Nanoparticle-Mediated Dual Targeting: An Approach for Enhanced Baicalin Delivery to the Liver

Abstract

In this study, water-soluble chitosan lactate (CL) was reacted with lactobionic acid (LA), a disaccharide with remarkable affinity to hepatic asialoglycoprotein (ASGP) receptors, to form dual liver-targeting LA-modified-CL polymer for site-specific drug delivery to the liver. The synthesized polymer was used to encapsulate baicalin (BA), a promising bioactive flavonoid with pH-dependent solubility, into ultrahigh drug-loaded nanoparticles (NPs) via the ionic gelation method. The successful chemical conjugation of LA with CL was tested and the formulated drug-loaded LA-modified-CL-NPs were assessed in terms of particle size (PS), encapsulation efficiency (EE) and zeta potential (ZP) using full factorial design. The in vivo biodistribution and pharmacokinetics of the designed NPs were assessed using ^99mTc-radiolabeled BA following oral administration to mice and results were compared to ^99mTc-BA-loaded-LA-free-NPs and ^99mTc-BA solution as controls. Results showed that the chemical modification of CL with LA was successfully achieved and the method of preparation of the optimized NPs was very efficient in encapsulating BA into nearly spherical particles with an extremely high EE exceeding 90%. The optimized BA-loaded-LA-modified-CL-NPs showed an average PS of 490 nm, EE of 93.7% and ZP of 48.1 mV. Oral administration of ^99mTc-BA-loaded-LA-modified-CL-NPs showed a remarkable increase in BA delivery to the liver over ^99mTc-BA-loaded-LA-free-CL-NPs and ^99mTc-BA oral solution. The mean area under the curve (AUC_0-24) estimates from liver data were determined to be 11-fold and 26-fold higher from ^99mTc-BA-loaded-LA-modified-CL-NPs relative to ^99mTc-BA-loaded-LA-free-CL-NPs and ^99mTc-BA solution respectively. In conclusion, the outcome of this study highlights the great potential of using LA-modified-CL-NPs for the ultrahigh encapsulation of therapeutic molecules with pH-dependent/poor water-solubility and for targeting the liver.

Keywords: baicalin; chitosan lactate; in vivo biodistribution study; ionic gelation method; lactobionic acid; liver targeting; nanoparticles; radiolabeling.

Figure 1

Response plots for the main effects of the method of addition of lactobionic acid (LA)-ethyldimethylcarbodiimide (EDC) to chitosan lactate (CL) solution and the concentration of LA used on (A) entrapment efficiency (EE%); (B) particle size (PS) and (C) Zeta potential (ZP).

Figure 2

The proposed interaction mechanism between LA (I), EDC (II) and CL (IV) during the formation of LA-modified-CL (V).

Figure 3

ATR spectra of (a) LA; (b) CL; (c) BA-loaded-LA-modified-CL-NPs; (d) BA-loaded-LA-free-CL-NPs and (e) BA. The closed stars represent the amine characteristic bands of CL, the open stars represent the absence of the amine characteristic bands of CL and the dots represent the aromatic characteristic bands attributed to the drug.

Figure 4

In vitro release profiles of BA from its solution in 0.25% TPP, BA-loaded-LA-free-CL-NPs and BA-loaded-LA-modified-CL-NPs in phosphate buffer (pH 6.8) at 37 °C in comparison to the in vitro release of BA from its dispersion in distilled water. Data points are mean ± SD (n = 3).

Figure 5

TEM micrographs of (A) BA-loaded-LA-free-CL-NPs; (B) BA-loaded-LA-modified-CL-NPs and (C) BA-loaded-LA-modified-CL-NPs after sonication.

Figure 6

TEM micrograph of BA-loaded-LA-free-CL-NPs after 15-day storage at room temperature showing particles aggregation.

Figure 7

Effect of different labelling conditions on the percentage radiochemical yield (% RCY) of ^99mTc-BA complex. (a) BA amount, (b) SnCl₂ amount, (c) reaction pH and (d) reaction time.

Figure 8

Mean (±SD) BA concentration in liver following oral administration of radiolabeled ^99mTc-BA to mice.

Figure 9

Mean (±SD) BA concentration in the blood following oral administration of radiolabeled ^99mTc-BA to mice.