Elsevier

Brain Research Bulletin

Volume 81, Issue 6, 5 April 2010, Pages 600-604
Brain Research Bulletin

Research report
Lactoferrin-modified nanoparticles could mediate efficient gene delivery to the brain in vivo

https://doi.org/10.1016/j.brainresbull.2009.12.008Get rights and content

Abstract

Lactoferrin (Lf)-modified nanoparticles (NPs) have been demonstrated to mediate efficient expression of exogenous genes in the brain via intravenous administration. The brain-targeting properties of Lf-modified NPs were investigated in this study. In vivo imaging results showed that the accumulation of Lf-modified NPs was higher in the brain but lower in the other organs than that of unmodified counterparts. The results of analytical transmission electron microscopy showed that some Lf-modified NPs crossed the blood–brain barrier (BBB) and reached the neural tissues, while some remained within the BBB. Similar results were observed in the distribution of exogenous gene products. All the results demonstrated the successful delivery of Lf-modified NPs into the brain. Lf-modified NPs could be exploited as potential brain-targeting delivery systems for exogenous genes, especially for those encoding secretive proteins.

Introduction

The blood–brain barrier (BBB), due to the presence of tight junctions and lack of fenestrae, is usually the rate-limiting factor for the penetration of proteins, peptides or genes into the central nervous system (CNS) [2]. Fortunately, the BBB possesses specific receptor-mediated transport mechanisms that potentially can be exploited as a means to target drugs to the brain [19], [16]. Till date, receptors discovered on the BBB mainly include transferrin (Tf) receptors, insulin receptors, epidermal growth factor receptors, insulin-like growth factor receptors, and so on [10], [11], [23]. Ligand-mediated brain-targeting drug delivery is one of the focuses at present. The natural ligand, Tf, and the synthetic monoclonal antibody to Tf receptors, for example, have been extensively used as brain-targeting ligands for constructing drug delivery systems to the brain [10], [23], [15], [1]. Some other ligands such as Angiopep-2 to low-density lipoprotein receptor-related protein-1 (LRP1) and RVG29 to GABA (B) receptor have also been exploited for conjugating brain delivery systems [18], [13], [22], [14].

Recently, lactoferrin (Lf) has been exploited as a novel brain-targeting ligand in our lab. Lf is a single-chain iron-binding glycoprotein that belongs to the Tf family. One of the advantages of Lf to be used as a brain-targeting ligand is the low plasma concentration of endogenous Lf, approximately 5 nM [21]. The plasma concentration of Lf is much lower than the Kd of Lf receptors in the BBB [9], efficiently avoiding the competitive inhibition of endogenous Lf to Lf-conjugated exogenous drug delivery systems. Furthermore, the transport of Lf across the BBB monolayer model was reported to be unidirectional, from the apical to the basolateral side [4]. This unidirectional transport might result in higher accumulation of Lf-conjugated drug delivery systems in the neuron, compared to Tf-conjugated counterparts. These advantages were partly reflected in a recent study, the results of which showed that exogenous gene expression of Lf-modified NPs in brains was about 2.3-fold of that of Tf-modified NPs [8]. Similar results were obtained in the biodistribution study of Lf-modified vectors and unmodified counterparts [8]. Hu et al. also reported that an approximate 3-fold of coumarin-6 was found in mice brains carried by Lf-modified NPs compared to that carried by unmodified counterparts [6].

In this study, the brain-targeting properties of Lf-modified NPs were characterized in vivo. The brain accumulation of different NPs was evaluated in macro-level using an in vivo imaging system and in microscopic level via an analytical transmission electron microscope. The expression of exogenous genes in the brain was also studied by staining Von Willebrand in the BBB.

Section snippets

Materials

Polyamidoamine (PAMAM) dendrimer [generation = 5, 21.43%, w/w solution in methanol, containing 128 surface primary amino groups (MW 28,826)], was purchased from Dentritech (Midland, MI, U.S.A.). α-Malemidyl-ω-N-hydroxysuccinimidyl polyethyleneglycol (NHS-PEG-MAL, MW 3400) was obtained from Nektar Therapeutics (Huntsville, AL, U.S.A.). Ethidium monoazide bromide (EMA) was purchased from Molecular Probes (Eugene, OR, U.S.A.). Copper chlorophyll was supplied by Qingdao Green Source Bioengineering

In vivo imaging of mice administrated with different NPs

Nude mice were administered with EMA-labeled Lf-modified NPs, and unmodified NPs as control. In vivo fluorescent images were taken at 4 h after injection. As shown in Fig. 1, EMA-labeled DNA was obviously accumulated in the brain of the mouse treated with Lf-modified NPs (Fig. 1B and F), the fluorescence of which was much stronger than that of unmodified NPs (Fig. 1A and E). Furthermore, the fluorescence relatively concentrated in the central region of the brain, which might be mainly dependent

Discussion

The brain-targeting delivery of Lf-modified NPs was verified in this study. The results fully demonstrated the brain-targeting potential of Lf-modified NPs via several separate means.

Several lines of evidence demonstrated the presence of specific Lf receptors in the brain [21], [3], [20]. Talukder et al. carried out a binding assay for Lf receptors with 125I-Lf and revealed a Kd of 0.11 μM of epithelial membranes of the choroid plexus in young calves [21]. Our previous studies also provided

Acknowledgments

This work was supported by the grants from National Basic Research Program (2007CB935802) of China (973 Program), and National Natural Science Foundation of China (30901861 and 30973652).

References (24)

  • M. Demeule et al.

    Involvement of the low-density lipoprotein receptor-related protein in the transcytosis of the brain delivery vector angiopep-2

    J. Neurochem.

    (2008)
  • B.A. Faucheux et al.

    Expression of lactoferrin receptors is increased in the mesencephalon of patients with Parkinson disease

    Proc. Natl. Acad. Sci. U.S.A.

    (1995)
  • Cited by (0)

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