Bigels as drug delivery systems: From their components to their applications.

Bigels are systems that usually result from mixing a hydrogel and an organogel: the aqueous phase is commonly formed by a hydrophilic biopolymer, whereas the organic phase comprises a gelled vegetable oil because of the presence of an organogelator. The proportion of the corresponding gelling agent in each phase, the organogel/hydrogel ratio, and the mixing temperature and speed all need to be taken into consideration for bigel manufacturing. Bigels, which are particularly useful drug delivery systems, have already been formulated for transdermal, buccal, and vaginal routes. Mechanical assessments and microscopy are the most reported characterization techniques. As we review here, their composition and unique structure confer promising drug delivery attributes, such as mucoadhesion, the ability to control drug release, and the possibility of including both hydrophilic and lipophilic drugs in the same system.

Biodegradable Microspheres as Intravitreal Delivery Systems for Prolonged Drug Release. What is their Eminence in the Nanoparticle Era?

Drug administration to the posterior segment of the eye has many challenges due to the natural barriers and consequent problems of low and unpredictable bioavailability. There is an increasing need for managing severe posterior eye diseases, such as age-related macular degeneration, diabetic retinopathy, etc. Most of these diseases, if left untreated, lead to blindness. Traditional ocular formulations and topical administrations are almost inefficient and the drug delivery to the back of the eye requires direct administrations through intravitreal injections of innovative drug delivery systems. These systems must be easily injectable, able to release the drug for a prolonged period of time (to overcome the problem of repeated administrations) and made of biodegradable/biocompatible polymers. Among these delivery systems, microspheres still have an important role. This overview wants to highlight the use of microspheres as intravitreal systems to overcome the challenges of back of the eye diseases. Studies have shown that microspheres are able to enhance the intravitreal half-life and thus bioavailability of many drugs, protecting them from degradation. Furthermore, personalized therapies can be made by changing the amount of administered microspheres. This review focuses on the materials (polymers) used for the preparation of the microparticulate systems and comparative remarks are made with respect to the use of nanoparticles.

Sponge-Like Dressings Based on the Association of Chitosan and Sericin for the Treatment of Chronic Skin Ulcers. II. Loading of the Hemoderivative Platelet Lysate.

Platelet lysate (PL) was loaded into dressings based on chitosan glutamate (CSG) low and high molecular weight, sericin (Ser), and glycine (Gly). A synergic effect of Ser and PL on fibroblast proliferation was proved in vitro. Two different PL loading approaches were considered: the first provided to prepare dressings by freeze-drying a mixture of PL and CSG/Gly/Ser solution, the second approach consisted in the extemporarily loading of PL in the CSG/Gly/Ser freeze-dried dressings. As for the first approach, PL loading did not produce any variation in dressing mechanical properties. Such dressings absorbed a high amount (about 8-fold of dry weight) of phosphate-buffered saline (fluid mimicking wound exudate), forming a gel with pseudoplastic and elastic properties. Platelet-derived growth factor AB assay indicated that neither freeze-drying nor the excipients alter PL growth factor content. As for the second approach, mechanical and rheological properties of the gel formed upon PL absorption enabled to choose a PL loading of about 90 µL/cm(2). Upon contact with fibroblasts, all PL loaded formulations increased the number not only of viable cells but also of those in the proliferative phase. Histological studies effected on human skin strips pointed out the positive effect of PL loaded dressings on dermal matrix reconstruction.

Skin Localization of Lipid Nanoparticles (SLN/NLC): Focusing the Influence of Formulation Parameters.

BACKGROUND: In this study, fluorescein labeled SLN and NLC formulations were prepared for improving the dermal distribution of the hydrophilic active ingredients and for enhancing the skin penetration. METHODS: To determine skin distribution of the lipid nanoparticles ex-vivo penetration/ permeation experiments were performed using full thickness rat skin by means of Franz diffusion cells. Studies on the localization of fluorescence labeled nanoparticles were performed by confocal laser scanning microscopy (CLSM). Cellular uptake studies were performed on human keratinocyte cell line (HaCaT) and visualized by fluorescence microscope. Both tissue and cell uptake were also quantitatively determined by means of fluorimetric method in the skin extract or cell extract. RESULTS: Both imaging and quantification studies suggest that the dermal localization of the lipid nanoparticles depends on their dimensions and particle size distribution. The CLSM images clearly show that the Tripalmitin based lipid nanoparticles have higher accumulation in the skin. It is possible to overcome the stratum corneum barrier function with T-NLC05 coded lipid nanoparticle formulation. Additionally cellular uptake of this NLC formulation is time dependent. Conclusion: It can be concluded that this formulation is promising for treating local skin disorders without systemic side effects. On the other hand obtained results suggest that optimum formulation (T-NLC05) might be an interesting option even for novel cosmetic products.

Characteristics of hydroxypropyl methylcellulose influencing compactibility and prediction of particle and tablet properties by infrared spectroscopy.

Particle characteristics, chemical substitution, compaction behavior, and tablet properties of hydroxypropyl methylcellulose powders from two different suppliers were related using multivariate data analysis. By Principal Component Analysis it was shown that the the degree of substitution of the HPMC powders did not correlate to the particle and compaction properties as strongly as anticipated. Particle shape and powder surface area seem to be more important for the compaction behaviour of the powders than the degree of substitution. In addition, particle and tablet properties were predicted from infrared spectral data. Fourier transform infrared (FTIR) and near infrared (NIR) spectral data of the powders were combined with measured values of the particle characteristics, compaction behavior, and tablet properties using the multivariate data analysis program SIMCA 7.1. Properties like density, particle shape, tablet tensile strength, and drug release characteristics of the HPMC powders and corresponding tablets in this study could be predicted using Partial Least Squares models. In conclusion, the particle shape and powder surface area of HPMC powders seem to be important factors for the quality of tablet attained. Further, this study confirms that NIR and FTIR analysis used in combination with multivariate analysis are powerful tools for predicting the properties of materials and the quality of the end product.