Preparation of biodegradable poly(+/-)lactide microparticles using a spray-drying technique

Impact of dispersion time interval and particle size on release profiles of propranolol HCl and carbamazepines from microparticle blends system

The objective of this study was to investigate the effect of dispersion time interval (DTI) on physicochemical properties of drug following the incorporation of propranolol HCl (Pro) and carbamazepine (CBZ) within ethyl cellulose (EC) microparticle blends using solvent evaporation method. The first Pro emulsion and second CBZ oil phase were dispersed in an external aqueous phase, with DTI of 0 and 60 min. The morphology of microparticle blends were characterized by SEM. The particle size mean of the emulsion droplets/hardened microparticles were monitored by FBRM. Encapsulation efficiency (EE) and in vitro drug release were also investigated. The resulting microparticle blends were spherical and formed two populations. The particle size mean of microparticle blends ranged from 113.27 µm to 122.42 µm. The EE was 77.28% to 78.64% for Pro and 96.48% to 98.64% for CBZ. FBRM studies showed that the size of microparticle blend prepared as W/O/W (Pro) and O/W (CBZ) system with DTI of 60 min and stirring time 4 h were larger than those prepared with DTI of 0 min. In vitro drug release studies after 28 days that revealed the CBZ release (58.72%) was faster than Pro release (43.16%). Investigation on surface morphology by SEM showed that the second drug CBZ which added as the oil phase in the W/O/W emulsion system had blocked the pores on the surface Pro microparticles prepared from the first primary emulsion, therefore affecting the drug release. This blocking effects of second drug (CBZ) on first emulsion microparticles (Pro) depended on the DTI. This phenomenon is only applicable if the first primary emulsion is W/O/W system.

Harnessing Dendritic Cells for Poly (D,L-lactide-co-glycolide) Microspheres (PLGA MS)-Mediated Anti-tumor Therapy

With emerging success in fighting off cancer, chronic infections, and autoimmune diseases, immunotherapy has become a promising therapeutic approach compared to conventional therapies such as surgery, chemotherapy, radiation therapy, or immunosuppressive medication. Despite the advancement of monoclonal antibody therapy against immune checkpoints, the development of safe and efficient cancer vaccine formulations still remains a pressing medical need. Anti-tumor immunotherapy requires the induction of antigen-specific CD8+ cytotoxic T lymphocyte (CTL) responses which recognize and specifically destroy tumor cells. Due to the crucial role of dendritic cells (DCs) in initiating anti-tumor immunity, targeting tumor antigens to DCs has become auspicious in modern vaccine research. Over the last two decades, micron- or nanometer-sized particulate delivery systems encapsulating tumor antigens and immunostimulatory molecules into biodegradable polymers have shown great promise for the induction of potent, specific and long-lasting anti-tumor responses in vivo. Enhanced vaccine efficiency of the polymeric micro/nanoparticles has been attributed to controlled and continuous release of encapsulated antigens, efficient targeting of antigen presenting cells (APCs) such as DCs and subsequent induction of CTL immunity. Poly (D, L-lactide-co-glycolide) (PLGA), as one of these polymers, has been extensively studied for the design and development of particulate antigen delivery systems in cancer therapy. This review provides an overview of the current state of research on the application of PLGA microspheres (PLGA MS) as anti-tumor cancer vaccines in activating and potentiating immune responses attempting to highlight their potential in the development of cancer therapeutics.

Solvent-free preparation of porous poly(l-lactide) microcarriers for cell culture

Porous polymeric microcarriers are a versatile class of biomaterial constructs with extensive use in drug delivery, cell culture and tissue engineering. Currently, most methods for their production require potentially toxic organic solvents with complex setups which limit their suitability for biomedical applications and their large-scale production. Herein, we report an organic, solvent-free method for the fabrication of porous poly(l-lactide) (PLLA) microcarriers. The method is based on the spherulitic crystallization of PLLA in its miscible blends with poly(ethylene glycol) (PEG). It is shown that the PLLA spherulites are easily recovered as microcarriers from the blends by a water-based process. Independent control over microcarrier size and porosity is demonstrated, with a higher crystallization temperature leading to a larger size, and a higher PLLA content in the starting blend resulting in a lower microcarrier porosity. Microcarriers are shown to be biocompatible for the culture of murine myoblasts and human adipose stromal/stem cells (hASC). Moreover, they support not only the long-term proliferation of both cell types but also hASC differentiation toward osseous tissues. Furthermore, while no significant differences are observed during cell proliferation on microcarriers of two different porosities, microcarriers of lower porosity induce a stronger hASC osteogenic differentiation, as evidenced by higher ALP enzymatic activity and matrix mineralization. Consequently, the proposed organic-solvent-free method for the fabrication of biocompatible porous PLLA microcarriers represents an innovative methodology for ex vivo cell expansion and its application in stem cell therapy and tissue engineering.

STATEMENT OF SIGNIFICANCE

We report a new solvent-free method for the preparation of porous polymeric microcarriers for cell culture, based on biocompatible poly(l-lactide), with independently controllable size and porosity. This approach, based on the spherulitic crystallization in polymer blends, offers the advantages of simple implementation, biological and environmental safety, easy adaptability and up-scalablility. The suitability of these microcarriers is demonstrated for long-term culture of both murine myoblasts and human adipose stromal/stem cells (hASCs). We show that prepared microcarriers support the osteogenic differentiation of hASCs, provided microcarriers of properly-tuned porosity are used. Hence, this new method is an important addition to the arsenal of microcarrier fabrication techniques, which will contribute to the adoption, regulatory approval and eventually clinical availability of microcarrier-based treatments and therapies.

PLA micro- and nano-particles

Poly(d,l-lactic acid) (PLA) has been widely used for various biomedical applications for its biodegradable, biocompatible, and nontoxic properties. Various methods, such as emulsion, salting out, and precipitation, have been used to make better PLA micro- and nano-particle formulations. They are widely used as controlled drug delivery systems of therapeutic molecules, including proteins, genes, vaccines, and anticancer drugs. Even though PLA-based particles have challenges to overcome, such as low drug loading capacity, low encapsulation efficiency, and terminal sterilization, continuous innovations in particulate formulations will lead to development of clinically useful formulations.

Preparation, characterization, and potential application of chitosan, chitosan derivatives, and chitosan metal nanoparticles in pharmaceutical drug delivery

Naturally occurring polymers, particularly of the polysaccharide type, have been used pharmaceutically for the delivery of a wide variety of therapeutic agents. Chitosan, the second abundant naturally occurring polysaccharide next to cellulose, is a biocompatible and biodegradable mucoadhesive polymer that has been extensively used in the preparation of micro-as well as nanoparticles. The prepared particles have been exploited as a potential carrier for different therapeutic agents such as peptides, proteins, vaccines, DNA, and drugs for parenteral and nonparenteral administration. Therapeutic agent-loaded chitosan micro- or nanoparticles were found to be more stable, permeable, and bioactive. In this review, we are highlighting the different methods of preparation and characterization of chitosan micro- and nanoparticles, while reviewing the pharmaceutical applications of these particles in drug delivery. Moreover, the roles of chitosan derivatives and chitosan metal nanoparticles in drug delivery have been illustrated.

Mechanisms of burst release from pH-responsive polymeric microparticles

OBJECTIVES

Microencapsulation of drugs into preformed polymers is commonly achieved through solvent evaporation techniques or spray drying. We compared these encapsulation methods in terms of controlled drug release properties of prepared microparticles and investigated the underlying mechanisms responsible for the 'burst release' effect.

METHODS

Using two different pH-responsive polymers with a dissolution threshold of pH 6 (Eudragit L100 and AQOAT AS-MG), hydrocortisone, a model hydrophobic drug, was incorporated into microparticles below and above its solubility within the polymer matrix.

KEY FINDINGS

Although, spray drying was an attractive approach due to rapid particle production and relatively low solvent waste, the oil-in-oil microencapsulation method was superior in terms of controlled drug release properties from the microparticles. Slow solvent evaporation during the oil-in-oil emulsification process allowed adequate time for drug and polymer redistribution in the microparticles and reduced uncontrolled drug burst release. Electron microscopy showed that this slower manufacturing procedure generated nonporous particles whereas thermal analysis and X-ray diffractometry showed that drug loading above the solubility limit of the drug in the polymer generated excess crystalline drug on the surface of the particles. Raman spectral mapping illustrated that drug was homogeneously distributed as a solid solution in the particles when loaded below saturation in the polymer with consequently minimal burst release.

CONCLUSIONS

Both the manufacturing method (which influenced particle porosity and density) and drug:polymer compatibility and loading (which affected drug form and distribution) were responsible for burst release seen from our particles.

Microbubbles as ultrasound triggered drug carriers

Originally developed as contrast agents for ultrasound imaging and diagnostics, in the past years, microbubbles have made their way back from the patients' bedside to the researcher's laboratory. Microbubbles are currently believed to have great potential as carriers for drugs, small molecules, nucleic acids, and proteins. This review provides insight into this intriguing new frontier from the perspective of the pharmaceutical scientist. First, basic aspects on the application of ultrasound-targeted microbubble destruction for drug delivery will be presented. Next, we will review the recently applied approaches for manufacturing and drug-loading microbubbles. Important quality issues and characterization techniques for advanced microbubble formulation will be discussed. Finally, we will provide an assessment of the prospects for microbubbles in drug and gene therapy, illustrating the problems and requirements for their future development.

Intraosseous delivery of paclitaxel-loaded hydroxyapatitealginate composite beads delaying paralysis caused by metastatic spine cancer in rats

Object

Bone is frequently the first site and the only site of breast cancer at recurrence. Local control is important especially for metastatic spine cancer, because epidural spinal cord compression is significantly associated with the quality of life and survival of these patients. The authors have developed a local delivery system of paclitaxel in the form of hydroxyapatite-alginate composite beads. This study was conducted to clarify the therapeutic effect in a rat model of metastatic spine cancer.

Methods

Twenty-one rats with metastatic spine cancer were divided into 3 groups: a local treatment group (6 rats), a systemic treatment group (9 rats), and a control group (6 rats). The hind-limb motor function of the animals was monitored daily by using the Basso-Beattie-Bresnahan scale. The authors monitored the disease-free time and survival times. The log-rank test was used to define statistically significant differences between the 3 groups.

Results

The animals in the control group developed hind-limb paralysis at a mean of 10.8 days and died at a mean of 16.0 days. The animals treated with 2.4 wt% of paclitaxel-loaded hydroxyapatite-alginate composite beads (the local treatment group) showed a 140–150% increase in the disease-free time and survival time compared with that of the control group. Although an ~ 30-fold higher dosage of paclitaxel was administered, the therapeutic effect was not evident in the systemic treatment group.

Conclusions

Intraosseous delivery of paclitaxel-loaded hydroxyapatite-alginate composite beads delayed paralysis caused by metastatic spine cancer in rats. The results indicate that intraosseous chemotherapy may provide an effective local treatment of metastatic spine cancer.

Influence of Formulation Variables on the Morphology of Biodegradable Micropartieles Prepared by Spray Drying

The preparation of microparticles of the biodegradable poly-DL-lactide (PLA) and polylactide-co-glycolide (PLGA) polymers using spray-drying technology was studied. Formulation parameters investigated include polymer type, polymer molecular weight, polymer concentration, and viscosity. Microparticles were characterized using electron microscopy, particle size analysis, and gel permeation chromatography. Kinematic viscosity was determined for each of the sprayed polymer solutions. Polymer molecular weight and polymer concentration were found to be important parameters when preparing PLA and PLGA microparticles using spray-drying technology.

Production of BSA-loaded alginate microcapsules: Influence of spray dryer parameters on the microcapsule characteristics and BSA release

The aim of this study was to optimize the production of BSA-loaded alginate microcapsules by spray drying and to study the release of bovine serum albumin fraction V (BSA) under gastric simulated conditions. Microcapsule yield, BSA release, microcapsule size and size distribution were characterized following the application of different production parameters including inlet air temperature, inlet air pressure and liquid feed rate. The microcapsules were incubated in 0.1 N HCl and BSA release was quantified over time. The yields were higher with the pressure of 3 bar compared to 4 bar and with a feed rate of 0.45 vs. 0.2 ml s(-1). A high feed rate (0.45 vs. 0.2 ml s(-1)) allows one to obtain microcapsules with a low BSA release (p = 0.0327). The increase of the atomizer inlet temperature leads to microcapsules with a higher BSA release (p = 0.0230). A higher air pressure of 4 bar compared to 3 bar resulted in a lower microcapsule size (2.55 vs. 2.80 microm) and led to a narrower size distribution (0.92 vs. 1.07). In conclusion, the spray dryer parameters influenced the alginate microcapsule characteristics as well as subsequent protein release into a simulated gastric medium.

Nanoparticle-coated microparticles: preparation and characterization

The objective of the present work was to design and prepare new nanoparticle-coated drug-loaded inorganic microparticles by spray-drying using diclofenac as drug model. Previous works presented the process to dry drug-loaded polymeric nanoparticles using silicon dioxide as adjuvant, otherwise in the present proposition the drug is associated with the silicon dioxide and unloaded polymeric nanocapsule or nanosphere suspensions were used as organic coating. Eudragit S100 was chosen because of its gastric resistance. The potential application of polymeric colloidal suspensions as nanocoating for microparticles were evaluated in terms of process yields, encapsulation efficiencies, morphologic analyses and in vitro drug release profiles in buffered media (pH 1.2; 5.0 and 7.4). The results showed the technological feasibility of preparing controlled nanoparticle-coated drug-loaded inorganic microparticles. When the diclofenac was employed as a hydrophilic model, in this salt form, the powders prepared in two steps (core previously prepared) showed an adequate gastroresistance by the use of Eudragit S100. The use of diclofenac as a hydrophobic model (acid form) conducted to powders presenting good gastroresistance when the nanocapsules and triacetin were employed.

Slow release formulations of inhaled rifampin

Rifampin microspheres were prepared by spray drying using either polylactic acid (PLA) or poly(lactic-co-glycolic acid) (PLGA) polymers in different drug to polymer ratios (90:10 to 5:95, w/w). The in-vitro release characteristics, particle-size distribution, and cytotoxicity (in an alveolar macrophage cell line) and pharmacokinetics in rats after pulmonary instillation were evaluated. Increasing the polymer content from 10% to 95% slowed down the in vitro drug release with PLGA particles showing a steeper change with increasing polymer content (100% to 20% drug release over 6 h) than PLA particles (88% to 42% drug release over 6 h). PLA microsphere formulations revealed lack of cytotoxicity and a mass median aerodynamic diameter (MMDA) of 2.22-2.86 mum, while PLGA particles were larger (MMDA of 4.67-5.11 mum). Pharmacokinetics differed among the formulations with the 10% PLA formulation showing a distinct sustained release (t (max) of 2 h vs 0.5 h of free drug) and a systemic bioavailability similar to that of free drug. Formulations with high polymer content showed a lower relative bioavailability (30%). This suggested that an optimal release rate existed for which a distinct amount of drug was delivered over an extended period of time.

Principles of encapsulating hydrophobic drugs in PLA/PLGA microparticles

Injectable biodegradable and biocompatible copolymers of lactic and glycolic acid (PLGA) are an important advanced delivery system for week-to-month controlled release of hydrophobic drugs (e.g., from biopharmaceutical classification system class IV), which often display poor oral bioavailability. The basic principles and considerations to develop such microparticle formulations is reviewed here based on a comprehensive study of papers and patents from the beginnings of hydrophobic drug encapsulation in polylactic acid and PLGA up through the very recent literature. Challenges with the diversity of drug properties, microencapsulation methods, and organic solvents are evaluated in light of the precedence of commercialized formulations and with a focus on decreasing the time to lab-scale encapsulation of water-insoluble drug candidates in the early stage of drug development. The influence of key formulation variables on final microparticle characteristics, and how best to avoid undesired microparticle properties, is analyzed mechanistically. Finally, concepts are developed to manage the common issues of maintaining sink conditions for in vitro drug release assays of hydrophobic compounds. Overall, against the backdrop of an increasing number of new, poorly orally available drug entities entering development, microparticle delivery systems may be a viable strategy to rescue an otherwise undeliverable substance.

Gelatin microspheres cross-linked with EDC as a drug delivery system for doxycyline: development and characterization

Chronic wounds express elevated levels of proteases, in particular matrix metalloproteinases (MMPs), which degrades de novo granulation tissue and endogenous biologically active proteins. An effective therapeutic approach for chronic wounds would be to modify this hostile environment and reduce the proteolytic imbalance. Doxycycline has been proved recently to inhibit MMPs and used topically for chronic wound ulcers, beyond their antimicrobial profile. To this end, a carrier system for controlled release of doxycycline, suitable for incorporation into various wound dressings like membranes and sponges was developed. In the present study gelatin microspheres, cross-linked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) was proposed. The cross-linking was carried out with different concentrations of EDC (10 mM, 50 mM and 100 mM) and for different time periods (3-24 h). The cross-linked microspheres were characterized by evaluating the extent of cross-linking, the morphology, swelling behaviour and drug loading and in vitro studies of drug release, enzymatic degradation and biocompatibility. The extent of cross-linking increased as a function of both EDC concentration and the cross-linking time periods. It is found that the extent of cross-linking greatly influences the swelling and drug release behaviour of the microspheres. The cross-linked microspheres were found to be biocompatible to NIH 3T3 mouse embryonic fibroblast. The overall study indicates that the zero length cross-linker EDC can be considered as a potential alternative for cross-linking the gelatin microspheres.

Spray-dried microparticles containing polymeric nanocapsules: Formulation aspects, liquid phase interactions and particles characteristics

Up to now, the full potential of polymer-based nanoparticles is not yet exploited because of a lack of stability when conserved in aqueous medium. The present paper reports the water elimination from nanocapsules (NC) dispersions by means of the spray-drying technique with the aim to achieve dried solid forms of interest using colloidal silicon dioxide as drying auxiliary. The influence of formulation parameters on the suspension behaviour and on the powders characteristics was also evaluated. Our findings demonstrated that the mixing protocol, the concentrations of both NC and silica are crucial parameters that affect the feed behaviour and the spray-dried particles characteristics. Interactions occurring in the feed are directed by hydrogen bounds and were more sensitive to the silica concentration than that of NC as evidenced by rheological measurements. The NC are entrapped within solid dried matrixes following their interaction with silica particles in the feed. SEM analyses of the obtained powders showed spherical separated microparticles formed by the association of NC and silica when they are mixed at adequate concentrations in the feed before spray-drying. On the other hand, fused agglomerated particles presenting NC at their surface, characterised by irregular shapes and a strong adhesiveness were prepared when the silica concentration was not sufficient. The surface composition of the spray-dried powders was investigated using the ESCA technique and revealed the NC exclusion from the surface to obtain powders suitable for further handling.

Etoposide-loaded nanoparticles made from glyceride lipids: formulation, characterization, in vitro drug release, and stability evaluation

The aim of the study was to prepare etoposide-loaded nanoparticles with glyceride lipids and then characterize and evaluate the in vitro steric stability and drug release characteristics and stability. The nanoparticles were prepared by melt emulsification and homogenization followed by spray drying of nanodispersion. Spray drying created powder nanoparticles with excellent redispersibility and a minimal increase in particle size (20-40 nm). Experimental variables, such as homogenization pressure, number of homogenization cycles, and surfactant concentration, showed a profound influence on the particle size and distribution. Spray drying of Poloxamer 407-stabilized nanodispersion lead to the formation of matrix-like structures surrounding the nanoparticles, resulting in particle growth. The in vitro steric stability test revealed that the lipid nanoparticles stabilized by sodium tauroglycocholate exhibit excellent steric stability compared with Poloxamer 407. All 3 glyceride nanoparticle formulations exhibited sustained release characteristics, and the release pattern followed the Higuchi equation. The spray-dried lipid nanoparticles stored in black polypropylene containers exhibited excellent long-term stability at 25 degrees C and room light conditions. Such stable lipid nanoparticles with in vitro steric stability can be a beneficial delivery system for intravenous administration as long circulating carriers for controlled and targeted drug delivery.

Mucoadhesive microspheres for controlled drug delivery

Mucoadhesion is a topic of current interest in the design of drug delivery systems. Mucoadhesive micro-spheres exhibit a prolonged residence time at the site of application or absorption and facilitate an intimate contact with the underlying absorption surface and thus contribute to improved and/or better therapeutic performance of drugs. In recent years such mucoadhesive microspheres have been developed for oral, buccal, nasal, ocular, rectal and vaginal routes for either systemic or local effects. The objective of this article is review the principles underlying the development and evaluation of mucoadhesive microspheres and the research work carried out on these systems.

Novel powder formulations for controlled delivery of poorly soluble anticancer drug: Application and investigation of TPGS and PEG in spray-dried particulate system

Biodegradable poly (lactic-co-glycolic acid) (PLGA), D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS) and/or polyethylene glycol (PEG) were combined as pharmaceutical excipient to fabricate microparticles containing sparingly soluble drug paclitaxel by spray-drying technique with successful achievement. The effect of formulation variety on particle morphology, surface composition, thermal property, drug entrapped capability, and drug release profile was investigated. The result indicated that the use of the appropriate mixtures of PLGA, TPGS and/or PEG produced paclitaxel-loaded microparticles characterised by acceptable pharmaceutical properties. Atomic force microcopy (AFM) and scanning electron microscopy (SEM) showed that the produced microparticles were spherical in shape with dimples or pores. The particle size ranged from 0.88 to 2.44 microm with narrow distribution. The combination of TPGS and PEG in the formulation resulted in a narrow particle size distribution in general although the influence of the formulation on the particle size was not significant. Differential scanning calorimetry (DSC) study implied that all those components in consideration were compatible well in the blend formulation systems. The paclitaxel entrapped in the particles existed in an amorphous or disordered-crystalline status in the matrices and was independent of the PLGA/TPGS/PEG ratio. X-ray photoelectron spectroscope (XPS) analysis revealed that after incorporation the particle's surface was dominated with PLGA due to its hydrophobic property. The formulation variety had an important impact on the drug release that was reduced with the presence of large fraction of TPGS resulting from a strong hydrophobic interaction between various matrix materials and the drug inside the particle. A zero order release could be yielded by optimising the ratio of PLGA/TPGS/PEG. The combination of PLGA/TPGS/PEG as safe pharmaceutical excipient to formulate particulate delivery system is beneficial in improving the pharmaceutical properties for further powder dosage application.

Oil core-polymer shell microcapsules prepared by internal phase separation from emulsion droplets. I. Characterization and release rates for microcapsules with polystyrene shells

Microcapsules with an oil core surrounded by a polymeric shell have been prepared by the controlled phase separation of polymer dissolved within the oil droplets of an oil-in-water emulsion. The dispersed oil phase consists of the shell polymer (polystyrene), a good solvent for the polymer (dichloromethane), and a poor solvent for the polymer (typically hexadecane). Removal of the good solvent results in phase separation of the polymer within the oil droplets. If the three interfacial tensions between the core oil, the shell-forming polymer, and the continuous phase are of the required relative magnitudes, a polymer shell forms surrounding the poor solvent. A UV-responsive organic molecule was added to the oil phase, prior to emulsification, to investigate the release of a model active ingredient from the microcapsules. This molecule should be soluble in the organic core but also have some water solubility to provide a driving force for release into the continuous aqueous phase. As the release rate of the active ingredient is a function of the thickness of the polymeric shell, for controlled release applications, it is necessary to control this parameter. For the preparative method described here, the thickness of the shell formed is directly related to the mass of polymer dissolved in the oil phase. The rate of volatile solvent removal influences the porosity of the polymer shell. Rapid evaporation leads to cracks in the shell and a relatively fast release rate of the active ingredient. If a more gentle evaporation method is employed, the porosity of the polymer shell is decreased, resulting in a reduction in release rate. Cross-linking the polymer shell after capsule formation was also found to decrease both the release rate and the yield of the active ingredient. The nature of the oil core also affected the release yield.

Microencapsulation of superoxide dismutase into biodegradable microparticles by spray-drying

The aim of this work was to encapsulate superoxide dismutase (SOD) into biodegradable microparticles by spray-drying technique. The nature of the organic solvent to dissolve the polymer, the method of incorporation of the drug in the organic phase (with or without a surfactant, namely sucrose ester of HLB = 6), the surfactant/polymer ratio, and the nature of the biodegradable polyesters were investigated as formulation variables. The polyesters investigated as matrix were poly(epsilon-caprolactone) (PCL), poly(d, l, lactide-co-glycolide) (PLG-RG756), and poly(d, l-lactide) (PLA-R207) of respective molecular weight 78.2 kDa, 84.8 kDa, and 199.8 kDa. At surfactant/polymer ratio of 1/10, the SOD-retained enzymatic activities were higher (> 95%) for PLG-RG756 and PLA-R207 but relatively lower for the PCL (approximately 85%) probably due to the PCL relatively higher hydrophobicity. The obtained microparticles exhibited average volume mean diameter of 4-10 microm, the smaller for PCL and the larger for PLG-RG756 polymeric matrix. The in vitro release profile showed that SOD was completely (100%) released from PLA-R207 in 48 hr and from PLG-RG756 and PCL within 72 hr. These results showed that spray-drying with incorporation of surfactant such as sucrose ester may efficiently encapsulate SOD into biodegradable microparticles. Such formulations may improve the bioavailability of SOD and similar biopharmaceuticals.