Chitosan hydrogels containing liposomes and cubosomes as particulate sustained release vaccine delivery systems

Sustained release depot systems have been widely investigated for their potential to improve the efficacy of subunit vaccines and reduce the requirement for boosting. The present study aimed to further enhance the immunogenicity of a sustained release vaccine by combining a depot formulation with a particulate antigen delivery system. Sustained release of the model subunit antigen, ovalbumin (OVA), was observed in vivo from chitosan thermogel-based formulations containing cationic, nanosized liposomes loaded with OVA and the immunopotentiator, Quil A (QA). Such formulations demonstrated the ability to induce cluster of differentiation (CD)8⁺ and CD4⁺ T-cell proliferation and interferon (IFN)-γ production, as well as the production of OVA-specific antibody. However, gel-incorporated liposomes showed evidence of instability and similar in vivo immune responses to liposomes in gel formulations were induced by gel-based systems loaded with soluble OVA and QA. The immunogenicity of chitosan thermogels containing cubosomes, a more stable lipidic particulate system, was therefore examined. Similarly, all gel-based formulations produced comparable effector immune responses in experimental mice, irrespective of whether the antigen and immunopotentiator were present in gels within cubosomes or in a soluble form. This work demonstrates the potential for sustained release thermogelling systems and highlights the importance of matching the physicochemical and immunological properties of the particulate system to that of the depot.     

Lecithin soybean phospholipid nano-transfersomes as potential carriers for transdermal delivery of the human growth hormone

Pharmaceutical molecules such as peptides and proteins are usually injected into the body. Numerous efforts have been made to find new noninvasive ways to administer these peptides. In this study, highly flexible vesicles (transfersomes [TFs]) were designed as a new modern transdermal drug delivery system for systemic drug administration through the skin, which had also been evaluated in vitro. In this study, two growth hormone-loaded TF formulations were prepared, using soybean lecithin and two different surfactants; F₁_sodium deoxycholate and F ₂_sodium lauryl sulfate. Thereafter, the amount of skin penetration by the two formulas was assessed using the Franz diffusion cell system. TF formulations were evaluated for size, zeta potential and in vitro skin penetration across the rat skin. Results indicated that vesicle formulations were stable for 4 weeks and their mean sizes were 241.33 ± 17 and 171 ± 12.12 nm in the F ₁ and F ₂ formulation, respectively. After application to rat skin, transport of the human growth hormone (hGH) released from the TF formulations was found to be higher than that of the hGH alone. Maximum amounts of transdermal hormone delivery were estimated to be 489.54 ± 8.301 and 248.46 ± 4.019 ng·cm−2 , for F ₁ and F ₂, respectively. The results demonstrate the capability of the TF-containing growth hormone in transdermal delivery and superiority of the F ₁ to F ₂ TFs.     

Computational stabilization of human growth hormone

Recombinant human growth hormone (hGH) is used worldwide for the treatment of pediatric hypopituitary dwarfism and in children suffering from low levels of hGH. It has limited stability in solution, and because of poor oral absorption, is administered by injection, typically several times a week. Development has therefore focused on more stable or sustained-release formulations and alternatives to injectable delivery that would increase bioavailability and make it easier for patients to use. We redesigned hGH computationally to improve its thermostability. A more stable variant of hGH could have improved pharmacokinetics or enhanced shelf-life, or be more amenable to use in alternate delivery systems and formulations. The computational design was performed using a previously developed combinatorial optimization algorithm based on the dead-end elimination theorem. The algorithm uses an empirical free energy function for scoring designed sequences. This function was augmented with a term that accounts for the loss of backbone and side-chain conformational entropy. The weighting factors for this term, the electrostatic interaction term, and the polar hydrogen burial term were optimized by minimizing the number of mutations designed by the algorithm relative to wild-type. Forty-five residues in the core of the protein were selected for optimization with the modified potential function. The proteins designed using the developed scoring function contained six to 10 mutations, showed enhancement in the melting temperature of up to 16 degrees C, and were biologically active in cell proliferation studies. These results show the utility of our free energy function in automated protein design.     

重组人生长激素长效缓释的研究进展

重组人生长激素长效缓释制剂可提高药物生物利用度,延长药物半衰期,减少药物不良反应,给疾病的临床治疗提供了更多的手段和可能。从微球、脂质体、化学修饰等方面综述了重组人生长激素长效缓释的研究进展。     

One-step synthesis of interpenetrating network hydrogels: Environment sensitivities and drug delivery properties

A novel interpenetrating network hydrogel for drug controlled release, composed of modified poly(aspartic acid) (KPAsp) and carboxymethyl chitosan (CMCTS), was prepared in aqueous system. The surface morphology and composition of hydrogels were characterized by SEM and FTIR. The swelling properties of KPAsp, KPAsp/CMCTS semi-IPN and KPAsp/CMCTS IPN hydrogels were investigated and the swelling dynamics of the hydrogels was analyzed based on the Fickian equation. The pH, temperature and salt sensitivities of hydrogels were further studied, and the prepared hydrogels showed extremely sensitive properties to pH, temperature, the ionic salts kinds and concentration. The results of controlled drug release behaviors of the hydrogels revealed that the introduction of IPN observably improved the drug release properties of hydrogels, the release rate of drug from hydrogels can be controlled by the structure of the hydrogels and pH value of the external environment, a relative large amount of drug released was preferred under simulated intestinal fluid. These results illustrated high potential of the KPAsp/CMCTS IPN hydrogels for application as drug carriers.     

Use of protein-acrylamide copolymer hydrogels for measuring protein concentration and activity

We report the development and characterization of a polyacrylamide-based protein immobilization strategy for surface-bound protein assays, including concentration detection, binding affinity, and enzyme kinetics. Glutathione S-transferase (GST) fusion proteins have been labeled with an acrylic moiety and attached to acrylic-functionalized glass surfaces through copolymerization with acrylic monomer. The specific attachment of GST-green fluorescent protein (GFP) fusion protein was more than sevenfold greater than the nonspecific attachment of nonacrylic-labeled GST-GFP; 0.32 ng/mm(2) of surface-attached GST-GFP was detectable by direct measurement of GFP fluorescence and this lower detection limit was reduced to 0.080 ng/mm(2) using indirect antibody-based detection. The polyacrylamide-based surface attachment strategy was also used to measure the kinetics of substrate phosphorylation by the kinase c-Src. Michaelis-Menten kinetic constants for the reaction occurring in solution were K(m) = 2.7 +/- 1.0 microM and V(max) = 8.1 +/- 3.1 (arbitrary units). Kinetic values for the reaction utilizing surface-immobilized substrate were K(m) = 0.36 +/- 0.033 microM and V(max) = 9.7 +/- 0.63 and were found to be independent of the acrylamide concentration within the copolymer. Such a surface attachment strategy should be applicable to the proteomics field and addresses denaturation and dehydration problems associated with protein microarray development.     

Aptamer-targeted delivery of Bcl-xL shRNA using alkyl modified PAMAM dendrimers into lung cancer cells

RNAi-based gene therapy has been recently considered as a promising approach against cancer. Targeted delivery of drug, gene or therapeutic RNAi-based systems to tumor cells is one of the important issues in order to reduce side effects on normal cells. Several strategies have been developed to improve the safety and selectivity of cancer treatments including antibodies, peptides and recently aptamers with various attractive characteristics including higher target specificity, affinity and reduced toxicity. Here we described a novel targeted delivery platform comprising modified PAMAM with 10-bromodecanoic acid (10C) and 10C-PEG for improvement of transfection efficiency, AS1411 aptamer for targeting nucleolin ligand on target cancer cells and shRNA plasmid for specific knockdown of Bcl-xL protein. Modified vector could significantly improve the transfection efficiency even after covalent or non-covalent aptamer binding compared to the non-targeted vector in A549 cells. The results of gene silencing and apoptosis assay indicated that our targeted shRNA delivery system could efficiently down-regulate the Bcl-xL expression up to 25% and induce 14% late apoptosis in target cancer cells with strong cell selectivity. This study proposed a novel targeted non-viral system for shRNA-mediated gene-silencing in cancer cells.     

Effects of calcium binding on the structure and stability of human growth hormone

Thermodynamic analysis of calcium ions binding to human growth hormone (hGH) was done at 27 °C in NaCl solution, 50 mM, using different techniques. The binding isotherm for hGH-Ca²⁺ was obtained by two techniques of ionmetry, using a Ca²⁺-selective membrane electrode, and isothermal titration calorimetry. Results obtained by two ionmetric and calorimetric methods are in good agreement. There is a set of three identical and non-interacting binding sites for calcium ions. The intrinsic dissociation equilibrium constant and the molar enthalpy of binding are 52 μM and −17.4 kJ/mol, respectively. Temperature scanning UV–vis spectroscopy was applied to elucidate the effect of Ca²⁺ binding on the protein stability, and circular dichroism (CD) spectroscopy was used to show the structural change of hGH due to the metal ion interaction. Calcium ions binding increase the protein thermal stability by increasing of the alpha helix content as well as decreasing of both beta and random coil structures.     

Enzyme delivery using protein-stabilizing and cell-penetrating 30Kc19α protein nanoparticles

Nanoparticles (NPs) are an emerging strategy for drug delivery and have been studied for the delivery of various biomolecules, such as chemically synthesized drugs and therapeutic proteins. In particular, protein NPs are non-cytotoxic and biodegradable. Application of a full length recombinant 30Kc19 protein to human serum albumin (HSA) NPs has been shown to improve the cellular uptake and stability of the cargo enzyme. In this study, we demonstrate that drug delivery can be achieved with only the α-helix domain of the 30Kc19 protein (30Kc19α), and without the addition of HSA. Protein concentration and pH were crucial for NP generation. NPs had a uniformly spherical shape with an optimal diameter of 180–230 nm, and released β-galactosidase in a sustained manner. The 30Kc19α protein provided stability to the cargo enzyme, and helped maintain the specific activity of the enzyme. X-gal staining showed effective delivery of β-galactosidase into human dermal fibroblasts. Non-cytotoxic property of the 30Kc19α protein demonstrates that such NPs could be a resourceful tool for delivering drugs to cells.     

Synergistic enhancement of protoplast growth by oxygenated perfluorocarbon and Pluronic F-68

Summary Cell suspension-derived protoplasts of albino Petunia hybrida were grown for 10 d at the interface between aqueous culture medium (KM8P) and an oxygenated (10 mbar for 15 min) perfluorocarbon liquid, perfluorodecalin. Protoplasts synthesised new cell walls and divided normally at the perfluorodecalin/culture medium interface, with a mean viability after 10 d of > 92.0%. The mean plating efficiency of protoplasts was elevated by 37% (P<0.05) following culture at the perfluorodecalin/medium interface, but was unaltered by perfluorodecalin or oxygen separately. The mean plating efficiency of protoplasts cultured at the interface was further increased to a maximium of 52% above control, in the presence of oxygenated perfluorodecalin and KM8P medium supplemented with the non-ionic, co-polymer surfactant, Pluronic F-68 at 0.01% (w/v). These findings demonstrate the effectiveness of oxygenated perfluorodecalin for promoting protoplast growth, by facilitating oxygen delivery. The finding that Pluronic F-68 further increased the plating efficiency of protoplasts cultured at the perfluorocarbon/aqueous interface suggests that these agents improve growth through separate, but cumulative, mechanisms.Abbreviations ATP adenosine triphosphate - PFCs perfluorochemicals - STP standard temperature and pressure     

Model‐based process development for the purification of a modified human growth hormone using multimodal chromatography

This study demonstrates how the multimodal Capto adhere resin can be used in concert with calcium chloride or arginine hydrochloride as mobile phase modifiers to create a highly selective purification process for a modified human growth hormone. Importantly, these processes are shown to result in significant clearance of product related aggregates and host cell proteins. Furthermore, the steric mass action model is shown to be capable of accurately describing the chromatographic process and the aggregate removal. Finally, justification of the selected operating ranges is evaluated using the model together with Latin hypercube sampling. The results in this article establish the utility of multimodal chromatography when used with appropriate mobile phase modifiers for the downstream bioprocessing of a modified human growth hormone and offer new approaches for bioprocess verification. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:1057–1064, 2014     

Characterization and in vitro evaluation of starch based hydrogels as carriers for colon specific drug delivery systems

A series of starch/methacrylic acid (MAAc) copolymer hydrogels of different compositions were synthesized using γ-rays induced polymerization and crosslinking. The effects of the preparation conditions such as the feed solution concentration, feed solution composition and irradiation dose on the gelation process of the synthesized copolymer were investigated. The swelling behavior of the starch/methacrylic acid (MAAc) copolymer hydrogels was characterized by studying the effect of the hydrogel composition on the time- and pH-dependent swelling. Swelling kinetics showed that the synthesized hydrogels possessed Fickian diffusion behavior at pH 1 and non-Fickian diffusion at pH 7 which recommend them as good candidate for colon specific drug delivery systems. The synthesized hydrogels were loaded with ketoprofen as a model drug to investigate the release behavior of the synthesized hydrogels. The results showed the ability of the hydrogels to keep the loaded drug at pH 1 and release it at pH 7. The data also showed that the release rate can be controlled by controlling the preparation conditions such as comonomer concentration and composition and irradiation dose.     

Analysis of protein folding and function using backbone modified proteins

With the recent development of chemical and biological methods to introduce backbone modifications into the polypeptide chains of proteins, there have been a growing number of site-directed mutagenesis experiments focused on understanding the role of the polypeptide backbone in protein folding and function. The substitution of a main chain amide bond with an ester bond is now a popular mutation to investigate the role of the polypeptide backbone in ligand, binding, enzyme catalysis, and protein folding. Here we review the results of studies on some 25 ester-bond containing analogues from nine different protein systems. The structural, thermodynamic, and functional consequences of introducing backbone amide- to ester-bond mutations into these protein systems are discussed.     

Preparation and characterization of poly(D,L-lactide-co-glycolide) microspheres for controlled release of human growth hormone

The purpose of this research was to assess the physicochemical properties of a controlled release formulation of recombinant human growth hormone (rHGH) encapsulated in poly(D,L-lactide-co-glycolide) (PLGA) composite microspheres. rHGH was loaded in poly(acryloyl hydroxyethyl) starch (acHES) microparticles, and then the protein-containing microparticles were encapsulated in the PLGA matrix by a solvent extraction/evaporation method. rHGH-loaded PLGA microspheres were also prepared using mannitol without the starch hydrogel microparticle microspheres for comparison. The detection of secondary structure changes in protein was investigated by using a Fourier Transfer Infrared (FTIR) technique. The composite microspheres were spherical in shape (44.6±2.47 μm), and the PLGA-mannitol microspheres were 39.7±2.50 μm. Drug-loading efficiency varied from 93.2% to 104%. The composite microspheres showed higher overall drug release than the PLGA/mannitol microspheres. FTIR analyses indicated good stability and structural integrity of HGH localized in the microspheres. The PLGA-acHES composite microsphere system could be useful for the controlled delivery of protein drugs.     

Characterization of recombinant human growth hormone variants from sodium hyaluronate-based sustained release formulation of rhGH under heat stress

This study provides the findings of investigations of potential product-related variants on recombinant human growth hormone (rhGH) in a once-weekly sustained release formulation (SR–rhGH) of sodium hyaluronate microparticles and on the rhGH bulk solution used as the active ingredient for SR–rhGH under extreme stress conditions of 24 h at 60 °C. The extent of rhGH degradation was much higher in solution (33%) than in SR–rhGH (10%). The degradation products, especially Met14 sulfoxide and deamidated rhGH variants, were separated and quantified by a modified reversed-phase high-performance liquid chromatography (RP–HPLC) method at reduced flow rate. The primary degradation product of rhGH was found to be deamidated rhGH, although an unknown peak was also detected. In contrast, the primary degradation product of SR–rhGH was Met14 sulfoxide rhGH, with no unknown peaks. Using a cell proliferation assay, the biological activities of the isolated products of SR–rhGH degradation were found to be equivalent to those of native hGH, as determined by comparison with a National Institute for Biological Standards and Control standard. In conclusion, SR–rhGH is structurally and functionally stable and maintains the intactness of rhGH.     

High throughput purification of recombinant human growth hormone using radial flow chromatography

Recombinant human growth hormone (r-hGH) was expressed in Escherichia coli as inclusion bodies. Using fed-batch fermentation process, around 670 mg/L of r-hGH was produced at a cell OD600 of 35. Cell lysis followed by detergent washing resulted in semi-purified inclusion bodies with more than 80% purity. Purified inclusion bodies were homogenous in preparation having an average size of 0.6 μm. Inclusion bodies were solubilized at pH 12 in presence of 2 M urea and refolded by pulsatile dilution. Refolded protein was purified with DEAE-anion exchange chromatography using both radial and axial flow column (50 ml bed volume each). Higher buffer flow rate (30 ml/min) in radial flow column helped in reducing the batch processing time for purification of refolded r-hGH. Radial column based purification resulted in high throughput recovery of diluted refolded r-hGH in comparison to axial column. More than 40% of inclusion body protein could be refolded into bioactive form using the above method in a single batch. Purified r-hGH was analyzed by mass spectroscopy and found to be bioactive by Nb2 cell line proliferation assay. Inclusion body enrichment, mild solubilization, pulsatile refolding and radial flow chromatography worked co-operatively to improve the overall recovery of bioactive protein from inclusion bodies.     

1H NMR studies at 360 Mhz of the methyl groups in native and chemically modified basic pancreatic trypsin inhibitor (BPTI)

In the ¹H NMR spectra obtained at 360 MHz after digital resolution enhancement, the multiplet resonances of the methyl groups in the basic pancreatic trypsin inhibitor (BPTI) were resolved. With suitable double irradiation techniques the individual methyl resonances were assigned to the different types of aliphatic amino acid residues. Furthermore, from pH titration and comparison of the native protein with chemically modified BPTI, the resonance lines of Ala 16 in the active site and Ala 58 at the C-terminus were identified. Potential applications of the resolved methyl resonances as natural NMR probes for studies of the molecular conformations are discussed.