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ABSTRACT: Protein instability and immunogenicity are two main roadblocks to the clinical success of novel protein drug delivery systems. In this commentary, we discuss the need for more extensive analytical characterization in relation to concerns about protein instability in injectable drug delivery systems for sustained release. We then will briefly address immunogenicity concerns and outline current best practices for using state-of-the-art analytical assays to monitor protein stability for both conventional and novel therapeutic protein dosage forms. Next, we provide a summary of the stresses on proteins arising during preparation of drug delivery systems and subsequent in vivo release. We note the challenges and difficulties in achieving the absolute requirement of quantitatively assessing the degradation of protein molecules in a drug delivery system. We describe the potential roles for academic research in further improving protein stability and developing new analytical technologies to detect protein degradation byproducts in novel drug delivery systems. Finally, we provide recommendations for the appropriate approaches to formulation design and assay development to ensure that stable, minimally immunogenic formulations of therapeutic proteins are created. These approaches should help to increase the probability that novel drug delivery systems for sustained protein release will become more readily available as effective therapeutic agents to treat and benefit patients.
Journal of Pharmaceutical Sciences 12/2011; 101(3):946-54. · 3.06 Impact Factor
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ABSTRACT: To investigate the in vitro release of octreotide acetate, a somatostatin agonist, from microspheres based on a hydrophilic polyester, poly(D,L-lactide-co-hydroxymethyl glycolide) (PLHMGA).
Spherical and non-porous octreotide-loaded PLHMGA microspheres (12 to 16 μm) and loading efficiency of 60-70% were prepared by a solvent evaporation. Octreotide release profiles were compared with commercial PLGA formulation (Sandostatin LAR(®)); possible peptide modification with lactic, glycolic and hydroxymethyl glycolic acid units was monitored.
PLHMGA microspheres showed burst release (~20%) followed by sustained release for 20-60 days, depending on the hydrophilicity of the polymer. Percentage of released loaded peptide was high (70-90%); > 60% of released peptide was native octreotide. PLGA microspheres did not show peptide release for the first 10 days, after which it was released in a sustained manner over the next 90 days; > 75% of released peptides were acylated adducts.
PLHMGA microspheres are promising controlled systems for peptides with excellent control over release kinetics. Moreover, substantially less peptide modification occurred in PLHMGA than in PLGA microspheres.
Pharmaceutical Research 07/2011; 29(1):110-20. · 4.09 Impact Factor
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ABSTRACT: Liposomes are versatile (sub)micron-sized membrane vesicles that can be used for a variety of applications, including drug delivery and in vivo imaging but they also represent excellent models for artificial membranes or cells. Several studies have demonstrated that in vitro transcription and translation can take place inside liposomes to obtain compartmentalized production of functional proteins within the liposomes (Kita et al. in Chembiochem 9(15):2403-2410, 2008; Moritani et al.in FEBS J, 2010; Kuruma et al. in Methods Mol Biol 607:161-171, 2010; Murtas et al. in Biochem Biophys Res Commun 363(1):12-17, 2007; Sunami et al. in Anal Biochem 357(1):128-136, 2006; Ishikawa et al. in FEBS Lett 576(3):387-390, 2004; Oberholzer et al. in Biochem Biophys Res Commun 261(2):238-241, 1999). Such a minimal artificial cell-based model is ideal for synthetic biology based applications. In this study, we propose the use of liposomes as artificial microbes for vaccination. These artificial microbes can be genetically programmed to produce specific antigens at will. To show proof-of-concept for this artificial cell-based platform, a bacterial in vitro transcription and translation system together with a gene construct encoding the model antigen β-galactosidase were entrapped inside multilamellar liposomes. Vaccination studies in mice showed that such antigen-expressing immunostimulatory liposomes (AnExILs) elicited higher specific humoral immune responses against the produced antigen (β-galactosidase) than control vaccines (i.e. AnExILs without genetic input, liposomal β-galactosidase or pDNA encoding β-galactosidase). In conclusion, AnExILs present a new platform for DNA-based vaccines which combines antigen production, adjuvanticity and delivery in one system and which offer several advantages over existing vaccine formulations.
Systems and Synthetic Biology 06/2011; 5(1-2):21-31.
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ABSTRACT: Screening of new gene delivery candidates regarding transfection efficiency and toxicity is usually performed by reading out transgene expression levels relative to a reference formulation after in vitro transfection. However, over the years and among different laboratories, this screening has been performed in a variety of cell lines, using a variety of conditions and read-out systems, and by comparison to a variety of reference formulations. This makes a direct comparison of results difficult, if not impossible. Reaching a consensus would enable placing new results into context of previous findings and estimate the overall contribution to the improvement of non-viral gene delivery. In this paper we illustrate the sensitivity of transfection outcomes on testing conditions chosen, and propose a screening protocol with the aim of standardization within the field.
Journal of Controlled Release 05/2011; 154(3):218-32. · 5.73 Impact Factor
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ABSTRACT: To evaluate if introduction of DNA nuclear Targeting Sequences (DTS; i.e. recognition sequences for endogenous DNA-binding proteins) in plasmid DNA (pDNA) leads to increased transfection efficiency of non-viral gene delivery by virtue of enhanced nuclear import of the pDNA.
A set of DTS was identified and cloned into EGFP-reporter plasmids controlled by the CMV-promoter. These pDNA constructs were delivered into A431 and HeLa cells using standard electroporation, pEI-based polyfection or lipofection methods. The amount of pDNA delivered into the nucleus was determined by qPCR; transfection efficiency was determined by flow cytometry.
Neither of these DTS increased transgene expression. We varied several parameters (mitotic activity, applied dose and delivery strategy), but without effect. Although upregulated transgene expression was observed after stimulation with TNF-α, this effect could be ascribed to non-specific upregulation of transcription rather than enhanced nuclear import. Nuclear copy numbers of plasmids containing or lacking a DTS did not differ significantly after lipofectamine-based transfection in dividing and non-dividing cells.
No beneficial effects of DTS on gene expression or nuclear uptake were observed in this study.
Pharmaceutical Research 03/2011; 28(7):1707-22. · 4.09 Impact Factor
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ABSTRACT: In this Commentary, the authors briefly discuss the status of efforts to individualize therapeutic interventions. They differentiate between the widely discussed idea of further shaping 'personalized medicine' approaches by using (new) biomarkers and (molecular) imaging techniques and the much less debated topic of 'personalized medicines': medicines, often carrier based, specifically geared to treat the individual patient optimally. An example where 'personalized medicine' is achieved by 'personalized medicines' is described: a smart drug delivery system is activated at the target site by non-invasive radiation (focused ultrasonic radiation, FU) while this spatial and temporal release process is guided and monitored by MRI (Magnetic Resonance Imaging guided High Intensity Focused Ultrasonic, MRIgHIFU).
International journal of pharmaceutics 02/2011; 415(1-2):5-8. · 2.96 Impact Factor
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ABSTRACT: Previously we have shown that the recombinantly produced SA2 amphiphilic oligopeptide (Ac-Ala-Ala-Val-Val-Leu-Leu-Leu-Trp-Glu-Glu-COOH) self-assembles into nanovesicles (van Hell et al. 2007). In this study, the intermolecular interactions that contribute to the formation of such peptide vesicles are examined. First, analysis of a 3-hydroxyflavone fluorescent probe inserted into the peptide assemblies demonstrated that the peptide self-assembly is based on hydrophobic clustering. The polarity of this hydrophobic microenvironment was comparable to that of negatively charged lipid bilayers. A substantial level of hydration at the hydrophilic-hydrophobic interface was detected, as was further confirmed by tryptophan fluorescence analysis. However, organic solvents such as acetonitrile, tetrahydrofuran, or ethanol could not disrupt SA2 oligopeptide vesicles, whereas these solvents fully disintegrated lipid vesicles. Instead, the SA2 assembly immediately disintegrated in hydrogen breaking solvents such dimethylsulfoxide and dimethylformamide, suggesting the involvement of additional intermolecular interactions via hydrogen bonding. Circular dichroism and Fourier transform infrared spectroscopy excluded well-defined patterns of intramolecular hydrogen bonding and indicated the polyproline type II as the dominant SA2 peptide conformation, which enables intermolecular hydrogen bonding. All-atom computational simulations were used to confirm the presence of such intermolecular hydrogen bonds and degrees of hydration. On the basis of the experimental and computational data presented, we propose a model of an interdigitated peptide assembly that involves intermolecular hydrogen bonding in addition to hydrophobic interactions that stabilize SA2 oligopeptide vesicles.
The Journal of Physical Chemistry B 09/2010; 114(34):11046-52. · 3.70 Impact Factor
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ABSTRACT: To study the release of a model protein, bovine serum albumin (BSA), from microspheres of an hydroxylated aliphatic polyester, poly(lactic-co-hydroxymethyl glycolic acid) (PLHMGA).
BSA-loaded microspheres were prepared by a double emulsion solvent evaporation method. The effect of copolymer composition and the molecular weight of the copolymer on in vitro release and degradation were studied. The integrity of the released BSA was studied by fluorescence spectroscopy and size exclusion chromatography (SEC).
Microspheres prepared from PLHMGA with 50% hydroxymethyl glycolic acid (HMG) showed a burst release followed by a sustained release in 5-10 days. PLHMGA microspheres prepared from a copolymer with 35% and 25% HMG showed a sustained release of BSA up to 80% for 30 and 60 days, respectively. The release of BSA was hardly affected by the molecular weight of the polymer. Fluorescence spectroscopy and SEC showed that the released BSA preserved its structural integrity. Microspheres were fully degradable, and the degradation time increased from approximately 20 days to 60 days when the HMG content decreased from 50% to 25%.
Taking the degradation and release data together, it can be concluded that the release of BSA from PLHMGA microspheres is governed by degradation of the microspheres.
Pharmaceutical Research 09/2010; 27(9):2008-17. · 4.09 Impact Factor
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ABSTRACT: Synthetic biology aims at reprogramming existing, or creating new, biological systems, with the ultimate aim to obtain artificial cells whose functions can be tailored. For the latter, encapsulation of complex biochemical reactions into cell-sized compartments, such as liposomes, is required. Recently, several groups have demonstrated that proteins of interest can be produced de novo within liposomes by entrapping cell-free protein-synthesis systems and DNA templates inside liposomes. Although detectable, intraliposomal protein synthesis was generally poor. Here, we have optimized intraliposomal cell-free protein synthesis by changing several variables, including lipid composition as well as liposome, pyrophosphatase, and T7 RNA polymerase concentration. Further, by using an activity-based assay, we have quantified the amount of full-length protein that was produced from DNA templates inside liposomes before and after optimization of aforementioned variables. Based on the model protein beta-galactosidase, it is demonstrated that liposomal protein synthesis can yield microgram quantities of protein (30-40 microg/mL liposomes).
Journal of Liposome Research 11/2009; 20(1):73-83. · 1.71 Impact Factor
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Journal of Pharmaceutical Sciences 11/2009; 99(5):2200-8. · 3.06 Impact Factor
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ABSTRACT: Previously, we have shown that the amphiphilic oligopeptide SA2 (Ac-Ala-Ala-Val-Val-Leu-Leu-Leu-Trp-Glu-Glu-COOH) spontaneously self-assemble into nano-sized vesicles in aqueous environment. Relative weak individual intermolecular interactions dominate such oligopeptide assemblies. In this study we aimed at improving the stability of such peptide vesicles by covalently crosslinking the oligopeptide vesicles using disulfide bonds. Two and three cysteines were introduced in the SA2 peptide sequence to allow crosslinking (Ac-Ala-Cys-Val-Cys-Leu-(Leu/Cys)-Leu-Trp-Glu-Glu-COOH).
Upon disulfide formation the crosslinked vesicles remained stable under conditions that disrupted the non-crosslinked peptide vesicles. The stabilized vesicles were more closely examined in terms of particle size (distribution) using atomic force microscopy, cryogenic electron microscopy, as well as dynamic light scattering analysis, showing an average particle radius in number between 15 and 20 nm. Using entrapment of calcein it was shown that intermolecular crosslinking of peptides within the vesicles did not affect the permeability for calcein.
Introduction of cysteines into the hydrophobic domain of the SA2 amphiphilic oligopeptides is a feasible strategy for crosslinking the peptide vesicles. Such small crosslinked oligopeptide vesicles may hold promise for drug delivery applications.
Pharmaceutical Research 10/2009; 26(9):2186-93. · 4.09 Impact Factor
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ABSTRACT: Gene therapy aims at delivering exogenous DNA into the nuclei of target cells to establish expression of a therapeutic protein. Non-viral gene delivery is examined as a safer alternative to viral approaches, but is presently characterized by a low efficiency. In the past years several non-viral delivery strategies have been developed, including cationic polymer-based delivery. One of the most described and most active polymers is linear pEI. This study addresses questions regarding formulating highly efficient pEI-based polyplexes. By mixing reporter plasmid DNA with non-coding junk DNA it was shown that the amount of reporter plasmid can be significantly decreased in linear pEI-based transfection while maintaining transfer activity. Junk DNA maximally exerts its function when co-delivered with active DNA within the same pEI complexes rather than upon co-delivery of distinct junk DNA/pEI and active DNA/pEI complexes. We conclude that not the total amount of active DNA, but rather the total amount of active DNA-containing particles is the limiting factor in pEI-mediated transfection.
International journal of pharmaceutics 09/2009; 390(1):76-83. · 2.96 Impact Factor
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ABSTRACT: Previously we have shown that recombinantly produced amphiphilic oligopeptides with amino acid sequence Ac-Ala-Ala-Val-Val-Leu-Leu-Leu-Trp-Glu-Glu spontaneously assemble into nano-sized vesicles with an average diameter of 120 nm. Moreover, peptide vesicles could be stabilized by introducing multiple cysteine residues within the hydrophobic domain of these amphiphilic oligopeptides, allowing the formation of intermolecular disulfide bridges. In this study, the cellular association and internalization of peptide vesicles were assessed. Flow cytometry and confocal laser-scanning microscopy showed that peptide vesicles were internalized by cells predominantly via adsorptive macropinocytosis. Furthermore, the potential of these peptide vesicles as delivery system for photosensitizers was explored. Water-insoluble phthalocyanines could be quantitatively entrapped within the hydrophobic domains of these peptide vesicles. Confocal laser-scanning microscopy analysis showed that internalized peptides co-localized with the phthalocyanine, suggesting that peptide vesicles are internalized in their intact form. Upon illumination, the phthalocyanine-containing peptide vesicles showed an active photodynamic response towards the cells leading to effective cell killing. In contrast, the free phthalocyanine or empty peptide vesicles did not show any cytotoxicity. In conclusion, this is the first demonstration that peptide vesicles show promise as delivery systems for photosensitizers to be used in photodynamic therapy.
Journal of Controlled Release 09/2009; 141(3):347-53. · 5.73 Impact Factor
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ABSTRACT: Abstract Liposomes can be used for several different reasons in therapy. In this brief review the sources of chemical and physical instability of liposomes and the approaches for long term stabilization will be discussed.
10/2008; 20(4):547-556.
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ABSTRACT: Abstract The interaction between myoglobin and negatively-charged liposomes composed of phosphatidylcholine/phosphatidylglycerol (1:1) was studied at low ionic strength under acidic conditions. Changes in the absorbance and the fluorescence spectra of myoglobin were recorded upon addition of liposomes to partially unfolded (pH 3.5) and native (pH 4.5 and pH 6.5) myoglobin. Association of myoglobin with liposomes was a relatively fast process at pH 3.5 and pH 4.5. Although at pH 3.5 myoglobin was unfolded partially before the addition of the liposomes while at pH 4.5 before the addition of liposomes myoglobin retained its native form, similar interaction patterns of myoglobin with liposomes were observed. The fluorescence and absorption spectra in the Soret region of myoglobin clearly indicated that at these pH values myoglobin was associated with the liposomes in a (partially) unfolded state. At pH 6.5 the kinetics of myoglobin association with liposomes was much slower than at pH 3.5 and 4.5. The spectroscopic measurements also indicated that the interaction of myoglobin with liposomes at pH 6.5 followed a different pattern and resulted in different protein structures in comparison with pH 3.5/4.5.
09/2008; 5(2):311-326.
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John F Carpenter,
Theodore W Randolph,
Wim Jiskoot, Daan J A Crommelin,
C Russell Middaugh,
Gerhard Winter,
Ying-Xin Fan,
Susan Kirshner,
Daniela Verthelyi,
Steven Kozlowski,
Kathleen A Clouse,
Patrick G Swann,
Amy Rosenberg,
Barry Cherney
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ABSTRACT: Therapeutic protein products provide unique and effective treatments for numerous human diseases and medical conditions. In many cases, these treatments are used chronically to slow disease progression, reduce morbidity and/or to replace essential proteins that are not produced endogenously in patients. Therefore, any factor that reduces or eliminates the effectiveness of the treatment can lead to patient suffering and even death. One means by which efficacy of therapeutic proteins can be compromised is by an immune response, resulting in antibody-mediated neutralization of the protein’s activity or alterations in bioavailability. For example, in the case of treatment of hemophilia A, neutralizing antibodies to Factor VIII can cause life-threatening bleeding episodes, resulting in significant morbidity and necessitating treatment with a prolonged course of a tolerance-inducing therapy to reverse immunity.In other cases, drug-induced antibodies to a therapeutic version of an endogenous protein can cross-react with and neutralize the patient’s endogenous protein. If the endogenous protein serves a nonredundant biological function, such an immune response can have devastating results. For example, pure red cell aplasia can result from neutralizing antibodies to epoetin alpha.
Journal of Pharmaceutical Sciences 09/2008; 98(4):1201-5. · 3.06 Impact Factor
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ABSTRACT: The potential of N-trimethyl chitosan (TMC) with two degrees of quaternization (DQ), TMC20 (DQ 20%, as a mucoadhesive) and TMC60 (DQ 60%, as a mucoadhesive and a permeation enhancer), and dextran (as a non-mucoadhesive and non-permeation enhancer) microparticles as carriers for pulmonary delivery of insulin was studied in diabetic rats. The impact of the powder formulation on insulin bioavailability and its pharmacological effect was evaluated using a population pharmacokinetic-pharmacodynamic (PKPD) model. Insulin-loaded microparticles were prepared by a supercritical fluid (SCF) drying technique. They had a median volume diameter and median volume aerodynamic diameter of about 6-10 microm and 4 microm, respectively. The PK of insulin in the diabetic rats was analyzed by a one-compartment disposition model and the PD was described by the minimal model of glucose disappearance. The bioavailability of the pulmonarily administered dextran-, TMC20- and TMC60-insulin microparticles relative to subcutaneously (SC) administered insulin, was 0.48, 0.59 and 0.95, respectively. Histological examinations of the rats' lungs did not show any local adverse reactions after single administration of insulin powders. The pharmacodynamic model could describe the insulin-glucose relationship and pharmacodynamic efficiency of insulin formulations, which was about 0.6(*)10(-5) ml/microU, irrespective of the formulations. The current findings suggest that TMC microparticles are a promising vehicle for pulmonary delivery of insulin.
Journal of Controlled Release 06/2008; 127(3):257-66. · 5.73 Impact Factor
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ABSTRACT: In the perspective of production of dry therapeutic protein formulations, spray drying of lysozyme (as a model protein) into super-critical carbon dioxide was studied. The effects of the nozzle (i.e., co-current coaxial converging and converging–diverging, and T-mixer impinging) and process conditions (i.e., flow rates, pressure) on the drying of the lysozyme prepared in aqueous solution dried with super-critical carbon dioxide enriched with ethanol were investigated. The particle size distribution, width of particle size distribution and mor-phology were used to determine the effect of the various parameters assessed. Particles with a median size of $1.5, $5 or $25 lm were produced depending of the nozzle selected. A basic comparative study of the nozzle was done by computational fluid dynamics, but the differences in particle size could not be depicted by these computations. The proportional increase of the flow rates (up to fivefold) caused a decrease in particle size (7-to 12-fold), and doubling the pressure caused a moderate decrease of the size (5–20%). The individual effect of the supercritical carbon dioxide, ethanol and solution streams was explained with a mass transfer model. Changing the ratio between flow rates slightly affected the particle size in various ways because of the swelling and shrinking stages of the drying droplet in super-critical carbon dioxide enriched with ethanol.
05/2008;
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ABSTRACT: In the perspective of production of dry therapeutic protein formulations, spray drying of lysozyme (as a model protein) into supercritical carbon dioxide was studied. The effects of the nozzle (i.e., co-current coaxial converging and converging-diverging, and T-mixer impinging) and process conditions (i.e., flow rates, pressure) on the drying of the lysozyme prepared in aqueous solution dried with supercritical carbon dioxide enriched with ethanol were investigated. The particle size distribution, width of particle size distribution and morphology were used to determine the effect of the various parameters assessed. Particles with a median size of approximately 1.5, approximately 5 or approximately 25 microns were produced depending of the nozzle selected. A basic comparative study of the nozzle was done by computational fluid dynamics, but the differences in particle size could not be depicted by these computations. The proportional increase of the flow rates (up to fivefold) caused a decrease in particle size (7- to 12-fold), and doubling the pressure caused a moderate decrease of the size (5-20%). The individual effect of the supercritical carbon dioxide, ethanol and solution streams was explained with a mass transfer model. Changing the ratio between flow rates slightly affected the particle size in various ways because of the swelling and shrinking stages of the drying droplet in supercritical carbon dioxide enriched with ethanol.
European Journal of Pharmaceutics and Biopharmaceutics 05/2008; 70(1):389-401. · 4.27 Impact Factor
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ABSTRACT: The processibility of 15 carbohydrates, more or less commonly used, was investigated as excipients in supercritical fluid drying. The focus was on the ability to produce amorphous powder, the stability of the powders towards crystallisation, and the residual water and ethanol content. The aqueous solutions were sprayed into a pressurised carbon dioxide-ethanol mixture flowing cocurrently through a coaxial two-fluid nozzle. The powder characteristics appeared to be influenced by the supersaturation level reached during the SCF-drying process and by the properties of the sugar species, such as water solubility and glass transition temperature, or the solution viscosities. The stability and the residual solvent content of a selected set of sugars and some mixtures were further analysed. The stability of amorphous powders was investigated at 4 degrees C, room temperature, 40 and 50 degrees C. Lactose, maltose, trehalose, raffinose, cyclodextrin, low-molecular-weight dextran and inulin could form free-flowing powders that remained amorphous during the 3-month stability study. Sucrose had to be mixed with other sugars to form a stable amorphous powder. Ethanol could be entrapped in supercritical fluid dried low-molecular-weight sugars, whereas polysaccharide powders were free of ethanol. Measures to prevent or overcome the presence of ethanol are discussed.
European Journal of Pharmaceutics and Biopharmaceutics 04/2008; 68(3):781-94. · 4.27 Impact Factor
