Preparing and evaluating delivery systems for proteins

Advanced Formulation Approaches for Proteins

Proteins and peptides are highly desirable as therapeutic agents, being highly potent and specific. However, there are myriad challenges with processing them into patient-friendly formulations: they are often unstable and have a tendency to aggregate or degrade upon storage. As a result, the vast majority of protein actives are delivered parenterally as solutions, which has a number of disadvantages in terms of cost, accessibility, and patient experience. Much work has been undertaken to develop new delivery systems for biologics, but to date this has led to relatively few products on the market. In this chapter, we review the challenges faced when developing biologic formulations, discuss the technologies that have been explored to try to overcome these, and consider the different delivery routes that can be applied. We further present an overview of the currently marketed products and assess the likely direction of travel in the next decade.

Rational Design and Development of Polymeric Nanogels as Protein Carriers

Proteins have gained significant attention as potential therapeutic agents owing to their high specificity and reduced toxicity. Nevertheless, their clinical utility is hindered by inherent challenges associated with stability during storage and after in vivo administration. To overcome these limitations, polymeric nanogels (NGs) have emerged as promising carriers. These colloidal systems are capable of efficient encapsulation and stabilization of protein cargoes while improving their bioavailability and targeted delivery. The design of such delivery systems requires a comprehensive understanding of how the synthesis and formulation processes affect the final performance of the protein. This review highlights critical aspects involved in the development of NGs for protein delivery, with specific emphasis on loading strategies and evaluation techniques. For example, factors influencing loading efficiency and release kinetics are discussed, along with strategies to optimize protein encapsulation through protein-carrier interactions to achieve the desired therapeutic outcomes. The discussion is based on recent literature examples and aims to provide valuable insights for researchers working toward the advancement of protein-based therapeutics.

Enhanced oral absorption and anti-inflammatory activity of ellagic acid via a novel type of case in nanosheets constructed by simple coacervation

As a nature component, ellagic acid (EA) shows a broad array of pharmacological activities but is lost in clinical translation partly due to poor aqueous solubility. In an effort to enhance its oral absorption, novel EA-loaded casein nanosheets (EA@CAS-NSs) was constructed by simple coacervation and investigated for in vitro characterization and in vivo evaluation. The influences of factors including pH, EA concentration, and mass ratio of CAS and EA on properties of EA@CAS-NSs were also studied. The low pH value and high matrix and drug ratio were harmful to small particle size of EA@CAS-NSs. Meanwhile, the low and high concentration of EA went against the 8 h short-term stability of EA@CAS-NSs. Interestingly, EA@CAS-NSs showed a typical disk-like structure with a diameter of 100-400 nm and good long-term storage stability for 24 months. The molecular structure of EA in NSs remained unchanged, but the EA in NSs had lower crystallinity and better thermal stability than in raw state. No chemical interaction occurred between CAS and EA, although the intermolecular distance of them was less than 10 nm. In simulated intestinal fluid, the solubility of EA in NSs was nearly three times that of raw EA, and the dissolution of EA@CAS-NSs was 12 folds of raw EA at 120 min. With oral administration, EA@CAS-NSs demonstrated an improved oral absorption in rats, as evidenced by an AUC_0-24 value 2.34 times higher than raw EA. Also, the EA@CAS-NSs showed a better anti-inflammatory activity than EA. Generally, EA@CAS-NSs could be a potential strategy for the further clinic use of EA.

Comparative analysis of pharmacokinetics of vancomycin hydrochloride in rabbits after ocular, intragastric, and intravenous administration by LC-MS/MS

The objective of this study was to compare the pharmacokinetics of vancomycin hydrochloride administered into rabbits through different routes and explore the feasibility of peptide drugs entering the systemic circulation through ocular administration. A convenient, accurate, and rapid liquid chromatography-trandem mass spectrometric (LC-MS/MS) method was established and used for the determination of vancomycin hydrochloride in rabbit plasma after intravenous administration (1.5 mg/kg), intragastric, and ocular administration (15 mg/kg). The pharmacokinetic parameters were analyzed using the DAS 2.0 software. We obtained a linear calibration curves vancomycin hydrochloride in plasma of rabbits over a concentration range of 0.05-10.0 μg/mL (R ² > 0.9995), the interassay accuracy was within 5%, precision of 1.66-3.38%, and recovery of >85%. No matrix effects were observed. The absolute bioavailability of vancomycin hydrochloride after intragastric and ocular administration was 1.0 and 7.3%, with the half-life values of 63.1 and 138.5 min, respectively. Therefore, the LC-MS/MS method established in this experiment was suitable for the determination of vancomycin hydrochloride. Vancomycin hydrochloride was rapidly absorbed into the blood circulation after ocular administration. Ocular administration was linked to higher bioavailability compared with intragastric administration, suggesting that the former will become a route for the delivery of peptide drugs.

Preparation and investigation of core-shell nanoparticles containing human interferon-α

Sustained release of active interferon-α (IFN-α) has been achieved from core-shell nanoparticles (NPs) prepared by aqueous precipitation of IFN-α-enriched human serum albumin (HSA-IFN-α) and layer-by-layer (L-b-L) by coating of the IFN-α NPs with poly(sodium-4-styrene) sulphonate (PSS) and chitosan (Chit). The concentration and the pH of HSA solution were optimized during the development of this method. Dynamic light scattering (DLS), zeta-potential, thermal analysis (differential scanning calorimetry (DSC) and termogravimetry (TG)), X-ray diffraction (XRD), IFN-α activity and morphology (transmission electron microscope (TEM)) studies were used to control the preparation and analyse the products. The dissolution kinetics of NPs was measured in vitro over 7 days in Hanson dissolution tester with Millex membrane. In vivo studies in Pannon white rabbit detected steady IFN-α plasma level for 10 days after subcutaneous injection administration of the HSA-IFN-α NPs. The IFN-α plasma concentration was detected by using the enzyme-linked immunosorbent assay (ELISA) method. In the present paper we discuss the preparation method, the optimization steps and the results of in vitro and in vivo release studies. It was established that 76.13% HSA-IFN-α are encapsulated in the core-shell NPs.

Additive potential of combination therapy against cryptococcosis employing a novel amphotericin B and fluconazole loaded dual delivery system

Cryptococcus neoformans is one of the most lethal fungi causing mortality across the globe. Immuno-competent patients and patients taking immuno-suppressive medications are extremely susceptible to its infection. For effective removal of cryptococcal burden, there is an urgent need for new forms of therapy. In the present study, we have explored the potential effects of amphotericin B (AMB) and fluconazole (FLC) in combination, against cryptococcosis in Swiss albino mice. To enhance the therapeutic potential of the tested drugs, they were entrapped into fibrin microspheres; a dual delivery vehicle comprising of poly-lactide co-glycolide (PLGA) microsphere that was additionally encapsulated into the fibrin cross-linked plasma bead. Dynamics of fibrin microspheres included survival and fungal burden in lung, liver and spleen of treated mice. While each drug was effective in combination or alone, prominent additive potential of AMB and FLC were clearly observed when used in fibrin microsphere. Significant reduction in fungal burden and increase in survival rate of AMB + FLC-fibrin microspheres treated mice shows an extensive accessibility of both tested drugs without any side-effects. A full potential of two-drug combination encapsulated in fibrin microspheres proposes an effective approach of safe delivery to the target site in their intact form and decrease the drug associated toxicities.

Promoting early neovascularization of SIS-repaired abdominal wall by controlled release of bioactive VEGF

Insufficient early neovascularization post-operation is thought to be the main reason of surgical recurrence of porcine small intestinal submucosa (SIS)-repaired abdominal wall defects.

Specific ion effects on the particle size distributions of cell culture-derived influenza A virus particles within the Hofmeister series

Virus particle (VP) aggregation can have serious implications on clinical safety and efficacy of virus-based therapeutics. Typically, VP are suspended in buffers to establish defined product properties. Salts used to achieve these properties show specific effects in chemical and biological systems in a reoccurring trend known as Hofmeister series (HS). Hofmeister series effects are ubiquitous and can affect colloidal particle systems. In this study, influences of different ions (anions: SO4 2-, HPO4 2-, Cl-, Br-, NO3 -, I-; cations: K+, Na+, Li+, Mg2+, Ca2+) on particle size distributions of cell culture-derived influenza VP were investigated. For the experimental setup, influenza virus A/Puerto Rico/8/34 (H1N1) VP produced in adherent and suspension Madin Darby canine kidney cells were used. Inactivated and concentrated virus harvests were dialyzed against buffers containing the ions of interest, followed by differential centrifugal sedimentation to measure particle size distributions. VP from both cell lines showed no aggregation over a wide range of buffers containing different salts in concentrations ≥60 mM. However, when dialyzed to low salt or Ca2+ buffers, VP produced in adherent cells showed increased aggregation compared to VP produced in suspension cells. Additionally, changes in VP diameters depending on specific ion concentrations were observed that partially reflected the HS trend.

Strontium ranelate-loaded PLGA porous microspheres enhancing the osteogenesis of MC3T3-E1 cells

Biodegradable poly lactic-co-glycolic acid (PLGA) has been used as a tissue engineering scaffold as well as a carrier for the delivery of proteins, drugs, and other macromolecules.

Alternating Magnetic Field-Responsive Hybrid Gelatin Microgels for Controlled Drug Release

Magnetically-responsive nano/micro-engineered biomaterials that enable a tightly controlled, on-demand drug delivery have been developed as new types of smart soft devices for biomedical applications. Although a number of magnetically-responsive drug delivery systems have demonstrated efficacies through either in vitro proof of concept studies or in vivo preclinical applications, their use in clinical settings is still limited by their insufficient biocompatibility or biodegradability. Additionally, many of the existing platforms rely on sophisticated techniques for their fabrications. We recently demonstrated the fabrication of biodegradable, gelatin-based thermo-responsive microgel by physically entrapping poly(N-isopropylacrylamide-co-acrylamide) chains as a minor component within a three-dimensional gelatin network. In this study, we present a facile method to fabricate a biodegradable drug release platform that enables a magneto-thermally triggered drug release. This was achieved by incorporating superparamagnetic iron oxide nanoparticles and thermo-responsive polymers within gelatin-based colloidal microgels, in conjunction with an alternating magnetic field application system.

Improved oral absorption of exenatide using an original nanoencapsulation and microencapsulation approach

Oral delivery is the most convenient and favorable route for chronic administration of peptides and proteins to patients. However, many obstacles are faced when developing such a delivery route. Nanoparticles (NPs) are among the leading innovative solutions for delivery of these drugs. Exenatide is a peptidic drug administered subcutaneously (SC) twice a day chronically as an add-on therapy for the worldwide pandemic disease, diabetes. Many attempts to develop oral nanocarriers for this drug have been unsuccessful due to the inability to retain this hydrophilic macromolecule under sink conditions or to find a suitable cross-linker which does not harm the chemical integrity of the peptide. In this study, we report about an original oral delivery solution based on a mixture of albumin and dextran NPs cross-linked using sodium trimetaphosphate (STMP). Moreover, we suggest a second defense line of gastro-resistant microparticles (MPs) composed of an appropriate ratio of Eudragit® L100-55 (Eudragit L) and hydroxypropylmethylcellulose (HPMC), for additional protection to these NPs presumably allowing them to be absorbed in the intestine intact. Our results demonstrate that such a system indeed improves the relative oral bioavailability of exenatide to a level of about 77% compared to subcutaneous injection due to the presence of dextran in the coating wall of the NPs which apparently promotes the lymphatic uptake in the enterocytes. This technology may be a milestone on the way to deliver other peptides and proteins orally.

Identification and Assessment of Octreotide Acylation in Polyester Microspheres by LC-MS/MS

Purpose

Polyesters with hydrophilic domains, i.e., poly(d,l-lactic-co-glycolic-co-hydroxymethyl glycolic acid) (PLGHMGA) and a multiblock copolymer of poly(ε-caprolactone)-PEG-poly(ε-caprolactone) and poly(l-lactide) ((PC-PEG-PC)-(PL)) are expected to cause less acylation of encapsulated peptides than fully hydrophobic matrices. Our purpose is to assess the extent and sites of acylation of octreotide loaded in microspheres using tandem mass spectrometry analysis.

Methods

Octreotide loaded microspheres were prepared by a double emulsion solvent evaporation technique. Release profiles of octreotide from hydrophilic microspheres were compared with that of PLGA microspheres. To scrutinize the structural information and localize the actual modification site(s) of octreotide, liquid chromatography ion-trap mass spectrometry (LC-ITMS) was performed on the acylated adducts.

Results

Hydrophilic microspheres showed less acylated adducts in comparison with PLGA microspheres. LC-MS/MS showed that besides the N-terminus and primary amine of lysine, the primary hydroxyl of the end group of octreotide was also subjected to acylation. Nucleophilic attack of the peptide can also occur to the carbamate bond presented in (PC-PEG-PC)-(PL) since 1,4-butanediisocyanate was used as the chain extender.

Conclusions

Hydrophilic polyesters are promising systems for controlled release of peptide because substantially less acylation occurs in microspheres based on these polymers. LC-ITMS provided detailed structural information of octreotide modifications via mass analysis of ion fragments.

Electronic supplementary material

The online version of this article (doi:10.1007/s11095-015-1685-3) contains supplementary material, which is available to authorized users.

Intrathecal delivery of protein therapeutics to the brain: a critical reassessment

Disorders of the central nervous system (CNS), including stroke, neurodegenerative diseases, and brain tumors, are the world's leading causes of disability. Delivery of drugs to the CNS is complicated by the blood-brain barriers that protect the brain from the unregulated leakage and entry of substances, including proteins, from the blood. Yet proteins represent one of the most promising classes of therapeutics for the treatment of CNS diseases. Many strategies for overcoming these obstacles are in development, but the relatively straightforward approach of bypassing these barriers through direct intrathecal administration has been largely overlooked. Originally discounted because of its lack of usefulness for delivering small, lipid-soluble drugs to the brain, the intrathecal route has emerged as a useful, in some cases perhaps the ideal, route of administration for certain therapeutic protein and targeted disease combinations. Here, we review blood-brain barrier functions and cerebrospinal fluid dynamics and their relevance to drug delivery via the intrathecal route, discuss animal and human studies that have investigated intrathecal delivery of protein therapeutics, and outline several characteristics of protein therapeutics that can allow them to be successfully delivered intrathecally.

Biodegradable dextran hydrogels for protein delivery applications

The rapid development of protein-based pharmaceuticals over recent decades has tremendously increased the need for suitable delivery systems, guaranteeing a safe and controlled delivery of proteinacious drugs. Hydrogels offer good opportunities as protein delivery systems or tissue engineering scaffolds owing to an inherent biocompatibility. Their hydrophilic, soft and rubbery nature ensures minimal tissue irritation and a low tendency of cells and proteins to adhere to the hydrogel surface. A variety of both natural and synthetic polymers have been used for the design of hydrogels, in which network formation is established by chemical or physical crosslinking. This review introduces the general features of hydrogels and focuses on dextran hydrogels in particular. Chemically and physically crosslinked systems are described and their potential suitability as protein delivery systems, as well as tissue engineering scaffolds are discussed. Special attention is given to network properties, protein delivery, degradation behavior and biocompatibility.

Novel preparation method for sustained-release PLGA microspheres using water-in-oil-in-hydrophilic-oil-in-water emulsion

An increasing number of drugs are needing improved formulations to optimize patient compliance because of their short half-lives in blood. Sustained-release formulations of drugs are often required for long-term efficacy, and microspheres are among the most popular ones. When drugs are encapsulated into microsphere formulations, different methods of preparation need to be used according to specific clinical requirements and the differing physicochemical characteristics of individual drugs. In this work, we developed a novel method for sustained-release drug delivery using a water-in-oil-in-hydrophilic oil-in-water (w/o/oh/w) emulsion to encapsulate a drug into poly(lactic-co-glycolic acid) (PLGA) microspheres. Different effects were achieved by varying the proportions and concentrations of hydrophilic oil and PLGA. Scanning electron and optical microscopic images showed the surfaces of the microspheres to be smooth and that their morphology was spherical. Microspheres prepared using the w/o/oh/w emulsion were able to load protein efficiently and had sustained-release properties. These results indicate that the above-mentioned method might be useful for developing sustained-release microsphere formulations in the future.

Development of dextran nanoparticles for stabilizing delicate proteins

One of the most challenging problems in the development of protein pharmaceuticals is to deal with stabilities of proteins due to its complicated structures. This study aims to develop a novel approach to stabilize and encapsulate proteins into dextran nanoparticles without contacting the interface between the aqueous phase and the organic phase. The bovine serum albumin, granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), β-galactosidase, and myoglobin were selected as model proteins. The proteins were added into an aqueous solution containing the dextran and polyethylene glycol, and then encapsulated into dextran nanoparticles by aqueous-aqueous freezing-induced phase separation. The encapsulation efficiency and recovery of dextran nanoparticles were determined. The dextran nanoparticles loaded with proteins were characterized by scanning electron microscopy and particle size analysis. The protein aggregation was determined by size-exclusion chromatography-high-performance chromatography, and the bioactivity of proteins recovered during formulation steps was determined. The bioactivity of GM-CSF, G-CSF, and β-galactosidase were examined by the proliferation of TF-1 cell, NSF-60 cell, and ortho-nitrophenyl-β-galactoside assay, respectively. The results of bioactivity recovered show that this novel dextran nanoparticle can preserve the protein's bioactivity during the preparation process. LysoSensor™ Yellow/Blue dextran, a pH-sensitive indicator with fluorescence excited at two channels, was encapsulated into dextran nanoparticles to investigate the ability of dextran nanoparticles to resist the acidic microenvironment (pH < 2.5). The result shows that the dextran nanoparticles attenuate the acidic microenvironment in the poly (lactic-co-glycolic acid) microsphere by means of the dilution effect. These novel dextran nanoparticles provided an appealing approach to stabilize the delicate proteins for administration.

Design and evaluation of a novel nanoparticulate-based formulation encapsulating a HIP complex of lysozyme

Formulation development of protein therapeutics using polymeric nanoparticles has found very little success in recent years. Major formulation challenges include rapid denaturation, susceptibility to lose bioactivity in presence of organic solvents and poor encapsulation in polymeric matrix. In the present study, we have prepared hydrophobic ion pairing (HIP) complex of lysozyme, a model protein, using dextran sulfate (DS) as a complexing polymer. We have optimized the process of formation and dissociation of HIP complex between lysozyme and DS. The effect of HIP complexation on enzymatic activity of lysozyme was also studied. Nanoparticles were prepared and characterized using spontaneous emulsion solvent diffusion method. Furthermore, we have also investigated release of lysozyme from nanoparticles along with its enzymatic activity. Results of this study indicate that nanoparticles can sustain the release of lysozyme without compromising its enzymatic activity. HIP complexation using a polymer may also be employed to formulate sustained release dosage forms of other macromolecules with enhanced encapsulation efficiency.

Injectable hydrogel for sustained protein release by salt-induced association of hyaluronic acid nanogel

A hyaluronic acid-based anionic nanogel formed by self-assembly of cholesteryl-group-bearing HA is designed for protein delivery. The HA nanogel spontaneously binds various types of proteins without denaturation, such as recombinant human growth hormone, erythropoietin, exendin-4, and lysozyme. The HA nanogel shows unique colloidal properties, in particular that an injectable hydrogel is formed by salt-induced association of the HA nanogel. A pharmacokinetic study in rats shows that an in situ gel formulation, prepared by simply mixing rhGH and HA nanogel in phosphate buffer, maintains plasma rhGH levels within a narrow range over one week. Therefore, HA nanogels offer a simple method for easy formulation of therapeutic proteins and are effective for sustained protein release systems.

Bovine β-lactoglobulin is dimeric under imitative physiological conditions: dissociation equilibrium and rate constants over the pH range of 2.5-7.5

The oligomerization of β-lactoglobulin (βLg) has been studied extensively, but with somewhat contradictory results. Using analytical ultracentrifugation in both sedimentation equilibrium and sedimentation velocity modes, we studied the oligomerization of βLg variants A and B over a pH range of 2.5-7.5 in 100 mM NaCl at 25°C. For the first time, to our knowledge, we were able to estimate rate constants (k(off)) for βLg dimer dissociation. At pH 2.5 k(off) is low (0.008 and 0.009 s(-1)), but at higher pH (6.5 and 7.5) k(off) is considerably greater (>0.1 s(-1)). We analyzed the sedimentation velocity data using the van Holde-Weischet method, and the results were consistent with a monomer-dimer reversible self-association at pH 2.5, 3.5, 6.5, and 7.5. Dimer dissociation constants K(D)(2-1) fell close to or within the protein concentration range of ∼5 to ∼45 μM, and at ∼45 μM the dimer predominated. No species larger than the dimer could be detected. The K(D)(2-1) increased as |pH-pI| increased, indicating that the hydrophobic effect is the major factor stabilizing the dimer, and suggesting that, especially at low pH, electrostatic repulsion destabilizes the dimer. Therefore, through Poisson-Boltzmann calculations, we determined the electrostatic dimerization energy and the ionic charge distribution as a function of ionic strength at pH above (pH 7.5) and below (pH 2.5) the isoelectric point (pI∼5.3). We propose a mechanism for dimer stabilization whereby the added ionic species screen and neutralize charges in the vicinity of the dimer interface. The electrostatic forces of the ion cloud surrounding βLg play a key role in the thermodynamics and kinetics of dimer association/dissociation.

Poly-ε-caprolactone microspheres containing interferon alpha as alternative formulations for the treatment of chronic hepatitis C

Interferon-alpha (IFN-alpha) is one of the main drugs used in the treatment of hepatitis C. Use of IFN-alpha has some limitations that result in poor treatment efficacy and low patient compliance. Therefore, the aim of this study was to develop poly-ε-caprolactone (PCL) microspheres containing IFN-alpha as an alternative for the treatment of chronic hepatitis C. Microspheres were prepared using the multiple emulsion followed by solvent evaporation technique. Particle size, surface morphology, drug content and encapsulation efficiency of the microspheres produced were evaluated. The stability of the formulation was assessed after 90 days at -20ºC. An in vitro release study was performed in PBS. In vitro cytotoxicity of the formulation was studied using hepatic cell line. The freeze-dried microspheres had mean particle size, IFN-alpha content, and encapsulation efficiency of 38.52 ± 4.64 µm, 15.52 ± 3.28% and 83.93 ± 5.76%, respectively. There were no significant changes during storage and the structural integrity of the protein was not compromised by the preparation technique. A total of 82% of the IFN-alpha was released after 28 days and the developed microspheres did not present cytotoxicity to the hepatic cell line. In vivo studies are currently underway to evaluate the biological activity of IFN-alpha encapsulated into microspheres.

Novel preparation techniques for alginate-poloxamer microparticles controlling protein release on mucosal surfaces

The objective of this study was to develop novel preparation techniques for protein-loaded, controlled release alginate-poloxamer microparticles with a size range suitable for pulmonary administration. Bovine serum albumin (BSA)-loaded microparticles were prepared by spray-drying aqueous polymer-drug solutions, followed by cross-linking the particles in aqueous or ethanolic CaCl(2) or aqueous ZnSO(4) solutions. The microparticles were characterized with respect to their morphology (optical and scanning electron microscopy), particle size (laser light diffraction), calcium content (atom absorption spectroscopy), alginate content (complexation with 1,9-dimethyl methylene blue) and in vitro drug release (modified Franz diffusion cell). The spray-dried microparticles were spherical in shape with a size range of 4-6μm. Aqueous cross-linking led to a significant size increase (10-15μm), whereas ethanolic cross-linking did not. The substantial drug loss (∼50%) during aqueous CaCl(2) cross-linking could be avoided by using aqueous ZnSO(4) or ethanolic CaCl(2) solutions. Protein release from microparticles cross-linked with ethanolic CaCl(2) solutions was much faster than in the case of aqueous CaCl(2) solutions, probably due to the lower calcium content. The salt concentration and temperature of the cross-linking solutions also affected the composition of and drug release from the microparticles. Cross-linked alginate-poloxamer microparticles can be produced in a size range appropriate for deep lung delivery and with controlled protein release kinetics (time frame: hours to days) with these novel preparation techniques. The systems offer an interesting potential for the controlled mucosal delivery of protein drugs.

Stability of seasonal influenza vaccines investigated by spectroscopy and microscopy methods

The stability of different seasonal influenza vaccines was investigated by spectroscopy and microscopy methods before and after the following stress-conditions: (i) 2 and 4 weeks storage at 25°C, (ii) 1 day storage at 37°C and (iii) one freeze-thaw cycle. The subunit vaccine Influvac (Solvay Pharma) and the split vaccine Mutagrip (Sanofi Pasteur) were affected by all stresses. The split vaccine Fluarix (GlaxoSmithKline) was affected only by storage at 25°C. The virosomal vaccine Inflexal V (Berna Biotech) was stable after the temperature stresses but aggregated after one freeze-thaw cycle. This study provides new insights into commercial vaccines of low antigen concentration and highlights the importance of using multiple techniques to assess vaccine stability.

Multivesicular liposome (MVL) sustained delivery of a novel synthetic cationic GnRH antagonist for prostate cancer treatment

Objectives

Multivesicular liposomes (MVLs) are often used as an appropriate carrier for delivering peptides due to high drug loading, relative stability and extended-release behaviour. However, when cationic amphipathic peptides are involved, some challenges may be encountered, including instability of multiple emulsions due to interaction between peptides and lipid membranes (electrostatic and hydrophobic interaction). LXT-101, a cationic amphipathic peptide, is a novel antagonist of gonadotropin-releasing hormone (GnRH) for prostate cancer treatment. The purpose of the current research was to explore simple methods of determining the interaction between peptide and lipid bilayer and to prepare MVLs of LXT-101 (DepoLXT-101) by the modified DepoFoam technique.

Methods

The anionic surfactants were added in the process of DepoLXT-101 preparation in order to minimize the effect of instability resulting from cationic peptides.

Key findings

DepoLXT-101 was obtained with good efficiency and reproduction. The integrity of encapsulated peptide was maintained as shown by RP-HPLC. DepoLXT-101 particles were characterized by morphology and particle size distribution and in-vitro release was also investigated. The release behaviour in vitro in medium of sodium chloride at 37°C showed that 70–90% of LXT-101 was released slowly from MVLparticles over 11 days. According to the fitting results of Ritgar-Pepps model, the in-vitro release of DepoLXT-101 was mainly governed by Fick's diffusion.

Conclusions

The data obtained from in-vivo study indicated that a sustained anticancer effect can be achieved over a 7-day period with subcutaneous administration of DepoLXT-101 in rats.

Encapsulation of Protein-Polysaccharide HIP Complex in Polymeric Nanoparticles

The objective of the present study is to formulate and characterize a nanoparticulate-based formulation of a macromolecule in a hydrophobic ion pairing (HIP) complex form. So far, HIP complexation approach has been studied only for proteins with molecular weight of 10–20 kDa. Hence, we have selected bovine serum albumin (BSA) having higher molecular weight (66.3 kDa) as a model protein and dextran sulphate (DS) as a complexing polymer to generate HIP complex. We have prepared and optimized the HIP complex formation process of BSA with DS. Ionic interactions between basic amino acids of BSA with sulphate groups of DS were confirmed by FTIR analysis. Further, nanoparticles were prepared and characterized with respect to size and surface morphology. We observed significant entrapment of BSA in nanoparticles prepared with minimal amounts of PLGA polymer. Finally, results of circular dichroism and intrinsic fluorescence assay have clearly indicated that HIP complexation and method of nanoparticle preparation did not alter the secondary and tertiary structures of BSA.

Development of interferon alpha-2b microspheres with constant release

Interferon alpha-2b (IFNα-2b) is an important immune regulator used widely in clinic. However, frequent subcutaneous injection and substantial toxicity decrease patients' compliance. So, drug delivery with more precisely controlled drug release is urgent for IFNα-2b. Microsphere is a promising sustained drug delivery system, which has been studied widely for delivery of proteins. However, it was found difficult to keep proteins' activity and guarantee complete release. In this study, we solidified IFNα-2b as microparticles firstly by co-lyophilizing it with gelatin and ZnSO(4). Microspheres were then prepared. The preparing procedure and formulation were optimized with encapsulation efficiency and in vitro release as main parameters. Finally, the microspheres were prepared by S/O/W method with microparticle size about 5 μm and PEGT/PBT-PLGA (9:1, w/w) as matrix material. The diameter of microspheres was 28.94 μm, the encapsulation efficiency was 86.01%, the burst release was 16.69%, the cumulative release was 83.06% at 23th day, and IFNα-2b was released from microspheres with a zero-order profile. These microspheres also demonstrated sustained and steady release for about 13 days in rats. In conclusion, the procedure and formulation used in this study were supposed to be successful to keep IFNα-2b active and released constantly and completely.

Mucosal delivery of liposome-chitosan nanoparticle complexes

Designing adequate drug carriers has long been a major challenge for those working in drug delivery. Since drug delivery strategies have evolved for mucosal delivery as the outstanding alternative to parenteral administration, many new drug delivery systems have been developed which evidence promising properties to address specific issues. Colloidal carriers, such as nanoparticles and liposomes, have been referred to as the most valuable approaches, but still have some limitations that can become more inconvenient as a function of the specific characteristics of administration routes. To overcome these limitations, we developed a new drug delivery system that results from the combination of chitosan nanoparticles and liposomes, in an approach of combining their advantages, while avoiding their individual limitations. These lipid/chitosan nanoparticle complexes are, thus, expected to protect the encapsulated drug from harsh environmental conditions, while concomitantly providing its controlled release. To prepare these assemblies, two different strategies have been applied: one focusing on the simple hydration of a previously formed dry lipid film with a suspension of chitosan nanoparticles, and the other relying on the lyophilization of both basic structures (nanoparticles and liposomes) with a subsequent step of hydration with water. The developed systems are able to provide a controlled release of the encapsulated model peptide, insulin, evidencing release profiles that are dependent on their lipid composition. Moreover, satisfactory in vivo results have been obtained, confirming the potential of these newly developed drug delivery systems as drug carriers through distinct mucosal routes.

Polymer-based sustained-release dosage forms for protein drugs, challenges, and recent advances

While the concept of using polymer-based sustained-release delivery systems to maintain therapeutic concentration of protein drugs for extended periods of time has been well accepted for decades, there has not been a single product in this category successfully commercialized to date despite clinical and market demands. To achieve successful systems, technical difficulties ranging from protein denaturing during formulation process and the course of prolonged in vivo release, burst release, and incomplete release, to low encapsulation efficiency and formulation complexity have to be simultaneously resolved. Based on this updated understanding, formulation strategies attempting to address these aspects comprehensively were reported in recent years. This review article (with 134 citations) aims to summarize recent studies addressing the issues above, especially those targeting practical industrial solutions. Formulation strategies representative of three areas, microsphere technology using degradable hydrophobic polymers, microspheres made of water soluble polymers, and hydrophilic in vivo gelling systems will be selected and introduced. To better understand the observations and conclusions from different studies for different systems and proteins, physicochemical basis of the technical challenges and the pros and cons of the corresponding formulation methods will be discussed.

Repair effect of diabetic ulcers with recombinant human epidermal growth factor loaded by sustained-release microspheres

In this study the w/o/w extraction-evaporation technique was adopted to prepare poly(lactic-co-glycolic acid) (PLGA) microspheres loading recombinant human epidermal growth factor (rhEGF). The microspheres were characterized for morphology by transmission electron microscopy (TEM) and particle size distribution. The release performances, the proliferation effects and therapeutic effects of rhEGF-loaded PLGA microspheres were all studied. The results showed that these spherical microspheres had a narrow size distribution and a high drug encapsulation efficiency (85.6%). RhEGF-loaded microspheres enhanced the growth rate of fibroblasts and wound healing more efficiently than pure rhEGF. The number of the proliferating cell nuclear antigen (PCNA) in the epidermis layer with the microsphere treatment was significantly larger than those of the control groups. Overall locally sustained delivery of rhEGF from biodegradable PLGA microspheres may serve as a novel therapeutic strategy for diabetic ulcer repair.

Development of protein delivery microsphere system by a novel S/O/O/W multi-emulsion

A novel method has been developed to protect protein drugs in poly (lactic-co-glycolic acid) (PLGA) microspheres using S/O/O/W multi-emulsion method. This method develops a novel protein drug sustained-release system, which is based on the combination of protein-loaded dextran glassy microparticles (protein-loaded AqueSpheres) and PLGA microspheres. The protein molecules are encapsulated in the dextran glassy particles and the drug-containing dextran glassy particles are further dispersed in the PLGA microspheres. The protein-loaded AqueSpheres based PLGA composite microspheres have spherical shape and a smooth surface. They possess a normal size distribution and a mean diameter of 67.08 microm. The method may decrease protein aggregations and incomplete release due to avoiding protein contacting with oil/water interfaces and hydrophobic PLGA. The dextran glassy particles can stabilize proteins in the PLGA matrix, which is the major advantage of this novel protein sustained-release system over preparation for the PLGA microspheres using W/O/W double-emulsion method.

Effect of particle size and charge on the network properties of microsphere-based hydrogels

This work describes the tailorability of the network properties of self-assembling hydrogels, based on ionic crosslinking between dextran microspheres. Copolymerization of hydroxyethyl methacrylate-derivatized dextran (dex-HEMA), emulsified in an aqueous poly(ethylene glycol) (PEG) solution, with methacrylic acid (MAA) or dimethylaminoethyl methacrylate (DMAEMA) resulted in negatively or positively charged microspheres, respectively, at physiological pH. The monomer/HEMA ratio ranged between 6 and 57, resulting in microspheres with zeta (zeta)-potentials from -6 to -34mV and +3 to +23mV, for the monomers MAA and DMAEMA, respectively. By altering the emulsification procedure, microsphere batches with various sizes and size distributions were obtained. The aim of the research was to assess the effect of particle size (distribution) and charge on the network properties of the macroscopic hydrogels. The ability to tailor the mechanical properties such as strength and elasticity increases the potential of the hydrogels to be used in a variety of pharmaceutical applications. Additionally, the injectability of these self-assembling hydrogels was investigated. Injectability is an important feature of drug delivery systems, since it allows avoiding surgery. Rheological analysis showed that an increasing surface charge of the microspheres led to stronger hydrogels. Relatively small microspheres (7microm) with a narrow size distribution (99% smaller than 14microm) gave rise to stronger hydrogels when compared to larger microspheres of 20microm with a broad distribution (99% smaller than 50microm). When small microspheres were combined with large microspheres of opposite charge, it was found that the strongest gels were obtained with 75% small and 25% large microspheres, instead of equal amounts (50/50) of positively and negatively charged microspheres. Computer modeling confirmed these findings and showed that the most favorable composition, related to the lowest potential energy, comprised of 75% small microspheres. Taking both charge and size effects into account, the storage moduli (G') of the almost fully elastic hydrogels could be tailored from 400 to 30,000Pa. Injectability tests showed that hydrogels (G' up to 4000Pa) composed of equal amounts of oppositely charged microspheres (-7 and +6mV, average particle size 7microm) could be injected through 25G needles using a static load of 15N, an ISO accepted value. In conclusion, a variety of options to control the network properties of macroscopic hydrogels are provided, related to the charge and particle size of the composing dextran microspheres. Furthermore, it is shown that the hydrogels are injectable, making them attractive candidates for a diversity of pharmaceutical applications.

Advances in lipid nanodispersions for parenteral drug delivery and targeting

Parenteral formulations, particularly intravascular ones, offer a unique opportunity for direct access to the bloodstream and rapid onset of drug action as well as targeting to specific organ and tissue sites. Triglyceride emulsions, liposomes and micellar solutions have been traditionally used to accomplish these tasks and there are several products on the market using these lipid formulations. The broader application of these lipid systems in parenteral drug delivery, however, particularly with new chemical entities, has been limited due primarily to the following reasons: a) only a small number of parenteral lipid excipients are approved, b) there is increasing number of drugs that are partially or not soluble in conventional oils and other lipid solvents, and c) the ongoing requirement for site-specific targeting and controlled drug release. Thus, there is growing need to expand the array of targetable lipid-based systems to deliver a wide variety of drugs and produce stable formulations which can be easily manufactured in a sterile form, are cost-effective and at least as safe and efficacious as the earlier developed systems. These advanced parenteral lipid-based systems are at various stages of preclinical and clinical development which include nanoemulsions, nanosuspensions and polymeric phospholipid micelles. This review article will showcase these parenteral lipid nanosystems and discuss advances in relation to formulation development, processing and manufacturing, and stability assessment. Factors controlling drug encapsulation and release and in vivo biodistribution will be emphasized along with in vitro/in vivo toxicity and efficacy case studies. Emerging lipid excipients and increasing applications of injectable lipid nanocarriers in cancer chemotherapy and other disease indications will be highlighted and in vitro/in vivo case studies will be presented. As these new parenteral lipid systems advance through the clinic and product launch, their therapeutic utility and value will certainly expand.

Fluorescence correlation spectroscopy at the oil-water interface: hard disk diffusion behavior in dilute beta-lactoglobulin layers precedes monolayer formation

We have performed a thorough characterization of fluorescence correlations spectroscopy (FCS) applied to oil-water interfaces of viscous oil droplets in aqueous solution, including numerical wave-optical calculations of the detection geometry and regularized multicomponent analysis of sample data. It is shown how significant errors in the estimation of the surface concentration can be avoided when FCS is applied to an interface region. We present data on the adsorption dynamics of beta-lactoglobulin (BLG), a well-studied model system. It is found that electrostatic repulsion slows the adsorption process and reduces the initial saturation density far below the monolayer concentration. During the first stages of adsorption, the diffusion coefficients of adsorbed protein closely follow the 2D hard disk model of Lahtinen et al.1 in response to increased surface concentration, which suggests that protein-protein interactions are limited to long-range Coulombic interactions at this stage.