC, and (D) PVP.

Fig. 2

In vitro characterizations of NAR NCs. Representative transmission electron microscopy images of (A) NC_F68, (B) NC_F127, (C) NC_HPMC, and (D) NC_PVP. The scale bar denotes 500 nm. (E) Differential scanning calorimetry thermograms and (F) powder X-ray diffraction diffractograms of NAR, PM_F68, PM_F127, PM_HPMC, PM_PVP, NC_F68, NC_F127, NC_HPMC, and NC_PVP. The PM_F68, PM_F127, PM_HPMC, and PM_PVP represent the physical mixture of NAR with F68, F127, HPMC, and PVP, respectively.

Fig. 3

(A) Dissolution profiles of NC_F68, NC_F127, NC_HPMC, and NC_PVP in fasted state simulated intestinal fluid. (B) Cumulative transport of NC_F68, NC_F127, NC_HPMC, and NC_PVP across Caco-2 cell monolayers. (C) The concentrations of TNF-α, IL-6, and NO in the supernatant after treatment with different NAR NCs. (D) Fluorescence images of intracellular ROS. Bar: 100 µm. Data are shown as mean ± SD (n = 3). *P < 0.05, **P < 0.01, and ***P < 0.001.

Fig. 4

Plasma drug concentrations of NAR after oral administration of the NCs at a single dose of 50 mg/kg to rats (data are mean ± SD, n = 5).

Fig. 5

The therapeutic effects of NAR NCs in the CIA rat model. (A) Schematic diagram of the establishment and treatment process of the CIA rat model. (B) Hind paw thickness and (C) arthritis scores of rats until d 45 were recorded. Data are shown as mean ± SD. *P < 0.05, ** P < 0.01, ***P < 0.001, and ****P < 0.0001. (D) Photographs of rat hind paw following treatment with PBS, NC_F68, NC_F127, NC_HPMC, or NC_PVP. Healthy, untreated animals served as the control.

Fig. 6

The maintenance of supersaturated solutions. (A) Ultraviolet absorption curve of free NAR after NCs were dissolved in water. (B) The crystallization rate of NAR after NCs dissolved in water. (C) Extinction absorption curves of NAR in different stabilizer solutions. (D) The area under the curve was calculated based on the data of extinction intensity at 500 nm. Data are shown as mean ± SD. ***P < 0.001 and **** P < 0.0001.

Fig. 7

Molecular docking of NAR with different stabilizers: (A) F68, (B) F127, (C) HPMC, and (D) PVP. The square and elliptic virtual frame represent the intramolecular and intermolecular hydrogen bond, respectively.