Degradation pathways, analytical characterization and formulation strategies of a peptide and a protein. Calcitonine and human growth hormone in comparison

Thermosensitive Hydrogel Based on Poly(2-Ethyl-2-Oxazoline)-Poly(D,L-Lactide)-Poly(2-Ethyl-2-Oxazoline) for Sustained Salmon Calcitonin Delivery

This study developed a thermosensitive hydrogel based on poly(2-ethyl-2-oxazoline)-poly(D,L-lactide)-poly(2-ethyl-2-oxazoline) (PPP) for the delivery of salmon calcitonin to improve the hypocalcemic effect. The tube inversion and rheological tests revealed that the copolymer solution underwent temperature-dependent sol-gel-sol transitions. Observation by scanning electron microscopy (SEM) showed that the hydrogel exhibited a porous three-dimensional network. The swelling test demonstrated that there was a maximum swelling ratio at low temperature (25°C) as compared with the high temperature (37°C). In vitro release revealed that the PPP hydrogel were capable of sustained release of salmon calcitonin (sCT). The in vivo biodegradability study indicated the good degradability of PPP hydrogel. More importantly, the in vivo retention time of the hydrogel in situ was significantly prolonged after subcutaneous injection of the PPP hydrogel compared to the F127 hydrogel. In vivo pharmacodynamics analysis showed that the hypocalcemic effect of both PPP and F127 hydrogel was significantly greater than that of sCT solution, and the mean serum Ca reduction effect could be maintained for 24 h of PPP hydrogel, indicating that PPP hydrogel could achieve a significant enhanced hypocalcemic effect. In conclusion, the PPP hydrogel has been shown to be prospective as a controlled release carrier for injection delivery of protein drugs.

Hydrogels For Peptide Hormones Delivery: Therapeutic And Tissue Engineering Applications

Peptides are the most abundant biological compounds in the cells that act as enzymes, hormones, structural element, and antibodies. Mostly, peptides have problems to move across the cells because of their size and poor cellular penetration. Therefore, a carrier that could transfer peptides into cells is ideal and would be effective for disease treatment. Until now, plenty of polymers, e.g., polysaccharides, polypeptides, and lipids were used in drug delivery. Hydrogels made from polysaccharides showed significant development in targeted delivery of peptide hormones because of their natural characteristics such as networks, pore sizes, sustainability, and response to external stimuli. The main aim of the present review was therefore, to gather the important usages of the hydrogels as a carrier in peptide hormone delivery and their application in tissue engineering and regenerative medicine.

Development of a novel stability indicating RP-HPLC method for quantification of Connexin43 mimetic peptide and determination of its degradation kinetics in biological fluids

Connexin43 mimetic peptide (Cx43MP) has been intensively investigated for its therapeutic effect in the management of inflammatory eye conditions, spinal cord injury, wound healing and ischemia-induced brain damage. Here, we report on a validated stability-indicating reversed-phase high performance liquid chromatography (RP-HPLC) method for the quantification of Cx43MP under stress conditions. These included exposure to acid/base, light, oxidation and high temperature. In addition, the degradation kinetics of the peptide were evaluated in bovine vitreous and drug-free human plasma at 37 °C. Detection of Cx43MP was carried out at 214 nm with a retention time of 7.5 min. The method showed excellent linearity over the concentration range of 0.9-250 µg/mL (R2 ≥ 0.998), and the limits of detection (LOD) and quantification (LOQ) were found to be 0.90 and 2.98 μg/mL, respectively. The accuracy of the method determined by the mean percentage recovery at 7.8, 62.5 and 250 µg/mL was 96.79%, 98.25% and 99.06% with a RSD of < 2.2%. Accelerated stability studies revealed that Cx43MP was more sensitive to basic conditions and completely degraded within 24 h at 37 °C (0% recovery) and within 12 h at 80 °C (0.34% recovery). Cx43MP was found to be more stable in bovine vitreous (t1/2slow= 171.8 min) compared to human plasma (t1/2slow = 39.3 min) at 37 °C according to the two phase degradation kinetic model. These findings are important for further pre-clinical development of Cx43MP.

Formulation for a novel inhaled peptide therapeutic for idiopathic pulmonary fibrosis

A caveolin-1 scaffolding domain, CSP7, is a newly developed peptide for the treatment of idiopathic pulmonary fibrosis. To develop a CSP7 formulation for further use we have obtained, characterized and compared a number of lyophilized formulations of CSP7 trifluoroacetate with DPBS and in combination with excipients (mannitol and lactose at molar ratios 1:5, 70 and 140). CSP7 trifluoroacetate was stable (>95%) in solution at 5 and 25 °C for up to 48 h and tolerated at least 5 freeze/thaw cycles. Lyophilized cakes of CSP7 trifluoroacetate with excipients were stable (>96%) for up to 4 weeks at room temperature (RT), and retained more than 98% of the CSP7 trifluoroacetate in the solution at 8 h after reconstitution at RT. The lyophilized CSP7 formulations were stable for up to 10 months at 5 °C protected from moisture. Exposure of the lyophilized cakes of CSP7 to 75% relative humidity (RH) resulted in an increase in the absorbed moisture, promoted crystallization of the excipients and induced reversible formation of CSP7 aggregates. Increased molar ratio of mannitol slightly affected formation of the aggregates. In contrast, lactose significantly decreased (up to 20 times) aggregate formation with apparent saturation at the molar ratio of 1:70. The possible mechanisms of stabilization of CSP7 trifluoroacetate in solid state by lactose include physical state of the bulking agent and the interactions between lactose and CSP7 trifluoroacetate (e.g. formation of a Schiff base with the N-terminal amino group of CSP7). Finally, CSP7 trifluoroacetate exhibited excellent stability during nebulization of formulations containing mannitol or lactose.

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, especiallyMet14 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.

Preparation and characterization of salmon calcitonin-biotin conjugates

This study was performed to prepare and characterize the biotinylated Salmon calcitonin (sCT) for oral delivery and evaluate the hypocalcemic effect of biotinylated-sCTs in rats. Biotinylated sCTs was characterized by using high performance liquid chromatography (HPLC) and MALDITOF-MS. The effect of biotinylation on permeability across Caco-2 cell monolayers was examined. Their hypocalcemic effect was determined in rats. Mono- and di-bio-sCTs were separated by reverse phase HPLC. The molecular weights of mono-bio-sCT and di-bio-sCT were determined to be 3,660.5 and 3,900.2 Da, respectively. The permeability of biotinylated-sCTs across Caco-2 cell monolayers was observed with a significant enhancement compared with sCT. Intrajejunal (ij) administration of mono-bio-sCT and di-bio-sCT resulted in sustained reduction in serum calcium levels, with a maximum reduction (% max(d)) of 21.6% and 30% after 4 h and 6 h of application, respectively. The biotin conjugation of sCT may be a promising strategy for increasing the oral bioavailability of sCT and achieving sustained calcium-lowering effects.

Release characteristics of salmon calcitonin from dextran hydrogels for colon-specific delivery

Biodegradable dextran hydrogels were synthesized by crosslinking dextran (T-70) with epichlorohydrin (ECH) for the in vitro colon-specific delivery of salmon calcitonin (sCT). Crosslinking reaction was performed in 2.8 M NaOH solution both in the presence and absence of ethanol at 10 and 23 degrees C. Biodegradation kinetics of dextran hydrogels were studied and, in the presence of 0.7 IU ml-1 dextranase, dextran discs lost 71.0% and 56.5% of their dry weight within 80 h at pH 5.5 and 7.0, respectively. sCT was derivatized with the fluorescamine (FSM) at borate buffer (pH 9.0) and the quantitative determinations were performed using spectrofluorimetric method (lambdaex: 390 nm, lambdaem: 475 nm). In vitro release studies for the hydrogels prepared in the presence of ethanol were carried out in simulated gastrointestinal fluids. Results indicated that 84.9% of the loaded-sCT was released for 17 h and dextran hydrogel prepared in the presence of ethanol may be a good delivery device for the colon-specific delivery of other peptide-type drugs as well as sCT.

Protein aggregation and its inhibition in biopharmaceutics

Protein aggregation is arguably the most common and troubling manifestation of protein instability, encountered in almost all stages of protein drug development. Protein aggregation, along with other physical and/or chemical instabilities of proteins, remains to be one of the major road barriers hindering rapid commercialization of potential protein drug candidates. Although a variety of methods have been used/designed to prevent/inhibit protein aggregation, the end results are often unsatisfactory for many proteins. The limited success is partly due to our lack of a clear understanding of the protein aggregation process. This article intends to discuss protein aggregation and its related mechanisms, methods characterizing protein aggregation, factors affecting protein aggregation, and possible venues in aggregation prevention/inhibition in various stages of protein drug development.

Preparation of bionanoreactor based on core-shell structured polyion complex micelles entrapping trypsin in the core cross-linked with glutaraldehyde

Recently, the polyion complex (PIC) micelle has been suggested as a promising carrier system for peptide and proteins. However, its utilities are limited by its sensitivity to the environment such as dilution and ionic strength of the solution. In this study, to overcome these obstructions, PIC micelles prepared from an anionic block copolymer, poly(ethylene glycol)-poly(alpha,beta-aspartic acid), and a cationic protein, trypsin, were cross-linked with glutaraldehyde through the Schiff base formation. On the basis of a light scattering technique, the results revealed an efficient resistance of the cross-linked PIC micelle to a high salt concentration, which was a key parameter controlling the structure of the PIC micelles. Moreover, the stability of trypsin after cross-linking was remarkably improved. Evidently, as a bionanoreactor and/or bionanoreservoir, the PIC micelles entrapping protein molecules in the cross-linked core reveal an improved stability, allowing their wide application in the fields of biotechnology and pharmaceutical sciences.

Pulmonary delivery of growth hormone using dry powders and visualization of its local fate in rats

A dry powder aerosol formed of human growth hormone (hGH), lactose and dipalmitoylphosphatidylcholine was assessed for systemic delivery of the hormone in rats. The fate of the protein locally in the deep lung was examined post-delivery. The powder was prepared by spray-drying and presented a primary particle diameter of 4.4 microm and a tap density of 0.069 g/cm(3). The mass median aerodynamic diameter was 4.4 micron in the multi-stage liquid impinger at 60 l/min using a Spinhaler device. The emitted dose and fine particle fraction were 89% and 58%, respectively. Varying the airflow rate from 30 to 90 l/min had limited impact on aerosolization properties in vitro. No hGH dimers or glycation adducts were produced during formulation of the powder. hGH absorbed into the bloodstream with a time to peak of 23 and 52 min and with an absolute bioavailability of 23% and 8% following intratracheal insufflation of the dry powder and intratracheal spray-instillation of a solution of the hormone, respectively. Confocal imaging of rat lung revealed an intense uptake of fluorescein isothiocyanate (FITC)-hGH by alveolar macrophages as early as 1 h post-delivery. A dry powder aerosol made of selected GRAS excipients improved absorption of hGH from the lung over a simple solution.

Long-term stabilization of recombinant human interferon alpha 2b in aqueous solution without serum albumin

The development of parenteral solution dosage forms of interferon alpha 2 (rhIFN-alpha2) without human albumin may significantly diminish the problem of forming highly immunogenic rhIFN-alpha 2b aggregates and the potential risk of blood-transmitted diseases caused by infectious viruses and often living pathogens that may be present in the plasma. With this purpose, we evaluated the compatibility of type I borosilicate glass vials and chlorobutyl stoppers with rhIFN-alpha 2b in an aqueous solution. At the same time, we carried out a targeted formulation screen at 37 degrees C of single or combined (e.g. polysorbate 80, EDTA Na(2), PEG 400) potentially stabilizing excipients. Quantified biochemical results from 12 independent batches of rhIFN-alpha 2b in a polysorbate/benzyl alcohol-based vehicle formulated at pH 7.4 were all found within the limits established by the World Health Organization for this cytokine. Real-time storage data confirmed the excellent biochemical long-term (30 months) stability of rhIFN-alpha 2b in this aqueous solution formulation. Analyses were performed at intervals throughout the time period using reverse-phase high-performance liquid chromatography, a sandwich-type enzyme-linked immunosorbent assay, and antiviral activity as stability-indicating assays. Furthermore, both the physical stability (color, odor, appearance, pH, and absence of particulate material) and the sterility of this formulation were maintained under the proposed shelf conditions.

Sustained release of human growth hormone from microcapsules prepared by a solvent evaporation technique

Biodegradable microcapsules for sustained release of recombinant human growth hormone (rhGH) were prepared by a solid-in-oil-in-water (S/O/W) emulsion solvent evaporation technique using lyophilized protein microparticles. The minimum mean particle size of rhGH in S/O dispersions was 2.8-3.0 microm when ammonium acetate was added at molar ratios of 10-20 times against rhGH. High entrapment of rhGH in microcapsules was achieved by incorporating rhGH powder with a smaller particle size obtained by lyophilizing with ammonium acetate. As the particle size of rhGH decreased, the in vivo initial release decreased, while subsequent serum levels of rhGH in sustained release phase were higher. Addition of zinc oxide to microcapsules resulted in higher serum levels than those prepared without zinc oxide, suggesting a stabilizing effect of zinc oxide after subcutaneous injection into rats. The release profile of rhGH from microcapsules was controllable by selecting the proper copoly(DL-lactic/glycolic)acid (PLGA) with L/G ratio and molecular weight. Utilization of rhGH powder with a smaller particle size obtained by lyophilizing with ammonium acetate is essential for preparation of microcapsules with high entrapment and well-controlled sustained release profile with small initial release.

Stability aspects of salmon calcitonin entrapped in poly(ether-ester) sustained release systems

Poly(ether-ester)s composed of hydrophilic poly(ethylene glycol)-terephthalate (PEGT) blocks and hydrophobic poly(butylene terephthalate) (PBT) blocks were studied as matrix for the controlled release of calcitonin. Salmon calcitonin loaded PEGT/PBT films were prepared from water-in-oil emulsions. The initial calcitonin release rate could be tailored by the copolymer composition, but incomplete release of calcitonin was observed. FTIR measurements indicated aggregation of calcitonin in the matrix, which was not due to the preparation method of the matrices, but due to the instability of calcitonin in an aqueous environment. Release experiments showed the susceptibility of calcitonin towards the composition of the release medium, in particular to the presence of metal ions. With increasing amount of sodium ions, a decrease in the total amount of released calcitonin was observed due to enhanced aggregation. The calcitonin had to be stabilized in the matrix to prevent aggregation. Incorporation of sodium dodecyl sulphate (SDS) as a stabilizer in PEGT/PBT matrices increased the percentage of calcitonin released, but could not avoid aggregation on a longer term.

Transmucosal delivery systems for calcitonin: a review

The commercial availability of peptides and proteins and their advantages as therapeutic agents have been the basis for tremendous efforts in designing delivery systems for such agents. The protection of these agents from biological fluids and physiological interactions is crucial for the treatment efficacy. One such agent is salmon calcitonin, a 32 amino-acid polypeptide hormone used in the treatment of bone diseases such as Paget's disease, hypercalcemia and osteoporosis. Researchers have studied different routes to deliver salmon calcitonin more effectively, including nasal, oral, vaginal and rectal delivery. These systems are designed to protect the polypeptide from the biological barriers that each delivery route imposes. Oil-based and polymer-based delivery systems are discussed.

The formulation of biopharmaceutical products

Biopharmaceutical products represent a diverse group of products that includes proteins, peptides, nucleic acids, whole cells, viral particles and vaccines. The conformation of the macromolecule or cell must be maintained to retain biological activity, and animal models for biological activity and characterization assays are often developed in tandem with initial formulation studies. This presents the formulation scientist with a unique set of challenges when compared to those for small molecules. This review focuses on approaches to the formulation of macromolecules into biopharmaceutical products, and provides examples of studies that have been undertaken within the authors' laboratories.