Preparation and evaluation of poly(L-lactic acid) microspheres containing rhEGF for chronic gastric ulcer healing

Nanomaterials for application in wound Healing: current state-of-the-art and future perspectives

Nanoparticles are the gateway to the new era in drug delivery of biocompatible agents. Several products have emerged from nanomaterials in quest of developing practical wound healing dressings that are nonantigenic, antishear stress, and gas-exchange permeable. Numerous studies have isolated and characterised various wound healing nanomaterials and nanoproducts. The electrospinning of natural and synthetic materials produces fine products that can be mixed with other wound healing medications and herbs. Various produced nanomaterials are highly influential in wound healing experimental models and can be used commercially as well. This article reviewed the current state-of-the-art and briefly specified the future concerns regarding the different systems of nanomaterials in wound healing (i.e., inorganic nanomaterials, organic and hybrid nanomaterials, and nanofibers). This review may be a comprehensive guidance to help health care professionals identify the proper wound healing materials to avoid the usual wound complications.

Tunable Volumetric Density and Porous Structure of Spherical Poly-ε-caprolactone Microcarriers, as Applied in Human Mesenchymal Stem Cell Expansion

Polymeric microspheres may serve as microcarrier (MC) matrices, for the expansion of anchorage-dependent stem cells. They require surface properties that promote both initial cell adhesion and the subsequent spreading of cells, which is a prerequisite for successful expansion. When implemented in a three-dimensional culture environment, under agitation, their suspension under low shear rates depends on the MCs having a modest negative buoyancy, with a density of 1.02-1.05 g/cm³. Bioresorbable poly-ε-caprolactone (PCL), with a density of 1.14 g/cm³, requires a reduction in volumetric density, for the microspheres to achieve high cell viability and yields. Uniform-sized droplets, from solutions of PCL dissolved in dichloromethane (DCM), were generated by coaxial microfluidic geometry. Subsequent exposure to ethanol rapidly extracted the DCM solvent, solidifying the droplets and yielding monodisperse microspheres with a porous structure, which was demonstrated to have tunable porosity and a hollow inner core. The variation in process parameters, including the molecular weight of PCL, its concentration in DCM, and the ethanol concentration, served to effectively alter the diffusion flux between ethanol and DCM, resulting in a broad spectrum of volumetric densities of 1.04-1.11 g/cm³. The solidified microspheres are generally covered by a smooth thin skin, which provides a uniform cell culture surface and masks their internal porous structure. When coated with a cationic polyelectrolyte and extracellular matrix protein, monodisperse microspheres with a diameter of approximately 150 μm and densities ranging from 1.05-1.11 g/cm³ are capable of supporting the expansion of human mesenchymal stem cells (hMSCs). Validation of hMSC expansion was carried out with a positive control of commercial Cytodex 3 MCs and a negative control of uncoated low-density PCL MCs. Static culture conditions generated more than 70% cell attachment and similar yields of sixfold cell expansion on all coated MCs, with poor cell attachment and growth on the negative control. Under agitation, coated porous microspheres, with a low density of 1.05 g/cm³, achieved robust cell attachment and resulted in high cell yields of ninefold cell expansion, comparable with those generated by commercial Cytodex 3 MCs.

Design of experiments for microencapsulation applications: A review

Microencapsulation techniques have been intensively explored by many research sectors such as pharmaceutical and food industries. Microencapsulation allows to protect the active ingredient from the external environment, mask undesired flavours, a possible controlled release of compounds among others. The purpose of this review is to provide a background of design of experiments in microencapsulation research context. Optimization processes are required for an accurate research in these fields and therefore, the right implementation of micro-sized techniques at industrial scale. This article critically reviews the use of the response surface methodologies in pharmaceutical and food microencapsulation research areas. A survey of optimization procedures in the literature, in the last few years is also presented.

Biomaterials and Nanotherapeutics for Enhancing Skin Wound Healing

Wound healing is an intricate process that requires complex coordination between many cell types and an appropriate extracellular microenvironment. Chronic wounds often suffer from high protease activity, persistent infection, excess inflammation, and hypoxia. While there has been intense investigation to find new methods to improve cutaneous wound care, the management of chronic wounds, burns, and skin wound infection remain challenging clinical problems. Ideally, advanced wound dressings can provide enhanced healing and bridge the gaps in the healing processes that prevent chronic wounds from healing. These technologies have great potential for improving outcomes in patients with poorly healing wounds but face significant barriers in addressing the heterogeneity and clinical complexity of chronic or severe wounds. Active wound dressings aim to enhance the natural healing process and work to counter many aspects that plague poorly healing wounds, including excessive inflammation, ischemia, scarring, and wound infection. This review paper discusses recent advances in the development of biomaterials and nanoparticle therapeutics to enhance wound healing. In particular, this review focuses on the novel cutaneous wound treatments that have undergone significant preclinical development or are currently used in clinical practice.

Nanotechnology for protein delivery: Overview and perspectives

Protein-based therapeutics have made a significant impact in the treatment of a variety of important human diseases. However, given their intrinsically vulnerable structure and susceptibility to enzymatic degradation, many therapeutic proteins such as enzymes, growth factors, hormones, and cytokines suffer from poor physicochemical/biological stability and immunogenicity that may limit their potential benefits, and in some cases limit their utility. Furthermore, when protein therapeutics are developed for intracellular targets, their internalization and biological activity may be limited by inefficient membrane permeability and/or endosomal escape. Development of effective protein delivery strategies is therefore essential to further enhance therapeutic outcomes to enable widespread medical applications. This review discusses the advantages and limitations of marketed and developmental-stage protein delivery strategies, and provides a focused overview of recent advances in nanotechnology platforms for the systemic delivery of therapeutic proteins. In addition, we also highlight nanoparticle-mediated non-invasive administration approaches (e.g., oral, nasal, pulmonary, and transdermal routes) for protein delivery.

Administration strategies for proteins and peptides

Proteins are a vital constituent of the body as they perform many of its major physiological and biological processes. Recently, proteins and peptides have attracted much attention as potential treatments for various dangerous and traditionally incurable diseases such as cancer, AIDS, dwarfism and autoimmune disorders. Furthermore, proteins could be used for diagnostics. At present, most therapeutic proteins are administered via parenteral routes that have many drawbacks, for example, they are painful, expensive and may cause toxicity. Finding more effective, easier and safer alternative routes for administering proteins and peptides is the key to therapeutic and commercial success. In this context, much research has been focused on non-invasive routes such as nasal, pulmonary, oral, ocular, and rectal for administering proteins and peptides. Unfortunately, the widespread use of proteins and peptides as drugs is still faced by many obstacles such as low bioavailability, short half-life in the blood stream, in vivo instability and numerous other problems. In order to overcome these hurdled and improve protein/peptide drug efficacy, various strategies have been developed such as permeability enhancement, enzyme inhibition, protein structure modification and protection by encapsulation. This review provides a detailed description of all the previous points in order to highlight the importance and potential of proteins and peptides as drugs.

Long-term delivery of protein therapeutics

INTRODUCTION

Proteins are effective biotherapeutics with applications in diverse ailments. Despite being specific and potent, their full clinical potential has not yet been realized. This can be attributed to short half-lives, complex structures, poor in vivo stability, low permeability, frequent parenteral administrations and poor adherence to treatment in chronic diseases. A sustained release system, providing controlled release of proteins, may overcome many of these limitations.

AREAS COVERED

This review focuses on recent development in approaches, especially polymer-based formulations, which can provide therapeutic levels of proteins over extended periods. Advances in particulate, gel-based formulations and novel approaches for extended protein delivery are discussed. Emphasis is placed on dosage form, method of preparation, mechanism of release and stability of biotherapeutics.

EXPERT OPINION

Substantial advancements have been made in the field of extended protein delivery via various polymer-based formulations over last decade despite the unique delivery-related challenges posed by protein biologics. A number of injectable sustained-release formulations have reached market. However, therapeutic application of proteins is still hampered by delivery-related issues. A large number of protein molecules are under clinical trials, and hence, there is an urgent need to develop new methods to deliver these highly potent biologics.

IL-1Ra and its delivery strategies: inserting the association in perspective

Interleukin-1 receptor antagonist (IL-1Ra) is a naturally occurring anti-inflammatory antagonist of interleukin-1 family of pro-inflammatory cytokines. The broad spectrum anti-inflammatory effects of IL-1Ra have been investigated against various auto-immune diseases such as diabetes mellitus, rheumatoid arthritis. Despite of its outstanding broad spectrum anti-inflammatory effects, IL-1Ra has short biological half-life (4-6 h) and to cope with this problem, up till now, many delivery strategies have been applied either to extend the half-life and/or prolong the steady-state sustained release of IL-1Ra from its target site. Here in our present paper, we have provided an overview of all approaches attempted to prolong the duration of therapeutic effects of IL-1Ra either by fusing IL-1Ra using fusion protein technology to extend the half-life and/or development of new dosage forms using various biodegradable polymers to prolong its steady-state sustained release at the site of administration. These approaches have been characterized by their intended impact on either in vitro release characteristics and/or pharmacokinetic and pharmacodynamic parameters of IL-1Ra. We have also compared these delivery strategies with each other on the basis of bioactivity of IL-1Ra after fusion with fusion protein partner and/or encapsulation with biodegradable polymer.

Exploration of statistical experimental design to improve entrapment efficiency of acyclovir in poly (d, l) lactide nanoparticles

OBJECTIVE

In current exploration, systematic attempts have been made to improve the entrapment efficiency of a model hydrophilic drug substance, i.e. acyclovir, in poly (d, l) lactide (PLA) nanoparticles (NPs) using a modified nanoprecipitation technique.

METHODS

Formulation parameters such as drug to polymer ratio, antisolvent selection, electrolyte (NaCl) addition, pH alteration and temperature were screened to improve the entrapment efficiency of acyclovir in PLA NPs. The temperature of the system (0-5 °C), phase volume ratio (1:2), stirring speed (2000 rpm), sonication time (5 min), etc. were kept constant during the preparation of NPs. Drug to polymer ratio and electrolyte addition emerged as critical formulation parameters affecting particle size as well as entrapment efficiency. Hence, in the present investigation a 3(2) full factorial design was used to investigate the combined influence of two factors, i.e. drug to polymer ratio (X1) and the amount of electrolyte, i.e. NaCl (X2) on particle size (Y1) and entrapment efficiency (Y2). The NPs were also evaluated for drug-excipient compatibility study by employing DSC and FT-IR analysis, whereas in vitro drug release studies were performed using dialysis bag technique in phosphate buffer pH 7.4.

RESULTS

Statistically significant models were evolved to predict entrapment efficiency and particle size. The effect of factors X1, X2 and [Formula: see text] was found to be statistically significant in nature. Response variables, i.e. entrapment efficiency and particle size, were simultaneously optimized using desirability function using Design Expert software. This process allowed the selection of most suitable level of factors to achieve desired level of particle size and entrapment efficiency. The results of multiple linear regression analysis revealed that for obtaining desirable particle size (less than 250 nm) and entrapment efficiency (more than 17%), the NPs should be prepared using 1:3 drug to polymer ratio and 0.04 M NaCl. Acyclovir was found to be compatible with PLA as indicated by DSC and FT-IR studies. The experimental values obtained from the optimized formulation highly agreed with the predicted values. The drug release from the optimized formulation exhibited biphasic pattern and the drug release kinetics was best explained by Weibull model.

CONCLUSION

In conclusion, results of the present study demonstrated that PLA NPs with expected particle size and entrapment efficiency can be obtained by adopting the concept of quality by design.

Controlling the stability and size of double-emulsion-templated poly(lactic-co-glycolic) acid microcapsules

The stability and size of poly(lactic-co-glycolic)acid (PLGA)-containing double emulsions and the resulting PLGA microcapsules are controlled by varying the composition of highly monodisperse water-in-oil-in-water (W/O/W) double emulsions. We propose that the basic inner phase of W/O/W double emulsions catalyzes the hydrolysis of PLGA and the ionization of carboxylic acid end groups, which enhances the surface activity of PLGA and facilitates the stabilization of the double emulsions. The size of PLGA-containing double emulsions and that of resulting microcapsules can be readily tuned by osmotic annealing, which depends on the concentration ratio of a solute in the inner and outer phases of double emulsions. The internal volume of PLGA microcapsules can be changed by more than 3 orders of magnitude using this method. This approach also overcomes the difficulty in generating monodisperse double emulsions and microcapsules over a wide range of dimensions using a single microfluidic device. The osmotic annealing method can also be used to concentrate encapsulated species such as colloidal suspensions and biomacromolecules.

Prospects of pharmaceuticals and biopharmaceuticals loaded microparticles prepared by double emulsion technique for controlled delivery

Several methods and techniques are potentially useful for the preparation of microparticles in the field of controlled drug delivery. The type and the size of the microparticles, the entrapment, release characteristics and stability of drug in microparticles in the formulations are dependent on the method used. One of the most common methods of preparing microparticles is the single emulsion technique. Poorly soluble, lipophilic drugs are successfully retained within the microparticles prepared by this method. However, the encapsulation of highly water soluble compounds including protein and peptides presents formidable challenges to the researchers. The successful encapsulation of such compounds requires high drug loading in the microparticles, prevention of protein and peptide degradation by the encapsulation method involved and predictable release, both rate and extent, of the drug compound from the microparticles. The above mentioned problems can be overcome by using the double emulsion technique, alternatively called as multiple emulsion technique. Aiming to achieve this various techniques have been examined to prepare stable formulations utilizing w/o/w, s/o/w, w/o/o, and s/o/o type double emulsion methods. This article reviews the current state of the art in double emulsion based technologies for the preparation of microparticles including the investigation of various classes of substances that are pharmaceutically and biopharmaceutically active.

Nanoscale particle therapies for wounds and ulcers

‘Small is beautiful’ – this should be the slogan of nanoscientists. Indeed, working with particles less than 100 nm in size, nanotechnology is on the verge of providing a host of new materials and approaches, revolutionizing applied medicine. The obvious potential of nanotechnology has attracted considerable investment from governments and industry hoping to drive its economic development. Several areas of medical care already benefit from the advantages that nanotechnology provides and its application in wound healing will be reviewed in this article.

Delivery of therapeutic proteins

The safety and efficacy of protein therapeutics are limited by three interrelated pharmaceutical issues, in vitro and in vivo instability, immunogenicity and shorter half-lives. Novel drug modifications for overcoming these issues are under investigation and include covalent attachment of poly(ethylene glycol) (PEG), polysialic acid, or glycolic acid, as well as developing new formulations containing nanoparticulate or colloidal systems (e.g., liposomes, polymeric microspheres, polymeric nanoparticles). Such strategies have the potential to develop as next generation protein therapeutics. This review includes a general discussion on these delivery approaches.

Preparation and characterization of quercetin-loaded polymethyl methacrylate microcapsules using a polyol-in-oil-in-polyol emulsion solvent evaporation method

Flavonoids and related compounds exhibit a wide range of useful pharmacological properties but present challenges related to their stability and solubility in commonly available solvents. In this study, polymethyl methacrylate (PMMA) microcapsules were prepared using a novel polyol-in-oil-in-polyol (P/O/P) emulsion solvent evaporation method as a means of stabilizing the flavonoids, using quercetin as a model flavonoid drug. The morphology of the microcapsules was evaluated using a scanning electron microscope, revealing a spherical shape with a smooth surface. The cross-section image of the PMMA microcapsules prepared with an amphiphilic polymer in the inner polyol phase showed that the microcapsule was filled with several submicron microspheres. The mean diameter varied from 1.03 ± 0.12 μm to 2.39 ± 0.42 μm, and the encapsulation efficiency ranged from 12.7% to 26.9%. When free quercetin was stored at 42°C, the residual quercetin content gradually decreased to 18% over 28 days as a result of oxidation. However, when encapsulated in PMMA microcapsules with an amphiphilic polymer in the inner polyol phase, the residual quercetin content decreased to just 82%. In-vitro release studies indicated a sustained release pattern throughout the 36-h study. The release kinetics of the microcapsules with an amphiphilic polymer followed a diffusion-controlled mechanism and the microcapsule without amphiphilic polymer followed an anomalous diffusion behaviour. This study suggests that the novel P/O/P emulsion solvent evaporation method can be applied to the encapsulation of flavonoids.

Nanoparticulate systems for growth factor delivery

The field of nanotechnology, which aims to control and utilize matter generally in 1-100 nm range, has been at the forefront of pharmaceutical development. Nanoparticulate delivery systems, with their potential to control drug release profiles, prolonging the presence of drugs in circulation, and to target drugs to a specific site, hold tremendous promise as delivery strategies for therapeutics. Growth factors are endogenous polypeptides that initiate intracellular signals to regulate cellular activities, such as proliferation, migration and differentiation. With improved understanding of their roles in physiopathology and expansion of their availability through recombinant technologies, growth factors are becoming leading therapeutic candidates for tissue engineering approaches. However, the outcome of growth factor therapeutics largely depends on the mode of their delivery due to their rapid degradation in vivo, and non-specific distribution after systemic administration. In order to overcome these impediments, nanoparticulate delivery systems are being harnessed for spatiotemporal controlled delivery of growth factors. This review presents recent advances and some disadvantages of various nanoparticulate systems designed for effective intact growth factor delivery. The therapeutic applications of growth factors delivered by such systems are reviewed, especially for bone, skin and nerve regeneration as well as angiogenesis. Finally, future challenges and directions in the field are presented in addition to the current limitations.

Effect of Molecular Size of PEGylated Recombinant Human Epidermal Growth Factor on the Biological Activity and Stability in Rat Wound Tissue

The purpose of this study was to investigate the effect of size of polyethylene glycol (PEG) conjugated to recombinant human epidermal growth factor (rhEGF) on its stability in skin wound tissue and in vitro biological activity to find the desirable conjugate as topical therapeutic agent for wound healing. Site-specific PEGylation at N-terminus of rhEGF was performed with monomethoxy PEG-Butyraldehyde derivatives (MW 2, 5, and 20 kDa). Mono-PEG-rhEGFs retained 60-70% of biological activity of native rhEGF, and the effect of PEG size was not significant. The improvement of stability in the rat skin wound tissue was dependent on the increase of the PEG size attached. The degradation half-lives of native rhEGF, mono-PEG-2K-, -5K-, and -20K-rhEGFs were 1.1, 3.1, 5.2, and 41.5 hr, respectively. Therefore, mono-PEG-20K-rhEGF was considered to be the most desirable in terms of the increase of stability and the preservation of biological activity. This study suggests that the high molecular weight PEG at N-terminus of rhEGF would give a satisfactory stabilizing effect and thus may improve therapeutic efficacy in clinical use.

Effect of surfactant HLB and different formulation variables on the properties of poly-D,L-lactide microspheres of naltrexone prepared by double emulsion technique

The aim of this work was to investigate the role of HLB of emulsifier as well as volume of the internal aqueous phase (W(1)) and presence of salt in the external aqueous phase (W(2)) on the morphology, size and encapsulation efficiency of poly(D,L-lactide) microspheres containing naltrexone HCl. PLA microparticles containing naltrexone HCl, an effective opiate antagonist, were prepared by a water-in-oil-in-water emulsification-solvent evaporation procedure. One of the five different emulsifiers: span 80, span 20, tween 85, tween 80 and tween 20, with HLB values from 4-17 were added to W(1). Presence of emulsifier in W(1) resulted in smaller particles with a more dense and uniform internal structure. Incorporation of span 80 (HLB 4.3, suitable for W/O emulsions) yield the highest encapsulation efficiency. Increasing the HLB value to 8 or 11 (span 20 or tween 85) decreased the efficiency of naltrexone HCl-loading. HLB values higher than 15 (tween 80 or tween 20) increased encapsulation efficiency unexpectedly, which could be attributed to migration of these emulsifiers to the O/W(2) interface and modifying the surface properties of microparticles. Increasing the internal water phase volume from 0.2-1.8 ml resulted in larger particle size with poor encapsulation efficiency. Addition of 10% w/w NaCl to the W(2) changed the surface morphology of microspheres from a porous form to a smooth surface. It was shown that, by selecting the appropriate HLB value of emulsifier in W(1), addition of salt to W(2) and controlling the volume of W(1), one can control the encapsulation efficiency, size and morphology of microspheres.

Biodegradable microspheres of ketorolac tromethamine for parenteral administration

Ketorolac tromethamine loaded microspheres were prepared using two different polyesters, namely poly (lactic acid) and poly (glycolic acid) by solvent evaporation technique. The morphology of microspheres was analysed by scanning electron microscopy. In vitro release profiles of these microspheres were studied in phosphate buffered saline pH 7.4. The release kinetics of ketorolac tromethamine from the microspheres was evaluated by fitting the release data to the zero-order, Higuchi and korsemeyer-peppas equations. All microspheres showed initial burst release, followed by fickian diffusion of drug through microspheres. These microspheres were formulated as parenterals to have controlled release system.

Use of microparticulate systems to accelerate skin wound healing

Rapid and proper healing is important in the treatment of skin wounds. The dressing achieves the functions of the natural skin by protecting the wound area from the bulk loss of tissue and creating an effective barrier to outside contaminants without increasing the bacterial load on the wound surface. There are many wound dressings available on the market which can be used in the healing process. Different dressings have been used according to the condition of the wound and the phases of wound healing. Biodegradable polymers are being widely used in drug delivery and also in wound healing. These polymers that are applicable as a wound dressing protect the wound site against unwanted external effects, inhibit wound contraction, and, if possible, stimulate the healing process. Micro- and nanoparticulates are currently being evaluated as a potential drug delivery in clinical applications. Growth factors also play a vital role in wound healing. Polymers used in wound healing act as sustained release vehicles for growth factors. Controlled release of growth factors from microspheres has provided a higher degree of healing in the wound areas. This review is intended to provide information regarding the various formulations and microparticulate systems used in wound healing.

Bioengineering approaches to controlled protein delivery

Proteins are of crucial importance in all biologic organisms, in terms of both structure and function. Their deficits play central roles in many pathologic states, and their potential as powerful therapeutic agents has been widely recognized. Many issues, however, exist in delivery of biologically active proteins to target tissues and organs. Recent advances in biomedical engineering have lead to development of advanced techniques for controlled delivery of peptides and proteins, paving the way for their efficient use in treating human injury and disease. With a particular emphasis on most recent advances, this review discusses currently available techniques for controlled delivery of proteins and considers future research directions.

Improvement of a bovine serum albumin microencapsulation process by screening design

The first objective of this study was to prepare microspheres containing a model protein by double emulsion-solvent evaporation/extraction method. This method was modified to consider the fragile nature of proteins. These modifications related to the reduction of polymer loss, of agitation duration and of contact time between protein and solvent. The polymer used was poly(epsilon-caprolactone) and the model protein was bovine serum albumin. The control of the microsphere properties constituted a second objective of this project. A screening design methodology was used to evaluate the effects of the process and formulation variables on microsphere properties. Twelve operating factors were retained, and the particle properties considered were the mean size, the encapsulation efficiency, and the surface state. The statistical analysis of the results allowed determining the most influent factors. Considering the whole results, it appeared that the polymer concentration, the osmotic pressure equilibrium and the volume of the inner, outer and organic phases were the most important parameters. Following this screening study, it was possible to produce particles of small size with high entrapment efficiency (near to 80%) and smooth surface. A good batch to batch reproductibility was obtained.

Modulated release of bioactive protein from multilayered blended PLGA coatings

The objective of this study was to develop a poly(D,L-lactic-co-glycolic acid) (PLGA)-based coating system for producing biologically-inspired delivery profiles. Protein-loaded microspheres were made from PLGA (50:50) terminated with carboxylic acid groups (PLGA-2A) blended either with more hydrophobic PLGA (50:50) having lauryl ester endcaps (PLGA-LE) or with the more hydrophilic Pluronic F-127 (PF-127). Dense coatings were formed by pressure-sintering the microspheres. Altering hydrophobicity changed the water concentration within coatings, and consequently the time to onset of polymer degradation and protein release was modulated. After blending up to 8% Pluronic, degradation by-products began accumulating immediately upon incubation in saline, whereas, degradation was delayed for up to 14 days with blending of up to 30% PLGA-LE. Primary protein release peaks from one-layer coatings could be created from 7 to 20 days using 8% PF-127 or 30% PLGA-LE blends, respectively. Multilayered coatings of different blends generated several release peaks, with their temporal occurrence remaining approximately the same when layers of other hydrophobicity were added above or below. To allow design of coatings for future use, results were used to construct a model based on Fourier analysis. This polymer blend system and model can be used to mimic temporally varying profiles of protein expression.

Stabilization and encapsulation of a staphylokinase variant (K35R) into poly(lactic-co-glycolic acid) microspheres

The aim of this study is to prepare poly(lactic-co-glycolic acid) (PLGA) microspheres containing a staphylokinase variant K35R (DGR) with purpose of preserving the protein stability during both encapsulation and drug release. DGR-loaded microspheres are fabricated using a double-emulsion solvent extraction technique. Prior to encapsulation, the effect of ultrasonication emulsification of DGR solutions with methylene chloride on protein recovery was investigated. Moderate ultrasonic treatment of aqueous DGR/dichloromethane mixtures caused approximately 84% DGR aggregation. Polyvinyl alcohol (PVA) added into aqueous DGR solutions significantly improved DGR recovery to >90%. The effects of co-encapsulated PVA and NaCl in the external aqueous phase on the characteristics of the microspheres were investigated. When 2% PVA was co-encapsulated and 2.5% NaCl was added to the external water phase, DGR encapsulation efficiency was significantly increased from 7.1% to 78.1% and DGR was distributed uniformly throughout the microspheres. In vitro release test showed that DGR was released from PLGA microspheres in a sustained manner over 15 days. A large amount of released DGR was inactive in the absence of co-encapsulated PVA. On the contrary, when 2% PVA was co-encapsulated, the released DGR was almost completely intact within 9 days. In conclusion, PLGA microspheres can be an effective carrier for DGR and form a promising depot system.

Macrophage-colony stimulating factor enhances MHC-restricted presentation of exogenous antigen in dendritic cells

Previous studies have shown that dendritic cells (DCs) can phagocytize, process and present a microencapsulated form of ovalbumin (OVA) in the context of class I MHC as well as class II MHC. In the present study, we examined the effects of recombinant human macrophage-colony stimulating factor (M-CSF) on the MHC-restricted presentation of microencapsulated OVA by DCs. Two types of DCs were generated from mouse bone marrow (BM) cells, one type with granulocyte/macrophage-colony stimulating factor (GM-CSF) alone, the other type with GM-CSF and interleukin (IL)-4. Pretreatment with M-CSF significantly enhanced both class I MHC and class II MHC-restricted presentation of exogenous OVA by both types of DCs. The enhancing activity of M-CSF on antigen presentation was more potent in DCs generated with GM-CSF alone compared to DCs generated with both GM-CSF and IL-4. Pretreatment of the DCs with M-CSF did not increase phagocytic activity or total level of expression of class I MHC (H-2K(b)) molecules, but increased expression of OVA peptide-H-2K(b) complexes upon phagocytosis of microencapsulated OVA. These results demonstrate that M-CSF increases intracellular processing events of phagocytized antigen in DCs.

Identification of optimal molecular size of modified Aloe polysaccharides with maximum immunomodulatory activity

Polysaccharides isolated from the gel of Aloe species have been known to have diverse biological activities, including immunomodulatory and antitumor activities. The molecular size-immunomodulatory activity relationship of modified Aloe polysaccharide (MAP) was examined in this study. Crude MAP (G2E1) was prepared from the gel of Aloe vera that was partially digested with cellulase. Proteins in crude MAP were removed by passage through a DEAE-Sephacel column, and then the protein-free MAP (G2E1D) was further separated into three fractions, G2E1DS3 molecular weight (MW > or = 400 KDa), G2E1DS2 (5 KDa < or = MW < or = 400 KDa), G2E1DS1 (MW < or = 5 KDa), by Sephacryl column chromatography and ultrafiltration. Immunomodulatory activities of MAP preparations were examined on a mouse macrophage cell line, RAW 264.7 cells, and in ICR strain of mouse implanted with sarcoma 180 cells. We found that polysaccharides between 400 and 5 KDa exhibit the most potent macrophage-activating activity as determined by increased cytokine production, nitric oxide release, expression of surface molecules, and phagocytic activity. In accordance with the in vitro activity, polysaccharides between 400 and 5 KDa also exhibited the most potent antitumor activity in vivo.

Preparation of uniform-sized PLA microcapsules by combining Shirasu Porous Glass membrane emulsification technique and multiple emulsion-solvent evaporation method

Relatively Uniform-sized biodegradable poly(lactide) (PLA) microcapsules were successfully prepared by combining a Shirasu Porous Glass (SPG) membrane emulsification technique and multiple emulsion-solvent evaporation method. An aqueous phase containing lysozyme was used as the internal water phase (w1), and PLA and Arlacel 83 were dissolved in a mixture solvent of dichloromethane (DCM) and toluene which was used as the oil phase (o). These two solutions were emulsified by a homogenizer to form a w1/o primary emulsion. The primary emulsion was permeated through the uniform pores (5.25 microm) of an SPG membrane into the external water phase by the pressure of nitrogen gas to form the uniform w1/o/w2 droplets. Then, the solid polymer microcapsules were obtained by simply evaporating the solvent. It is necessary to avoid the phase separation of primary emulsion during the SPG membrane emulsification. It was found that when the density difference of the internal water phase and oil phase was reduced to nearly zero and Arlacel 83 was used as the oil emulsifier, the phase separation was not observed within 24 h. The w1/o/w2 emulsion with uniform diameter was obtained only when Arlaecl 83 concentration was limited below 2.5 wt.% based on oil phase. The drug encapsulation efficiency was found to be related to several factors including PLA molecular weight, additive type and its concentration in the internal water phase, the emulsifier type and concentration in the oil phase, the NaCl concentration and the pH value in the external water phase. Comparing with the stirring method, it was found that the size was more uniform and the drug encapsulation efficiency was much higher when the microcapsules were prepared by SPG membrane emulsification technique and the highest drug encapsulation efficiency of 92.20% was obtained. This is the first study to prepare PLA microcapsules by combining an SPG membrane emulsification technique and multiple emulsion-solvent evaporation method.

Cyclosporin A and tacrolimus, but not rapamycin, inhibit MHC-restricted antigen presentation pathways in dendritic cells

The main targets for the immunosuppressive calcineurin inhibitors, cyclosporin A (CsA) and tacrolimus, have been considered to be activated T cells, but not antigen-presenting cells. Here we demonstrate that CsA and tacrolimus, but not rapamycin, inhibit major histocompatibility complex (MHC)-restricted antigen presentation in dendritic cells (DCs). Microencapsulated ovalbumin (OVA) was efficiently captured, processed, and presented on both class I MHC molecules (cross-presentation) as well as on class II MHC molecules. Addition of CsA and tacrolimus, but not rapamycin, to cultures of DCs inhibited both the class I processing pathway and the class II processing pathway of exogenous OVA. In addition, CsA and tacrolimus, but not rapamycin, also inhibited the classic class I processing pathway of endogenous OVA. CsA and tacrolimus did not inhibit presentation of exogenously added OVA peptide, SIINFEKL, phagocytic activity of DCs, or the total level of expression of class I MHC (H-2Kb) molecules. CsA and tacrolimus, however, inhibited profoundly the expression of SIINFEKL-H-2Kb complexes in OVA-phagocytized DCs. These results demonstrate clearly that CsA and tacrolimus inhibit intracellular processing events of antigens, and further suggest that the immunosuppressive activity of CsA and tacrolimus is at least in part due to inhibition of antigen processing pathways.

A New Approach for Determining the Stability of Recombinant Human Epidermal Growth Factor by Thermal Fourier Transform Infrared (FTIR) Microspectroscopy

Based on Fourier transform infrared (FTIR) microspectroscopy, the conformation of rhEGF under the influence of pH, heat treatment, chaotropic salts, concentration of salt and protein structure perturbants was studied. The FTIR spectrum of rhEGF showed that major secondary structures from amide I bands composed of 40.6% beta-sheets, 25.0% reverse turns, 16.5% random coils, 13.0% loops and 4.9% side-chain structures. At extreme pH conditions (pH < 4 and pH > 8), there were changes in intensity of the bands attributed to loop (1658 cm(-1)) and random coil structures, and these bands shifted to lower wavenumbers, indicating changes in protein conformation. Thermal denaturation of rhEGF occurred at 40-76 degrees C and the formation of intermolecular beta-aggregates was revealed by the FTIR spectra. Thermal-irreversible property of rhEGF after second-heating treatment suggested that rhEGF has a poor thermal stability. While investigating the stability of rhEGF in the presence of chaotropic salts, anions induced protein unfolding of rhEGF more significantly than cations. The optimal stabilizing effect was found at the 2 M NaCl added to rhEGF, and expressed the structure of rhEGF more stable on the many components. The bands of loop structure (1654 cm(-1)), beta-sheet (1638 cm(-1)) and intermolecular antiparallel beta-aggregation formation (1694, 1619 and 1612 cm(-1)) seem to be "marked" to be more sensitive in determining environmental changes of rhEGF for FTIR microspectroscopy.

The healing effect of TGF-α on gastric ulcer induced by acetylsalicylic acid in rats

The present study was designed to investigate the effects of microemulsion and aqueous solution containing transforming growth factor alpha (TGF-alpha) and/or aprotinin administered intragastrically (i.g.) on healing of acute gastric ulcers induced by acetylsalicylic acid (ASA). The microemulsion was prepared by modification of the microemulsion formulation described in our previous study. Acute gastric lesions were induced by the application of ASA (150 mg/kg in 1.5 ml of 0.2N HCl i.g.). TGF-alpha in solution or microemulsion formulations were administered at a dose of 10 microg/kg per 24h i.g. for 2 days. The effects of TGF-alpha on the healing was evaluated with the measurement of ulcer score, basal gastric acid secretion, total protein content of gastric fluid, gastric mucus level and histological analysis. The results indicated that the highest decrease in ulcer area was observed in group treated with microemulsion containing TGF-alpha plus aprotinin (TA-ME). TGF-alpha in microemulsion formulation was more effective than TGF-alpha in solution formulation in the increase of gastric mucus secretion, in the decrease of gastric acid secretions and ulcer scores. Histological evaluation of the gastric mucosa samples revealed that, best recovery was obtained in the TA-ME treated group.

Improved entrapment efficiency of hydrophilic drug substance during nanoprecipitation of poly(l)lactide nanoparticles

The purpose of this research was to improve the entrapment efficiency of a model hydrophilic drug substance, sodium cromoglycate, loaded inside polylactic acid nanoparticles by a modified nanoprecipitation method. The effect of formulation parameters was studied to improve the entrapment efficiency of the drug substance inside the nanoparticles. Several parameters (changes in the amount of model drug, solvent selection, electrolyte addition, pH alteration) were tested in order to increase the loading of the hydrophilic drug in the hydrophobic nanoparticles. Lowering of the pH was the most efficient way to increase the drug loading; up to approximately 70% of the sodium cromoglycate used in the particle formation process could be loaded inside the particles. The loading efficiency without the pH change was around 10% to 15% at maximum. The crystallinity values and crystal habits of the sodium cromoglycate nanoparticles were studied (x-ray diffraction) before and after the lowering of the pH. The change in pH conditions during the nanoprecipitation process did not affect markedly the crystallinity properties of the drug substance. According to this study, it is possible to improve the entrapment efficiency of hydrophilic sodium cromoglycate inside of the nanoparticles by small changes in the process parameters without alterations in the physical properties of the original drug substance.

Biodegradable microspheres for protein delivery

In a very short time, since their emergence, the field of controlled delivery of proteins has grown immensely. Because of their relatively large size, they have low transdermal bioavailabilities. Oral bioavailability is generally poor since they are poorly absorbed and easily degraded by proteolytic enzymes in the gastrointestinal tract. Ocular and nasal delivery is also unfavorable due to degradation by enzymes present in eye tissues and nasal mucosa. Thus parenteral delivery is currently most demanding and suitable for delivery of such molecules. In systemic delivery of proteins, biodegradable microspheres as parenteral depot formulation occupy an important place because of several aspects like protection of sensitive proteins from degradation, prolonged or modified release, pulsatile release patterns. The main objective in developing controlled release protein injectables is avoidance of regular invasive doses which in turn provide patient compliance, comfort as well as control over blood levels. This review presents the outstanding contributions in field of biodegradable microspheres as protein delivery systems, their methods of preparation, drug release, stability, interaction with immune system and regulatory considerations.

N-terminal site-specific mono-PEGylation of epidermal growth factor

PURPOSE

N-terminal site-specific mono-PEGylation of recombinant human epidermal growth factor (EGF) was accomplished using polyethyleneglycol (PEG) derivatives (Mw = 2000 and 5000) through a reactive terminal aldehyde group.

METHODS

The site-specific PEG conjugation was conducted ata slightly acidic pH condition (pH 5.5). The mono-PEGylation was targeted to an alpha-amine group at the N-terminal end of EGF to minimize reduction of biologic activity. Tryptic digestion mapping and MALDI-TOF MS techniques were applied to show the occurrence of mono-PEGylation at the N-terminus of EGF.

RESULTS

The site-specific mono-PEGylated EGF, when compared with native EGF, fully retained its in vitro biologic activities such a cell proliferation and intracellular signal transduction. This revealed that although a synthetic polymer of a PEG was covalently conjugated to EGF, the internalized complex of PEGylated EGF-receptor within cells did not hamper the intracellular signal transduction events. The PEGylated EGF also exhibited a prolonged circulation in blood stream in vivo and markedly enhanced physical stability whe incubated with tissue homogenate.

CONCLUSION

N-terminally mono-PEGylated EGF shows increased physical stability while retaining its biologic activity.

Polyhydroxyalkanonate derivatives in current clinical applications and trials

Polyhydroxyalkanonate is a typical biodegradable material, which is permitted for use in the medical and pharmaceutical fields. For its biodegradability, biocompatibility, and toxicological safety, the majority of products practically used are composed of homo-polymers of poly(lactic acid), poly(glycolic acid), and poly(epsilon-caprolactone) and their co-polymers. On the market, suture strings are still the main usage. The needs of biodegradable materials have been being gradually increased by the development of drug delivery systems, tissue engineering, and regenerative medicine. Some types of formulation, that is, mono-fibers, twisted fibers, films, fabrics, sponges, and injectable particles are developed to match each purpose. This article reviews the current clinical applications and trials of polyhydroxyalcanonate products.

Effects of epidermal growth factor microemulsion formulation on the healing of stress-induced gastric ulcers in rats

The effects of intragastric (i.g.) administration of microemulsion formulation of epidermal growth factor (EGF) on the healing of acute gastric ulcers induced by cold-restraint stress in rats was studied and compared with intraperitoneal (i.p.) administration of solutions. In the microemulsion formulation (W/O), labrafil M 1944 CS was the oil phase. Arlacel 186 and Brij 35 were used as the surfactants. Absolute alcohol and distilled water were used as the co-surfactant and the aqueous phase, respectively. Acute gastric lesions were induced by cold-restraint stress for 4 h in the refrigerator (4.0+/-0.5 degrees C). EGF was administered at a dose of 6 microg/kg per day intraperitoneally and intraperitoneally for 7 days. Basal gastric acid secretion (microequiv. H+/30 min), ulcer score (mm(2)) and tissue mucus levels (microg/g tissue) were measured. Basal gastric secretion was significantly reduced after the administration of EGF microemulsion (ME+EGF) (P<0.05). There was no significant decrease in basal gastric acid secretion following i.p (IPEGF) and i.g (IG-EGF) of EGF administrations of solutions compared to their control groups (P>0.05). The results indicate that the highest reduction in the basal acid secretion was seen after the administration of a microemulsion of EGF formulation. The mean ulcer score was reduced by i.g treatment with the microemulsion dosage form of EGF in 7 days from 15.9+/-1.4 to 1.16+/-0.45 mm(2) and was almost completely healed in four of the animals. The results demonstrate that the ulcer score was significantly reduced in i.p. (IPEGF) solution (P<0.005), i.g (IG-EGF) solution (P<0.01) and i.g. microemulsion (ME+EGF) (P<0.01) treated groups compared to untreated group. In IG-EGF, ME+EGF treated groups, mucus levels increased significantly compared to their control groups(P<0.05 and P<0.01). In contrast, there was no significant change in the mucus levels following i.p. EGF administration (P>0.05).

Effect of lecithin and MgCO3 as additives on the enzymatic activity of carbonic anhydrase encapsulated in poly(lactide-co-glycolide) (PLGA) microspheres

A model enzyme, carbonic anhydrase, was encapsulated and released from poly(lactide-co-glycolide) (PLGA) microspheres (1-3 microm) made by a novel phase inversion technique. Lecithin was used as a surfactant in the encapsulation process and was incorporated in either the organic phase, aqueous phase, both phases, or not at all. Additional microspheres were also made with lecithin incorporated in the aqueous phase and a basic salt, MgCO3, in the polymeric phase. Released carbonic anhydrase, protein extracted from microspheres, or enzyme incubated with lecithin and PLGA were analyzed via HPLC and activity assay to determine the effect of these additives on protein integrity and activity. Lecithin in the aqueous phase appeared to increase the fraction of enzyme in monomeric form as well as its activity for both extracted protein and released protein as compared to the other formulations without MgCO3. Incubation of enzyme with PLGA degradation products indicated that the acidic environment within the microspheres aids in the irreversible inactivation of the encapsulated protein. Addition of MgCO3 further increased the amount of monomer in both the extracted and released protein by decreasing the amount of acid-induced cleavage and noncovalent aggregation, but still greatly decreased the activity of the enzyme.