Effect of additives on encapsulation efficiency,stability and bioactivity of entrapped lysozyme from biodegradable polymer particles

Low encapsulation efficiency, incomplete and erratic release profiles are the most common features of controlled released protein delivery systems employing biodegradable polymers. In the present study, lysozyme as a model protein was encapsulated in biodegradable microspheres using solvent evaporation method and the effect of amphiphilic stabilizer, a basic salt and a lyoprotectant on microparticle formulation was evaluated. Incorporation rat serum albumin (RSA) in the internal aqueous phase during emulsion increased the encapsulation efficiency of lysozyme and maintained the bioactivity. Use of NaHCO₃ improved the encapsulation efficiency of lysozyme from 15–94%, but at the cost of reduced in vitro release characteristics. Incorporation of both RSA and NaHCO₃ improved the bioactivity of lysozyme and decreased burst release of the protein from the polymer particle, but reduced the encapsulation efficiency from 90–70%. Addition of sucrose in the internal aqueous phase lowered the encapsulation efficiency which was restored by its addition in the external aqueous phase. Maintenance of internal aqueous phase pH close to the iso-electric point of the protein and osmotic balance between the internal aqueous phase and the external aqueous phase during solvent evaporation method helped in better encapsulation of the protein drug. In vitro release of the lysozyme correlated with the effect of different excipients on entrapment in polymer matrix. Entrapment efficiency as high as 76%, low burst effect and high bioactivity of the entrapped lysozyme was observed from the polymer particles. Use of RSA, sucrose and NaHCO₃ helped in a co-operative way towards the formulation of particles entrapping bioactive lysozyme.     

Formulation development and optimization of bilayer tablets of aceclofenac

Objective: The objective of the present study was to develop bilayer tablets of aceclofenac that are characterized by initial burst drug release followed by sustained release of drug.

Methods: The fast-release layer of the bilayer tablet was formulated using microcrystaline cellulose (MCC) and HPMC K4M. The amount of HPMC E4M (X₁) and MCC (X₂) was used as independent variables for optimization of sustained release formulation applying 3² factorial design. Three dependent variables were considered: percentage of aceclofenac release at 1 h, percentage of aceclofenac release at 12 h, and time to release 50% of drug (t_50%). The composition of optimum formulation of sustained release tablets were employed to formulate double layer tablets.

Results: The results indicate that X₁ and X₂ significantly affected the release properties of aceclofenac from sustained release formulation. The double layer tablets containing fast-release layer showed an initial burst drug release of more than 30% of its drug content during first 1 h followed by sustained release of the drug for a period of 24 h.

Conclusion: The double layer tablets for aceclofenac can be successfully employed as once-a-day oral-controlled release drug delivery system characterized by initial burst release of aceclofenac for providing the loading dose of drug.     

Effect of poly(ethylene glycol) content and formulation parameters on particulate properties and intraperitoneal delivery of insulin from PLGA nanoparticles prepared using the double-emulsion evaporation procedure

Abstract

Context: Size, encapsulation efficiency and stability affect the sustained release from nanoparticles containing protein-type drugs.

Objectives: Insulin was used to evaluate effects of formulation parameters on minimizing diameter, maximizing encapsulation efficiency and preserving blood glucose control following intraperitoneal (IP) administration.

Methods: Homogenization or sonication was used to incorporate insulin into poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles with increasing poly(ethylene glycol) (PEG) content. Effects of polymer type, insulin/polymer loading ratio and stabilizer in the internal aqueous phase on physicochemical characteristics of NP, in vitro release and stability of encapsulated insulin were investigated. Entrapment efficiency and release were assessed by radioimmunoassay and bicinconnic acid protein assay, and stability was evaluated using SDS-PAGE. Bioactivity of insulin was assessed in streptozotocin-induced, insulin-deficient Type I diabetic mice.

Results: Increasing polymeric PEG increased encapsulation efficiency, while the absence of internal stabilizer improved encapsulation and minimized burst release kinetics. Homogenization was shown to be superior to sonication, with NP fabricated from 10% PEG–PLGA having higher insulin encapsulation, lower burst release and better stability. Insulin-loaded NP maintained normoglycaemia for 24?h in diabetic mice following a single bolus, with no evidence of hypoglycemia.

Conclusions: Insulin-loaded NP prepared from 10% PEG–PLGA possessed therapeutically useful encapsulation and release kinetics when delivered by the IP route.     

Clinical safety of ranibizumab in age-related macular degeneration

Importance of the field: Clinical safety of pharmaceutical products in the elderly is vital because of their increased risk of cardiac and other adverse events.

Areas covered in this review: Search of the Medline database, including articles and abstracts from 1984 to 2009.

What the reader will gain: Knowledge of ocular and systemic risks: The rate of endophthalmitis was 0.05% per injection (MARINA) and <0.1% per injection (ANCHOR), rates confirmed in a retrospective analysis of 14,320 injections. Moderate increases in intraocular pressure were transient, and incidences of intraocular inflammation were rarely serious. Systemic arterial thromboembolic events occurred in 4.6 and 0% of ranibizumab-treated patients and in 3.8 and 0% of sham-treated patients in MARINA (2 years) and PIER (1 year), respectively. In SAILOR, there was a numerically higher rate of cerebrovascular stroke with 0.5 mg ranibizumab compared with 0.3 mg ranibizumab (1.2 vs 0.7%), which was a non-statistically significant trend in patients with a history of stroke.

Take home message: Although further studies to investigate the risk of stroke with ranibizumab therapy are required, repeated intravitreal ranibizumab was well tolerated and not associated with clinically significant safety risks during up to 2 years of treatment.     

Modulating release of ranibizumab and aflibercept from thiolated chitosan-based hydrogels for potential treatment of ocular neovascularization

Background: This paper describes the synthesis of thiolated chitosan-based hydrogels with varying degrees of crosslinking that has been utilized to modulate release kinetics of two clinically relevant FDA-approved anti-VEGF protein drugs, ranibizumab and aflibercept. These hydrogels have been fabricated into disc shaped structures for potential use as patches on ocular surface.

Methods: Protein conformational changes and aggregation after loading and release was evaluated by circular dichroism (CD), steady-state tryptophan fluorescence spectroscopy, electrophoresis and size-exclusion chromatography (SEC). Finally, the capacity of both released proteins to bind to VEGF was tested by ELISA and surface plasmon resonance (SPR) technology.

Results: The study demonstrates the versatility of thiolated chitosan-based hydrogels for delivering proteins. The effect of various parameters of the hydrogel on protein release kinetics and mechanism of protein release was studied using the Korsmeyer-Peppas release model. Furthermore, we have studied the stability of released proteins in detail while comparing it with non-entrapped proteins under physiological conditions to understand the effect of formulation conditions on protein stability.

Conclusions: The disc-shaped thiolated chitosan-based hydrogels provide a potentially useful platform to deliver ranibizumab and aflibercept for the treatments of ocular diseases such as wet AMD, DME and corneal neovascularization     

Comparative study of DNA encapsulation into PLGA microparticles using modified double emulsion methods and spray drying techniques

Recently, several research groups have shown the potential of microencapsulated DNA as adjuvant for DNA immunization and in tissue engineering approaches. Among techniques generally used for microencapsulation of hydrophilic drug substances into hydrophobic polymers, modified WOW double emulsion method and spray drying of water-in-oil dispersions take a prominent position. The key parameters for optimized microspheres are particle size, encapsulation efficiency, continuous DNA release and stabilization of DNA against enzymatic and mechanical degradation. This study investigates the possibility to encapsulate DNA avoiding shear forces which readily degrade DNA during this microencapsulation. DNA microparticles were prepared with polyethylenimine (PEI) as a complexation agent for DNA. Polycations are capable of stabilizing DNA against enzymatic, as well as mechanical degradation. Further, complexation was hypothesized to facilitate the encapsulation by reducing the size of the macromolecule. This study additionally evaluated the possibility of encapsulating lyophilized DNA and lyophilized DNA/PEI complexes. For this purpose, the spray drying and double emulsion techniques were compared. The size of the microparticles was characterized by laser diffractometry and the particles were visualized by scanning electron microscopy (SEM). DNA encapsulation efficiencies were investigated photometrically after complete hydrolysis of the particles. Finally, the DNA release characteristics from the particles were studied. Particles with a size of <10 microm which represent the threshold for phagocytic uptake could be prepared with these techniques. The encapsulation efficiency ranged from 100-35% for low theoretical DNA loadings. DNA complexation with PEI 25?kDa prior to the encapsulation process reduced the initial burst release of DNA for all techniques used. Spray-dried particles without PEI exhibited high burst releases, whereas double emulsion techniques showed continuous release rates.     

A Polysorbate-Based Non-Ionic Surfactant Can Modulate Loading and Release of β-Lactoglobulin Entrapped in Multiphase Poly(DL-Lactide-co-glycolide) Microspheres

Purpose. The goal of the present paper was to investigate the role of a surfactant, Tween 20, in the modulation of the entrapment and release of -lactoglobulin (BLG) from poly (DL-lactide-co-glycolide) microspheres. Methods. Poly(DL-lactide-co-glycolide) microspheres containing BLG were prepared by a water-in-oil-in-water emulsion solvent procedure. Tween 20 was used as a surfactant in the internal aqueous phase of the primary emulsion. BLG entrapment efficiency and burst release were determined. Displacement of BLG from microsphere surface was followed by confocal microscopy observations and zeta potential measurements, whereas morphological changes were observed by freeze-fracture electron microscopy. Results. Tween 20 was shown to increase 2.8 fold the encapsulation efficiency of BLG without any modification of the stability of the first emulsion and the viscosity of the internal aqueous phase. In fact, Tween 20 was shown to be responsible for removing the BLG molecules that were adsorbed on the particle surface or very close to the surface as shown by confocal microscopy and zeta potential measurements. Tween 20 reduced the number of aqueous channels between the internal aqueous droplets as well as those communications with the external medium. Thus, the more dense structure of BLG microspheres could explain the decrease of the burst release. Conclusions. These results constitute a step forward in the improvement of existing technology in controlling protein encapsulation and delivery from microspheres prepared by the multiple emulsion solvent evaporation method.     

Monitoring Microviscosity and Microacidity of the Albumin Microenvironment Inside Degrading Microparticles from Poly(lactide-co-glycolide) (PLG) or ABA-triblock Polymers Containing Hydrophobic Poly(lactide-co-glycolide) A Blocks and Hydrophilic Poly(ethyleneoxide) B Blocks

Purpose. The purpose of this study was to monitor the microenvironment of an encapsulated model protein during the release from biodegradable microparticles (MP) made from three different polymers, namely poly(lactide-co-glycolide) (PLG) and ABA-triblock polymers containing hydrophobic poly(lactide-co-glycolide) A blocks and hydrophilic poly(ethyleneoxide) B blocks with an A:B ratio of 90:10 (ABA10) and 70:30 (ABA30). Methods. MP loaded with spin labeled albumin were prepared by a w/o/w technique. The particles were characterized by light scattering and electron microscopy. In vitro release of albumin was determined by size exclusion chromatography. Light microscopic experiments were conducted to visualize water penetration in the matrix. The protein microenvironment inside the degrading microparticles was characterized noninvasively by 2 GHz EPR spectroscopy. Results. Water penetrated rapidly into all MP in the range of few minutes. A burst release was observed for PLG. The release from ABA block-polymers continued for over 14 days despite the rapid solubilization of the protein inside the microparticles. The initial microviscosity of the protein environment inside the ABA particles after exposure to buffer was 2 mm²/s and increased with time. A gradual decrease of the pH to a value of 3.5 was observed within the MP. Conclusions. The data indicate that the microviscosity and microacidity inside protein loaded microparticles can be studied nondestructively by EPR spectroscopy. Our results clearly demonstrate that ABA-block polymers are superior to PLG allowing a controlled release of proteins from swollen microspheres.     

Effect of palmitic acid on the characteristics and release profiles of rotigotine-loaded microspheres

Background: The initial burst release is a major obstacle to the development of microsphere-formulated drug products.

Purpose: To investigate the influence of palmitic acid on the characteristics and release profiles of rotigotine-loaded poly(d,l-lactide-co-glycolide) microspheres.

Materials and methods: Rotigotine-loaded microspheres (RMS) were prepared using the oil-in-water emulsion solvent evaporation technique. The in vitro characteristics of the RMS were evaluated with scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and a particle size analyzer. The in vitro drug release and in vivo pharmacokinetics of the RMS were investigated.

Results and discussion: The SEM results showed that the addition of palmitic acid changed the surface morphology of the microspheres from smooth to dimpled and then to non-smooth as the palmitic acid content increased. DSC revealed the existence of molecularly dispersed forms of palmitic acid in the microspheres. The in vitro and in vivo release profiles indicated that the addition of 5% and 8% palmitic acid significantly decreased the burst release of rotigotine from the microspheres, and the late-stage release was delayed as the palmitic acid content increased across the investigated range (5–15%).

Conclusion: The addition of palmitic acid to the microspheres significantly affects the release profile of rotigotine from RMS.     

Influence of the primary emulsification procedure on the characteristics of small protein-loaded PLGA microparticles for antigen delivery

Microparticles prepared from poly(lactic-co-glycolic acid) (PLGA) using a W₁/O/W₂ double emulsion solvent evaporation method are suitable vehicles for the delivery of proteins to antigen presenting cells, e.g. dendritic cells. In this study, the influence of different techniques for the preparation of the primary W₁/O emulsion was investigated with respect to the protein localization within the microparticles, morphological characteristics of these particles, protein burst release and the native state of the released protein. Bovine serum albumin bearing fluorescein isothiocyanate (FITC-BSA) was used as model protein. A static micromixer was applied for the preparation of the W₁/O/W₂ double emulsion. Employing a rotor-stator homogenizer (Ultra-Turrax®) for primary emulsification, microcapsules with a high burst release were produced, because nearly all FITC-BSA was attached to the outside of the particle wall. Using a high pressure homogenizer or an ultrasonic procedure resulted in the formation of microspheres with homogeneous protein distribution and a reduced burst release.     

Floating microspheres of carvedilol as gastro retentive drug delivery system: 32 full factorial design and in vitro evaluation

Abstract

Context: Designing a sustained release system for Carvedilol to increase its residence time in the stomach.

Objective: Preparation of floating microsphere by the emulsion solvent diffusion method, studying the effect of various process parameters and optimize the formulation using full factorial design.

Methods: Different microsphere formulations were prepared by varying the ratio ethanol:dichloromethane (1:0 to 1:1.5), ethyl cellulose:hydroxypropyl methyl cellulose and stirring speed (800–1600?rpm). The effect of these variables on particle size, encapsulation parameters, surface topography, in vitro floatability and drug release were evaluated.

Results: 3² full factorial design was used for the optimization of the formulation. Drug entrapment efficiency, particle size and in vitro drug release were dependent on concentration of ethyl cellulose and stirring speed. Microspheres remained buoyant for more than 10?h and showed sustained release of the drug.

Conclusion: Floating microspheres of Carvedilol with good floating ability and sustained release were developed.     

Utilization of an Amorphous Form of a Water-Soluble GPIIb/IIIa Antagonist for Controlled Release from Biodegradable Microspheres

Purpose. We prepared injectable microspheres for controlled release of TAK-029, a water-soluble GPIIb/IIIa antagonist and discussed the characteristics of controlled release from microspheres. Methods. Copoly(dl-lactic/glycolic)acid (PLGA) microspheres were used for controlled release of TAK-029 [4-(4-amidinobenzoylglycyl)-3-methoxycarbonyl-2-oxopiperazine-l-acetic acid]. They were prepared with a solid-in-oil-in-water (S/O/W) emulsion solvent evaporation technique using either a crystalline form or an amorphous form of the drug. Results. An amorphous form of TAK-029 gave more homogeneous S/O dispersion and higher viscosity than its crystalline form when added to dichloromethane solution of PLGA, resulting in a high drug entrapment into microspheres and a well-controlled release of the drug. Additions of sodium chloride into an external aqueous phase and L-arginine into an oil phase also increased entrapment of the drug, and reduced initial burst of the drug from the microspheres. The micro-spheres demonstrated a desirable plasma level profile in therapeutic range (20–100 ng/ml) for 3 weeks in rats after single subcutaneous injection. Conclusions. A well-controlled release of TAK-029, a water-soluble neutral drug, with small initial burst was achieved by utilizing its amorphous form as a result of possible interaction with PLGA and L-arginine.     

Techniques for efficient entrapment of pharmaceuticals in biodegradable solid micro/nanoparticles

Importance of the field: Biodegradable solid particles are potential carriers for both hydrophobic and hydrophilic drugs and have been marketed for prolongation of pharmaceutical activity. In developing such particles, it is important to achieve stable encapsulation of the drugs in the particles and a controlled rate of drug release.

Areas covered in this review: In this paper, the principles and techniques for preparing such particles are reviewed.

What the reader will gain: Overall, it remains difficult to identify a general approach for achieving effective entrapment and controlled release, because these qualities are determined by multiple complex factors. The encapsulation efficiency of drugs in particles can be improved through various techniques, including hydrophobic interaction, covalent bonding, ionic interaction and physical isolation. In addition, the release behaviors of drugs are strongly influenced by environmental conditions as well as the physicochemical properties of the polymers and drugs.

Take home message: Solid particles with targeting ability in addition to prolongation of biological activity may have potential for development of a new type of pharmaceutical in the clinical field.     

Development and evaluation of co-formulated docetaxel and curcumin biodegradable nanoparticles for parenteral administration

Context: Technology for development of biodegradable nanoparticles encapsulating combinations for enhanced efficacy.

Objective: To develop docetaxel (DTX) and curcumin (CRM) co-encapsulated biodegradable nanoparticles for parenteral administration with potential for prolonged release and decreased toxicity.

Materials and methods: Modified emulsion solvent-evaporation technique was employed in the preparation of the nanoparticles optimized by the face centered-central composite design (FC-CCD). The uptake potential was studied in MCF-7 cells, while the toxicity was evaluated by in vitro hemolysis test. In vivo pharmacokinetic was evaluated in male Wistar rats.

Results and discussion: Co-encapsulated nanoparticles were developed of 219?nm size, 0.154 PDI, ?13.74?mV zeta potential and 67.02% entrapment efficiency. Efficient uptake was observed by the nanoparticles in MCF-7 cells with decreased toxicity in comparison with the commercial DTX intravenous injection, Taxotere®. The nanoparticles exhibited biphasic release with initial burst release followed by sustained release for 5 days. The nanoparticles displayed a 4.3-fold increase in AUC (391.10?±?32.94 versus 89.77?±?10.58?μg/ml min) in comparison to Taxotere® with a 6.2-fold increase in MRT (24.78?±?2.36 versus 3.58?±?0.21?h).

Conclusion: The nanoparticles exhibited increased uptake, prolonged in vitro and in vivo release, with decreased toxicity thus exhibiting potential for enhanced efficacy.     

Injectable hybrid delivery system composed of gellan gum,nanoparticles and gentamicin for the localized treatment of bone infections

ABSTRACT

Objectives: Bone infections are treated with antibiotics administered intravenously, antibiotic-releasing bone cements or collagen sponges placed directly in the infected area. These approaches render limited effectiveness due to the lack of site specificity and invasiveness of implanting cements and sponges. To address these limitations, we developed a novel polysaccharide hydrogel-based injectable system that enables controlled delivery of gentamicin (GENT). Its advantages are minimal invasiveness, and localized and finely regulated release of the drug.

Methods: GENT was incorporated both directly within the gellan gum hydrogel and into poly(L-lactide-co-glycolide) nanoparticles embedded into the hydrogel.

Results: We confirmed the injectability of the system and measured extrusion force was 15.6 ± 1.0 N, which is suitable for injections. The system set properly after the injection as shown by rheological measurements. Desired burst release of the drug was observed within the first 12 h and the dose reached ~27% of total GENT. Subsequently, GENT was released gradually and sustainably: ~60% of initial dose within 90 days. In vitro studies confirmed antimicrobial activity of the system against Staphylococcus spp. and cytocompatibility with osteoblast-like cells.

Conclusions: Developed injectable system enables minimally invasive, local and sustained delivery of the pharmaceutically relevant doses of GENT to combat bone infections.     

Improving Protein Delivery from Microparticles Using Blends of Poly(DL lactide co-glycolide) and Poly(ethylene oxide)-poly(propylene oxide) Copolymers

Purpose. Microparticles containing ovalbumin as a model for protein drugs were formulated from blends of poly(DL lactide-co-glycolide) and poly(ethylene oxide)-poly(propylene oxide) copolymers (Pluronic). The objectives were to achieve uniform release characteristics and improved protein delivery capacity. Methods. The water- in oil -in oil emulsion/solvent extraction technique was used for microparticle production. Results. A protein loading level of over 40% (w/w) was attained in microparticles having a mean diameter of approximately 5 µm. Linear protein release profiles over 25 days in vitro were exhibited by certain blend formulations incorporating hydrophilic Pluronic F127. The release profile tended to plateau after 10 days when the more hydrophobic Pluronic L121 copolymer was used to prepare microparticles. A delivery capacity of 3 µg OVA/mg particles/ day was achieved by formulation of microparticles using a 1:2 blend of PLG:Pluronic F127. Conclusions. The w/o/o formulation approach in combination with PLG:Pluronic blends shows potential for improving the delivery of therapeutic proteins and peptides from microparticulate systems. Novel vaccine formulations are also feasible by incorporation of Pluronic L121 in the microparticles as a co-adjuvant.     

The Stability of Recombinant Human Growth Hormone in Poly(lactic-co-glycolic acid) (PLGA) Microspheres

Purpose. The development of a sustained release formulation for recombinant human growth hormone (rhGH) as well as other proteins requires that the protein be stable at physiological conditions during its in vivo lifetime. Poly(lactic-co-glycolic acid) (PLGA) microspheres may provide an excellent sustained release formulation for proteins, if protein stability can be maintained. Methods. rhGH was encapsulated in PLGA microspheres using a double emulsion process. Protein released from the microspheres was assessed by several chromatrographic assays, circular dichroism, and a cell-based bioassay. The rates of aggregation, oxidation, diketopiperazine formation, and deamidation were then determined for rhGH released from PLGA microspheres and rhGH in solution (control) during incubation in isotonic buffer, pH 7.4 and 37°C. Results. rhGH PLGA formulations were produced with a low initial burst (<20%) and a continuous release of rhGH for 30 days. rhGH was released initially from PLGA microspheres in its native form as measured by several assays. In isotonic buffer, pH 7.4 and 37°C, the rates of rhGH oxidation, diketopiperazine formation, and deamidation in the PLGA microspheres were equivalent to the rhGH in solution, but aggregation (dimer formation) occured at a slightly faster rate for protein released from the PLGA microspheres. This difference in aggregation rate was likely due to the high protein concentration used in the encapsulation process. The rhGH released was biologically active throughout the incubation at these conditions which are equivalent to physiological ionic strength and pH. Conclusions. rhGH was successfully encapsulated and released in its fully bioactive form from PLGA microspheres over 30 days. The chemical degradation rates of rhGH were not affected by the PLGA microspheres, indicating that the internal environment of the microspheres was similar to the bulk solution. After administration, the microspheres should become fully hydrated in the subcutaneous space and should experience similar isotonic conditions and pH. Therefore, if a protein formulation provides stability in isotonic buffer, pH 7.4 and 37°C, it should allow for a safe and efficacious sustained release dosage form in PLGA microspheres.     

Metronidazole and Pentoxifylline films for the local treatment of chronic periodontal pockets: preparation,in vitro evaluation and clinical assessment

Objective: Periodontitis is one of the most important chronic inflammatory dental diseases arising from the destructive actions caused by a variety of pathogenic organisms presented in the oral cavity. The aim of this study is the preparation and in vitro evaluation of films for the local treatment of periodontal pockets.

Methods: The prepared films contained either metronidazole (Mtr), for its antimicrobial effect in periodontal diseases, using a mixture of polymers namely hydroxypropyl methyl cellulose, Carbopol 934 or locally applied Pentoxifylline (PTX), for its anti-inflammatory activity, using chitosan. All films were prepared using solvent casting technique and were evaluated for their physical characteristics, drug content uniformity, surface pH, swelling behavior, mechanical properties and in vitro release. Further characterization was done on the selected formulations using differential scanning calorimetry and scanning electron microscopy for surface structure. Clinical evaluation tests were also performed.

Result: Appropriate physical characteristics and mechanical properties for most formulations and their suitability for periodontal application were observed. In vitro drug release from most films showed a burst release rate for both Mtr and PTX during the first 2 h after which the release rate was markedly decreased. Clinical trials on patients revealed the advantageous use of Mtr and PTX as an adjunct treatment with traditionally used dental techniques.

Conclusion: The effectiveness of the co-therapy of either drug could add benefit in the eradication of chronic periodontal hazards.     

pH triggered delivery of curcumin from Eudragit-coated chitosan microspheres for inflammatory bowel disease: characterization and pharmacodynamic evaluation

Objective: This investigation deals with the development and evaluation (in vitro and in vivo) of pH triggered Eudragit-coated chitosan microspheres of curcumin (CUR) for treating ulcerative colitis.

Methods: CUR-loaded chitosan microspheres were initially prepared by emulsion cross linking method followed by coating with Eudragit S-100. The pharmacodynamics of the developed formulation was analyzed in mice by acetic acid induced colitis model.

Results: The developed microspheres were of uniform spherical shape with high entrapment efficiency. CUR-chitosan microspheres showed less intense peaks compared to free CUR confirming inclusion of drug within microspheres as revealed by X-ray diffractogram. Uncoated CUR-chitosan microspheres exhibited burst release within initial 4?h while microspheres coated with Eudragit S-100 prevented premature release of CUR and showed controlled release up to 12?h following Higuchi model. In vivo organ biodistribution study showed negligible amount of CUR in stomach and small intestine confirming integrity of microsphere in upper gastrointestinal tract (GIT). In vivo study revealed significant reduction in severity and extent of colonic damage with CUR-loaded microspheres as compared to pure CUR which was further confirmed by histopathological study.

Conclusion: In vitro and in vivo studies proved the developed formulations as a promising system for pH-dependent delivery of drug to colon in ulcerative colitis.     

Comparative study of DNA encapsulation into PLGA microparticles using modified double emulsion methods and spray drying techniques

Recently, several research groups have shown the potential of microencapsulated DNA as adjuvant for DNA immunization and in tissue engineering approaches. Among techniques generally used for microencapsulation of hydrophilic drug substances into hydrophobic polymers, modified WOW double emulsion method and spray drying of water-in-oil dispersions take a prominent position. The key parameters for optimized microspheres are particle size, encapsulation efficiency, continuous DNA release and stabilization of DNA against enzymatic and mechanical degradation. This study investigates the possibility to encapsulate DNA avoiding shear forces which readily degrade DNA during this microencapsulation. DNA microparticles were prepared with polyethylenimine (PEI) as a complexation agent for DNA. Polycations are capable of stabilizing DNA against enzymatic, as well as mechanical degradation. Further, complexation was hypothesized to facilitate the encapsulation by reducing the size of the macromolecule. This study additionally evaluated the possibility of encapsulating lyophilized DNA and lyophilized DNA/PEI complexes. For this purpose, the spray drying and double emulsion techniques were compared. The size of the microparticles was characterized by laser diffractometry and the particles were visualized by scanning electron microscopy (SEM). DNA encapsulation efficiencies were investigated photometrically after complete hydrolysis of the particles. Finally, the DNA release characteristics from the particles were studied. Particles with a size of <10?µm which represent the threshold for phagocytic uptake could be prepared with these techniques. The encapsulation efficiency ranged from 100–35% for low theoretical DNA loadings. DNA complexation with PEI 25?kDa prior to the encapsulation process reduced the initial burst release of DNA for all techniques used. Spray-dried particles without PEI exhibited high burst releases, whereas double emulsion techniques showed continuous release rates.