Supercritical solvent impregnation of ophthalmic drugs on chitosan derivatives

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.

Supercritical fluid-mediated methods to encapsulate drugs: recent advances and new opportunities

With the advent of the development of novel pharmaceutical products and therapies, there is a need for effective delivery of these products to patients. Dependent on whether they are small-molecular weight drugs or biologics, many new compounds may suffer from poor solubility, poor stability or require frequent administration and therefore require optimized delivery. For example, the utilization of polymorphism and the enhanced solubility in the amorphous state is being exploited to improve the dissolution of small-molecular weight poorly soluble drugs. This can be achieved by the formation of solid dispersions in water-soluble matrices. In addition, encapsulation in biodegradable polymeric materials is one potential route to reduce the frequency of administration through the formation of sustained-release formulations. This is desirable for biologics, for example, which generally require administration once or twice daily. Supercritical fluid processing can achieve both of these outcomes, and this review focuses on the use of supercritical CO2 to encapsulate active pharmaceutical ingredients to enhance solubility or achieve sustained release. Using supercritical CO2-mediated processes provides a clean and potentially solvent-free route to prepare novel drug products and is therefore an attractive alternative to conventional manufacturing technologies.

Chemical technologies for exploiting and recycling carbon dioxide into the value chain

While experts in various fields discuss the potential of carbon capture and storage (CCS) technologies, the utilization of carbon dioxide as chemical feedstock is also attracting renewed and rapidly growing interest. These approaches do not compete; rather, they are complementary: CCS aims to capture and store huge quantities of carbon dioxide, while the chemical exploitation of carbon dioxide aims to generate value and develop better and more-efficient processes from a limited part of the waste stream. Provided that the overall carbon footprint for the carbon dioxide-based process chain is competitive with conventional chemical production and that the reaction with the carbon dioxide molecule is enabled by the use of appropriate catalysts, carbon dioxide can be a promising carbon source with practically unlimited availability for a range of industrially relevant products. In addition, it can be used as a versatile processing fluid based on its remarkable physicochemical properties.

Supercritical fluid-assisted preparation of imprinted contact lenses for drug delivery

The aim of this work was to develop an innovative supercritical fluid (SCF)-assisted molecular imprinting method to endow commercial soft contact lenses (SCLs) with the ability to load specific drugs and to control their release. This approach seeks to overcome the limitation of the common loading of preformed SCLs by immersion in concentrated drug solutions (only valid for highly water soluble drugs) and of the molecular imprinting methods that require choice of the drug before polymerization and thus to create drug-tailored networks. In particular, we focused on improving the flurbiprofen load/release capacity of daily wear Hilafilcon B commercial SCLs by the use of sequential SCF flurbiprofen impregnation and extraction steps. Supercritical carbon dioxide (scCO2) impregnation assays were performed at 12.0 MPa and 40 °C, while scCO2 extractions were performed at 20.0 MPa and 40 °C. Conventional flurbiprofen sorption and drug removal experiments in aqueous solutions were carried out for comparison purposes. SCF-processed SCLs showed a recognition ability and a higher affinity for flurbiprofen in aqueous solution than for the structurally related ibuprofen and dexamethasone, which suggests the creation of molecularly imprinted cavities driven by both physical (swelling/plasticization) and chemical (carbonyl groups in the network with the C-F group in the drug) interactions. Processing with scCO2 did not alter some of the critical functional properties of SCLs (glass transition temperature, transmittance, oxygen permeability, contact angle), enabled the control of drug loaded/released amounts (by the application of several consecutive processing cycles) and permitted the preparation of hydrophobic drug-based therapeutic SCLs in much shorter process times than those using conventional aqueous-based molecular imprinting methods.