Evaluation of drug delivery following the administration of magnetic albumin microspheres containing adriamycin to the rat

In vivo restoration of dystrophin expression in mdx mice using intra-muscular and intra-arterial injections of hydrogel microsphere carriers of exon skipping antisense oligonucleotides

Duchenne muscular dystrophy (DMD) is a genetic disease caused by a mutation in the X-linked Dytrophin gene preventing the expression of the functional protein. Exon skipping therapy using antisense oligonucleotides (AONs) is a promising therapeutic strategy for DMD. While benefits of AON therapy have been demonstrated, some challenges remain before this strategy can be applied more comprehensively to DMD patients. These include instability of AONs due to low nuclease resistance and poor tissue uptake. Delivery systems have been examined to improve the availability and stability of oligonucleotide drugs, including polymeric carriers. Previously, we showed the potential of a hydrogel-based polymeric carrier in the form of injectable PEG-fibrinogen (PF) microspheres for delivery of chemically modified 2'-O-methyl phosphorothioate (2OMePs) AONs. The PF microspheres proved to be cytocompatible and provided sustained release of the AONs for several weeks, causing increased cellular uptake in mdx dystrophic mouse cells. Here, we further investigated this delivery strategy by examining in vivo efficacy of this approach. The 2OMePS/PEI polyplexes loaded in PF microspheres were delivered by intramuscular (IM) or intra-femoral (IF) injections. We examined the carrier biodegradation profiles, AON uptake efficiency, dystrophin restoration, and muscle histopathology. Both administration routes enhanced dystrophin restoration and improved the histopathology of the mdx mice muscles. The IF administration of the microspheres improved the efficacy of the 2OMePS AONs over the IM administration. This was demonstrated by a higher exon skipping percentage and a smaller percentage of centered nucleus fibers (CNF) found in H&E-stained muscles. The restoration of dystrophin expression found for both IM and IF treatments revealed a reduced dystrophic phenotype of the treated muscles. The study concludes that injectable PF microspheres can be used as a carrier system to improve the overall therapeutic outcomes of exon skipping-based therapy for treating DMD.

Brain Targeting of anti-HIV Nucleosides: in vitro and in vivo Evaluation of 6-chloro-2′,3′-dideoxypurine, a Lipophilic Prodrug of 2′,3′-dideoxyinosine

Lipophilic 6-halo-2′,3′-dideoxypurine nucleosides may be useful prodrugs for the targeting of 2′,3′-dideoxyinosine (ddl) to the central nervous system. The purpose of this study was to evaluate the potential effectiveness of 6-chloro-2′,3′-dideoxypurine (6-CI-ddP) for the targeting of ddl to the brain. In vitro studies indicated that the adenosine deaminase-mediated biotransformation of 6-CI-ddP to ddl was more rapid in mouse brain homogenate than in mouse serum. The brain distribution of 6-CI-ddP and ddl was assessed in vivo in mice following intravenous and oral administration of the prodrug or parent drug. Brain concentrations of ddl were similar after intravenous administration of 6-CI-ddP or ddl. However, after oral administration of the 6-CI-ddP prodrug, significantly greater concentrations of ddl were seen in the brain compared to those found after oral administration of ddl. The brain:serum AUG ratio (expressed as a percentage) of ddl after intravenous administration of 50 mg kg−1 of the active nucleoside was 3%. Following oral administration of 250 mg kg−1 ddl, low concentrations of ddl were detected in the brain. Brain:serum AUC ratios following intravenous and oral administration of the prodrug 6-CI-ddP were 19–25%. Thus, brain:serum AUC ratios were 6- to 8-fold higher after prodrug administration than those obtained after administration of the parent nucleoside. Oral administration of 6-CI-ddP yielded concentrations of ddl in the brain similar to those obtained following intravenous administration. The results of this study provide further evidence that 6-CI-ddP may be a useful prodrug for delivering ddl to the central nervous system, particularly after oral administration.

Preparation of adriamycin magnetic albumin microspheres and their experimental antitumor effects in vitro and in vivo

The adriamycin magnetic microspheres (ADM-MAMs) were prepared by the heat-stabilized protein methods. Their physico-chemical properties were examined; their cytotoxicities against tumor cells in vitro were assayed by a modified MTT method, and their effects were observed on the implanted gastric tumor in Wistar rats given ADM-MAMs via alimentary canal at the presence of the external magnetic fields. The results showed that the ADM-MAMs were successfully prepared and had cytotoxic effect on tumor cells in vitro similar to the free ADM (P > 0.05). The inhibitory effects of ADM-MAMs on the implanted gastric tumor in vivo were significantly increased as compared with the controls (P < 0.01). Our results suggested that ADM-MAMs were a new type of adriamycin (ADM) preparation and its form alteration did not affect its anticancer effects.

Lung-targeted delivery system of curcumin loaded gelatin microspheres

The purpose of the study is to design and evaluate curcumin loaded gelatin microspheres (C-GMS) for effective drug delivery to the lung. C-GMS was prepared by the emulsification-linkage technique and the formulation was optimized by orthogonal design. The mean encapsulation efficiency and drug loading of the optimal C-GMS were 75.5 ± 3.82 % and 6.15 ± 0.44%, respectively. The C-GMS presented a spherical shape and smooth surface with a mean particle diameter of 18.9 μm. The in vitro drug release behavior of C-GMS followed the first-order kinetics. The tissue distribution showed that the drug concentrations at lung tissue for the C-GMS suspension were significantly higher than those for the curcumin solution, and the Ce for lung was 36.19. Histopathological studies proved C-GMS was efficient and safe to be used as a passive targeted drug delivery system to the lung. Hence, C-GMS has a great potential for the targeted delivery of curcumin to the lung.

Preparation of the core-shell structure adriamycin lipiodol microemulsions and their synergistic anti-tumor effects with diethyldithiocarbamate in vivo

We prepared the core-shell structure adriamycin lipiodol microemulsions (ADM-CSLMs) and evaluated their in vivo antitumor effects in combination with Diethyldithiocarbamate (DDC). Two types of ADM-CSLMs, adriamycin liposome-lipiodol microemulsion(ADM-LLM) and adriamycin microsphere lipiodol microemulsion (ADM-MLM), were prepared through the emulsification method. The drug loading and encapsulation efficiency of ADM-CSLMs were measured by the high-performance liquid chromatograph (HPLC). The size and shape of the ADM-CSLMs were determined by an atom force microscopy (AFM), a transmission electron microscopy (TEM), and a particle size analyzer, respectively. The synergistic effects of DDC and ADM-CSLMs for cancer treatment of carcinoma drug-resistance cell was evaluated by the MTT method, the activation of superoxide dismutase (SOD) was detected by chemiluminescence, and the ADM accumulation in cells was measured by flow cytometry. Walker-256 carcinoma was transplanted to the livers of the male SD rats, ADM-CSLMs were administrated to the livers of the rats by intervention hepatic artery embolization through microsurgery. The tumor growth and animal survival were evaluated. The results show that the average diameter of ADM-LLM and ADM-MLM were 4.23 ± 1.2 μm and 4.67 ± 1.4 μm, respectively, and their ADM encapsulation efficiency were 83.7% and 87.2% with respect to loading efficiency of 82 μg/ml and 91 μg/ml. The tumor growth and animal survival in two of the ADM-CSLMs combined with DDC groups were significantly higher than that of ADM only treatment, ADM liposome combined with DDC (P < 0.01), as well as the ADM microsphere combined with DDC (P < 0.01). Therefore, ADM-CSLMs are useful carriers for the treatment of carcinoma and their anti-tumor effect can be enhanced by DDC in a suitable concentration.

Magnetic nanoparticle drug carriers and their study by quadrupole magnetic field-flow fractionation

Magnetic nanoparticle drug carriers continue to attract considerable interest for drug targeting in the treatment of cancers and other pathological conditions. The efficient delivery of therapeutic levels of drug to a target site while limiting nonspecific, systemic toxicity requires optimization of the drug delivery materials, the applied magnetic field, and the treatment protocol. The history and current state of magnetic drug targeting is reviewed. While initial studies involved micrometer-sized and larger carriers, and work with these microcarriers continues, it is the sub-micrometer carriers or nanocarriers that are of increasing interest. An aspect of magnetic drug targeting using nanoparticle carriers that has not been considered is then addressed. This aspect involves the variation in the magnetic properties of the nanocarriers. Quadrupole magnetic field-flow fractionation (QMgFFF) is a relatively new technique for characterizing magnetic nanoparticles. It is unique in its capability of determining the distribution in magnetic properties of a nanoparticle sample in suspension. The development and current state of this technique is also reviewed. Magnetic nanoparticle drug carriers have been found by QMgFFF analysis to be highly polydisperse in their magnetic properties, and the strength of response of the particles to magnetic field gradients is predicted to vary by orders of magnitude. It is expected that the least magnetic fraction of a formulation will contribute the most to systemic toxicity, and the depletion of this fraction will result in a more effective drug carrying material. A material that has a reduced systemic toxicity will allow higher doses of cytotoxic drugs to be delivered to the tumor with reduced side effects. Preliminary experiments involving a novel method of refining a magnetic nanoparticle drug carrier to achieve this result are described. QMgFFF is used to characterize the refined and unrefined material.

Significant delivery of tacrine into the brain using magnetic chitosan microparticles for treating Alzheimer's disease

Alzheimer's disease (AD) is a progressive degenerative disorder of the brain characterized by a slow, progressive decline in cognitive function and behavior. As the disease advances, persons have a tough time with daily tasks like using the phone, cooking, handling money or driving the car. AD affects 15 million people worldwide and it has been estimated that AD affects 4.5 million Americans. Tacrine is a reversible cholinesterase inhibitor used for treating mild to moderate AD. In the present study, an attempt was made to target the anti-Alzheimer's drug tacrine in the brain by using magnetic chitosan microparticles. The magnetic chitosan microparticles were prepared by emulsion cross-linking. The formulated microparticles were characterized for process yield, drug loading capacity, particle size, in vitro release, release kinetics and magnetite content. The particle size was analyzed by scanning electron microscope. The magnetite content of the microparticles was determined by atomic absorption spectroscopy. For animal testing, the microparticles were injected intravenously after keeping a suitable magnet at the target region. The concentrations of tacrine at the target and non-target organs were analyzed by HPLC. The magnetic chitosan microparticles significantly increased the concentration of tacrine in the brain in comparison with the free drug.

Magnetic colloids as drug vehicles

This review article is a description of the present status of magnetic drug delivery systems (DDS). These are colloidal dispersions of composite nanoparticles consisting of a (polymeric or inorganic) biocompatible matrix and magnetic units, and designed to load and release therapeutic drugs. The matrix, together perhaps with adsorbed polymers or polyelectrolytes, provides the DDS with additional colloidal stability and eventually control of the immune response, and the magnetic inclusions have the goal of providing magnetic guidance. The techniques used in the production of the particles are described. The large surface/volume ratio of the particles brings about a superlative importance of the interface aspects, which are depicted in some detail. Attention is also paid to the possibilities that magnetic DDS offer to be guided by magnetic fields, and to their fate upon entering in contact with the blood proteins and the tumor cells. A description of in vitro and in vivo biodistribution experiments helps in this description. The number of animal experiments performed using magnetic DDS is rather large, but results in humans are far from being sufficient in number, something easily understood. The hopes for improvement and the challenges that must be overcome are described in the closing section.

Radical Crosslinked Albumin Microspheres as Potential Drug Delivery Systems: Preparation and In Vitro Studies

This article reports on the preparation of acryloylated bovine serum albumin microspheres and the evaluation of their employment in drug delivery areas. The influence of preparation parameters on albumin microspheres and the chemicophysical properties of loaded drugs were investigated. In particular, we focussed on acylation albumin degree and the amount of acryloylated albumin against comonomer in the polymerization step. Finally the release profile took into consideration the interaction drug-matrix, the fuctionalization degree of albumin, and the water affinity of matrix.

Radical cross-linked albumin microspheres as potential drug delivery systems: preparation and in vitro studies

The aim of this research is the preparation of acryloylated bovine serum albumin microspheres and the evaluation of their employment in drug delivery. The influence of preparation parameters on albumin microspheres and the chemicophysical properties of loaded drugs were investigated. In particular, we focused our attention on acylation albumin degree, amount of acryloylated albumin against comonomer in the polymerization step, and finally the release profile. We considered on the interaction drug-matrix, the fuctionalization degree of albumin, and the water affinity of matrix.

In vivo tumor targeting of tumor necrosis factor-alpha-loaded stealth nanoparticles: effect of MePEG molecular weight and particle size

The aim of this study is to reveal the influence of methoxypolyethyleneglycol (MePEG) molecular weight and particle size of stealth nanoparticles on their in vivo tumor targeting properties. Three sizes (80, 170 and 240nm) of poly methoxypolyethyleneglycol cyanoacrylate-co-n-hexadecyl cyanoacrylate (PEG-PHDCA) nanoparticles loading recombinant human tumor necrosis factor-alpha (rHuTNF-alpha) were prepared at different MePEG molecular weights (MW=2000, 5000 and 10,000) using double emulsion method. The opsonization in mouse serum was evaluated by Coomassie brilliant blue staining of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Phagocytosis was evaluated by incubating (125)I-rHuTNF-alpha-loaded nanoparticles with mouse macrophages (RAW264.7). The pharmacokinetics, biodistribution and tumor targeting studies were performed in S-180 tumor-bearing mice. Higher MePEG molecular weight provided thicker fixed aqueous layer thickness (FALT) and smaller particle size offered higher surface MePEG density. The serum protein adsorption and phagocytic uptake were markedly decreased for the nanoparticles with higher MePEG molecular weight or smaller size. The particles (80nm) made of PEG(5000)-PHDCA, possessing a thicker FALT (5.16nm) and a shortest distance (0.87nm) between two neighboring MePEG chains, showed the strongest capacity of decreasing protein adsorption and phagocytic uptake. These particles extended the half-life of rHuTNF-alpha in S-180 tumor-bearing mice by 24-fold (from 28.2 min to 11.33 h), elevated the rHuTNF-alpha peak concentration in S-180 tumors by 2.85-fold and increased the area under the intratumoral rHuTNF-alpha concentration curve by 7.44-fold. The results of the present study showed PEG-PHDCA nanoparticles with higher MePEG molecular weight and smaller particle size could achieve higher in vivo tumor targeting efficiency.

Synthesis and surface engineering of iron oxide nanoparticles for biomedical applications

Superparamagnetic iron oxide nanoparticles (SPION) with appropriate surface chemistry have been widely used experimentally for numerous in vivo applications such as magnetic resonance imaging contrast enhancement, tissue repair, immunoassay, detoxification of biological fluids, hyperthermia, drug delivery and in cell separation, etc. All these biomedical and bioengineering applications require that these nanoparticles have high magnetization values and size smaller than 100 nm with overall narrow particle size distribution, so that the particles have uniform physical and chemical properties. In addition, these applications need special surface coating of the magnetic particles, which has to be not only non-toxic and biocompatible but also allow a targetable delivery with particle localization in a specific area. To this end, most work in this field has been done in improving the biocompatibility of the materials, but only a few scientific investigations and developments have been carried out in improving the quality of magnetic particles, their size distribution, their shape and surface in addition to characterizing them to get a protocol for the quality control of these particles. Nature of surface coatings and their subsequent geometric arrangement on the nanoparticles determine not only the overall size of the colloid but also play a significant role in biokinetics and biodistribution of nanoparticles in the body. The types of specific coating, or derivatization, for these nanoparticles depend on the end application and should be chosen by keeping a particular application in mind, whether it be aimed at inflammation response or anti-cancer agents. Magnetic nanoparticles can bind to drugs, proteins, enzymes, antibodies, or nucleotides and can be directed to an organ, tissue, or tumour using an external magnetic field or can be heated in alternating magnetic fields for use in hyperthermia. This review discusses the synthetic chemistry, fluid stabilization and surface modification of superparamagnetic iron oxide nanoparticles, as well as their use for above biomedical applications.

RGD-anchored magnetic liposomes for monocytes/neutrophils-mediated brain targeting

Negatively charged magnetic liposomes were prepared using soya lecithin (Soya PC), cholesterol and phosphatidyl serine (PS) for their preferential presentation to circulating blood phagocytes (monocytes and neutrophils). PS ratio was optimized in terms of drug and magnetite loading, in vitro magnetic responsiveness and ex vivo monocytes/neutrophils uptake. RGD peptide was covalently coupled to the negatively charged liposomes composed of PC, cholesterol, PS and phopsphatidyl ethanolamine (PE) via carbodiimide-mediated coupling. In vivo cellular sorting study under magnetic guard indicated an increase in relative count of neutrophils and monocytes. Results suggest that selective uptake of RGD-anchored magnetic liposomes by these cells imparts them magnetic property. High levels of a model drug diclofenac sodium was quantified in target organ brain. In case of negatively charged uncoated magnetic liposomes brain levels of the drug was 5.95-fold compared to free drug and 7.58-fold in comparison to non-magnetic formulation, while for RGD-coated magnetic liposomes this ratio was 9.1-fold compared to free drug solution, 6.62-fold compared to non-magnetic RGD-coated liposomes and 1.5-fold when compared to uncoated magnetic liposomes. Liver uptake was significantly bypassed (37.2% and 48.3% for uncoated and RGD-coated magnetic liposomes, respectively). This study suggested the potential of negatively charged and RGD-coated magnetic liposomes for monocytes/neutrophils-mediated active delivery of drugs to relatively inaccessible inflammatory sites, i.e. brain. The study opens a new perspective of active delivery of drugs for a possible treatment of cerebrovascular diseases.

Correlation between drug release kinetics from proteineous matrices and protein folding: elasticity and compressibility study

Naproxen sodium (NS) release mechanism from proteineous matrices based on egg albumin (EA) and bovine serum albumin (BSA) was investigated by several physico-chemical methods. The gel strength, modulus of elasticity and erosion properties of the matrices were studied and correlated with drug release kinetics. The results revealed that NS release rate from EA and BSA matrices was markedly different, indicating the significant role of protein nature and conformation on matrix behavior. Unexpectedly it was found that incorporation of NS to EA matrix increased gel strength and modulus of elasticity and decreased matrix erosion. This effect was dependent on NS concentration in the matrix. In contrast to EA, BSA behaved as a non-gelling matrix and was unable to retard drug release because of its high solubility. The influence of NS on protein folding and compressibility in protein solutions was studied using densitometric and ultrasonic techniques. Adiabatic compressibility measurements revealed that NS caused unfolding of EA, an effect which led to a decrease in EA intrinsic compressibility and the exposure of atomic side groups buried in protein interior. Unfolding of EA led to an increase of modulus of elasticity in solution (measured by ultrasonic velocimetry technique) which is in correlation with the modulus of elasticity measurements of gelled tablets (measured by Instron). In concentrated EA solutions, the results showed a large increase in EA compressibility and ultrasonic absorption in the presence of NS indicating a strong aggregation of the denatured state of EA. Regarding BSA, the results suggested that NS affected the packing of the protein interior, transforming it to a molten globule intermediate state, an effect that led to an increase in BSA compressibility. At high BSA concentrations, aggregation of the molten globule state was observed as indicated by an increase of BSA compressibility and ultrasonic absorption values.

Enhanced hepatocyte uptake and liver targeting of methotrexate using galactosylated albumin as a carrier

Liver targeting of drugs has wide therapeutic implications due to numerous liver-related diseases. Using conjugates of methotrexate (MTX) to variously galactosylated bovine serum albumin (BSA), we studied whether we could enhance the liver targeting of MTX, a model drug, via galactose receptors selectively abundant on the hepatocytes. Here, we report that the galactosylation of the carrier protein BSA significantly enhanced the hepatocyte uptake and liver targetability of MTX. In vitro, the amount of MTX taken up by rat hepatocytes was positively correlated with the galactose content in BSA. MTX conjugates were relatively stable in plasma, but released MTX with time in liver homogenates. These results imply that the conjugates would exert low toxicity in the blood, but have therapeutic activity in the liver by liberating MTX. In vivo, MTX-galactosylated BSA conjugates (MTX-L(24)BSA) showed significantly different pharmacokinetics from free MTX or MTX-BSA conjugates. The plasma level of free MTX rapidly declined in a biexponential fashion with an apparent terminal half-life of 0.35 h. MTX-BSA conjugates showed the slowest decline with an apparent terminal half-life of 6 h, whereas MTX-L(24)BSA showed a biphasic pattern; a rapid distributive phase with a half-life of 0.567 h and a slow terminal phase. MTX-L(24)BSA showed the highest liver targetability, when evaluated in terms of two indices based on the area under the total amount of radioactivity-time curve (AUQ); Te*(liver), % AUQ(liver) to total AUQ, and te*, the ratio of AUQ(liver) to AUQ(kidney). Compared with free MTX and MTX-BSA, MTX-L(24)BSA showed about twofold higher Te*(liver) of 87.5%. The te* of MTX-L(24)BSA was 25- and fourfold higher than those of free MTX and MTX-BSA, respectively. Moreover, MTX-L(24)BSA showed a gradual increase in the therapeutically active intact form of MTX in the liver while showing the lowest level of intact MTX in the kidney. These results suggest that galactosylated BSA has a great potential as an hepatocyte-directed and more effective liver targeting carrier of drugs for liver diseases.

Enhanced brain tumor selectivity of cationic magnetic polysaccharide microspheres

A novel cationic delivery system composed of magnetic aminodextran microspheres (MADM) 1-2 microm in diameter was evaluated along with neutral magnetic dextran microspheres (MDM) for their ability to target intracerebral rat glioma-2 (RG-2) tumors in vivo. The tissue distribution of the microspheres was determined following intraarterial injection (25 mg/kg) over 2 min in male Fisher 344 rats bearing RG-2 tumors as well as normal animals with a magnetic field of 0 or 0.6 T applied to the brain for 30 min. Animals were sacrificed at 30 min or 6 h post-injection after which the microspheres were recovered from various tissues and analyzed for magnetite (Fe3O4) content by atomic absorption. Overall, administration of cationic MADM and neutral MDM particles in normal animals resulted in low brain tissue concentrations with the highest concentrations observed in lung and spleen tissue. In contrast, studies in brain tumor bearing animals resulted in cationic MADM particles concentrating in brain tumor at levels significantly higher than neutral MDM particles (p = 0.0111). Cationic particles were also retained in brain tissue over a longer period of time compared to neutral particles (p = 0.0161) with MADM tumor concentrations decreasing only 4% after 6h compared with a 32% decrease for MDM. Application of a magnetic field failed to produce any significant effect on tissue distribution due to high variability in these groups, but generally resulted in increased brain concentrations and decreased non-target tissue concentrations. TEM analysis of brain tissue sections in tumor animals also revealed differences in particle distribution with MADM particles observed in the interstitial space and MDM particles trapped in the vasculature. In summary, particle charge, state of the vascular endothelium and time significantly influenced particle distribution contributing to the ability of MADM to selectively target brain tumor and supports further investigation of magnetic cationic microspheres as a targeted drug delivery system for brain tumors.

Distribution of small magnetic particles in brain tumor-bearing rats

Small (10-20 nm) uncharged magnetic particles (SMP) were evaluated for their ability to target intracerebral rat glioma-2 (RG-2) tumors in vivo. In an effort to determine the influence of particle size on blood-tumor barrier uptake, the tissue distribution of the injected particles was evaluated following intraarterial injection (4 mg/kg SMP) in male Fisher 344 rats bearing RG-2 tumors with a magnetic field of 0 G or 6000 G applied to the brain for 30 min. Animals were sacrificed at 30 min or 6 h post-injection after which tissues were collected and analyzed for magnetite content. In the presence of a magnetic field, SMP localized in brain tumor tissue at levels of 41-48% dose/g tissue after 30 min and 6 h respectively, significantly greater than non-target tissues. In the absence of a magnetic field only 31-23% dose/g tissue was achieved for the same time points. Tumor targeting of the SMP for brain tumor was demonstrated by large target selectivity indexes (ts) of 2-21 for normal brain tissue, indicating a 2-21 fold increase in concentrations compared to normal brain. In comparison with larger (1 micron) diameter magnetic particles, SMP concentrated in brain tumor at significantly higher levels than magnetic neutral dextran (p = 0.0003) and cationic aminodextran (p = 0.0496) microspheres previously studied. TEM analysis of brain tissue revealed SMP in the interstitial space of tumors, but only in the vasculature of normal brain tissue. These results suggest that changes in the vascular endothelium of tumor tissue promote the selective uptake of SMP and provide a basis for the design of new small drug-loaded particles as targeted drug delivery systems for brain tumors.

Magnetic targeting of thermosensitive magnetoliposomes to mouse livers in an in situ on-line perfusion system

We recently reported the preparation and in vitro targeting of dextran magnetite (DM)-incorporated thermosensitive liposomes, namely thermosensitive magnetoliposomes (TMs) [Viroonchatapan et al. Pharm. Res. 12 1176-1183 (1995)]. The current study was designed to determine whether these novel liposomes can be targeted to the mouse liver with the aid of an extracorporeal magnet. An on-line liver perfusion system consisting primarily of a sample injector, permanent magnets, and a fluorescence detector was established for a real-time measurement of targeting efficiency of TMs containing calcein as a fluorescent marker. Normal and reticuloendothelial system (RES)-blocked livers from mice were used for the perfusion experiments. In the RES-blocked livers, percentage holdings of TMs were 73-80% and 26-45% in the presence and absence of magnetic field, respectively, indicating an efficient targeting of TMs with a targeting advantage index (TAI) of 1.6-3.1. On the other hand, TAI in the normal livers was found to be 1.1-1.4 and less than that in the RES-blocked livers, suggesting a role of RES uptake of TMs. The effects of DM concentrations in TM suspensions on the percentage holding of TMs were shown to be minor. Liposome concentration dependence was observed for hepatic uptake of TMs, possibly because of the saturation of phagocytosis by Kupffer cells. The present results suggest that TMs would be useful in future cancer treatment by magnetic targeting combined with drug release in response to hyperthermia.

Preparation and characterization of polyethyl-2-cyanoacrylate nanocapsules containing antiepileptic drugs

Biocompatible and biodegradable colloidal drug delivery systems can be obtained by means of in situ polymerization of alkylcyanoacrylate. In particular, nanocapsules of polyethylcyanoacrylate (PECA) were prepared by adding the monomer to an organic phase, consisting of Miglyol 812 and an organic solvent (ethanol, acetone or acetonitrile), and subsequently mixing the organic phase with an aqueous phase containing Pluronic F68 at different concentrations. The possible mechanism of formation and the influence of preparation conditions on the quality of nanocapsule formulations were investigated by freeze-fracture electron microscopy and laser light scattering using both the inverse Laplace transform and the standard cumulant analysis for data fitting. High-quality nanocapsule systems were obtained using an aprotic fully water-miscible organic solvent such as acetone. The presence of ethanol led to the formation of both nanospheres and nanocapsules. The concentrations of nonionic surfactant in the aqueous phase of monomer in the organic phase did not influence the kind of colloidal suspension obtained. The oil simply plays the role of monomer support. The diameter of PECA nanoparticles (nanospheres and nanocapsules) ranged from 100 to 400 nm. Three antiepileptic drugs (Ethosuximide, 5,5-diphenyl hydantoin and carbamazepine) were entrapped in PECA nanocapsules. The loading capacity of PECA nanocapsules, prepared using acetone as organic solvent, varied from 1% to 11% (drug/dried material) as a function of the solubility (affinity) of the different drugs with the oil core. This parameter also influenced the release from PECA nanocapsules, which was slower for drugs with a higher affinity for Miglyol 812. By encapsulating the three antiepileptic drugs in the PECA nanocapsules, it was possible to achieve controlled drug release. The mechanism of drug release from PECA nanocapsules was mainly diffusion from the oil core through the intact polymer barrier.

Tissue distribution of methotrexate following administration as a solution and as a magnetic microsphere conjugate in rats bearing brain tumors

A novel magnetic microsphere-methotrexate (MM-MTX) drug delivery system was synthesized and evaluated in rats bearing rat glioma-2 (RG-2) tumors. Methotrexate was linked to the surface of the magnetic particle via an aminohexanol linker that would release free drug following hydrolysis. Male Fischer 344 rats bearing RG-2 tumors were administered 3 mg/kg of methotrexate (MTX) either as MM-MTX or as a solution (MTX-S) over 5 min. A 6000 gauss magnetic field was applied for 15 min from the end of MM-MTX administrations. Serial sacrifices were conducted at 15 min, 30 min and 45 min after drug administrations, organs collected, and analyzed for total MTX by a radioassay. At all times, MTX right brain (ipsilateral), brain tumor, and left brain concentrations were approximately 3.5 to 5-fold greater in the MM-MTX group compared to the MTX-S group. MTX concentrations in all other organs were less following administration of MM-MTX than MTX-S except in lung at 30 and 45 min. The targeting efficacy, an index for site-specificity, for both MM-MTX and MTX-S were similar and indicated some enhancement in MTX localization in brain tumor. Confocal and conventional light microscopic analyses demonstrated a diffuse distribution of MM-MTX in tumor consistent with extravascular uptake, whereas a predominant capillary distribution of MM-MTX was observed in normal brain. Following 45 min, the animals treated with MM-MTX died possibly due to redistribution of particles to the lung. This toxicity was dose-dependent. High brain MTX concentrations coupled with extravascular uptake of MM-MTX provide a basis for further investigations with this novel drug delivery system.

Magnetically responsive photosensitizing reagents for possible use in photoradiation therapy

The ability of a magnetically responsive material to function as a carrier for photosensitizing agents for use in photoradiation therapy (PRT) has been examined in vitro. The photosensitizer has been attached to the magnetically responsive matrix (Dynabeads) by non-specific adsorption, Intralipid-mediated adsorption and poly-L-lysine mediated adsorption. In these studies, it has been demonstrated that conditions of attachment of photosensitizer to the matrix may be adapted in order to facilitate a diffuse or highly localized photo-toxic effect on target cells in vitro. The authors believe that this system may represent a novel approach to targeting photosensitizing agents to specific areas, thereby circumventing some of the problems associated with conventional photoradiation therapy (PRT), particularly in hollow organs.

Magnetically responsive diclofenac sodium-loaded erythrocytes: preparation and in vitro characterization

Diclofenac sodium-bearing magnetic erythrocytes were prepared using a preswell technique. The optimum loading of drug and magnetite achieved were 63-73 and 12-18 per cent, respectively. Drug-loaded erythrocytes and drug-loaded magnetic erythrocytes were characterized for in vitro drug and haemoglobin release, magnetic responsiveness, osmotic fragility, turbulence shock, morphology and percentage cell recovery. The drug-loaded magnetic erythrocytes were found less resistant to osmotic and turbulence shock when compared with the normal and drug-loaded erythrocytes. However, in optimum concentration erythrocytes tolerated drug and coated magnetite appreciably. The drug-loaded magnetic erythrocytes responded effectively for an external magnetic field of 8.0 kOe. The study suggested the potentiality of diclofenac sodium-loaded magnetic erythrocytes, for active delivery of drug to painful inflamed joints.

Preparation and in vitro characterization of a magnetically responsive ibuprofen-loaded erythrocytes carrier

The erythrocytes were loaded with ibuprofen and magnetite (ferrofluids) using the pre-swell technique. Various process variables including drug concentration, magnetite concentration, sonication of ferrofluids that could affect the loading of drug and magnetite were optimized. The loaded erythrocytes were characterized for in vitro drug efflux, haemoglobin release, morphology, osmotic fragility, turbulence shock, in vitro magnetic responsiveness and percentage cell recovery. In optimum concentration erythrocytes could tolerate ibuprofen as no appreciable detrimental effects were noticed on cell morphology, osmotic fragility, and turbulence shock, when compared with normal erythrocytes. However, magnetite showed some detrimental effect on erythrocytes. A drug release profile from the cellular system was observed to follow approximate zero-order kinetics. The loaded cells effectively responded for an external magnetic field of 8.0 KOe.

Targeting anticancer drugs to the brain. I: Enhanced brain delivery of oxantrazole following administration in magnetic cationic microspheres

A magnetic cationic microsphere delivery system, prepared from the polysaccharide chitosan and containing oxantrazole (OX), was examined for its ability to enhance brain delivery of OX compared to administration of OX in solution (OX-S). Magnetic chitosan microspheres containing OX (MCM-OX) and OX-S were administered intraarterially to male Fischer 344 rats at OX doses of 0.1 mg/kg and 0.5 mg/kg with a magnetic field of 6000 G applied to the brain for 30 min. Animals were sacrificed at 30 min and 120 min after MCM-OX and OX-S treatments, and multiple tissues were collected and analyzed for OX by HPLC. A statistical analysis of the effects of treatment, OX dose, and time on total OX in each sampled tissue was made. MCM-OX significantly increased OX brain concentrations compared to those achieved with OX-S treatments, concentrations after MCM-OX being a minimum of 100-fold greater. Within the MCM-OX treatment groups, ipsilateral OX concentrations were much greater, indicating target organ selectivity. A most interesting finding was that OX brain concentrations were similar at 120 min and 30 min after MCM-OX treatment. Thus, even in the absence of the magnetic field, MCM-OX were retained in the brain, possibly through cationic-anionic interactions with the blood-brain barrier.

Optimized formulation of magnetic chitosan microspheres containing the anticancer agent, oxantrazole

A combined emulsion/polymer cross-linking/solvent evaporation technique was used to prepare magnetic chitosan microspheres (MCM) containing the anticancer drug, oxantrazole. A central composite experimental design was used to simultaneously evaluate a variety of formulation factors on a number of response variables, such as the percentage of oxantrazole entrapped in the MCM. In association with the study design, statistical optimization procedures indicated the factors that significantly influence MCM preparation and what levels of the factors are needed to produce optimum MCM. Entrapment of anticancer agents into biodegradable microspheres is difficult because of low aqueous drug solubility and porosity of the particles. The latter effect was circumvented by a chitosan cross-linking step that resulted in approximately 3% (w/w) oxantrazole entrapment in the MCM via the optimization procedures. The combined formulation and statistical optimization strategy provide a basis to develop other microparticulate systems and led to a dosage form that can be used for future in vivo investigations.

Targeted delivery of low dose doxorubicin hydrochloride administered via magnetic albumin microspheres in rats

The efficacy of magnetic albumin microspheres in the targeted delivery of an anti-cancer agent, doxorubicin hydrochloride, has been investigated in rats. Using the tail as a target organ, the animals were intra-arterially administered with either 0.12 mg/kg of free drug, or 0.04 mg/kg of microsphere entrapped drug in the presence of a 8000 Gauss magnet applied for 30 min at the target-site. In each group, the animals were sacrificed over a 48 h period and their various tissues analysed for drug concentration using HPLC. It was found that compared to the free drug, a one-third dose of microsphere entrapped drug resulted in almost eight times higher drug exposure (AUC0-infinity) at the target site. In addition, the drug delivery to all the non-target tissues, including liver and heart, was substantially reduced. The study confirms the efficacy of magnetic albumin microspheres in the targeted delivery of chemotherapeutic agents.

Comparative disposition of adriamycin delivered via magnetic albumin microspheres in presence and absence of magnetic field in rats

The multiple tissue disposition of adriamycin hydrochloride delivered via magnetic albumin microspheres, in absence (control) and presence of magnetic field (experimental), has been investigated in rats. The animal tail was demarcated into three segments: T1, the dosing-site; T2, the target-site; and T3, the post target-site. Following the arterial cannulation at T1, 0.4 mg/kg of microsphere associated drug was administered to the control as well as the experimental animals. In experimental group, the target-site T2 was exposed to a 8000 G magnetic field for 30 min. In both groups the animals were sacrificed in triplicates over a 48 hr period and their various tissues monitored for drug concentrations using HPLC. In presence of magnetic field, the microspheres demonstrated 16 fold increase in the maximum drug concentration, 6 fold increase in drug exposure and 6 fold increase in the drug targeting efficiency for T2. Drug delivery to most non-target tissues, including heart and liver, was substantially reduced. The results quantitatively suggest that the efficacy of magnetic albumin microspheres in the targeted delivery of incorporated therapeutic agent is predominantly due to the magnetic effects, and not alone due to the characteristics of the micro-carrier system.

Albumin microspheres. I: Physico-chemical characteristics

Albumin microspheres are biodegradable particles which can be readily radiolabelled and synthesized in the size range of 1 to 200 microns. During the last 30 years extensive efforts have been made towards the design and development of this carrier for the purpose of diagnosis and drug delivery. This review presents a thorough discussion on the physico-chemical characteristics of albumin microspheres.

Effect of carrier dose on the multiple tissue disposition of doxorubicin hydrochloride administered via magnetic albumin microspheres in rats

The effect of carrier dose on the multiple tissue disposition of doxorubicin hydrochloride has been investigated in rats. The drug was encapsulated in submicron magnetic albumin microspheres using a heat-denaturation technique. The rat tail was used as a target organ. Two groups of animals were administered 2.0 or 0.04 mg/kg of microsphere-entrapped drug via the ventral caudal artery, and the predefined tail target site was exposed to a 8000-G magnetic field for 30 min after dosing. In each group, the animals were sacrificed in triplicate over a 48-h period, and their various tissues were analyzed for drug concentration using reversed-phase ion-pair HPLC. The reduction in carrier dose was found to increase drug distribution as well as the targeting efficiency for the target tissue. The drug delivery to heart and liver was reduced. The significance of carrier dose in the targeted delivery of drugs is discussed.

Ultrastructural disposition of adriamycin-associated magnetic albumin microspheres in rats

The ultrastructural disposition of intra-arterially administered adriamycin-associated magnetic albumin microspheres has been investigated. The rat tail was used as the target organ and demarcated into the following three parts: T1, the injection site; T2, the target site; and T3, the posttarget site. Adriamycin HCl (2.0 mg/kg) was administered via the carrier through a cannula fixed at T1. The target site, T2, was exposed to a magnetic field of 8000 G for 30 min postdosing. Animals were sacrificed at scheduled time intervals over a 72-h period, and the tissue samples from T2 were observed by light and transmission electron microscopy. Electron microscopy revealed that microspheres traverse the vascular endothelium of the target tissue as early as 2 h after dosing. Gradual loss of tissue organization and cellular components, as a function of drug exposure time, demonstrated that the pharmacodynamic characteristics of the drug are not altered by its entrapment and delivery via the magnetic microspheres. The study confirms second-order drug targeting in the target tissue of healthy animals.