Chemical characterization (LC-MS-ESI), cytotoxic activity and intracellular localization of PAMAM G4 in leukemia cells

Generation 4 of polyamidoamine dendrimer (G4-PAMAM) has several biological effects due to its tridimensional globular structure, repetitive branched amides, tertiary amines, and amino-terminal subunit groups liked to a common core. G4-PAMAM is cytotoxic due to its positive charges. However, its cytotoxicity could increase in cancer cells due to the excessive intracellular negative charges in these cells. Furthermore, this work reports G4-PAMAM chemical structural characterization using UHPLC-QTOF-MS/MS (LC-MS) by electrospray ionization to measure its population according to its positive charges. Additionally, the antiproliferative effects and intracellular localization were explored in the HMC-1 and K-562 cell lines by confocal microscopy. The LC-MS results show that G4-PAMAM generated multivalent mass spectrum values, and its protonated terminal amino groups produced numerous positive charges, which allowed us to determine its exact mass despite having a high molecular weight. Additionally, G4-PAMAM showed antiproliferative activity in the HMC-1 tumor cell line after 24 h (IC50 = 16.97 µM), 48 h (IC50 = 7.02 µM) and 72 h (IC50 = 5.98 µM) and in the K-562 cell line after 24 h (IC50 = 15.14 µM), 48 h (IC50 = 14.18 µM) and 72 h (IC50 = 9.91 µM). Finally, our results showed that the G4-PAMAM dendrimers were located in the cytoplasm and nucleus in both tumor cell lines studied.

KR‑12‑a6 promotes the osteogenic differentiation of human bone marrow mesenchymal stem cells via BMP/SMAD signaling

Considering the increased resistance to antibiotics in the clinic and the ideal antibacterial properties of KR‑12, the effects of KR‑12‑a6, an important analogue of KR‑12, on the osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) were investigated. Osteogenic differentiation‑associated experiments were conducted in hBMSCs, and KR‑12‑a6 was used as an additional stimulating factor during osteogenic induction. Quantitative analysis of alkaline phosphatase (ALP) and alizarin red staining, and reverse transcription‑quantitative PCR analysis of the expression of osteogenesis‑associated genes were performed to determine the effects of KR‑12‑a6 on the osteogenic differentiation of hBMSCs. LDN‑212854 was selected to selectively suppress BMP/SMAD signaling. Western blotting was performed to investigate the underlying mechanisms. The intensity of ALP and alizarin red staining gradually increased with increasing KR‑12‑a6 concentrations. KR‑12‑a6 induced the strongest staining at 40 µg/ml, whereas 60 µg/ml and 80 µg/ml concentrations did not further increase the intensity of staining. The mRNA expression levels of RUNX2 and ALP increased in a dose‑dependent manner as early as 3 days post‑KR‑12‑a6 treatment. The mRNA expression of COL1A1, BSP and BMP2 exhibited significant upregulation from day 7 post‑KR‑12‑a6 treatment. In contrast, the mRNA levels of OSX, OCN and OPN were enhanced dramatically at day 14 following KR‑12‑a6 stimulation. Additionally, KR‑12‑a6 significantly promoted the phosphorylation of Smad1/5. Furthermore, LDN‑212854 suppressed the activation of Smad1/5 and inhibited the upregulation of several osteogenic differentiation‑associated genes in KR‑12‑a6‑treated hBMSCs. KR‑12‑a6 promoted the osteogenic differentiation of hBMSCs via BMP/SMAD signaling.

68Ga tagged dendrimers for molecular tumor imaging in animals

Dear Editor, Angiogenesis is an essential physiological process that involves formation of new blood vessels from the pre-existing ones and is one of the fundamental processes required for normal growth and development. The ability to non-invasively evaluate angiogenesis might provide new insights into cancer biology pathway. This approach might lead to opportunities to more appropriately select patients likely to respond to anti-angiogenic drugs. Polyamidoamine dendrimers are a member of a versatile, new class of dendritic polymers and are the most well characterized and widely used polymers. In the present study we have utilized them for imaging of a crucial process of angiogenesis in a cancer model of mice. Amongst, several PET radionuclides, there has been a renewed interest in ⁶⁸Ga for many reasons. Gallium-68 is well suited for use as a radiolabel for PET because of its comparatively shorter half-life of 68min. The emission of two divergent photons per decay allows the construction of three-dimensional images. Furthermore, the advances in generator technology for ⁶⁸Ga production and its favorable chemistry for radiocomplexation have paved the way for emerging applications of ⁶⁸Ga radiopharmaceuticals. A recent study reported the blood pharmacokinetics of different generations of PAMAM dendrimers (generations 3-6) derivatized with large chelating ligands to facilitate complexation of gadolinium ions for imaging applications. It was observed that the resulted PAMAM gadolinium complexes cleared from the blood circulation in a biphasic manner (fast component-10min; slow component-1h). The rapid clearance of the dendrimers from blood observed in our study was in accordance with previous observations. The biodistribution studies of ⁶⁸Ga-DOTA-G4 PAMAM showed the major uptake at an early time interval of 15min in the kidneys. This confirmed that kidneys are the major excretory organs for DOTA conjugated G4 PAMAM dendrimers. The radioactivity in kidneys, as compared with other organs was higher initially and declined with time. A study in the recent past also reported a high uptake of indium-111 (¹¹¹In)-DOTA analog-PAMAM dendrimer in rats' kidneys, immediately after administration of radioactivity. A considerable amount of radioactivity was also recovered from lungs which were higher in case of ⁶⁸Ga-DOTA-G4 PAMAM conjugate. Lung is an important component of the reticulo-endothelial system (RES) and thus is involved in the clearance of macromolecules. Additionally, due to its rich vasculature, lungs are likely targets for the location of intravenously injected dendrimer nanoparticles. The animal biodistribution data in tumor bearing mice demonstrated that the tumor uptake (at 1h) of ⁶⁸Ga-DOTA-G4 PAMAM dendrimer was 0.33%. It has been reported that using higher generation PAMAM dendrimers, magnetic resonance imaging (MRI) agents affect the biodistribution patterns in animal tumor models. Animal PET imaging data showed that maximum tumor to background ratio was obtained at 1h post injection of ⁶⁸Ga DOTA-G4 PAMAM dendrimer suggesting that the designed nanoprobes could efficiently target tumor tissues and be retained there due to their enhanced permeability and retention (EPR) effect. Dendrimers can achieve passive EPR mediated targeting to a tumor by controlling their size and physicochemical properties. Further, an earlier study reported that branched PAMAM dendrimer showed significantly higher accumulation in ovarian tumor bearing mice than the conventional linear N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer of comparable molecular weight. The use of radiolabeled dendrimers due to their topology, functionality and dimensions has been described as a promising approach for the molecular visualization of tumor angiogenesis. So, the successful radiolabeling of ⁶⁸Ga-DOTA-G4 PAMAM dendrimers is encouraging as it showed good localization of both the radiolabeled by ⁶⁸Ga and ¹¹¹In products in the tumor.

Fate and stability of polyamide-associated bacterial assemblages after their passage through the digestive tract of the blue mussel Mytilus edulis

We examined whether bacterial assemblages inhabiting the synthetic polymer polyamide are selectively modified during their passage through the gut of Mytilus edulis in comparison to the biopolymer chitin with focus on potential pathogens. Specifically, we asked whether bacterial biofilms remained stable over a prolonged period of time and whether polyamide could thus serve as a vector for potential pathogenic bacteria. Bacterial diversity and identity were analysed by 16S rRNA gene fingerprints and sequencing of abundant bands. The experiments revealed that egested particles were rapidly colonised by bacteria from the environment, but the taxonomic composition of the biofilms on polyamide and chitin did not differ. No potential pathogens could be detected exclusively on polyamide. However, after 7days of incubation of the biofilms in seawater, the species richness of the polyamide assemblage was lower than that of the chitin assemblage, with yet unknown impacts on the functioning of the biofilm community.

Cellular imaging using biocompatible dendrimer-functionalized graphene oxide-based fluorescent probe anchored with magnetic nanoparticles

We describe a novel multicomponent graphene nanostructured system that is biocompatible, and has strong NIR optical absorbance and superparamagnetic properties. The fabrication of the multicomponent nanostructure system involves the covalent attachment of 3 components; Fe(3)O(4)(Fe) nanoparticles, PAMAM-G4-NH(2) (G4) dendrimer and Cy5 (Cy) on a graphene oxide (GO) surface to synthesize a biologically relevant multifunctional system. The resultant GO-G4-Fe-Cy nanosystem exhibits high dispersion in an aqueous medium, and is magnetically responsive and fluorescent. In vitro experiments provide a clear indication of successful uptake of the GO-G4-Fe-Cy nanosystem by MCF-7 breast cancer cells, and it is seen to behave as a bright and stable fluorescent marker. The study also reveals varied cellular distribution kinetics profile for the GO nanostructured system compared to free Cy. Furthermore, the newly developed GO nanostructured system is observed to be non-toxic to MDA-MB-231 cell growth, in striking contrast to free G4 dendrimer and GO-G4 conjugate. The GO-G4-Fe-Cy nanostructured system characterized by multifunctionality suggests the merits of graphene for cellular bioimaging and the delivery of bioactives.

[PEGylated polyamidoamine dendrimer/methotrexate complex: pharmacokinetics and anti-tumor activity in normal and tumor-bearing rodents]

Generation 4 polyamidoamine (PAMAM) dendrimer was PEGylated with polyethylene glycol (PEG) at an average molecular weight 5 000 via amide bond. PAMAM and PEGylated PAMAM (PAMAM-PEG) dendrimer were used as drug nanocarriers. Methotrexate (MTX), an antineoplastic agent, was selected as a model drug. PAMAM/MTX and PAMAM-PEG/MTX complexes were prepared. The pharmacokinetic characters and anti-tumor activity of the PAMAM-PEG/MTX complex were studied as compared with MTX injection and PAMAM/MTX complex by intravenous injection in rats and S180 tumor bearing mice, separately. The plasma samples from normal rats were analyzed by HPLC method, and concentration-time data were analyzed using a non-compartmental analysis. Their anti-tumor effects in vivo were evaluated against S180 solid tumors in mice by measuring average tumor weight and calculating the inhibitory rate of tumor on day 17 after successive injections. The results showed that both plasma half-life and mean retention time (MRT) of the complexes were longer than that of MTX injection (P<0.01), while the area under the plasma concentration vs time curve (AUC) of PAMAM-PEG/MTX was the largest as compared with that of free drug and PAMAM/MTX complex (P<0.01). The inhibitory rate of tumor of PAMAM-PEG/MTX complex enhanced 2.1 and 1.8 times over that of free drug and PAMAM/MTX complex, respectively, indicating that PAMAM-PEG/MTX exhibited the highest antitumor activity. In summary, PEGylated PAMAM could be useful as a potential drug delivery carrier.

Poly(amino acid)s: Promising enzymatically degradable stealth coatings for liposomes

Poly(amino acid)s (PAAs) were evaluated as coating polymers for long-circulating liposomes. The pharmacokinetics of PAA-coated liposomes were assessed in rats. Prolonged circulation times were obtained, comparable to those reported for poly(ethylene glycol) (PEG)-liposomes. Besides, the enzymatic degradability of PAAs was studied. PAAs - in free as well as liposome-associated form - are degradable by proteases, which is beneficial for reducing the risks of accumulation in vivo. Furthermore, complement activation by PAA-liposomes was evaluated in vitro and in vivo. Like other liposome types, they appear to activate the complement system. However, a role of endotoxin contamination of the PAA-liposome formulations used cannot be excluded in our complement activation studies.

Synthesis, cellular transport, and activity of polyamidoamine dendrimer-methylprednisolone conjugates

Dendrimers have emerged as promising multifunctional nanomaterials for drug delivery due to their well-defined size and tailorability. We compare two schemes to obtain methylprednisolone (MP)-polyamidoamine dendrimer (PAMAM-G4-OH) conjugate. Glutaric acid (GA) was used as a spacer to facilitate the conjugation. In scheme A, PAMAM-G4-OH was first coupled to GA and then further conjugated with MP to obtain PAMAM-G4-GA-MP conjugates. This scheme yields a lower conjugation ratio of MP, presumably because of lower reactivity and steric hindrance for the steroid at the crowded dendrimer periphery. In scheme B, this steric hindrance was overcome by first preparing the MP-GA conjugate, which was then coupled to the PAMAM-G4-OH dendrimer. The (1)H NMR spectrum of the conjugate from scheme B indicates a conjugation of 12 molecules of MP with the dendrimer, corresponding to a payload of 32 wt %. In addition, conjugates were further fluorescent-labeled with fluoroisothiocynate (FITC) to evaluate the dynamics of cellular entry. Flow cytometry and UV/visible spectroscopic analysis showed that the conjugate is rapidly taken up inside the cell. Fluorescence and confocal microscopy images on A549 human lung epithelial carcinoma cells treated with conjugates show that the conjugate is mostly localized in cytosol. MP-GA-dendrimer conjugate showed comparable pharmacological activity to free MP, as measured by inhibition of prostaglandin secretion. These conjugates can potentially be further conjugated with a targeting moiety to deliver the drugs to specific cells in vivo.

Highly efficient, nonpeptidic oligoguanidinium vectors that selectively internalize into mitochondria

Oligoguanidinium-based cell delivery systems have gained broad interest in the drug delivery field since one decade ago. Thus, arginine-containing peptides as Tat or Antp, oligoarginine peptides, and derived peptoids have been described as shuttles for delivering nonpermeant drugs inside cancer cells. Herein we report a new family of tetraguanidinium cell penetrating vectors efficiently internalized in human tumor cells. Their high internalization, studied by confocal microscopy and flow cytometry, as well as their specific accumulation in mitochondria makes these new vectors likely vehicles for the targeted delivery of anticancer drugs to mitochondria.

Accessibility of nuclear chromatin by DNA binding polyamides

Pyrrole-imidazole polyamides bind DNA with affinities comparable to those of transcriptional regulatory proteins and inhibit the DNA binding activities of components of the transcription apparatus. If polyamides are to be useful for the regulation of gene expression in cell culture experiments, one pivotal issue is accessibility of specific sites in nuclear chromatin. We first determined the kinetics of uptake and subcellular distribution of polyamides in lymphoid and myeloid cells using fluorescent polyamide-bodipy conjugates and deconvolution microscopy. Then cells were incubated with a polyamide-chlorambucil conjugate, and the sites of specific DNA cleavage in the nuclear chromatin were assayed by ligation-mediated PCR. In addition, DNA microarray analysis revealed that two different polyamides generated distinct transcription profiles. Remarkably, the polyamides affected only a limited number of genes.

Steric stabilization of poly(2-(dimethylamino)ethyl methacrylate)-based polyplexes mediates prolonged circulation and tumor targeting in mice

BACKGROUND

Efficient tumor targeting of polymeric gene transfer systems (polyplexes) represents a major challenge. To establish tumor targeting after intravenous (IV) administration, the circulation lifetime of these systems should be sufficiently long. Since naked polyplexes are rapidly eliminated from the circulation after IV adminstration, strategies have to be developed to improve their pharmacokinetics.

METHODS

Complexes of plasmid DNA and poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA)-graft-PEG or AB di-block copolymers of pDMAEMA and PEG, as well as PEGylated complexes prepared via PEGylation of preformed complexes (postPEGylation), were evaluated for their physicochemical properties (size and charge) their interactions with blood constituents and transfection activity in vitro. The pharmacokinetics and biodistribution of PEG-polyplexes were studied in mice after IV administration. The degree of accumulation in two subcutaneous (SC) mouse tumors after IV administration was evaluated for the system with the longest circulation time.

RESULTS

It is shown that the surface charge of the pDMAEMA-polyplexes was effectively shielded by two PEGylation methods (i.e. the use of pDMAEMA-graft-PEG polymers and postPEGylation). The shielding effect was the highest for the postPEGylation method with PEG(20000), yielding polyplexes that hardly show interactions with blood components (i.e. albumin and erythrocytes) and show substantially prolonged circulation time in mice after IV administration. The superior colloidal stability and circulation kinetics of the postPEGylated polyplexes translated into tumor accumulation which amounted to about 3.5% of the injected dose per gram tumor tissue in a SC Neuro2A tumor model and to about 4.2% of the injected dose per gram tumor tissue in a SC C26 tumor model.

CONCLUSIONS

This study shows that postPEGylation of pDMAEMA-based polyplexes is the most attractive method to prepare polyplexes with long circulating properties. Tumor targeting capacity after intravenous administration was demonstrated in two subcutaneous tumor models.

Intravenous fate of poly(2-(dimethylamino)ethyl methacrylate)-based polyplexes

The objective of this study was to assess the in vivo fate of poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA)-based polyplexes after intravenous administration into mice. Circulation kinetics and tissue distribution in terms of plasmid localization and transfection efficiency were assessed. To gain more insight into the observed biodistribution and gene expression profile, the interaction of pDMAEMA-based polyplexes with blood components (erythrocytes and albumin) was investigated in vitro. In the case of i.v. injection of positively charged polyplexes at a dose of 30 microg DNA most of the radioactivity was found in the lungs and the liver 60 min after injection. In the case of pDMAEMA/DNA polyplexes with a negative charge, uptake occurred mainly by the liver. Administration of positively charged complexes at a 30 microg DNA dose resulted in reporter gene expression primarily in the lungs. Injection of negatively charged complexes and naked plasmid did not result in luciferase expression in any of the organs examined. In vitro turbidity experiments showed the induction of a charge dependent aggregation process upon addition of albumin to the polyplexes pointing out to the involvement of aggregate formation in the dominant lung uptake of the positively charged polyplexes. Also, incubations of polyplexes after pre-incubation with a physiological concentration of albumin with washed erythrocytes confirmed that polyplexes induce the formation of extremely large structures. This paper underlines the need for the design of systems with reduced interaction with blood components to promote the delivery of DNA to target tissues outside the lungs.

Preparation and characterization of folate-targeted pEG-coated pDMAEMA-based polyplexes

A folate-poly(ethylene glycol) conjugate capable of covalent coupling to primary amines present at the surface of polyplexes was developed. Coating of poly(dimethylaminomethyl methacrylate (pDMAEMA)-based polyplexes with this folate-pEG conjugate led to a sharp decrease of the zeta-potential, and a small increase in particle size. The size of the particles in isotonic medium did not change markedly in time demonstrating that rather stable particles were formed. The in vitro cellular toxicity of the pEGylated polyplexes with and without folate ligands was lowered considerably compared to uncoated polyplexes. The toxicity observed for the targeted pEGylated polyplexes was slightly higher than that of corresponding untargeted polyplexes, which might indicate an increased cellular association of targeted polyplexes. Transfection of OVCAR-3 cells in vitro was markedly increased compared to untargeted pEGylated polyplexes, suggesting targeted gene delivery.

Cellular uptake of N-methylpyrrole/N-methylimidazole polyamide-dye conjugates

The cellular uptake and localization properties of DNA binding N-methylpyrrole/N-methylimidazole polyamide-dye conjugates in a variety of living cells have been examined by confocal laser scanning microscopy. With the exception of certain T-cell lines, polyamide-dye conjugates localize mainly in the cytoplasm and not in the nucleus. Reagents such as methanol typically used to fix cells for microscopy significantly alter the cellular localization of these DNA-binding ligands.

Search for the optimal linker in tandem hairpin polyamides

In order to target specific DNA sequences >or=10 base pairs in size by minor groove binding ligands, a search for the optimal linker in dimers of hairpin polyamides was initiated. Two series of tandem polyamides ImPyIm-(R)[ImPyIm-(R)(H2N)gamma-PyPyPy-L](HN)gamma-PyPyPy-beta-Dp (1a-e), where L represents a series of 4-8 carbon long aliphatic amino acid linkers, and ImPyIm-(R)[ImPyIm-(R)(H2N)gamma-PyPyPyIm-L](HN)gamma-PyPyPy-beta-Dp (2a-e), where L represents a series of 2-6 carbon long aliphatic amino acid linkers, were synthesized and characterized by quantitative DNase I footprinting. beta, gamma and Dp represents beta-alanine, gamma-aminobutyric acid, and 3-(dimethylamino)propylamine, respectively. It was found that the five-carbon 5-aminovaleric acid (delta), is suitable to span one base-pair (bp) of DNA when incorporated into a tandem polyamide. ImPyIm-(R)[ImPyIm-(R)(H2N)gamma-PyPyPy-delta](HN)gamma-PyPyPy-beta-Dp (1b) binds the 10 bp binding-site 5'-AGTGAAGTGA-3' with equilibrium association constant K(a)=3.2 x 10(10) M(-1) and ImPyIm-(R)[ImPyIm-(R)(H2N)gamma-PyPyPyIm-delta](HN)gamma-PyPyPy-beta-Dp (2d) binds the 11 bp binding-site 5'-AGTGATAGTGA-3' with K(a)=9.7 x 10(9) M(-1). Tandem 1b also bind the 11 bp site but with lower affinity affording a 15-fold specificity for the shorter binding site. Replacing a methylene group in the amino acid linker with an oxygen atom to form tandem polyamide ImPyIm-(R)[ImPyIm-(R)(H2N)gamma-PyPyPy-E](HN)gamma-PyPyPy-beta-Dp (4) where E represents the ether linker, resulted in that an 80-fold specificity for the 10 bp binding site over the 11 bp site.

The fate of poly(2-dimethyl amino ethyl)methacrylate-based polyplexes after intravenous administration

Poly(2-dimethyl amino ethyl) methacrylate (pDMAEMA) cationic polymers have been shown to be efficient vectors for gene delivery in vitro. This contribution deals with the in vivo properties of polyplexes based on this polymer. In mice, pDMAEMA/[32P]-pLuc complexes distributed primarily to the lungs. The gene expression profile matched the biodistribution profile. In vitro turbidity experiments in serum showed severe aggregation upon addition of cationic polyplexes, pointing out the involvement of aggregates in the dominant lung uptake of the positively charged polyplexes. Incubations of polyplexes with albumin yielded a decline of the zeta potential of the complexes to negative values, making an electrostatic mechanism in the dominant lung uptake less likely. Hemagglutination experiments showed that the polyplexes induce the formation of extremely large structures when incubated with washed erythrocytes. Altogether, the present data indicate that aggregate formation and trapping of the formed aggregates in the lung capillary bed is probably responsible for the dominant lung uptake and transfection. Poly(ethylene)glycol (PEG) of the polymeric structures prevented the increase in the observed turbidity in serum seen with polyplexes and was also able to reduce interactions with erythrocytes. Currently, the in vivo fate of the PEGylated polyplexes is under investigation.

Localization, depuration, bioaccumulation and impairment of ion regulation associated with cationic polymer exposure in rainbow trout (Oncorhynchus mykiss)

1. Static exposure of rainbow trout, Oncorhynchus mykiss, to three commercial 14C-labelled cationic polymers (EDP, epichlorhydrin-dimethylamine; CYT, polyacrylamide ester; and STK, polyacrylamide amide) resulted in 14C being concentrated only in gill tissue. 2. Depuration studies examining the effect of humic acid (HA) on cationic polymer bound in gill tissue indicate that the binding is reversible with exposure to polymer-free water and polymer-free water with HA for each of the three polymers. 3. Analysis of blood pH, Na+, K+, total NH3 and Cl- after static water exposures to EDP (m.w. 50,000) at 7.5 mg EDP/l revealed a treatment related decrease in blood pH, from 7.1 to 6.6, accompanied by an increase in blood NH3 and evidence of severe impairment of ion regulation. 4. Repeated exposure to the cationic polymers did not result in increases in the 14C concentration in gill tissue suggesting that bioaccumulation of the polymers does not occur. 5. These data suggest that the gill is the site of toxicity for these cationic polymers and that their toxic effects involve gill function and ion regulation rather than systemic actions on internal organs.

Vector-mediated delivery of a polyamide ("peptide") nucleic acid analogue through the blood-brain barrier in vivo

Polyamide ("peptide") nucleic acids (PNAs) are molecules with antigene and antisense effects that may prove to be effective neuropharmaceuticals if these molecules are enabled to undergo transport through the brain capillary endothelial wall, which makes up the blood-brain barrier in vivo. The model PNA used in the present studies is an 18-mer that is antisense to the rev gene of human immunodeficiency virus type 1 and is biotinylated at the amino terminus and iodinated at a tyrosine residue near the carboxyl terminus. The biotinylated PNA was linked to a conjugate of streptavidin (SA) and the OX26 murine monoclonal antibody to the rat transferrin receptor. The blood-brain barrier is endowed with high transferrin receptor concentrations, enabling the OX26-SA conjugate to deliver the biotinylated PNA to the brain. Although the brain uptake of the free PNA was negligible following intravenous administration, the brain uptake of the PNA was increased at least 28-fold when the PNA was bound to the OX26-SA vector. The brain uptake of the PNA bound to the OX26-SA vector was 0.1% of the injected dose per gram of brain at 60 min after an intravenous injection, approximating the brain uptake of intravenously injected morphine. The PNA bound to the OX26-SA vector retained the ability to bind to synthetic rev mRNA as shown by RNase protection assays. In summary, the present studies show that while the transport of PNAs across the blood-brain barrier is negligible, delivery of these potential neuropharmaceutical drugs to the brain may be achieved by coupling them to vector-mediated peptide-drug delivery systems.