Use of polysaccharides as drug carriers. Dextran and inulin derivatives of procainamide

Influence of Oxidation Degree on the Physicochemical Properties of Oxidized Inulin

This paper reports the oxidation of inulin using varying ratios of sodium periodate and the characterization of the inulin polyaldehyde. The physicochemical properties of the inulin polyaldehyde (oxidized inulin) were characterized using different techniques including 1D NMR spectroscopy, ¹³C Nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), differential scanning calorimetric (DSC), ultraviolet-visible spectroscopy (UV), and scanning electron microscopy (SEM). The aldehyde peak was not very visible in the FTIR, because the aldehyde functional group exists in a masked form (hemiacetal). The thermal stability of the oxidized inulin decreased with the increasing oxidation degree. The smooth spherical shape of raw inulin was destructed due to the oxidation, as confirmed by the SEM result. The ¹HNMR results show some new peaks from 4.8 to 5.0 as well as around 5.63 ppm. However, no aldehyde peak was found around 9.7 ppm. This can be attributed to the hemiacetal. The reaction of oxidized inulin with tert-butyl carbazate produced a carbazone conjugate. There was clear evidence of decreased peak intensity for the proton belonging to the hemiacetal group. This clearly shows that not all of the hemiacetal group can be reverted by carbazate. In conclusion, this work provides vital information as regards changes in the physicochemical properties of the oxidized inulin, which has direct implications when considering the further utilization of this biomaterial.

[Nanoparticle Formation and Delivery of Poorly Water-soluble Drugs by Hydrophobized Polymers]

When a hydrophobic group is introduced into a water-soluble polymer, self-assembly with the hydrophobic group as nucleus occurs in water. In the 1990s, many researchers focused on this phenomenon and various self-aggregates were prepared. Among them, a block copolymer consisting of a hydrophilic chain and a hydrophobic chain is associated in water, producing polymer micelles with the hydrophilic chain oriented in the outer shell and the hydrophobic chain as core. Meanwhile, many studies were conducted to create polymer self-associates by introducing hydrophobic groups into water-soluble polymers. In this review, the author describes hydrophobized polymers with polysaccharides and synthetic polymers that are frequently used as pharmaceutical raw materials. In addition are outlined the usefulness of hydrophobized polymers as carriers with the function of encapsulating and solubilizing poorly water-soluble drugs, along with the results of our research.

Synthesis and Characterization of pH-Sensitive Inulin Conjugate of Isoniazid for Monocyte-Targeted Delivery

The use of particles for monocyte-mediated delivery could be a more efficient strategy and approach to achieve intracellular targeting and delivery of antitubercular drugs to host macrophages. In this study, the potential of inulin microparticles to serve as a drug vehicle in the treatment of chronic tuberculosis using a monocytes-mediated drug targeting approach was evaluated. Isoniazid (INH) was conjugated to inulin via hydrazone linkage in order to obtain a pH-sensitive inulin-INH conjugate. The conjugate was then characterized using proton nuclear magnetic resonance (¹HNMR), Fourier transform infrared spectroscopy (FTIR) as well as in vitro, cellular uptake and intracellular Mycobacterium tuberculosis (Mtb) antibacterial efficacy. The acid-labile hydrazone linkage conferred pH sensitivity to the inulin-INH conjugate with ~95, 77 and 65% of the drug released after 5 h at pH 4.5, 5.2, and 6.0 respectively. Cellular uptake studies confirm that RAW 264.7 monocytic cells efficiently internalized the inulin conjugates into endocytic compartments through endocytosis. The intracellular efficacy studies demonstrate that the inulin conjugates possess a dose-dependent targeting effect against Mtb-infected monocytes. This was through efficient internalization and cleavage of the hydrazone bond by the acidic environment of the lysosome, which subsequently released the isoniazid intracellularly to the Mtb reservoir. These results clearly suggest that inulin conjugates can serve as a pH-sensitive intracellular drug delivery system for TB treatment.

Preparation and Characterization of Oxidized Inulin Hydrogel for Controlled Drug Delivery

Inulin-based hydrogels are useful carriers for the delivery of drugs in the colon-targeted system and in other biomedical applications. In this project, inulin hydrogels were fabricated by crosslinking oxidized inulin with adipic acid dihydrazide (AAD) without the use of a catalyst or initiator. The physicochemical properties of the obtained hydrogels were further characterized using different techniques, such as swelling experiments, in vitro drug release, degradation, and biocompatibility tests. The crosslinking was confirmed with Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). In vitro releases of 5-fluorouracil (5FU) from the various inulin hydrogels was enhanced in acidic conditions (pH 5) compared with physiological pH (pH 7.4). In addition, blank gels did not show any appreciable cytotoxicity, whereas 5FU-loaded hydrogels demonstrated efficacy against HCT116 colon cancer cells, which further confirms the potential use of these delivery platforms for direct targeting of 5-FU to the colon.

Design and Characterization of Inulin Conjugate for Improved Intracellular and Targeted Delivery of Pyrazinoic Acid to Monocytes

The propensity of monocytes to migrate into sites of mycobacterium tuberculosis (TB) infection and then become infected themselves makes them potential targets for delivery of drugs intracellularly to the tubercle bacilli reservoir. Conventional TB drugs are less effective because of poor intracellular delivery to this bacterial sanctuary. This study highlights the potential of using semicrystalline delta inulin particles that are readily internalised by monocytes for a monocyte-based drug delivery system. Pyrazinoic acid was successfully attached covalently to the delta inulin particles via a labile linker. The formation of new conjugate and amide bond was confirmed using zeta potential, Proton Nuclear Magnetic Resonance (1HNMR) and Fourier transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) confirmed that no significant change in size after conjugation which is an important parameter for monocyte targeting. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to establish the change in thermal properties. The analysis of in-vitro release demonstrated pH-triggered drug cleavage off the delta inulin particles that followed a first-order kinetic process. The efficient targeting ability of the conjugate for RAW 264.7 monocytic cells was supported by cellular uptake studies. Overall, our finding confirmed that semicrystalline delta inulin particles (MPI) can be modified covalently with drugs and such conjugates allow intracellular drug delivery and uptake into monocytes, making this system potentially useful for the treatment of TB.

Physical and Biological Properties of Water Soluble Polyelectrolyte Complexes

Water soluble non-stoichiometric polyelectrolyte complexes have been investigated as potential drug carrier systems for parenteral administra tion. Complexes between the polycationic quaternized poly(vinyl imidazole) (QPVI) and an excess of a higher molecular weight partially sulfonated dextran (pDS) were designed to inherit the biocompatible properties of dextran. Polyelectrolyte complexes with an overall anionic nature prepared from excess poly(methacrylic acid) (PMAA) and low molecular weight quaternary poly amines were also studied. Sedimentation velocity techniques and size exclu sion chromatography showed that complexation was present in all of the systems studied under the appropriate conditions. These studies also indicated that an increasing [polycation]/[polyanion] ratio resulted in a smaller, more compact complex conformation. Platelet aggregation studies showed that toxic aggregatory effects normally induced by the polycations, and to a lesser extent the pDS, were eliminated in vitro when they formed part of a soluble polyelec trolyte complex. In vivo distribution studies in mice using 125I-labelled polyca tion complexed with pDS or PMAA showed accumulation of 40-50% of the ad ministered dose in the liver after 2 hours. The polycation present in these com plexes appears to have been prevented, to some extent, from interacting with negatively-charged biological surfaces, such as platelets in vitro. However this complexation was not sufficient, at least for the macromolecules we have ex amined, to prevent the extensive incidence of unwanted interactions in vivo, lead ing to removal of the polyelectrolyte complexes from the circulation. In conclusion it has been shown that the ionic bonds which hold this type of complex to gether, are not sufliciently strong in vivo to preserve a stable complex structure.

Dextrans for targeted and sustained delivery of therapeutic and imaging agents

Dextrans are glucose polymers which have been used for more than 50 years as plasma volume expanders. Recently, however, dextrans have been investigated for delivery of drugs, proteins/enzymes, and imaging agents. These highly water soluble polymers are available commercially as different molecular weights (M(W)) with a relatively narrow M(W) distribution. Additionally, dextrans contain a large number of hydroxyl groups which can be easily conjugated to drugs and proteins by either direct attachment or through a linker. In terms of pharmacokinetics, the intact polymer is not absorbed to a significant degree after oral administration. Therefore, most of the applications of dextrans as macromolecular carriers are through injectable routes. However, a few studies have reported the potential of dextrans for site (colon)-specific delivery of drugs via the oral route. After the systemic administration, the pharmacokinetics of the conjugates of dextran with therapeutic/imaging agents are significantly affected by the kinetics of the dextran carrier. Animal and human studies have shown that both the distribution and elimination of dextrans are dependent on the M(W) and charge of these polymers. Pharmacodynamically, conjugation with dextrans has resulted in prolongation of the effect, alteration of toxicity profile, and a reduction in the immunogenicity of drugs and/or proteins. A substantial number of studies on dextran conjugates of therapeutic/imaging agents have reported favorable alteration of pharmacokinetics and pharmacodynamics of these agents. However, most of these studies have been carried out in animals, with only a few being extended to humans. Future studies should concentrate on barriers for the clinical use of dextrans as macromolecular carriers for delivery of drugs, proteins, and imaging agents.

Development of an immunoassay for larch arabinogalactan and its use in the detection of larch arabinogalactan in rat blood

We describe a sensitive and convenient immunoassay for larch arabinogalactan and demonstrate its specificity for larch arabinogalactan. Anti-larch arabinogalactan antiserum is about 10(4) and 10(6) times more selective for detecting larch arabinogalactan than antiserum binds to branch terminal disaccharides consisting of the terminal beta-D-galactosyl residue and the penultimate branch (1-->6)-beta-D-galactosyl residue. It does not bind L-arabinose. The sensitivity of the assay for larch arabinogalactan is less than 0.1 microgram/mL. The application of the assay for measuring arabinogalactan pharmacokinetics in rat blood is illustrated.

Dose dependency of the kinetics of dextrans in rats: effects of molecular weight

The effects of dose on the serum and tissue kinetics of high and low molecular weight (M(r)) dextrans were studied in rats. Single intravenous (iv) doses of 1, 25, or 100 mg of fluorescein-labeled dextrans with average M(r) of approximately 4 kD (FD-4) or 150 kD (FD-150) per kilogram of body weight were administered to rats, and serum, urine, and various tissues were collected over time. The samples were analyzed by a sensitive and specific chromatographic method. For FD-150, the area under the serum concentration-time curves (AUCs) increased disproportionately when the dose was increased from 1 to 100 mg/kg; the dose-corrected AUCs were 50.1 +/- 1.9, 85.9 +/- 2.4, and 122 +/- 3 micrograms.h/mL for the doses of 1, 25, and 100 mg/kg, respectively (p < 0.05). This increase in the dose-corrected AUCs was associated with a high and nonlinear accumulation of FD-150 in the liver; that is, the percent dose recovered in the liver decreased from 68.5 +/- 2.4% to 41.5 +/- 3.4% when the dose was increased from 1 to 100 mg/kg (p < 0.05). On the other hand, the serum kinetics of FD-4 exhibited dose independence [the dose-corrected AUCs were 2.38 +/- 0.04, 2.19 +/- 0.07, and 2.30 +/- 0.07 microgram.h/mL for the doses of 1, 25, and 100 mg/kg, respectively (p > 0.05)]. This dose independence was attributed to a high and linear excretion of FD-4 into urine as indicated by the percent doses of FD-4 excreted into urine [i.e., 82.0 +/- 1.8, 78.7 +/- 4.4, and 82.2 +/- 7.2 for the doses of 1, 25, and 100 mg/kg, respectively (p > 0.05)].(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of body distribution of poly(vinyl alcohol) with other water-soluble polymers after intravenous administration

The body distribution of poly(vinyl alcohol) (PVA) with molecular weights (MW) from 14,800 to 434,000 Da was investigated after intravenous administration and compared with that of other water-soluble polymers such as poly(ethylene glycol) (PEG), gelatin, dextran, and pullulan. The half-life of PVA in the circulation was prolonged from 90 min (MW 14,800 Da) to 23 h (MW 434,000 Da), similar to that of PEG which had a half-life of 30 min (MW 6000) and 20 h (MW 170,000). However, the half-life of PVA was much longer than that of other polymers when compared at a similar molecular weight. PVA was located in most organs but with very small accumulation. An insignificant interaction of PVA with cell components, such as macrophages and blood cells, was observed. Similar to PEG, the excretion rate of PVA at the glomeruli was rapidly reduced around 30,000 Da, as the molecular weight increased. These results indicate that the half-life of intravenously injected PVA in the blood was mainly determined by the permeation characteristics of the kidney.