Spray drying technique to produce controlled release formulations of zidovudine—an anti‐HIV drug

This article explores the application of spray drying technique to produce microparticles of poly(D ,L ‐lactide‐co‐glycolic acid) (PLGA), as well as di‐block copolymer of polylactic acid (PLA) and polyethylene glycol (PEG) (PLA‐PEG), containing zidovudine (AZT), an anti‐HIV drug, to achieve its controlled release over an extended period of time. Of the two polymers studied, PLGA is hydrophobic, whereas PLA‐PEG is hydrophilic and the drug, AZT is water‐soluble. Formulations were developed containing 10 and 25 wt % of AZT giving encapsulation efficiencies (EE) of 66 to 86% for PLGA and 90 to 94% for PLA‐PEG di‐block copolymer. All the formulations were characterized by Fourier transform spectroscopy (FTIR) to investigate the interaction of AZT with polymers and to characterize PLA‐PEG. NMR was also employed to confirm the formation of PLA‐PEG. X‐ray diffraction was used to understand the molecular level dispersion of AZT within the polymeric matrices, while differential scanning calorimetry was employed to assess thermal properties. Scanning electron microscopy was employed to understand the surface morphology of AZT‐loaded microparticles. In vitro release experiments performed in pH 7.4 buffer media extended the release of AZT up to 125 h with PLGA, whereas 30 h were required for releasing AZT through PLA‐PEG microparticles. Cumulative release data were fitted to an empirical equation to understand the nature of release characteristics. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci 000: 000–000, 2011     

Preparation and in vitro characterization of poly(sebacic acid‐co‐ricinoleic acid)‐based tamoxifen citrate‐loaded microparticles for breast cancer

This study was aimed to develop an injectable polymeric drug delivery system for tamoxifen citrate (TC) using poly(sebacic acid‐co‐ricinoleic acid) [poly(SA‐RA) 70 : 30 w/w] as a drug carrier for the treatment of estrogen receptor positive breast cancer. Injectable biodegradable microparticles of TC were produced by solvent displacement technique of microencapsulation and were characterized by surface morphology (scanning electron microscopy), particle size, size distribution, physical and chemical interaction (Fourier transform infrared), nature and physical state of drug [DSC and X‐ray diffraction (XRD)], and in vitro release studies. TC loading over different concentrations was analyzed by high performance liquid chromatography (HPLC) technique. Polyanhydride microparticles obtained after lyophilization were nearly spherical in shape with smooth surface and size less than 2.5 μm. TC was dispersed in the form of amorphous state, and TC remains intact and stable during the process of microencapsulation. In vitro drug release studies demonstrated prolonged controlled release of TC with zero‐order kinetics. Stability studies revealed that the production process of microparticles itself did not affect the chemical stability of the drug and polymer forming the particle matrix. Significant difference in drug release capacity was observed in microparticles with different drug loadings, and the drug release was more sustained in microparticles prepared with high TC. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A multiple emulsion method for loading 5‐fluorouracil into a magnetite‐loaded nanocapsule: a physicochemical investigation

The preparation of 5‐fluorouracil (5‐FU) loaded poly(lactic‐co‐glycolic acid) (PLGA) biodegradable nanocapsules containing magnetite nanoparticles was studied through the modified multiple emulsion solvent evaporation method for magnetically controlled delivery of anticancer drugs. The morphology and size distribution of the prepared magnetite/PLGA nanocapsules were investigated by transmission and scanning electron microscopy. The micrographs showed that the magnetic nanocapsules were almost spherical in shape and their mean diameter was in the nanometer range with a narrow size distribution. Fourier transform infrared and ultraviolet–visible spectroscopy confirmed incorporation of 5‐FU molecules into the PLGA matrix. The magnetite content was assessed by thermogravimetric and magnetometry analysis and the results showed a magnetite content of 35 wt% with high magnetic responsivity. Magnetometry measurements showed superparamagnetic properties of the magnetic nanocapsules with a saturation magnetization of 13.7 emu g^?1. Such biodegradable magnetic nanocapsules could be considered as an appropriate choice for drug targeting. Furthermore, the influence of some important processing parameters such as PLGA concentration, initial loading of 5‐FU and poly(vinyl alcohol) concentration on drug content, encapsulation efficiency and in vitro drug release kinetics was investigated and optimized. The drug content and encapsulation efficiency of the magnetic nanocapsules were 4–7 wt% and 60%–80%, respectively, and the nanocapsules demonstrated controlled release of 5‐FU at 37 °C in a buffer solution. All samples exhibited a burst release at the initial stage and this burst release showed its close dependence on the formulation parameters. Copyright © 2012 Society of Chemical Industry     

Preparation and release characteristics of dexamethasone acetate loaded organochlorine‐free poly(lactide‐co‐glycolide) nanoparticles

Dexamethasone‐loaded poly(lactide‐co‐glycolide) (PLGA) devices are commonly used as model systems for controlled release. In this study, PLGA nanoparticles containing dexamethasone acetate were prepared by a nanoprecipitation technique in the absence of organochlorine solvents and were characterized by their mean size, ζ potential, scanning electron microscopy, and differential scanning calorimetry to develop a controlled release system. The analytical method for the quantification of dexamethasone acetate by high‐performance liquid chromatography was validated. The results show that it was possible to prepare particles at a nanometric size because the average diameter of the drug‐loaded PLGA particles was 540 ± 4 nm with a polydispersity index of 0.07 ± 0.01 and a ζ potential of ?2.5 ± 0.3 mV. These values remained stable for at least 7 months. The drug encapsulation efficiency was 48%. In vitro tests showed that about 25% of the drug was released in 48 h. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41199.     

The effect of process variables on the morphology and release characteristics of protein‐loaded PLGA particles

Poly(lactide‐co‐glycolide) (PLGA 75 : 25), IV 0.94 dL/g was chosen as the matrix of the microparticles. Bovine serum albumin (BSA) (Fraction V) as the model drug was incorporated in the microparticles by a W/O/W emulsification and solvent evaporation technique. The effect of the various preparation parameters on particle morphology, drug loading efficiency, and drug release profiles of the resultant microparticles were examined. Particle size varied from 5 to 60 μm. The final morphology of the microparticles varied dramatically with preparation variables such as equipment used to produce the primary emulsion (W1/O) and the water‐to‐oil ratio (W1/O) in the primary emulsion. In general, the viscosity of the primary emulsion had a significant effect on the porosity of particles produced. The release of BSA showed a strong relationship with the preparation parameters of microparticles, partly due to the morphological effects. For example, microparticles made from the vortex mixer that was used to disperse inner aqueous phase (W1) to oil phase (O) showed a lower burst effect than that made from the homogenizer because of its better surface morphology. W1/O ratio, speed of dispersing the primary emulsion into W2, PLGA concentration, and different matrix materials also affected the drug release profiles. In all the samples studied here, only diffusion‐controlled release was observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3053–3061, 2006     

Intrinsic factor and vitamin B12 complex‐loaded poly[lactic‐co‐(glycolic acid)] microspheres: preparation,characterization and drug release

BACKGROUND: Vitamin B12 is an essential vitamin required by all mammals. Absorption of vitamin B12 is facilitated by binding of intrinsic factor–vitamin B₁₂ complex to specific receptors in the ileum. In humans a deficiency of this vitamin or a lack of intrinsic factor leads to pernicious anaemia. The major objective of the present study was to prepare intrinsic factor–vitamin B12 complex‐loaded poly[lactic‐co‐(glycolic acid)] (PLGA)‐based microparticles and to investigate their release kinetics. RESULTS: PLGA copolymer was synthesized by the ring‐opening polymerization method and characterized using gel permeation chromatography, Fourier transform infrared spectroscopy and ¹H NMR. The glass transition temperature measurement showed a single T_g at 40 °C. The intrinsic factor–vitamin B12 complex‐loaded PLGA microspheres were prepared by a water‐in‐oil‐in‐water double emulsion solvent extraction/evaporation technique. An environmental scanning electron microscopy investigation demonstrated that the PLGA particles had a mean particle diameter of 38 µm. Interestingly, different drug release patterns (bi‐ and triphasic ones) were observed for vitamin B12‐loaded and intrinsic factor–vitamin B12 complex‐loaded microspheres. In contrast to the rapid release of vitamin B12 by itself, in vitro release tests showed that intrinsic factor and vitamin B12 in the complex were released from PLGA microspheres in a sustained manner over 15 days. CONCLUSION: PLGA microspheres can be an effective carrier for the intrinsic factor–vitamin B12 complex. Copyright © 2007 Society of Chemical Industry     

Preparation and characterization of lovastatin polymeric microparticles by coacervation‐phase separation method for dissolution enhancement

Dissolution rate of lovastatin is slow, only 30% of the oral dose is absorbed, and it undergoes extensive first‐pass extraction resulting in low and variable bioavailability. The objective of this research was to enhance the dissolution rate through preparing polymeric microparticles. Coacervation‐phase separation method through the addition of a non‐solvent was used to prepare polymeric microparticles. The method was optimized through studying effects of the type of solvent, the type of polymer, drug : polymer ratio and concentration of surfactant on particle size, particle size distribution, and in‐vitro drug release. Optimized polymeric microparticles and unprocessed drug were characterized using different techniques (SEM, FTIR, DSC, and PXRD) and their flow properties were evaluated. The optimum microparticles were prepared using ethanol as a solvent, Eudragit^® L 100 as a polymer in a drug:polymer ratio of 1:2 and SDS in a concentration of 0.25%. Characterization techniques indicated a change from the crystalline form to an amorphous form that was molecularly dispersed into the polymer. Flow properties of these microparticles were improved as compared to unprocessed drug. Drug release was enhanced 4‐ to 5‐folds probably due to precipitation of the drug in an amorphous form; wetting enhancement; size reduction and stabilization by polymers and surfactants. In conclusion the selection of proper process parameters enhanced drug release 5 folds. The use of DMSO as a solvent and the preparation of physical mixtures in this research provided a means for controlled or prolonged release. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43277.     

Preparation and characterization of pH‐sensitive microparticles based on polyelectrolyte complexes for antibiotic delivery

pH‐sensitive microparticles formed by combination of a synthetic copolymer and sodium alginate in presence of calcium chloride were prepared in mild conditions for specific water‐soluble drug delivery. The copolymers of acryloxyethyl‐trimethylammonium chloride and N‐vinyl‐2‐pyrrolidone were synthesized by radical polymerization in aqueous solution at 60°C using sodium persulfate as initiator. Fourier transform infrared spectroscopic characterization confirmed the structure of the copolymers and their compositions were determined by potentiometric method. Scanning Electron Microscopy study revealed that microparticles have a rough morphology with size ranging from 450 to 800 µm as measured by optical microcopy. Cefotaxime as a model drug was encapsulated in the microparticles to evaluate the in vitro release behavior under different pH conditions. At physiological temperature, the amount of drug released increased with increasing pH. The amount of drug release from microparticles after 24 h (84%) was more extensive in simulated intestinal fluid when compared with acidic pH environment (20%). These preliminary results suggest that the new microparticles can be used as good candidate for oral drug controlled release in the treatment to colon diseases. POLYM. ENG. SCI., 55:981–987, 2015. © 2014 Society of Plastics Engineers     

Preparation and drug release behaviors of 5‐fluorouracil loaded poly(glycolide‐co‐lactide‐co‐caprolactone) nanoparticles

5‐Fluorouracil (5‐Fu) loaded poly(glycolide‐co‐lactide‐co‐caprolactone) (PGLC) nanoparticles were prepared by modified spontaneous emulsification solvent diffusion method (modified‐SESD method) and characterized by dynamic light scattering, scanning electron microscopy and ¹H NMR determination. It was found that the obtained nanoparticles showed near spherical shape and was controllable with the radius range of 30–100 nm. Compared with the nanoparticles prepared by polylactide and poly (lactide‐co‐glycolide) (PLGA) under the similar preparation condition, yield of PGLC nanoparticles was the highest, which reached to about 100%. On the other hand, drug entrapment efficiency of PGLC nanoparticles was also higher than that of PLGA and PLLA nanoparticles. 5‐Fu release behavior of PGLC nanoparticles in vitro showed that 5‐Fu release of PGLC nanoparticles showed a near zero‐order release profile, and 5‐Fu release rate of PGLC nanoparticles was faster than that of PLLA and PLGA nanoparticles. According to degradation behavior of PGLC nanoparticles, it could be proposed that the kinetic of degradation controlled release played an important role in the release process of PGLC nanoparticles. It revealed that the PGLC nanoparticles could be a promising drug carrier. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Controlled delivery of growth‐hormone‐releasing peptide 6 from the poly(lactic‐co‐glycolic acid)–poly(ethylene glycol)–poly(lactic‐co‐glycolic acid) copolymer and the effect of a growth‐hormone‐releasing peptide 6–copolymer hydrogel on the growth of rex rabbits

Growth‐hormone‐releasing peptide 6 (GHRP‐6) plays an important role in animal growth. However, there have been few studies focusing on the effect of GHRP‐6 on animal growth through controlled release systems. We synthesized the poly(lactic‐co‐glycolic acid) (PLGA)–poly(ethylene glycol) (PEG)–PLGA copolymer to investigate its controlled released effect on GHRP‐6 in vitro and to study the effect of a GHRP‐6–copolymer hydrogel on the growth of rex rabbits. The copolymer was synthesized with ring‐opening copolymerization and characterized by ¹H‐NMR. The interaction between GHRP‐6 and the copolymer was characterized by Fourier transform infrared spectroscopy and X‐ray diffraction. The body weight, serum level of insulin‐like growth factor 1 (IGF‐1), and hair coat quality were studied in rex rabbits. The results show that hydrogen bonds formed between the N? H group in GHRP‐6 and the C?O group in the copolymer. The release mechanism of GHRP‐6 was a combination of a diffusion‐controlled mechanism and an erosion‐controlled mechanism in the copolymer. The serum level of IGF‐1, hair coat quality, and body weight were all significantly higher in the GHRP‐6–copolymer hydrogel group than in the other groups. These results indicate that the copolymer effectively controlled the release of GHRP‐6. In addition, the GHRP‐6–copolymer hydrogel increased the synthesis of IGF‐1 for a prolonged period and, thereby, increased the rex rabbits' growth and hair coat quality. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40185.     

Effects of polymer degradation on drug release from PLGA‐mPEG microparticles: A dynamic study of microparticle morphological and physicochemical properties

In vitro degradation and drug release of poly (DL ‐lactide‐co‐glycolic acid)‐methoxypoly(ethyleneglycol) (PLGA‐mPEG) microparticles were performed through a dynamic monitoring process, to investigate the effect of degradation on drug release from microparticles and to elucidate the dominant factor that governed the drug release kinetics. Methotrexate (MTX), an antirheumatic drug, was employed as the model drug. Drug release showed a triphasic pattern: an initial burst release followed by a lag period and subsequently a second burst release. The initial burst release was mainly caused by dissolution and diffusion of drugs at/near the surface of microparticles. During the following lag period, microparticles suffered little morphological changes, whereas the physicochemical changes of the polymer contributed to the increasing mobility of drug molecules, and then provided transport pathways for drug release. Later on, the erosion of the polymer matrix became significant. Morphology study showed that the trend of porosity change was in accordance with last phase release profile, indicating that porosity played an extremely important role in controlling drug release. The liberation pattern of mPEG was elucidated. The more pores formed, the more mPEG chains were exposed to the aqueous medium and disengaged from the polymer. Scanning electron micrography observation further confirmed these conclusions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The polymer free volume as a controlling factor for drug release from poly(lactide‐co‐glycolide) microspheres

Drug release from poly(lactide‐co‐glycolide) (PLGA) microspheres is strongly determined by the pore structure of the particles. This study examines how swelling‐induced pore constriction delays the drug release and by which factors this process is controlled. Combination of different porosimetric and pycnometric methods enabled insight into the submicroscopic range of the pore structure and revealed that remarkably the polymer free volume plays a crucial role in drug release from PLGA microspheres. Surprisingly, the latter was shown to be inversely correlated to the degree of diffusional drug release. This can be explained by a swelling‐induced constriction of the macroporous channel system in the microspheres which is related to the availability of free volume. The hole free volume was shown to be well controllable by the manufacturing conditions. Thus, the study deepens comprehension of the mechanism of drug release from biodegradable microparticles and offers an effective approach for controlling the release behavior. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39740.     

Development and evaluation of a novel dosage form of diltiazem HCl using ethylene vinyl acetate copolymer and sodium starch glycolate (in vitro/in vivo study)

The work aims at developing a CR formulation, with high encapsulation efficiency of diltiazem HCl, suitable for twice daily administration. Microparticles, using EVA copolymer, were prepared by coacervation‐phase separation technique, subjected to controlled extraction and vacuum freeze drying processes to generate and immobilize a non uniform initial drug concentration distribution, and evaluated in vitro and in animals. Effects of increasing initial drug concentration, varying polymer system, increasing porosity, and decreasing tortuosity, varying the size of the microparticles and the pH of the dissolution medium on the release rate were evaluated. The results indicated that the release rate from microparticles was constant (zero‐order) for an appreciable period of time but it was low for twice‐daily administration. It increased with increasing initial drug concentration, varying polymer system, increasing porosity, and decreasing tortuosity, and decreasing the size of the microparticles but the duration of constant release was shorter except for formulations containing 2.00 and 2.25% sodium starch glycolate. 10‐h duration of constant release was achieved and the zero‐order release rate was within the required rate to achieve the desired therapeutic level. The pH of the dissolution medium did not have any effect on the release rate. The results of the in vivo study indicated that in vitro dissolution correlated well with in vivo AUC_0‐10 and that there were no statistically significant differences in AUC_0‐10 and C_max between the new CR formulation and Cardizem® CD. Accordingly, a new CR formulation that delivers diltiazem HCl at a constant rate, suitable for twice daily administration was developed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Amine‐modified poly(vinyl alcohol) as a novel surfactant to modulate size and surface charge of poly(lactide‐co‐glycolide) nanoparticles

Poly(lactide‐co‐glycolide) (PLGA) nanoparticles (NPs) represent a promising tool for effective delivery of biomacromolecules, thanks to their biodegradability and biocompatibility properties. PLGA NPs are often synthesized by the emulsion‐solvent evaporation method and poly(vinyl alcohol) (PVA) represents one of the most commonly used surfactants. Although PVA‐mediated synthesis of PLGA NPs is effective in tailoring NP size and stability, the resulting negative surface charge can prevent both endosomal escape and biomacromolecule release in cell cytosol. To overcome this limit, a novel amino‐modified PVA (amino‐PVA) surfactant with a cationic charge was synthesized and its potential for the formulation of PLGA NPs was investigated. In either single (oil‐in‐water) or double (water‐in‐oil‐in‐water) emulsion synthesis, different mixtures of PVA and amino‐PVA were studied, by monitoring their effects on NP size and surface charge. Optimized properties were obtained with a combination of 0.975% (w/v) of PVA with 0.025% (w/v) of amino‐PVA. This formulation was further investigated for degradation properties and cytocompatibility. High stability and low cytotoxicity make the system promising for the encapsulation and release of hydrophilic drugs and biomacromolecules. © 2016 Society of Chemical Industry     

Electrohydrodynamic liquid atomization of biodegradable polymer microparticles: Effect of electrohydrodynamic liquid atomization variables on microparticles

The exploration of a method to tailor a biodegradable polymer into microparticles/nanoparticles with a desirable morphology and size may result in their enhanced performance as biomedical devices for drug delivery and simplify the preparation process. A modified electrohydrodynamic liquid atomization (EHDA) process is reported here for the preparation of poly(lactic‐co‐glycolic acid) (PLGA) microparticles. To understand systematically the EHDA method for the preparation of PLGA microparticles, PLGAs of four different molecular weights were electrosprayed under different conditions involving changes in the applied potential, liquid flow rate, polymer concentration, and solvent. The results show that the right concentration range of PLGA is key for electrospraying the spherical particles. A solution with a low‐molecular‐weight PLGA has a wider concentration range for electrospraying into spherical particles than a solution with a high‐molecular‐weight PLGA. At the concentration at which spherical particles are formed, the diameter of the as‐sprayed particles is not affected substantially by the applied potential and PLGA molecular weight, but it increases monotonically with the liquid flow rate and PLGA concentration. Experimentation further demonstrated that low electric conductivity, a low dielectric constant, and a high vapor pressure of chloroform are favorable for controlling the EHDA process to obtain quasi‐monodisperse particles. The addition of the solvent N,N‐dimethylformamide with opposite solvent properties extremely disturbs the stability of the EHDA process and, at the same time, produces smaller and polydisperse particles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Gastro‐resistant controlled release of OTC encapsulated in alginate/chitosan matrix coated with acryl‐EZE® MP in fluidized bed

A gastro‐resistant system of acryl‐EZE® MP coated alginate/chitosan microparticles was developed to improve the controlled release of oxytetracycline (OTC). Microparticles were obtained by complex coacervation and, thereafter, were coated using fluidized polymer dispersion with acryl‐EZE® MP solution. OTC distribution inside the microparticles was determined by multiphoton confocal microscopy, demonstrating the efficiency of encapsulation process. In vitro OTC release kinetic was performed in order to obtain the release profile in gastric and intestinal simulated fluids. A fast initial release, or burst effect, was observed with uncoated microparticles loaded with OTC in gastric conditions. When a 50% mass increase in acryl‐EZE® MP coating was achieved, OTC release in acidic medium was greatly reduced, resulting in the expected gastro‐resistant effect. Different mathematical models were applied to describe the drug diffusion across the polymer matrix. The Logistic model was the best tool to interpret the experimental data in most of the systems studied. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40444.     

Tamoxifen‐loaded microspheres based on mixtures of poly(D,L‐lactide‐co‐glycolide) and poly(D,L‐lactide) polymers: Effect of polymeric composition on drug release and in vitro antitumoral activity

Mixtures of different bioerosionable polyesters were used to prepare microparticulated tamoxifen delivery systems to achieve anticancer effects in breast malignant cancer cells. Tamoxifen (TMX) was included into microspheres (MS) formulated via spray‐drying. Mixtures of poly(D ,L ‐lactide‐co‐glycolide) (PLGA) of different lactide/glycolide proportions (50 : 50 and 75 : 25) and poly(D ,L ‐lactic acid) (PLA) were used. The average diameter of the resultant TMX‐loaded microparticles was in the range 1.04 ± 0.51–1.55 ± 0.95 μm. The encapsulation efficiency of TMX was between 97.8% [48.9 ± 0.1 TMX (μg)/MS (mg)] and 69.6% [36.6 ± 0.1 TMX (μg)/MS (mg)] depending on the polymeric composition of the formulation. Drug burst effect was not observed. TMX was released from the polymeric matrices in a sustained release manner between 11 and 58 days depending on polymeric composition of microspheres. TMX‐loaded microspheres showed high efficacy in causing cell death in MCF7 breast malignant cancer cells. Thus, these TMX‐loaded PLGA‐based microspheres hold potential to treat breast malignant cancer cells. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and characterization of miglitol-loaded Poly (d,l-lactide-co-glycolide) microparticles using high pressure homogenization-solvent evaporation method

Sustained release Miglitol-loaded poly (d, l-lactide-co-glycolide) (PLGA) microparticles were prepared using high pressure homogenization-solvent evaporation method. 2³ full factorial design was employed to study effect of independent variables (X₁-Polymer amount; X₂-Surfactant concentration and X₃-Homogenization Pressure) on percent encapsulation efficiency (%EE) as response. The microparticles produced were characterized for particle size, morphology, % EE, drug polymer compatibility and in vitro drug release. An average particle size of Miglitol-loaded PLGA microparticles was 230.1?nm and found almost spherical with smooth surface. % EE ranged from 58.7%?±?2.11 to 86.5%?±?0.24 depending on the polymer amount, surfactant concentration and homogenization pressure. An absence of chemical interaction between drug-polymer and reduction in % crystallinity of drug was confirmed by FTIR and X-ray diffraction analysis respectively. In vitro release studies showed a sustained release of Miglitol from microparticles up to 12?hrs.     

Microparticles based on hydrophobically modified chitosan as drug carriers

In this work, a hydrophobically modified (HM) chitosan derivative was prepared by covalent linkage of C₁₂ groups to the chitosan backbone. HM‐chitosan microparticles were prepared according to an emulsification‐solvent evaporation method and naltrexone (NTX) was used as a model drug. For comparison, unmodified chitosan and poly lactic‐co‐glycolic acid (PLGA) microparticles were also tested as carriers for NTX. HM‐chitosan formed viscous semi‐dilute solutions, suggesting a high level of chain entanglements and hydrophobic associations. HM‐chitosan microparticles generally showed higher production yield and encapsulation efficiency, as compared with chitosan and PLGA. The burst release shown by chitosan microparticles was significantly reduced when using the HM‐chitosan derivative. An enhanced control of drug release was observed over at least 50 days. PLGA particles demonstrated inferior controlled release properties as compared to HM‐chitosan subsequent to the initial release stage. These results revealed the potential of hydrophobic modification of chitosan as a means to improve the stability and sustained delivery properties of the polymer. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40055.     

Production of double‐walled nanoparticles containing meloxicam

Double‐walled nanospheres, containing meloxicam, were fabricated with poly‐(D,L ‐lactide‐co‐glycolide) (PLGA) and poly(L ‐lactide) (PLLA) using the solvent evaporation technique. This article discusses the effect of formulation variables [sonication power, sonication time, concentration of poly(vinyl alcohol), organic/aqueous volume ratio in the first emulsion] on the production of double‐walled nanospheres. The involved phase separation of these two polymers was investigated using differential scanning calorimetry. Double‐walled microspheres containing meloxicam were also produced to determine the composition of the shell and core polymer, based on different solubilities of polymers in ethyl acetate, and to examine the inner morphology and drug distribution using optical and fluorescence microscopy. The produced microparticles have shown a double‐walled structure with meloxicam solubilized in the PLGA‐rich phase. Therefore, adjusting the selected formulation variables and using a mass ratio of 1:1 PLLA/PLGA, double‐walled nanospheres where meloxicam is dispersed within the core can be produced. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers