The development of a dense gas solvent exchange process for the impregnation of pharmaceuticals into porous chitosan

Preparation and in vitro release kinetics of nitrendipine-loaded PLLA-PEG-PLLA microparticles by supercritical solution impregnation process

In this work, drug-loaded polymer microparticles were prepared by a supercritical solution impregnation (SSI) process with nitrendipine as the model drug and PLLA-PEG-PLLA as the drug carrier. The morphology, size, distribution and functional groups of the drug-loaded microparticles were characterized by scanning electron microscopy (SEM), laser particle size analyzer and fourier transform infrared analysis (FTIR). The effects of pressure, temperature and cosolvent concentration on the drug loading and release property of the microparticles prepared with and without cosolvent were investigated. The in vitro drug release kinetics of drug-loaded microparticles was studied with five models. The results indicated that the morphology of the drug-loaded polymer microparticles was not influenced by the SSI process. And the addition of ethanol cosolvent could significantly improve the drug loading of the microparticles. The most satisfied drug loading and the release properties of the microparticles were achieved under 55 °C, 13 MPa and cosolvent ethanol concentration of 3%. The drug could be released for more than 140 h. The analysis of the drug release kinetics showed that the experimental data fitted with Ritger-Peppas model were optimal. According to the release exponent value, the in vitro release process of the nitrendipine-loaded microparticles was controlled by Fickian diffusion, which can provides a theoretical basis for drug release of this type of experiment.

Improving the dissolution rate of hydrophobic drugs through encapsulation in porous lactose as a new biocompatible porous carrier

T he dissolution rates of indomethacin (IMC) and nifedipine (NIF) as poorly water-soluble model drugs have been significantly improved by encapsulating their molecules in the porous structure of engineered-particles of lactose as a new biocompatible porous carrier. The formulation method used in this study utilized a template-based spray-drying technique for in-situ production of porous lactose followed by two solvent-based drug-loading methods: (i) adsorption from organic solution, and (ii) incipient wetness impregnation to incorporate the drugs inside the porous lactose. In both cases, the results of DSC and XRD have revealed the deposition of nano-sized crystals of drugs inside the nanopores due to the nanoconfinement phenomenon. Greater extents of drug loadings have been achieved during the indomethacin adsorption due to the hydrogen-bonding interaction with the surface of lactose, as determined by FTIR spectroscopy. The in vitro release studies in simulated gastric fluid (SGF) have shown faster release rates for the impregnated particles compared with drug-loaded particles via the adsorption method.

Nano-formulations of drugs: Recent developments, impact and challenges

Nano-formulations of medicinal drugs have attracted the interest of many researchers for drug delivery applications. These nano-formulations enhance the properties of conventional drugs and are specific to the targeted delivery site. Dendrimers, polymeric nanoparticles, liposomes, nano-emulsions and micelles are some of the nano-formulations that are gaining prominence in pharmaceutical industry for enhanced drug formulation. Wide varieties of synthesis methods are available for the preparation of nano-formulations to deliver drugs in biological system. The choice of synthesis methods depend on the size and shape of particulate formulation, biochemical properties of drug, and the targeted site. This article discusses recent developments in nano-formulation and the progressive impact on pharmaceutical research and industries. Additionally, process challenges relating to consistent generation of nano-formulations for drug delivery are discussed.

Incorporation of acetaminophen as an active pharmaceutical ingredient into porous lactose

A new formulation method for solid dosage forms with drug loadings from 0.65 ± 0.03% to 39 ± 1% (w/w) of acetaminophen (APAP) as a model drug has been presented. The proposed method involves the production of highly-porous lactose with a BET surface area of 20 ± 1 m(2)/g as an excipient using a templating method and the incorporation of drug into the porous structure by adsorption from a solution of the drug in ethanol. Drug deposition inside the carrier particles, rather than being physically distributed between them, eliminated the potential drug/carrier segregation, which resulted in excellent blend uniformities with relative standard deviations of less than 3.5% for all drug formulations. The results of DSC and XRD tests have shown deposition of nanocrystals of APAP inside the nanopores of lactose due the nanoconfinement phenomenon. FTIR spectroscopy has revealed no interaction between the adsorbed drug and the surface of lactose. The final loaded lactose particles had large BET surface areas and high porosities, which significantly increased the crushing strengths of the produced tablets. In vitro release studies in phosphate buffer (pH 5.8) have shown an acceptable delivery performance of 85% APAP release within 7 minutes for loaded powders filled in gelatin capsules.

Ordered nanoporous silica as carriers for improved delivery of water insoluble drugs: a comparative study between three dimensional and two dimensional macroporous silica

The goal of the present study was to compare the drug release properties and stability of the nanoporous silica with different pore architectures as a matrix for improved delivery of poorly soluble drugs. For this purpose, three dimensional ordered macroporous (3DOM) silica with 3D continuous and interconnected macropores of different sizes (200 nm and 500 nm) and classic mesoporous silica (ie, Mobil Composition of Matter [MCM]-41 and Santa Barbara Amorphous [SBA]-15) with well-ordered two dimensional (2D) cylindrical mesopores were successfully fabricated and then loaded with the model drug indomethacin (IMC) via the solvent deposition method. Scanning electron microscopy (SEM), N₂ adsorption, differential scanning calorimetry (DSC), and X-ray diffraction (XRD) were applied to systematically characterize all IMC-loaded nanoporous silica formulations, evidencing the successful inclusion of IMC into nanopores, the reduced crystallinity, and finally accelerated dissolution of IMC. It was worth mentioning that, in comparison to 2D mesoporous silica, 3DOM silica displayed a more rapid release profile, which may be ascribed to the 3D interconnected pore networks and the highly accessible surface areas. The results obtained from the stability test indicated that the amorphous state of IMC entrapped in the 2D mesoporous silica (SBA-15 and MCM-41) has a better physical stability than in that of 3DOM silica. Moreover, the dissolution rate and stability of IMC loaded in 3DOM silica was closely related to the pore size of macroporous silica. The colorimetric 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Cell Counting Kit (CCK)-8 assays in combination with direct morphology observations demonstrated the good biocompatibility of nanoporous silica, especially for 3DOM silica and SBA-15. The present work encourages further study of the drug release properties and stability of drug entrapped in different pore architecture of silica in order to realize their potential in oral drug delivery.

An overview of the analytical characterization of nanostructured drug delivery systems: towards green and sustainable pharmaceuticals: a review

The analytical characterization of drug delivery systems prepared by means of green manufacturing technologies using CO(2) as a processing fluid is here reviewed. The assessment of the performance of nanopharmaceuticals designed for controlled drug release may result in a complex analytical issue and multidisciplinary studies focused on the evaluation of physicochemical, morphological and textural properties of the products may be required. The determination of the drug content as well as the detection of impurities and solvent residues are often carried out by chromatography. Assays on solid state samples relying on X-ray, vibrational and nuclear magnetic resonance spectroscopies are of great interests to study the composition and structure of pharmaceutical forms. The morphology and size of particles are commonly checked by microscopy and complementary chemical information can be extracted in combination with spectroscopic accessories. Regarding the thermal behavior, calorimetric and thermogravimetric techniques are applied to assess the thermal transitions and stability of the samples. The evaluation of drug release profiles from the nanopharmaceuticals can be based on various experimental set-ups depending on the administration route to be considered. Kinetic curves showing the evolution of the drug concentration as a function of time in various physiological conditions (e.g., gastric, plasmatic or topical) are recorded commonly by UV-vis spectroscopy and/or chromatography. Representative examples are commented in detail to illustrate the characterization strategies.

Incorporation of indomethacin nanoparticles into 3-D ordered macroporous silica for enhanced dissolution and reduced gastric irritancy

In the present study, we exploited for the first time the potential of 3-D ordered macroporous (3DOM) silica as matrix for drug nanoparticles, in order to obtain proper control over drug particle size in the sub-micrometer range, enhance the dissolution rate, and reduce gastric damage. 3DOM silica matrix with 3-D spherical pores of 200 nm was successfully created and then loaded with IMC nanoparticles at various drug-silica ratios. A rapid release profile for IMC nanoparticle formulations was achieved in comparison with microsized IMC and a commercial capsule, which could be attributed to both increase in the specific surface area and decrease in the crystallinity of IMC, as well as the hydrophilic surface and the interconnected pore networks of 3DOM silica. Reduced gastric damage of IMC was demonstrated, and the protective effect may arise from the reduction in drug particle size as well as encapsulation effect of 3DOM silica.

Enhancing cell penetration and proliferation in chitosan hydrogels for tissue engineering applications

The aim of this study was to develop a process to create highly porous three-dimensional (3D) chitosan hydrogels suitable for tissue engineering applications. Chitosan was crosslinked by glutaraldehyde (0.5 vol %) under high pressure CO(2) at 60 bar and 4 °C for a period of 90 min. A gradient-depressurisation strategy was developed, which was efficient in increasing pore size and the overall porosity of resultant hydrogels. The average pore diameter increased two fold (59 μm) compared with the sample that was depressurised after complete crosslinking and hydrogel formation (32 μm). It was feasible to achieve a pore diameter of 140 μm and the porosity of hydrogels to 87% by addition of Acacia gum (AG) as a surfactant to the media. The enhancement in porosity resulted in an increased swelling ratio and decreased mechanical strength. On hydrogels with large pores (>90 μm) and high porosities (>85%), fibroblasts were able to penetrate up to 400 μm into the hydrogels with reasonable viabilities (~80%) upon static seeding. MTS assays showed that fibroblasts proliferated over 14 days. Furthermore, aligned microchannels were produced within porous hydrogels to further promote cell proliferation. The developed process can be easily used to generate homogenous pores of controlled sizes in 3D chitosan hydrogels and may be of use for a broad range of tissue engineering applications.

Fabrication of porous chitosan scaffolds for soft tissue engineering using dense gas CO2

The aim of this study was to investigate the feasibility of fabricating porous crosslinked chitosan hydrogels in an aqueous phase using dense gas CO(2) as a foaming agent. Highly porous chitosan hydrogels were formed by using glutaraldehyde and genipin as crosslinkers. The method developed here eliminates the formation of a skin layer, and does not require the use of surfactants or other toxic reagents to generate porosity. The chitosan hydrogel scaffolds had an average pore diameter of 30-40 μm. The operating pressure had a negligible effect on the pore characteristics of chitosan hydrogels. Temperature, reaction period, type of biopolymer and crosslinker had a significant impact on the pore size and characteristics of the hydrogel produced by dense gas CO(2). Scanning electron microscopy and histological analysis confirmed that the resulting porous structures allowed fibroblasts seeded on these scaffolds to proliferate into the three-dimensional (3-D) structure of these chitosan hydrogels. Live/dead staining and MTS analysis demonstrated that fibroblast cells proliferated over 7 days. The fabricated hydrogels exhibited comparable mechanical strength and swelling ratio and are potentially useful for soft tissue engineering applications such as skin and cartilage regeneration.

A review on composite liposomal technologies for specialized drug delivery

The combination of liposomes with polymeric scaffolds could revolutionize the current state of drug delivery technology. Although liposomes have been extensively studied as a promising drug delivery model for bioactive compounds, there still remain major drawbacks for widespread pharmaceutical application. Two approaches for overcoming the factors related to the suboptimal efficacy of liposomes in drug delivery have been suggested. The first entails modifying the liposome surface with functional moieties, while the second involves integration of pre-encapsulated drug-loaded liposomes within depot polymeric scaffolds. This attempts to provide ingenious solutions to the limitations of conventional liposomes such as short plasma half-lives, toxicity, stability, and poor control of drug release over prolonged periods. This review delineates the key advances in composite technologies that merge the concepts of depot polymeric scaffolds with liposome technology to overcome the limitations of conventional liposomes for pharmaceutical applications.