Compensate for or Minimize Matrix Effects? Strategies for Overcoming Matrix Effects in Liquid Chromatography-Mass Spectrometry Technique: A Tutorial Review.

In recent decades, mass spectrometry techniques, particularly when combined with separation methods such as high-performance liquid chromatography, have become increasingly important in pharmaceutical, bio-analytical, environmental, and food science applications because they afford high selectivity and sensitivity. However, mass spectrometry has limitations due to the matrix effects (ME), which can be particularly marked in complex mixes, when the analyte co-elutes together with other molecules, altering analysis results quantitatively. This may be detrimental during method validation, negatively affecting reproducibility, linearity, selectivity, accuracy, and sensitivity. Starting from literature and own experience, this review intends to provide a simple guideline for selecting the best operative conditions to overcome matrix effects in LC-MS techniques, to obtain the best result in the shortest time. The proposed methodology can be of benefit in different sectors, such as pharmaceutical, bio-analytical, environmental, and food sciences. Depending on the required sensitivity, analysts may minimize or compensate for ME. When sensitivity is crucial, analysis must try to minimize ME by adjusting MS parameters, chromatographic conditions, or optimizing clean-up. On the contrary, to compensate for ME analysts should have recourse to calibration approaches depending on the availability of blank matrix. When blank matrices are available, calibration can occur through isotope labeled internal standards and matrix matched calibration standards; conversely, when blank matrices are not available, calibration can be performed through isotope labeled internal standards, background subtraction, or surrogate matrices. In any case, an adjusting of MS parameters, chromatographic conditions, or a clean-up are necessary.

Thermosensitive hybrid hyaluronan/p(HPMAm-lac)-PEG hydrogels enhance cartilage regeneration in a mouse model of osteoarthritis.

Osteoarthritis (OA), due to cartilage degeneration, is one of the leading causes of disability worldwide. Currently, there are not efficacious therapies to reverse cartilage degeneration. In this study we evaluated the potential of hybrid hydrogels, composed of a biodegradable and thermosensitive triblock copolymer cross-linked via Michael addition to thiolated hyaluronic acid, in contrasting inflammatory processes underlying OA. Hydrogels composed of different w/w % concentrations of hyaluronan were investigated for their degradation behavior and capacity to release the polysaccharide in a sustained fashion. It was found that hyaluronic acid was controllably released during network degradation with a zero-order release kinetics, and the release rate depended on cross-link density and degradation kinetics of the hydrogels. When locally administered in vivo in an OA mouse model, the hydrogels demonstrated the ability to restore, to some extent, bone remineralization, proteoglycan production, levels of Sox-9 and Runx-2. Furthermore, the downregulation of proinflammatory mediators, such as TNF-α, NFkB, and RANKL and proinflammatory cytokines was observed. In summary, the investigated hydrogel technology represents an ideal candidate for the potential encapsulation and release of drugs relevant in the field of OA. In this context, the hydrogel matrix could act in synergy with the drug, in reversing phenomena of inflammation, cartilage disruption, and bone demineralization associated with OA.

Effect of Grinding on the Solid-State Stability and Particle Dissolution of Acyclovir Polymorphs.

The present work investigated the solid state change of 4 acyclovir polymorphs when ground at room temperature (Method A) and under cryo-grinding in the presence of liquid nitrogen (Method B). Modifications in particle size and shape (evaluated by scanning electron microscopy) and in the water content (evaluated by thermal analysis) were related to transitions at the solid state, as confirmed by X-ray powder diffractometry. Anhydrous Form I was stable under grinding by both Methods A and B. The anhydrous Form II was stable during grinding under Method A, whereas it was progressively converted to the hydrate Form V during grinding under Method B. The hydrate Form V was stable under Method A, whereas it was converted to the anhydrous Form I after 15 min and then to the hydrate Form VI after 45 min of grinding. The hydrate Form VI proved to be stable under grinding by both Methods A and B. Thus, Form I and VI were the only forms that yielded a sizeable decrease in particle size under grinding, with a consequent increase in particle dissolution rate, while maintaining solid state physicochemical stability. Form I treated under Method B grinding gave the best dissolution rate.

Nano-medicine Improving the Bioavailability of Small Molecules for the Prevention of Neurodegenerative Diseases.

Neurodegenerative diseases, including Parkinson's and Alzheimer's, are a heterogeneous group of brain disorders characterized by the progressive degeneration of the structure and function of the central or peripheral nervous system. It is thought that the number of people affected by these pathologies will increase in future decades, particularly in the more economically developed countries, where the populations are experiencing a demographic shift towards older ages. For many of these pathologies, and in particular for Alzheimer's disease, no effective treatments are available, and the consequent economic and social costs are very high. Scientific progress in recent decades has provided a better understanding of the genetic and biological mechanisms responsible for these neurodegenerative diseases, and offers the hope for new therapeutic approaches in the near future. Meanwhile, the lack of effective therapies for these diseases has caused researchers to focus attention on the powerful opportunity of prevention, seen on the one hand as a series of healthcare measures and patient behaviors, and on the other hand as treatments exploiting several molecules or compounds with the potential to slow down the appearance of the first signs of pathology or even to prevent these diseases. Among these, curcumin, flavonoids, such as quercetin, Gingko biloba, and folic acid have attracted the attention of scientists, and ways are being explored to increase their effectiveness and bioavailability in the site of action. Most molecules suffer from problems of solubility, or bioavailability, or the ability to cross the blood brain barrier, and one solution to this limitation being explored is nanomedicine. Polymeric nanoparticles, as well as liposomes, and functionalized nanosystems may overcome several bioavailability limits of active molecules and increase their effectiveness in the brain. This review offers an overview of small molecules that may prove effective in preventing neurodegenerative diseases, and describes the strategies in nanomedicine that are being studied to improve their bioavailability.

Formation, Physicochemical Characterization, and Thermodynamic Stability of the Amorphous State of Drugs and Excipients.

Drugs and excipients used for pharmaceutical applications generally exist in the solid (crystalline or amorphous) state, more rarely as liquid materials. In some cases, according to the physicochemical nature of the molecule, or as a consequence of specific technological processes, a compound may exist exclusively in the amorphous state. In other cases, as a consequence of specific treatments (freezing and spray drying, melting and co-melting, grinding and compression), the crystalline form may convert into a completely or partially amorphous form. An amorphous material shows physical and thermodynamic properties different from the corresponding crystalline form, with profound repercussions on its technological performance and biopharmaceutical properties. Several physicochemical techniques such as X-ray powder diffraction, thermal methods of analysis, spectroscopic techniques, gravimetric techniques, and inverse gas chromatography can be applied to characterize the amorphous form of a compound (drug or excipient), and to evaluate its thermodynamic stability. This review offers a survey of the technologies used to convert a crystalline solid into an amorphous form, and describes the most important techniques for characterizing the amorphous state of compounds of pharmaceutical interest.