Liver targeting of human interferon-beta with pullulan based on metal coordination

Mediation of synergistic chemotherapy and gene therapy via nanoparticles based on chitosan and ionic polysaccharides

Nanoparticles (NPs)-based on various ionic polysaccharides, including chitosan, hyaluronic acid, and alginate have been frequently summarized for controlled release applications, however, most of the published reviews, to our knowledge, focused on the delivery of a single therapeutic agent. A comprehensive summarization of the co-delivery of multiple therapeutic agents by the ionic polysaccharides-based NPs, especially on the optimization of the polysaccharide structure for overcoming various extracellular and intracellular barriers toward maximized synergistic effects, to our knowledge, has been rarely explored so far. For this purpose, the strategies used for overcoming various extracellular and intracellular barriers in vivo were introduced first to provide guidance for the rational design of ionic polysaccharides-based NPs with desired features, including long-term circulation, enhanced cellular internalization, controllable drug/gene release, endosomal escape and improved nucleus localization. Next, four preparation strategies were summarized including three physical methods of polyelectrolyte complexation, ionic crosslinking, and self-assembly and a chemical conjugation approach. The challenges and future trends of this rapidly developing field were finally discussed in the concluding remarks. The important guidelines on the rational design of ionic polysaccharides-based NPs for maximized synergistic efficiency drawn in this review will promote the future generation and clinical translation of polysaccharides-based NPs for cancer therapy.

Pullulan in biomedical research and development - A review

Pullulan is an imperative microbial exo-polymer commercially produced by yeast like fungus Aureobasidium pullulans. Its structure contains maltosyl repeating units which comprises two α-(1 → 4) linked glucopyranose rings attached to one glucopyranose ring through α-(1 → 6) glycosidic bond. The co-existence of α-(1 → 6) and α-(1 → 4) glycosidic linkages endows distinctive physico-chemical properties to pullulan. It is highly biocompatible, non-toxic and non-carcinogenic in nature. It is extremely resistant to any mutagenicity or immunogenicity. The unique properties of pullulan make it a potent candidate for biomedical applications viz. drug delivery, gene delivery, tissue engineering, molecular chaperon, plasma expander, vaccination, etc. This review highlights the potential of pullulan in biomedical research and development.

Pullulan microbeads/Si-HPMC hydrogel injectable system for the sustained delivery of GDF-5 and TGF-β1: new insight into intervertebral disc regenerative medicine

Discogenic low back pain is considered a major health concern and no etiological treatments are today available to tackle this disease. To clinically address this issue at early stages, there is a rising interest in the stimulation of local cells by in situ injection of growth factors targeting intervertebral disc (IVD) degenerative process. Despite encouraging safety and tolerability results in clinic, growth factors efficacy may be further improved. To this end, the use of a delivery system allowing a sustained release, while protecting growth factors from degradation appears of particular interest. We propose herein the design of a new injectable biphasic system, based on the association of pullulan microbeads (PMBs) into a cellulose-based hydrogel (Si-HPMC), for the TGF-β1 and GDF-5 growth factors sustained delivery. We present for the first time the design and mechanical characterization of both the PMBs and the called biphasic system (PMBs/Si-HPMC). Their loading and release capacities were also studied and we were able to demonstrate a sustained release of both growth factors, for up to 28 days. Noteworthy, the growth factors biological activity on human cells was maintained. Altogether, these data suggest that this PMBs/Si-HPMC biphasic system may be a promising candidate for the development of an innovative bioactive delivery system for IVD regenerative medicine.

Carbohydrate-based materials for targeted delivery of drugs and genes to the liver

The insult to liver by toxic materials leads to cirrhosis, hepatitis and cancer. Upon administration, drugs accumulate in liver, which is systemically cleared by reticuloendothelial system. However, specific targeting of drugs to liver is a serious challenge. Specific delivery of molecules to hepatocytes is accomplished by targeting cell surface lectins, asialoglycoprotein receptors. Asialofetuin, N-acetyl glucosamine and galactose are high-affinity ligands of asialoglycoprotein receptors. The bioconjugation of drugs, fluorescent molecules and gene delivery vectors with lectin-targeting agents, and their delivery in liver hepatocytes, is discussed. Mannose and N-acetyl glucosamine conjugates are evaluated for their delivery to hepatic stellate and kupffer cells. The glycosylated gene and drug delivery vectors in clinical trials are outlined.

pH-sensitive pullulan-based nanoparticle carrier of methotrexate and combretastatin A4 for the combination therapy against hepatocellular carcinoma

This study designs a pH-sensitive nanoparticle carrier of methotrexate (MTX) and combretastatin A4 (CA4) based on pullulan for the combination therapy against hepatocellular carcinoma (HCC). Briefly, N-urocanyl pullulan (URPA) with the degree of substitution (DS) of 5.2% was synthesized and then conjugated with MTX to form MTX-URPA, in which MTX content was 17.8%. MTX-URPA nanoparticles prepared by the dialysis method had spherical shape and the mean size of 187.1 nm, and showed high affinity for HepG2 cells. CA4 was successfully loaded into MTX-URPA nanoparticles and exhibited pH-sensitive in vitro release property. After intravenous injection to PLC/PRF/5-bearing nude mice, CA4 loaded MTX-URPA (CA4/MTX-URPA) nanoparticles achieved the enhanced antitumor and anti-angiogenic effects, the prolonged circulation time in blood, and the increased distributions both in the liver and the tumor. In conclusion, this drug carrier system has significant liver-targeting property and exhibits advantages for the combination therapy against hepatocellular carcinoma.

Near-infrared emitting polymer nanogels for efficient sentinel lymph node mapping

Sentinel lymph node (SLN) mapping has been widely used to predict the metastatic spread of primary tumor to regional lymph nodes in clinical practice. In this research, a new near-infrared (NIR)-emitting polymer nanogel (NIR-PNG) having a hydrodynamic diameter of about 30 nm, which is optimal for lymph node uptake, was developed. The NIR-emitting polymer nanoprobes were designed and synthesized by conjugating IRDye800 organic dye to biodegradable pullulan-cholesterol polymer nanogels. The NIR-PNG nanoprobes were found to be photostable compared with the IRDye800-free dye at room temperature. Upon intradermal injection of the NIR-PNG into the front paw of a mouse, the nanoprobes entered the lymphatic system and migrated to the axillary lymph node within 2 min. The NIR fluorescence signal intensity and retention time of NIR-PNG in the lymph node were superior to the corresponding properties of the IRDye800-free dye. A immunohistofluorescence study of the SLN resected under NIR imaging revealed that the NIR-PNG nanoprobes were predominantly co-localized with macrophages and dendritic cells. Intradermal injection of NIR-PNG nanoprobes into the thigh of a pig permitted real-time imaging of the lymphatic flow toward the SLN. The position of the SLN was identified within 1 min with the help of the NIR fluorescence images. Taken together, the experimental results demonstrating the enhanced photostability and retention time of the NIR-PNG provide strong evidence for the potential utility of these polymer probes in cancer surgery such as SLN mapping.

Expression profile of plasmid DNA obtained using spermine derivatives of pullulan with different molecular weights

The objective of this study was to prepare a novel gene carrier from pullulan, a polysaccharide with an inherent affinity for the liver, and evaluate the feasibility in gene transfection. Pullulan with different molecular weights was cationized by chemical introduction of spermine. The cationized pullulan derivative was complexed with a plasmid DNA and applied to HepG2 cells for in vitro gene transfection. The level of gene expression depended on the molecular weight of cationized pullulan derivatives and the highest level was observed for the cationized pullulan derivative with a molecular weight of 47.3 x 10(3). Pre-treatment of cells with asialofetuin decreased the level of gene expression by the complexes. These findings indicate that the cationized pullulan derivative is a promising non-viral carrier of plasmid DNA which is internalized in a receptor-mediated fashion.

Effect of modification manner on the photodynamic antitumor activity of C60 modified with pullulan

To design a novel cytospecific photosensitizer for photodynamic antitumor therapy, a fullerene (C(60)) was chemically modified with pullulan, a water-soluble polysaccharide with a high affinity for asialoglycoprotein receptors (ASGPRs). The effect of the molecular weight of pullulan and the modification manner to C(60) on the photodynamic antitumor activity of C(60) modified with pullulan was evaluated. In this study, two modification manners were selected. First, ethylene diamine was chemically introduced to the hydroxyl groups of pullulan with different molecular weights. Then, C(60) was coupled to pullulan through the amino groups introduced (pendant type). Second, ethylene diamine was introduced to the terminal aldehyde groups of pullulan by a reductive amination reaction, and then the pullulan with the terminal amino groups was coupled to C(60) (terminal type). Irrespective of the pullulan molecular and the modification manner, the C(60)-pullulan conjugates exhibited a similar ability to generate superoxide anions upon light irradiation. Comparing the C(60)-pullulan conjugates of pendant and terminal types, a high lectin affinity was observed for the latter conjugates. The conjugates showed a high affinity for HepG2 cells with ASGPRs and, consequently, a strong in vitro antitumor activity on the cells. It is concluded that the manner of pullulan modification is a key factor contributing to the photodynamic antitumor activity of modified C(60).

Synthesis and Characterization of Self-Assembled Nanogels Made of Pullulan

Self-assembled nanogels made of hydrophobized pullulan were obtained using a versatile, simple, reproducible and low-cost method. In a first reaction pullulan was modified with hydroxyethyl methacrylate or vinyl methacrylate, further modified in the second step with hydrophobic 1-hexadecanethiol, resulting as an amphiphilic material, which self-assembles in water via the hydrophobic interaction among alkyl chains. Structural features, size, shape, surface charge and stability of the nanogels were studied using hydrogen nuclear magnetic resonance, fluorescence spectroscopy, cryo-field emission scanning electron microscopy and dynamic light scattering. Above the critical aggregation concentration spherical polydisperse macromolecular micelles revealed long-term colloidal stability in aqueous medium, with a nearly neutral negative surface charge and mean hydrodynamic diameter in the range 100–400 nm, depending on the polymer degree of substitution. Good size stability was observed when nanogels were exposed to potential destabilizing pH conditions. While the size stability of the nanogel made of pullulan with vinyl methacrylate and more hydrophobic chains grafted was affected by the ionic strength and urea, nanogel made of pullulan with hydroxyethyl methacrylate and fewer hydrophobic chains grafted remained stable.

Evaluation of pullulan-functionalized doxorubicin nanoparticles for asialoglycoprotein receptor-mediated uptake in Hep G2 cell line

The present study discusses evaluation of pullulan-functionalized doxorubicin nanoparticles for asialoglycoprotein receptor-mediated uptake in the Hep G2 cell line. Doxorubicin hydrochloride (DOX) nanoparticles using polymers of different hydrophobic character, polyethylene sebacate (hydrophobic) and poly (lactic-co-glycolic acid) (intermediate hydrophobicity) with high entrapment efficiency and particle size were prepared by modified nanoprecipitation, using Gantrez AN 119 as complexing agent. Nanoparticles of Gantrez AN 119 were also prepared to represent a hydrophilic polymer. Cell uptake of DOX nanoparticles was found to be comparable to DOX solution irrespective of DOX concentration, nanoparticles size, and pullulan concentration. Furthermore, uptake of nanoparticles functionalized with or without pullulan prepared with polymers of different hydrophobic character revealed comparable uptake. Comparable uptake of DOX solution and DOX nanoparticles functionalized with or without pullulan suggest extracellular release of DOX as the mechanism of uptake from the nanoparticles. In vivo evaluation in hepatic cancer model is therefore essential to confirm the role of pullulan as asialoglycoprotein receptors ligand.

An efficient esterification of pullulan using carboxylic acid anhydrides activated with iodine

Acylation of alcohols (esterification) with anhydride is an important and routinely utilized transformation in organic synthesis. Iodine is a cheap and one of the most powerful anhydride activating agents for the esterification of alcohols. Therefore, an efficient and cost effective method was developed for the acylation of pullulan polysaccharide by using different acid anhydrides activated with iodine. A series of organo-soluble pullulan esters were successfully synthesized, purified and characterized. Under solvent free conditions, it was feasible to fabricate pullulan nonaacetate and pullulan stearate. Attachment (covalent) of the pendant groups onto polymer backbone was verified by spectroscopic techniques. All of the products were characterized by using thermal analysis, FTIR and 1H NMR spectroscopy.

Interferon alpha delivery systems for the treatment of hepatitis C

Hepatitis C virus (HCV) infections are the most common chronic blood-borne viral infections in the world. The prevalence of HCV infections varies significantly by race or ethnicity, with a high prevalence of the disease displayed in the Hispanic population. Additionally, Hispanics with chronic HCV have also more advanced hepatic fibrosis and faster liver fibrosis progression rates than either African Americans or Caucasians. Furthermore, a higher prevalence of cirrhosis and extent of mortality from liver cirrhosis is also observed in the Hispanic population compared with other groups. Current recommendations for treatment of hepatitis C are interferon alpha (IFNalpha)-based monotherapy and combination of IFNalpha preparations with ribavirin. Future treatment regimens will still be based on IFNalpha therapy with or without other effective antiviral agents, currently under investigation. However, there are some inherent limitations, mainly their relative short systemic circulation lifespan, and their unwanted effects on some non-target tissues. New research focuses on the development of novel modified interferon molecules which demonstrate reduced side effects and extended systemic circulation time, which can ultimately provide greater efficacy. Alternative routes for IFNalpha delivery, such as oral delivery, demonstrate challenging but promising areas of research for improving future patient compliance.

Expression profile of plasmid DNA by spermine derivatives of pullulan with different extents of spermine introduced

The objective of this study is to prepare a novel gene carrier from pullulan, a polysaccharide with an inherent affinity for the liver, and evaluate the feasibility in gene transfection. Various amounts of spermine were chemically introduced into pullulan with molecular weights of 22,800, 47,300, and 112,000 to prepare cationized pullulan derivatives with different percentages of spermine introduced. Each cationized pullulan derivative was complexed with a plasmid DNA at various ratios and applied to HepG2 cells for in vitro gene transfection. The level of gene expression depended on the percent spermine introduced of cationized pullulan derivatives and the molecular weight of pullulan. However, when compared at the complexation molar ratio of pullulan derivative to the plasmid DNA, the expression level became maximum around the ratio of 10(2), irrespective of the pullulan molecular weight. Pre-treatment of cells with asialofetuin of asialoglycoprotein receptor ligand decreased the level of gene expression by the complexes. The cationized pullulan derivative with an appropriate physicochemical character is a promising non-viral carrier which promotes the receptor-mediated internalization of plasmid DNA and consequently enhances the expression level.

Efficient gene transfer by pullulan–spermine occurs through both clathrin- and raft/caveolae-dependent mechanisms

The feasibility and mechanism of gene delivery by pullulan-spermine, a recently developed cationic polysaccharide, were investigated. Pullulan-spermine-mediated transfection of plasmid DNA resulted in greatly reduced cytotoxicity and a 10-fold increase in the level of gene expression when compared to Lipofectamine 2000, a commercially available cationic lipid. Additionally, after transfection of p53-expressing plasmid DNA by pullulan-spermine but not Lipofectamine 2000, the in vitro proliferation of T24 cells was significantly reduced. Pullulan-spermine-mediated gene expression was inhibited by both chlorpromazine of clathrin-mediated endocytosis inhibitor and methyl-beta-cyclodextrin and filipin of raft/caveolae inhibitors. We conclude that pullulan-spermine is a promising carrier for gene transfection, and that cellular uptake of pullulan-spermine-plasmid DNA complexes is mediated by clathrin- and raft/caveolae-dependent endocytotic pathways.

Novel delivery methods for treatment of viral hepatitis: an update

Viral hepatitis represents the most common cause of chronic liver disease worldwide. Currently approved therapies for chronic hepatitis B include IFN, an immune modulator, and nucleoside analogues lamivudine and adefovir. For chronic hepatitis C, a combination of pegylated IFN-alpha and ribavirin represents the standard treatment. However, currently available treatments for both these viruses are effective only in a limited number of patients, are costly, prolonged, associated with significant side effects and require a substantial commitment from the patients and healthcare providers. A number of novel antiviral treatments, together with strategies to enhance the response to current therapies, are being explored at present. For all new therapies, as well as for improving existing treatments, selective delivery of medications into liver cells would be desirable to enhance antiviral activity and avoid systemic side effects. New achievements in the field of drug and gene delivery against chronic hepatitis to the liver are reviewed here.

Strategies for targeting protein therapeutics to selected tissues and cells

The advent of recombinant biotechnology and the recent sequencing of the human genome now allow for identification of scores of potential protein therapeutics along with the capacity to produce them in quantities and purities required for clinical application. Thus, clinical development of potential protein therapeutics has become as commonplace as development efforts of classical small molecule therapeutics. Whereas small molecule therapeutic lead candidates are identified through screens of large sets of possibilities, therapeutic protein candidates are defined by genetic information as a single composition (or a limited set of isoforms). Small molecule leads are identified through the combined assessment of desired selectivity, biodistribution and pharmacokinetic properties. In essence, these selection parameters emulate the actions of protein therapeutics that function as systemic hormones through their ability to target selective cells and tissues of the body via selective receptor interaction with minimal actions elsewhere. However, many, if not most, potential protein therapeutics do not normally circulate through the body to reach their target cell or tissue; rather, they are frequently synthesised at local sites, act at that site and are degraded without reaching appreciable systemic levels. Dose-limiting adverse events are associated with systemic administration of many of these proteins, restricting their clinical potential. This review examines current strategies to reduce these dose-limiting events by possibly focusing the delivery of potential protein therapeutics to discrete tissues and cells.

Uptake of Pullulan in Cultured Rat Liver Parenchymal Cells

Uptake of pullulan, including a binding process followed by internalization, was examined in cultured rat liver parenchymal cells. A tyramine derivative of pullulan was labeled with [125I]iodine and used as a ligand. Pullulan bound to the cell surface was released by EDTA treatment, indicating that pullulan binding requires Ca2+ and a contribution from the asialoglycoprotein receptor. Binding of pullulan reached a steady state and internalization represented a biphasic mode, which included first- and zero-order processes in the initial stage and after 20 min incubation, respectively. The uptake of pullulan could be estimated by a similar model for intracellular disposition of asialofetuin. Kinetic parameters of pullulan constituting both binding and internalization were below those found for asialofetuin. These results suggest that pullulan is taken up by liver parenchymal cells via the asialoglycoprotein receptor; however, uptake availability is lower than that of asialofetuin.

Intracellular disposition of polysaccharides in rat liver parenchymal and nonparenchymal cells

Binding and internalization of arabinogalactan, pullulan, dextran, and mannan were examined in rat liver parenchymal and nonparenchymal cells using 125I or fluorescein isothiocyanate (FITC) labeled polysaccharides. Binding and uptake of arabinogalactan and pullulan into parenchymal cells was inhibited by asialofetuin, indicating that the asialoglycoprotein receptor is involved in the intracellular disposition of arabinogalactan and pullulan. Uptake of 125I-labeled dextran to parenchymal cells was unchanged upon addition of excess unlabeled dextran, suggesting that dextran uptake occurs via fluid phase endocytosis. Of the polysaccharides tested, mannan showed the strongest specific association with liver nonparenchymal cells. FITC-labeled polysaccharides showed arabinogalactan and pullulan are internalized to liver parenchymal cells, whereas mannan is internalized to nonparenchymal cells. This study demonstrates that intracellular disposition of polysaccharides in the liver occurs via receptor-mediated endocytosis (RME), indicating that RME plays a role in the biodisposition of these polysaccharides as drug carriers.