Bojan Čalija

An investigation of formulation factors affecting feasibility of alginate-chitosan microparticles for oral delivery of naproxen

In the present work we investigated the feasibility of chitosan treated Ca-alginate microparticles for delivery of naproxen in lower parts of GIT and evaluated influence of formulation factors on their physicochemical characteristics and drug release profiles. Investigated factors were drug/polymer ratio, chitosan molecular weight, chitosan concentration in hardening medium, and hardening time. Sixteen microparticle formulations were prepared utilizing 24 full factorial design (each factor was varied at two levels). Microparticles size varied between 262.3 ± 14.9 and 358.4 ± 21.7 μm with slightly deformed spherical shape. Low naproxen solubility and rapid reaction of ionotropic gelation resulted in high encapsulation efficiency (> 75.19%). Under conditions mimicking those in the stomach, after two hours, less than 6.18% of naproxen was released. Significant influence of all investigated factors on drug release rate was observed in simulated small intestinal fluid. Furthermore, experimental design analysis revealed that chitosan molecular weight and its concentration had the most pronounced effect on naproxen release. Release data kinetics indicated predominant influence of a pH-dependent relaxation mechanism on drug release from microparticles.

Inorganically modified diatomite as a potential prolonged-release drug carrier

Inorganic modification of diatomite was performed with the precipitation product of partially neutralized aluminum sulfate solution at three different mass ratios. The starting and the modified diatomites were characterized by SEM-EDS, FTIR, thermal analysis and zeta potential measurements and evaluated for drug loading capacity in adsorption batch experiments using diclofenac sodium (DS) as a model drug. In vitro drug release studies were performed in phosphate buffer pH6.8 from comprimates containing: the drug adsorbed onto the selected modified diatomite sample (DAMD), physical mixture of the drug with the selected modified diatomite sample (PMDMD) and physical mixture of the drug with the starting diatomite (PMDD). In vivo acute toxicity testing of the modified diatomite samples was performed on mice. High adsorbent loading of the selected modified diatomite sample (~250mg/g in 2h) enabled the preparation of comprimates containing adsorbed DS in the amount near to its therapeutic dose. Drug release studies demonstrated prolonged release of DS over a period of 8h from both DAMD comprimates (18% after 8h) and PMDMD comprimates (45% after 8h). The release kinetics for DAMD and PMDMD comprimates fitted well with Korsmeyer-Peppas and Bhaskar models, indicating that the release mechanism was a combination of non-Fickian diffusion and ion exchange process.

Modified local diatomite as potential functional drug carrier--A model study for diclofenac sodium.

Diatomite makes a promising candidate for a drug carrier because of its high porosity, large surface area, modifiable surface chemistry and biocompatibility. Herein, refined diatomite from Kolubara coal basin, which complied with the pharmacopoeial requirements for heavy metals content and microbiological quality, was used as a starting material. Inorganic modification of the starting material was performed through a simple, one-step procedure. Significant increase in adsorbent loading with diclofenac sodium (DS) was achieved after the modification process (∼373mg/g) which enabled the preparation of comprimates containing therapeutic dose of the adsorbed drug. Adsorption of DS onto modified diatomite resulted in the alteration of the drugs XRD pattern and FTIR spectrum. In vitro drug release studies in phosphate buffer pH 7.5 demonstrated prolonged DS release over 8h from comprimates containing DS adsorbed on modified diatomite (up to 37% after 8h) and those containing physical mixture of the same composition (up to 45% after 8h). The results of in vivo toxicity testing on mice pointed on potential safety of both unmodified (starting) and modified diatomite. All these findings favor the application of diatomite as a potential functional drug carrier.

Chitosan oligosaccharide as prospective cross-linking agent for naproxen-loaded Ca-alginate microparticles with improved pH sensitivity

Objectives: The aim of the presented work was to develop Ca-alginate microparticles for oral administration of naproxen reinforced with chitosan oligosaccharide (COS) with a special interest to examine the potential of COS for improvement of microparticles stability in simulated intestinal fluid (SIF). Method: Microparticles were prepared according to the two-step procedure using an air-jet device with varying calcium chloride and COS concentration in the gelling medium. All prepared microparticles were subjected to size determination, morphology, surface, and inner structure analysis by scanning electron microscopy (SEM), drug loading (DL) and encapsulation efficiency (EE), differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy, in vitro swelling, and drug release studies. Results: In general, COS-treated microparticles were spherical in shape but somewhat deformed, exhibiting the surface roughness with the mean particle size less than 350 µm. FT-IR and DSC studies confirmed the formation of polyelectrolyte complex (PEC) between alginate and COS, whereas chemical properties and crystalline state of naproxen were unaffected by the encapsulation process. Low naproxen solubility in the gelling medium and rapid entrapment resulted in high encapsulation efficiency (>80.0%). The results of swelling studies demonstrated that COS-treated particles were less sensitive to swelling and erosion in SIF in comparison to the nontreated particles. This resulted in prolonged drug release in SIF, which was dependent on the COS/alginate ratio. Conclusion: The obtained findings proved that COS could be used as an effective cross-linking agent for improvement of Ca-alginate microparticles stability in SIF, allowing prolonged release of the encapsulated drug after oral administration.

Effects of different carrier materials on physicochemical properties of microencapsulated grape skin extract

AbstractThe goal of this study was to investigate the characteristics of grape skin extract (GSE) spray dried with different carriers: maltodextrin (MD), gum Arabic (GA) and skim milk powder (SMP). The grape skin extract was obtained from winery by-product of red grape variety Prokupac (Vitis vinifera L.). The morphology of the powders, their thermal, chemical and physical properties (water activity, bulk and tapped densities, solubility), as well as release studies in different pH conditions were analyzed. Total anthocyanin content and total phenolic content were determined by spectrophotometric methods. MD and GA-based microparticles were non-porous and spherical, while SMP-based ones were irregularly shaped. The process of spray drying Prokupac GSE using these three carriers produced powders with low water activity (0.24–0.28), good powder characteristics, high yields, and solubility higher than 90%. The obtained dissolution/release profiles indicated prolonged release of anthocyanins and phenolic compounds in different mediums, especially from GSE/GA microparticles. These results have shown that grape skin as the main by-product of wine production could be used as a source of natural colorants and bioactive compounds, and microencapsulation as a promising technique for the protection of these compounds, their stabilization in longer periods and prolonged release.

Development of semisolid self-microemulsifying drug delivery systems (SMEDDSs) filled in hard capsules for oral delivery of aciclovir

The study aimed to develop semisolid self-microemulsifying drug delivery systems (SMEDDSs) as carriers for oral delivery of aciclovir in hard hydroxypropylmethyl cellulose (HPMC) capsules. Six self-dispersing systems (SD1-SD6) were prepared by loading aciclovir into the semisolid formulations consisting of medium chain length triglycerides (lipid), macrogolglycerol hydroxystearate (surfactant), polyglyceryl-3-dioleate (cosurfactant), glycerol (hydrophilic cosolvent), and macrogol 8000 (viscosity modifier). Their characterization was performed in order to identify the semisolid system with rheological behaviour suitable for filling in hard HPMC capsules and fast dispersibility in acidic and alkaline aqueous media with formation of oil-in-water microemulsions. The optimal SMEDDS was loaded with aciclovir at two levels (2% and 33.33%) and morphology and aqueous dispersibility of the obtained systems were examined by applying light microscopy and photon correlation spectroscopy (PCS), respectively. The assessment of diffusivity of aciclovir from the SMEDDSs by using an enhancer cell model, showed that it was increased at a higher drug loading. Differential scanning calorimetry (DSC) analysis indicated that the SMEDDSs were semisolids at temperatures up to 50°C and physically stable and compatible with HPMC capsules for 3 months storage at 25°C and 4°C. The results of in vitro release study revealed that the designed solid dosage form based on the semisolid SMEDDS loaded with the therapeutic dose of 200mg, may control partitioning of the solubilized drug from in situ formed oil-in-water microemulsion carrier into the sorrounding aqueous media, and hence decrease the risk for precipitation of the drug.

Application of miscibility analysis and determination of Soluplus solubility map for development of carvedilol-loaded nanofibers

Electrospinning was used to produce carvedilol-loaded Soluplus polymer nanofibers using a systematic approach. Miscibility between drug and polymer was determined through calculation of the interaction parameter, χ, and the difference between the total solubility parameters, Δdt. A solubility map for Soluplus was obtained by examining different solvent systems, carrying out electrospinning, and characterizing the nanofibers formed. Miscibility studies showed that carvedilol and Soluplus can form a miscible system (χ=-2.3054; Δδt<7.0MPa1/2). Based on the Soluplus solubility map, acetone: chloroform (90:10; w/w) represents a suitable solvent system for electrospinning of carvedilol-loaded Soluplus nanofibers. Scanning electron microscopy of these nanofiber samples showed smooth surface morphology. The nanofibers had a regular cylindrical morphology. Beads appeared along the nanofibers more frequently in formulations with lower percentages of carvedilol. Differential scanning calorimetry showed no melting endothermic peak for carvedilol, which suggests its complete conversion from the crystalline to the amorphous form (at polymer: carvedilol 1:1). The infrared spectrum of the carvedilol-loaded Soluplus nanofibers showed no characteristic carvedilol peak at 3344.5cm-1, which suggests interactions between carvedilol and Soluplus. Dissolution studies of these nanofibers showed improved pure carvedilol dissolution properties, with >85% of the carvedilol released in the first 15min, versus 20% for pure carvedilol. The use of miscibility analysis and polymer solubility studies demonstrate great technological potential to tackle the challenge for inadequate dissolution of poorly water-soluble drugs.

Microencapsulation of anthocyanin-rich black soybean coat extract by spray drying using maltodextrin, gum Arabic and skimmed milk powder

Abstract Black soybean coat is insufficiently valorised food production waste rich in anthocyanins. The goal of the study was to examine physicochemical properties of spray dried extract of black soybean coat in regard to carrier materials: maltodextrin, gum Arabic, and skimmed milk powder. Maltodextrin and gum Arabic-based microparticles were spherical and non-porous while skimmed milk powder-based were irregularly shaped. Low water activity of microparticles (0.31–0.33), good powders characteristics, high solubility (80.3–94.3%) and encapsulation yields (63.7–77.0%) were determined. All microparticles exhibited significant antioxidant capacity (243–386 μmolTE/g), good colour stability after three months of storage and antimicrobial activity. High content of total anthocyanins, with cyanidin-3-glucoside as predominant, were achieved. In vitro release of anthocyanins from microparticles was sustained, particularly from gum Arabic-based. These findings suggest that proposed simple eco-friendly extraction and microencapsulation procedures could serve as valuable tools for valorisation and conversion of black soybean coat into highly functional and stable food colourant.

Potentiation of the ibuprofen antihyperalgesic effect using inorganically functionalized diatomite

Refined diatomite from the Kolubara coal basin (Serbia) was inorganically functionalized through a simple, one-pot, non-time-consuming procedure. Model drug ibuprofen was adsorbed on the functionalized diatomite under optimized conditions providing high drug loading (∼201 mg g-1). Physicochemical characterization was performed on the starting and modified diatomite before and after ibuprofen adsorption. Dissolution testing was conducted on comprimates containing the drug adsorbed on the modified diatomite (composite) and those containing a physical mixture of the drug with the modified diatomite. The antihyperalgesic and the antiedematous activity of ibuprofen from both composites and physical mixtures were evaluated in vivo employing an inflammatory pain model in rats. Functionalization and subsequent drug adsorption had no significant effect on the diatomite ordered porous structure. Two forms of ibuprofen most likely coexisted in the adsorbed state - the acidic form and a salt/complex with aluminium. Both comprimate types showed extended ibuprofen release in vitro, but no significant influence on the duration of the ibuprofen effect was observed upon in vivo application of the composite or physical mixture. However, both the composite and the physical mixture were more effective than equivalent doses of ibuprofen in pain suppression in rats. This potentiation of the ibuprofen antihyperalgesic effect may result from the formation of the drug complex with the carrier and can be of clinical relevance.

Polymeric Microparticles and Inorganic Micro/Nanoparticulate Drug Carriers: An Overview and Pharmaceutical Application

Abstract Recent expansion of innovative micro- and nanosized drug carriers has been driven by utilization of materials with improved functional properties, along with employment of innovative preparation techniques. Various materials of both natural and synthetic origin, with diverse physicochemical properties, ranging from polymers to structured porous inorganic materials have been investigated as starting materials for preparation of these carriers. This chapter focuses on characteristics, methods of preparation/functionalization of micro- and nanosized carriers consisting of these two distinct groups of materials. In addition, their potential application in up-to-date drug delivery is discussed.