Development of a polymeric nanoparticulate drug delivery system: In vitro characterization of nanoparticles based on sugar-containing conjugates

https://doi.org/10.1016/S0378-5173(02)00336-8Get rights and content

Abstract

This paper reports the synthesis of polymeric nanoparticles from a sugar-containing conjugate for liver-specific drug delivery. The conjugate was composed of lactobionic acid, diamine-terminated poly(ethylene glycol) and cholic acid (abbreviated as LEC). The conjugate was characterized by 1H NMR and FT-IR spectroscopy measurements. In aqueous media, the conjugate can self-assemble to form core-shell type nanoparticles, and the formation of a core-shell structure was observed by fluorescence spectroscopy. The critical association concentration (CAC) of the LEC conjugate nanoparticles was determined from fluorescence excitation spectra to be 0.05 g/l. The LEC nanoparticles were mostly spherical with sizes ranging from 10 to 30 nm. Clonazepam (CNZ) was used as a model hydrophobic drug, and was incorporated into the hydrophobic core of the nanoparticles. CNZ was released more slowly at a higher drug loading due to drug crystallization.

Introduction

Controlled drug delivery technology represents one of the frontier areas of science, which involves a multidisciplinary scientific approach. These delivery systems offer numerous advantages compared to conventional dosage forms. These include improved efficacy, reduced toxicity, and improved patient compliance and convenience. Such systems often use macromolecules as drug carriers. This field of pharmaceutical technology has grown and has diversified rapidly in recent years.

Among the different dosage forms reported, both nano- and microparticles have gained increasing importance, due to a tendency to accumulate in the inflamed areas of the body (Illum et al., 1989). Nano- and microparticles occupy a unique position in drug delivery technology due to their attractive properties. In particular, nanoparticles have several advantages in pharmaceutical applications. They are easily purified and sterilized. In addition, they offer drug targeting possibilities and a sustained release action (Allemann et al., 1993). Nanoparticles based on a core-shell structure or polymeric micelle present advantages in terms of lengthy circulation in the body, drug solubility, drug stability, and a high level of drug encapsulation (Yokoyama et al., 1991, Gref et al., 1994, Kwon et al., 1995).

For liver disease therapy, there has been growing interest in the area of liver-cell specific drug delivery systems in recent years. This may be due to a failure of other pharmacological approaches to the liver disease site as a result of the non-specific delivery mechanism towards the other organs and several side effects. A great deal of effort has been made to achieve an appropriate liver targeting of chemotherapeutic agents with liposomes (Kim and Han, 1995), microspheres (Kim et al., 1993), and drug-carrier molecule conjugates (Seymour et al., 1991). Among the liver-associated surface receptors, the asialoglycoprotein receptor (ASGP-R: galactose receptor) is well known to be present only on hepatocytes (Ashwell and Harford, 1982). It is also retained on several human hepatoma cell lines (Fallon and Schwartz, 1988). If a ligand binds to a galactose receptor, the ligand–receptor complex is rapidly internalized and the receptor recycles back to the surface (Ciechanover et al., 1983). Accordingly, the receptor shows a high binding capacity and efficient cellular uptake of galactosylated ligands. Therefore, designing a drug delivery system for galactose receptor-mediated endocytosis would be useful for targeting the hepatocyte/liver and hepatoma cells (Nishikawa et al., 1993, Goto et al., 1994).

In this study, core-shell type polymeric nanoparticles composed of cholic acid (CA) and diamine-terminated poly(ethylene glycol) (ATPEG) with a galactose moiety from lactobionic acid (abbreviated as LEC) was synthesized for a liver-specific drug delivery system. CA is a naturally occurring substance and acts as a drug incorporation site with hydrophobic characteristics. ATPEG is a modified PEG which has well defined biocompatibility, is non-toxic, and has non-immunogenic properties. It is known to prevent interactions with cells and proteins due to its hydrophilic nature (Wang et al., 1997). Because of the amphiphilicity of the LEC conjugate, core-shell type nanoparticles with a sugar moiety were prepared by a diafiltration method, and the physico-chemical characteristics were evaluated in vitro.

Section snippets

Materials

ATPEG with an average molecular weight of 2000 was supplied by the Texaco Chem. Co. (Ballaire, TX). CA and N-hydroxysuccinimide (NHS) were purchased from the Sigma Chem. Co. (St. Louis, MO). Lactobionic acid (LA) and N,N′-dicyclohexyl carbodiimide (DCC) were obtained from the Aldrich Chem. Co. (Milwaukee, USA). The dialysis membranes with a molecular weight cutoff (MWCO) of 2000 g/mol were purchased from Spectra/Por™ Membranes. Dimethyl sulfoxide (DMSO) and other chemicals were of reagent grade

Results and discussion

The synthesized LEC conjugate structure is represented schematically in Fig. 1. The FT-IR spectra provided evidence of LE and LEC conjugate synthesis. In the LE spectrum, the amide stretch and amide bend vibration was observed at 3335 and 1627 cm−1, respectively. The LEC conjugate spectrum contained CH stretch absorption bands at 2927 and 2851 cm−1 due to CA, and an amide bend at 1576 cm−1. The LEC conjugate was also characterized by 1H NMR spectroscopy as shown in the previous report (Kim et

Acknowledgements

This work was supported by Korea Research Foundation Grant (KRF-2001-015-FP0127).

References (20)

There are more references available in the full text version of this article.

Cited by (40)

  • Absolute quantification of poly(DL-lactide-co-glycolide) in microspheres using quantitative <sup>1</sup>H NMR spectroscopy

    2017, Journal of Pharmaceutical and Biomedical Analysis
    Citation Excerpt :

    Notably, glycolic acid and lactic acid are by-products of various metabolic pathways in the body [5]; thus, minimal systemic toxicity is associated with PLGA. PLGA has been widely utilized in medical applications, such as long-acting release products (LARs) [6]. One notable PLGA-based LAR is the leuprorelin microsphere (i.e., Lupron Depot [7]), used for the treatment of advanced prostate and breast cancers.

  • Nanomedicine of anastrozole for breast cancer: Physicochemical evaluation, in vitro cytotoxicity on BT-549 and MCF-7 cell lines and preclinical study on rat model

    2015, Life Sciences
    Citation Excerpt :

    All the wave numbers are shifted to lower side indicating marginal decrease in intensity and also probability of presence of residual intact drug molecules in polymeric structure. These results are also in agreement with the previous studies of Kim et al., and Nimesh et al., where the decrease in the crystallinity of formulations may be due to the polymer network did not have enough time to be organized prior to the formation of nanoparticles during the solvent diffusion into the outer aqueous phase [31,32]. Thus the results of FTIR spectroscopy support the formation of dispersed phase of drug molecules in the polymeric structures which is the characteristics of freshly prepared freeze dried nanoparticles.

  • Glycopolymer micelles with reducible ionic cores for hepatocytes-targeting delivery of DOX

    2013, International Journal of Pharmaceutics
    Citation Excerpt :

    ASGP-R of hepatocytes could recognize and internalize galactose- and N-acetylgalactosamine-terminated glycoproteins via clathrin-coated pits (Stockert, 1995). Therefore many nanocarriers with galactose were synthesized and successfully applied in hepatic cellular-specific drug targeting (Kim and Kim, 2002; Mi et al., 2007). Motivated by the above, we first described the synthesis of block copolymers containing galactose as the ligand targeting HepG2 cells.

  • Antisolvent crystallization of carbamazepine from organic solutions

    2012, Chemical Engineering Research and Design
    Citation Excerpt :

    The development of a drug delivery system is a rapidly expanding subsection of the pharmaceutical market and the current methods frequently require the technologies for particle size reduction. To achieve these goals, researchers have strived for the improvement of the physical characteristics and formulation of drugs, which include the studies on nanotechnology in regards to pharmaceutical application (Kim and Kim, 2002; Pasquali et al., 2008; Lindfors et al., 2008). Carbamazepine (5H-dibenzazepine-5-carboxamide) is a well known drug used for the treatment of epilepsy and trigeminal neuralgia.

View all citing articles on Scopus
View full text